Ocean warming since 1982 has expanded the niche of toxic algal blooms in the North Atlantic and North Pacific oceans

Combined Effects of Temperature and Toxic Algal Abundance on Paralytic Shellfish Toxic Accumulation, Tissue Distribution and Elimination Dynamics in Mussels Mytilus coruscus

This study assessed the impact of increasing seawater surface temperature (SST) and toxic algal abundance (TAA) on the accumulation, tissue distribution and elimination dynamics of paralytic shellfish toxins (PSTs) in mussels. Mytilus coruscus were fed with the PSTs-producing dinoflagellate A. catenella under four simulated environment conditions. The maximum PSTs concentration was determined to be 3548 µg STX eq.kg⁻¹, which was four times higher than the EU regulatory limit. The increasing SST caused a significant decline in PSTs levels in mussels with rapid elimination rates, whereas high TAA increased the PSTs concentration. As a result, the PSTs toxicity levels decreased under the combined condition. Additionally, toxin burdens were assessed within shellfish tissues, with the highest levels quantified in the hepatopancreas. It is noteworthy that the toxin burden shifted towards the mantle from gill, muscle and gonad at the 17th day. Moreover, variability of PSTs was measured, and was associated with changes in each environmental factor. Hence, this study primarily illustrates the combined effects of SST and TAA on PSTs toxicity, showing that increasing environmental temperature is of benefit to lower PSTs toxicity with rapid elimination rates.

Portable, stable, and sensitive assay to detect phosphate in water with gold nanoparticles (AuNPs) and dextran tablet

A novel and highly sensitive tablet-based colorimetric sensor is developed for the detection of phosphate (Pi) in drinking and surface water using mercaptoacetic acid-capped gold nanoparticles (MA-AuNPs). Characterization of AuNPs and MA-AuNPs was achieved by ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and Dynamic light scattering (DLS). The principle of this sensor is based on the aggregation and disaggregation mechanisms of AuNPs that result in a color change from blue to red due to the surface plasmon resonance effect, where europium ions (Eu³⁺) act as the aggregating agent. Herein, dextran is used to encapsulate the Eu³⁺ ions into a tablet format to make the detection system user friendly. Hence, the sensor only requires dissolving a Eu³⁺-dextran tablet into the water sample and subsequently adding MA-AuNPs for the colorimetric quantification of phosphate. This assay is very sensitive with a calculated detection limit of 0.3 μg L^-1 and an upper detection limit of 26 μg L^-1, while 10 μg L^-1 is the allowable limit of Pi in drinking water. A comparative study with a conventional Hach kit confirmed the accuracy of our sensor. Also, real water samples from river, lake, and tap sources were tested to examine the sensor's applicability towards commercialization. The assay did not interfere with common ions in water, thus being Pi-specific, and the performance of the assay was stable for up to at least three weeks. Overall, our new approach provides a simple, stable, rapid, low-cost and promising device for Pi detection in water.

A global child health perspective on climate change, migration and human rights

Current indicators of anthropogenic climate change are foreboding and demand immediate collaborative action and policy change to reduce carbon emissions rapidly. Human and environmental effects of climate change are already widespread. Large-scale disruptive disasters and weather-related events have downstream and cascading effects on livelihoods, national economies, population health and global human rights. These effects create human displacement and migration crises with far-reaching implications for children. Displacement and migration, both within and across national borders, have sequelae for the physical and mental health of children. Young children are vulnerable-both physiologically and developmentally immature-and dependent on others for safety and resources. They also are least responsible for the climate crisis. Child health threats stemming from displacement and migration exemplify questions of social and intergenerational injustice inherent in the climate crisis. Pediatric health care providers are increasingly called upon to care for children and ensure access to care for children who have experienced displacement from climate change, even as dire predictions for the future are escalating climate adaptation efforts. Pediatric health care providers have a role in these efforts-to identify and advocate for those children most at risk from climate change and to bolster clinical care and education strategies to prevent harm to our patients and children. This paper provides a global perspective on climate change for pediatric providers, including how climate change reflects and reinforces colonial legacies that harm child health. We provide action steps for those providers who care for children who have been displaced in the U.S. and who advocate for children's health globally.

A pediatrician's guide to climate change-informed primary care

Despite the urgency of the climate crisis and mounting evidence linking climate change to child health harms, pediatricians do not routinely engage with climate change in the office. Each primary care visit offers opportunities to screen for and support children burdened with risks to health that are increasingly intense due to climate change. Routine promotion of healthy behaviors also aligns with some needed-and powerful-solutions to the climate crisis. For some patients, including those engaged in athletics, those with asthma and allergies, or those with complex healthcare needs, preparedness for environmental risks and disasters worsened by climate change is a critical component of disease prevention and management. For all patients, anticipatory guidance topics that are already mainstays of pediatric best practices are related closely to needed guidance to keep children safe and promote health in the setting of compounding risks due to climate change. By considering climate change in routine care, pediatricians will be updating practice to align with evidence-based literature and better serving patients. This article provides a framework for pediatricians to provide climate-informed primary care during the structure of pediatric well child and other visits.

Environmental DNA Metabarcoding for Simultaneous Monitoring and Ecological Assessment of Many Harmful Algae

Harmful algae can have profound economic, environmental, and social consequences. As the timing, frequency, and severity of harmful algal blooms (HABs) change alongside global climate, efficient tools to monitor and understand the current ecological context of these taxa are increasingly important. Here we employ environmental DNA metabarcoding to identify patterns in a wide variety of potentially harmful algae and associated ecological communities in the Hood Canal of Puget Sound in Washington State, USA. Tracking trends of occurrence in a series of water samples over a period of 19 months, we find algal sequences from genera with harmful members in a majority of samples, suggesting that these groups are routinely present in local waters. We report patterns in variants of the economically important genus Pseudo-nitzschia (of which some members produce domoic acid; family Bacillariaceae), as well as multiple potentially harmful algal taxa previously unknown or poorly documented in the region, including a cold-water variant from the genus Alexandrium (of which some members produce saxitoxin; family Gonyaulacaceae), two variants from the genus Karlodinium (of which some members produce karlotoxins; family Kareniaceae), and one variant from the parasitic genus Hematodinium (family Syndiniaceae). We then use data on environmental variables and the biological community surrounding each algal taxon to illustrate the ecological context in which they are commonly found. Environmental DNA metabarcoding thus simultaneously (1) alerts us to potential new or cryptic occurrences of algae from harmful genera, (2) expands our knowledge of the co-occurring conditions and species associated with the growth of these organisms in changing marine environments, and (3) suggests a pathway for multispecies monitoring and management moving forward.

Initiation of efficient C4 pathway in response to low ambient CO2 during the bloom period of a marine dinoflagellate

Dinoflagellates are important primary producers and major causative agents of harmful algal blooms in the global ocean. Despite the great ecological significance, the photosynthetic carbon acquisition by dinoflagellates is still poorly understood. The pathways of photosynthetic carbon assimilation in a marine dinoflagellate Prorocentrum donghaiense under both in situ and laboratory-simulated bloom conditions were investigated using a combination of metaproteomics, qPCR, stable carbon isotope and targeted metabolomics approaches. A rapid consumption of dissolved CO₂ to generate high biomass was observed as the bloom proceeded. The carbon assimilation genes and proteins including intracellular carbonic anhydrase 2, phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase and RubisCO as well as their enzyme activities were all highly expressed at the low CO₂ level, indicating that C₄ photosynthetic pathway functioned in the blooming P. donghaiense cells. Furthermore, δ¹³ C values and content of C₄ compound (malate) significantly increased with the decreasing CO₂ concentration. The transition from C₃ to C₄ pathway minimizes the internal CO₂ leakage and guarantees efficient carbon fixation at the low CO₂ level. This study demonstrates the existence of C₄ photosynthetic pathway in a marine dinoflagellate and reveals its important complementary role to assist carbon assimilation for cell proliferation during the bloom period.

Efficient integration of plasmonic Ag/AgCl with perovskite-type LaFeO3: Enhanced visible-light photocatalytic activity for removal of harmful algae

A novel plasmonic Ag/AgCl@LaFeO₃ (ALFO) photocatalyst was successfully synthesized by a simple in-situ synthesis method with enhanced photocatalytic activity under visible light for harmful algal blooms (HABs) control. The structure, morphology, chemical states, optical and electrochemical properties of the photocatalyst were systematically investigated using a series of characterization methods. Compared with pure LaFeO₃ and Ag/AgCl, ALFO-20% owned a higher light absorption capacity and lower electron-hole recombined rate. Therefore, ALFO-20% had higher photocatalytic activity with a near 100% removal rate of chlorophyll a within 150 min, whose kinetic constant was 15.36 and 9.61 times faster than those of LaFeO₃ and Ag/AgCl. In addition, the changes of zeta potential, cell membrane permeability, cell morphology, organic matter, total soluble protein, photosynthetic system and antioxidant enzyme system in Microcystis aeruginosa (M. aeruginosa) were studied to explore the mechanism of M. aeruginosa photocatalytic inactivation. The results showed that ALFO-20% could change the permeability and morphology of the algae cell membrane, as well as destroy the photosynthesis system and antioxidant system of M. aeruginosa. What's more, ALFO could further degrade the organic matters flowed out after algae rupture and die, reducing the secondary pollution and avoiding the recurrence of HABs. Finally, the species of reactive oxygen species (ROS) (mainly •O₂^- and •OH) produced by ALFO were determined through quenching experiments, and a possible photocatalytic mechanism was proposed. Overall, ALFO can efficiently remove the harmful algae under the visible light, providing a promising method for controlling HABs.

Mitigation of harmful algal blooms caused by Alexandrium catenella and reduction in saxitoxin accumulation in bivalves using cultivable seaweeds

Alexandrium catenella is a harmful algal bloom (HAB)-forming dinoflagellate that causes significant damage to the cultivation and harvest of shellfish due to its synthesis of paralytic shellfish toxins.  To evaluate the potential for macroalgae aquaculture to mitigate A. catenella blooms, we determined the effects of three cultivable macroalgae - Saccharina latissima (sugar kelp), Chondrus crispus (Irish moss), and Ulva spp. - on A. catenella in culture- and field-based experiments.  Co-culture growth assays of A. catenella exposed to environmentally realistic concentrations of each macroalgae showed that all species except low levels of C. crispus caused cell lysis and significant reductions in A. catenella densities relative to control treatments of 17-74% in 2-3 days and 42-96% in ~one week (p<0.05 for all assays). In a toxin accumulation experiment, S. latissima significantly lessened (p<0.05) saxitoxin (STX) accumulation in blue mussels (Mytilus edulis), keeping levels (71.80±1.98 µg STX 100 g^-1) below US closure limits (80 µg STX 100 g^-1) compared to the untreated control (93.47±8.11 µg STX 100 g^-1). Bottle incubations of field-collected, bloom populations of A. catenella experienced significant reductions in cell densities of up to 95% when exposed to aquaculture concentrations of all three macroalgae (p<0.005 for all). The stocking of aquacultured S. latissima within mesocosms containing a bloom population of A. catenella (initial density: 3.2 × 10⁴ cells L^-1) reduced the population of A. catenella by 73% over 48 h (p<0.005) while Ulva addition caused a 54% reduction in A. catenella over 96 h (p<0.01).  Among the three seaweeds, their ordered ability to inhibit A. catenella was S. latissima > Ulva spp. > C. crispus. Seaweeds' primary anti-A. catenella activity were allelopathic, while nutrient competition, pH elevation, and macroalgae-attached bacteria may have played a contributory role in some experiments. Collectively, these results suggest that the integration of macroalgae with shellfish-centric aquaculture establishments should be considered as a non-invasive, environmentally friendly, and potentially profit-generating measure to mitigate A. catenella-caused damage to the shellfish aquaculture industry.

An Autonomous Platform for Near Real-Time Surveillance of Harmful Algae and Their Toxins in Dynamic Coastal Shelf Environments

Efforts to identify in situ the mechanisms underpinning the response of harmful algae to climate change demand frequent observations in dynamic and often difficult to access marine and freshwater environments. Increasingly, resource managers and researchers are looking to fill this data gap using unmanned systems. In this study we integrated the Environmental Sample Processor (ESP) into an autonomous platform to provide near real-time surveillance of harmful algae and the toxin domoic acid on the Washington State continental shelf over a three-year period (2016–2018). The ESP mooring design accommodated the necessary subsystems to sustain ESP operations, supporting deployment durations of up to 7.5 weeks. The combination of ESP observations and a suite of contextual measurements from the ESP mooring and a nearby surface buoy permitted an investigation into toxic Pseudo-nitzschia spp. bloom dynamics. Preliminary findings suggest a connection between bloom formation and nutrient availability that is modulated by wind-forced coastal-trapped waves. In addition, high concentrations of Pseudo-nitzschia spp. and elevated levels of domoic acid observed at the ESP mooring location were not necessarily associated with the advection of water from known bloom initiation sites. Such insights, made possible by this autonomous technology, enable the formulation of testable hypotheses on climate-driven changes in HAB dynamics that can be investigated during future deployments.

Effects of the Marine Biotoxins Okadaic Acid and Dinophysistoxins on Fish

Natural high proliferations of toxin-producing microorganisms in marine and freshwater environments result in dreadful consequences at the socioeconomically and environmental level due to water and seafood contamination. Monitoring programs and scientific evidence point to harmful algal blooms (HABs) increasing in frequency and intensity as a result of global climate alterations. Among marine toxins, the okadaic acid (OA) and the related dinophysistoxins (DTX) are the most frequently reported in EU waters, mainly in shellfish species. These toxins are responsible for human syndrome diarrhetic shellfish poisoning (DSP). Fish, like other marine species, are also exposed to HABs and their toxins. However, reduced attention has been given to exposure, accumulation, and effects on fish of DSP toxins, such as OA. The present review intends to summarize the current knowledge of the impact of DSP toxins and to identify the main issues needing further research. From data reviewed in this work, it is clear that exposure of fish to DSP toxins causes a range of negative effects, from behavioral and morphological alterations to death. However, there is still much to be investigated about the ecological and food safety risks related to contamination of fish with DSP toxins.

Climate Change and the Practice of Medicine: Essentials for Resident Education

Despite calls for including content on climate change and its effect on health in curricula across the spectrum of medical education, no widely used resource exists to guide residency training programs in this effort. This lack of resources poses challenges for training program leaders seeking to incorporate evidence-based climate and health content into their curricula. Climate change increases risks of heat-related illness, infections, asthma, mental health disorders, poor perinatal outcomes, adverse experiences from trauma and displacement, and other harms. More numerous and increasingly dangerous natural disasters caused by climate change impair delivery of care by disrupting supply chains and compromising power supplies. Graduating trainees face a knowledge gap in understanding, managing, and mitigating these many-faceted consequences of climate change, which-expected to intensify in coming decades-will influence both the health of their patients and the health care they deliver. In this article, the authors propose a framework of climate change and health educational content for residents, including how climate change (1) harms health, (2) necessitates adaptation in clinical practice, and (3) undermines health care delivery. The authors propose not only learning objectives linked to the Accreditation Council for Graduate Medical Education core competencies for resident education but also learning formats and assessment strategies in each content area. They also present opportunities for implementation of climate and health education in residency training programs. Including this content in residency education will better prepare doctors to deliver anticipatory guidance to at-risk patients, manage those experiencing climate-related health effects, and reduce care disruptions during climate-driven extreme weather events.

Domoic acid and saxitoxin in seabirds in the United States between 2007 and 2018

As harmful algal blooms (HABs) increase in magnitude and duration worldwide, they are becoming an expanding threat to marine wildlife. Over the past decade, blooms of algae that produce the neurotoxins domoic acid (DA) and saxitoxin (STX) and documented concurrent seabird mortality events have increased bicoastally in the United States. We conducted a retrospective analysis of HAB related mortality events in California, Washington, and Rhode Island between 2007 and 2018 involving 12 species of seabirds, to document the levels, ranges, and patterns of DA and STX in eight sample types (kidney, liver, stomach, intestinal, cloacal, cecal contents, bile, blood) collected from birds during these events. Samples (n = 182) from 83 birds were examined for DA (n = 135) or STX (n = 17) or both toxins simultaneously (n = 30), using ELISA or LCMS at the National Oceanographic and Atmospheric Administration, National Marine Fisheries Service (NOAA-NMFS) Wildlife Algal-toxin Research and Response Network (WARRN-West) or the University of California, Santa Cruz (UCSC). DA or STX was detected in seven of the sample types with STX below the minimum detection limit in blood for the three samples tested. DA was found in 70% and STX was found in 23% of all tested samples. The ranges of detectable levels of DA and STX in all samples were 0.65-681,190.00 ng g^-1 and 2.00-20.95 ng g^-1, respectively. Cloacal contents from a Pacific loon (Gavia pacifica) collected in 2017 from Ventura County, California, had the highest maximum level of DA for all samples and species tested in this study. The highest level of STX for all samples and species was detected in the bile of a northern fulmar (Fulmarus glacialis) collected in 2018 from San Luis Obispo County, California. DA detections were consistently found in gastrointestinal samples, liver, bile, and kidney, whereas STX detections were most frequently seen in liver and bile samples. Co-occurring HAB toxins (DA and STX) were detected in white-winged scoters (Melanitta deglandi) in 2009, a Brandt's cormorant (Phalacrocorax penicillatus) in 2015, and a northern fulmar and common murre (Uria aalge) in 2018. This article provides DA and STX tissue concentrations and patterns in avian samples and shows the utility of various sample types for the detection of HAB toxins. Future research to understand the pharmacodynamics of these toxins in avian species and to establish lethal doses in various bird species would be beneficial.

The tide turns: Episodic and localized cross-contamination of a California coastline with cyanotoxins

The contamination of coastal ecosystems from a variety of toxins of marine algal origin is a common and well-documented situation along the coasts of the United States and globally. The occurrence of toxins originating from cyanobacteria along marine coastlines is much less studied, and little information exists on whether toxins from marine and freshwater sources co-occur regularly. The current study focused on the discharge of cyanotoxins from a coastal lagoon (Santa Clara River Estuary) as a consequence of an extreme tide event (King Tides; December 3-5, 2017) resulting in a breach of the berm separating the lagoon from the ocean. Monthly monitoring in the lagoon throughout 2017 documented more than a dozen co-occurring cyanobacterial genera, as well as multiple algal and cyanobacterial toxins. Biotoxin monitoring before and following the King Tide event using Solid Phase Adsorption Toxin Tracking (SPATT) in the lagoon and along the coast revealed the co-occurrence of microcystins, anatoxin, domoic acid, and other toxins on multiple dates and locations. Domoic acid was ubiquitously present in SPATT deployed in the lagoon and along the coast. Microcystins were also commonly detected in both locations, although the beach berm retained the lagoonal water for much of the year. Mussels collected along the coast contained microcystins in approximately half the samples, particularly following the King Tide event. Anatoxin was observed in SPATT only in late December, following the breach of the berm. Our findings indicate both episodic and persistent occurrence of both cyanotoxins and marine toxins may commonly contaminate coastlines in proximity to cyanobacteria-laden creeks and lagoons.

Improving in vitro ciguatoxin and brevetoxin detection: selecting neuroblastoma (Neuro-2a) cells with lower sensitivity to ouabain and veratridine (OV-LS)

Marine biotoxins accumulating in seafood products pose a risk to human health. These toxins are often potent in minute amounts and contained within complex matrices; requiring sensitive, reliable, and robust methods for their detection. The mouse neuroblastoma (Neuro-2a) cytotoxicity assay (N2a-assay) is a sensitive, high-throughput, in vitro method effective for detecting sodium channel-specific marine biotoxins. The N2a-assay can be conducted to distinguish between specific effects on voltage-gated sodium (Na_V) channels, caused by toxins that activate (e.g., ciguatoxins (CTXs), brevetoxins (PbTxs)) or block (e.g., tetrodotoxins, saxitoxins) the target Na_V. The sensitivity and specificity of the assay to compounds activating the Na_V are achieved through the addition of the pharmaceuticals ouabain (O) and veratridine (V). However, these compounds can be toxic to Neuro-2a cells and their application at insufficient or excessive concentrations can reduce the effectiveness of this assay for marine toxin detection. Therefore, during growth incubation, Neuro-2a cells were exposed to O and V, and surviving cells exhibiting a lower sensitivity to O and V (OV-LS) were propagated. OV-LS Neuro-2a cells were selected for 60-80% survival when exposed to 0.22/0.022 mM O/V during the cytotoxicity assay. At these conditions, OV-LS N2a cells demonstrated a 3.5-fold higher survival rate 71% ± 7.9 SD (n = 232), and lower sensitivity to O/V, compared to the original Neuro-2a cells 20% ± 9.0 SD (n = 16). Additionally, OV-LS N2a cells were 1.3-2.6-fold more sensitive for detecting CTX3C 1.35 pg/ml, CTX1B 2.06 pg/ml, and PbTx-3 3.04 ng/ml compared to Neuro-2a cells using 0.1/0.01 mM O/V. Detection of CTX3C in a complex fish matrix using OV-LS cells was 0.0048 pg CTX3C/mg fish tissue equivalent. This work shows the potential for a significant improvement in sensitivity for CTX3C, CTX1B, and PbTx-3 using the OV-LS N2a-assay.

Identification of influencing factors of A. catenella bloom using machine learning and numerical simulation

Alexandrium catenella (A. catenella) is a notorious algal species known to cause paralytic shellfish poisoning (PSP) in Korean coastal waters. There have been numerous studies on its temporal and spatial blooms in Korea. However, its bloom dynamics have not been fully understood because of the complexity in physical, chemical, and biological environments. This study aims to identify the factors that influence A. catenella blooms by applying a numerical model and machine learning. Intensive monitoring of A. catenella was conducted to investigate temporal variations in its population and its spatial distribution in the area with frequent occurrences of PSP bloom initiation. Moreover, a numerical model was built to analyze the ocean physical factors related to the bloom of A. catenella. Based on the information obtained from the monitored and simulated results, the decision tree (DT) method was applied to identify factors that caused the bloom. The outbreak of A. catenella was observed in the eastern coastal water of Geoje Island in 2017, recording a peak density of 4 × 10⁴ (cell L^-1). Retention time and particle scattering demonstrated that the physical force in 2017 was weaker than that in 2018, as shown by the smaller effects of advection and dispersion in 2017. The decision tree model showed that (1) water temperature below 17.21 °C was ideal for the growth of A. catenella, (2) phosphate influenced the growth of the species, and (3) cell density was accelerated with increasing retention time. The results from DT can contribute to the prediction of A. catenella blooms by determining the conditions that cause bloom initiation. Further, they can be used as a practical approach for mitigating HABs. Thus, machine learning and numerical simulation in this study can be a potential approach for effectively managing the bloom of A. catenella.

Introducing climate change into the biochemistry and molecular biology curriculum

Our climate is changing due to anthropogenic emissions of greenhouse gases from the production and use of fossil fuels. Present atmospheric levels of CO₂ were last seen 3 million years ago, when planetary temperature sustained high Arctic camels. As scientists and educators, we should feel a professional responsibility to discuss major scientific issues like climate change, and its profound consequences for humanity, with students who look up to us for knowledge and leadership, and who will be most affected in the future. We offer simple to complex backgrounds and examples to enable and encourage biochemistry educators to routinely incorporate this most important topic into their classrooms.

Assessing the Use of Molecular Barcoding and qPCR for Investigating the Ecology of Prorocentrum minimum (Dinophyceae), a Harmful Algal Species

Prorocentrum minimum is a species of marine dinoflagellate that occurs worldwide and can be responsible for harmful algal blooms (HABs). Some studies have reported it to produce tetrodotoxin; however, results have been inconsistent. qPCR and molecular barcoding (amplicon sequencing) using high-throughput sequencing have been increasingly applied to quantify HAB species for ecological analyses and monitoring. Here, we isolated a strain of P. minimum from eastern Australian waters, where it commonly occurs, and developed and validated a qPCR assay for this species based on a region of ITS rRNA in relation to abundance estimates from the cultured strain as determined using light microscopy. We used this tool to quantify and examine ecological drivers of P. minimum in Botany Bay, an estuary in southeast Australia, for over ~14 months in 2016–2017. We compared abundance estimates using qPCR with those obtained using molecular barcoding based on an 18S rRNA amplicon. There was a significant correlation between the abundance estimates from amplicon sequencing and qPCR, but the estimates from light microscopy were not significantly correlated, likely due to the counting method applied. Using amplicon sequencing, ~600 unique actual sequence variants (ASVs) were found, much larger than the known phytoplankton diversity from this region. P. minimum abundance in Botany Bay was found to be significantly associated with lower salinities and higher dissolved CO₂ levels.

Marine invertebrate interactions with Harmful Algal Blooms - Implications for One Health

Harmful Algal Blooms (HAB) are natural atypical proliferations of micro or macro algae in either marine or freshwater environments which have significant impacts on human, animal and ecosystem health. The causative HAB organisms are primarily dinoflagellates and diatoms in marine and cyanobacteria within freshwater ecosystems. Several hundred species of HABs, most commonly marine dinoflagellates affect animal and ecosystem health either directly through physical, chemical or biological impacts on surrounding organisms or indirectly through production of algal toxins which transfer through lower-level trophic organisms to higher level predators. Traditionally, a major focus of HABs has concerned their natural production of toxins which bioaccumulate in filter-feeding invertebrates, which with subsequent trophic transfer and biomagnification cause issues throughout the food web, including the human health of seafood consumers. Whilst in many regions of the world, regulations, monitoring and risk management strategies help mitigate against the impacts from HAB/invertebrate toxins upon human health, there is ever-expanding evidence describing enormous impacts upon invertebrate health, as well as the health of higher trophic level organisms and marine ecosystems. This paper provides an overview of HABs and their relationships with aquatic invertebrates, together with a review of their combined impacts on animal, human and ecosystem health. With HAB/invertebrate outbreaks expected in some regions at higher frequency and intensity in the coming decades, we discuss the needs for new science, multi-disciplinary assessment and communication which will be essential for ensuring a continued increasing supply of aquaculture foodstuffs for further generations.

Variable inter and intraspecies alkaline phosphatase activity within single cells of revived dinoflagellates

Adaptation of cell populations to environmental changes is mediated by phenotypic variability at the single-cell level. Enzyme activity is a key factor in cell phenotype and the expression of the alkaline phosphatase activity (APA) is a fundamental phytoplankton strategy for maintaining growth under phosphate-limited conditions. Our aim was to compare the APA among cells and species revived from sediments of the Bay of Brest (Brittany, France), corresponding to a pre-eutrophication period (1940's) and a beginning of a post-eutrophication period (1990's) during which phosphate concentrations have undergone substantial variations. Both toxic marine dinoflagellate Alexandrium minutum and the non-toxic dinoflagellate Scrippsiella acuminata were revived from ancient sediments. Using microfluidics, we measured the kinetics of APA at the single-cell level. Our results indicate that all S. acuminata strains had significantly higher APA than A. minutum strains. For both species, the APA in the 1990's decade was significantly lower than in the 1940's. For the first time, our results reveal both inter and intraspecific variabilities of dinoflagellate APA and suggest that, at a half-century timescale, two different species of dinoflagellate may have undergone similar adaptative evolution to face environmental changes and acquire ecological advantages.

Bistability in oxidative stress response determines the migration behavior of phytoplankton in turbulence

Turbulence has long been known to drive phytoplankton fitness and species succession: motile species dominate in calmer environments and non-motile species in turbulent conditions. Yet a mechanistic understanding of the effect of turbulence on phytoplankton migratory behavior and physiology is lacking. By combining a method to generate turbulent cues, quantification of stress accumulation and physiology, and a mathematical model of stress dynamics, we show that motile phytoplankton use their mechanical stability to sense the intensity of turbulent cues and integrate these cues in time via stress signaling to trigger switches in migratory behavior. The stress-mediated warning strategy we discovered provides a paradigm for how phytoplankton cope with turbulence, thereby potentially governing which species will be successful in a changing ocean.

Turbulence is an important determinant of phytoplankton physiology, often leading to cell stress and damage. Turbulence affects phytoplankton migration both by transporting cells and by triggering switches in migratory behavior, whereby vertically migrating cells can actively invert their direction of migration upon exposure to turbulent cues. However, a mechanistic link between single-cell physiology and vertical migration of phytoplankton in turbulence is currently missing. Here, by combining physiological and behavioral experiments with a mathematical model of stress accumulation and dissipation, we show that the mechanism responsible for the switch in the direction of migration in the marine raphidophyte Heterosigma akashiwo is the integration of reactive oxygen species (ROS) signaling generated by turbulent cues. Within timescales as short as tens of seconds, the emergent downward-migrating subpopulation exhibited a twofold increase in ROS, an indicator of stress, 15% lower photosynthetic efficiency, and 35% lower growth rate over multiple generations compared to the upward-migrating subpopulation. The origin of the behavioral split as a result of a bistable oxidative stress response is corroborated by the observation that exposure of cells to exogenous stressors (H₂O₂, UV-A radiation, or high irradiance), in lieu of turbulence, caused comparable ROS accumulation and an equivalent split into the two subpopulations. By providing a mechanistic link between the single-cell mechanics of swimming and physiology on the one side and the emergent population-scale migratory response and impact on fitness on the other, the ROS-mediated early warning response we discovered contributes to our understanding of phytoplankton community composition in future ocean conditions.

Effect of sea surface temperature and precipitation on annual frequency of harmful algal blooms in the East China Sea over the past decades

Coastal harmful algal blooms (HABs) in China's seas have attracted researchers' attention for decades. Among the four seas of China, the HAB frequency is the highest in the East China Sea (ECS). The impact of climate change and anthropogenic dominant factors on HABs is not well quantified and the response of HABs to the changing climate is also not clear. Here, we compiled a time series of observation-based HAB events since the 1980s and performed a regional assessment to elucidate the dominant drivers of HAB events in the ECS. The results showed that the increase in the frequency of HAB events in the ECS between 2000 and 2003 was associated with increases in dissolved inorganic phosphorus and sea surface temperature anomalies as well as decreasing summer precipitation. The declining annual frequency in HAB events in the ECS after 2003 was associated with the two climatological factors, most notably, precipitation. Under the "business-as-usual" scenario, climate change will increase the annual HAB events in the ECS from the historical frequency (1985-2013) by more than five-fold by the end of 21st century. These findings demonstrated that management strategies based on reducing nutrient loading also need to consider the effects of climate change in the future.

Marine harmful algal blooms (HABs) in the United States: History, current status and future trends

Harmful algal blooms (HABs) are diverse phenomena involving multiple. species and classes of algae that occupy a broad range of habitats from lakes to oceans and produce a multiplicity of toxins or bioactive compounds that impact many different resources. Here, a review of the status of this complex array of marine HAB problems in the U.S. is presented, providing historical information and trends as well as future perspectives. The study relies on thirty years (1990-2019) of data in HAEDAT - the IOC-ICES-PICES Harmful Algal Event database, but also includes many other reports. At a qualitative level, the U.S. national HAB problem is far more extensive than was the case decades ago, with more toxic species and toxins to monitor, as well as a larger range of impacted resources and areas affected. Quantitatively, no significant trend is seen for paralytic shellfish toxin (PST) events over the study interval, though there is clear evidence of the expansion of the problem into new regions and the emergence of a species that produces PSTs in Florida - Pyrodinium bahamense. Amnesic shellfish toxin (AST) events have significantly increased in the U.S., with an overall pattern of frequent outbreaks on the West Coast, emerging, recurring outbreaks on the East Coast, and sporadic incidents in the Gulf of Mexico. Despite the long historical record of neurotoxic shellfish toxin (NST) events, no significant trend is observed over the past 30 years. The recent emergence of diarrhetic shellfish toxins (DSTs) in the U.S. began along the Gulf Coast in 2008 and expanded to the West and East Coasts, though no significant trend through time is seen since then. Ciguatoxin (CTX) events caused by Gambierdiscus dinoflagellates have long impacted tropical and subtropical locations in the U.S., but due to a lack of monitoring programs as well as under-reporting of illnesses, data on these events are not available for time series analysis. Geographic expansion of Gambierdiscus into temperate and non-endemic areas (e.g., northern Gulf of Mexico) is apparent, and fostered by ocean warming. HAB-related marine wildlife morbidity and mortality events appear to be increasing, with statistically significant increasing trends observed in marine mammal poisonings caused by ASTs along the coast of California and NSTs in Florida. Since their first occurrence in 1985 in New York, brown tides resulting from high-density blooms of Aureococcus have spread south to Delaware, Maryland, and Virginia, while those caused by Aureoumbra have spread from the Gulf Coast to the east coast of Florida. Blooms of Margalefidinium polykrikoides occurred in four locations in the U.S. from 1921-2001 but have appeared in more than 15  U.S. estuaries since then, with ocean warming implicated as a causative factor. Numerous blooms of toxic cyanobacteria have been documented in all 50  U.S. states and the transport of cyanotoxins from freshwater systems into marine coastal waters is a recently identified and potentially significant threat to public and ecosystem health. Taken together, there is a significant increasing trend in all HAB events in HAEDAT over the 30-year study interval. Part of this observed HAB expansion simply reflects a better realization of the true or historic scale of the problem, long obscured by inadequate monitoring. Other contributing factors include the dispersion of species to new areas, the discovery of new HAB poisoning syndromes or impacts, and the stimulatory effects of human activities like nutrient pollution, aquaculture expansion, and ocean warming, among others. One result of this multifaceted expansion is that many regions of the U.S. now face a daunting diversity of species and toxins, representing a significant and growing challenge to resource managers and public health officials in terms of toxins, regions, and time intervals to monitor, and necessitating new approaches to monitoring and management. Mobilization of funding and resources for research, monitoring and management of HABs requires accurate information on the scale and nature of the national problem. HAEDAT and other databases can be of great value in this regard but efforts are needed to expand and sustain the collection of data regionally and nationally.

Diversity and regional distribution of harmful algal events along the Atlantic margin of Europe

The IOC-ICES-PICES Harmful Algal Event Database (HAEDAT) was used to describe the diversity and spatiotemporal distribution of harmful algal events along the Atlantic margin of Europe from 1987 - 2018. The majority of events recorded are caused by Diarrhetic Shellfish Toxins (DSTs). These events are recorded annually over a wide geographic area from southern Spain to northern Scotland and Iceland, and are responsible for annual closures of many shellfish harvesting areas. The dominant causative dinoflagellates, members of the morphospecies 'Dinophysis acuminata complex' and D. acuta, are common in the waters of the majority of countries affected. There are regional differences in the causative species associated with PST events; the coasts of Spain and Portugal with the dinoflagellates Alexandrium minutum and Gymnodinium catenatum, north west France/south west England/south Ireland with A. minutum, and Scotland/Faroe Islands/Iceland with A. catenella. This can influence the duration and spatial scale of PST events as well as the toxicity of shellfish. The diatom Pseudo-nitzschia australis is the most widespread Domoic Acid (DA) producer, with records coming from Spain, Portugal, France, Ireland and the UK. Amnesic Shellfish Toxins (ASTs) have caused prolonged closures for the scallop fishing industry due to the slow depuration rate of DA. Amendments to EU shellfish hygiene regulations introduced between 2002 and 2005 facilitated end-product testing and sale of adductor muscle. This reduced the impact of ASTs on the scallop fishing industry and thus the number of recorded HAEDAT events. Azaspiracids (AZAs) are the most recent toxin group responsible for events to be characterised in the ICES area. Events associated with AZAs have a discrete distribution with the majority recorded along the west coast of Ireland. Ciguatera Poisoning (CP) has been an emerging issue in the Canary Islands and Madeira since 2004. The majority of aquaculture and wild fish mortality events are associated with blooms of the dinoflagellate Karenia mikimotoi and raphidophyte Heterosigma akashiwo. Such fish killing events occur infrequently yet can cause significant mortalities. Interannual variability was observed in the annual number of HAEDAT areas with events associated with individual shellfish toxin groups. HABs represent a continued risk for the aquaculture industry along the Atlantic margin of Europe and should be accounted for when considering expansion of the industry or operational shifts to offshore areas.

Exposure to marine benthic dinoflagellate toxins may lead to mitochondrial dysfunction

Even though marine dinoflagellates are important primary producers, many toxic species may alter the natural equilibrium of aquatic ecosystems and even generate human intoxication incidents, as they are the major causative agents of harmful algal blooms. In order to deepen the knowledge regarding benthic dinoflagellate adverse effects, the present study aims to clarify the influence of Gambierdiscus excentricus strain UNR-08, Ostreopsis cf. ovata strain UNR-03 and Prorocentrum lima strain UNR-01 crude extracts on rat mitochondrial energetic function and permeability transition pore (mPTP) induction. Our results, expressed in number of dinoflagellate cell toxic compounds tested in a milligram of mitochondrial protein, revealed that 934 cells mg prot-1 of G. excentricus, and 7143 cells mg prot-1 of both O. cf. ovata and P. lima negatively affect mitochondrial function, including by decreasing ATP synthesis-related membrane potential variations. Moreover, considerably much lower concentrations of dinoflagellate extracts (117 cells mg prot-1 of G. excentricus, 1429 cells mg prot-1 of O. cf. ovata and 714 cells mg prot-1 of P. lima) produced mPTP-induced swelling in Ca2+-loaded isolated mitochondria. The present study clearly demonstrates the toxicity of G. excentricus, O. cf. ovata and P. lima extracts at the mitochondrial level, which may lead to mitochondrial failure and consequent cell toxicity, and that G. excentricus always provide much more severe effects than O. cf. ovata and P. lima.

Current distribution and potential expansion of the harmful benthic dinoflagellate Ostreopsis cf. siamensis towards the warming waters of the Bay of Biscay, North-East Atlantic

In a future scenario of increasing temperatures in North-Atlantic waters, the risk associated with the expansion of the harmful, benthic dinoflagellate Ostreopsis cf. siamensis has to be evaluated and monitored. Microscopy observations and spatio-temporal surveys of environmental DNA (eDNA) were associated with Lagrangian particle dispersal simulations to: (i) establish the current colonization of the species in the Bay of Biscay, (ii) assess the spatial connectivity among sampling zones that explain this distribution, and (iii) identify the sentinel zones to monitor future expansion. Throughout a sampling campaign carried out in August to September 2018, microscope analysis showed that the species develops in the south-east of the bay where optimal temperatures foster blooms. Quantitative PCR analyses revealed its presence across almost the whole bay to the western English Channel. An eDNA time-series collected on plastic samplers showed that the species occurs in the bay from April to September. Due to the water circulation, colonization of the whole bay from the southern blooming zones is explained by inter-site connectivity. Key areas in the middle of the bay permit continuous dispersal connectivity towards the north. These key areas are proposed as sentinel zones to monitor O. cf. siamensis invasions towards the presumably warming water of the North-East Atlantic.

Genome-wide single nucleotide polymorphism markers reveal population structure and dispersal direction of an expanding nuisance algal bloom species

Species invasion and range expansion are currently under scrutiny due to increasing anthropogenic impact on the natural environment. This is also true for harmful algal blooms, which have been reported to have increased in frequency. However, this research is challenging due to the ephemeral nature, small size and mostly low concentrations of microalgae in the environment. One such species is the nuisance microalga Gonyostomum semen (Raphidophyceae), which has increased in occurrence in northern Europe in recent decades. The question of whether the species has expanded its habitat range or if it was already present in the lakes but was too rare to be detected remains unanswered. The aim of the present study was to determine the genetic structure and dispersal pathways of G. semen using RAD (restriction-site-associated DNA) tag sequencing. For G. semen, which has a huge genome (32 Gbp), we faced particular challenges, but were nevertheless able to recover over 1000 single nucleotide polymorphisms at high coverage. Our data revealed a distinct population genetic structure, demonstrating a divide of western and eastern populations that probably represent different lineages. Despite significant genetic differentiation among lakes, we found only limited isolation-by-distance. While we had expected a pattern of recent expansion northwards, the data demonstrated gene flow from the northeast/east towards the southwest/west. This genetic signature suggests that the observed gene flow may be due to dispersal by autumn migratory birds, which act as dispersal vectors of resistant resting propagules that form at the end of the G. semen blooms.

Contemporary aquaculture: implications for human nutrition

Aquaculture is increasing the global supply of foods, and holds tremendous potential to address malnutrition and diet-related diseases. The species selected and feeds used affects the nutrients available from aquaculture. Progress in the development of novel and sustainable aquaculture feeds to reduce reliance on wild fisheries, feed fortification to increase nutrient content, and expansion of the diversity of aquatic species produced are key areas for continued research and development. Ultimately, the degree to which aquaculture will contribute to nutrition depends largely on who can access the fish produced, which will be shaped by production technology as well as trade and price dynamics. Finally, the contribution of aquaculture expansion to improving nutrition will be bounded by aquaculture's environmental sustainability.

An assessment of temporal, spatial and taxonomic trends in harmful algal toxin exposure in stranded marine mammals from the U.S. New England coast

Despite a long-documented history of severe harmful algal blooms (HABs) in New England coastal waters, corresponding HAB-associated marine mammal mortality events in this region are far less frequent or severe relative to other regions where HABs are common. This long-term survey of the HAB toxins saxitoxin (STX) and domoic acid (DA) demonstrates significant and widespread exposure of these toxins in New England marine mammals, across multiple geographic, temporal and taxonomic groups. Overall, 19% of the 458 animals tested positive for one or more toxins, with 15% and 7% testing positive for STX and DA, respectively. 74% of the 23 different species analyzed demonstrated evidence of toxin exposure. STX was most prevalent in Maine coastal waters, most frequently detected in common dolphins (Delphinus delphis), and most often detected during July and October. DA was most prevalent in animals sampled in offshore locations and in bycaught animals, and most frequently detected in mysticetes, with humpback whales (Megaptera novaeangliae) testing positive at the highest rates. Feces and urine appeared to be the sample matrices most useful for determining the presence of toxins in an exposed animal, with feces samples having the highest concentrations of STX or DA. No relationship was found between the bloom season of toxin-producing phytoplankton and toxin detection rates, however STX was more likely to be present in July and October. No relationship between marine mammal dietary preference and frequency of toxin detection was observed. These findings are an important part of a framework for assessing future marine mammal morbidity and mortality events, as well as monitoring ecosystem health using marine mammals as sentinel organisms for predicting coastal ocean changes.

Simple determination of six groups of lipophilic marine algal toxins in seawater by automated on-line solid phase extraction coupled to liquid chromatography-tandem mass spectrometry

Lipophilic marine algal toxins (LMATs) are highly toxic secondary metabolites produced by marine microalgae that pose a great threat to marine aquaculture organisms and human health. In this study, a novel and automated method for the simultaneous determination of six groups of LMATs in seawater was developed by on-line solid phase extraction (SPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Condition optimization and method validation were performed, and the recoveries of all 14 target LMATs featuring different properties ranged from 83.5% to 96.0%. The limits of detection of most target compounds were within ≤3.000 ng/L with good precision (relative standard deviation ≤ 12.1%) and linearity (R²≥0.9916). Compared with off-line SPE methods, the proposed on-line SPE method has better recovery, sensitivity, repeatability, and throughput; in addition, the volume of seawater sample necessary to conduct determinations is greatly reduced in the present method. Finally, the method was applied to determine LMATs in actual seawater samples collected from the Bohai and South Yellow Seas of China in summer, and okadaic acid and pectenotoxin-2 were detected in all seawater samples. The highest concentration of ∑LMATs (22.23 ng/L) occurred in the coastal mariculture area of Shandong Province. Therefore, routine monitoring of LMATs in seawater of the coastal mariculture zone is necessary to prevent shellfish contamination especially in summer, and the proposed on-line SPE-LC-MS/MS method is a powerful way for direct and automatic detection of various LMATs in coastal mariculture area.

Landscape-scale patterns of nutrient enrichment in a coral reef ecosystem: implications for coral to algae phase shifts

Nutrient pollution is altering coastal ecosystems worldwide. On coral reefs, excess nutrients can favor the production of algae at the expense of reef-building corals, yet the role of nutrients in driving community changes such as shifts from coral to macroalgae is not well understood. Here we investigate the potential role of anthropogenic nutrient loading in driving recent coral-to-macroalgae phase shifts on reefs in the lagoons surrounding the Pacific island of Moorea, French Polynesia. We use nitrogen (N) tissue content and stable isotopes (δ¹⁵ N) in an abundant macroalga (Turbinaria ornata) together with empirical models of nutrient discharge to describe spatial and temporal patterns of nutrient enrichment in the lagoons. We then employ time series data to test whether recent increases in macroalgae are associated with nutrients. Our results revealed that patterns of N enrichment were linked to several factors, including rainfall, wave-driven circulation, and distance from anthropogenic nutrient sources, especially human sewage. Reefs near large watersheds, where inputs of N from sewage and agriculture are high, have been consistently enriched in N for at least the last decade. In many of these areas, corals have decreased and macroalgae have increased, while reefs with lower levels of N input have maintained high cover of coral and low cover of macroalgae. Importantly, these patchy phase shifts to macroalgae have occurred despite substantial island-wide increases in the density and biomass of herbivorous fishes over the time period. Together, these results indicate that nutrient loading may be an important driver of coral-to-macroalgae phase shifts in the lagoons of Moorea even though the reefs harbor an abundant and diverse herbivore assemblage. These results emphasize the important role that bottom-up factors can play in driving coral-to-macroalgae phase shifts and underscore the critical importance of watershed management for reducing inputs of nutrients and other land-based pollutants to coral reef ecosystems.

Aqueous photodegradation of okadaic acid and dinophysistoxin-1: Persistence, kinetics, photoproducts, pathways, and toxicity evaluation

Diarrhetic shellfish poisoning (DSP) toxins are a class of natural organic contaminants that pose a serious threat not only to marine ecosystems and fisheries but also to human health. They are widely distributed in coastal and offshore waters around the world. However, the persistence and photochemical degradation characteristics of DSP in an aqueous environment are still unclear. This study aimed to elucidate the photochemical fate of two representative DSP toxins, namely, okadaic acid (OA) and dinophysistoxin-1 (DTX1). Results showed that photo-mediated chemical reactions play a crucial role in eliminating DSP toxins in seawater. However, the degradation of OA and DTX1 was relatively slow under natural solar radiation, with a removal efficiency of 90.0% after exposure for more than 20 days. When the reaction solutions of OA and DTX1 were exposed to Hg lamp radiation, their degradation followed pseudo-first-order kinetics, and was remarkably influenced by seawater pH and metal-ion concentration. A total of 24 tentative transformation products (TPs) of OA and DTX1 were identified via liquid chromatography high-resolution mass spectrometry. C12 (C₄₃H₆₆O₁₁) and C24 (C₄₄H₆₈O₁₁) were the main TPs. The following possible photodegradation pathways were proposed: decarboxylation, photoinduced hydrolysis, chain scission, and photo-oxidation. Toxicity assays via protein phosphatase 2A inhibition proved that photochemical processes could significantly reduce the DSP toxicity of irradiated solutions by approximately 88%. This work provides an enhanced understanding of the fate of DSP toxins in the aqueous environment, allowing for an improved assessment of their environmental impacts.

Simultaneous removal of harmful algal cells and toxins by a Ag2CO3-N:GO photocatalyst coating under visible light

The frequent harmful algae blooms (HABs) in eutrophic waters pose serious threats to the water environment and health of human beings and animals. In this study, a new type of photocatalytic coating was prepared by loading Ag₂CO₃-N:GO (AGON) on the polyurethane sponge modified by silica sol via a dip coating method for the photocatalytic inactivation of Microcystis aeruginosa (M. aeruginosa) and degradation of Microcystin-LR (MC-LR). The factors including photocatalyst loading dosage, natural organic matter (NOM), and alkalinity were studied. The effects on the physiological characteristics of M. aeruginosa and reactive oxygen species (ROS) were also investigated to reveal the photocatalytic inactivation mechanisms. The results showed that the AGON coating-4 (the initial concentration of AGON suspension used for loading is 4 g/L) exhibited the optimum photocatalytic performance under visible light, which can completely remove chlorophyll a after 5 h of irradiation. And the NOM and alkalinity in water have relatively negative effects on the photocatalytic inactivation of algae. The prepared AGON coating also exhibited excellent photocatalytic performance in the degradation of MC-LR under visible light. It only needed 20, 60 and 120 min to completely degrade 0.1, 0.3 and 0.5 mg/L MC-LR, respectively. However, the mixed systems of algae and MC-LR required a longer time to achieve photocatalytic degradation. The O₂^- were the predominant reactive oxygen species, causing the damage of cell membranes and walls and the leakage of cellular content, which eventually led to the irreversible damage to algal cells. What's more, the coating can be reused several times due to its good cyclability and stability. Therefore, the AGON coating has promising prospects for the treatment of algal blooms in eutrophic waters.

Easy detection of karlodinium veneficum using PCR-based dot chromatography strip

In this study, a novel detection method by PCR-based dot chromatography strip (PDCS) is proposed. To investigate the application of PDCS in the detection of harmful microalgae, the internal transcribed spacer sequence of Karlodinium veneficum, one of the most common bloom-forming species, was cloned and sequenced to design and screen specific primers with tag sequences and probes, including gold nanoparticle probe, test probe, and control probe. The PDCS was prepared manually, and PCR amplicons prepared from the genomic DNA of K. veneficum using tagged specific primers were analyzed by PDCS for visual detection of the target species. The resulting test strip showed red spots at the predicted test and control points visible to the naked eyes, showing the successful development of PDCS. This detection technique is independent of expensive experimental equipment (except a DNA thermal cycler for PCR) but requires an aliquot of PCR amplicons mixed with development buffer to apply to the sample pad of PDCS for approximately 10 min to visualize the analytical results. Cross-reactivity test with 21 microalgae, including K. veneficum, showed that the established PDCS technique has excellent specificity. The detection limit of PDCS was 9.13 × 10^-2 ng μL^-1 for genomic DNA and 5.3 × 10⁵ cells L ^- 1 for crude DNA extracts of the target alga. In summary, the PDCS with high sensitivity and specificity can be prepared by hand, which is less expensive than traditional strip, thus providing a promising alternative to the detection of K. veneficum in natural samples.

Random forest classification to determine environmental drivers and forecast paralytic shellfish toxins in Southeast Alaska with high temporal resolution

Paralytic shellfish poison toxins (PSTs) produced by the dinoflagellate in the genus Alexandrium are a threat to human health and subsistence lifestyles in Southeast Alaska. It is important to understand the drivers of Alexandrium blooms to inform shellfish management and aquaculture, as well as to predict trends of PST in a changing climate. In this study, we aggregate environmental data sets from multiple agencies and tribal partners to model and predict concentrations of PSTs in Southeast Alaska from 2016 to 2019. We used daily PST concentrations interpolated from regularly sampled blue mussels (Mytilus trossulus) analyzed for total PSTs using a receptor binding assay. We then created random forest models to classify shellfish above and below a threshold of toxicity (80 µg 100 g^-1) and used two methods to determine variable importance. We obtained a multivariate model with key variables being sea surface temperature, salinity, freshwater discharge, and air temperature. We then used a similar model trained using lagged environmental variables to hindcast out-of-sample (OOS) shellfish toxicities during April-October in 2017, 2018, and 2019. Hindcast OOS accuracies were low (37-50%); however, we found forecasting using environmental variables may be useful in predicting the timing of early summer blooms. This study reinforces the efficacy of machine learning to determine important drivers of harmful algal blooms, although more complex models incorporating other parameters such as toxicokinetics are likely needed for accurate regional forecasts.

Tracking Alexandrium catenella from seed-bed to bloom on the southern coast of Korea

Alexandrium catenella was tracked from seed-bed to bloom at a hot spot of cyst deposition on the southern coast of Korea from June 2016 to Feb. 2020. Changes in cyst abundance and germinability from sediment, as well as the vegetative cell abundance and encystment in the water column were intensively monitored. Cyst germination of ca. 73% occurred synchronously in November of 2016 to 2019, when bottom water temperature was around 15 °C. After mass germination, vegetative cells formed a seed populations at low density (<10 cells L^-1) during winter. Overwintering populations initiated growth in March and then proliferated into high density (ca. 4 × 10⁴ cells L^-1) spring blooms in mid-April 2017 when moderate temperature (15 °C) was recorded. There was no bloom in spring of 2018 and 2019, but small vegetative populations developed. Decline of the spring bloom was followed by massive encystment and an increase in Noctiluca abundance. An average spring encystment ratio of 0.002 was estimated for the study years. Newly formed cysts lay dormant during the warm season lasting about six months and then seeded the next population of vegetative cells. An average contribution ratio of cells recruited from the sediment was ca. 0.09 for seeding winter populations. The range in shift ratios for spring production of a daughter cyst population to prior cyst abundance of the mother population in fall was 0.1 to 0.6 for consecutive years, depending on annual variation of local environments. Tracking mass transformation of A. catenella cysts will contribute to more effective science based management of paralytic shellfish poisoning on the southern Korean coast.

An approach for evaluating the economic impacts of harmful algal blooms: The effects of blooms of toxic Dinophysis spp. on the productivity of Scottish shellfish farms

Shellfish production is an important activity for the economy of many countries. As well as its direct value, it helps to stabilize communities in rural areas characterized by limited job opportunities. It is also important for consumers who recognize shellfish as a healthy product that gains its nutrition from natural plankton without the need for fertilizers, chemical treatments or other anthropogenic intervention typical of terrestrial agriculture or other marine aquaculture. Nevertheless, global shellfish fisheries are under threat from harmful algal blooms (HABs) and related biotoxins, whose production is potentially exacerbated by global changes. This research provides evidence of economic impacts on Scottish shellfish farms in the last 10 years caused by HABs and their associated biotoxins. In contrast to previous approaches that have focused on variation in production as a function of temporal trends and blooms events, we use a production function approach to show which input factors (labour, capital, climate variables, concentration of biotoxins) have an effect on production. Results show that diarrhoetic shellfish toxins produced by the genera Dinophysis are most significant. A 1% change in the production of these biotoxins reduces shellfish production by 0.66%, with an average yearly negative variation in production of 15% (1,080 ton) and an economic loss (turnover) of  £ (GBP) 1.37 m per year (in 2015 currency) over a national annual industry turnover of ~ £ 12 m. The production function approach is coupled with a multivariate time series model (VAR) capturing the statistical relationship between algal concentration, information on climatic variables and biotoxins to forecast the damage to shellfish production from HABs. This provides producers and regulators with the economic information to plan temporal and spatial mitigating measures necessary to limit damages to production by comparing the costs of these measures with the costs of lost production.

Protocols for Monitoring Harmful Algal Blooms for Sustainable Aquaculture and Coastal Fisheries in Chile

Harmful algae blooms (HABs) cause acute effects on marine ecosystems due to their production of endogenous toxins or their enormous biomass, leading to significant impacts on local economies and public health. Although HAB monitoring has been intensively performed at spatiotemporal scales in coastal areas of the world over the last decades, procedures have not yet been standardized. HAB monitoring procedures are complicated and consist of many methodologies, including physical, chemical, and biological water sample measurements. Each monitoring program currently uses different combinations of methodologies depending on site specific purposes, and many prior programs refer to the procedures in quotations. HAB monitoring programs in Chile have adopted the traditional microscopic and toxin analyses but not molecular biology and bacterial assemblage approaches. Here we select and optimize the HAB monitoring methodologies suitable for Chilean geography, emphasizing on metabarcoding analyses accompanied by the classical tools with considerations including cost, materials and instrument availability, and easiness and efficiency of performance. We present results from a pilot study using the standardized stepwise protocols, demonstrating feasibility and plausibility for sampling and analysis for the HAB monitoring. Such specific instructions in the standardized protocol are critical obtaining quality data under various research environments involving multiple stations, different analysts, various time-points, and long HAB monitoring duration.

Urea Inputs Drive Picoplankton Blooms in Sarasota Bay, Florida, U.S.A

Recent increases in global urea usage, including its incorporation in slow-release fertilizers commonly used in lawn care in Florida, have the potential to alter the form and amount of nitrogen inputs to coastal waters. This shift may, in turn, impact phytoplankton community diversity and nutrient cycling processes. An autonomous water quality monitoring and sampling platform containing meteorological and water quality instrumentation, including urea and phycocyanin sensors, was deployed between June and November of 2009 in Sarasota Bay, Florida. This shallow, lagoonal bay is characterized by extensive and growing urban and suburban development and limited tidal exchange and freshwater inputs. During the monitoring period, three high-biomass (up to 40 µg chlorophyll-a·L−1) phytoplankton blooms dominated by picocyanobacteria or picoeukaryotes were observed. Each bloom was preceded by elevated (up to 20 μM) urea concentrations. The geolocation of these three parameters suggests that “finger canals” lining the shore of Sarasota Bay were the source of urea pulses and there is a direct link between localized urea inputs and downstream picoplankton blooms. Furthermore, high frequency sampling is required to detect the response of plankton communities to pulsed events.

Cultures of Dinophysis sacculus, D. acuminata and pectenotoxin 2 affect gametes and fertilization success of the Pacific oyster, Crassostrea gigas

Harmful algal blooms (HABs) of toxic species of the dinoflagellate genus Dinophysis are a threat to human health as they are mainly responsible for diarrheic shellfish poisoning (DSP) in the consumers of contaminated shellfish. Such contamination leads to shellfish farm closures causing major economic and social issues. The direct effects of numerous HAB species have been demonstrated on adult bivalves, whereas the effects on critical early life stages remain relatively unexplored. The present study aimed to determine the in vitro effects of either cultivated strains of D. sacculus and D. acuminata isolated from France or their associated toxins (i.e. okadaic acid (OA) and pectenotoxin 2 (PTX2)) on the quality of the gametes of the Pacific oyster Crassostrea gigas. This was performed by assessing the ROS production and viability of the gametes using flow cytometry, and fertilization success using microscopic counts. Oocytes were more affected than spermatozoa and their mortality and ROS production increased in the presence of D. sacculus and PTX2, respectively. A decrease in fertilization success was observed at concentrations as low as 0.5 cell mL^-1 of Dinophysis spp. and 5 nM of PTX2, whereas no effect of OA could be observed. The effect on fertilization success was higher when both gamete types were concomitantly exposed compared to separate exposures, suggesting a synergistic effect. Our results also suggest that the effects could be due to cell-to-cell contact. These results highlight a potential effect of Dinophysis spp. and PTX2 on reproduction and recruitment of the Pacific oyster.

Marine harmful algal blooms and human health: A systematic scoping review

Exposure to harmful algal blooms (HABs) can lead to well recognised acute patterns of illness in humans. The objective of this scoping review was to use an established methodology and the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting framework to map the evidence for associations between marine HABs and observed both acute and chronic human health effects. A systematic and reproducible search of publications from 1985 until May 2019 was conducted using diverse electronic databases. Following de-duplication, 5301 records were identified, of which 380 were included in the final qualitative synthesis. The majority of studies (220; 57.9%) related to Ciguatera Poisoning. Anecdotal and case reports made up the vast majority of study types (242; 63.7%), whereas there were fewer formal epidemiological studies (35; 9.2%). Only four studies related to chronic exposure to HABs. A low proportion of studies reported the use of human specimens for confirmation of the cause of illness (32; 8.4%). This study highlighted gaps in the evidence base including a lack of formal surveillance and epidemiological studies, limited use of toxin measurements in human samples, and a scarcity of studies of chronic exposure. Future research and policy should provide a baseline understanding of the burden of human disease to inform the evaluation of the current and future impacts of climate change and HABs on human health.

Distribution of Harmful Algal Growth-Limiting Bacteria on Artificially Introduced Ulva and Natural Macroalgal Beds

The intensity and frequency of harmful algal blooms (HABs) have increased, posing a threat to human seafood resources due to massive kills of cultured fish and toxin contamination of bivalves. In recent years, bacteria that inhibit the growth of HAB species were found to be densely populated on the biofilms of some macroalgal species, indicating the possible biological control of HABs by the artificial introduction of macroalgal beds. In this study, an artificially created Ulva pertusa bed using mobile floating cages and a natural macroalgal bed were studied to elucidate the distribution of algal growth-limiting bacteria (GLB). The density of GLB affecting fish-killing raphidophyte Chattonella antiqua, and two harmful dinoflagellates, were detected between 106 and 107 CFU g−1 wet weight on the biofilm of artificially introduced U. pertusa and 10 to 102 CFU mL−1 from adjacent seawater; however, GLB found from natural macroalgal species targeted all tested HAB species (five species), ranging between 105 and 106 CFU g−1 wet weight in density. These findings provide new ecological insights of GLB at macroalgal beds, and concurrently demonstrate the possible biological control of HABs by artificially introduced Ulva beds.

Outbreak of diarrhetic shellfish poisoning associated with consumption of mussels, United Kingdom, May to June 2019

We report on six cases of diarrhetic shellfish poisoning following consumption of mussels harvested in the United Kingdom. Dinophysis spp. in the water column was found to have increased rapidly at the production site resulting in high levels of okadaic acid-group lipophilic toxins in the flesh of consumed mussels. Clinicians and public health professionals should remain aware of algal-derived toxins being a potential cause of illness following seafood consumption.

Atmospheric Forcing of the High and Low Extremes in the Sea Surface Temperature over the Red Sea and Associated Chlorophyll-a Concentration

Taking advantage of 37-year-long (1982–2018) of high-quality satellite datasets, we examined the role of direct atmospheric forcing on the high and low sea surface temperature (SST) extremes over the Red Sea (RS). Considering the importance of SST in regulating ocean physics and biology, the associated impacts on chlorophyll (Chl-a) concentration were also explored, since a small change in SST can cause a significant impact in the ocean. After describing the climate features, we classified the top 5% of SST values (≥31.5 °C) as extreme high events (EHEs) during the boreal summer period and the lowest SST values (≤22.8 °C) as extreme low events (ELEs) during the boreal winter period. The spatiotemporal analysis showed that the EHEs (ELEs) were observed over the southern (northern) basin, with a significant warming trend of 0.027 (0.021) °C year−1, respectively. The EHEs were observed when there was widespread less than average sea level pressure (SLP) over southern Europe, northeast Africa, and Middle East, including in the RS, leading to the cold wind stress from Europe being relatively less than usual and the intrusion of stronger than usual relatively warm air mass from central Sudan throughout the Tokar Gap. Conversely, EHEs were observed when above average SLP prevailed over southern Europe and the Mediterranean Sea as a result of the Azores high and westward extension of the Siberian anticyclone, which led to above average transfer of cold and dry wind stress from higher latitudes. At the same time, notably less wind stress due to southerlies that transfer warm and humid air masses northward was observed. Furthermore, physical and biological responses related to extreme stress showed distinct ocean patterns associated with each event. It was found that the Chl-a concentration anomalies over the northern basin caused by vertical nutrient transport through deep upwelling processes are the manifestation of the superimposition of ELEs. The situation was the opposite for EHEs due to the stably stratified ocean boundary layer, which is a well-known consequence of global warming.

Establishment of double probes rolling circle amplification combined with lateral flow dipstick for rapid detection of Chattonella marina

Chattonella marina is one of the main algae that could cause harmful algal blooms. It has killed a large number of cultured fish in coastal areas of many countries, causing serious economic losses. Therefore, it is necessary to establish a method that can specifically detect C. marina at pre-bloom abundance, so that timely measures can be taken before this alga causes harm. In this study, a long probe, a short probe and a pair of amplification primers were first designed by using the internal transcribed spacer (ITS) sequence of C. marina as the target gene and using the CD74 gene of a distant species Gallus gallus as the base sequence. The double probes rolling circle amplification (dpRCA) system was then established with the designed probes and amplification primers. A novel detection protocol referred to as dpRCA-LFD by combining the dpRCA products and lateral flow dipstick (LFD) was finally established, which can make the detection results visible to the naked eyes. The reaction conditions of dpRCA were optimized and the optimal conditions were as follows: cycle number of ligation reaction, 12; ligation temperature, 58 °C; amplification temperature, 60 °C; and amplification time, 60 min. The specificity test that was performed using the optimized dpRCA conditions indicated that dpRCA-LFD was exclusively specific for the target alga. The tests with the genomic DNA of C. marina and the recombinant plasmid containing the ITS sequence of C. marina showed that the sensitivity of dpRCA-LFD was 100 times higher than that of conventional PCR. The detection limit (DL) for the genomic DNA was 8.3 × 10^-3 ng µL^-1 (8.3 × 10^-3 ng per reaction), and the DL for the recombinant plasmid DNA was 7.8 copies µL^-1 (7.8 copies per reaction). The practicality of the developed dpRCA-LFD was further validated by test with the spiked samples containing C. marina and field samples. The simulative test showed that the dpRCA-LFD has a DL of 10 cells mL^-1. The dpRCA-LFD could successfully recognize the target cells from the field samples. In summary, the dpRCA-LFD established in this study has advantages of good specificity, high sensitivity, and easily visible detection results, and therefore is promising for the analysis of C. marina in field samples.

Effects of marine harmful algal blooms on bivalve cellular immunity and infectious diseases: A review

Bivalves were long thought to be "symptomless carriers" of marine microalgal toxins to human seafood consumers. In the past three decades, science has come to recognize that harmful algae and their toxins can be harmful to grazers, including bivalves. Indeed, studies have shown conclusively that some microalgal toxins function as active grazing deterrents. When responding to marine Harmful Algal Bloom (HAB) events, bivalves can reject toxic cells to minimize toxin and bioactive extracellular compound (BEC) exposure, or ingest and digest cells, incorporating nutritional components and toxins. Several studies have reported modulation of bivalve hemocyte variables in response to HAB exposure. Hemocytes are specialized cells involved in many functions in bivalves, particularly in immunological defense mechanisms. Hemocytes protect tissues by engulfing or encapsulating living pathogens and repair tissue damage caused by injury, poisoning, and infections through inflammatory processes. The effects of HAB exposure observed on bivalve cellular immune variables have raised the question of possible effects on susceptibility to infectious disease. As science has described a previously unrecognized diversity in microalgal bioactive substances, and also found a growing list of infectious diseases in bivalves, episodic reports of interactions between harmful algae and disease in bivalves have been published. Only recently, studies directed to understand the physiological and metabolic bases of these interactions have been undertaken. This review compiles evidence from studies of harmful algal effects upon bivalve shellfish that establishes a framework for recent efforts to understand how harmful algae can alter infectious disease, and particularly the fundamental role of cellular immunity, in modulating these interactions. Experimental studies reviewed here indicate that HABs can modulate bivalve-pathogen interactions in various ways, either by increasing bivalve susceptibility to disease or conversely by lessening infection proliferation or transmission. Alteration of immune defense and global physiological distress caused by HAB exposure have been the most frequent reasons identified for these effects on disease. Only few studies, however, have addressed these effects so far and a general pattern cannot be established. Other mechanisms are likely involved but are under-studied thus far and will need more attention in the future. In particular, the inhibition of bivalve filtration by HABs and direct interaction between HABs and infectious agents in the seawater likely interfere with pathogen transmission. The study of these interactions in the field and at the population level also are needed to establish the ecological and economical significance of the effects of HABs upon bivalve diseases. A more thorough understanding of these interactions will assist in development of more effective management of bivalve shellfisheries and aquaculture in oceans subjected to increasing HAB and disease pressures.

The Southeast Alaska Tribal Ocean Research (SEATOR) Partnership: Addressing Data Gaps in Harmful Algal Bloom Monitoring and Shellfish Safety in Southeast Alaska

Many communities in Southeast Alaska harvest shellfish such as mussels and clams as an important part of a subsistence or traditional diet. Harmful algal blooms (HABs) of phytoplankton such as Alexandrium spp. produce toxins that can accumulate in shellfish tissues to concentrations that can pose a hazard for human health. Since 2013, several tribal governments and communities have pooled resources to form the Southeast Alaska Tribal Ocean Research (SEATOR) network, with the goal of minimizing risks to seafood harvest and enhancing food security. SEATOR monitors toxin concentrations in shellfish and collects and consolidates data on environmental variables that may be important predictors of toxin levels such as sea surface temperature and salinity. Data from SEATOR are publicly available and are encouraged to be used for the development and testing of predictive algorithms that could improve seafood risk assessment in Southeast Alaska. To date, more than 1700 shellfish samples have been analyzed for paralytic shellfish toxins (PSTs) in more than 20 locations, with potentially lethal concentrations observed in blue mussels (Mytilus trossulus) and butter clams (Saxidomus gigantea). Concentrations of PSTs exhibit seasonality in some species, and observations of Alexandrium are correlated to sea surface temperature and salinity; however, concentrations above the threshold of concern have been found in all months, and substantial variation in concentrations of PSTs remain unexplained.

Oil pipelines and food sovereignty: threat to health equity for Indigenous communities

Energy projects may profoundly impact Indigenous peoples. We consider effects of Canada's proposed Trans Mountain oil pipeline expansion on the health and food sovereignty of the Tsleil-Waututh Nation (TWN) through contamination and impeded access to uncontaminated traditional foods. Federal monitoring and TWN documentation show elevated shellfish biotoxin levels in TWN's traditional territory near the terminus where crude oil is piped. Although TWN restoration work has re-opened some shellfish-harvesting sites, pipeline expansion stands to increase health risk directly through rising bioaccumulating chemical toxins as well as through increased hazardous biotoxins. Climate change from increased fossil fuel use, expected via pipeline expansion, also threatens to increase algae blooms through higher temperature and nutrient loading. As the environmental impact assessment process failed to effectively consider these local health concerns in addition to larger impacts of climate change, new assessment is needed attending to linked issues of equity, sustainability and Indigenous food sovereignty.

Seasonal variations of phytoplankton assemblages in relation to environmental factors in Mediterranean coastal waters of Morocco, a focus on HABs species

Studies on phytoplankton and in particular Harmful Algal Blooms (HABs) species in southern Mediterranean waters are scarce. We performed from April 2008 to June 2009 weekly investigations on microphytoplankton community structure and abundance in two contrasted marine ecosystems located in the western Moroccan Mediterranean coast, M'diq Bay and Oued Laou Estuary. Simultaneously, we measured the main physico-chemical parameters. Globally, the two studied areas showed comparable values of the assessed abiotic environmental factors. Temperature and salinity followed seasonal variation with values ranging from 13.5 °C to 21.4 °C and 31 to 36.8, respectively. Average nutrient values in surface water ranged from 0.7 to 45.76 μM for dissolved inorganic nitrogen, 0.02-2.10 μM for PO₄ and 0.23-17.46 μM for SiO₄ in the study areas. A total of 92 taxa belonging to 8 taxonomic classes were found. The highest number of microphytoplankton abundance reached 1.2 × 10⁶ cells L^-1 with diatoms being the most abundant taxa. Factorial Discriminant Analysis (FDA) and Spearman correlation test showed a significant seasonal discrimination of dominant microphytoplankton species. These micro-organisms were associated with different environmental variables, in particular temperature and salinity. Numerous HABs species were encountered regularly along the year. Although Dinophysis species and Prorocentrum lima were present in both sites, no Lipophilic Shellfish Poisoning was detected for the analyzed bivalve mollusks. Domoic acid (DA), produced by toxic species of Pseudo-nitzschia was found with concentrations up to 18 µg DA g^-1 in the smooth clam Callista chione. Data showed that the observed persistent and dramatic Paralytic Shellfish Poisoning (PSP) intoxication of mollusks resulted probably of Gymnodinium catenatum proliferations in both studied areas. Contrary to C. chione, the cockle Achanthocardia tuberculatum showed a permanent and extremely high toxicity level during the 15 months survey with up to 7545 µg Equivalent Saxitoxin kg^-1 flesh (ten times higher than the sanitary threshold of 800 µg eqSTX Kg^-1flesh). The present work highlights for the first time the dynamic of microphytoplankton including HABs species and their associated toxin accumulation in the commercially exploited shellfish in the southern western Mediterranean waters of Morocco. Furthermore, the acquired data will help us to improve the monitoring of HABs species and related toxins in these coastal marine systems.