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

The underappreciated role of biotic factors in controlling the bloom ecology of potentially harmful microalgae in the Hudson-Raritan Bay

Despite widespread distribution of harmful algal blooms (HABs) and new and improved methods for detecting and quantifying them, no unifying ecological explanation has been found. Improved understanding depends upon local, ecological studies that include analysis of phytoplankton species data in relation to both abiotic and biotic parameters. Ecological network analysis was used to detect co-occurrence patterns among abiotic and biotic parameters in a long-term monitoring dataset (i.e., 2010-2021) from the eutrophic Hudson-Raritan Estuary (HRE) between the states of New York and New Jersey. The regular co-occurrence of potentially harmful bloom-forming species with companion species observed through microscopy was supported by the results of ecological network analysis, which showed that there were far more associations between HAB species and biotic parameters (∼95%) than abiotic parameters (∼5%). Temperature was the environmental variable that was most associated with HAB species throughout the estuary. The numerous network associations of HAB species with one another and with diatoms, dinoflagellates, and zooplankton highlight the complexity of planktonic food webs and interactions. Results also suggest that some taxa may play a central role in structuring the HRE plankton communities. These findings demonstrate that biotic associations play an underappreciated role in plankton structure and the value of examining the ecology of HAB species within the breadth of their biological communities. While network analysis does not fully explain and confirm complex associations among species, it does provide fresh insights and testable hypotheses to strengthen understanding and improve prediction.

Oxygen micro-nanobubbles for mitigating eutrophication induced sediment pollution in freshwater bodies

Sediment hypoxia is a growing problem and has negative ecological impacts on the aquatic ecosystem. Hypoxia can disturb the biodiversity and biogeochemical cycles of both phosphorus (P) and nitrogen (N) in water columns and sediments. Anthropogenic eutrophication and internal nutrient release from lakebed sediment accelerate hypoxia to form a dead zone. Thus, sediment hypoxia mitigation is necessary for ecological restoration and sustainable development. Conventional aeration practices to control sediment hypoxia, are not effective due to high cost, sediment disturbance and less sustainability. Owing to high solubility and stability, micro-nanobubbles (MNBs) offer several advantages over conventional water and wastewater treatment practices. Clay loaded oxygen micro-nanobubbles (OMNBs) can be delivered into deep water sediment by gravity and settling. Nanobubble technology provides a promising route for cost-effective oxygen delivery in large natural water systems. OMNBs also have the immense potential to manipulate biochemical pathways and microbial processes for remediating sediment pollution in natural waters. This review article aims to analyze recent trends employing OMNBs loaded materials to mitigate sediment hypoxia and subsequent pollution. The first part of the review highlights various minerals/materials used for the delivery of OMNBs into benthic sediments of freshwater bodies. Release of OMNBs at hypoxic sediment water interphase (SWI) can provide significant dissolved oxygen (DO) to remediate hypoxia induced sediment pollution Second part of the manuscript unveils the impacts of OMNBs on sediment pollutants (e.g., methylmercury, arsenic, and greenhouse gases) remediation and microbial processes for improved biogeochemical cycles. The review article will facilitate environmental engineers and ecologists to control sediment pollution along with ecological restoration.

Spatiotemporal transitions in Pseudo-nitzschia species assemblages and domoic acid along the Alaska coast

The toxic diatom genus Pseudo-nitzschia is distributed from equatorial to polar regions and is comprised of >57 species, some capable of producing the neurotoxin domoic acid (DA). In the Pacific Arctic Region spanning the Bering, Chukchi, and Beaufort seas, DA is recognized as an emerging human and ecosystem health threat, yet little is known about the composition and distribution of Pseudo-nitzschia species in these waters. This investigation characterized Pseudo-nitzschia assemblages in samples collected in 2018 during summer (August) and fall (October-November) surveys as part of the Distributed Biological Observatory and Arctic Observing Network, encompassing a broad geographic range (57.8° to 73.0°N, -138.9° to -169.9°W) and spanning temperature (-1.79 to 11.7°C) and salinity (22.9 to 32.9) gradients associated with distinct water masses. Species were identified using a genus-specific Automated Ribosomal Intergenic Spacer Analysis (ARISA). Seventeen amplicons were observed; seven corresponded to temperate, sub-polar, or polar Pseudo-nitzschia species based on parallel sequencing efforts (P. arctica, P. delicatissima, P. granii, P. obtusa, P. pungens, and two genotypes of P. seriata), and one represented Fragilariopsis oceanica. During summer, particulate DA (pDA; 4.0 to 130.0 ng L-1) was observed in the Bering Strait and Chukchi Sea where P. obtusa was prevalent. In fall, pDA (3.3 to 111.8 ng L-1) occurred along the Beaufort Sea shelf coincident with one P. seriata genotype, and south of the Bering Strait in association with the other P. seriata genotype. Taxa were correlated with latitude, longitude, temperature, salinity, pDA, and/or chlorophyll a, and each had a distinct distribution pattern. The observation of DA in association with different species, seasons, geographic regions, and water masses underscores the significant risk of Amnesic Shellfish Poisoning (ASP) and DA-poisoning in Alaska waters.

SoundToxins: A Research and Monitoring Partnership for Harmful Phytoplankton in Washington State

The more frequent occurrence of marine harmful algal blooms (HABs) and recent problems with newly-described toxins in Puget Sound have increased the risk for illness and have negatively impacted sustainable access to shellfish in Washington State. Marine toxins that affect safe shellfish harvest because of their impact on human health are the saxitoxins that cause paralytic shellfish poisoning (PSP), domoic acid that causes amnesic shellfish poisoning (ASP), diarrhetic shellfish toxins that cause diarrhetic shellfish poisoning (DSP) and the recent measurement of azaspiracids, known to cause azaspiracid poisoning (AZP), at low concentrations in Puget Sound shellfish. The flagellate, Heterosigma akashiwo, impacts the health and harvestability of aquacultured and wild salmon in Puget Sound. The more recently described flagellates that cause the illness or death of cultivated and wild shellfish, include Protoceratium reticulatum, known to produce yessotoxins, Akashiwo sanguinea and Phaeocystis globosa. This increased incidence of HABs, especially dinoflagellate HABs that are expected in increase with enhanced stratification linked to climate change, has necessitated the partnership of state regulatory programs with SoundToxins, the research, monitoring and early warning program for HABs in Puget Sound, that allows shellfish growers, Native tribes, environmental learning centers and citizens, to be the "eyes on the coast". This partnership enables safe harvest of wholesome seafood for consumption in the region and helps to describe unusual events that impact the health of oceans, wildlife and humans.

Seafood consumption during harmful algal blooms: The impact of information regarding safety and health

Harmful algal blooms (HABs) can cause massive fish kills all over the world. However, some commercially caught species are safe to eat. The fish safe for consumption are vastly different from the fish that wash up on shore. Prior research finds this difference in edibility is mostly unknown by consumers, and that the misperception of unhealthy and unsafe fish is the dominant paradigm. To date, there has been minimal research on the effect of disseminating this information regarding seafood health to consumers, and how consumption habits would change during a bloom. We implement a survey that presents respondents with information explaining the health and safety of certain commercially caught seafood during a HAB, specifically red grouper. It is a particularly popular, large, deep-sea fish. Our results suggest that respondents receiving this information are 34 percentage points more likely to say that they would be willing to consume red grouper during a bloom, relative to consumers who were not provided this added information. Prior knowledge of this information suggests long-term outreach programs may be more effective than last minute "point of sale" information campaigns. The results demonstrated the importance of correct knowledge and awareness regarding HABs, as it pertains to efforts to stabilize local economies dependent on seafood harvesting and consumption.

Seasonality of phytoplankton biomass and composition on the Cape Canaveral shelf of Florida: Role of shifts in climate and coastal watershed influences

Seasonal patterns of phytoplankton biomass and composition in the inner continental shelf off Cape Canaveral on the east coast of Florida were examined for a 6-year period (2013–2019). In situ water samples were collected and analyzed for chlorophyll a, phytoplankton biomass and composition, along with water quality parameters. Regional satellite data on chlorophyll a, and temperature was also obtained from NASA. Average chlorophyll a values over the study period ranged from 0.63 ± 0.03 μg L−1 in the summer to 2.55 ± 0.10 μg L−1 in the fall. Phytoplankton community composition also showed seasonal differences, with persistent dominance by picoplanktonic cyanobacteria in the summer, but mixed dominance by picocyanobacteria and dinoflagellates in the fall. Seasonal differences were attributed to a shift in predominant seasonal wind directions, which drive water along the coast from the north in the fall and winter, but from the south in the spring and summer, including eddies and upwelling from the Gulf Stream. Water masses moving along the Florida coast from the north are influenced by nutrient and phytoplankton-enriched inputs from estuaries along the north coast of Florida, explaining the higher phytoplankton biomass levels on the Cape Canaveral shelf in the fall and winter. Seasonal patterns observed in this study demonstrate the importance of allochthonous influences on phytoplankton biomass and composition, and highlight the potential sensitivity of phytoplankton communities to continuing cultural eutrophication and future climate changes, including the frequency and intensity of tropical storms, and alterations in discharges from land.

INVESTIGATING BLOOD LACTATE CONCENTRATION AS A PROGNOSTIC INDICATOR FOR BIRDS PRESENTING WITH BREVETOXICOSIS: 2020-2021

Large blooms of the dinoflagellate Karenia brevis cause annual harmful algal bloom events, or "red tides" on Florida's Gulf Coast. Each year, the Clinic for the Rehabilitation of Wildlife (CROW) is presented with hundreds of cases of aquatic birds that exhibit neurologic clinical signs due to brevetoxicosis. Double-crested cormorants (Phalacrocorax auratus) are the most common species seen, and typically present with a combination of ataxia, head tremors, knuckling, and/or lagophthalmos. Blood lactate levels are known to increase in mammals for a variety of reasons, including stress, hypoxia, sepsis, and trauma, but there is limited literature on blood lactate values in avian species. The objective of this study was to determine the prognostic value of blood lactate concentration on successful rehabilitation and release of birds presenting with clinical signs consistent with brevetoxicosis. Blood lactate levels were collected on intake, the morning after presentation and initial therapy, and prior to disposition (release or euthanasia) from 194 birds (including 98 cormorants) representing 17 species during the 2020-2021 red tide season. Overall, mean blood lactate at intake, the morning after intake, and predisposition was 2.9, 2.8, and 3.2 mmol/L, respectively, for released birds across all species (2.9, 2.9, and 3.2 mmol/L for released cormorants); 3.4, 3.4, and 6.5 mmol/L for birds that died (4.0, 3.5, and 7.9 mmol/L for cormorants that died); and 3.1, 3.5, and 4.7 mmol/L for birds that were euthanized (3.5, 4.7, and 4.9 mmol/L for cormorants that were euthanized). On average, birds that died or were euthanized had an elevated lactate at all time points as compared to those that were released, but these results were not statistically significant (P = 0.13). These results indicate that blood lactate levels do not appear to be useful as a prognostic indicator for successful release of birds, including double-crested cormorants, affected by brevetoxicosis.

Hindcasting harmful algal bloom risk due to land-based nutrient pollution in the Eastern Chinese coastal seas

Harmful algal blooms (HABs) have been increasing in frequency, areal extent and duration due to the large increase in nutrient inputs from land-based sources to coastal seas, and cause significant economic losses. In this study, we used the "watershed-coast-continuum" concept to explore the effects of land-based nutrient pollution on HAB development in the Eastern Chinese coastal seas (ECCS). Results from the coupling of a watershed nutrient model and a coast hydrodynamic-biogeochemical model show that between the 1980s and 2000s, the risk of diatom blooms and dinoflagellate blooms increased by 158% and 127%, respectively. The spatial expansion of HAB risk caused by dinoflagellates is larger than that of diatoms. The simulated suitability of the habitat for bloom of Aureococcus anophagefferens, a pico-plankton of non-diatom or dinoflagellate, in the Bohai Sea is consistent with observations spatially and temporally. To halt further nutrient accumulation in the ECCS, reductions of dissolved inorganic nitrogen (DIN) (16%) and dissolved inorganic phosphorus (DIP) (33%) loading are required. To improve the situation of distorted DIN:DIP ratios, even larger reductions of DIN are required, especially in the Bohai Sea. Our approach is a feasible way to predict the risk of HABs under the pressure of increasing anthropogenic nutrient pollution in coastal waters.

Prokaryotic Diversity and Dynamics during Dinoflagellate Bloom Decays in Coastal Tunisian Waters

(1) Background: Harmful algal blooms (HABs) can negatively impact marine ecosystems, but few studies have evaluated the microbial diversity associated with HABs and its potential role in the fates of these proliferations. (2) Methods: Marine prokaryotic diversity was investigated using high-throughput sequencing of the 16S rRNA gene during the bloom declines of two dinoflagellates detected in the summer of 2019 along the northern and southern Tunisian coasts (South Mediterranean Sea). The species Gymnodinium impudicum (Carthage, Tunis Gulf) and Alexandrium minutum (Sfax, Gabes Gulf) were identified using microscopy and molecular methods and were related to physicochemical factors and prokaryotic compositions. (3) Results: The abundance of G. impudicum decreased over time with decreasing phosphate concentrations. During the G. impudicum bloom decay, prokaryotes were predominated by the archaeal MGII group (Thalassarchaeaceae), Pelagibacterales (SAR11), Rhodobacterales, and Flavobacteriales. At Sfax, the abundance of A. minutum declined with decreasing phosphate concentrations and increasing pH. At the A. minutum peak, prokaryotic communities were largely dominated by anoxygenic phototrophic sulfur-oxidizing Chromatiaceae (Gammaproteobacteria) before decreasing at the end of the survey. Both the ubiquitous archaeal MGII group and Pelagibacterales were found in low proportions during the A. minutum decay. Contrary to the photosynthetic Cyanobacteria, the photo-autotrophic and -heterotrophic Rhodobacterales and Flavobacteriales contents remained stable during the dinoflagellate bloom decays. (4) Conclusions: These results indicated changes in prokaryotic community diversity during dinoflagellate bloom decays, suggesting different bacterial adaptations to environmental conditions, with stable core populations that were potentially able to degrade HABs.

Developmental exposure to domoic acid targets reticulospinal neurons and leads to aberrant myelination in the spinal cord

Harmful algal blooms (HABs) produce neurotoxins that affect human health. Developmental exposure of zebrafish embryos to the HAB toxin domoic acid (DomA) causes myelin defects, loss of reticulospinal neurons, and behavioral deficits. However, it is unclear whether DomA primarily targets myelin sheaths, leading to the loss of reticulospinal neurons, or reticulospinal neurons, causing myelin defects. Here, we show that while exposure to DomA at 2 dpf did not reduce the number of oligodendrocyte precursors prior to myelination, it led to fewer myelinating oligodendrocytes that produced shorter myelin sheaths and aberrantly wrapped neuron cell bodies. DomA-exposed larvae lacked Mauthner neurons prior to the onset of myelination, suggesting that axonal loss is not secondary to myelin defects. The loss of the axonal targets may have led oligodendrocytes to inappropriately myelinate neuronal cell bodies. Consistent with this, GANT61, a GLI1/2 inhibitor that reduces oligodendrocyte number, caused a reduction in aberrantly myelinated neuron cell bodies in DomA-exposed fish. Together, these results suggest that DomA initially alters reticulospinal neurons and the loss of axons causes aberrant myelination of nearby cell bodies. The identification of initial targets and perturbed cellular processes provides a mechanistic understanding of how DomA alters neurodevelopment, leading to structural and behavioral phenotypes.

Evaluating red tide effects on the West Florida Shelf using a spatiotemporal ecosystem modeling framework

The West Florida Shelf (WFS), located in the eastern Gulf of Mexico, fosters high species richness and supports highly valuable fisheries. However, red tide events occur regularly that can impact fisheries resources as well as ecosystem state, functioning, and derived services. Therefore, it is important to evaluate and quantify the spatiotemporal impacts of red tides to improve population assessments, mitigate potential negative effects through management, and better understand disturbances to support an ecosystem-based management framework. To model red tide effects on the marine community, we used Ecospace, the spatiotemporal module of the ecosystem modeling framework Ecopath with Ecosim. The inclusion of both lethal and sublethal response functions to red tide and a comprehensive calibration procedure allowed to systematically evaluate red tide effects and increased the robustness of the model and management applicability. Our results suggest severe red tide impacts have occurred on the WFS at the ecosystem, community, and population levels in terms of biomass, catch, and productivity. Sublethal and indirect food-web effects of red tide triggered compensatory responses such as avoidance behavior and release from predation and/or competition.. This study represents a step forward to operationalize spatiotemporal ecosystem models for management purposes that may increase the ability of fisheries managers to respond more effectively and be more proactive to episodic mortality events, such as those caused by red tides.

Interspecific competition between the bloom-causing dinoflagellates Hetrocapsa bohaiensis and the local species Chlorella pyrenoidosa

Harmful algal blooms caused by Heterocapsa bohaiensis have broken out in aquaculture areas near Liaodong Bay, China, since 2012, resulting in mass mortality of Eriocheir sinensis larvae and substantial economic loss. Chlorella pyrenoidosa is a local phytoplankton species that is found in aquaculture ponds. However, the reason why H. bohaiensis dominated and proliferated in the phytoplankton community remains unknown. Previous studies have revealed the toxicity and hemolytic activity of H. bohaiensis. It is suspected that the out-competition of H. bohaiensis to C. pyrenoidosa was associated with toxicity. Filtrate and bi-algal cultures were investigated to determine the interspecific competition between H. bohaiensis and C. pyrenoidosa in this study. Filtrate experiments revealed that H. bohaiensis showed no toxin allelopathy in C. pyrenoidosa. However, the C. pyrenoidosa filtrates had significant allelopathic effects on the growth of H. bohaiensis. The bi-algal culture experiments and the simulation showed that the dominant species were dependent on the initial cell density ratios of the species and nutrient ratios. Therefore, H. bohaiensis achieved competitive advantage through exploitation competition but not allelopathy. The results contribute to the reasons for the occurrence of H. bohaiensis blooms in a further study.

A combined approach detected novel species diversity and distribution of dinoflagellate cysts in the Yellow Sea, China

Resting cysts of dinoflagellates seed harmful algal blooms (HABs) and their geographic expansion, which makes it fundamentally important to obtain comprehensive inventories of dinoflagellate resting cysts in HABs-prone regions. The Yellow Sea (YS) of China has observed numerous outbreaks of dinoflagellate HABs with some novel species recorded recently indicating an underestimated HABs-causing species diversity. We report our investigation of dinoflagellate cysts of YS via an approach combining metabarcoding sequencing and single-cyst morpho-molecular identification, which identified many novel cyst species and a significant controlling effect of the Yellow Sea Cold Water Mass on cyst composition. The metabarcoding and single cyst-based sequencing detected 11 cyst species never being unambiguously reported in China, 10 never reported as cyst producers, and 3 HABs-causing species never reported from YS. Our detections of many potentially toxic or HABs-causative, particularly novel, cysts and distribution pattern provide important insights into the risks and ecology of dinoflagellate HABs.

Effects of nitrate and ammonium on assimilation of nitric oxide by Heterosigma akashiwo

The harmful alga Heterosigma akashiwo possesses a hybrid nitrate reductase (NR) enzyme, NR2-2/2HbN, which has the potential to convert NO to nitrate for assimilation into biomass. In previous research, NR transcription in H. akashiwo was induced by nitrate while NR activity was inhibited by ammonium. Here, the capacity of H. akashiwo to use NO in the presence of nitrate and/or ammonium was investigated to understand the regulation of NO assimilation. Continuous cultures of H. akashiwo were acclimated to growth on nitrate, ammonium, or a mixture of both. Aliquots from these cultures were spiked with ¹⁵N-labeled NO. The expression of genes involved in nitrogen assimilation was evaluated, as well as nitrate reductase activity and assimilation of ¹⁵N-labeled nitrogen into algal biomass. Results showed that NO induced expression and activity of NR, and upregulated expression of GOGAT regardless of the presence of other inorganic nitrogen sources, while GS expression decreased over time. Furthermore, ¹⁵NO uptake and assimilation was significantly higher in cultures acclimated for growth on ammonium compared to cultures acclimated for growth on nitrate alone. Assimilation of NO may provide H. akashiwo with a competitive advantage in N-poor environments or areas with elevated NO.

Metabarcoding reveals high genetic diversity of harmful algae in the coastal waters of Texas, Gulf of Mexico

Environmental-DNA (eDNA) for metabarcoding is a rapid and effective means to investigate microplankton community composition and species diversity. The objective of this study was to examine the genetic diversity of the phytoplankton community in the Gulf of Mexico, with particular emphasis on harmful algal bloom species. Samples were collected at stations along the coast of Texas in September-October 2017 that were inundated by low salinity waters in the aftermath of Hurricane Harvey. Metabarcodes were generated from the eDNA targeting both the V4 and V8-V9 regions of the 18S rDNA gene. Evaluation of the metabarcodes revealed an unexpectedly high number of harmful algal species during this short period, including five that had not been documented in this region previously. A total of 36 harmful algal species could be differentiated based on V4 and V8-V9 metabarcode markers. Using a phylogenetic approach, the taxonomic resolution of each marker differed and not all species could be differentiated using solely one marker. The V4 region resolved species within some genera (e.g., Heterocapsa), while the V8-V9 marker was necessary to resolve species within other genera (e.g., Chattonella). In other cases, species differentiation within a genus required a combination of both markers (e.g., Prorocentrum, Karenia), or another marker will be needed to resolve all species (e.g., Alexandrium, Dinophysis). We conclude that no single marker can delineate all species, so it is recommended HAB monitoring programs use more than one marker. Overall, the observed diversity of HAB species along the Texas coast using metabarcoding exceeded reports from other parts of the world.

Brown tides linked to the unique nutrient profile in coastal waters of Qinhuangdao, China

Brown tides caused by the pelagophyte Aureococcus anophagefferens have frequently occurred in the Bohai Sea since 2009 and have led to a dramatic collapse of the local scallop culture. To determine why brown tides occurred in the Bohai Sea rather than in other eutrophic coastal waters of China, phytoplankton communities and nutrients were evaluated and nutrient addition experiments were conducted in the Qinhuangdao coastal area. The concentration of dissolved organic nitrogen (DON) was nearly five times higher than that of dissolved inorganic nitrogen (DIN) during brown tides. High levels of phytoplankton biomass and nutrients were observed in the inshore waters, and the patterns of different nutrients were heterogeneous, which could be due to the uneven distribution of pelagophytes and non-brown tide phytoplankton populations (NBTP). The nutrient enrichment results indicated that the growth of the phytoplankton community was nitrogen-limited. Enrichment of DON, especially urea, could promote the growth of pelagophytes during the development stages of the brown tide. In brief, the results of this study imply that the unique nutrient profile (rich in DON but deficient in DIN) could support the outbreak of brown tides in the inshore waters of Qinhuangdao.

Marked shifts of harmful algal blooms in the Bohai Sea linked with combined impacts of environmental changes

The Bohai Sea, a semi-enclosed inland sea in China and an important mariculture region, has experienced extensive harmful algal blooms (HABs) and their negative impacts for several decades. To investigate the changes of HABs and their potential drivers over time and space, a dataset of 230 HAB events (1952-2017), along with corresponding environmental data (1990-2017) was compiled. The frequency of HAB events in the Bohai Sea has increased over time but plateaued in the last decade, and our analysis showed that history of HABs in the Bohai Sea could be categorized into three periods based on their frequency, scale, and HAB-forming species. The seasonal window of HAB events has started earlier and lasted longer, and the main hotspot has moved from Bohai Bay to coastal waters of Qinhuangdao over time. There were marked shifts in the representative HAB-forming microalgae, from dinoflagellates in the first period (before 2000) to haptophytes in the second period (2000-2009), and pelagophytes in the third period (2009 onwards). These community changes are accompanied by a trend toward diversification of HAB-forming microalgae, decrease in cell-size, and increase in negative impacts. Statistical analyses indicate that long-term changes in HABs in the Bohai Sea are linked with the combined effects of climate change, eutrophication and mariculture development. The results of the present study require to refine future monitoring programs, develop adaptive management strategies and predictive models for HABs in the Bohai Sea.

Easy detection of Prorocentrum donghaiense by polymerase chain reaction-nucleic acid chromatography strip

In recent years, Prorocentrum donghaiense, as a dominant species, has ranked first in terms of cumulative number and area of algal blooms in the East China Sea. In this study, the D1-D2 region of the large ribosomal subunit of P. donghaiense was used as the target gene, and specific primers DH-FP/DH-RP were designed according to the species-specific region of the target gene. An easy, sensitive and visual detection method refered to as polymerase chain reaction-nucleic acid chromatography strip (PCR-NACS) was established for P. donghaiense. The optimized parameters of the PCR amplification system are as follows: primer concentration, 0.15 μM; annealing temperature, 62 °C; and Mg²⁺ concentration, 1.5 mM. The specificity test showed that PCR-NACS was exlusively specific for the detection of the target algae. The sensitivity test show that the lowest detection limit (LDL) of PCR-NACS was 2.7 × 10^-2 ng·μL^-1 for genomic DNA and 3.58 × 10² copies·μL^-1 for plasmid DNA, respectively. The tests using both genomic DNA and plasmid DNA as templates showed that the sensitivity of PCR-NACS was 10 times higher than that of ordinary PCR. The stability test showed that the interfering algal species did not affect the detection of the target algae by PCR-NACS. In addition, the test with simulated natural samples containing target algae showed that the LDL of PCR-NACS could reach 1.27 × 10¹ cells·mL^-1. In summary, the PCR-NACS established in this study may provide a new method for easy identification of P. donghaiense in natural water samples.

A massive bloom of Karenia species (Dinophyceae) off the Kamchatka coast, Russia, in the fall of 2020

In the fall of 2020, a long-lasting and massive harmful algal bloom (HAB) with extensive fields of yellow sea foam was observed in relatively cold waters (7-13 °C) off the coasts of the Kamchatka Peninsula, Russia. According to the estimates based on bio-optical parameters in satellite imagery, the Kamchatka bloom 2020 lasted for two months and covered a vast area of more than 300 × 100 km. An abundance of dead fish and invertebrates, including sea urchins, sea anemones, chitons, cephalopods, bivalves were found on shore during the bloom. Animals suffered almost 100% mortality within a depth range between 5 and 20 m. To identify the causative microalgal species, light and scanning electron microscopy, Raman spectroscopy, and molecular phylogenetic approaches were used. The HAB area was estimated by the spectral analysis of satellite-derived imagery. The causative organisms were unarmored dinoflagellates of Karenia species. Their density and biomass reached 100-620 cells·mL^-1 and 1300-7700 mg·m^-3, respectively, which accounted for 31-99% of the total cell density and 82-99% of the total phytoplankton biomass in late September to mid-October. The dominant species was Karenia selliformis, and the other co-occurring kareniacean species were K. cf. cristata, K. mikimotoi, K. papilionacea, K. longicanalis, and two unidentified morphotypes of Karenia spp. The molecular phylogeny inferred from LSU rDNA and ITS region showed that K. selliformis from Kamchatka in 2020 belonged to the cold-water group I and was identical to K. selliformis strains from Hokkaido, Japan, identified in 2021. This is the first HAB event caused by K. selliformis recorded from Russian coastal waters.

Alexandrium on the Alaskan Beaufort Sea shelf: Impact of upwelling in a warming Arctic

The harmful algal genus Alexandrium has characteristically been found in temperate and subtropical regions; however recent evidence suggests global warming may be expanding its range into high latitude waters. Alexandrium cysts have previously been documented in the Chukchi Sea and we hypothesize that Alexandrium may be expanding further into the Arctic due to distribution by the Beaufort shelfbreak jet. Here we document the presence of Alexandrium catenella along the Alaskan Beaufort Sea shelf, marking an expansion of its known range. The observations of A. catenella were made using three different methods: FlowCAM imaging, 18S eukaryotic sequencing, and real-time quantitative PCR. Four occupations of a shelf/slope transect spanned the evolution of a strong wind-driven upwelling event over a 5-day period. A nearby mooring provided the physical context for the event, revealing that enhanced easterly winds reversed the Beaufort shelfbreak jet to the west and induced upwelling of colder, denser water onto the outer shelf. A. catenella sequences dominated the surface phytoplankton community at the onset of the upwelling event. This signal vanished during and after the event, likely due to a combination of alongstream advection, cross-stream advection, and wind mixing. These results suggest contrasting physical processes that are both subject to global warming amplification, delivery of warm waters via the Beaufort shelfbreak jet and upwelling, may control the proliferation of this potential harmful alga into the Arctic.

Understanding the temporal dynamics of estimated environmental niche hypervolumes for marine fishes

Understanding how species respond to the environment is essential in ecology, evolution, and conservation. Abiotic factors can influence species responses and the multi-dimensional space of abiotic factors that allows a species to grow represents the environmental niche. While niches are often assumed to be constant and robust, they are most likely changing over time and estimation can be influenced by population biology, sampling intensity, and computation methodology. Here, we used a 12-year time series of survey data to fit annual ecological niche models (ENMs) for 10 marine fish species by using two regression and two machine learning algorithms to evaluate the variation and differentiation of environmental niches. Fitted ENMs were used to develop multi-dimensional annual and pooled hypervolumes that were evaluated over time and across ENM algorithms, species, and years by computing volume, distance, and dissimilarity metrics for each annual estimated niche. We then investigated potential drivers of estimated hypervolume dynamics including species abundance, species occurrence, sampling effort, salinity, red tides severity, and algorithm. Overall, our results revealed that estimated niches varied over time and across ENM, species, and algorithms. Niche estimation was influenced over time by multiple factors suggesting high complexity on niche dynamics interpretation. Species with high occurrence tended to have a closer representation of the pooled niche and years with higher abundance tended to produce niche expansion. ENM algorithm, sampling effort, seawater salinity, and red tides explained the deviations from the pooled niche. Greater sampling effort led to more comprehensive and complete estimates of species niches. High red tides severity triggered niche contraction. Our results emphasize the predictable effects of population, sampling, and environment on species niche estimation and interpretation, and that each should be considered when performing and interpreting ecological niche analyses. Our niche analysis approach may contribute to effectively quantifying and assessing niche dynamics.

Addition of carbon sources and nutrient salts can inhibit gangue acidification by changing microbial community structure

Acidic pollution from gangue oxidation has become a primary environmental problem in coal mining areas in China. The use of microorganisms to remediate acidic pollution in coal gangue piles has been indicated to be effective, but environmental differences and carbon sources in different mining areas have become important factors restricting microbial activity. Instead of the addition of new functional bacteria to gangue piles, carbon sources and nutrient salts were added to recently discharged gangue to enhance the activity of beneficial bacteria in the indigenous microbial community. The changes in pH and electrical conductivity (EC) of the gangue leachate as well as the composition and abundance of the functional microbial community on the surface of the gangue were analyzed by leaching simulation experiments and 16S rRNA sequencing. The results showed that the addition of a carbon source maintained the pH of the gangue leachate at 6.31~6.65 in 14 d, which was significantly higher than that of the control group, but the pH of the leachate decreased significantly after the addition of the carbon source was stopped. The most effective treatment is adding a low concentration of nutrient salt (20% concentration) and sodium lactate (0.02 g/L) to the gangue first, and then adding sodium lactate (0.1 mg/L) every 7 days. The addition of carbon sources and nutrient salts changed the microbial community composition on the surface of the gangue, and the species diversity index decreased. The dominant genera in the experimental group were Listeria, Arthrobacter, and Enterococcus. The functional gene types in the experimental and control groups were almost the same, but their relative abundance changed. The abundance of functional genes related to the sulfur cycle increased substantially in the experimental group, and the abundance of genes involved in the nitrogen and carbon cycles also increased, albeit to different degrees.

Review of harmful algal bloom effects on birds with implications for avian wildlife in the Chesapeake Bay region

The Chesapeake Bay, along the mid-Atlantic coast of North America, is the largest estuary in the United States and provides critical habitat for wildlife. In contrast to point and non-point source release of pesticides, metals, and industrial, personal care and household use chemicals on biota in this watershed, there has only been scant attention to potential exposure and effects of algal toxins on wildlife in the Chesapeake Bay region. As background, we first review the scientific literature on algal toxins and harmful algal bloom (HAB) events in various regions of the world that principally affected birds, and to a lesser degree other wildlife. To examine the situation for the Chesapeake, we compiled information from government reports and databases summarizing wildlife mortality events for 2000 through 2020 that were associated with potentially toxic algae and HAB events. Summary findings indicate that there have been few wildlife mortality incidents definitively linked to HABs, other mortality events that were suspected to be related to HABs, and more instances in which HABs may have indirectly contributed to or occurred coincident with wildlife mortality. The dominant toxins found in the Chesapeake Bay drainage that could potentially affect wildlife are microcystins, with concentrations in water approaching or exceeding human-based thresholds for ceasing recreational use and drinking water at a number of locations. As an increasing trend in HAB events in the U.S. and in the Chesapeake Bay have been reported, additional information on HAB toxin exposure routes, comparative sensitivity among species, consequences of sublethal exposure, and better diagnostic and risk criteria would greatly assist in predicting algal toxin hazard and risks to wildlife.

Treatment of the red tide dinoflagellate Karenia brevis and brevetoxins using USEPA-registered algaecides

The effectiveness of USEPA-registered algaecides for managing algae in lakes and reservoirs has been extensively evaluated in laboratory studies, mesocosm studies and in situ treatment. However, the use of these algaecides in marine environments for the management of dinoflagellates and associated toxins remains largely unknown. Karenia brevis is a toxic dinoflagellate that causes red tides in the Gulf of Mexico. In this study, we investigated the efficacy of six USEPA-registered algaecides, three copper-based and three peroxide-based, on treating toxic K. brevis with a natural bloom density (1.79 × 10⁷ cells/L). Our results indicate that the application of as low as 0.31-0.34 mg Cu/L led to a significant decrease of K. brevis cells within 24 h after treatment, while peroxide-based algaecides required a relatively higher concentration for the effective removal of K. brevis cells (4.89-7.08 mg H₂O₂/L), but still lower than maximum label rate. Total brevetoxin levels 72 h after treatment revealed that 1.00 mg Cu/L for Algimycin® PWF, 6.48 mg H₂O₂/L for PAK® 27 and 7.08 mg H₂O₂/L for Oximycin® P5 had the greatest impact on decreasing toxin levels. The correlation analysis showed that brevetoxin reduction rate was significantly positively related with the peroxide-based algaecide exposure concentration, which is caused by the oxidation of hydroxyl radicals produced by hydrogen peroxide. The degradation dynamics of the three peroxide-based algaecides revealed that salinity, microorganisms and organic matter (≥ 0.2 μm) impact the stability of hydrogen peroxide, and Oximycin® P5 showed the highest stability among tested peroxide-based algaecides with a degradation rate of 0.467 mg/d in natural seawater. Hence, our laboratory work provided new insights into potential emergency treatment methods for immediate mitigation of K. brevis and brevetoxins. More work on the fate and persistence of algaecide active ingredients and phycotoxins, effects of site characteristics, and pilot studies on marine non-targets are still needed before safe application of this method for HABs in marine systems.

Storm-induced coastward expansion of Margalefidinium polykrikoides bloom in Chesapeake Bay

An unusual coastward expansion of the toxic dinoflagellate species Margalefidinium polykrikoides was observed in 2020 summer after a tropical storm passing Chesapeake Bay. Such coastward expansion was only recorded in 2007. A newly developed coupled Lagrangian particle tracking and harmful algal bloom model driven by environmental variables was used to investigate the underlying mechanisms and successfully reproduced the expansion patterns. Persistent pre-storm southerly winds favored the delivery of bloom source water originated inside the bay to the coast. Storm-induced strong upwelling of denser subsurface water interacted with the after-storm outflow plume (steered southward as the storm's impacts waned), forming a transport barrier to accumulate algae and delineate the coastwide bloom extent. Algal diel vertical migrations and transport barrier enable algae to stay in the nearshore regions. The storm-induced coastward expansion of M. polykrikoides might increase future bloom possibility in the coastal area.

Assessing a model of Pacific Northwest harmful algal bloom transport as a decision-support tool

In the Pacific Northwest, blooms of the diatom Pseudo-nitzschia (PN) sometimes produce domoic acid, a neurotoxin that causes amnesic shellfish poisoning, leading to a Harmful Algal Bloom (HAB) event. The Pacific Northwest (PNW) HAB Bulletin project, a partnership between academic, government, and tribal stakeholders, uses a combination of beach and offshore monitoring data and ocean forecast modeling to better understand the formation, evolution, and transport of HABs in this region. This project produces periodic Bulletins to inform local stakeholders of current and forecasted conditions. The goal of this study was to help improve how the forecast model is used in the Bulletin's preparation through a retrospective particle-tracking experiment. Using past observations of beach PN cell counts, events were identified that likely originated in the Juan de Fuca eddy, a known PN hotspot, and then particle tracks were used in the model to simulate these events. A variety of "beaching definitions" were tested, based on both water depth and distance offshore, to define when a particle in the model was close enough to the coast that it was likely to correspond to cells appearing in the intertidal zone and in shellfish diets, as well as a variety of observed PN cell thresholds to determine what cell count should be used to describe an event that would warrant further action. The skill of these criteria was assessed by determining the fraction of true positives, true negatives, false positives, and false negatives within the model in comparison with observations, as well as a variety of derived model performance metrics. This analysis suggested that for our stakeholders' purposes, the most useful beaching definition is the 30 m isobath and the most useful PN cell threshold for coincident field-based sample PN density estimates is 10,000 PN cells/L. Lastly, the performance of a medium-resolution (1.5 km horizontal resolution) version of the model was compared with that of a high-resolution (0.5 km horizontal resolution) version, the latter currently used in forecasting for the PNW HAB Bulletin project. This analysis includes a direct comparison of the two model resolutions for one overlapping year (2017). These results suggested that a narrower, more realistic beaching definition is most useful in a high-resolution model, while a wider beaching definition is more appropriate in a lower resolution model like the medium-resolution version used in this analysis. Overall, this analysis demonstrated the importance of incorporating stakeholder needs into the statistical approach in order to generate the most effective decision-support information from oceanographic modeling.

Increase in records of toxic phytoplankton and associated toxins in water samples in the Patagonian Shelf (Argentina) over 40 years of field surveys

Historical records (1980-2018) of potentially toxic phytoplankton and phycotoxins on the Argentine Continental Shelf (35°S-56.5°S) and adjacent ocean waters were systematically reviewed from scientific literature to assess their abundance and diversity over spatial and temporal scales. Records increased from 124 in the period 1980-1992 to 638 in 2006-2018, and the scanned area expanded from coastal to offshore waters including the shelf-break front. Alexandrium was the most reported genus (54%) during 1980-1992 and Pseudo-nitzschia (52%) during 1993-2005. By 2006-2018, a higher diversity was documented: Alexandrium (20%), Dinophysis (32%), Pseudo-nitzschia (31%), and the most recently described potentially toxic dinoflagellates of the family Amphidomataceae (8%). Likewise, a wider spectrum of phycotoxins was documented in the last decade, with lipophilic (LSTs) and paralytic shellfish toxins (PSTs) as the most recorded. Increased records are related to intensified monitoring, more detailed taxonomic analyses and more sensitive chemical techniques for marine biotoxin detection. This quantitative assessment brings light to the widespread occurrence of HABs along contrasting areas of the Patagonian Shelf and sets the basis for ecosystem risk evaluation. Moreover, comparison of toxic phytoplankton reported in the SW Atlantic with those in similar temperate seas in the North Atlantic and the Pacific Ocean, disclose ocean basin differences in strain toxicity of A. ostenfeldii, D. tripos and Azadinium species.

Low Levels of Contaminants Stimulate Harmful Algal Organisms and Enrich Their Toxins

A widespread increase in intense phytoplankton blooms has been noted in lakes worldwide since the 1980s, with the summertime peak intensity amplifying in most lakes. Such blooms cause annual economic losses of multibillion USD and present a major challenge, affecting 11 out of the 17 United Nations Sustainable Development Goals. Here, we evaluate recent scientific evidence for hormetic effects of emerging contaminants and regulated pollutants on Microcystis sp., the most notorious cyanobacteria forming harmful algal blooms and releasing phycotoxins in eutrophic freshwater systems. This new evidence leads to the conclusion that pollution is linked to algal bloom intensification. Concentrations of contaminants that are considerably smaller than the threshold for toxicity enhance the formation of harmful colonies, increase the production of phycotoxins and their release into the environment, and lower the efficacy of algaecides to control algal blooms. The low-dose enhancement of microcystins is attributed to the up-regulation of a protein controlling microcystin release (McyH) and various microcystin synthetases in tandem with the global nitrogen regulator Ycf28, nonribosomal peptide synthetases, and several ATP-binding cassette transport proteins. Given that colony formation and phycotoxin production and release are enhanced by contaminant concentrations smaller than the toxicological threshold and are widely occurring in the environment, the effect of contaminants on harmful algal blooms is more prevalent than previously thought. Climate change and nutrient enrichment, known mechanisms underpinning algal blooms, are thus joined by low-level pollutants as another causal mechanism.

Removal of harmful algae in natural water by semiconductor photocatalysis- A critical review

Harmful Algal Blooms (HABs) have turned out to be a global occurrence owing to the detrimental phenomenon like eutrophication and global climate change caused by human activities. This newly emergent threat imposes a severe hazardous to public health, ecosystems and fishery-based economies. Rapid and exponential growth of certain delirious and toxic algal species shall be held causative to the formation of HABs. The potential disadvantages they pose, make it necessary the identification of efficient treatment methodologies. Photocatalysis has been identified as the most promising solution amongst all the identified and investigated methods, for the environmental and economic benefits beheld. Different treatment methodologies were evaluated and light has been thrown on the advantages beheld by photocatalysis over the other methods. Focus has been given to the different photocatalysts that have been so far put to use towards photocatalytic disinfection of HABs and algal toxins. This present study provides useful information on the application of the traditional and photocatalysis process for removal of HABs in water bodies. Moreover, the results revealed that photocatalysis method could cause potent inhibitory effect on growth of algae species and disrupted algal cells membranes to some extent. Finally, the conventional treatment techniques have been recognized to be insufficient for removal of HABs. However, the photocatalyst technology have been utilized mostly for the mineralization and neutralization of the algal pollutants without any harmful secondary pollutants.

Slicing the Pie: Interpreting harmful algal blooms one pie chart at a time

The Earth's oceans are home to a diverse array of life, from large marine mammals to microscopic organisms. Among the most important are the marine phytoplankton, which comprise the basis of marine food webs, and also produce a large percentage of the Earth's oxygen through photosynthesis. Although the vast majority of phytoplankton are essential to ocean health, several dozen species produce potent toxins, and can form what are called Harmful Algal Blooms (HABs). This activity focuses on the importance of HABs, as well as the types of data scientists collect to understand blooms. In the classroom exercises, students will calculate the proportional abundance (% contribution) of five HAB species present in water samples, and use these data to create pie graphs to depict species composition. Students will then compare these results with levels of HAB toxins in water samples collected over the same time period. Thought questions challenge students to develop hypotheses regarding how changes in the HAB community may relate to observed trends in toxin concentrations. This activity was successfully taught to visually impaired students who were able to complete the pie charts and answer the thought questions.

Mechanism of the allelopathic effect of macroalgae Gracilaria bailiniae on Nitzschia closterium

With the rapid development of the seaweed industry in China, the scale and production of its commercial seaweed are ranked among the most significant worldwide. Consequently, the control of algal blooms, especially fouling diatoms, during macroalgae industrialisation is an important issue. Many diatom bloom studies have focused on physical and chemical controls, with limited economic and eco-friendly biological controls reported. In our study, Gracilaria bailiniae fresh thalli and aqueous extract profoundly suppressed Nitzschia closterium growth (50% inhibition concentration of the fourth day (IC_50-4 day) was 0.667 × 10^-3 g·mL^-1 and 3.889 × 10^-3 g·mL^-1, respectively). The cellular morphology changes of N. closterium exposed to the G. bailiniae aqueous extract were severe atrophies and plasmolysis and dissolution of endocellular structures. To explore more potential allelochemicals to control N. closterium, the intracellular compounds of G. bailiniae were detected and screened. Three organic acids (citrate, hydroxyethanesulfonic acid (HA) and taurine) had allelopathic potential against N. closterium. Our results showed that citrate and HA markedly suppressed N. closterium (IC_50-4 day: 1.035 mM and 1.151 mM, respectively); however, taurine poorly suppressed N. closterium (IC_50-4 day: 2.500 mM). Therefore, HA is one of the main allelopathic compounds in G. bailiniae. Further, the allelopathic mechanism of HA against the N. closterium photosynthetic system broke its photosynthetic apparatus (oxygen-evolving complex, reaction centres, the effective antenna size and the donor side of photosystem II) and hindered electron transport. The experimental results provide a new and eco-friendly strategy to control diatom blooms.

Karenia brevis bloom patterns on the west Florida shelf between 2003 and 2019: Integration of field and satellite observations

Harmful algal blooms of the toxic dinoflagellate Karenia brevis occur almost annually on the West Florida Shelf (WFS) of the eastern Gulf of Mexico. To date, however, comprehensive assessments of K. brevis bloom spatial extent and temporal occurrence are lacking due to limitations in the two primary bloom monitoring techniques: microscopy evaluation of field-collected water samples and satellite remote sensing of ocean color. This is despite community efforts in expanding sampling coverage statewide and developing remote sensing algorithms to interpret color changes of surface waters. In this work, an approach is developed to combine the strengths of both techniques to estimate mean bloom occurrence frequency and bloom intensity as well as bloom extent at weekly, bi-weekly, monthly, and annual intervals between 2003 and 2019. Here, due to technical constraints on ocean color remote sensing, a bloom is defined as waters with K. brevis concentrations greater than 1.5 × 10⁵ cells L^-1. While microscopy examination of surface water samples provides K. brevis cell concentrations to help delineate bloom locations from Moderate Resolution Imaging Spectrometer on Aqua (MODIS/A) images, the imagery provides far more synoptic and frequent observations to make the bloom characterization statistically meaningful. Such derived bloom statistics often show bloom patterns that are not always known previously or at the time of the event, and in some years, they also differ from those determined from microscopic taxonomy data alone. For example, in terms of bloom size, two major bloom periods are observed in 2005 - 2007 and 2014 - 2018, respectively, when annual cumulative bloom size exceeded ∼50,000 km². While preliminary in nature, the approach and results from this work may represent a first step to integrate water sample analysis and satellite remote sensing towards an improved characterization of K. brevis blooms on the WFS.

Variability patterns and phenology of harmful phytoplankton blooms off southern Portugal: Looking for region-specific environmental drivers and predictors

Harmful algal blooms (HABs) negatively impact coastal ecosystems, fisheries, and human health, and their prediction has become imperative for effective coastal management. This study aimed to evaluate spatial-temporal variability patterns and phenology for key toxigenic phytoplankton species off southern Portugal, during a 6-year period, and identify region-specific environmental drivers and predictors. Total abundance of species responsible for amnesic shellfish poisoning (Pseudo-nitzschia spp.), diarrhetic shellfish poisoning (Dinophysis spp.), and paralytic shellfish poisoning (G. catenatum) were retrieved, from the National Bivalve Mollusk Monitoring System public database. Contemporaneous environmental variables were acquired from satellite remote sensing, model-derived data, and in situ observations, and generalized additive models (GAMs) were used to explore the functional relationships between HABs and environmental variables and identify region-specific predictors. Pseudo-nitzschia spp. showed a bimodal annual cycle for most coastal production areas, with spring and summer maxima, reflecting the increase in light intensity during the mixed layer shoaling stage, and the later stimulatory effects of upwelling events, with a higher bloom frequency over coastal areas subjected to stronger upwelling intensity. Dinophysis spp. exhibited a unimodal annual cycle, with spring/summer maxima associated with stratified conditions, that typically promote dinoflagellates. Dinophysis spp. blooms were delayed with respect to Pseudo-nitzschia spp. spring blooms, and followed by Pseudo-nitzschia spp. summer blooms, probably reflecting upwelling-relaxation cycles. G. catenatum occurred occasionally, namely in areas more influenced by river discharges, under weaker upwelling. Statistical-empirical models (GAMs) explained 7-8%, and 21-54% of the variability in Pseudo-nitzschia spp. and Dinophysis spp., respectively. Overall, a set of four easily accessible environmental variables, surface photosynthetically available radiation, mixed layer depth, sea surface temperature, and chlorophyll-a concentration, emerged as the most influential predictors. Additionally, over the coastal production areas along the south coast, river discharges exerted minor negative effects on both HAB groups. Despite evidence supporting the role of upwelling intensity as an environmental driver of Pseudo-nitzschia spp., it was not identified as a relevant model predictor. Future model developments, such as the inclusion of additional environmental variables, and the implementation of species- and period-specific, and hybrid modelling approaches, may further support HAB operational forecasting and managing over complex coastal domains.

Metaproteomics reveals unique metabolic niches of dominant bacterial groups in response to rapid regime shifts during a mixed dinoflagellate bloom

The dynamics of bacterial composition and metabolic activity during a distinct phytoplankton bloom have been reported. However, there is limited information on the bacterial community response to drastic environmental changes caused by species succession during a mixed-species bloom. This study investigated active bacterial groups and metabolic activity during a mixed bloom formed by dinoflagellates Prorocentrum obtusidens and Karenia mikimotoi using a metaproteomic approach. Bacterial community structure and dominant bacterial groups varied rapidly with the bloom regime shifts caused by species succession. Pseudoalteromonas and Vibrio dominated the bacterial community in the P. obtusidens-dominated regime, while Alteromonas, Cytophaga-Flavobacteria-Bacteroides (CFB) group, and marine Roseobacter clade (MRC) were the major contributors in other regimes, with the most abundant taxa being Alteromonas in the K. mikimotoi-dominated regime and the CFB group in the dissipation regime. Specific metabolic niches and unique substrate specificity of different bacterial groups enabled them to dominate and thrive in different bloom regimes. High metabolic plasticity in signal response, substrate utilization, motility, and adhesion are essential for bacteria to respond to drastic bloom regime shift, and the predominance of specific bacteria under unique bloom regimes may be the result of long-term coevolution between bacteria and bloom-forming phytoplankton species.

A Strategic Framework for Community Engagement in Oceans and Human Health

Over the past two decades, scientific research on the connections between the health and resilience of marine ecosystems, and human health, well-being, and community prosperity has expanded and evolved into a distinct "metadiscipline" known as Oceans and Human Health (OHH), recognized by the scientific community as well as policy makers. OHH goals are diverse, and seek to improve public health outcomes, promote sustainable use of aquatic systems and resources, and strengthen community resilience. OHH research has historically included some level of community outreach and partner involvement; however, the increasing disruption of aquatic environments and urgency of public health impacts calls for a more systematic approach to effectively identify and engage with community partners to achieve project goals and outcomes. Herein, we present a strategic framework developed collaboratively by community engagement personnel from the four recently established U.S. Centers for Oceans and Human Health (COHH). This framework supports researchers in defining levels of community engagement and in aligning partners, purpose, activities, and approaches intentionally in their community engagement efforts. Specifically, we describe: (1) a framework for a range of outreach and engagement approaches; (2) the need for identifying partners, purpose, activities, and approaches; and (3) the importance of making intentional alignment among them. Misalignment across these dimensions may lead to wasting time or resources, eroding public trust, or failing to achieve intended outcomes. We illustrate the framework with examples from current COHH case studies, and conclude with future directions for strategic community engagement in OHH and other environmental health contexts.

Daily Samples Revealing Shift in Phytoplankton Community and Its Environmental Drivers during Summer in Qinhuangdao Coastal Area, China

Rapid urbanization and economic development in coastal regions have significantly increased coastal nutrient pollution and remarkably changed the phytoplankton community and developed some species into bloom, resulting in large economic losses and serious threats to public health. Therefore, it is indispensable to reveal the shift in the phytoplankton community and phytoplankton abundance, and phytoplankton’s environmental drivers. However, previous studies could not present the details of the environmental drivers of phytoplankton due to samples being collected with low temporal resolution. Here, high-temporal-resolution (daily) samples were collected to investigate the influence of environmental factors on phytoplankton in Qinhuangdao for 44 days. Phytoplankton communities showed a rapid succession, with predominant genera changing in the order Skeletonema–Chaetoceros–Skeletonema–Thalassiosira. Similarly, Thalassiosira pacifica, Skeletonema costatum, Chaetoceros tortissimus, and Chattonella marina were identified as the dominant species and were abundant in 0–1.27 × 107 cells·L−1, 0–9.34 × 106 cells·L−1, 0–6.49 × 106 cells·L−1, and 0–3.64 × 106 cells·L−1, respectively. Moreover, inflows facilitate the rapid succession of the phytoplankton community. Dissolved inorganic phosphorus (DIP) was found to remarkably influence the succession of phytoplankton communities and the bloom of the top three dominant species, i.e., Thalassiosira pacifica, Skeletonema costatum, and Chaetoceros tortissimus. Overall, our results provide high-temporal-resolution observations of phytoplankton community succession and reveal its environmental drivers. This contributes to our current understanding of the occurrence of algae blooms and supports the development of management strategies to control algae bloom in coastal waters.

Morphological variation and phylogeny of Karenia selliformis (Gymnodiniales, Dinophyceae) in an intensive cold-water algal bloom in eastern Hokkaido, Japan

Harmful algal blooms responsible for mass mortalities of marine organisms have been rare in Hokkaido, northern Japan, although fish-killing blooms have been frequently reported from western Japanese coasts. In September-November 2021, a huge and prolonged cold-water bloom occurred along the Pacific coast of eastern Hokkaido, and was associated with intensive mortalities of sea urchin, fish, octopus, shellfish, etc. In this study, morphology and phylogeny of the dominant and co-occurring unarmored dinoflagellates of the Kareniaceae in the bloom were examined by using light microscopy, scanning electron microscopy and molecular phylogeny inferred from ITS and LSU rDNA (D1-D3) sequences. Morphological observation and molecular phylogeny showed that the dominant species was Karenia selliformis, with co-occurrences of other kareniacean dinoflagellates, Kr. longicanalis, Kr. mikimotoi, Karlodinium sp., Takayama cf. acrotrocha, Takayama tuberculata and Takayama sp. The typical cell forms of Kr. selliformis in the bloom were discoid, dorsoventrally flattened, and 35.3-43.6 (39.4  ±  2.1) µm in length, which was larger than the cell sizes in previous reports. Transparent cells of Kr. selliformis, lacking chloroplasts or having a few shrunken chloroplasts and oil droplets, were also found. Cells of Kr. selliformis showed morphological variation, but the species could be distinguished from other co-occurring Karenia species by the nucleus positioned in the hypocone and chloroplasts numerous (46-105) in number and small (2.9-4.6 µm) in diameter. Cell density of Kr. selliformis exceeding 100 cells mL^-1 was recorded in the temperature range of 9.8-17.6 °C. The rDNA sequences determined from Kr. selliformis in the blooms of Hokkaido, Japan in 2021 were identical to those from the bloom in Kamchatka, Russia in 2020.

Relationships between blooms of Karenia brevis and hypoxia across the West Florida Shelf

Harmful algal blooms (HABs) caused by the dinoflagellate Karenia brevis on the West Florida Shelf have become a nearly annual occurrence causing widespread ecological and economic harm. Effects range from minor respiratory irritation and localized fish kills to large-scale and long-term events causing massive mortalities to marine organisms. Reports of hypoxia on the shelf have been infrequent; however, there have been some indications that some HABs have been associated with localized hypoxia. We examined oceanographic data from 2004 to 2019 across the West Florida Shelf to determine the frequency of hypoxia and to assess its association with known HABs. Hypoxia was present in 5 of the 16 years examined and was always found shoreward of the 50-meter bathymetry line. There were 2 clusters of recurrent hypoxia: midshelf off the Big Bend coast and near the southwest Florida coast. We identified 3 hypoxic events that were characterized by multiple conductivity, temperature, and depth (CTD) casts and occurred concurrently with extreme HABs in 2005, 2014, and 2018. These HAB-hypoxia events occurred when K. brevis blooms initiated in early summer months and persisted into the fall likely driven by increased biological oxygen demand from decaying algal biomass and reduced water column ventilation due to stratification. There were also four years, 2011, 2013, 2015, and 2017, with low dissolved oxygen located near the shelf break that were likely associated with upwelling of deeper Gulf of Mexico water onto the shelf. We had difficulty in assessing the spatiotemporal extent of these events due to limited data availability and potentially unobserved hypoxia due to the inconsistent difference between the bottom of the CTD cast and the seafloor. While we cannot unequivocally explain the association between extreme HABs and hypoxia on the West Florida Shelf, there is sufficient evidence to suggest a causal linkage between them.

The value of monitoring in efficiently and adaptively managing biotoxin contamination in marine fisheries

Harmful algal blooms (HABs) can produce biotoxins that accumulate in seafood species targeted by commercial, recreational, and subsistence fisheries and pose an increasing risk to public health as well as fisher livelihoods, recreational opportunities, and food security. Designing biotoxin monitoring and management programs that protect public health with minimal impacts to the fishing communities that underpin coastal livelihoods and food systems is critically important, especially in regions with worsening HABs due to climate change. This study reviews the history of domoic acid monitoring and management in the highly lucrative U.S. West Coast Dungeness crab fishery and highlights three changes made to these programs that efficiently and adaptively manage mounting HAB risk: (1) expanded spatial-temporal frequency of monitoring; (2) delineation of clear management zones; and (3) authorization of evisceration orders as a strategy to mitigate economic impacts. Simulation models grounded in historical data were used to measure the value of monitoring information in facilitating efficient domoic acid management. Power analysis confirmed that surveys sampling 6 crabs (the current protocol) have high power to correctly diagnose contamination levels and recommend appropriate management actions. Across a range of contamination scenarios, increasing the spatial-temporal frequency of monitoring allowed management to respond more quickly to changing toxin levels and to protect public health with the least impact on fishing opportunities. These results highlight the powerful yet underutilized role of simulation testing and power analysis in designing efficient biotoxin monitoring programs, demonstrating the credibility of these programs to stakeholders, and justifying their expense to policymakers.

Characterization of Atmospheric Processes of Brevetoxins in Sea Spray Aerosols from Red Tide Events

Atmospheric processes can affect the longevity of harmful toxins in sea spray aerosols (SSA). This study characterized the degradation of brevetoxin (BTx) in SSA under different environmental conditions. The samples of seawater collected during a Karenia brevis bloom in Manasota, Florida, were nebulized into a large outdoor photochemical chamber to mimic the atmospheric oxidation of aerosolized toxins and then aged in the presence or absence of sunlight and/or O₃. Aerosol samples were collected during the aging process using a Particle-Into-Liquid Sampler. Their BTx concentrations were measured using an enzyme-linked immuno-sorbent assay (ELISA) and high-performance liquid chromatography/tandem mass spectroscopy. The BTx ozonolysis rate constant measured by ELISA was 5.74 ± 0.21 × 10³ M^-1 s^-1. The corresponding lifetime for decay of 87.5% BTx in the presence of 20 ppb of O₃ was 7.08 ± 0.26 h, suggesting that aerosolized BTx can still travel long distances at night before SSA deposition. BTx concentrations in SSA decreased more rapidly in the presence of sunlight than in its absence due to oxidation with photochemically produced OH radicals.

Marine Origin Ligands of Nicotinic Receptors: Low Molecular Compounds, Peptides and Proteins for Fundamental Research and Practical Applications

The purpose of our review is to briefly show what different compounds of marine origin, from low molecular weight ones to peptides and proteins, offer for understanding the structure and mechanism of action of nicotinic acetylcholine receptors (nAChRs) and for finding novel drugs to combat the diseases where nAChRs may be involved. The importance of the mentioned classes of ligands has changed with time; a protein from the marine snake venom was the first excellent tool to characterize the muscle-type nAChRs from the electric ray, while at present, muscle and α7 receptors are labeled with the radioactive or fluorescent derivatives prepared from α-bungarotoxin isolated from the many-banded krait. The most sophisticated instruments to distinguish muscle from neuronal nAChRs, and especially distinct subtypes within the latter, are α-conotoxins. Such information is crucial for fundamental studies on the nAChR revealing the properties of their orthosteric and allosteric binding sites and mechanisms of the channel opening and closure. Similar data are provided by low-molecular weight compounds of marine origin, but here the main purpose is drug design. In our review we tried to show what has been obtained in the last decade when the listed classes of compounds were used in the nAChR research, applying computer modeling, synthetic analogues and receptor mutants, X-ray and electron-microscopy analyses of complexes with the nAChRs, and their models which are acetylcholine-binding proteins and heterologously-expressed ligand-binding domains.

Generation of Reactive Oxygen Species (ROS) by Harmful Algal Bloom (HAB)-Forming Phytoplankton and Their Potential Impact on Surrounding Living Organisms

Most marine phytoplankton with relatively high ROS generation rates are categorized as harmful algal bloom (HAB)-forming species, among which Chattonella genera is the highest ROS-producing phytoplankton. In this review, we examined marine microalgae with ROS-producing activities, with focus on Chattonella genera. Several studies suggest that Chattonella produces superoxide via the activities of an enzyme similar to NADPH oxidase located on glycocalyx, a cell surface structure, while hydrogen peroxide is generated inside the cell by different pathways. Additionally, hydroxyl radical has been detected in Chattonella cell suspension. By the physical stimulation, such as passing through between the gill lamellas of fish, the glycocalyx is easily discharged from the flagellate cells and attached on the gill surface, where ROS are continuously produced, which might cause gill tissue damage and fish death. Comparative studies using several strains of Chattonella showed that ROS production rate and ichthyotoxicity of Chattonella is well correlated. Furthermore, significant levels of ROS have been reported in other raphidophytes and dinoflagellates, such as Cochlodinium polykrikoides and Karenia mikimotoi. Chattonella is the most extensively studied phytoplankton in terms of ROS production and its biological functions. Therefore, this review examined the potential ecophysiological roles of extracellular ROS production by marine microalgae in aquatic environment.

Temporal and Spatial Signaling Mediating the Balance of the Plankton Microbiome

The annual patterns of plankton succession in the ocean determine ecological and biogeochemical cycles. The temporally fluctuating interplay between photosynthetic eukaryotes and the associated microbiota balances the composition of aquatic planktonic ecosystems. In addition to nutrients and abiotic factors, chemical signaling determines the outcome of interactions between phytoplankton and their associated microbiomes. Chemical mediators control essential processes, such as the development of key morphological, physiological, behavioral, and life-history traits during algal growth. These molecules thus impact species succession and community composition across time and space in processes that are highlighted in this review. We focus on spatial, seasonal, and physiological dynamics that occur during the early association of algae with bacteria, the exponential growth of a bloom, and its decline and recycling. We also discuss how patterns from field data and global surveys might be linked to the actions of metabolic markers in natural phytoplankton assemblages.

High-resolution Spatiotemporal Dynamics of Harmful Algae in the Indian River Lagoon (Florida)-A Case Study of Aureoumbra lagunensis, Pyrodinium bahamense, and Pseudo-nitzschia

The Indian River Lagoon (IRL), located on the east coast of Florida, is a complex estuarine ecosystem that is negatively affected by recurring harmful algal blooms (HABs) from distinct taxonomic/functional groups. Enhanced monitoring was established to facilitate rapid quantification of three recurrent bloom taxa, Aureoumbra lagunensis, Pyrodinium bahamense, and Pseudo-nitzschia spp., and included corroborating techniques to improve the identification of small-celled nanoplankton (<10 μm in diameter). Identification and enumeration of these target taxa were conducted during 2015-2020 using a combination of light microscopy and species-specific approaches, specifically immunofluorescence flow cytometry as well as a newly developed qPCR assay for A. lagunensis presented here for the first time. An annual bloom index (ABI) was established for each taxon based on occurrence and abundance data. Blooms of A. lagunensis (>2×10⁸ cells L^-1) were observed in all six years sampled and across multiple seasons. In contrast, abundance of P. bahamense, largely driven by the annual temperature cycle that moderates life cycle transitions and growth, displayed a strong seasonal pattern with blooms (10⁵-10⁷ cells L^-1) generally developing in early summer and subsiding in autumn. However, P. bahamense bloom development was delayed and abundance was significantly lower in years and locations with sustained A. lagunensis blooms. Pseudo-nitzschia spp. were broadly distributed with sporadic bloom concentrations (reaching 10⁷ cells L^-1), but with minimal concentrations of the toxin domoic acid detected (<0.02 μg L^-1). In summer 2020, multiple monitoring tools characterized a novel nano-cyanobacterium bloom (reaching 10⁹ cells L^-1) that coincided with a decline in A. lagunensis and persisted into autumn. Statistical and time-series analyses of this spatiotemporally intensive dataset highlight prominent patterns in variability for some taxa, but also identifies challenges of characterizing mechanisms underlying more episodic yet persistent events. Nevertheless, the intersect of temperature and salinity as environmental proxies proved to be informative in delineating niche partitioning, not only in the case of taxa with long-standing data sets but also for seemingly unprecedented blooms of novel nanoplanktonic taxa.

Transcriptomic Profile of the Cockle Cerastoderma edule Exposed to Seasonal Diarrhetic Shellfish Toxin Contamination

Bivalves constitute an important source of proteins for human consumption, but some accumulate biotoxins such as diarrhetic shellfish toxins (DSTs), constituting a risk to human health. The cockle Cerastoderma edule is one of the most important species harvested in the Portuguese coast but also one of the most affected species due to recurrent DSTs exposure. However, little is known regarding the effects of the toxins produced by blooming dinoflagellates on C. edule. Herein, we explore the Differentially Expressed Genes (DEGs) of two tissues (gills and digestive gland) from wild cockles sampled in Portugal, through their whole transcriptomic response in two different seasons (exposed and not exposed to DSTs). The de novo transcriptome assembly returned 684,723 contigs, N50 of 1049, and 98.53% completeness. Altogether, 1098 DEGs were identified, of which 353 DEGs were exclusive for the digestive gland, 536 unique for the gills and 209 DEGs were common. Among DEGs were identified known DSTs-biomarkers including glutathione peroxidase, glutathione S-transferase, superoxide dismutase, cytochrome P450, ABC transporters, actin and tubulin-related proteins, Heat shock proteins and complement C1Q-like proteins. This study provides the first transcriptomic profile of C. edule, giving new insights about its molecular responses under different environmental conditions of DSTs exposure.

The potential of prodigiosin for control of Prorocentrum donghaiense blooms: Algicidal properties and acute toxicity to other marine organisms at various trophic levels

Prorocentrum donghaiense, a marine dinoflagellate, causes harmful algal blooms (HABs) characterised by the highest outbreak frequency and most extensive coverage among similar species in the East China Sea. Highly efficient and ecofriendly biocontrol strategies should be developed for HAB control. Prodigiosin is an efficient biological algicide that demonstrated strong algicidal activity towards P. donghaiense. However, the mechanism of its toxicity to P. donghaiense is unknown. These factors were investigated to evaluate potential use of prodigiosin for control of P. donghaiense blooms. Photosynthetic electron transport rate, maximum quantum yield and respiration rate of P. donghaiense decreased significantly upon exposure to prodigiosin, indicating that prodigiosin rapidly exerted adverse effects on the chloroplasts and mitochondria. Furthermore, a significant increase in dichlorofluorescein fluorescence intensity indicated an overproduction of reactive oxygen species (ROS). The antioxidant system of P. donghaiense scavenged ROS; however, an increase in malondialdehyde concentrations indicated that excessive ROS were still able to initiate lipid peroxidation. Thus, ROS production resulted in the formation of lipids with a reduced degree of unsaturation. Lipid peroxidation decreased lipid fluidity and rigidified the membrane system, causing serious functional destruction of the membrane. Flow cytometry analysis indicated that prodigiosin arrested the cell cycle of P. donghaiense. However, surviving algal cells were able to repair the damaged functions and resume the cell cycle after prodigiosin was removed by photodegradation. Otherwise, P. donghaiense cells lost their membrane integrity and died. To begin an evaluation of ecological safety of prodigiosin, we tested four marine organisms at various trophic levels. The results of these tests indicated that Chlorella vulgaris, Photobacterium phosphoreum, Artemia salina and Lateolabrax japonicus were less sensitive to prodigiosin than P. donghaiense. Toxicity to all five organisms declined after prodigiosin was exposed to sunlight for 6 h. Considering the toxic doses of prodigiosin to various organisms and its photodegradation characteristics, we suggest that prodigiosin has potential in controlling P. donghaiense blooms but should be applied at night, in small doses, with multiple applications.

Digital Technologies and Open Data Sources in Marine Biotoxins' Risk Analysis: The Case of Ciguatera Fish Poisoning

Currently, digital technologies influence information dissemination in all business sectors, with great emphasis put on exploitation strategies. Public administrations often use information systems and establish open data repositories, primarily supporting their operation but also serving as data providers, facilitating decision-making. As such, risk analysis in the public health sector, including food safety authorities, often relies on digital technologies and open data sources. Global food safety challenges include marine biotoxins (MBs), being contaminants whose mitigation largely depends on risk analysis. Ciguatera Fish Poisoning (CFP), in particular, is a MB-related seafood intoxication attributed to the consumption of fish species that are prone to accumulate ciguatoxins. Historically, CFP occurred endemically in tropical/subtropical areas, but has gradually emerged in temperate regions, including European waters, necessitating official policy adoption to manage the potential risks. Researchers and policy-makers highlight scientific data inadequacy, under-reporting of outbreaks and information source fragmentation as major obstacles in developing CFP mitigation strategies. Although digital technologies and open data sources provide exploitable scientific information for MB risk analysis, their utilization in counteracting CFP-related hazards has not been addressed to date. This work thus attempts to answer the question, "What is the current extent of digital technologies' and open data sources' utilization within risk analysis tasks in the MBs field, particularly on CFP?", by conducting a systematic literature review of the available scientific and grey literature. Results indicate that the use of digital technologies and open data sources in CFP is not negligible. However, certain gaps are identified regarding discrepancies in terminology, source fragmentation and a redundancy and downplay of social media utilization, in turn constituting a future research agenda for this under-researched topic.