The polychaete, Paraprionospio pinnata, is a likely vector of domoic acid to the benthic food web in the northern Gulf of Mexico

Updated checklist of polychaete species (Annelida) recorded from Malaysia, with remarks on the research history

Background

An updated comprehensive checklist of polychaete species, which have been recorded from Malaysian waters, is provided, with their geographic distributions and the research history for them. A total of 57 species belonging to 30 families have been reported since the early 1870s, with Nereididae as the most dominant family with ten species; however, more than half of the total are questionable species in the country. Despite the increased efforts of polychaete studies in the past decade, the taxonomic endeavour of discovering and describing species in the country could be higher. Malaysian polychaetes were mostly recorded from Peninsular Malaysia, whereas very few were from Borneo Island. Most previously recorded species were associated with intertidal and estuarine habitats and a few were found in the subtidal and freshwater environments. We stress the need for urgent research on this biologically, ecologically and culturally relevant taxonomic group as the species accumulation curve grows exponentially in this megadiverse country.

New information

The current checklist has been updated since the previous one in 2013. Many species previously listed were judged as doubtful and not taxonomically reliable.

Phycotoxins and marine annelids - A global review

Several species of microalgae can produce potent phycotoxins that negatively affect aquatic organisms and their consumers following different exposure routes, as well as toxicokinetic (TK) and toxicodynamic (TD) processes. Benthic organisms are especially vulnerable as they are exposed to both benthic and planktonic species causative of harmful algal blooms (HABs). While benthic algae can come into direct contact with annelids during substrate remobilization, planktonic cells can settle to the bottom mostly during senescence and/or encystment stages, and in shallow and calm waters. We performed a systematic, qualitative review of the literature on the phycotoxin TK and TD processes in marine annelids, summarizing the most relevant findings and general trends. Besides, by using innovative analytical/statistical approaches, we were able to detect patterns and gaps in the current literature, thus pointing to future research directions. We retrieved and analyzed studies involving diarrhetic shellfish toxins (DSTs), paralytic shellfish toxins (PSTs), brevetoxins (PbTXs), domoic acid (DA), as well as palytoxin and its congeners, the ovatoxins (treated together as PLTXs). It is worth mentioning that studies evaluating other phycotoxins (e.g., ciguatoxins, yessotoxins) were not found in the literature. The absence of data on PbTXs, PSTs and DA is the largest gap hampering TK assessment in annelids, although some relevant information on TD is already available. Whereas lethal effects from DSTs have not been reported, more potent toxins like PbTXs, PSTs, DA and those grouped as PLTX-like compounds can cause mortality and/or marked decrease in annelid abundance. In addition, phycotoxins have been linked to sublethal effects on annelid cells. Although very sparse, field and laboratory studies offer strong evidence that annelids may be reliable indicators of toxin exposure and their negative effects during both early and later stages of HABs in marine environments. Besides quickly responding to these compounds at both organismic and suborganismic levels, annelids are easily found in areas affected by HABs. The use of annelids in future investigations evaluating the action mechanisms of toxic microalgae on marine invertebrates should be thus encouraged. In this case, the choice for widely dispersed and numerically dominant species of annelids would strengthen the validation and extrapolation of results from risk assessments in areas affected by HABs worldwide.

Domoic Acid and Pseudo-nitzschia spp. Connected to Coastal Upwelling along Coastal Inhambane Province, Mozambique: A New Area of Concern

Harmful algal blooms (HABs) are increasing globally in frequency, persistence, and geographic extent, posing a threat to ecosystem and human health. To date, no occurrences of marine phycotoxins have been recorded in Mozambique, which may be due to absence of a monitoring program and general awareness of potential threats. This study is the first documentation of neurotoxin, domoic acid (DA), produced by the diatom Pseudo-nitzschia along the east coast of Africa. Coastal Inhambane Province is a biodiversity hotspot where year-round Rhincodon typus (whale shark) sightings are among the highest globally and support an emerging ecotourism industry. Links between primary productivity and biodiversity in this area have not previously been considered or reported. During a pilot study, from January 2017 to April 2018, DA was identified year-round, peaking during Austral winter. During an intense study between May and August 2018, our research focused on identifying environmental factors influencing coastal productivity and DA concentration. Phytoplankton assemblage was diatom-dominated, with high abundances of Pseudo-nitzschia spp. Data suggest the system was influenced by nutrient pulses resulting from coastal upwelling. Continued and comprehensive monitoring along southern Mozambique would provide critical information to assess ecosystem and human health threats from marine toxins under challenges posed by global change.

Persistent domoic acid in marine sediments and benthic infauna along the coast of Southern California

Blooms of the diatom genus Pseudo-nitzschia occur annually in the Southern California Bight (SCB), and domoic acid (DA) associated with these events can contaminate fisheries, presenting both human and wildlife health risks. Recent studies have suggested that marine sediments may act as a reservoir for DA, extending the risk of food web contamination long after water column blooms have ended. In this study, we conducted a regional assessment of the extent and magnitude of DA in the benthic environment, and monthly observations of sediments and benthic infauna at multiple stations over a 16-month period. DA was widespread in continental shelf sediments of the SCB. The toxin was detected in 54% of all shelf habitats sampled. Detectable concentrations ranged from 0.11 ng/g to 1.36 ng/g. DA was consistently detected in benthic infauna tissues over the monthly timeseries, while the DA concentrations in sediments during the same period were commonly below detection or at low concentrations. The presence of DA in the benthic environment did not always have an apparent water column source, raising the possibility of lateral transport, retention/preservation in sediments or undetected blooms in subsurface waters. In most cases, DA was detected in tissues but not in the co-located surface sediments. Coarse taxonomic sorting of the infauna revealed that the accumulation of DA varied among taxa. We observed that DA was widespread among lower trophic level organisms in this study, potentially acting as a persistent source of DA to higher trophic levels in the benthos.

Assessing the efficiency of low-cost cleaning methods for diatoms from intertidal sediment samples

This study aims to compare the effectiveness of several low-cost reagents in obtaining high-quality diatom slides for microphytobenthos research. We evaluated the performance of eight reagents in sediment samples of beach intertidal zones. For each of the tested reagents, different pre-treatment conditions (pre-washed; non-washed) and three different temperatures (room temperature at 26 °C, 60 °C, and 100 °C) were also evaluated. For each treatment (combinations between reagents, temperatures, and pre-treatment conditions), we counted diatoms cells that met the criteria necessary for taxonomic identification (Whole/Half frustules or valves without cell material) in 30 randomly chosen fields of view in definitive preparations made from the treated samples. We also compared the treatments regarding species richness and diversity observed in the definitive preparations. The reagents influenced more the conditions of diatoms cells than the temperature and pre-treatment. H₂O₂, HNO₃, NaClO were the methods that had the best performance in relation to the number of identifiable items. The six treatments with H₂O₂ presented similar amounts of identifiable items, regardless of pre-treatment and temperature. HNO₃ presented a higher number of identifiable items in non-washed and pre-washed treatments at 60 °C and non-washed at 100 °C. NaClO had its best performance the following treatments: non-washed at room temperature and non-washed and pre-washed at 60 °C. H₂O₂ and HNO₃ also showed better results for diatom species richness and diversity, followed by NaClO. The use of H₂O₂ was more robust since it obtained good results regardless of temperature and pre-treatments and should be preferred. HNO₃ and NaClO should be used only with the appropriate temperatures, and pre-washing should be avoided.

Organic polymer consumption facilitates domoic acid entry into the marine food web without direct ingestion of Pseudo-nitzschia

Domoic acid (DA) is a neurotoxin produced by diatoms from the genera Pseudo-nitzschia and Nitzschia. DA is transferred through the food web when consumed by organisms such as copepods (e.g., Acartia tonsa). DA bioaccumulates in higher trophic levels and poses a threat to human health through amnesic shellfish poisoning. Laboratory experiments using a DA reference standard demonstrated that mild turbulence facilitates formation of organic polymer aggregates >0.6 µm in-vivo that can scavenge dissolved DA (dDA). Using A. tonsa, we demonstrate that DA can be assimilated through consumption of these organic polymers which scavenged dDA -a pathway which does not require direct ingestion of the toxin-producer Pseudo-nitzschia. In filtered seawater with spiked DA, copepods accumulated 24.8 ± 4.7 pg DA copepod-1 (2.1 ppm) on average by consuming organic polymers. This was validated in one out of five experiments using ambient DA concentrations. Copepods were suspended in particle-free seawater and accumulated 14.4 ± 3.8 pg DA copepod-1 (1.20 ppm), and in particle-concentrated seawater they accumulated 40.9 ± 3.8 pg DA copepod-1 (3.42 ppm). Data from this experiment suggests that ~34% of the total assimilated DA entered via an organic polymer-bound DA pathway. This experiment had the highest Pseudo-nitzschia spp. abundance (~225,000 cells L - 1) and cellular toxin quota, up to 0.88 pg DA cell-1, relative to the other four ambient DA experiments. These results demonstrate the potential for DA to enter the marine food web through an alternate pathway and may have considerable implications to understanding the flow of DA through marine food webs, and how we monitor DA and its potential vectors into the food web.

Pseudo-nitzschia, Nitzschia, and domoic acid: New research since 2011

Some diatoms of the genera Pseudo-nitzschia and Nitzschia produce the neurotoxin domoic acid (DA), a compound that caused amnesic shellfish poisoning (ASP) in humans just over 30 years ago (December 1987) in eastern Canada. This review covers new information since two previous reviews in 2012. Nitzschia bizertensis was subsequently discovered to be toxigenic in Tunisian waters. The known distribution of N. navis-varingica has expanded from Vietnam to Malaysia, Indonesia, the Philippines and Australia. Furthermore, 15 new species (and one new variety) of Pseudo-nitzschia have been discovered, bringing the total to 52. Seven new species were found to produce DA, bringing the total of toxigenic species to 26. We list all Pseudo-nitzschia species, their ability to produce DA, and show their global distribution. A consequence of the extended distribution and increased number of toxigenic species worldwide is that DA is now found more pervasively in the food web, contaminating new marine organisms (especially marine mammals), affecting their physiology and disrupting ecosystems. Recent findings highlight how zooplankton grazers can induce DA production in Pseudo-nitzschia and how bacteria interact with Pseudo-nitzschia. Since 2012, new discoveries have been reported on physiological controls of Pseudo-nitzschia growth and DA production, its sexual reproduction, and infection by an oomycete parasitoid. Many advances are the result of applying molecular approaches to discovering new species, and to understanding the population genetic structure of Pseudo-nitzschia and mechanisms used to cope with iron limitation. The availability of genomes from three Pseudo-nitzschia species, coupled with a comparative transcriptomic approach, has allowed advances in our understanding of the sexual reproduction of Pseudo-nitzschia, its signaling pathways, its interactions with bacteria, and genes involved in iron and vitamin B₁₂ and B₇ metabolism. Although there have been no new confirmed cases of ASP since 1987 because of monitoring efforts, new blooms have occurred. A massive toxic Pseudo-nitzschia bloom affected the entire west coast of North America during 2015-2016, and was linked to a 'warm blob' of ocean water. Other smaller toxic blooms occurred in the Gulf of Mexico and east coast of North America. Knowledge gaps remain, including how and why DA and its isomers are produced, the world distribution of potentially toxigenic Nitzschia species, the prevalence of DA isomers, and molecular markers to discriminate between toxigenic and non-toxigenic species and to discover sexually reproducing populations in the field.