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A somewhat disparate, yet temporally cohesive, set of phytoplankton abundance, microphytobenthos, including the diatom Pseudo-nitzschia, benthic infauna, and sediment toxin data were used to develop a theory for the transfer of domoic acid (DA) from the toxic diatom to the benthos in the highly productive waters of the northern Gulf of Mexico near the Mississippi River plume. Archived samples and new data were used to test the theory that DA is likely to be incorporated into benthic consumers. High spring abundances of potentially toxic Pseudo-nitzschia diatoms were simultaneously present in the surface waters, bottom waters and on the seafloor. Examination of the gut contents of a typical deposit-feeding and suspension-feeding polychaete, Paraprionospio pinnata, during similar periods of high Pseudo-nitzschia abundance in surface water indicated consumption of the diatoms. Demersal fishes, particularly Atlantic croaker, are known to consume these polychaetes, with a potential for transfer of DA to even higher trophic levels. These findings warrant a theory to be tested with further studies about the trophic linkage of a phytoplankton toxin into the benthic food web.

Scientific Literacy in America is very low compared to other developed countries. The public has a poor understanding of basic scientific principles (28% are considered scientifically literate) and outreach efforts to address this problem are limited. When looking at specific issues such as harmful algal blooms in freshwater systems there is hardly any active outreach programs. The basis for this study was to help the public understand what harmful algal blooms are and what visual indicators exist to warn of their presence. Initial surveys were conducted to find out what fishermen knew about algae and harmful algal blooms. The participants (age 11–70) had heard of algae (100%), but very few had heard of a harmful algal bloom (40%) and when the participants were pressed on the subject, few could define algae. An educational brochure was created from the baseline of data collected from the public and was distributed to the same fishing areas. A follow-up interview of these areas showed that the brochures were being taken by people, but finding those actual people proved difficult. Once brochures were viewed, many people were able to indicate something new they learned about algae such as algae produces oxygen. Scientists need to take a more active role in conveying their research to the public in order to increase scientific knowledge.

Harmful algal blooms are an increasing problem for coastal waters world-wide. The presence of the toxigenic diatom genus Pseudo-nitzschia is of concern in the Gulf of Mexico, due to the potential for several species in this genus to produce the neurotoxin domoic acid (DA). Louisiana coastal waters are of particular interest due to the presence of both toxin-producing species of Pseudo-nitzschia and abundant potential vectors. While trophic transfer of DA to consumers has repeatedly occurred along the California coast, little is known about trophic transfer of recently detected DA in the Gulf of Mexico. In this study, the presence of DA was investigated in filter-feeding gulf menhaden (Brevoortia patronus) and in seawater where high abundances of these fish reside. Pseudo-nitzschia presence and enumeration was determined using light microscopy, species identification in seawater and gulf menhaden gut contents was conducted with transmission electron microscopy (TEM), and DA quantification in corresponding seawater and tissue samples was determined by competitive enzyme-linked immunosorbent assay (cELISA). Examination of the phytoplankton revealed the presence of four species of Pseudo-nitzschia: P. calliantha for the first time, P. pseudodelicatissima, P. pungens, and P. americana, with P. calliantha as the dominant Pseudo-nitzschia species. Low levels of DA were detected in both seawater and fish samples, with a significant correlation between the two (n = 22, p = 0.043). Thus, for the first time in the Gulf of Mexico, a potential vector of DA has been identified, revealing the possibility of DA contamination in coastal Louisiana food webs. Published by Elsevier B.V.

Toxin producing cyanobacteria commonly inhabit fresh waters and brackish estuaries, and blooms of these species may be escalating worldwide due to eutrophication. The most common cyanobacterial toxins occurring in fresh and brackish waters are microcystins (MC), which are known to accumulate in aquatic organisms. Prey preference for filter-feeding organisms, such as clams and mussels, make the blue crab, Callinectes sapidus, a candidate for microcystin contamination, therefore making this commercially important edible crab species a potential vector of these toxins to humans. The present study was conducted in a hyper-eutrophic freshwater lake, Lac des Allemands, located in the Barataria estuary system of southeastern Louisiana, and was aimed at documenting the presence and abundance of toxic cyanobacteria and assessing microcystin concentrations in surface water and blue crabs taken from this region. Microcystis sp. were the dominant cyanobacteria, with alternating blooms of Microcystis and Anabaena spp. occurring during the 8-month study. Enzyme-linked immunosorbent assay (ELISA) was used to evaluate concentrations of microcystins from surface water and hepatopancreas, viscera, and muscle tissues of blue crabs. The highest concentration of microcystins found in surface water (1.42 μg MC l−1) was above the tolerable daily intake (TDI) guideline for microcystins in drinking water (1.0 μg MC l−1) set by the World Health Organization (WHO). Highest concentration of microcystins occurring in crab tissue were 820 μg MC kg−1 in hepatopancreas, 65 μg MC kg−1 in viscera, and 105 μg MC kg−1 in muscle, which were close to or exceeding the WHO-TDI guidelines for human consumption (0.04 μg MC kg−1 body weight day−1) based on human body weight and amount of crab tissue consumed. This study documents the presence of microcystins in both surface water and blue crab tissue and therefore, demonstrates the potential for Microcystis and Anabaena blooms to produce toxins that may be accumulated in the tissues of blue crabs and transferred to higher level consumers, including humans.

Over the past decade diatom blooms of domoic acid (DA)-producing Pseudo-nitzschia spp. have been responsible for numerous marine mammal and bird mortalities in Monterey Bay, CA. One possible toxin vector is the market squid, Loligo opalescens , a small pelagic mollusk that plays an important role in the near-shore food web of the California Current ecosystem as a favored vertebrate prey species. This study examined the trophic link between toxic Pseudo-nitzschia and L. opalescens using toxin and stomach content analyses of animals collected from Monterey Bay, CA in 2000. Receptor binding assay data (confirmed by tandem mass spectrometry), demonstrated the presence of DA in squid during a toxic Pseudo-nitzschia event, with P. australis frustules observed in stomach samples. Though DA levels were low ( −1 tissue) in L. opalescens during the study period, it is now clear that this potent neurotoxin can occur in squid and is likely delivered through its krill prey species, which are known to retain DA after feeding on toxic Pseudo-nitzschia . Our findings suggest that further study of the relationship between Pseudo-nitzschia blooms and DA contamination of squid is warranted to better evaluate the potential health risk to humans and wildlife associated with this major commercial seafood species and important prey item.