Exposure to the Cyanotoxin Microcystin Arising from Interspecific Differences in Feeding Habits among Fish and Shellfish in the James River Estuary, Virginia.

Abstract

The cyanotoxin, microcystin (MC), is known to accumulate in the tissues of diverse aquatic biota although factors influencing exposure, such as feeding habits and seasonal patterns in toxin production, are poorly known. We analyzed seasonal variation in the MC content of primary and secondary consumers, and used dietary analysis (gut contents and stable isotopes) to improve understanding of cyanotoxin transport in food webs. Periods of elevated toxin concentration were associated with peaks in the abundance of genes specific to Microcystis and MC toxin production (mcyD). Peak toxin levels in consumer tissues coincided with peak MC concentrations in seston. However, toxins in tissues persisted in overwintering populations suggesting that potential health impacts may not be limited to bloom periods. Interspecific differences in tissue MC concentrations were related to feeding habits and organic matter sources as pelagic fishes ingested a greater proportion of algae in their diet, which resulted in greater MC content in liver and muscle tissues. Sediments contained a greater proportion of allochthonous (terrestrial) organic matter and lower concentrations of MC, resulting in lower toxin concentrations among benthic detritivores. Among shellfish, the benthic suspension feeder Rangia cuneata (wedge clam) showed seasonal avoidance of toxin ingestion due to low feeding rates during periods of elevated MC. Among predators, adult Blue Catfish had low MC concentrations, whereas Blue Crabs exhibited high levels of MC in both muscle and viscera.

Current Techniques for Detecting and Monitoring Algal Toxins and Causative Harmful Algal Blooms

“…There are some commercially available kits such as Ridascreen TM test kit (R-Biopharm, Darmstadt, Germany) for PSP toxins, DSPcheck kit (UBE Industries, Tokyo, Japan) and Rougier Biotech ELISA (Montreal, Quebec, Canada) for DSP toxins, ADDA ELISA kit for MCs and NOD (Abraxis, Warminster, PA, USA), and Cigua-Check for CTX toxins (Oceanit Test System, Hawaii, USA) [10,13,26,53,54] Cell-based assays employ live mammalian cells, which are based on cellular response that incorporates both binding to the receptors and subsequent intracellular signaling responses of the cell. Cellular assays rely on a number of end-points, including morphological change, or more commonly cytotoxicity and reporter gene activation [10].…”

“…It is also evident that various algal toxins might predominate in different water bodies. Seasonal variations of MCs in the tidal freshwater segment of the James River Estuary, for example, occurred with first peak in May, maximal concentration in July and August, and undetectable after November, concurrent with the abundance of Microcystis and the mcyD genes responsible for MC generation [13].…”

Current Techniques for Detecting and Monitoring Algal Toxins and Causative Harmful Algal Blooms

“…Microcystis ADDA-ELISA < 0.10 µg/L (May), 0.92 µg/L (July), < 0.05 µg/L (Nov) [13] Monterey Bay, California, USA…”

“…There are some commercially available kits such as Ridascreen TM test kit (R-Biopharm, Darmstadt, Germany) for PSP toxins, DSPcheck kit (UBE Industries, Tokyo, Japan) and Rougier Biotech ELISA (Montreal, Quebec, Canada) for DSP toxins, ADDA ELISA kit for MCs and NOD (Abraxis, Warminster, PA, USA), and Cigua-Check for CTX toxins (Oceanit Test System, Hawaii, USA)[10,13,26,53,54]. More methods are being developed toward commercial ELISA kits in detecting various algal toxins.…”

A Systematic Investigation into the Environmental Fate of Microcystins and The Potential Risk: Study in Lake Taihu

“…But is it absolutely safe when there is no obvious bloom? A study in the James River Estuary indicated that potential health risks may exist in non-bloom periods [ 34 ]. Another study in the San Francisco Estuary indicated that Microcystis , even at low abundance, may have influences on fishery production via toxic and food web at multiple trophic levels [ 35 ].…”