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Microcystins in Bivalves: Optimizing of Monitoring For and Minimizing Risk From an Emerging Human Health Threat

This project began in September 2019 and is projected to be completed in August 2022

This project addresses an emerging concern across the US - the transfer of freshwater algal toxins into the marine environment where they can infiltrate the food web and present a health risk to both humans and wildlife. Microcystin monitoring approaches in both bivalves and water samples will be evaluated for their collective suitability to detect microcystins in marine bivalves. This study will generate information on the occurrence, prevalence, and concentrations of microcystins in bivalves.

Why We Care
Toxins from harmful cyanobacterial blooms such as microcystin are a threat to the health of animals and humans. There are now data demonstrating that microcystins associated blooms of Microcystis accumulate in shellfish in California, Washington, Louisiana, Virginia, and New York (NY) at concentrations exceeding guidance levels set by some states for food and beyond the estimated tolerable daily intake rate set by the US Environmental Protection Agency (EPA). Results have demonstrated that microcystin is transported to estuarine and coastal regions where it can bioaccumulate in shellfish. Once in the shellfish, the toxins enter the food web and may cause death in bivalve-consuming marine mammals. Bivalves, including oysters, represent a 2 billion dollar fishery in the US. Oysters are the most valuable US aquacultured shellfish and the second most valuable commercial shellfishery. Oysters thrive within brackish zones of estuaries, downstream from freshwater bodies that are increasingly prone to microcystin-producing cyanobacterial blooms. In New York, for example, oysters have been shown to contain high microcystin concentrations. Unfortunately, the scope of microcystin contamination of estuarine bivalves is unclear, as are the optimal methods for monitoring and predicting levels of microcystins in bivalves.

What Are We Doing
The overarching objective of this project is to combine and compare traditional and novel microcystin monitoring approaches with bivalve and water column monitoring approaches to assess their collective suitability in detecting and predicting microcystin concentrations within estuarine bivalves. To identify technologies most predictive of microcystin contamination of bivalves, time series sampling across freshwater-to-marine continuums within multiple estuarine ecosystems will be established on the US east and west coasts. For each time series, concentrations of microcystins in bivalves will be measured using liquid chromatograph mass spectrometry (LC-MS) and these values will be compared to the newly available Abraxis, Inc enzyme-linked immunosorbent assay (ELISA) for microcystins in bivalves. In tandem, solid phase adsorption toxin tracking (SPATT) devices will be deployed and sampled at varying distances between bivalve collection sites and freshwater tributaries suspected of delivering microcystins to each estuarine region.

Additionally, a suite of water column-based measurements will be made to assess their value in predicting microcystin accumulation in bivalves. These measurements include microcystin concentration and identification of cyanobacteria by quantitative polymerase chain reaction (PCR). Rates of microcystin accumulation and depuration will be quantified and statistical models will be developed to identify the environmental factors that forecast and are most predictive of microcystin accumulation in bivalves. An added benefit of this project will be an assessment of new technologies for quantifying or predicting microcystin concentrations in water and bivalves.

The researchers will collaborate with federal, state, and local agencies and bivalve farms to facilitate the transitioning of successful approaches to end users. Management-relevant actions of this project will include webinars, fact sheets, presentations of the major findings, and recommendations of this project, as well as training regulatory agencies and bivalve growers in the use of the most effective technologies assessed during this project.

Dr. Christopher Gobler of Stony Brook University leads this project. This project is co-led by Dr. Raphael Kudela University of California at Santa Cruz. The project is funded through the NCCOS Monitoring and Event Response for Harmful Algal Blooms (MERHAB) Program.

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