Domoic Acid Dataset

This map on domoic acid concentrations in Narragansett Bay (NB) was generated from a research project carried out at the University of Rhode Island by Co- Principal Investigators Drs. Matthew Bertin and Bethany Jenkins and their research teams. This work was funded by Rhode Island Sea Grant and the Rhode Island Consortium for Coastal Ecology Assessment, Innovation, and Modeling (RI C-AIM).

Background

The project monitored species of the diatom Pseudo-nitzschia (P-n) and their production of the neurotoxin domoic acid at selected sites in NB, Rhode Island. While P-n species have been present in NB for over 50 years, the first Rhode Island shellfish harvest closure due to high levels of domoic acid in the plankton was not until October 2016. This precautionary closure, another subsequent closure in March 2017 due to domoic acid exceeding action limits in shellfish meat, and the continued detection of low levels of domoic acid suggests that either P-n species composition has changed to new toxic- producing strains of P-n in NB, or NB environmental conditions have shifted in favor of making resident P-n more toxic. The 2016 and 2017 closures sparked interest in identifying environmental drivers that lead to increased domoic acid production as well as identifying P-n species composition in NB.

Methods

Over a two-year period from September 2017 – November 2019, our research group has sampled NB weekly, collecting samples to measure various environmental factors such as dissolved nutrients, chlorophyll a, temperature, and salinity from the surface seawater. Additionally, we have monitored P-n species (through genetic analysis of DNA sequences), and the cell-associated domoic acid from phytoplankton samples using liquid chromatography-tandem mass spectrometry (LC- MS/MS). Our genetic methods can distinguish between P-n species and our analytical methods are very sensitive and can detect very low levels of domoic acid (ng domoic acid/L of seawater).

Results

We have found seasonal differences in P-n species in NB and we have found a seasonal pattern in increased cell-associated domoic acid concentrations. All toxin concentrations are at low levels, and no closures occurred during the sampling period. Cell-associated domoic acid rises in the fall (September and October) and the late spring/early summer (May and June), and highest concentrations were observed at the sites closest to the entrance of NB. We hypothesize that these seasonally distinct P-n communities are responsible for low-level domoic acid production which likely contributed to the 2016 precautionary closure, while it appears a species new to NB, Pseudo-nitzschia australis, likely contributed to the 2017 closure. This map shows how cell-associated domoic acid increases and decreases over the sampling period. Sampling sites are shown with the concentration of domoic acid recorded on specific dates.

Impact

We hope this information will aid Rhode Island stakeholders by providing data following the 2016 and 2017 closures on when, where, and what concentration of low- level cell-associated domoic acid is present. This is important as domoic acid can bioaccumulate in shellfish and cause illness in humans when consumed. While cooking does not destroy the toxin, live shellfish can naturally purge the toxin with time and become safe for consumption later. These domoic acid measurements and P-n species composition provide baseline data during a period of no closures for important context if additional closures were to occur in the future.

Acknowledgments

Thanks to Dr. Tatiana Rynearson, Jacob Strock, Jessica Carney, Nina Santos, Captain Stephen Barber on the R/V Cap'n Bert, Dr. Harold “Bud” Vincent II on the R/V Hope Hudner, and Steve Granger on the R/V Zostera for assistance with sampling.

We thank graduate and undergraduate researchers and other research personnel Alexa Sterling, Riley Kirk, Katherine Bell, Dr. Laura Holland, Marissa Caponi, Meagan King, Emily McDermith, Erin Tully, Samantha Vaverka, Patrick Wilson, Stephanie Anderson, and Jorge Vazquez-Custodio for sampling assistance.

Learn More

The full dataset used to power this app is available on ERDDAP. If using this data, please cite the ERDDAP dataset.