Project: RI Sound as a potential source of HAB toxins for Narragansett Bay

Award Abstract:

In fall 2016, Narragansett Bay (NB) and Rhode Island Sound (RIS) experienced a significant planktonic bloom of toxin producing Pseudo-nitzschia spp. that led to closures of shellfish harvesting. The bloom occurred primarily in mid and lower NB with its longest duration in RIS. Shellfish managers raised the possibility that the source of this harmful algal bloom (HAB) was outside of the local region.

The main objective of this proposal is to determine the potential for intrusions of RIS water to carry harmful algae into NB. The emphasis will be on Pseudo-nitzschia spp. and the neurotoxin domoic acid (DA), but with collection of data on Alexandrium and Dinophysis abundance as well. We propose to 1) seek the most appropriate sentinel station in RIS to measure water properties and toxins in shellfish in waters prone to intrusions into NB, 2) establish the occurrence, abundance, and distribution of the three phytoplankton species in relation to physical parameters within RIS and lower NB, 3) relate domoic acid uptake in blue mussels (Mytilus edulis) with Pseudo-nitzschia abundance and toxin content, and with environmental variables toward improved management of shellfish resources.

We propose to first optimize the location of a sentinel mooring for HAB detection near the mouth of NB by using passive particle-tracking methods with realistic model circulation fields. Subsequently, at the selected sentinel site location between June and November, we will monitor currents and water column properties using an ADCP mounted on the sea floor and a moored string of CTDs distributed over the full water depth to characterize surface temperature and vertical stratification during Pseudo-nitzschia blooms. We will profile the water column and collect phytoplankton for species enumeration and identification on a bi-weekly basis at the sentinel station as well as at eight sites around lower NB. Mussels will be suspended at the sentinel stations and one station in NB to monitor DA uptake monthly. Wild mussels at five sites will be monitored for toxin content.

This approach will help determine the abundance and distribution of three HAB species in relation to physical parameters within RIS and lower NB, and define whether HAB species are introduced into NB from RIS or whether they develop into blooms from already established populations.