SLS - Suzi Clark

Suzi Clark
Wednesday, February 3, 2021 - 12:00pm to 1:00pm

Title: Investigating Harmful Algal Blooms in the Gulf of Maine with Observations and Models


The toxic diatom genus Pseudo-nitzschiais a growing presence in the Gulf of Maine (GOM), where regionallyunprecedented levels of domoic acid (DA) in 2016 led to thefirstDA-induced shellfishery closuresin theregion. However, factors driving the 2016 event and Pseudo-nitzschia dynamics areunclear.In the first part of this talk, Pseudo-nitzschiabloom dynamics before and duringthe 2016 eventare investigated withobservations. Water sampleswere processed for particulate DA,temperature, salinity, nutrients, cell abundance, and Pseudo-nitzschia DNA.DA concentrations increased with Pseudo-nitzschia abundance but werenot correlated with any environmental factor. The high DA concentrations in 2016 were caused primarily byP. australis, which was observed for the first time in the region.However,environmental factorswerenotsignificantly different from previous years, suggesting the introduction of P. australis on an anomalous water mass.In the second part of the talk, a hydrodynamic model and Lagrangian particle tracking modelare used to test the introduction hypothesis.Based on particle tracking experiments, the most likely source of P. australisto the Gulfof Maine was the Scotian Shelf. However, in 2016, connectivity between the bloom region and the Scotian Shelf was not significantly different from other years, nor were temperature conditions more favorable for P. australisgrowth. Observations indicated that decreased surface salinity on the Scotian Shelf in 2016 preceded the introduction of P. australis. Thissuggests that the 2016 event was the result of changes in upstream water masses, either as increased influence of the Labrador Current or increasedoutflow from the Gulf of St. Lawrence, which could have acted as conduits connecting distant P. australispopulations to the region. Continued and increased monitoring is warranted to track interannual Pseudo-nitzschia persistence in the Gulf of Maine.

About this Series

The Atmosphere, Ocean and Climate Sack Lunch Seminar Series is an informal seminar series within PAOC that focuses on more specialized topics than the PAOC Colloquium. Seminar topics include all research concerning the science of atmosphere, ocean and climate. The seminars usually take place on Wednesdays from 12-1pm in 54-915. The presentations are either given by an invited speaker or by a member of PAOC and can focus on new research or discussion of a paper of particular interest.