Pseudo-nitzschia bloom dynamics in the Gulf of Maine: 2012-2016
Suzanna Clark, Massachusetts Institute of Technology, Cambridge, United States; Woods Hole Oceanographic Institution, Woods Hole, MA, United States, Katherine Hubbard, Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Saint Petersburg, United States, Donald M Anderson, Woods Hole Oceanographic Institution, Biology, Woods Hole, MA, United States, Dennis Joseph McGillicuddy Jr, Woods Hole Oeanographic Institution, Woods Hole, MA, United States, David K Ralston, WHOI, Department of Applied Ocean Physics & Engineering, Woods Hole, United States and David W Townsend, University of Maine, School of Marine Sciences, Orono, ME, United States
Abstract:
The toxic diatom genus
Pseudo-nitzschia is a growing presence in the Gulf of Maine (GOM), where regionally unprecedented levels of domoic acid (DA) in 2016 led to the first Amnesic Shellfish Poisoning closures in the region. Factors driving GOM
Pseudo-nitzschia dynamics, DA concentrations, and the 2016 event were explored with data from four offshore oceanographic surveys in the GOM (summer 2012, 2014, and 2015, and fall 2016), and surface water samples from a weekly time series in 2013. Samples were processed for particulate DA (pDA), dissolved nutrients (nitrate, ammonium, silicic acid, and phosphate), cellular abundance, and species composition (estimated via Automated Ribosomal Intergenic Spacer Analysis). Temperature and salinity data were obtained from measurements during the surveys and NERACOOS buoys.
Pseudo-nitzschia biogeography was consistent in the years 2012, 2014, and 2015, with greater Pseudo-nitzschia cell abundance and P. plurisecta dominance in low-salinity inshore samples, and lower Pseudo-nitzschia cell abundance and P. delicatissima and P. seriata dominance in high-salinity offshore samples. During the 2016 event, pDA concentrations were an order of magnitude higher than in previous years, and inshore-offshore contrasts in biogeography were weak, with P. australis present in every sample. Statistical analysis confirmed that pDA increased with the abundance and the cellular DA of Pseudo-nitzschia species, but was not correlated with any one environmental factor. The greater pDA in 2016 was caused by P. australis – the observation of which is unprecedented in the region – and may have been exacerbated by low residual silicic acid.
It is hypothesized that P. australis was introduced to the GOM with an anomalous water mass. This hypothesis is being tested with a Lagrangian particle tracking model and hindcasts from the Regional Ocean Modeling System (ROMS) in 2012 – 2016.
Funded by NSF and NIEH
