The EN476 coastal survey consisted of a series of transects spanning from just south of Boston to one off Mount Desert Island (see map). Surface live counts revealed low Alexandrium abundance south and west of Penobscot Bay, with cell concentrations at or below the limit of detection in that area. From Penobscot Bay to the east, cell concentrations are patchy, ranging from zero to 1201 cells per liter.
It is clear that model predictions of a larger-than-usual bloom in the western Gulf of Maine (WGOM) have not materialized thus far. We are currently investigating the causes of low Alexandrium abundance in the WGOM observed on OC460 and EN476. At this point it appears that hydrodynamic factors may have played a role, as two of the three surface drifters deployed off Casco Bay on OC460 have shown very modest along-shore transport in the month since their release on May 7 (see drifter figure). In addition, there is a distinct water mass anomaly in the deep and intermediate waters of the Gulf of Maine as compared with the major bloom that took place in 2008 (see GOM TS diagram). Deep waters are more than one degree warmer, and Maine Intermediate Waters are a few tenths of a degree warmer and a few tenths of a psu fresher than during this same time period in 2008. We are very eager to learn if there is a nutrient anomaly associated with the water mass anomaly, and how its near surface expression may have affected vegetative growth of Alexandrium. Dave Townsend’s lab will begin running the nutrient samples in the near future.
-on behalf of the EN476 science party