Toxic Alexandrium blooms in the western Gulf of Maine: The plume advection hypothesis revisited

Abstract

The plume advection hypothesis links blooms of the toxic dinoflagellate Alexandrium fundyense in the western Gulf of Maine (GOM) to a buoyant plume derived from river outflows. This hypothesis was examined with cruise and moored-instrument observations in 1993 when levels of paralytic shellfish poisoning (PSP) toxins were high, and in 1994 when toxicity was low. A coupled physical-biological model simulated hydrography and A. fundyense distributions. Initial A. fundyense populations were restricted to low-salinity nearshore waters near Casco Bay, but also occurred in higher salinity waters along the plume boundary. This suggests two sources of cells-those from shallow-water cyst populations and those transported to shore from offshore blooms in the eastern segment of the Maine coastal current (EMCC). Observations confirm the role of the plume in A. fundyense transport and growth. Downwelling-favorable winds in 1993 transported the plume and its cells rapidly alongshore, enhancing toxicity and propagating PSP to the south. In 1994, sustained upwelling moved the plume offshore, resulting in low toxicity in intertidal shellfish. A. fundyense blooms were likely nutrient limited, leading to low growth rates and moderate cell abundances. These observations and mechanisms were reproduced by coupled physical-biological model simulations. The plume advection hypothesis provides a viable explanation for outbreaks of PSP in the western GOM, but should be refined to include two sources for cells that populate the plume and two major pathways for transport: one within the low-salinity plume and another where A. fundyense cells originating in the EMCC are transported along the outer boundary of the plume front with the western segment of the Maine coastal current.Toxic dinoflagellate blooms are a serious economic and

Interannual variability of Alexandrium fundyense abundance and shellfish toxicity in the Gulf of Maine

“…This is particularly surprising given the tremendous patchiness present in synoptic distributions of the organism (e.g. Townsend et al 2001;Anderson et al 2005). Perhaps the organism's life history strategy, including a resting cyst stage, lends intrinsic stability to the population on interannual to interdecadal time periods (Wyatt and Jenkinson, 1997).…”

Tracking of a Fluorescent Dye in a Freshwater Lake with an Unmanned Surface Vehicle and an Unmanned Aircraft System

“…The spread of hazardous agents such as radioactive particulates, oil, and harmful algal blooms have important economical [1], ecological [2], and national security [3] consequences. There are numerous mathematical models and methods for understanding and predicting how these agents are transported and dispersed, from ground water contamination to volcanic eruptions [4,5].…”

Mechanisms regulating large-scale seasonal fluctuations in Alexandrium fundyense populations in the Gulf of Maine: Results from a physical–biological model

“…By no means does this discount the potential importance of higher frequency and smaller scale phenomena in regulating blooms of A. fundyense in the Gulf of Maine. Indeed, synoptic-scale variability appears to play a role not only in regional bloom dynamics (Franks and Anderson, 1992ab;Keafer and Anderson, 1993;Anderson et al, 2005;Keafer et al, submitted;Luerssen et al, submitted), but also in determining mean properties of the system such as the cross-isobath transport of cells (Hetland et al, 2002;McGillicuddy et al, 2003). However, given the prominent aspects of the mean circulation in the Gulf of Maine (Bigelow, 1927), superposition of the mean physics with the mean biology constitutes a logical starting point for investigating the large-scale seasonal bloom dynamics.…”