Suppression of the 2010 Alexandrium fundyense bloom by changes in physical, biological, and chemical properties of the Gulf of Maine

Abstract

For the period 2005–2009, the abundance of resting cysts in bottom sediments from the preceding fall was a first-order predictor of the overall severity of spring-summer blooms of Alexandrium fundyense in the western Gulf of Maine and southern New England. Cyst abundance off mid-coast Maine was significantly higher in fall 2009 than it was preceding a major regional bloom in 2005. A seasonal ensemble forecast was computed using a range of forcing conditions for the period 2004–2009, suggesting that a large bloom was likely in the western Gulf of Maine in 2010. This did not materialize, perhaps because environmental conditions in spring-summer 2010 were not favorable for growth of A.fundyense. Water mass anomalies indicate a regional-scale change in circulation with direct influence on A. fundyense’s niche. Specifically, near-surface waters were warmer, fresher, more stratified, and had lower nutrients than during the period of observations used to construct the ensemble forecast. Moreover, a weaker-than-normal coastal current lessened A. fundyense transport into the western Gulf of Maine and Massachusetts Bay. Satellite ocean color observations indicate the 2010 spring phytoplankton bloom was more intense than usual. Early-season nutrient depletion may have caused a temporal mismatch with A. fundyense’s endogenous clock that regulates the timing of cyst germination. These findings highlight the difficulties of ecological forecasting in a changing oceanographic environment, and underscore the need for a sustained observational network to drive such forecasts.

Alexandrium pacificum Litaker sp. nov (Group IV): Resting cyst distribution and toxin profile of vegetative cells in Bizerte Lagoon (Tunisia, Southern Mediterranean Sea)

“…On the northeastern coast of Britain, Alexandrium tamarense cyst accumulations in the Firth of Forth have also been linked to toxic blooms in the adjacent coastal waters (Lewis et al, 1995). Evidence for the existence of a regional seedbed has also been found in studies in the Gulf of Maine where a strong correlation between the abundance of A. fundyense cysts and the size of subsequent blooms has been documented (McGillicuddy et al, 2011). A similar link between cyst accumulations in lagoons, harbors, or other such sites has been found in the Mediterranean and has been responsible for localized blooms of A. pacificum in Thau Lagoon and Tarragona Harbor (Bravo et al, 2008) (Table 2).…”

Alexandrium catenella cyst dynamics in a coastal embayment : temperature dependence of dormancy, germination, and bloom Initiation

“…In both estuarine systems and in deeper coastal waters, discrete cyst seedbeds have been shown to provide the inoculum for A. catenella blooms . In some habitats, the size of the cyst seedbed and the timing of an extent of excystment can directly affect the magnitude of blooms (Wall 1971;McGillicuddy 2011;. Cyst seedbeds have obvious implications for the persistence of A. catenella -thus understanding temporal dynamics is important.…”

Improving the accuracy and utility of harmful algal bloom forecasting systems

“…Our approach to the forecasting (described in McGillicuddy et al 2011) generates estimates of regionwide Alexandrium cell abundance for the forthcoming bloom season, but does not yet project toxicity and shellfish closures along the coast. Press releases issued to describe the forecasts have used bloom descriptors that are relatively general (e.g., "severe", "moderate", "moderately large") and that therefore do not provide the type of information that the general public and resource managers would like.…”

“…As a result, models are being used to help extrapolate and interpret these sparse observations (Franks 1997;McGillicuddy et al 2011). These include conceptual models (e.g., Anderson et al 2005), empirical models (e.g., Blauw et al 2010;Raine et al 2010), and complex numerical models (e.g., He et al 2008).…”

“…This model has demonstrated good skill at reproducing observations He et al 2008) and has been heavily used for hindcasts (looking at past events to understand underlying mechanisms; He et al 2008;Li et al 2009). It is also being used to issue weekly nowcasts and forecasts (looking forward 3 or 4 days) and even seasonal or annual forecasts (McGillicuddy et al 2011). …”