C.4 Objectives

We propose a multi-disciplinary, multi-year field and modeling program to investigate the ecology and oceanography of toxic Alexandrium blooms in the GOM. This program has been designed to address the autecology of Alexandrium cells, their transport pathways and physical environment, and the fate of their toxins within the food web. A series of oceanographic surveys, process studies, and a set of laboratory experiments will address the PSP problem on a scale that is ambitious but necessary given the extent of coastline affected and the distinct habitats in which Alexandrium occurs.

The overall goal of ECOHAB-GOM is to understand and model the dynamics of the toxic dinoflagellate Alexandrium in the Gulf of Maine by investigating the physical, biological, chemical, and behavioral mechanisms underlying population abundance and distribution in several key habitats or regimes and by characterizing the transport pathways that link them.

Specific objectives are to:

1) Determine how hydrodynamic, chemical, and biological processes and conditions in the "source region" of Casco Bay affect the structure and scale of WMCC Alexandrium populations.

2) Investigate the small scale physical, biological and chemical processes that control the evolution and fate of patches of Alexandrium cells that are entrained into and transported by the WMCC.

3) Determine the biological and hydrodynamic mechanisms that result in late-season maintenance and retention of Alexandrium cells in the WMCC region and which re-seed the area with cysts that represent the inoculum for blooms in future years.

4) Investigate the hydrography and nutrient chemistry of the EMCC and identify the factors that regulate Alexandrium population dynamics in those waters.

5) Determine the linkages between the EMCC and WMCC and between the EMCC and the Bay of Fundy with respect to freshwater, nutrients, and Alexandrium cells.

6) Investigate linkages between PSP on Georges Bank and Alexandrium populations in the EMCC and WMCC.

7) Determine the distribution and abundance of Alexandrium cysts in the EMCC and WMCC regions, and estimate the timing, rate and magnitude of germination as an inoculum for bloom initiation. 8) Estimate the impact of grazing on Alexandrium populations in the EMCC and WMCC, and determine the extent to which toxins are partitioned within the marine planktonic food web.

9) Develop a suite of multiscale nested circulation models to produce realistic four dimensional environmental fields into which relevant biological processes will be incorporated. This set of coupled models will be used to: (a) dynamically interpolate data from the observational network; (b) expose the underlying physical-biological interactions that control Alexandrium populations; (3) provide a basis for simpler predictive models of PSP toxicity that can be driven by a relatively small number of readily observable variables.