C.5.2 Program elements. The rationale and approach of the major program elements are described below. Additional information is posted on the ECOHAB-Gulf of Maine web page (http://crusty.er.usgs.gov/ecohab/) for reviewers interested in non-essential details that cannot be provided here. For convenience, the rationale, approach, and methods of the major program elements will be highlighted below, with a listing of the responsible PIs.

C.5.2.1 Field Observations of Alexandrium Distribution and Transport

Rationale: A key objective of ECOHAB-GOM is to understand the effects of physical processes on Alexandrium distributions at several scales, including the Gulf-wide scale, the regional scale, and the smallest scales in which localized blooms of cells develop or aggregate. Our observations and modeling will employ a nested approach, with overlapping grids of varying resolution and spatial coverage, in order to resolve at the same time the small-scale physical-biological interactions responsible for the initiation and cessation of blooms, the transport processes linking source regions with the major current systems, and the large-scale physical coupling between the different populations of Alexandrium within the GOM. The range of scales is so large that models are required for analysis and hypothesis testing, but they only provide meaningful information in the context of a well-designed observational effort. Moored measurements will quantify transport processes in the Gulf, providing information about the coupling between the regions as well as the response to local forcing. Shipboard observations of physical properties and Alexandrium cells will cover several different scales, including broad-scale surveys that link the western and eastern Gulf, as well as repeated, high-resolution surveys within the EMCC and WMCC to identify population structure and variability and to evaluate the physical-biological interactions. Because of our prior knowledge of the WMCC population, this portion of the study will focus on linking the dynamics of the source region in Casco Bay to the regional distribution of Alexandrium. The EMCC study will start by characterizing the regional distribution of cells, following with a detailed examination of the mechanisms responsible for growth, maintenance, and delivery to shellfish. Process studies will explore the detailed biological-physical interactions in both regions in the latter portion of the program. The Georges Bank region will be included in the large-scale modeling studies and will be sampled for shellfish toxicity, but will not be included in the physical-biological field investigations.

Approach: Moored Measurements (PIs: Signell, Pettigrew, Geyer). Eight moorings will be deployed during Years 1 and 3, three in the Casco Bay region and five in the larger-scale Gulf of Maine region (Fig. 5). Deployment will be in February/March and recovery during August. In Jordan Basin, bottom pressures and a 6 element chain of SeaCats at 5, 10, 25, 50, 100 and 200 m will allow geostrophic volume transports to be estimated in the principal inflow region along the Scotian shelf. With the exception of this mooring in Jordan Basin, all others will sample surface layer and lower layer velocities, temperature and salinity. The Casco Bay mooring will also measure surface and bottom turbidity and surface wave intensity to document sediment resuspension events relevant to the transport of cysts. At 4 of the moorings (2 in EMCC, 1 off Nova Scotia and 1 off the Kennebec) Acoustic Doppler Current Profilers (ADCPs) will provide high vertical resolution of currents (every few meters) through the water column. The other moorings will include a vector-measuring current meter (VMCM) at 5 m and vector-averaging current meters (VACMs) at 25 m depth (near the base of the pycnocline) and in near-bottom waters. The VACMs will include conductivity and temperature sensors, and SeaCat instruments will be deployed adjacent to the VMCMs to provide salinity and temperature data at 5 m depth. SeaCats will also be deployed at 5 and 25 m at the locations of the ADCPs. The instruments will sample at 7.5 to 10 minute intervals. This mooring configuration was effective in resolving the vertical structure of the WMCC plume (Geyer et al., submitted ms.).

DuringYear 4 process studies, a limited array of moorings will be deployed to provide information in regions of particular relevance to Alexandrium transport. In the WMCC region, the Casco Bay mooring and the adjacent ADCP mooring will be redeployed, and in the EMCC region, a three-mooring array will be deployed in the region southwest of Grand Manan Island to address the linkage between southwestern Fundy, the EMCC, and the nearshore region of the downeast coast.

Shipboard Studies, Western Gulf (PIs: Anderson, Keafer, Geyer, Churchill, Loder, Doucette, Turner): The WMCC study encompasses three interconnected sub-regions (Fig. 4D): the individual embayments or sounds in which blooms are initiated, the semi-enclosed waters of Casco Bay, and the adjacent coastal current. Exchange rates must be quantified in the embayments that accumulate Alexandrium, and the transport mechanisms and timing between those sites and Casco Bay must be determined. Finally, the transport between Casco Bay and the coastal current has to be quantified.

Bi-weekly shipboard sampling during the WMCC bloom season (April-June) in Years 1 and 3 will be along 6 transects extending 20 km offshore of Casco Bay (Fig. 4D), each with 6-10 stations where vertical profiles of water properties, nutrients, light transmission, current velocity, in situ fluorescence and Alexandrium cells will be obtained at surface, 3.5, 7, and 10m with a fully instrumented rosette. The top 3 samples will be combined to give one "surface layer" measure. The 10m sample will be archived and test counts made to justify additional counting. Ten years of experience has shown us that discrete depth sampling is questionable with 12-hr surveys of a vertically migrating organism. At select stations, however, (Fig. 4D), vertical profiles of cells and nutrients will be taken. During Year 3, several tidal cycle surveys with shipboard ADCP, CTD, and Alexandrium cell collection will be performed in critical regions that link the source populations to the WMCC. Ten satellite-tracked surface drifters (Davis, 1985) will be released in the source region in Year 3 to provide additional insight into the linkage between the nearshore waters and the coastal current.

Cells will be counted using a new immunological procedure which reduces the chance of misidentification, especially when the Alexandrium population is low. An Alexandrium-specific monoclonal antibody probe (the producing M8751-1 hybridoma is maintained in the Anderson lab) will be used in a whole cell, indirect immunofluorescent format (Anderson et al. 1993). This technique has replaced standard counting by light microscopy in the Anderson lab. Modification of this procedure to an ELISA format is under development and may be ready for use at the time of the field programs (Anderson, unpub. data). Samples can then be processed in 96-well plates with quantitation by an automated plate reader - increasing sample throughput by an order of magnitude.

Another new technology to be tested uses an rRNA probe developed by Scholin and Anderson (unpub. data) and applied in a "sandwich" assay (Scholin et al, in press). The Alexandrium probe is not commercially available, but we have ample supplies (WHOI holds the patent). We will use this probe in automated fashion for "real-time" detection of Alexandrium when time is critical, such as in locating the patch to be drogued for the Year 4 process study. There are serious problems to be resolved with respect to cell quantitation (Anderson et al. 1997), however, so we consider it premature to rely heavily on the rRNA probe for routine cell counts.

Another technology to be explored is based on our view that HABs and their toxins will someday be monitored with moored instruments that filter water and detect cells or their toxins. This project offers a superb opportunity to compare traditional cell counts with measures of total particulate toxin in a water sample. Accordingly, for every cell sample taken for this project, 5 liters of water will be filtered and the collected material analyzed for toxins using the receptor binding assay (Doucette et al. in press). Toxin distributions will be mapped and compared to cell distributions. These data will indicate whether toxin per cell of Alexandrium remains constant in time and space, and whether automated detection of toxin or cells by moored sensors will provide adequate protection.

Shipboard Studies, Eastern Gulf (PIs: Townsend, Loder, Pettigrew, Keller): The objectives of the shipboard studies in the EMCC region are to: 1) characterize the hydrographic and circulation fields on the southwest Scotian Shelf, in southwestern Bay of Fundy, and on the eastern Maine shelf, 2) characterize volume transports, nutrient fluxes, and Alexandrium dynamics, 3) determine the physical linkages between the southwest Scotian Shelf, the southwestern Bay of Fundy, the EMCC, and the eastern Maine nearshore environment, and the WMCC. The observational approach relies heavily on shipboard observations, moored data, meteorological measurements, and satellite-tracked drifters.

Three 12-day cruises are planned (June, July, August). Each survey will have three legs: an east to west leg sampling inner shelf stations, a return leg sampling the offshore boundary for modeling purposes, and another west to east inner shelf sampling leg. Stations are shown in Fig. 5. The 6-7 day timescale between survey legs is short enough that physical and biological features within the domain (such as bloom patches) may retain their identity, as found in a similar survey strategy in the 1993-94 WMCC studies (Geyer et al., submitted ms.. Anderson, unpub. data). Five ARGOS-tracked drifters will be released at the upstream end of the EMCC and recovered on the second leg of the survey. ADCP measurements will provide vertical shear and possibly tidal and residual in conjunction with the moored time series measurements. Other methods for cells, nutrients, zooplankton, etc. are the same as those described for the WMCC.