J. L. Martin¹, F.H. Page², A. Hanke², M.M. LeGresley¹ and M. Dowd², Biological Station, Fisheries & Oceans Canada, 531 Brandy Cove Road, St. Andrews, NB, CANADA E5B 2L9, E-mail: martinjl@mar.dfo-mpo.gc.ca

Abstract

Phytoplankton samples have been collected since 1988 at 4 stations (inshore and offshore) in the western Bay of Fundy, eastern Canada. Water samples for phytoplankton enumeration and community structure were settled in Zeiss counting chambers and cells greater than 5 µm were enumerated as cells (organisms) L^-1 using a Nikon inverted microscope. The dataset has been examined from several perspectives including that of annual timing of blooms. When cumulative cell counts within each year were calculated, beginning in January, the cumulative curves indicated that the annual increase in diatom abundance began around day 110 (early April) and reached 50% of its annual total betwe#ffffff">en days 150 and 250 (late May - early September) and had returned to background levels around day 275 (October 1). Cumulative curves for total dinoflagellates showed the annual increase was around day 150 (late May) - around 40 days later that the diatom increase. The range in median day for the dinoflagellates was narrower than diatoms - between days 210 and 230 (late July - mid August). Results indicate that there has been no significant interannual variability in the amplitude and phase of the dinoflagellate abundance cycle.

Alexandrium spp blooms occur annually between late May - August with highest concentrations observed during most years during the period July 9-21. During the period 1997-2000, concentrations were less that 1.0 X 10⁴ cells L^-1, which resulted in shellfish toxicity, but at levels below those observed during most years. Highest concentrations since 1988 were observed in 1989 with 1.62 X 10⁵ cells L^-1.

Domoic acid production has been associated with Pseudo-nitzschia pseudodelicatissima in the Bay of Fundy and generally requires more than one million chains of cells L to be in the water in order for shellfish to become toxic above the regulatory level. Blooms tend to occur during late summer with highest concentrations observed during 1988 and 1995, during late August/ early September.

This dataset represents more than 70,000 records between 1988 and 2001. Future plans include further refining and quality control and exploring the temporal and spatial variability in the patterns more fully. Statistical methods will be applied for comparisons of the cumulative frequency curves between years and locations to detect significant time patterns in inter-annual variability, for detecting patterns in community structure (including HABs) for exploring potential associations between species abundance and environmental patterns.