LE3 .A278 2000

2000

Daborn, Graham

Acadia University

Master of Science

Masters

Biology

Biology

While the ecology of the intertidal mudflats of the upper Bay of Fundy has been extensively studied during the warmer months of the year, the winter ecology remains largely unknown. Winter air temperatures average below 0C for several months of the year, and extensive amounts of sediment-laden ice are present on the mudflats and in the seawater during that time. Benthic macroinvertebrates, such as the amphipod 'Corophium volutator', are an important food source for millions of migrating shorebirds and fish in the summer. The question arises as to how these invertebrates survive the winter. In the winter and spring of 1996, I monitored environmental conditions and benthic invertebrate density in the upper intertidal zone at one Minas Basin mudflat, the Windsor mudflat, to gain an understanding of the winter conditions experienced by infauna and of the presumed recolonization of the mudflat in the spring. Hourly weather data and subsurface sediment temperatures at 15-min intervals were collected from late January to early June. Observations of ice on the mudflat were made periodically. Once the ice had disappeared from the mudflat in mid-March, weekly samples were taken for invertebrates and for chlorophyll 'a' (as a measure of abundance of the benthic diatoms which the invertebrates eat). The results indicated that although the air temperature can be substantially colder than the lethal temperature of the invertebrate macrofauna, the sediment temperature is not, which appears to be the result of insulation by ice in or on the sediment. However, the re-floating of ice which has frozen to the sediment may result in portions of the sediment surface and its infaunal inhabitants being removed. Invertebrate abundance patterns failed to reveal evidence of spring immigration. It appears likely that the infauna remain in place over the winter and that recruitment is by reproduction.

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