Seasonal and spatial distribution of planktonic crustacea in the lower Saint John River,a multibasin estuary in New Brunswick,Canada |
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| Authors: | J C H Carter M J Dadswell |
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| Institution: | 1. Department of Biology, University of Waterloo, N2L 3G1, Waterloo, Ontario, Canada
2. Department of Fisheries and Oceans Biological Station, Fisheries and Environmental Sciences, E0G 2X0, St. Andrews, New Brunswick, Canada
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| Abstract: | Five stations on the lower Saint John River, a complex multibasin estuary, were sampled semiquantitatively for zooplankton at biweekly intervals for one year, and qualitatively over a 4-year period. Planktonic Crustacea were dominated by the true estuarine copepods,Acartia tonsa andEurytemora affinis and the euryhaline marine copepodsOithona similis andPseudocalanus minutus. Atypical estuarine forms, confined to a lower fiord-like basin with salinity of 20‰, were the amphipod,Parathemisto abyssorum and the mysidErythrops erythrophthalma. River flows were highly variable from year to year. Certain basins function as lakes in some years and estuaries in other years, causing extreme zooplankton community fluctuations, and succession patterns dependent on salinity rather than season. On occasion freshwater zooplankters maintained viable populations at unusually high salinities (ca. 5‰). Vertical and horizontal distributions of zooplankters indicate that the estuary in fact comprises two systems: a true estuary in the upper reaches and the surface waters at the lower end, and a fiord in a subsidiary basin in the lower end. |
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