Distribution of Eurytemora affinis (Poppe, 1880) (Copepoda: Calanoida) in the Schelde estuary (Belgium - The Netherlands): the effect of oxygen?
Appeltans, W. (2001). Distribution of Eurytemora affinis (Poppe, 1880) (Copepoda: Calanoida) in the Schelde estuary (Belgium - The Netherlands): the effect of oxygen? BSc Thesis. Free University of Brussels: Brussel. 15 pp.
E. affinis (Poppe, 1880) (Copepoda: Calanoida) is a dominant species in temperate estuaries. In most European estuaries this species peaks around 0-6 PSU. In the Schelde (Belgium/The Netherlands), the species was reported to be displaced to higher salinity (10 - 12 PSU) in the early nineties (Soetaert & Van Rijswijk, 1993). This displacement was explained as a consequence of too low oxygen concentrations at the optimum salinity zone. The oxygen concentration has improved in recent years, this study verified if this had any consequences for the distribution of E. affinis in the Schelde. Comparison of E. affinis abundance during spring at Bath (10 PSU) and at Antwerp (3 PSU), in 1990- '91 and 1996- '98 showed that the peak of the population has moved to Antwerp since 1996, and that its abundance at this station shows a significant correlation with oxygen concentration (spearmann rank, r = 0.665 ; p<0.05). Other ecological factors, potentially influencing the spatial distribution of the species such as suspended particulate matter concentration and the availability of phytoplankton food, are discussed. The observed changes in population abundance at different stations support the theory that E. affinis population moves actively within the estuary.
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