JPR Advance Access published online on December 6, 2006
Journal of Plankton Research, doi:10.1093/plankt/fbl071
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research-article |
Effects of salinity and temperature on the post-embryonic development of Eurytemora affinis (Copepoda; Calanoida) from the Seine estuary: a laboratory study
a Ecosystem Complexity Research Group, Station Marine de Wimereux, Université des Sciences et Technologies de Lille, CNRS – UMR 8013 ELICO, 28 Avenue Foch, BP 80, F-62930 Wimereux France b Laboratoire d'Ecotoxicologie – Milieux Aquatique (LEMA), Faculté des Sciences et Techniques, Université du Havre - 76058 Le Havre Cedex - BP 540
* Corresponding author. Permanent address : Station Marine de Wimereux, 28 Avenue Foch, BP 80, F-62930 Wimereux France. Fax.: +33-321-992-901 Tel.: +33-321-992-926 E-mail address : sami.souissi{at}univ-lille1.fr
Received on January 10, 2006; revised on August 14, 2006; accepted on October 30, 2006
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Abstract |
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The species complex Eurytemora affinis is the most common calanoid copepod of northern-hemisphere estuaries. In the oligo- meso-haline zone (salinity 5-25) of the Seine estuary E. affinis reaches very high concentrations between March and June when temperature varies between 10°C and 15°C. To understand the population dynamics of E. affinis in the Seine estuary we investigated the effect of a combination of temperatures (10°C-15°C) and salinities (5, 15 and 25) on its post-embryonic development. To take into account the individual variability copepods were observed individually. Post-embryonic development time varies as a function of temperature and salinity and showed high individual variability. The increase of temperature from 10°C to 15°C deceased the mean post-embryonic development time from 24 days to 17 days. Increase in development time and mortality at salinity of 25 at both temperatures suggests that these conditions were the most stressful of those tested. No significant difference in development time or mortality was discerned between salinities of 5 and 15. In general mortality was higher for copepodid stages than for naupliar stages. The individual variability increased during the development and was also very high: some individuals develop faster at salinity 25 than others at salinities of 5 and 15. Moreover the distributions of the molting probability fitted well with a gamma density function, and thus we suggest this adjustment in models of population dynamics of copepods to tighter up the method of capturing individual variability. The population of E. affinis from the Seine estuary showed a faster development rate than conspecific populations from other estuaries at similar experimental temperatures and salinities. The responses of the post-embryonic development time to salinity and temperature show that E. affinis is well adapted to the low salinity zone of the estuary but can also survive at higher salinities.
Key Words: development rate • Eurytemora affinis • individual variability • mortality rate • salinity • Seine estuary • temperature