Instantaneous salinity reductions affect the survival and feeding rates of the co-occuring copepods Acartia tonsa Dana and A. clausi Giesbrecht differently
2008 (English)In: Journal of experimental marine biology and ecology, ISSN 0022-0981, Vol. 362, no 1, 18-25 p.Article in journal (Refereed) Published
Salinity variability at short time scales constitutes a severe restriction to marine life in coastal and estuarine ecosystems. In these environments zooplankters may experience rapid salinity variations due to diverse processes, yet lethal or sub-lethal responses to such changes have been scarcely studied. We assessed short-term (12 h) survival and time-integrated clearance (F; mL ind(-1) h(-1)) and ingestion rates (1, mu gC ind(-1) h(-1)) after 1, 2, 4, 8 and 12 h of two widespread and abundant coastal copepods, Acartia tonsa and A. clausi, subjected to instant salinity changes from 32 PSU to 26, 20,14, 8 and 4 PSU (A. tonsa) and from 32 to 26, 20 and 14 PSU (A. clausi). We expected that A. tonsa, which occur naturally in environments where sharp salinity gradients are common would tolerate wider salinity changes than A. clausi, which less frequently encounter sharp gradients in nature. For A. tonsa mortality for the extreme haline shock (change from 32 to 4 PSU) was 31%, whereas A. clausi reached 22% Mortality already at a change from 32 to 14 PSU; in comparison, mortality for A. tonsa at the 32/14 PSU treatment was only 3%. F and I decreased significantly at extreme treatments, and the total clearance in experimental bottles with salinity shocked animals (F-tot, mL h(-1)) was only 5% of rates measured in non-shocked control bottles for A. tonsa (32/4 PSU change) and 20% for A. clausi (32/14 PSU change); corresponding total ingestion (I-tot, mu gC h(-1)) represented 9.5% of that in control bottles for A. tonsa and 24% for A. clausi. In comparison, the 32/14 PSU treatment did not affect either clearance or ingestion rates in A. tonsa. Results suggest that in the field A. tonsa is not likely to suffer significant mortalities due to sudden salinity reductions in the Surrounding medium - except under extreme circumstances- while A. clausi cannot tolerate changes > 18 PSU. However, in both species feeding activity could be severely compromised by salinity reductions. The decreased feeding rate may have direct implications for processes ranging from energy acquisition at individual level to organic matter transfers at ecosystem level and thus deserves more attention in experimental studies and population modelling.
Place, publisher, year, edition, pages
2008. Vol. 362, no 1, 18-25 p.
IdentifiersURN: urn:nbn:se:su:diva-15601DOI: doi:10.1016/j.jembe.2008.05.005OAI: oai:DiVA.org:su-15601DiVA: diva2:182121
1. Univ Gothenburg, Kristinebergs Marina Forskningsstn, Dept Marine Ecol, S-45034 Fiskebackskil, Sweden
2. Univ Republica, Fac Ciencias, Secc Oceanol, Montevideo 11400, Uruguay
3. Stockholm Univ, Dept Syst Ecol, S-10691 Stockholm, Sweden2008-12-062008-12-062011-01-10Bibliographically approved