SECONDARY PRODUCTION OF CAPITELLA SP (POLYCHAETA, CAPITELLIDAE) INHABITING DIFFERENT ORGANICALLY ENRICHED ENVIRONMENTS

Three populations of Capitella sp. submitted to three different enviro nmental conditions were monitored during one year in Alfacs Bay (Ebro Delta, NW Mediterranean) to estimate their respective contributions to the secondary production. Yearly secondary production of Capitella sp . at the three sites under study were 0.83 gDW.m(-2).y(-1) for the dis turbed sand site, 3.74 gDW.m(-2).y(-1) for the typical silt site, and 36.9 BDW.m(-2).y(-1) for the disturbed silt site. The corresponding P/ B ratios were of 4.09 y(-1), 3.66 y(-1) and 5.71 y(-1), respectively. Ar the two silty sites, Capitella sp. presents: (1) a marked seasonal variability, and (2) high production rates and P/B ratios, which are t wo characteristics of opportunists. At the disturbed sand site its sea sonal pattern is much more stable; and its production much lower (alth ough P/B ratios are still high). The ''within site'' seasonal differen ces found between the three populations probably did nor result from t emporal changes in food quantity nor quality. Nevertheless, difference s in protein concentrations may contribute to explain differences in m aximal densities and biomasses observed among sites. Our results confi rm that Capitella sp. shows a great plasticity relative to environment .