Mussel biodeposition in an estuary in southern Chile

Abstract

Temporal variability in biodeposit production by Choromytilus chorus (Molina) and Mytilus chilensis (Hupe) was studied from February 1989 to January 1990 in the Queule River Estuary, southern Chile. Biodeposits were collected monthly from PVC cylinders containing C. chorus or M. chilensis and analyzed for total dry weight, inorganic and organic weight and organic carbon and nitrogen content. Water characteristics (temperature, salinity, oxygen, chlorophyll a, seston) were also measured at each sampling period. The highest biodeposition rates were calculated during spring and summer months; from October until January sedimentation and mussel biodeposition rates were similar. During this period the highest temperature and water salinities occurred, as well as one of the 2 chlorophyll a peaks observed during the study. The lowest biodeposition rates occurred during winter months, when temperature and water salinities were lowest and turbidity of the water was at its highest. Mean annual biodeposition rate of C. chorus was 271 g total dry weight (DW) m-2 d-1, with 212 and 59 g DW m-2 d-1 for the inorganic and organic fractions, respectively. Mean annual biodeposition of M. chilensis was 234 g total DW m-2 d-1, with 184 and 49 g DW m-2 d-1 for the inorganic and organic fractions. Mean annual sedimentation rate was 553 g total DW m-2 d-1, with 458 and 95 g DW m-2 d-1 for the inorganic and organic fractions, respectively. Biodeposits of C chorus averaged annually 6.4 % carbon and 0.3% nitrogen, with a C/N ratio of 40.8. Biodeposits of M chilensis averaged 6.0 % carbon and 0.4 % nitrogen, with a C/N ratio of 21.4. Naturally sedimented material averaged annually 5.5 % organic carbon and 0.5% organic nitrogen, with a C/N ratio of 13.6