Population dynamics, secondary production and calcification in a Mediterranean population of Ditrupa arietina (Annelida : Polychaeta)

Temporal changes in the distribution of the serpulid polychaete Ditrupa ari etina in the Bay of Banyuls-sur-mer were monitored between January 1996 and January 1998. Life-history characteristics, population dynamics, secondary production and calcification were measured at a permanent site between Jun e 1994 and June 1996. Secondary production and calcification were then extr apolated to the whole Bay. D, anietina has a 2 yr life cycle with worms fir st reproducing when they are 1 yr old. Reproduction occurs during spring wi th several spawning peaks each year. Development is planktotrophic and the duration of the pelagic phase is close to 6 wk. Recruitment does not correl ate with larval supply due to high mortality rates during the first benthic stage. Mortality follows an exponential model. Growth is best described by a logistic model and is almost restricted to the first year of the life cy cle. Density significantly decreased between 1996 and 1998. This pattern re sulted from a strong recruitment in the whole bay during 1994, a weaker rec ruitment restricted to the deeper part of the bay during 1995, and a total absence of recruitment during both 1996 and 1997. Secondary production was between 0.4 and 295.9 g DW m(-2) yr(-1), and 0.1 and 12.3 g DW m(-2) yr(-1) , during the June 1994 to June 1995 and the June 1995 to June 1996 time per iods, respectively. Calcification was between 17 and 11836 g m(-2) yr(-1), and 2 and 397 g m(-2) yr(-1), during the June 1994 to June 1995 and the Jun e 1995 to June 1996 time periods, respectively. Calcification rates calcula ted for the June 1994 to June 1995 time period are the highest ever reporte d for temperate benthic ecosystems.