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 arietina 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 June 1994 and June 1996. Secondary production and calcification were then extrapolated to the whole Bay. D, anietina has a 2 yr life cycle with worms first reproducing when they are 1 yr old. Reproduction occurs during spring with several spawning peaks each year. Development is planktotrophic and the duration of the pelagic phase is close to 6 wk. Recruitment does not correlate 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 cycle. Density significantly decreased between 1996 and 1998. This pattern resulted from a strong recruitment in the whole bay during 1994, a weaker recruitment 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 periods, 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 June 1995 to June 1996 time periods, respectively. Calcification rates calculated for the June 1994 to June 1995 time period are the highest ever reported for temperate benthic ecosystems.