Secondary production and calcification were then extrapolated to the whole Bay. D. arietina 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. Calcification rates calculated for the June 1994 to June 1995 time period are the highest ever reported for temperate benthic ecosystems.