Growth anomalies in Pecten maximus from coastal waters (Bay of Brest, France): relationship with diatom blooms

The aim of this study was to characterize the daily shell growth of Pecten maximus from early 1998 to late spring 1999 in the Bay of Brest with a care ful qualitative and quantitative description of the pelagic primary product ion. Our results, in accordance with previous studies, demonstrate that the re are episodic declines in the growth rate. Concurrent events of low growt h rate and large bottom-concentrations of algae following diatom blooms (Ce rataulina pelagica or Rhizosolenia delicatula), suggests that this high con centration of phytoplankton on the bottom layer may affect food intake or r espiratory activity of the scallops by gill clogging or oxygen depletion. I n this study, silicic acid or phosphorus are inferred to be limiting factor s responsible for the collapse of the spring bloom. Further, we suggest tha t, in an N-enriched ecosystem, Si or P-limitation and the changing sinking velocities of phytoplankton, could affect the biology of benthic suspension -feeders.