Seasonal changes of macrozooplankton and Benthic Boundary layer macrofaunafrom the Bay of Saint-Brieuc (western English Channel)

The macrozooplankton and Benthic Boundary Layer (BBL) macrofauna over a coa rse sand and pebble community in the Bay of Saint-Brieuc (western English C hannel) were sampled with a WP2 zooplankton net and with a modified MACER-G IROQ suprabenthic sledge, respectively, from February 1994 to November 1995 . One hundred and sixty-four species were collected in in 44 suprabenthic s ledge hauls and 19 taxa in 30 zooplankton net hauls. In the water column, a ppendicularians and cnidarians dominated, while, in the BBL, holoplanktonic amphipods, chaetognaths, amphipods and mysids dominated the fauna; among t hem Apherusa spp., Sagitta setosa Muller, Anchialina agilis (Sars), Siriell a clausii Sars and Eusirus longipes Boeck were the dominant species. The de nsity and biomass of the BBL macrozooplankton were lower than those of the macrozooplankton in the water column. The density and biomass of suprabenth os remained low throughout the year. In the water column, density and bioma ss of macrozooplankton showed a maximum in spring and remained low from aut umn to winter; conversely, in the BBL, the density and biomass of both macr ozooplankton and suprabenthos were higher from summer to autumn. The change in abundance of both BBL and pelagic taxa was seasonal. Some species were primarily sampled in the water column (appendicularians, cladocerans and cn idarians), while others were preferentially found at the BBL (suprabenthic species, holoplanktonic amphipods and cephalopods). A third group was colle cted throughout the water column (chaetognaths and fish larvae).