Hydrography and Phytoplankton Biomass in the Eastern English Channel in Spring 1992

The coastal water in the Eastern English Channel, named ‘ fleuve côtier ’ (FC) between the River Seine and the Cape Gris-Nez, is a low-salinity water mass because of the integrated continental runoffs. This coastal water is often limited seaward by coastal front(s) and is characterized as a transfer pathway from the English Channel to the North Sea. The results of this study show that the phytoplankton production start is located off the Seine and Somme Estuaries, and the phytoplanktonic production is lower in the deep and turbulent waters off the Pays-de-Caux, in spite of their nutrient richness. The dispersion of the nearshore produced biomass is often seaward-limited by the coastal front. Nevertheless, the system is complex and the overall biomass distribution is not always limited by the front because production exists offshore of the front. The production seems limited by the depth (20–25 m) independently of the FC structure. In fact, the FC itself appears neither sufficient nor indispensable to develop the phytoplanktonic production in the Eastern English Channel. The broad Picardy Bay, including a part of FC and offshore water, is revealed as an isolated phytoplanktonic system.