Productivity, photosynthetic pigments and hydrology in the coastal front of the Eastern English Channel

In the French area of the Eastern English Channel, the coastalwaters 3 or 4 miles wide are separated from offshore watersby a coastal front. The phytoplanktonic biomass (B) and production(P) are higher in coastal waters, and an increase of biomasshas been observed at the interface. This frontal biomass, lessproductive, resulted from hydrodynamic accumulation, not dueto local growth. The productivity (P/B) deficit (50%) spreadsover the external area of the front, probably because the biomassis partly constituted of exported inactive coastal phytoplankton.The productivity is higher again in offshore waters. The variationof the pigment pool indicates a stress on phytoplankton in thefront and this ergocline was not productive at the time of thetwo cruises.