Modification of the Berre Lagoon Pelagic Ecosystem Since the 1980s

Abstract

The Berre lagoon is a semi-enclosed basin Northeast of Marseilles (South of France) that has been largely impacted by human activities for several decades. The implantation in the northern part of the Saint Chamas power plant (deviation of the Durance River) in 1966 led to inputs from large freshwater bodies of water within this system. The lagoon communicates with the Mediterranean Sea through the canal of Caronte. Up to 2005, the inputs of freshwater were largely uncontrolled, leading to strong seasonal variations (2 to 4.10(9) m(-3). y(-1)) with minima observed in summer - early fall and maxima from fall through late spring. This led to important horizontal and vertical spatial as well as temporal variations in salinity, showing strong stratification taking place seasonally, particularly in the southern part where marine water forms the bottom layer. Since September 2005, inputs of freshwater have been modified following the EU's compulsory requirement to reduce salinity variations. This has resulted in strong modifications of the ecosystem, such as disappearance of abundant species (i.e., rotifers), introduction of several marine species/genuses (i.e., chaetognaths, ctenophores), and alteration of trophic level interactions.