In estuaries, salty swamps and most of the brackish waters generally, the salinity can vary more or less quickly, as a result of the tide, of the pluviometry and of periods of sunshine. The species which live in these waters thus have to support variations of salinity. Some of these euryhaline species are met in sea (¨euryhaline marine species¨); others are present usually in freshwaters (¨euryhaline freshwater species¨); some ones (¨brackish species¨) are considered as limited to waters the salinity of which is situated between 0,5 and 30 %o. In addition, in samples collected in estuaries, stenohaline marine and freshwater diatom species are also found.

Estuaries and brackish waters in Southern brittany