Tuesday, June 5, 2007

Factors affecting the periphytic diatom community in Mediterranean coastal wetlands

Rosa Trobajo1, Xavier Quintana2, Eileen J. Cox3, and Carles Ibanez3. (1) Aquatic Ecosystems Unit, Crta de Poble Nou s/n, Apartat de Correus 200, 43540- Sant Carles de la Rapita, Spain, (2) Institute of Aquatic Ecology, University of Girona, Campus de Montilivi, 17071-Girona, Spain, (3) Department of Botany, The Natural History Museum, Cromwell Road, London SW7 5BD, England

The factors that determine the species composition and distribution patter of periphytic diatom species of lentic and fluctuating coastal waters (Empordà wetlands, NE Spain) were studied. A total of 165 taxa have been identified, 17% of which are new citation for the Iberian Peninsula. 84.69% of the individuals counted belong to the genera of Cocconeis (Cocconeis placentula), Nitzschia, Navicula and Amphora genera. Among them, Nitzschia is the genus represented by the highest number of taxa. Most of the periphytic diatom species occurring in the salt marshes of Empordà wetlands are change-tolerant of many environmental variables such as salinity, temperature and nutrients. The factors that determine the diatom species composition and distribution are factors directly involved in the flux of system energy like confinement and productivity. Based on confinement and productivity 5 diatom assemblages have been distinguished. The morphological plasticity of one of the most dominant taxa (Nitzschia frustulum) will be also empathised since experimental studies showed the effect of three environmental variables (salinity, nutrients and water morphology) on the valve morphology of N. frustulum.

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