DUGi

Phytoplankton Composition in Shallow Water Ecosystems: Influence of Environmental Gradients and Nutrient Availability

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@2072@@273639

Environmental gradients caused by hydrological changes, whether natural or maninduced,affect the planktonic taxonomic and functional composition in shallow waterecosystems. In this sense, our aim was to find out the main variables or variable ratiosthat are the driving forces of the major phytoplankton taxonomic groups inMediterranean coastal lagoons. For this purpose, 11 waterbodies were choosen, 6 ofthem in Empordà wetlands and 5 in the Doñana National Park, looking forrepresentative conditions along a gradient of salinity and nutrient content. Two surveyswere conducted in each waterbody (January and May 2007), after that thephytoplankton composition (chemotaxonomic composition) and also several physicaland chemical environmental variables were analyzed. Two methodological approacheswere used and compared: a first approach with a log (x+1) variable transformation and asecond one where variables were transformed using the compositional data analysis(CoDa) techniques introduced by Aitchison (1986). When the raw data approach andthe CoDa approach analysis (RDA) were compared, the results obtained were similarwith regard to explained variance and also interpretation. The CoDa approach wascharacterized by the introduction of a new environmental driving factor, the bacterialbiomass, whose ratio with the peptidase enzyme activity became significant. In thissense, the CoDa approach contributed to improving the biological interpretation of thephytoplankton distribution based on the raw analysis

Universitat de Girona. Departament d’Informàtica i Matemàtica Aplicada