PHYTOPLANKTON SEASONAL SUCCESSION IN THE ALBUFERA OF VALENCIA (SPAIN)

Abstract

A seasonal study of the phytoplanktonic communities in the Albufera of Valencia, an hypertrophic coastal lagoon, has been undertaken at the point of its maximum depth (3 m) along the vertical profile. The extreme eutrophy of the Albufera produces notoriously high phytoplanktonic densities; a summer maximum of 5,57 x 1012 individuals/m2 has been registered. The minimum density, five times lower (1,16 x 1012 ind/m2), occurs in winter. Cyanobacteria constitute the dominant phytoplanktonic group, reaching relative abundances above 96% in august, due mainly to species of the genera Lyngbya and Oscillatoria. The dominance of cyanobacteria is constant during the whole annual cycle constituing more than the 77% of the total phytoplankton, with the only exception of the month of april, in which a relative minimum of 41% was registered. Consequently, in this month, other algal groups reach their maximum representation, mainly chlorophyceae (35%), diatoms (16%) and cryptophyceae (4,2%). It is interesting to note the presence of Anabaenopsis circularis, a species of tropical distribution, whose growth in the Albufera has only recently been observed. All these results show that an important and recent change on the specific composition of the Albufera phytoplankton has occurred, due to its extreme eutrophication process.