Temporal changes of cyanobacteria in the largest coastal Spanish Lake
Villena, María-José; Romo, Susana
published: Aug 1, 2003
ArtNo. ESP142014800030, Price: 29.00 €
In this work, we will present long-term changes of cyanobacteria in the largest coastal, shallow, Spanish freshwater lake (the Albufera of Valencia). The lake is used as a reservoir for rice cultivation in the sorrounded lake area. The Albufera lake was in a mesotrophic state during the first half of the 20th century and at the end of 1960s, due to eutrophication, it rapidly turned into an eutrophic state with loss of submerged macrophytes and general biodiversity in the plankton, benthos and fish populations, that remains until now. Since the beginning of the century, cyanobacteria were represented in the phytoplankton of the lake, but from 1970s to 2000 became the dominant group. A total of 26 cyanobacteria species have been described between 1942 and 2000. Morphological and phenological features of the species are shortly reported in this study. Since 1991, a restoration plan of the lake started by sewage water diversion, that has reduced to half planktic chlorophyll a concentrations, although hypertrophic levels persist. Some alternative clear water phases appeared in which cyanobacteria contribution was reduced from 50-90 % to less 5 %. After nutrient diversion also a shift in cyanobacteria composition was observed. Large oligophotic filamentous species (mainly Planktothrix agardhii) were replaced by slender filamentous species (mainly Pseudanabaena galeata, Planktolyngbya contorta, Pl. limnetica and Jaaginema cf metaphyticum) and chroococcals (Chroococcus dispersus, Ch. minutus and Aphanocapsa incerta). Water stability, filament resuspension from the sediment, turbidity and benthic-planktivorous fish, were mechanisms stabilizing cyanobacteria dominance in the lake, while high flushing, nutrient depletion and increase of underwater light destabilized or prompted changes in the cyanobacteria community.