Increase of rotifer diversity after sewage diversion in the hypertrophic lagoon, Albufera of Valencia, Spain

The Albufera of Valencia is a large oligohaline hypertrophic lagoon, regulated by sluice gates according to the needs of the surrounding rice field cultivation. It is in a turbid state with permanent cyanobacterial blooms. A slight improvement was detected after diversion in the 1990s of part of the sewage flowing into it. After sewage diversion, we found that: (1) Chlorophyll concentration and rotifer densities decreased; (2) Rotifer proportions declined, due mainly to a relative increase in cladocerans; (3) Rotifer diversity increased. The two dominants of the 1980s, Polyarthra spp. in the colder period and Brachionus angularis in the warmer one, reverted after sewage diversion to a more …