Changes of life-history traits and size in Daphnia magna during a clear-water phase in a hypertrophic lagoon (Albufera of Valencia, Spain)

The rol.e o.flarge her?ivorous zooplankton, especially Dap~ma, m promotmg clear-water phases due to its grazmg effeet on phyroplankton is well doeumented (SoMMER et al. 1986, CARPENTER & KlTCHNEL 1996). The PGE model of plankton sueeession (SOMMER et al. 1986) deseribes both the produetion of the clear-water phase (CWP) and its decline. The latter results from two main meehanisms: (l) that the herbivorous woplankton beeomes food limited due to overpopulation, and (2) that fish predation a~eelerates ~e decline of the large woplankton speeJes. The aJm of the present study was to examine the ~opulati~n dynam!cs of Daphnia magna that eontnb~ted m produemg a CWP in the hypereutrophie shallow lake, Albufera ofValencia. Due to the high trophie level of the lake and the drastie ehanges that happen during this clear-water episode, the data presented herein clearly illustrate the operadon of the aforementioned meehanisms during the CWP and how they affeet the size strueture and lifehistory traits of the D. magna population.