Short-term dynamics of cladocerans in a eutrophic shallow lake during a shift in the phytoplankton dominance

Issue		Ann. Limnol. - Int. J. Lim. Volume 45, Number 4, 2009


Page(s)		237 - 245
DOI		10.1051/limn/2009027
Published online		29 October 2009

Ann. Limnol. - Int. J. Lim. 45 (4) 2009 : 237-245
DOI: 10.1051/limn/2009027

Short-term dynamics of cladocerans in a eutrophic shallow lake during a shift in the phytoplankton dominance

Nelson Abrantes, António Nogueira and Fernando Gonçalves

CESAM & Department of Environment, University of Aveiro, 3810-193 Aveiro, Portugal

njabrantes@ua.pt

Received 10 July 2009; Accepted 4 September 2009; Published online 29 October 2009

Abstract
The changes in the dynamics of cladocerans in Lake Vela (Portugal), as well as the morphologic and life history traits of the small-bodied cladoceran Ceriodaphnia pulchella, were studied intensively during one month characterized by deep and fast changes in the phytoplankton community: the beginning of the cyanobacteria dominance. Lake Vela, located in the Mediterranean region, is a polymictic shallow lake exhibiting characteristics typical of an advanced trophic status, namely the permanently turbid water, the reduction in biodiversity and the occurrence of cyanobacteria blooms. The density and composition of the cladocerans populations varied considerably during the short-term period analyzed. Coincident with the increase of cyanobacteria, the density of Daphnia longispina decreased drastically, associated with an increase of Bosmina longirostris and Chydorus sp. The constant density of C. pulchella, even during the cyanobacteria dominance, and the strong relationship found between weight and size, suggests that the low quality of phytoplanktonic food in Lake Vela did not play an important role in its fitness. Besides the small size of C. pulchella, this fact could be also related to its diversified diet. Nevertheless, a closer examination of the life history parameters of C. pulchella revealed a reduction in the fecundity, size at first reproduction, mean size of ovigerous females and maximum size of the population, which suggest an increase of the fish pressure after the decline of Daphnia. C. pulchella showed also a short-life cycle and a fast turnover of individuals, which constitutes also an advantage, allowing a fast adaptive response of the population.

Key words: Mediterranean shallow lakes -- short-term dynamics -- cladocerans -- cyanobacteria -- Ceriodaphnia pulchella

© EDP Sciences 2009

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