Chemical composition and biomass parameters of a population of Craspedacusta sowerbii Lank1880 (Cnidaria: Limnomedusa)

Until now, very little information about the ecology of the freshwater jellyfish, Craspedacusta sowerbii, has been available. Although many publications deal with Craspedacusta, most of them contain only observations. Detailed analyses are rare. In this study, investigations on size-dependent fresh and dry weights, and carbon, nitrogen and phosphorus, are presented. The water content of the medusae ranged between 96.74 and 99.87%. Fresh and dry weights ranged from 0.06 to 331.86 mg FW ind.(-1) and 0.01 to 2.50 mg DW ind.(-1), respectively. The molar C:N:P relationship was calculated as 39:9:1. The C:P ratio was low in contrast to other freshwater zooplankton species, and implied a high demand for P. A comparison with the C:P stoichiometry of their prey indicates the possibility of P limitation of Craspedacusta at a gross growth efficiency above 25%. The results are discussed in relation to medusae abundance, bioaccumulation and their impact on food web structure.