Estimation of food demands of Aurelia aurita medusae populations in the Kiel Bight/Western Baltic

Abstract

Using previously published data on respiration, body growth and reproduction, the food demands of the Kiel Bight Aurelia aurita populations in 1982 and 1983 were estimated according to the carbon budget approach. In 1982, medusae abundance and biomass were high and food demands accounted for 37 g C 100 m^-3 season^-1, whereas in 1983 a low Aurelia stock was associated with a food demand of only 7 g C 100 m^-3 season^-1. On average, medusae consumption made up roughly 40% and 8% of summer secondary production in 1982 and 1983, respectively. A comparison of Aurelia biomass values determined during six years revealed that the conditions in 1983 are typical for Kiel Bight, whereas in 1982 exceptionally high biomass and feeding rates were observed. It is therefore concluded that grazing impact of medusae is of comparatively low importance in most years.