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- Title
Population dynamics and zooplankton-predation impact of the indigenous scyphozoan Aurelia aurita and the invasive ctenophore Mnemiopsis leidyi in Limfjorden (Denmark).
- Authors
Riisgård, Hans Ulrik; Madsen, Caroline V.; Barth-Jensen, Coralie; Purcell, Jennifer E.
- Abstract
The invasive ctenophore, Mnemiopsis leidyi, which had its first mass occurrence in Limfjorden (Denmark) in 2007, and the indigenous common jellyfish, Aurelia aurita, were studied from autumn 2008 through summer 2009. By December 2008, both A. aurita and M. leidyi populations had disappeared for the winter. In 2009, the first A. aurita appeared in February and the medusae attained their maximum umbrella diameter by the end of June, when the estimated half-life of copepods was only 1.6 ± 1.1 d. Low densities of M. leidyi in early July (< 0.5 m-3) increased to high densities by late August (66.2 to 224.9 ind. m-3). In 2009, the estimated time to clear the central part of Limfjorden (Skive Fjord) of zooplankton by A. aurita and M. leidyi feeding was between 0.5 d (4 June) and 2.9 d (26 August). During that period, copepods and other mesozooplankton organisms were virtually absent while ciliates were a substantial part of the zooplankton biomass. In "pre-Mnemiopsis years", there seems to have been large variability in the grazing impact on zooplankton depending on the seasonal abundance of A. aurita. With the addition of the second carnivore M. leidyi, however, additional predation pressure caused the zooplankton stocks to be severely depressed throughout 2008 and 2009 when copepods and cladocerans no longer showed the high seasonal peaks in abundance typical of previous years.
- Subjects
CTENOPHORA; JELLYFISHES; MOON jelly (Cnidaria); COPEPODA; MNEMIOPSIS
- Publication
Aquatic Invasions, 2012, Vol 7, Issue 2, p147
- ISSN
1798-6540
- Publication type
Article
- DOI
10.3391/ai.2012.7.2.001