Gelatinous zooplankton in the Belgian part of the North Sea and the adjacent Schelde estuary: Spatio-temporal distribution patterns and population dynamics | Marine@Ugent

Gelatinous zooplankton in the Belgian part of the North Sea and the adjacent Schelde estuary: Spatio-temporal distribution patterns and population dynamics

Published paper: Gelatinous zooplankton in the Belgian part of the North Sea and the adjacent Schelde estuary: Spatio-temporal distribution patterns and population dynamics

 

Many ocean ecosystems are thought to be heading towards a dominance of gelatinous organisms. However, gelatinous zooplankton has been largely understudied and the absence of quantitative long-term data for the
studied area impedes drawing conclusions on potential increasing densities. This study gives a comprehensive overviewof the spatio-temporal distribution patterns of gelatinous zooplankton in terms of diversity and density
in the Belgian part of the North Sea and the adjacent Schelde estuary, based on monthly and seasonal samples between March 2011 and February 2012. Three Scyphozoa, three Ctenophora and 27 Hydrozoa taxa were iden-
tified, including three non-indigenous species: Mnemiopsis leidyi, Nemopsis bachei and Lovenella assimilis.In general, one gelatinous zooplankton assemblage was found across locations and seasons. Average gelatinous
zooplankton densities reached up to 18 ind·m−3 near the coast, gradually declining towards the open sea. In the brackish Schelde estuary, average densities remained below 3 ind·m−3
. Highest gelatinous zooplankton densities were recorded in summer and autumn. Overall, hydromedusae were the most important group both in terms of diversity and density. The ctenophore Pleurobrachia pileus and the hydromedusa Clytia sp. were present in every season and at every location. Gelatinous zooplankton densities never outnumbered the non-gelatinous zooplankton densities recorded fromtheWP3 samples. The spatial and temporal distribution patterns seemed to be mainly driven by temperature (season) and salinity (location). Other environmental parameters including (larger) non-gelatinous zooplankton densities (as an important food source) were not retained in the most parsimonious DistLM model.In terms of population dynamics, Beroe sp. seemed to follow the three reproductive cycles of its prey P. pileus and the presence of M. leidyi, which were abundant in a broad size spectrum in summer and autumn. In general, gelatinous zooplankton diversity was higher, but densities were in the same order of magnitude compared to adjacent areas in the North Sea. This study provides a baseline
against which a potential increase in gelatinous zooplankton in the Belgian part of the North Sea and the Schelde estuary can be measured.

 

Authors: Lies Vansteenbrugge, Tina Van Regenmortel , Marleen De Troch , Magda Vincx ,Kris Hostens

 

Read the article here: http://www.sciencedirect.com/science/article/pii/S1385110114002317