The Oder Estuary - IOW

Schernewski, G. & T. Dolch (eds.): The Oder Estuary – against the background of the European Water Framework
Directive. Marine Science Reports 57 (2004). ISSN: 0939-396X.
Die Makrofauna des Oderhaffs - Vorschläge für ein Monitoring
nach EU-WRRL
The macroinvertebrate community of the Oder Lagoon - Proposals
for a monitoring after EU-WFD
Silke Rödiger
Universität Duisburg-Essen, FB 9 Institut für Ökologie, Abteilung Hydrobiologie, Germany
Email: silke.roediger@uni-essen.de
Summary
This article reports on a series of studies about the macroinvertebrate community of the Oder
(Szczecin) Lagoon, a coastal basin in the southern Baltic, carried out in 2001 and 2002. The main
goals were to investigate the diatribution of species in the lagoon, to discover changes in the
macroinvertebrate composition and abundance during the 20th century and to make proposals for a
montiroing strategy on benthic invertebrates after the EU Water Framework Directive.
For that purpose samples were taken along the shore (sediment core sampler, hand net) and from
the deeper parts of the lagoon (grab sampler). Additionally selected parameters of the
physicochemical Monitoring in the Sczcecin Lagoon were evaluated for the research period.
The Oder Lagoon has to be classified as eutroph; local oxygen deficits near the ground with a
minimum oxygen saturation of 20 % were observed. The lagoon is an oligohalinic waterbody
showing a salinity range from 0,1 till 4,2 ‰.
Due to the low salinity the macroinvertebrate community in the lagoon mainly consists of limnetic
organisms. In Total 63 taxa were found, with Mollusca (20 taxa) and Diptera (10 taxa) showing the
largest numbers of species. The shore of the lagoon is mainly inhabited by Diptera (Chironomidae)
and Oligochaeta, but the most diverse group are the Mollusca. The species composition at the
beaches and smaller bathing areas differs significantly from the more natural sampling sites which
are covered with dense reeds. Particularly the typical lagoon species which prefer calm waters, only
occured in protected shore areas. The species composition along the transect changed in
dependency on depth and shore distance; additionally it is influenced by the mud content in the
sediment. On the whole, the macroinvertebrate community of the Oder Lagoon is limited to species
with a high tolerance against fluctuations in their abiotic environment.
The comparison between the present biocenosis and historical investigations of the lagoon showed
clear changes in species composition. The Mollusca decreased during the last 100 years. Some
species which, in historical studies, were reported as common or frequent couldn’t be found any
longer, some are collected only once or twice. These species are often described as inhabitants of
reeds or submerse plants. It may be the decrease of macrophyte populations based on
eutrophication that is responsible for this diappearance of special Mollusca. In addition to these
changes, an increasing immigration of new species occured in the lagoon. Particularly in the 1980’s
and 1990’s some Crustacea (Gammarus tigrinus, Pontogammarus robustoides) took advantage by
their tolerance against salinity fluctuations and became established in the Oder Lagoon.