Gohse-Reimann, Sandra Sabine (2007) Untersuchungen zur Ernährungsökologie benthischer Invertebraten im Makrophytensystem : ein marin-limnischer Ansatz. (PhD/ Doctoral thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 216 pp.

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Abstract

Macrophytes of different aquatic environments house a large variety of invertebrates. Due to a far branched food web these invertebrates form an important link between primary producers and final consumers. However, this food web is influenced by many abiotic and biotic factors. Networking between the macrophytes as well as their associated epiphytes and the invertebrate grazers is both in marine and freshwater systems well described. The interactions between the invertebrates of both systems are examined only scantily. During a two-year monitoring program the community of the macroinvertebrates of a marine (Zostera marina, Baltic Sea) and one freshwater (Potamogeton perfoliatus, Schluensee) macrophyte systems was examined monthly. Clear differences turned out in the seasonal structure of both habitats. While the marine eelgrass community is characterized by the sessile mussel Mytilus edulis, the mobile snails Radix ovata and Potamopyrgus antipodarum dominate in the freshwater environment. The omnivorous invertebrates (without decapods) are predominating in the shoot area in both systems. These data from the field investigations formed the basis for extensive laboratory examinations. In marine and freshwater mesocosm experiments intra- and interspecific interactions of amphipods, isopods and gastropods were examined. It turned out that strong effects occur in the marine environment while there weren't any effects in the freshwater approaches. As the biomasses of isopods in the marine mesocosms decreased in the presence of the amphipods while no effect was observed in the freshwater. Feeding preference tests with three crustacean species each from the two examined habitats showed seasonal differences among the decapods and amphipods of both systems. While the marine amphipods and isopods preferred predominately the vegetable food source, the freshwater representatives gave an average preference to animal food sources. The quality of the food source had strong effects on the biomass growth and the survival rates of the animals in marine and freshwater amphipods and isopods. The presence or the density combination of the two crustacean groups also affected the two factors mentioned before. It became evident that more isopods survived on animal food in the two environments if the gammarid crustaceans were excluded. The biocoenosis in marine and freshwater macrophyte systems are subject to strong seasonal changes. In both systems macrophytes were quite different in their seasonal availability as habitats for invertebrates. Factors like the food quality, density composition and availability of the food can perform a strong influence on the macroinvertebrate fauna. Both examined environments were different in there structure and the distribution of the food related ecological groups.

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