The food-web of the Cladophora-belt fauna

Abstract

1. The species composition of the fauna in the Cladophora glomerata belts of the Baltic sea has been studied quantitatively. 2. Examples are presented to illustrate composition and density of the epiphytic diatom flora. 3. The dry weight of Cladophora glomerata was determined with the aid of length measurements under a microscope. It amounts to 0.25 mg per 1000 mm length of alga filaments, and to 15.9 mg for a tuft with a total surface area of 1 dm2. 4. The productivity of Cladophora glomerata was calculated. It amounts to 3105 m alga filaments per dm2 per month. 5. The following biomasses per dm2 rock surface have been estimated:Cladophora (dry weight): 0.78 g, diatoms (dry weight): 1.15 g, animals (number of individuals): 12 544. 6. The fauna of the Cladophora-belt has been subdivided according to feeding types. 7. Some herbivores have been studied in laboratory experiments. The epiphytic diatoms are important for survival of the first postmarsupial stages of the isopod Idotea baltica as well as for maximum growth rates of the gastropod Hydrobia ulvae and chironomid larvae. 8. The daily consumption of Cladophora-filaments has been determined for juveniles of the isopod Idotea baltica and the amphipod Gammarus oceanicus by microscope examinations of faecal pellets. 9. The diatom diet of the rotifer Proales reinhardti has been listed according to genera or species. Among the animals living in the Cladophora-belt, P. reinhardti attains the highest numbers of individuals. 10. Examples of food-chains within the Cladophora community are presented. © 1967 Biologischen Anstalt Helgoland.