Systematics and ecology of the Isefjord marine fauna (Denmark) with a survey of the eelgrass (Zostera) vegetation and its communities

Abstract This paper represents the results of more than 30 years field observations and research work carried out from the Isefjord Laboratory, Vellerup Vig (Zealand, Denmark), which is owned and financed by the author. The Isefjord complex, 36 km long, including the main fjord and the Roskilde Fjord, and covering about 400 km2, is a shallow (7–10 m, max. 30 m) area dominated by substrata of fine sand to mud with a high content of organic matter. As a guidebook for future research the first part gives information about distribution, systematics, ecology, and breeding of the majority of the 477 animal species described. Nearly 400 species are invertebrates and of the chordates 68 species are true fishes. 63% of all animal species have not previously been recorded from the area, 27 species are new to Danish seas, and one (Polychaeta, Capitellidae) is new to science. The hydrography is treated mainly on the basis of literature. The fjord system may be classified as mixohaline: the Isefjord proper is polyhali...