The World’s oceans are fairly well explored. Yet, there are organisms in the marine plankton that are almost completely unknown. Some of the organisms that have escaped the critical eyes of scientists are the unicellular parasites of the ocean’s zooplankton. Fish larvae and microscopic crustaceans named copepods are the most important components of the marine zooplankton, which plays a key role in the marine food web, and these organisms have long been known to host parasites. Nevertheless, very little is known about the importance of parasitism in marine zooplankton, and we don’t even know what kinds of organisms these parasites are. A few recent investigations have demonstrated that up to half of all eggs and newly hatched fish larvae of important fishes as sardine, mackerel, cod and turbot are infected with microscopic, unicellular parasites that may be fatal to their hosts. Also the most numerous animals in the oceans, the copepods, are infected with parasites that are presumably affiliated with very different groups of organisms. The aim of this project is to classify these parasites by analysing their DNA. Such classification is important for future understanding of prevalence and impact of parasitism in the marine zooplankton. Parasitism probably contributes significantly to the natural mortality of fish larvae and copepods and is, thereby, of considerable importance for sizes and conditions of fish stocks. At the moment, we have insufficient basic knowledge on the biology of these parasites and it is, therefore, not currently possible to assess their dynamics and effects.

The field work will take place in the North Atlantic/Mediterranean Sea in September 2006