CS39A Zooplankton - Feeding, Reproduction, Growth and Molecular Diversity
Date: Tuesday, June 11, 2002
Time: 5:00:00 PM
Location: View Royal
 
HansenBW, Roskilde University, Roskilde, Denmark, bhansen@ruc.dk
Stenalt, E, , Roskilde University, Roskilde, Denmark, stenalt@ruc.dk
Petersen, J, K, National Environmental Research Institute, Roskilde, Denmark, jkp@dmu.dk
Bisgaard, H, C, Roskilde University, Roskilde, Denmark, hcb@ruc.dk
 
GROWTH AND MORTALITY OF BIVALVE LARVAE AND SETTLERS IN DANISH ESTUARIES.
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In Danish estuaries, characterized by shallow water and high nutrients levels, a tight pelagic-benthic coupling prevails. Filtrating bivalves are pivotal benthic componants, since they to a various extend are controlling the phytoplankton. In a series of projects within SUSTAINEX we aim at developing a model for Sustainable Exploitation of Blue Mussels in Denmark Understanding recruitment of bivalves, larval output, abundance, mortality, and settling are crucial parameters for that model. However, relatively few reports exists on these topics. The next step in recruitment, settlement and survival through the first winter, is also scarcely reported in the literature. In the present we report in situ larval abundance, growth, mortality, and settlement for some Danish estuaries. The presentation will focus on examples from SUSTAINEX. After a total anoxia in a particular estuary, bivalve larvae were carried by water intrusions from open water and were re-colonizing. Despite a high larval mortality, 60-90%, they were established as settlers by a rate of up to 12.000 ind/d. The benthic population was restored within approximately 2 years. Substrate preference was tested in situ as well as under controlled conditions, where the larvae was exposed for 3 choices: unconditioned, biofilm and filamentous algal substrates. A in situ predation study was performed with newly settled individuals suggesting a significant loss due to sea urchins and various crustaceans. The speciation problem among juvenile bivalves is serious. The literature either base the speciation of larvae and newly settlers upon 1) morphology, which is quite difficult and somewhat subjective, 2) or accept results on a taxonomic level by the Class. In the present projects we aim at to be able to speciate by using DNA techniques (RFLP). At present we can speciate the 7 most common species based on individual larvae. Our contribution will report on our problems and successes within DNA speciation.