Selective grazing by adults and larvae of the zebra mussel (Dreissena polymorpha): application of flow cytometry to natural seston

1. Selective grazing of adults and larvae of the zebra mussel (Dreissena polymorpha) on phytoplankton and detritus from both laboratory cultures and natural seston was quantified using flow cytometry. 2. Mean clearance rate of adult zebra mussels was higher on a mixture of the green alga Scenedesmus and the cyanobacterium Microcystis than when Scenedesmus was offered as single food, suggesting selective feeding by the mussels. 3. Feeding on lake seston both adults and larvae showed a higher clearance rate on phytoplankton than on detritus particles, suggesting that zebra mussels select for phytoplankton. Furthermore, it was noted that adults preferred seston particles in the 0-1 and 30-100 m size ranges. 4. In our study, zebra mussels did not discriminate against cyanobacteria, and our results indicate that they may even ingest them preferentially

The impact of climate change on lakes in the Netherlands: a review

Climate change will alter freshwater ecosystems but specific effects will vary among regions and the type of water body. Here, we give an integrative review of the observed and predicted impacts of climate change on shallow lakes in the Netherlands and put these impacts in an international perspective. Most of these lakes are man-made and have preset water levels and poorly developed littoral zones. Relevant climatic factors for these ecosystems are temperature, ice-cover and wind. Secondary factors affected by climate include nutrient loading, residence time and water levels. We reviewed the relevant literature in order to assess the impact of climate change on these lakes. We focussed on six management objectives as bioindicators for the functioning of these ecosystems: target species, nuisance species, invading species, transparency, carrying capacity and biodiversity. We conclude that climate change will likely (i) reduce the numbers of several target species of birds; (ii) favour and stabilize cyanobacterial dominance in phytoplankton communities; (iii) cause more serious incidents of botulism among waterfowl and enhance the spreading of mosquito borne diseases; (iv) benefit invaders originating from the Ponto-Caspian region; (v) stabilize turbid, phytoplankton-dominated systems, thus counteracting restoration measures; (vi) destabilize macrophyte-dominated clear-water lakes; (vii) increase the carrying capacity of primary producers, especially phytoplankton, thus mimicking eutrophication; (viii) affect higher trophic levels as a result of enhanced primary production; (ix) have a negative impact on biodiversity which is linked to the clear water state; (x) affect biodiversity by changing the disturbance regime. Water managers can counteract these developments by reduction of nutrient loading, development of the littoral zone, compartmentalization of lakes and fisheries management