Sediment resuspension, salinity and temperature affect the plankton community of a shallow coastal lake

Climate change is predicted to cause an increasing frequency of storm tides, rising sea levels and water temperatures, and altered precipitation and run-off. Such changes are likely to influence turbidity, salinity and temperature regimes of coastal aquatic ecosystems. To determine possible effects on plankton communities of these ecosystems, we combined feeding experiments with a monitoring study of tidally influenced, polymictic Lake Waihola (New Zealand). The feeding experiments were carried out using dominant Daphnia carinata, and important taxa of heterotrophic nanoflagellates (HNF) and ciliates. The field study encompassed the entire planktonic food web. Moderate levels of turbidity and salinity affected clearance and ingestion rates of D. carinata, HNF and oligotrich ciliates in our feeding experiments. Redundancy analysis identified sediment resuspension, salinity and temperature as important factors affecting the plankton communities in Lake Waihola. A wide variety of biota was affected by sediment resuspension and temperature. Fewer species responded to salinity, most likely due to unusually low salinities throughout the monitoring period. If global warming results in altered turbidity, salinity or temperature regimes in coastal aquatic ecosystems changes might be expected in the structure of their plankton communities, with potential consequences throughout the food web.