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Keywords:

  • conductivity;
  • eutrophication;
  • floating-leaved macrophytes;
  • plant macrofossils;
  • submerged macrophytes

Summary

  1. Aquatic macrophytes are commonly used to assess the ecological condition of lakes. Little is known, however, about long-term macrophyte dynamics in shallow lakes. In the absence of historical data, the remains of macrophytes (fruits, seeds and vegetative fragments) found in lake sediments may provide just such information. In order to interpret confidently past change in aquatic plant communities from their sedimentary remains, it is vital to establish the similarity between the contemporary and fossil assemblages.
  2. We investigated the relationship between present lake vegetation and plant macrophyte remains in surface sediments. Thirty-five shallow lakes, spanning around six degrees of latitude and mostly located in the semi-arid Mediterranean climatic zone of Turkey, were sampled for aquatic plants, surface sediment plant remains and a range of other key environmental variables.
  3. Around 50% of the taxa recorded in the modern vegetation were represented in the sediment. Sedimentary macrofossils of some taxa were under- or over-represented relative to their frequency in the modern vegetation, for example Potamogeton spp. and Characeae, respectively. Despite this disparity, there was good agreement between the assemblage composition of the modern and sedimentary samples. Furthermore, conductivity and trophic state (as indicated by total nitrogen, total phosphorus and chlorophyll-a) were the environmental variables most clearly correlated with both the contemporary and macrofossil assemblages in these lakes.
  4. We conclude that aquatic macrophyte macrofossils can be used as reliable indicators of ecological status and to determine qualitative changes in assemblages of aquatic plants consequent to environmental change (e.g. in lake trophic status and/or salinity). This may be especially useful for lakes in arid and semi-arid Mediterranean regions, which are particularly vulnerable to hydrological constraints under climate change.