Chydorid Ephippia as Indicators of Past Environmental Changes – A New Method

Abstract

I present a new method, ephippium analysis, to investigate past environmental changes which may have affected chydorid Cladocera (Anomopoda, Chydoridae). I studied chydorid ephippia from sediments of two small lakes (Kaksoislammi and Rutikka) in southern Finland. The relative adundance of chydorid ephippia periodically increased during the Holocene. Ephippia were abundant during the late Pleistocene/early Holocene transition, reflecting the severe climate (short open-water season) that existed prior to the onset of rapid postglacial warming. Both lakes experienced an environmental change in the late Holocene. In Kaksoislammi there was a dramatic change in predator–prey relationships following a decline in pH. All chydorids responded with increased gamogenesis. Prehistoric anthropogenic activities caused a rise in the trophic state in Rutikka and probably caused changes in the predator/food web. One chydorid, Alona affinis, reacted first with increased gamogenesis and then almost disappeared. These first results of ephippium analysis indicate that the method has a great potential in detecting periods of environmental change during the Holocene.