The long-term succession of cladoceran fauna and palaeoclimate forcing: A 14,600-year record from Plešné Lake, the Bohemian Forest

A sediment record of cladoceran remains was analysed in a 543 cm long core from Plešné jezero (Plešné Lake), the Bohemian Forest, Czech Republic. The core covered the time period from the Oldest Dryas to the present. Littoral and benthic Cladocera included 11 species of the family Chydoridae while three species (Bosmina longispina, Daphnia cf. pulicaria and D. cf. longispina) lived in the open water. Remains of Alona quadrangularis and Chydrous sphaericus occurred in the oldest sediment layers from the beginning of the Bølling chronozone. Bosmina longispina and Daphnia cf. pulicaria appeared about 400 years later. Inorganic sediment accumulated at a relatively high rate of ∼ 90 mg cm−2 yr−1 at that time, diluting cladoceran remains and organic matter. Remains of Cladocera accumulated at 0.1 to 0.01 of the Holocene rate, making it difficult to observe effects of climate variation on the species structure of Cladocera in the Late-Glacial. Production of remains increased after warming during the Younger Dryas-Preboreal transition at ∼11.6 kyr BP, and the proportion of littoral species increased. The most important change in cladoceran fauna occurred at ∼10.5 kyr BP and culminated with afforestation of the catchment around 10.3 kyr BP. The domaination of Bosmina longispina lasted for ∼250 years. The afforestation occurred concurrently with a decrease in lake water pH. Bosmina longispina and Daphnia cf. pulicaria disappeared, production of cladoceran remains decreased, but biodiversity increased. Planktonic Cladocera were represented by Daphnia cf. longispina during most of the rest of the Holocene. The production of Cladocera never reached the Preboreal level. Since ∼ 5 cal. kyr BP, the inferred pH continuously decreased. The final decline was likely caused by cooling during the Little Ice Age and by sulphur emissions from ore smelting. The recent acidification of lake water and impoverishment of aquatic fauna was brought about by emissions of sulphur and nitrogen compounds in the 20th century.