Open AccessSubfossil littoral Cladocera as indicators of brackish‐water Littorina transgression of the Baltic Basin in a small lake in Finland
Author(s) -
SARMAJAKORJONEN KAARINA,
HYVÄRINEN HANNU
Publication year - 2002
Publication title -
boreas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 74
eISSN - 1502-3885
pISSN - 0300-9483
DOI - 10.1111/j.1502-3885.2002.tb01079.x
Subject(s) - marine transgression , littoral zone , littorina , brackish water , fauna , cladocera , siltation , acartia , geology , oceanography , ecology , gastropoda , structural basin , zooplankton , sediment , biology , paleontology , salinity , crustacean , copepod
The study aimed to investigat e the value of freshwater littoral Cladocera (chydorids, Ophryoxu s gracili s and Sida crystallina ) in stratigraphical studies of shore displacement of the Baltic Sea. Diatoms and Cladocera were analysed from a sediment core from Lake Ruokolampi (S Finland, 60°34'N, 27°26'E), where a brackish‐water Baltic transgression (Littorina Sea) is clearly expressed by changes in lithology. The diatom flora indicates a development of the waterbody from an Ancylus Lake bay to a small lake that was subject to a brackish Littorina transgressio n followed by another small‐lake stage. There was a rich chydorid fauna in the Ancylus Lake bay and the following small lake. Littoral Cladoceran diversity fell sharply at the onset of the brackish transgression; however, three species ( Alona rectangula, Alona affinis and Chydorus sphaericus s.l. ) appear to have been tolerant of the saline conditions. Concentrations of all species rose rapidly after the transgression. Littoral Cladocera appear to react to the inflow of brackish water as sensitively as the diatoms and may provide a valuable additional method for pinpointing Baltic Sea transgression and isolation events, especially in cases where the diatom and biostratigraphical evidence is not as clear as in the Ruokolampi sequence.