A two-step expansion of the dinocyst $Lingulodinium\ machaerophorum$ in the Caspian Sea: the role of changing environment
Résumé
Dinoflagellate cyst assemblages were analysed in four short sediment cores collected in the south Basin
of the Caspian Sea for assessing environmental changes over the last few millennia. Two of these cores
were dated by radionuclides. The sedimentation rate of one of them was very high, in the order of 20 mm
per year. The interpretation of the four sequences is supported by a collection of 27 lagoonal or marine
surface sediment samples. A sharp increase in the concentration of the dinocyst occurs after 1967,
especially owing to Lingulodinium machaerophorum. Considering nine other cores covering parts or the
whole of Holocene, it became clear that this species started to develop in the Caspian Sea only during the
last three millennia. By analysing instrumental data and collating existing reconstructions of sea level
changes over the last decades, we show that the main forcing for the recent increase of
L. machaerophorum percentages and concentration is global climate change, especially sea surface
temperature increase. Sea level fluctuations likely only have a minor impact. We argue that the recent
increase in L. machaerophorum indicates that the Caspian Sea clearly is in the Anthropocene.
Origine : Publication financée par une institution
