Holocene paleoclimate reconstruction on the eastern Adriatic based on ostracods and stable isotopes from a coastal Lake Velo Blato (Croatia)

Coastal systems, such as those of the Eastern Adriatic Coast, are complex archives where marine and terrestrial influences can hinder paleoclimate reconstruction. Here, we present a new lake sediment record from coastal karst Lake Velo Blato and use stable isotopes and compositional analysis of ostracod assemblages to reconstruct Holocene paleoclimate and paleoenvironmental changes. Ostracod assemblages revealed three ecological groups: brackish (Cyprideis torosa), freshwater (Cypridopsis vidua), and wetland (Limnocythere inopinata, Darwinula stevensoni), indicating that salinity is the main ecological driver, while processes related to lake succession are secondary. Stable isotope composition of calcite suggests the wettest climate conditions between 8100 and 7500 cal yr BP, coinciding with the development of a freshwater lake. Marine influence is evidenced between 7500 and 6300 cal yr BP, marked by a transition from freshwater (Candona neglecta, Cypridopsis vidua, Paralimnocythere psammophila) to brackish (Cyprideis torosa, Candona angulata, Heterocypris salina) ostracod assemblages, which persisted throughout the Middle to Late Holocene. However, shifts in carbon isotopes around 2100 cal yr BP indicate a significant environmental change, coinciding with a transition from a brackish lake to a shallow wetland. Climatically, warm and dry conditions prevailed during the Roman and Medieval Warm Periods, while wetter conditions have dominated since the Little Ice Age. This study provides a high-resolution record of Holocene paleoclimate and paleoenvironmental change, offering a valuable contribution to understanding coastal systems of the Eastern Adriatic region.