First foraminiferal record and multi-proxy reconstruction of paleoenvironmental changes in the Gulf of Gdańsk (SE Baltic Sea) over the last 5000 years

We present new multi-proxy data investigating major environmental transitions over the last 5 kyr BP, based on a sediment core retrieved from the Gulf of Gdańsk (SE Baltic Sea). Between 5 and 1.5 kyr BP, the bay experienced low-energy depositional conditions, which were disrupted around 4 kyr BP, likely due to intensified storm activity and reduced river discharge, potentially linked to the formation of a coastal spit that altered sediment transport patterns. The benthic foraminiferal assemblage during this interval was monospecific, dominated by Cribroelphidium clavatum , a euryhaline species well adapted to brackish conditions. Low benthic δ 18 O values indicated a notable freshening of the Gulf of Gdańsk between 3 and 1.7 kyr BP. A more pronounced shift in the depositional environment occurred around 1.4 kyr BP, when salinity drops and possible hypoxia disrupted benthic habitats. These changes led to the local disappearance of benthic foraminifera assemblages, previously dominated by Cribroelphidium clavatum . Although environmental conditions improved around 0.9 kyr BP, benthic foraminiferal communities did not re-establish, likely due to persistent low salinity and bottom hypoxia conditions.