The diatom records of two sediment cores taken in the SW part of the Gulf of Gdańsk indicate paleoenvironmental variability in the last three stages of formation of the Baltic Sea: the Mastogloia, the Littorina and the Post-Littorina. Diatom community compositions of the cores show the influence of several factors on past environmental conditions of the study area: (1) regional salinity changes, (2) changes of the Vistula River inflow, and (3) sedimentary processes connected with the Hel Peninsula development.

The aim of this study was to analyze resting spores of Chaetoceros spp. preserved in Middle and Late Holocene sediments of the three parts of the Gulf of Gdańsk, southern Baltic Sea. The material studied consists of ten cores retrieved from Kuźnica Deep (Puck Lagoon), as well as the shallower and deeper parts of the Outer Puck Bay region. Our results indicate that the abundance of Chaetoceros resting spores in diatom taphocoenoses corresponded to regional and local paleoecological changes registered in Mastogloia, Littorina and Post-Littorina sediments, and that they also reflect human impact in the last hundred years.