Distribution of larvae of polychaetes and molluscs in plankton of the Black Sea

Pelagic larvae of polychaete worms and molluscs are always present in plankton inhabiting the Black Sea. Material that underpins this paper are 270 samples of plankton collected during three research cruises to the western Black Sea and two to the central part of the sea in different seasons of 1957. The study evidences that pelagic larvae of polychaete worms and molluscs – Polychaeta, Lamellibranchia, Gastropoda and Amphineura – occur in any part of the sea; however, being neritic forms, they have the abundance and diversity greatest in coastal zone of the sea. Pelagic larvae of the polychaetes and molluscs are found in plankton of the Black Sea year round; the peak of their species diversity and abundance is typically registered in summer months. Lamellibranchia contribute the largest share to the total number of larvae of benthic invertebrates; larvae of polychaetes and molluscs prefer upper seawater layers