Analysis of the seasonal impact of three marine bivalves on seston particles in water column

Suspension-feeding bivalves are the keystone species that affect the abundance and composition of phytoplankton communities. This study compares the food selectivity of oysters Crassostrea gigas (Thunberg, 1973), mussels Mytilus galloprovincialis (Lamarck, 1819), and cockles Katelysia rhytiphora (Lamy, 197) on natural particle assemblages in the laboratory using water collected from Coffin Bay, South Australia, in spring, summer, autumn and winter. The phytoplankton community was dominated by Bacillariophyceae (diatoms), Dinophyceae (dinoflagellates), Synechococcus (cyanobacteria), and picophytoplankton (2–5 μm) from September 2016 to August 2017. Diatoms and picoplankton, including cyanobacteria, were dominant in spring and summer, while dinoflagellates were dominant in autumn and winter. Oysters and mussels selectively fed on large food particles (e.g., diatom, dinoflagellate and large picoplankton > 2 μm) regardless of season, but mussels could access a wider size spectrum of food particles compared to oysters. In contrast, cockles selected for both large and small food particles (e.g., Synechococcus and small picoeukaryotes