Genetic diversity of picoeukaryotes in a semienclosed harbour in the subtropical western Pacific Ocean

Abstract

Picoeukaryotes (<2 to 3 μm) are important components of aquatic ecosystems. The genetic diversity and seasonal variability of marine picoeukaryotes were compared between a semienclosed harbour and the adjacent open sea off the subtropical coast in the western Pacific Ocean based on 18S rRNA clone library analysis. Examination of 733 clones revealed 186 different restriction fragment length polymorphism (RFLP) patterns, representing 186 operational taxonomic units (OTUs). At least 19 high-level taxonomic groups of picoeukaryotes were recorded. Alveolates group II, ciliates and stramenopiles comprising 37, 17 and 11 % of the picoeukaryotes, respectively, were the most dominant groups. Phototrophs such as prasinophytes, cryptophytes and haptophytes were retrieved occasionally. Members from the 2 newly defined phyla, picobiliphytes and Telonemia, were also obtained. A differential spatial distribution of OTUs was observed between samples collected from the 2 sampling sites. Seasonal variations in picoeukaryote composition were more pronounced in the open sea libraries than in the semi-enclosed harbour libraries. © Inter-Research 2008.