Diversity and biogeochemical function of planktonic fungi in the ocean.

Microbial communities play critical biogeochemical roles in the functioning of marine ecosystems. Recent advances in molecular methods and environmental genomics have greatly advanced our understanding of microbial prokaryotes and their diversity and functional ecology in the world's oceans. Large populations of heterotrophic eukaryotes are well documented in the oceans and yet, their diversity and function remain relatively unknown. Particularly, large populations of planktonic fungi have long been known to exist in coastal and oceanic waters but the diversity and ecology of planktonic fungi remain one of the most under-studied microbial topics. Recent studies have revealed novel diversity and interesting ecological functions of planktonic fungi and suggest that they are a potentially important component in marine microbial food web. This chapter will review the diversity and ecology of planktonic fungi in the world's oceans and discuss their significance in ocean carbon and nutrient cycling.