Osmomixotrophy in Phytoplankton: Analysis of 46 Strains From Marine and Freshwater Habitats Indicates Prevalent Use of Organic Compounds

ABSTRACT

Osmomixotrophic use of dissolved organic compounds may be more widespread than previously recognized, but research seems so far isolated and mostly focusing on single phytoplankton groups or strains. Here we combined data from 24 marine and 22 freshwater strains to analyse their ability to use dissolved organic compounds. The results emphasize that osmomixotrophy is ubiquitous in phytoplankton across functional groups and taxa isolated from various habitats and not strictly dependent on light or nutrient deficiencies. Differences found in phytoplankton originating from different habitats may result from adaptive responses to habitat conditions, but conclusions need to be drawn carefully in line with the limited number of taxa included per habitat and potential niche partitioning. This study underscores the ecological significance of heterogeneous nutritional strategies and the necessity to address existing knowledge gaps to finally draw conclusions about the impact of osmomixotrophy in the context of single ecosystems and on global scales.