Use of organic compounds by phytoplankton - a synthesis across strains from different habitats and functional groups

Abstract

Mixotrophy is emerging as a default nutritional strategy in phytoplankton, but research seems so far isolated and mostly focusing on single phytoplankton groups or strains. Here we combined data from 24 oceanic and 22 freshwater strains to analyze phytoplanktons ability to use dissolved organic compounds. The results emphasize that mixotrophy is ubiquitous in phytoplankton across functional groups and taxa isolated from various habitats and not strictly dependent on light or nutrient deficiencies. We propose that the prevalence of mixotrophy stems from phytoplanktons heterotrophic ancestry, while the divergence into different lineages partly explains variation in mixotrophic behavior. 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 mixotrophy in the context of single ecosystems and on global scales. Graphical abstract textAnalyzing thousands of data points across 46 marine and freshwater strains, this study establishes mixotrophy as a ubiquitous metabolic strategy in phytoplankton. These findings challenge the autotrophic paradigm, demonstrating that organic matter acquisition is a default state with significant implications for our understanding of global carbon cycles. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=93 SRC="FIGDIR/small/703725v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@cd9939org.highwire.dtl.DTLVardef@6a4fdorg.highwire.dtl.DTLVardef@39f5a6org.highwire.dtl.DTLVardef@12e811a_HPS_FORMAT_FIGEXP M_FIG C_FIG