Activity, Diversity, and Genetic Makeup of Wild Marine Photosynthetic Eukaryotes

The marine biosphere is responsible for approximately half of global photosynthetic carbon fixation. The organisms that perform the bulk of marine photosynthesis are unicellular and extremely diverse. The unicellular eukaryotic component includes algae that belong to the Viridiplantae as well as members of other eukaryotic supergroups. Genomes have been sequenced from five cultured common marine green algae (Viridiplantae), including the smallest free-living eukaryotes known, as well as from other widespread groups. However, many other marine eukaryotic algae remain uncultured. Targeted genomic and transcriptomic data taken straight from the environment without a culturing step are providing powerful new information on the diversity, biology and ecology of these microbes. Along with genome sequences from cultured taxa, these data also give us insights to algal and land plant evolution. Large scale differences have been observed in gene content and invasive elements. At a finer scale, pathway analysis is providing insights to niche differentiation and organism interactions. The secrets revealed by comparative omic analyses form a baseline against which hypotheses can be developed and tested on the environmental factors that regulate algal growth and contributions to global carbon fixation. Combined with traditional and molecular oceanographic research approaches, new lineages are being identified and the activities of uncultured taxa revealed. Here, we will explore discoveries from oceanographic field work and their integration with new findings from model systems.