Meta-analysis of 139 extant Tara ocean metagenomes to unveil the relationship between taxonomy and functionality in prokaryotes inhabiting aquatic ecosystems

The total microbiome functionality of bacteria was recently predicted to be 35.5 {+/-}0.2 million of KEGG functions. Logically, due to the limitation in space and resource availability of the local community, local functionality will only comprise a small subset of the total functionality but the relationship between taxonomy and functionality is still uncertain. Here, I used a meta-analysis of 139 extant Tara ocean seawater samples from 68 locations across to globe with information on prokaryotic taxonomy on species level from 16S metabarcoding and functionality of prokaryotes on eggNOG gene family level from metagenomes to unveil the relationship between taxonomy and functionality, and to predict the global distribution of functionality. Functional richness showed a statistically significant increase with increasing species richness (P <0.0001, R2 =0.64) and increasing species diversity (P <0.0001, R2 =0.26) while functional diversity was similar across the different waters, ranging from 2.96 to 3.22. Globally, the highest functional richness was found in the Northern Pacific Ocean and in the North Atlantic Ocean, and decreased at extreme latitudes. Taken together, I unveil the relationship between taxonomy and functionality, and predict the global distribution of functional richness in prokaryotes inhabiting aquatic ecosystems, implying more pronounced effects in terrestrial ecosystems due to larger differences in environmental parameters especially for functional diversity.