Elucidating the effects of physicochemical variables on the structure, composition and functionality of microbiomes in the Prince Edward Islands

Abstract

Recent studies have shown that a range of biological and oceanographic features shape the composition, structure and function of Southern Ocean (SO) microbiomes. Within the vicinity of islands, the interactions between landmasses, the surrounding waters and biology result in complex tropic interactions. These interactions are expected to affect nutrient cycling and ecosystem services the bulk of which is driven by microorganisms. However, little is known regarding the microbial dynamics of near- shore regions of SO islands such as the Prince Edward Islands (PEIs). This knowledge deficit is particularly true for particle attached (PA) and free living (FL) bacterioplankton and fungal microbiota. Here, we provide insights regarding microbial community structure and composition of PEI microbiomes. We assess the effects of physicochemical factors on PEI microbial communities. Samples were collected from three depths, namely, the Fluorescence maximum (Fmax), the oxygen minimum zone (OMZ) and the bathypelagic zone (Deep) at 10 sites within the vicinity of the PEIs. Phylogenetic analysis of 16S and ITS rRNA gene regions and statistical analysis revealed a shift in bacterioplankton and fungal community structure and composition, respectively. This shift coincided with differences in depth and water mass specificity. The results also show that PA and FL PEI microbial communities were strongly influenced by oceanographic features and physicochemical variables. Extracellular enzymatic activities specific for carbon, nitrogen and phosphorus acquisition did not reveal any specific trends between community composition and potential functionality but exhibited a close linkage with substrate availability and depth. These resultssuggest that potential extracellular enzymatic functionality of the microbiome is driven by nutrient dynamics in this environment. This study provides valuable insights regarding the influence of biotic and abiotic drivers in the dynamics of near-shore microbial communities in the SO.