Diversity and co-occurrence networks of picoeukaryotes as a tool for indicating underlying environmental heterogeneity in the Western Pacific Ocean.

Picoeukaryotes are an essential component of microbial communities and play key roles in marine ecosystems. In this study, surface water picoeukaryotes were investigated at 32 stations along a latitudinal cross-section of the Western Pacific (WP) in 2015. Multivariate analyses demonstrated that there were clear spatial patterns in picoeukaryotic community structures which were consistent with the distributions of environmental variables. The spatial patterns of community structures and diversity indices were all significantly correlated with multiple environmental parameters, especially nutrients. Co-occurrence networks linked community variability to environmental heterogeneity. In summary, the construction of picoeukaryotic communities in the WP was significantly affected by numerous environmental variables, and certain variables were revealed as key forcing factors responsible for the main similarities between picoeukaryotic communities. This study details the relationships between the picoeukaryotes and environmental parameters in the WP, and provides insight for application of using picoeukaryotes as indicator in future bioassessment for open waters.