Deciphering microeukaryotic-bacterial co-occurrence networks in coastal aquaculture ponds

Microeukaryotes and bacteria are key drivers of primary productivity and nutrient cycling in aquaculture ecosystems. Although their diversity and composition have been widely investigated in aquaculture systems, the co-occurrence bipartite network between microeukaryotes and bacteria remains poorly understood. This study used the bipartite network analysis of high-throughput sequencing datasets to detect the co-occurrence relationships between microeukaryotes and bacteria in water and sediment from coastal aquaculture ponds. Chlorophyta and fungi were dominant phyla in the microeukaryotic-bacterial bipartite networks in water and sediment, respectively. Chlorophyta also had overrepresented links with bacteria in water. Most microeukaryotes and bacteria were classified as generalists, and tended to have symmetric positive and negative links with bacteria in both water and sediment. However, some microeukaryotes with high density of links showed asymmetric links with bacteria in water. Modularity detection in the bipartite network indicated that four microeukaryotes and twelve uncultured bacteria might be potential keystone taxa among the module connections. Moreover, the microeukaryotic-bacterial bipartite network in sediment harbored significantly more nestedness than that in water. The loss of microeukaryotes and generalists will more likely lead to the collapse of positive co-occurrence relationships between microeukaryotes and bacteria in both water and sediment. This study unveils the topology, dominant taxa, keystone species, and robustness in the microeukaryotic-bacterial bipartite networks in coastal aquaculture ecosystems. These species herein can be applied for further management of ecological services, and such knowledge may also be very useful for the regulation of other eutrophic ecosystems.