Metagenomic Insights Into Co-Proliferation of Vibrio Spp. and Dinoflagellates Prorocentrum During A Spring Algal Bloom in the Coastal East China Sea Near Xiamen

Abstract

BackgroundCoastal harmful algal blooms (HAB), commonly termed ‘Red tides’, have severe undesirable consequences to the marine ecosystems and local fishery and tourism industries. Increase in nitrogen and/or phosphate loading is often attributed as the major culprits of increasing frequency and intensity of the coastal HAB; however, fundamental understanding is lacking as to the causes and mechanism of bloom formation despite decades of intensive investigation.ResultsIn this study, we interrogated the prokaryotic microbiomes of surface water samples collected at two neighboring segments of East China Sea that contrast greatly in terms of the intensity and frequency of Prorocentrum-dominated HAB. Mantel tests identified significant correlations between the structural and functional composition of the microbiomes and the physicochemical state and the algal biomass density of the surface seawater, implying the possibility that prokaryotic microbiota may play key roles in coastal HAB. A conspicuous feature of the microbiomes at the sites characterized with high trophic state index and eukaryotic algal cell counts was disproportionate proliferation of Vibrio spp., and their complete domination of the functional genes attributable to the dissimilatory nitrate reduction to ammonia (DNRA) pathway significantly enriched at these sites. The genes attributed to phosphorus uptake function were also significantly enriched at these sites, presumably due to the Pi-deficiency induced by algal growth; however, the profiles of the phosphorus mineralization genes lacked consistency, barring any conclusive evidence with regard to contribution of prokaryotic microbiota to phosphorous bioavailability. The results of the co-occurrence network analysis performed with the core prokaryotic microbiome also supported that the observed proliferation of Vibrio and HAB may be causally associated.ConclusionsThe findings of this study suggest a previously unidentified association between Vibrio proliferation and the Prorocentrum-dominated HAB in the subtropical East China Sea, and opens a discussion regarding an unlikely, but still possible, involvement of Vibrio-mediated DNRA in Vibrio-Prorocentrum symbiosis. Further substantiation of this interaction with culture-based experiments may prove crucial for understanding of the dynamics of explosive local algal growth during HAB events endemic to the region.

Comparative metagenomic analysis of microbial community compositions and functions in cage aquaculture and its nearby non-aquaculture environments

“…A study on P. donghaiense found that as P. donghaiense is primarily a photoautotrophic organism with carbon needs mostly fulfilled from uptake of inorganic carbon, the environmental factors regarded to be crucial to its overgrowth during the bloom events are presumably availability of nitrogen and phosphorus, as suggested by previous laboratory observations (Varkitzi et al, 2010;Anderson et al, 2012). Kim et al (2021) found through their study on the co-proliferation of Vibrio spp. and dinoflagellates Prorocentrum during a spring algal bloom in the coastal East China Sea that there is a clear correlation between Vibrio and algal blooms.…”

“…Water eutrophication can easily lead to the occurrence of anaerobic environments, and therefore, the population size of sulfate-reducing bacteria can to some extent indicate the level of water nutrient enrichment. Existing studies have shown that in general, the abundance of sulfate-reducing bacteria is negatively correlated with dissolved oxygen content and positively correlated with water nutrient enrichment (Kim et al, 2021).…”

“…To gain a more comprehensive understanding of the functional profiles of microbial communities in both aquaculture and non-aquaculture environments, our analysis specifically targeted genes encoding key enzymes linked to distinct ecosystem functions. Because less predictable is the influence of microbiota on Eutrophication of water bodies of the marine phosphorus cycle, given the patchy ecophysiological understanding of marine microbial phosphorus metabolism (Kim et al, 2021). We identified genes related to phosphorus (P) metabolism in seawater by reviewing the literature.…”