Microbial community dynamics: a sensitive tool for assessing marine ecosystem health and the response to environmental change

Microbial communities, accounting for up to 90% of the total biomass of the oceans, play a critical role in driving global biogeochemical cycles. Community analysis of microbial biomass reveals extraordinary taxonomic... [ view full abstract ]

Microbial communities, accounting for up to 90% of the total biomass of the oceans, play a critical role in driving global biogeochemical cycles. Community analysis of microbial biomass reveals extraordinary taxonomic diversity with distinct communities in different water masses. Their diversity is reflected by metabolic versatility that allows marine microbes to respond rapidly to changes in their physical and chemical environment, including anthropogenically-driven change. These responses, including shifts in the diversity and structure of microbial communities and their metabolic activity, can be used as a sensitive tool for assessing ecosystem health, anthropogenic impact and responses to climate change. We recently launched a multi-disciplinary project to develop a marine spatial plan (MSP) for Algoa Bay to inform South Africa’s new MSP process. The first objective is to produce a bioregional plan. This requires fundamental knowledge of the extent and distribution of biodiversity, the ecosystem processes that sustain this biodiversity and the anthropogenic factors that impact ecosystem functioning. Algoa Bay is influenced by oceanographic features including warm subtropical waters from the Agulhas Current, upwelling of cool, nutrient-rich bottom waters and significant nutrient-rich freshwater inflow. In a bottom-up approach, we used next generation sequencing analysis to characterise the pelagic and benthic bacterial and phytoplankton communities of the Bay, including the Sundays and Swartkops estuaries. The data provide insight into macro- and mesoscale variability that reflect the complexity of freshwater and marine influences and anthropogenic impact with important implications for the development of a bioregional plan for the Algoa Bay system.