AME - Vol. 74 No. 4 - Feature article

Inverse estuaries, such as Spencer Gulf (South Australia), are dynamic environments. Hypersalinity and heterogeneity in nutrient concentrations drive shifts in bacterioplankton populations, including between ecotypes of the nitrogen fixing ‚Candidatus Atelocyanobacterium thalassa’ (UCYN-A). Image: Greg Love

Messer LF, Doubell M, Jeffries TC, Brown MV, Seymour JR

 

Prokaryotic and diazotrophic population dynamics within a large oligotrophic inverse estuary

 

Inverse estuaries represent a unique marine environment which unlike classical estuaries, receive very little freshwater inputs and can exhibit steep horizontal salinity gradients from marine to hypersaline waters. Messer and colleagues provide the first description of bacterioplankton and nitrogen fixing (diazotrophic) communities within a temperate inverse estuary in southern Australia, an environment with distinct heterogeneity in biotic and abiotic resources. Biogeographic patterns in the relative abundance of significant cyanobacterial taxa, such as Synechococcus and the diazotrophic ‘Candidatus Atelocyanobacterium thalassa’, demonstrates the complex microbial community dynamics and niche differentiation within the estuary and suggests that pelagic nitrogen fixation could be an important, previously overlooked, process in this temperate system.

 

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