title: Bacterioplankton Dynamics within a Large Anthropogenically Impacted Urban Estuary.
abstract: The abundant and diverse microorganisms that inhabit aquatic systems are both determinants and indicators of aquatic health, providing essential ecosystem services such as nutrient cycling but also causing harmful blooms and disease in impacted habitats. Estuaries are among the most urbanized coastal ecosystems and as a consequence experience substantial environmental pressures, providing ideal systems to study the influence of anthropogenic inputs on microbial ecology. Here we use the highly urbanized Sydney Harbor, Australia, as a model system to investigate shifts in microbial community composition and function along natural and anthopogenic physicochemical gradients, driven by stormwater inflows, tidal flushing and the input of contaminants and both naturally and anthropogenically derived nutrients. Using a combination of amplicon sequencing of the 16S rRNA gene and shotgun metagenomics, we observed strong patterns in microbial biogeography across the estuary during two periods: one of high and another of low rainfall. These patterns were driven by shifts in nutrient concentration and dissolved oxygen leading to a partitioning of microbial community composition in different areas of the harbor with different nutrient regimes. Patterns in bacterial composition were related to shifts in the abundance of Rhodobacteraceae, Flavobacteriaceae, Microbacteriaceae, Halomonadaceae, Acidomicrobiales, and Synechococcus, coupled to an enrichment of total microbial metabolic pathways including phosphorus and nitrogen metabolism, sulfate reduction, virulence, and the degradation of hydrocarbons. Additionally, community beta-diversity was partitioned between the two sampling periods. This potentially reflected the influence of shifting allochtonous nutrient inputs on microbial communities and highlighted the temporally dynamic nature of the system. Combined, our results provide insights into the simultaneous influence of natural and anthropogenic drivers on the structure and function of microbial communities within a highly urbanized aquatic ecosystem.
authors: Plant Functional Biology and Climate Change Cluster, University of Technology SydneySydney, NSW, Australia; Hawkesbury Institute for the Environment, Western Sydney UniversityPenrith, NSW, Australia.
authors: Thomas C
authors: TC
authors: Jeffries
authors: Plant Functional Biology and Climate Change Cluster, University of Technology Sydney Sydney, NSW, Australia.
authors: Maria L
authors: ML
authors: Schmitz Fontes
authors: School of Geosciences, University of Sydney Institute of Marine Science, The University of SydneySydney, NSW, Australia; Sydney Institute of Marine ScienceMosman, NSW, Australia.
authors: Daniel P
authors: DP
authors: Harrison
authors: Plant Functional Biology and Climate Change Cluster, University of Technology Sydney Sydney, NSW, Australia.
authors: Virginie
authors: V
authors: Van-Dongen-Vogels
authors: Centre for Coastal Management, Southern Cross University Lismore, NSW, Australia.
authors: Bradley D
authors: BD
authors: Eyre
authors: Plant Functional Biology and Climate Change Cluster, University of Technology Sydney Sydney, NSW, Australia.
authors: Peter J
authors: PJ
authors: Ralph
authors: Plant Functional Biology and Climate Change Cluster, University of Technology Sydney Sydney, NSW, Australia.
authors: Justin R
authors: JR
authors: Seymour
keywords: anthropogenic impacts; environmental microbiology; environmental pollutants; estuarine ecology; eutrophication; metagenomics; microbial ecology; microbiome