Abstract
Rapid urban expansion and increased human activities have led to the progressive deterioration of many marine ecosystems. The diverse microbial communities that inhabit these ecosystems are believed to influence large-scale geochemical processes and, as such, analyzing their composition and functional metabolism can be a means to assessing an ecosystem’s resilience to physical and chemical perturbations, or at the very least provide baseline information and insight into future research needs. Here we show the utilization of organic and inorganic contaminant screening coupled with metabolomics and bacterial 16S rRNA gene sequencing to assess the microbial community structure of marine sediments and their functional metabolic output. The sediments collected from Moreton Bay (Queensland, Australia) contained low levels of organic and inorganic contaminants, typically below guideline levels. The sequencing dataset suggest that sulfur and nitrite reduction, dehalogenation, ammonia oxidation, and xylan degradation were the major metabolic functions. The community metabolites suggest a level of functional homogeneity down the 40-cm core depth sampled, with sediment habitat identified as a significant driver for metabolic differences. The communities present in river and sandy channel samples were found to be the most active, with the river habitats likely to be dominated by photoheterotrophs that utilized carbohydrates, fatty acids and alcohols as well as reduce nitrates to release atmospheric nitrogen and oxidize sulfur. Bioturbated mud habitats showed overlapping faunal activity between riverine and sandy ecosystems. Nitrogen-fixing bacteria and lignin-degrading bacteria were most abundant in the sandy channel and bioturbated mud, respectively. The use of omics-based approaches provide greater insight into the functional metabolism of these impacted habitats, extending beyond discrete monitoring to encompassing whole community profiling that represents true phenotypical outputs. Ongoing omics-based monitoring that focuses on more targeted pathway analyses is recommended in order to quantify the flux changes within these systems and establish variations from these baseline measurements.
Highlights
Despite Australia’s vast landmass, an estimated 85% of the total population live within the coastal zone [1]
We extend the application of bacterial 16S rRNA gene sequencing and metabolomics to assess the pressures of urban expansion, industrialization, and other factors associated with increased human activities on the Moreton Bay ecosystem
Habitat type was the major control on bacterial community composition when Moreton Bay was considered as a large estuary with diverse habitats and moderate human activity
Summary
Despite Australia’s vast landmass, an estimated 85% of the total population live within the coastal zone [1]. Increased human activities have significantly changed the nutrient flux into these aquatic ecosystems [5]. Eutrophication is one of the biggest threats to coasts and estuaries globally [5], causing severe degradation of water quality, loss of biodiversity and richness, ecological shifts, and ecosystem malfunction [7]. Such changes are likely to adversely affect coastal communities in terms of employment and tourism opportunities and recreational activities. A substantial number of other pollutants such as trace metals, pesticides, and hydrocarbons have been introduced into coastal waters as a result of human activities, increased urbanization, and as a consequence of greater impervious surfaces constructed within catchments [9]
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