Differential responses of macro- and meiofaunal communities to environmental factors and pollutants along coastal gradients around south-eastern Australia.
Supervisors: Graham Edgar, Scott Ling( University of Tasmania).
Although possessing great importance in terms of production and biodiversity, a largely unknown component of shallow rocky reef environments of southern Australia are macro- and meiofauna – animals ranging from 16 mm to 0.125 mm. These animals occur particularly abundantly on macroalgae and in sediment. Although their size prevents them from being as visible as other emblematic marine animals, they are of critical importance to the coastal ecosystems they inhabit, notably in marine food webs and nutrient cycling. Like other invertebrates associated with shallow rocky reefs, they are exposed to a wide variety of pollution and environmental forcing. In the present study, the distribution of infauna and epifauna is quantified across 43 sites around south-eastern Australia. The variability in structure and richness of these communities is analysed against seventeen environmental and pollutant factors measured across the sites, grouped into five categories: environmental, catchment effects, heavy metals, hydrocarbons and nutrients. Likely environmental and anthropogenic drivers associated with pollution gradients in sites adjacent to state capital cities (Sydney, Adelaide, Melbourne and Hobart) with a legacy of heavy metal pollution and other pollutants and in more pristine sites (eastern Tasmania) are identified using DISTLM (Distance based Linear Models). An effort was made to disentangle environmental variability from habitat effects and also pollutants’ impact on the coastal communities on a large bio-geographical scale. Environmental factors were found to drive more variability in communities than the fourteen pollutants, of which only lead and total organic carbon affect all three communities in terms of structure. Each community had differing sensitivities, infauna was strongly associated with catchment effects, heavy metals and nutrients, reef macrofauna was strongly associated with hydrocarbons and nutrients and reef meiofauna varied with heavy metals, hydrocarbons and nutrients. Responses to the factors in terms of richness and mean body size also differed between the communities. The sensitivity of the analysis at different taxonomic ranks showed that sensitivity declined after the species rank for structure and order and class rank for richness for the infaunal and macrofaunal (larger than 1 mm) communities, respectively. Insights gained during the study on how small marine life respond to environmental and pollution covariates fills a vital knowledge gap for improved management of food webs and ecosystem function in polluted estuaries.