Mr Matthew Nelson1
1Environment Protection Authority SA, Adelaide, Australia
Spencer Gulf has some of the most extensive Posidonia seagrass meadows in the world, which support vast fisheries, capture carbon, stabilise sediments and assimilate nutrients. However, habitats are sensitive to environmental change, which jeopardises the services they provide. The EPA runs a large broadscale monitoring program, developed to detect potential impact of nutrient enrichment throughout South Australia. The EPA monitored habitat condition in Spencer Gulf across over 100 sites between 2010-2018 and found that throughout the region there has been broadscale habitat decline including sites changing from moderate to dense seagrass habitat to bare sand with the system now considered mesotrophic rather than oligotrophic. Some areas showed clear association to known anthropogenic nutrient sources, but interestingly, further north in the Gulf the association to known sources was not clear-cut.
The multiple uses within Spencer Gulf are well known, but with this comes cumulative impacts from all sources including industry, aquaculture, stormwater, agriculture and wastewater. Interrogation of discharge data suggests that nutrient inputs have remained stable over the last ~20 years, but we are seeing on-going habitat decline. Are the habitats in northern Spencer Gulf at a tipping point and could the rising sea surface temperature and marine heatwaves contribute to stress that could push them over the edge?
Completed undergrad and Honers in Marine Biology at Flinders University. I joined the EPA in 2009 and have been involved implementing and delivery of the Aquatic Ecosystem Condition Reports for the nearshore marine environments for South Australia.