Human Impacts on Marine Ecosystems – Conservation Café with Prof Emma Johnston (by Arun Dayanandan)

August 3, 2015 at 12:41 am

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(Arun Dayanandan, August 2015)

On August 1, 2015, the Sydney chapter of the Society for Conservation Biology welcomed Prof Emma Johnston as guest speaker at their monthly Conservation Café series. As Director of the Sydney Harbour Research Program at the Sydney Institute of Marine Science and as an Australian Research Fellow at the University of New South Wales, Prof Johnston has been involved in a multitude of key aspects in marine conservation and research in both academia and the broader community.

At the Saturday talk, Prof Johnston began with an emphasis on the current state of the marine environment in the South-Pacific. As the global climate shifts, the East Australian Ocean Current has begun to move faster, resulting in an increased input of warmer water in previously colder regions. As the water current is a method of providing food and transport for a large number of species, this has led to an increased number of non-native herbivorous and associated predatory species, such as Coral Trout, entering the waterways around Australia. Scientists are finding that these once-temporary visitors are now able to overwinter, and so fewer habitats are left for native species. The impact of warmer waters also acts synergistically with the arrival of new species. As the water warms, toxicity of heavy metals increases along with an increase in the metabolic activity of fish resulting in increased stress levels amongst native species. Furthermore, this increases the resilience of non-native species making them better able to compete for the same resources as the local marine flora and fauna.

Prof Johnston stressed that conservation efforts are already underway to save the habitat of these at-risk species, but that current methods are focused on areas that are already protected, such as national parks. While this is certainly a positive initiative, it is difficult to have equal representation of diverse ecosystems and thus limits the number of species niches protected.

Shifting gears, the talk moved to the issue of microplastics in our oceans. While there exists many concerns in regards to the global marine environment, no issue dominates the minds of the general public as does that of global plastic pollution. In Prof Johnston’s words, “people want clean water to drink, clean water to view, and clean water to fish in.” With an obvious cause and an equally disturbing effect, it is easy to see why the media portray regions such as the Great Pacific Garbage Patch with such vigour.

Unfortunately, the vast majority of microplastics are found throughout the ocean sediment in concentrations 10 times higher than those found in the Pacific gyre. Furthermore, up to 40% of all fish in the ocean have microplastics in their stomachs, either through direct ingestion or by preying upon other species, which have ingested these contaminants. For example, dioxin contamination on the west side of the Sydney Harbour Bridge causes fish in that area to be inedible as, once inside the human body, microplastics cause a disease known as fibrosis.

Despite the pressing issue, the Australian federal government does not maintain an institutionalized system of monitoring the state of these particles. Often times, legislation change comes too little too late, as in the case of the gun buyback program set in motion in the wake of the Port Arthur shootings. During heavy rains and immediate spills, these plastics, along with a host of other contaminants stored in the sediment, are resuspended in the water column. Possible solutions include re-adding sediments from the coast back to the sea floor and adding barriers, such as breakwalls and sandbags, to counter the movement of these plastics. Their drawback lies in the fact that artificial barriers change the dynamics of the waterways, leading to decreased intertidal zones and a change in species diversity. Furthermore, while these barriers may work along the coast, it does not prevent microplastics from entering city water facilities and, ultimately, in our drinking water.

As Prof Johnston closed: despite the effects taking decades to be felt, there are other methods that can be put in place now in order for future generations to enjoy the water ways we hope to experience. Eliminating bottom-trawling fishing methods, enacting stricter bycatch measures, and reducing contaminant input into the Australian oceans is a huge step in the right direction, and one that we cannot wait for any longer.