Heating of the world’s oceans could radically reorganise marine food webs across the globe causing the numbers of some species to collapse while promoting the growth of algae, new research has warned. Healthy marine food webs that look like a pyramid, with smaller numbers of larger predatory species at the top and more abundant smaller organisms at the bottom, could become “bottom heavy”. The types of species that could become less abundant in the oceans are the same ones targeted by commercial fishing and also are socially and culturally important to many communities around the globe. In the research, published in the journal Science, researchers at the University of Adelaide recreated a marine habitat in a series of 1,800-litre tanks and then subjected some to temperature and CO2 changes.
After being subjected to higher temperatures and higher CO2 the rocks, he said, were overgrown with turf algae and the sandy bottom had a lot more slimy algae that is toxic to some species. The tanks recreated a habitat off the coast of Adelaide in Gulf St Vincent that was about six metres deep. Many of the species placed into the tanks – including kelp, crustaceans and the multitude of different bacteria on rocks, sand and in sediment – were gathered from the gulf. Native fish and crabs were also added.
Dr Kirsty Nash, of the Institute for Marine and Antarctic Studies at the University of Tasmania, who was not involved in the research, said studying the resilience of marine systems was challenging, and the researchers had struck a balance between what was practically possible while giving an insight into real-world impacts. She said: “Developing this type of understanding is really important if we want to then address questions around the broader consequences of climate change for society, for example, are fisheries likely to suffer as a result of climate change.”
Source: Guardian
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