Study predicts changes in marine ecosystems

Study predicts changes in marine ecosystems

A new study based on the first global survey of marine life by scuba divers has provided fresh insights into how climate change may affect marine ecosystems.

A new study based on the first global survey of marine life by scuba divers has provided fresh insights into how climate change may affect marine ecosystems.

The research, published in the research journal Science Advances, predicts that as the oceans warm, fish – which appear to be superior predators in warm water – will extend their ranges away from the equator and cause a decline in the diversity of invertebrates such as crabs, lobsters, sea urchins and octopus. This is the first evidence of how ecological interactions affect marine species’ abundance at global scales.

Using data collated by the citizen science project Reef Life Survey (RLS) and including divers from New Zealand, the University of Tasmania-led research team found the total number of fishes and large invertebrates seen underwater changed little from the tropics to polar latitudes.

However, while fishes were more numerous in the tropics they became progressively rarer towards colder latitudes, while large invertebrates showed the opposite pattern.

Lead author and RLS founder, University of Tasmania Professor Graham Edgar, said this distribution is changing as waters become warmer, and will affect food webs, ecosystems and fisheries worldwide.

Related research by co-author University of Auckland Associate Professor Mark Costello found the global distribution of marine species is highly correlated with sea temperature, either at latitude or depth, with fewer species towards the poles and deep-sea.

“The effects of climate change on marine life vary greatly between geographic regions,” Associate Professor Costello says.

“In South Eastern Australia and Tasmania the ‘tropicalisation’ of marine life is already underway but similar effects have not yet been detected in New Zealand.

“Previous research suggested that climate change would directly affect the range of species due to rising temperatures. We found this is not the end of the story. This study showed that species’ distributions reflected not only their preference for particular temperatures and environmental conditions but also ecological interactions.

“As fish extend their range into warming waters further from the equator so will their impact on the abundance of large mobile invertebrates, with consequences for both the broader ecosystem and human activities such as fishing.”

Ongoing monitoring of marine life at both local and regional levels is needed to allow the early detection of such changes. This would allow fisheries and conservation management to adapt so as to minimise the social and economic impacts, and potentially benefit from the changes.

Professor Edgar concluded that “species monitoring of shallow waters at this geographic scale is only possible with the support of citizen scientists, such as the RLS divers who contributed data to the latest study. RLS data now includes information on 4000 species in 50 countries, allowing a better understanding of how and why species are distributed while also providing an early-warning mechanism for climate-induced changes.”

The Reef Life Survey involves hundreds of scuba divers around the world, including staff and students from the University of Auckland’s Leigh Marine Laboratory.

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