Marine climate worries for scientists

Reef Life survey diver on a South Australian temperate reef. Photo: Graham Edgar.

A new study has indicated that warming oceans are picked to have a cascade effect on New Zealand marine life as marine predators extend their range away from warm waters.

The research, which is based on the first global survey of marine life by scuba divers, 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.

Published in the research journal Science Advances, it 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 fish species and large invertebrates seen underwater changed little from the tropics to polar latitudes.

However, while fish 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, says 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 finds 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,” says Mark.

'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 climate change would directly affect the range of species due to rising temperatures. We find this is not the end of the story. This study shows species' distributions reflect 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, says Mark. This will allow fisheries and conservation management to adapt to minimise the social and economic impacts, and potentially benefit from the changes.

'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,” says professor Graham Edgar.

'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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4 comments

Early warning signals

Posted on 23-10-2017 08:55 | By Papamoaner

Yet another early warning alarm nobody wants to listen to and motor vehicle density continues to increase exponentially. I can remember Professor Peter Barrett at Victoria University in Wellington warning us about climate change more than a decade ago, based upon deep core drilling data in Antarctica, but nobody wants to hear it. If we are starting to notice differences now, that might be because we are now entering the turning point along the horizontal part of the exponential curve. That being the case WATCH OUT WORLD because from here on the curve gets vertical which means changes will accelerate at a rate of knots. Might pay to get the water wings and plastic pants out. And don't forget the dunny paper- we might need it real soon if we don't wake up to these warnings.


Here goes..

Posted on 23-10-2017 11:41 | By overit

Don't they say when the Ocean collapses, then it will affect the land.


Climate

Posted on 23-10-2017 18:04 | By NZer

Can anyone show me a period of time when the climate was always the same.... Um no? Why not? Maybe because climate is continually changing and always will....


@NZer

Posted on 26-10-2017 17:10 | By Papamoaner

Fair comment, but it's not the change or the rate of change that causes concern. Rather the direction of change. Even if it's sinusoidal and eventually reverses direction, the oscillation period might be too great for us to survive.


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