Last updated April 12, 2018 at 1:28 pm
Acidification is leading marine animals astray.
The behaviour of larvae of the Australian barramundi or Asian seabass (Lates calcarifer) is being affected by acidification of seawater.
It’s not just birds and animals that are being led astray by the impact of humans on their natural environment. It seems fish are affected too.
A new study from the University of Adelaide suggests that baby fish will find it harder to reach secure shelters in future acidified oceans, putting fish populations at risk.
The researchers have described how barramundi larvae in high CO2 conditions, which are predicted for the turn of the century, turn away from the ocean noises they would normally be attracted to. They are instead attracted to other sounds – noises produced by the wrong sort of habitats and ‘white noise’.
“Oceanic larvae – hatchlings or baby fish – from quite a few species of fishes and invertebrates listen to sounds of coastal ecosystems,” said project leader Professor Ivan Nagelkerken, from the University’s Environment Institute.
“They use these sounds to guide them from the open ocean, where they hatch, to a sheltered home in shallow waters, where they can spend their juvenile and adult lives.”
Attracted to the wrong sounds
“Unfortunately the CO2 that humans are pumping into the atmosphere by burning fossil fuels gets absorbed by the ocean and causes acidification, and this causes changes to the behaviour of many marine animals.”
The research, carried out by then PhD candidate Tullio Rossi, compared the activity of barramundi larvae in marine tanks with levels of CO2 that are predicted for the turn of the century against the responses of barramundi larvae in current day CO2 levels.
“We found that while larvae of barramundi are attracted to the sounds of tropical estuaries, larvae raised under future ocean conditions with elevated CO2 were deterred by these natural sounds,” Nagelkerken said. “Moreover, under elevated CO2, larval barramundi were attracted to the wrong sounds.”
The other sounds were noises found on cold water reefs, which are not the correct habitat for barramundi, and artificial sounds or “white noise”.
Professor Sean Connell, from the University’s Southern Seas Ecology Laboratories, says that if ocean acidification causes larvae to be deterred to the sounds of their habitats, and attracts them to irrelevant sounds, they could end up in the wrong habitat or in places where they cannot survive.
“Fewer larvae are arriving in coastal ecosystems, estuaries and rivers could result in smaller population sizes and, in the case of commercial species like barramundi, this could have a significant impact on fisheries, whether it be commercial or recreational,” he said.
“The research also raises questions about future fish populations in areas with unnatural sounds. Will some species be more attracted, for example, to areas where there are a lot of human structures and sounds in and under the water, such as harbours and oil platforms, in the future?”
The paper is published in Scientific Reports.
