As ocean acidification continues its steady reign worldwide, it is predicted that fish diversity would be much lower in the future, with small “weedy” species dominating the environment, according to a new study published in the Current Biology journal.
After studying species interaction at underwater volcanic vents over three years, researchers at the University of Adelaide concluded that fish diversity in the future would be significantly reduced as a result of ocean acidification.
In such environments, the carbon dioxide (CO2) concentrations are similar to those predicted for the oceans at the end of this century. The research team then compared their findings with that of adjacent marine environments that had current CO2 levels.
"This study was done in a shallow-water temperate kelp ecosystem using volcanic CO2 vents as natural laboratories to get a peek into what future ecosystems might look like. It further shows that forecasting effects of climate change on future ecosystems is impossible if we do not incorporate complex species interactions," said project leader Professor Ivan Nagelkerken, marine ecologist in the University’s Environment Institute
In both surveys and underwater experiments, the researchers demonstrated that in marine environments with high CO2 content, one or two fish species would proliferate while the less aggressive ones would cease to exist.
Professor Nagelkerken elaborated on this, saying, “If we look at the total number of fish, we actually see that these increase under ocean acidification but local biodiversity is lost.”
As a result of ocean acidification, small weedy species—the marine equivalent of rats and cockroaches—would flourish.
Professor Nagelkerken explained: “Small weedy species would normally be kept under control by their predators—and by predators we mean the medium-sized predators that are associated with kelp. But ocean acidification is also transforming ecosystems from kelp to low grassy turf, so we are losing the habitat that protects these intermediate predators, and therefore losing these species.”
One solution to counter this is to reduce overfishing on the predator species. “Strong controls on overfishing could be a key action to stall diversity loss and ecosystem change in a high CO2 world,” Professor Nagelkerken said.