Small "weedy" fish described as the "cockroaches" of the ocean would dominate the world's seas if ocean acidification continues at its current rate, according to researchers at the University of Adelaide on Friday.
For the first time, researchers have successfully managed to demonstrate the effects of ocean acidification, and according to University of Adelaide marine ecologist Prof. Ivan Nagelkerken, fish diversity would be reduced as a result of changes to the ecosystem.
In a statement released on Friday, Nagelkerken said ocean acidification negatively affected large sea plants such as kelp, which is used by medium-sized predators to hide from larger predators.
He said if kelp disappears but "low grassy turf" remains, as happened in the university's studies, then smaller, "weedy" species would survive and thrive due to having fewer predators and more places to hide.
"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," Nagelkerken said on Friday.
"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.
"The result is a lot of what are known as weedy species, somewhat the marine equivalent to rats and cockroaches, plenty of them around but no-one really wants to eat them."
Nagelkerken said ocean acidification had one major negative effect, and that was that biodiversity within the ocean would be lost due to having higher numbers of fewer species of fish.
"If we look at the total number of fish we actually see that these increase under ocean acidification but local biodiversity is lost," Nagelkerken said.
"There are increases in the abundance of food such as small crustaceans and snails and, because the dominant species tend to win almost all combats with other species and are attracted to food much faster, their numbers rise."
Nagelkerken said his team conducted the ocean acidification study in a "shallow-water temperate kelp ecosystem" to get "a peek into what future ecosystems might look like".
Nagelkerken said the future effects of ocean acidification could be further mitigated by restricting the overfishing of those medium-sized predators to ensure the natural food chain remains intact.