Benthic marine animals – those living at the deepest levels of the ocean – may be threatened by increased ocean acidification due to elevated CO2 levels, a new study has found. The study examined how higher acidification affects the behavior of baby barramundi fish.
Baby fish that hatch in the open ocean must follow noise cues that will lead them to find a home in reefs or mangroves where they can grow to adulthood. But higher levels of ocean acidity affect their neurological pathways, causing them to move away from noise cues.
“If baby fish will be unable to find a safe home during their settlement phase the risks of not surviving are high,” said Tullio Rossi, MSc, PhD candidate at the University of Adelaide and the study’s lead author about their findings. “Baby fish could become easy prey for larger fish or starve if they stick around the open ocean for too long.”
“Also, they risk settling in the wrong habitat which is probably just as bad. This would translate in lower levels of population replenishment to their natural habitats,” he added. “Whether this means local or global extinction is still an open question.”
Reversing the “business as usual trajectory of carbon emissions” could help us avoid the most serious effects of ocean acidification, said Mr. Rossi. He thinks the outcome of the recent Paris climate talks (COP21) are a step in the right direction. “COP21 is just the beginning and now serious action from countries and individuals is needed in order to reach the targets,” he said.
“When it comes to ocean acidification, reducing carbon emissions is the main solution,” said Mr. Rossi. “However, estuaries where barramundi larvae usually settle often have higher seawater CO2 concentrations than the open ocean due to various natural and human influences that will act on top of the effect of increasing human CO2 emissions.”
“If we reduce human influences on estuaries and rivers (e.g. reduce nutrient pollution) we might partly mitigate these additional effects that lead to even higher CO2 values in estuaries than ocean acidification alone,” he said.