You might have heard about ocean acidification and how this is driven by rising CO2 levels in ocean. It's quite a big deal, since it hinders the ability of animals like reef-building coral to produce calcium carbonate shells or skeletons. Besides acidification, there's the issue of rising temperatures that cause fish to migrate to more forgiving waters and, last but not least, a build up of CO2 itself in the water. As the concentration rises, fish become intoxicated and essentially behave as if they're drunk.
This conditions is known as hypercapnia and affects fish once CO2 concentrations in the water reach 650 parts per million. Previously, live fish stored in tanks with elevated CO2 behaved in an intoxicated state in which they seem disorientated and unaware of their surroundings. This renders them vulnerable to predators or unable to find their school of fish. Ironically, they seem lost at sea.
Findings from the lab are sure to happen in the ocean as well if the current trend of burning fossil fuels is allowed to continue. The consequences are unforeseeable, but it can't be any good. Australian researchers from the University of New South Wales, Sydney claim that by 2100 the CO2 concentrations in some of the oceans' regions will be up to 10 times normal levels. Moreover, in 2100 up to half of the world's ocean dwelling life will suffer from hypercapnia, the paper published in Nature states.
“If atmospheric carbon dioxide pollution continues to rise, fish and other marine creatures in CO2 hotpots in the Southern, Pacific and North Atlantic oceans will experience episodes of hypercapnia by the middle of this century – much sooner than had been predicted, and with more damaging effects than thought,” said Ben McNeil, a climate scientist at UNSW and lead author of the paper.
“Very little research has been done on open-ocean species and we just don’t know how many of these fish will react to elevated CO2 levels,” commented Philip Munday, an ecologist at James Cook University, Queensland.
There is of course a variation in how different species react to CO2 concentrations. Atlantic Cod (Gadus morhua), for instance, seems to have a high resilience to CO2 and hypercapnia.
As you might imagine, it's very difficult to model accurately how CO2 concentrations will evolve in the ocean. What's certain is that these will continue to rise per the trendline presented in the graph below. An ocean of drunken fish is not how I imagined 2100 would be.