July 1, 2014 — Fish seem like chummy enough creatures, often schooling with fish they’re familiar with to avoid predators and increase the chances of finding a mate. But as carbon dioxide levels rise worldwide, they could lose their ability to recognize each other, in effect becoming “friendless” wanderers who will hang out with just about anybody.
That’s the short version of new research on climate change and fish behavior out of James Cook University in Queensland, Australia. A team led by Lauren Nadler wanted to know how fish will react to ocean acidification caused by more and more human-generated CO2 in the atmosphere. So they created two experimental setups, one with regular ocean water and the other enriched with CO2, and into them dumped a bunch of tropical damselfish. Here’s what those guys look like out on the reef:
Juvenile damselfish ordinarily take about three weeks to bond to the point that they’ll recognize each other. And that is indeed what happened with the control-environment fish, who later chose to school with their childhood buddies. But in the altered one, which had CO2 levels comparable to what the IPCC estimates for 2100, the fish showed signs of developmental impairment: When put among schools of fish they grew up with and with ones they didn’t, they displayed no preference for hobnobbing with their old tank mates. They’d just as soon swim with strangers.