Rising CO2 Levels In Oceans Disorient Fish Navigation
Tests on clownfish larvae showed they became disoriented and were unable to find a suitable place to live if they were raised in seawater that had absorbed carbon dioxide from the atmosphere.
The effect is potentially devastating for a wide range of fish populations because many rely on odours in seawater to seek out the right habitats to live in, according to researchers investigating the impact of greenhouse gas emissions on marine life.
The world’s oceans soak up vast quantities of carbon dioxide released by burning fossil fuels. By absorbing the gas, oceans become more acidic.
Global ocean pH has dropped around 0.1 points since pre-industrial times. But with increasing carbon emissions expected, this pH is predicted to fall a further 0.3 to 0.4 points by 2100.
In the study, scientists checked how well the larvae followed odours in normal seawater, which has a pH of 8.15, and compared it with their performance in slightly acidified seawater that mimics ocean conditions expected in 2100 and beyond.
At a pH of 7.8, the larvae stopped following odour trails released by reefs and anemones. Instead, they homed in on scents they normally avoided, including those released by plants and other organisms which thrive in the wrong kinds of habitat for the fish. The larvae also lost the ability to use smell to distinguish between their parents and other fish.
At pH of 7.6, the larvae were unable to follow any kind of odour in the water, and instead swam in random directions. [Via]
