The ecological consequences of a predator going on the blink can be catastrophic. Single species can rampage out of control with their natural checks and balances removed, even if the predator is just a snail. Paolo Domenici, from CNR-IAMC, Italy, and Patricio Manríquez, from CEAZA, Chile, explain that the large marine snail Concholepas concholepas, a Chilean delicacy known as ‘loco’, resides along the length of the rocky Pacific coast of Chile and Peru where it dines on several species of mussel, including Semymitilus algosus, ensuring that the mussel does not exclude other species. In addition to maintaining biodiversity along the shoreline, the snail is prized by small-scale fisheries, making it vital that we understand the potential impact of rising sea temperatures and CO2 levels on this species as we continue pumping greenhouse gases into the atmosphere. Because elevated CO2 levels in water can affect the behaviour of predator and prey alike, Domenici, Manríquez and their colleague Rodrigo Torres decided to find out more about the impact of future climate scenarios on this key Chilean species.
As the lateralization (handedness) of some animals – the direction that they prefer when turning – can alter as CO2 levels rise, Domenici and Manríquez measured the turning preferences of 40 juvenile locos that had experienced modern-day CO2 levels and temperatures by tempting them through a T-shaped maze with a delicious morsel of S. algosus placed behind a Plexiglas wall. At the end of the channel, the snails were forced to turn either left or right before circumnavigating the obstruction to receive their reward. After filming the snail's painstakingly slow progress eight times, Manríquez then measured whether the snail turned left exclusively, was right handed, had a slight preference for one or the other direction, or was ‘ambidextrous’. Then, Manríquez and Torres began the arduous task of maintaining each of the snails in their own individual mini biodomes for 6 months, setting the temperature at either 15°C or 19°C and the CO2 level at either 500 μatm (current levels) or 1400 μatm (future levels), before retesting their handedness.
While the snails that had been residing in modern (500 μatm CO2) mild and warm climate scenarios had retained their handedness, preferring to turn to the side that they had favoured 6 months earlier, the snails that had experienced the future (1400 μatm CO2) mild and warm climate scenarios had lost their earlier preference and now had a completely different turning behaviour. And when Domenici analysed the snails’ overall performances, it was clear that the snails that had been reared in warm future climate conditions were slower when they negotiated the maze, and both groups of future CO2 snails took longer to decide which direction to turn. The higher CO2 climate also seemed to impair the ability of the snails to follow their noses and avoid the barrier, often colliding with the obstruction as they attempted to manoeuvre around it, while the snails that had been kept in a lower CO2 environment negotiated the barrier without impediment.
Increases in CO2 levels similar to those that are predicted to occur by the end of the century had clearly changed the behaviour of this key predator on the rocky Chilean coast and affected the ability of the animals to repeat behaviours that were previously hard-wired. And Domenici is concerned about the effect that future change may have on this delicate ecosystem, saying, ‘The negative effects of ocean acidification on locomotion traits associated with prey-finding may cause cascading effects beyond those described at the individual level, such as predator–prey population dynamics and community structure’.