Ocean acidification could tamper with marine animals’ sense of smell and the shape of signaling molecules.
A pair of spiny lobsters locks antennae as they battle on the gravel-strewn bottom of an aquarium. The two grapple, grabbing legs and jousting with their long spines. Their aggressive actions extend beyond the show of force: the crustaceans also fire off chemical signals by peeing at each other.
A pair of spiny lobsters locks antennae as they battle on the gravel-strewn bottom of an aquarium. The two grapple, grabbing legs and jousting with their long spines. Their aggressive actions extend beyond the show of force: the crustaceans also fire off chemical signals by peeing at each other.
“They’re actively signaling as they’re fighting,” says Charles D. Derby, a sensory biologist at Georgia State University whose lab studies these underwater wrestling matches, along with other crustacean behaviors. Lobster urine, released from the face near the base of the antennae, contains an array of compounds, including chemical cues to an animal’s sex and social status.
Lobsters are just one of myriad marine animals that rely on molecular missives. Behaviors such as finding meals, choosing habitats, avoiding predators, seeking sex, and engaging in social encounters “are all driven by chemistry, at least in part,” Derby says. By playing key roles in how critters act and relate to each other, chemical signals affect the distribution of organisms in an ecosystem. Chemoreceptors are found not only in noses or mouths; in marine animals, they also show up on fins, limbs, or, as in lobsters, antennae that they flick back and forth.
A changing climate may make chemical communication for sea creatures more challenging. By the year 2100, the pH of the ocean—currently about 8.1—is expected to drop to 7.7 if atmospheric carbon dioxide continues to rise. Over the past decade, research has revealed how sensitive chemoreception systems are and how they may take a hit from human activities that cause pollution, warming waters, and ocean acidification. For instance, higher CO2 levels in the water cause juvenile sea bass to lose sensitivity to some smells. In the wild, that could make it harder for the fish to find food and can render them more vulnerable to predators, says Peter C. Hubbard, an electrophysiologist at the Center of Marine Sciences in Portugal. And for migratory fish, such as salmon, lowered olfactory sensitivity may mean difficulty in navigating rivers for spawning.
Many studies have reported changes to fish olfaction and behavior with increased CO2 levels. Recently, a group of marine scientists has raised doubts about the data in some of these papers and the methodology the studies used to test behavioral changes in fish due to increased CO2, a controversy that has cost the field some of its credibility.But many researchers agree that acidification would impact ecologically and economically important species through changes to the water’s chemistry. That makes it important to investigate the underlying mechanisms and the magnitude of the effects. Understanding such mechanisms could help make sense of confusing, difficult-to-replicate behavioral findings. So scientists continue to work to untangle the basic workings of marine chemoreception, from identifying signaling molecules to finding the receptors that they bind.
Wilke C., in press. Climate change could alter undersea chemical communication. ACS Central Science. Full article.
