The ways in which animals behave and interact with one another have impacts on the structure, function, and health of ecosystems. Sea stars, for example are major predators in marine ecosystems and help control the population of shellfish, such as mussels. The mussels play an important role in water filtration and habitat structuring and are of economic importance around the world. The GlobalChangeBehav project, supported through the Marie Skłodowska-Curie (MSC) programme, investigated how ocean acidification (OA) and ocean warming (OW) may affect the behaviour of marine organisms. Researchers conducted laboratory experiments with blue mussels (Mytilus edulis) and common sea stars (Asterias rubens). “We tested for the effects of warming and acidification on responses to predator cues in mussels, and self-righting behaviour in sea stars, where they return to an upright position after being inverted. We also conducted a meta-analytical review of ocean acidification effects on fish behaviour,” states MSC research fellow Jeff Clements.
Response to predation
Mussels and sea stars are interesting to work with because they are uncephalised – meaning they do not have a concentrated head or brain – yet they exhibit complex behaviours. “They can be used as model organisms as they are easy to maintain in the lab and their behaviours are easy to measure,” Clements explains. “In addition, mussels are economically and ecologically important organisms and understanding how they respond to changes in their environment is critical.” The team observed that mussels exposed to future predicted temperatures stay closed longer than mussels in present-day temperatures, which means they are feeding less. “We found that OW, but not OA, affected mussels' response to predators by causing them to remain closed for a longer period of time after being attacked,” Clements notes. This correlated well with previous reports of reduced survival and growth in blue mussels under future temperatures. It also suggests that mussel behaviour under these conditions may influence their physiology and survival, potentially having major consequences for their populations and the ecosystems in which they play critical roles.
According to Clements: “We found that although OA is a serious issue for many marine organisms, its direct effect on marine animal behaviour does not appear to be as ubiquitous as once thought. From our results, it appears that OA does not affect mussel or sea star behaviour. Furthermore, our meta-analysis of earlier research found that the serious effects of OA on fish behaviour are likely less serious than previously thought.” However, this does not mean that OA does not pose a harm for marine ecosystems, but it does mean that direct effects of acidification on the behaviour of marine animals are likely not as strong as early studies on this topic would suggest. “OA is still a major threat to marine ecosystems, and we cannot ignore its consequences; but direct effects on animal behaviour appear weak,” Clements points out “Given the economic importance of blue mussels, the project’s results will have significant implications for the sustainability of bivalve fisheries and aquaculture and their role in water filtration in the face of marine global change.”
GlobalChangeBehav, blue mussels, common sea star, ocean acidification, ocean warming, Asterias rubens, Mytilus edulis