Climate change is rapidly altering Earth's oceans—reshaping coastlines, raising water temperatures, and increasing ocean acidity, all of which can have devastating consequences for the animals that live in them. But at least one marine creature may be more resilient to the changes than previously thought, a new study suggests.
Over time, animals evolve with changes in their environments, but conservationists have long worried that climate change is progressing faster than many species can adapt. But researchers at the University of California–Santa Barbara thought that something called transgenerational plasticity—in which parents' experiences shape their offspring's characteristics—might allow some species to rapidly evolve to a changing ocean.
While parental experiences cannot change the basic genetic code they pass on to offspring, research shows that it can influence which genes are expressed—a process called epigenetic change. The team looked to purple sea urchins off California's coast, where upwelling, or the transport of nutrient-rich water up to the sea surface, causes frequent shifts in the pH of the water, to find out if the adults' exposure to stressors like changing temperatures or pH might alter their offspring's gene expression to better tolerate such stressors.
The researchers plucked adult purple urchins from a rocky reef off the coast of Goleta, California, and brought them back to the lab where, for four and a half months—about the time it takes for urchins to grow reproductive cells (i.e. eggs and sperm)—the urchins lived in one of two seawater tanks, munching on weekly rations of kelp. One tank mimicked non-upwelling conditions with a normal pH, and the other had a low pH to simulate ocean acidification conditions.
After the urchins spawned, the team collected eggs from the females. They crossed all the eggs with sperm from a single male urchin exposed only to non-stressful, non-upwelling conditions—so that any downstream effects on their progeny could be attributed to the mother—and raised the young urchins in either low or normal pH conditions.
The researchers looked closely at the embryos' size and transcriptome—the set of the animals' genetic code that is expressed, or active—to find out if the mother's exposure to harsh conditions gave their offspring any advantage. It turns out that the progeny of mothers who had endured more acidic conditions were larger and better prepared to survive such conditions themselves. For example, the offspring of mothers exposed to more acidic conditions down-regulated genes involved in energetically costly processes like the breakdown in proteins, and up-regulated genes involved in processes that allowed the urchins to tune their internal pH.
The results provide a glimmer of hope for anyone worried about ocean ecosystems. If urchins can pass on tools to their offspring that help them survive rapidly changing conditions, then other marine creatures—like the globe's beleaguered coral reefs—might be able to as well.