Over the past decade, marine scientists published a series of studies warning that humanity’s burgeoning carbon dioxide (CO2) emissions could cause yet another devastating problem. They reported that seawater acidified by rising CO2—already known to threaten organisms with carbonate shells and skeletons, such as corals—could also cause profound, alarming changes in the behavior of fish on tropical reefs. The studies, some of which made headlines, found that acidification can disorient fish, make them hyperactive or bolder, alter their vision, and lead them to become attracted to, rather than repelled by, the smell of predators. Such changes, researchers noted, could cause populations to plummet.
But in a Nature paper published today, researchers from Australia, Canada, Norway, and Sweden challenge a number of those findings. In a major, 3-year effort that studied six fish species, they could not replicate three widely reported behavioral effects of ocean acidification. The replication team notes that many of the original studies came from the same relatively small group of researchers and involved small sample sizes. That and other “methodological or analytical weaknesses” may have led the original studies astray, they argue.
“It’s an exceptionally thorough replication effort,” says Tim Parker, a biologist and an advocate for replication studies at Whitman College in Walla Walla, Washington. Marine scientist Andrew Esbaugh of the University of Texas, Austin, agrees that it’s “excellent, excellent work.”