The acidity of our oceans has been a common concern when it comes to talking about climate change. Ocean acidity is the result of excess atmospheric carbon dioxide being absorbed into the oceans. The more carbon dioxide absorbed into the oceans, the lower its pH level goes, acidifying ocean water and affecting plant and animal life. Some estimates in the past have suggested that the rise in acidity levels is unprecedented.
However, according to a new study published in PLOS Biology, high-profile published accounts detailing worrying trends around ocean acidification and its effects on marine life (fish, specifically) have decreased. But why?
Researchers implemented a meta-analysis that examined studies conducted between 2009 and 2019, all of which focused on how ocean acidity levels were affecting fish life and behaviors—in total, reviewing about 91 different studies from a range of journals. Researchers noted that while studies published early in their time window noted drastic correlations between ocean acidity and negative effects on fish behavior, those correlations quickly fizzled out. The research team suspects this is a key example of the decline effect.
The decline effect refers to scientific claims that, over time, show less and less support. Basically, there was less scientific evidence supporting early findings. It’s quite common in many fields of research. But why is it happening here? Researchers noted two potential reasons driving the decline effect.
The first is publication bias. That is, there’s a tendency to publish research that has big, bold, and eye-catching claims. Studies like these are likely to be published in the more prestigious journals and, thus, have much more visibility. It’s only when we see people replicating existing studies and coming up with different, or lesser, results, that we start to see the entire picture on a specific question. But, the research team noted, studies like that are less likely to get published or pass peer-review muster. That’s why we see less confirming evidence of early claims.
The second reason may stem from sample size. Many of the studies researchers analyzed had smaller sample sizes, limiting what those studies could tell us.
While researchers note that ocean acidification is a severe consequence of human-driven climate change, more research needs to be published to better understand other areas deeply affected by ocean acidity.