Ocean acidification is concerning to say the least. As a result of climate change, the oceans have warmed at an alarming rate. This causes issues at the poles, where melting glaciers and warming waters raise sea levels, and in the tropics as coral reefs are lost to bleaching. These are only a few of the problems that are now common in our current climate. But what if I told you that there are some benefits to the acidification of our oceans? “Benefits” may be a stretch; however, there are numerous ocean-dwelling species that could adapt well to the increased carbon dioxide in the ocean.
In a controlled experiment by German, Swedish, and Norwegian scientists, herring larvae surprisingly thrived in environments where CO2 levels were high. Specifically, these scientists created an environment based on predictions of CO2 levels at the end of the century and found that these herring larvae are actually predicted to fare better in the future than they do at present.
One reason is because herring spawn mostly near the ocean floor where CO2 levels are highest. As a result, herring larvae have adapted to the changing oceans more so than, for instance, cod which spawns near the surface. More CO2 in the oceans in the future could mean a flourishing herring population.
Another reason herring seem to thrive in these conditions is also due to their increased food supply in CO2-concentrated oceans. This evidence goes directly against a 2014 study that concluded that herring populations suffer from malnutrition and organ damage due to one glaring difference: studies of contemporary herring populations consider the damage rising CO2 levels have caused to herring food supplies. Scientists predict that in the future, increased algae blooms will produce a booming population of zooplankton (a herring food source). This, in turn, would improve herring survival rates by 20 percent.
Some shellfish and snails have also been studied for their resilience to their changing habitats. Most marine species that rely on a shell for protection are experiencing troubling issues. Due to the acidification, the carbonate that makes certain species’ shells is being dissolved faster than it can calcify. The shells of the tiny marine snails develop deformities that renders them vulnerable. Although this is the case, Marine snails, like herring, benefit from an increased food supply of algal turf near the carbon dioxide-rich ocean vents where they live. This is good for the snails because it enables them to adjust to their new environment without any loss to their food supply.
Some Lobster, Crab and Shrimp
While herring and tiny marine snails benefit from an increased food supply, certain types of lobster, crab and even shrimp are benefitting from reinforced exoskeletal protection thanks to ocean acidification. For the blue crabs of the Chesapeake and American lobsters, the amount of bicarbonate in acidified waters has made it easier for them to build stronger shells (even while other marine life struggle to do the same).
This isn’t completely good news, however. While shells for certain species of shrimp do indeed harden, the transparency of their shells (which these specimen rely on for proper camouflage against predators) lessens. This means one of the main evolutionary protectors shrimp have against predators is severely at risk. Additionally, the growth rate of the blue crab has raised alarm in marine biology circles. Yes, the exoskeleton of the blue crab is stronger in adulthood, but with a slow growth rate, adolescent blue crabs will become more susceptible to predatory attacks than before.
Ocean Acidification: Too Complex for a Single Narrative
The lesson here is that ocean acidification’s impact on marine life isn’t as simple as the current narrative suggests. There is no doubt that the carbon dioxide in the oceans is wreaking havoc on the delicate ecosystems. Coral reefs are dying. Algae blooms are suffocating the marine food chain and causing the rise of dead zones. And yet, evolutionary adjustments are proving that some species have a hopeful shot in surviving a bleak future.