Each passing day seems to reveal yet another facet of the wicked problem that is the climate crisis. We see storms, droughts, fires, crop failure, invasive species, pervasive disease and habitat loss threatening all life on the planet. But it’s also vital that we consider that which we don’t see. The stuff that’s hidden. Those things that lie beneath the ripples and tides, in our oceans.
We’re pretty disrespectful to our seas. Overfishing, plastic pollution, and ocean acidification form a tripple whammy ticking time bomb seriously pushing life to the brink. Now, you’re likely well informed by this point of depleted fish stocks and the plastic clogging everything up from the inside, but what about ocean acidification? It’s probably not something you give much thought to unless you’re in the field, but here’s why we all need to be more aware of the great shellpocalypse happening right now off our coasts; especially in California, where it’s happening twice as fast as anywhere else in the world.
As atmospheric carbon dioxide increases, the planet does what it can to maintain an equilibrium. The plants and algae take up a significant volume during photosynthesis and this helps (thus the tree-planting incentive remains strong), but our oceans also absorb much of this excess CO2 and acidify as a result. It’s a simple bit of chemistry as carbon dioxide combines with water to form carbonic acid; some of which goes on to dissociate into bicarbonate and free hydrogen ions, thus increasing the pH of the seawater. The result? A decrease in the number of carbonate ions free in solution. And what are the implications of this, you might ask? Chaos for calcifying marine organisms, i.e. anything with a shell.
Calcification, or the precipitation of dissolved ions out of seawater into solid calcium carbonate is an essential process utilized by a plethora of organisms including corals, plankton, urchins, starfish, shellfish and more. As the oceans acidify from all the excess CO2 in the atmosphere, they do what they’ve always done: try to return to equilibrium. So, that means dissolving any calcium carbonate, returning it to free ions to try to mop up some of the excess hydrogen ions (think: the reverse of the process I mentioned above).
To these critters, this process is akin to having the walls of your house thin over time. Eventually, the roof caves in and you are left vulnerable and exposed. The fight for survival becomes almost impossible for some and when this occurs, anything depending on those organisms becomes threatened too. Thus, the basis of a collapsing food chain.
The coral reefs—or, nurseries of our oceans—upon which a quarter of our marine life depends are already struggling with bleaching due to rising sea temperatures. Combine this with reduced calcification and you quickly see the severity of the matter. Then, there are the bivalves such as mussels and clams, upon which millions of people the world over depend on for essential nutrition. These are struggling too. Finally, the calcifying phytoplankton that help to remove some of that CO2 during photosynthesis are becoming depleted. Once they’re gone, there will be an exponential increase in ocean acidification.
A new study has revealed that waters off the coast of California are acidifying twice as fast as anywhere else on the planet. Looking at shell degradation in photosynthesizing foraminifera (phytoplankton), the team of researchers found a significant correlation between acidification and changes in upwellings and currents as a result of extreme climate events.
The California coastline plays host to a diverse array of marine life with the likes of dense kelp forests being some of the richest and most dynamic “gardens of the sea” found anywhere on earth. These habitats are regularly at the mercy of El Niño events that—although natural—are becoming more severe as climate change causes an increase in sea surface temperature. During these events, there is a reduction in the cold, deep ocean swells being brought to the surface (upwellings). This means that the acidifying waters are not subject to replenishment by cool currents from the deep, which also bring with them many nutrients nourishing life in this habitat.
One potential benefit that might come from ocean acidification in these California kelp forests is the potential for reduced urchin populations that are known to decimate kelp beds during El Niño events. Urchins are calcifying organisms and as such, if they are repeatedly subjected to acidic seawater, their populations are likely to become depleted. However, this adds a layer of complexity because these too are an important source of food for things like sea otters. There’s a circle of life and truly we don’t know enough about all predator-prey interactions to be able to predict the exact implications of removing any one species.
The planet does a remarkable job of returning to homeostasis, or equilibrium, when it has an excess of anything thrown at it. But this is only up until a certain point. Past a given threshold, things start to suffer and this is exactly what we’re seeing in our acidifying oceans. Now, more than ever, we need to be supporting leaders and thus policies that respect the urgency of our climate crisis and prioritize the remedies, if we are to have any hope of saving our seas.
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Photo: Kat Kennedy; Shane Stagner on Unsplash