How Marine Life is Adapting to Ocean Acidification

Of all the myriad environmental problems facing our planet in the modern day, those that are affecting the world’s oceans are the most pressing and extreme. These marine environments are highly-specialized and so are the animals and plants that call them home, so any change in water temperature, quality, or cleanliness, can seriously affect the entire ecosystem. Among these many issues that have begun to force adaptation in ocean life, ocean acidification has seen some of the most egregious and rapid changes.

Ocean acidification is one of the most pressing environmental challenges facing marine habitats. As with so many environmental problems, ocean acidification is caused by human beings, specifically by human-induced climate change. This phenomenon occurs when ocean waters absorb more carbon dioxide (CO₂) from the atmosphere. This causes their pH levels drop and creates a more acidic environment.

This shift in acidity has had a profound effects on marine ecosystems and inhabitants. Those that have been most affected are the organisms that rely on calcium carbonate for their shells and skeletons, such as mollusks, coral, plankton, and crustaceans. As we mentioned earlier, despite the challenges posed by ocean acidification, many marine species have started showing remarkable adaptability. This trend, while worrisome in some capacity, offers scientists hope and insight into how ecosystems might adjust to our ever-changing climate.

In this article, we will define ocean acidification and learn about its profound impact on marine life. We will also look into the incredible ways in which various species have begun adapting to survive in our ocean’s increasingly acidic waters.

What is Ocean Acidification?

As with so many different environmental issues caused by human beings, ocean acidification has already begun to alter the fundamental makeup of our oceans. Much like mircoplastics have altered ocean chemistry by leaching harmful chemicals into the water, ocean acidification has changed them chemical composition of some seawater. Ocean acidification occurs when CO₂ from the atmosphere dissolves into seawater. This forms a compound known as carbonic acid. While not overtly dangerous on its own, this weak acid dissociates into hydrogen ions and bicarbonate, lowering the ocean’s pH and reducing the availability of carbonate ions. The thing is, those carbonate ions are essential for many marine organisms.

As much as this sounds like a novel problem, ocean acidification began a long time ago. In fact, the ocean’s pH has dropped by approximately 0.1 units since the Industrial Revolution, representing a 30% increase in acidity. This change might seem minuscule in the grand scheme of things, but it has already had profound implications for marine ecosystems, especially for calcifying organisms like corals, shellfish, and some plankton species.

This has happened in Earth’s history several times before. The largest period occurred about 56 million years ago. At that time, it altered all life on the planet and forced potentially millions of species to adapt to the new normal. Things returned to relative homeostasis after that, with only a few acidification events occurring between then and now. That said, scientists have noticed that the rate of ocean acidification today is happening faster than it has in the past 300 million years.

Impact of Ocean Acidification on Marine Life

Coral Reefs: The Foundation of Marine Ecosystems

Coral reefs are often referred to as “rainforests of the sea” because they are full of a rich array of biodiverse marine plants an animals. Sadly, these vital ecosystems are among those most affected by acidification. Corals rely on calcium carbonate to build their skeletons, but as ocean acidity increases, it becomes harder for them to calcify. When they can’t make their skeletons properly, their structures become weaker, grow slower, and are more susceptible to damage.

Corals are even more susceptible than most ocean lifeforms to environmental changes because they are such unique organisms, and the warming waters caused by climate change have similarly affected them in a highly negative way.

Shellfish and Mollusks

Shelled animals such as oysters, clams, and mussels also depend on calcium carbonate to build their shells. Acidified waters make it difficult for shellfish like these to maintain their protective coverings, leaving them vulnerable to predators and the environmental stresses caused by pollution and climate change. This, coupled with a persistent problem of overfishing for the past several centuries, has created ripple effects on human industries that rely on these species, such as fisheries and aquaculture.

Plankton

Though plankton might be mostly invisible to the naked eye, these tiny organisms form the vert foundation of the marine food web. Some species, like coccolithophores, rely on carbonate to build their near-microscopic shells. At that size, the ocean acidification can have a much more profound affect on the species as a while. The problem is, a decline in these organisms can have cascading effects on marine ecosystems, impacting species ranging from small fish to large whales.

In the book The Ends of the World , author Peter Brannen, describes the cause and effects of all of our planet’s major extinction events, from the Permian, to the Cretaceous, to our own eventual extinction. He describes that the circumstances leading up to our own demise will likely be predicated by a loss of miniscule, essential creatures such as insects and plankton. Well, if ocean acidification continues unabated, we may well be headed for that end sooner rather than later.

Fish and Marine Mammals

In general, fish and marine mammals are less directly affected by acidification. Nevertheless, the changes in their prey populations and habitats have had an influence their survival. Acidification can also interfere with the sensory and reproductive systems of some fish, making it harder for them to find food or mates.

How Marine Life is Adapting

Despite the challenges posed by ocean acidification, many marine species are showing surprising levels of resilience. While adaptation is not universal, the examples below highlight the incredible ingenuity of life in the face of adversity.

Corals: Selective Breeding and Symbiont Shifts

Corals might be specialized, but they are also adaptable. Indeed, some coral species have already begun to adapt to the increasing acidification and rising ocean temperatures by forming partnerships with more heat- and acidification-tolerant strains of symbiotic algae (zooxanthellae). These algae provide corals with energy through photosynthesis, so switching to hardier strains helps corals survive in less favorable conditions. Additionally, scientists have already begun using selective breeding programs in coral nurseries, which helps to build more resilient coral populations.

Oysters and Shellfish: Local Adaptation

Studies have found that some oyster populations, particularly those in naturally acidic environments like estuaries, have always been more tolerant of acidified conditions. In many ways, these populations may hold the key to understanding the very genetic traits that enable resilience. Several hatcheries are also experimenting with “preconditioning” oysters to acidic water by effectively training them to thrive in increasingly challenging conditions.

Plankton: Genetic Diversity

Despite how fragile they might seem, some plankton species have begun to exhibit significant genetic diversity, which may allow them to adapt more quickly to changing conditions. Recent studies suggest that certain coccolithophore populations can adjust their calcification processes to survive in more acidic waters, though the long-term viability of these adaptations remains uncertain.

Marine Plants: Thriving on Carbon Dioxide

Many oceanic plants are also becoming affected by ocean acidification, but just as many are evolving to adapt. Seagrasses and macroalgae, like kelp, actually benefit from higher CO₂ levels in the water. This is because plants utilize carbon dioxide for photosynthesis. Their growth can offset some of the impacts of acidification by buffering pH levels in some areas, thus creating small refuges for marine life.

There are other so-called “ecosystem engineers” like mangroves, seagrasses, and coral reefs that can help play a vital role in mitigating the effects of ocean acidification. These environments capture carbon and regulate local pH levels in a way that is meaningful to other marine creatures.

Mangroves

Mangroves sequester large amounts of carbon in their root systems and surrounding sediments. This reduces CO₂ in the water, buffering nearby areas against acidification, creating more stable conditions for marine organisms.

Seagrass Meadows

As previously mentioned, seagrasses not only thrive in high-CO₂ conditions but also provide critical habitat for a wide range of marine species. For many species that are currently struggling to adapt, these ecosystems offer a glimmer of hope.

Scientific Interventions to Support Adaptation

We touched on it earlier, but many scientists are also working on innovative strategies to support marine life in adapting to acidification. These efforts include:

Ocean Restoration Projects: Healing Marine Ecosystems

Ocean restoration projects have become critical initiatives in the wake of climate change, pollution, and ocean acidification. These programs are designed to repair damaged marine ecosystems and mitigate the effects of environmental stressors by focusing on meaningful activities such as rebuilding habitats, enhancing biodiversity, and supporting the resilience of marine life.

Coral Reef Restoration

The restoration of our planet’s coral reefs is absolutely necessary for the survival of marine life and, quite frankly, our own species. Coral reefs are among the ecosystems most affected by climate change and ocean acidification, but restoration projects are offering hope for their recovery. Scientists and conservationists use several approaches to rebuild and protect coral reefs:

• Coral Nurseries: Corals are cultivated in underwater nurseries and transplanted to degraded reefs once they reach maturity. These days, scientists gave started selectively breeding corals that show resilience to acidification and warming waters. This, in turn, can create hardier populations that will be able to survive further environmental devastation.
• Artificial Reefs: Structures made from eco-friendly materials, such as limestone or special concrete, have been deployed in areas where natural reefs have been lost to environmental damage. These artificial reefs provide a surface for coral larvae to attach and grow, while also creating habitats for surrounding marine life.
• Microfragmentation: This technique involves corals being cut into small pieces. This works by encouraging fast growth in the smaller corals and has proven effective in rapidly restoring large sections of damaged reefs.

Marine Protected Areas (MPAs)

Governments, conservation organizations, and scientists have created MPAs and Marine Sanctuaries as a way of helping ocean habitats bounce back from environmental stressors. Indeed, the creation and maintaining of MPAs has since become an essential component of ocean restoration. These areas restrict human activities like fishing, mining, and drilling, allowing ecosystems to recover naturally. By reducing outside stressors, MPAs provide a sanctuary where marine species can thrive and adapt to environmental changes, including acidification.

The Importance of Ocean Restoration Projects

Ocean restoration projects not only help repair damaged ecosystems but also enhance their resilience to future challenges; challenges that despite the best efforts and intentions of many, are coming whether we like it or not. By stabilizing habitats, supporting biodiversity, and offsetting the effects of acidification, these initiatives play a vital role in safeguarding the health of our oceans.

Alkalinity Enhancement

Some researchers have even begun to explore ways to increase ocean alkalinity to counteract acidification. This is accomplished by adding substances like crushed limestone to the water. In this way, scientists hope to neutralize excess hydrogen ions and stabilize pH levels. It’s important to note, however, that this would be a huge-scale effort and the calculations required to do it properly kind of boggles the mind. The concept is simple, though, even if it is difficult to quantify.

What Can We Do to Help?

While marine life shows incredible resilience, the trick to fixing the issues lies in reducing the root causes of ocean acidification. Here are some ways individuals and governments can help:

Reduce Carbon Emissions: As always, the main thing to do would be to reduce our carbon emissions by transitioning to renewable energy sources, reducing reliance on fossil fuels, and adopting sustainable practices. All of this will lower the amount of CO₂ entering our atmosphere.

Support Marine Conservation: We need to keep on protecting marine habitats through conservation initiatives and marine protected areas (MPAs). This will help to create refuges for vulnerable species and give them a chance to bounce back.

Promote Sustainable Fishing: As humans, we need to mitigate our consumption of everything we use, including seafood. Overfishing compounds the existing stress already placed on marine ecosystems. Supporting sustainable seafood practices will help maintain healthy populations so they can be fished and cultivated for centuries to come.

Raise Awareness: Educating others about ocean acidification and its impacts can inspire collective action and policy changes.

True Investigator Says…

Though adaptations within marine ecosystems are working to help species adapt to rapid ocean acidification, more needs to be done. The root cause of this, carbon emissions causing changes in our atmosphere and ocean temperatures, needs to be addressed first and foremost. As remarkable as they might seem, these adaptations alone cannot fully counteract the widespread impacts of ocean acidification. To ensure the survival of marine ecosystems, it is essential to pair natural adaptation with robust human intervention and protect our oceans, even from ourselves.