Ocean Acidification: Marine Life and Fisheries at Risk

What Is Ocean Acidification and What Causes It?

Ocean acidification is a gradual process where the ocean becomes more acidic due to increased levels of carbon dioxide (CO2) in the atmosphere. When CO2 is absorbed by seawater, it reacts with water to form carbonic acid, which then dissociates into hydrogen ions and bicarbonate ions. This increase in hydrogen ions lowers the pH of the ocean, leading to a more acidic ocean.

The pH scale measures how acidic or basic a substance is, ranging from 0 to 14. A pH below 7 is acidic, a pH of 7 is neutral, and a pH above 7 is basic (alkaline). Each whole number on the scale represents a tenfold difference in acidity or alkalinity, meaning even small changes in pH can have significant effects.

Since the start of the Industrial Revolution, atmospheric carbon dioxide levels have risen dramatically due to human activities such as burning fossil fuels, deforestation, and industrial processes. The oceans have absorbed about 30% of this excess CO2, leading to a significant drop in ocean pH. The average seawater pH of surface water has decreased from approximately 8.11 to 8.05 between 1985 and 2021.

While CO2 absorption by oceans forms an important part of the carbon cycle, the shift in ocean chemistry disrupts the delicate balance of marine ecosystems.

How Does Ocean Acidification Threaten Coral Reefs?

Coral reefs are under significant threat from ocean acidification, which is harming their health and the ecosystems they support. Often called the "rainforests of the sea," water corals are home to a diverse range of marine life and provide critical habitats for many species.

Ocean acidification weakens coral skeletons by reducing the availability of calcium carbonate, a key building block for corals. This makes it harder for them to build and maintain their structures, leaving reefs more vulnerable to erosion and storm damage, and slowing their growth. Research shows that coral calcification has declined by up to 10% every decade since the late 1990s.

Acidification also contributes to coral bleaching, where corals lose the essential algae that provide them with nutrients and color. Without these algae, corals become stressed and more prone to disease. The disruption of this delicate balance further harms coral health and reduces their ability to reproduce.

As coral cover declines, the entire reef ecosystem suffers. There is a loss of habitat complexity and biodiversity, affecting species that rely on reefs for shelter and food. The economic and social consequences are also substantial, as we’ll explore later on.

What Adaptation Strategies Are Marine Species Displaying in Response to Ocean Acidification?

Marine species are facing growing challenges from ocean acidification, and while some are struggling, others are showing signs of adaptation. Here are some ways that marine organisms are adapting:

• Behavioral changes: Some marine species alter their behaviors in response to changing ocean conditions. For example, fish may shift their feeding habits or migration patterns to find more suitable environments. Certain species might avoid areas with high acidity to reduce exposure and stress.
• Physiological adjustments: Marine organisms can sometimes adjust their physiology to better cope with acidified conditions. For instance, some species are able to increase their internal production of bicarbonate to counteract the effects of lower pH levels on their calcium carbonate structures.
• Evolutionary adaptation: Over longer periods of time, some marine species may undergo evolutionary changes that enhance their resilience to acidification. Certain populations of marine organisms, like some types of oysters, have shown resilience by developing genetic traits that help them cope with acidified environments.
• Symbiotic relationships: Coral reefs are particularly affected by ocean acidification, but some coral have adapted by forming new symbiotic relationships with different types of algae that are more resilient to acidic conditions. This helps coral maintain their health and function despite changing environmental conditions.
• Physiological tolerance: Certain marine species are exhibiting increased tolerance to acidic conditions. For example, some species of seaweed and algae can continue to grow and thrive despite higher acidity levels, which may help them outcompete less tolerant species and maintain ecosystem functions.
• Habitat shifts: Marine species may move to different habitats that are less affected by acidification. For example, species might migrate to deeper or more alkaline waters where the impacts of acidification are less severe.

These adaptation strategies show how marine life can be resilient, but they also reveal the limits of these adaptations when faced with fast-changing environments.

Which Regions and Marine Environments Are Most Vulnerable to Ocean Acidification?

Certain regions and marine environments are vulnerable to the effects of ocean acidification due to a combination of local conditions and broader environmental factors. These include:

• Coral reefs: Coral reefs, found in tropical and subtropical waters, are highly sensitive to ocean acidification. These organisms depend on calcium carbonate to build their skeletons, making them particularly at risk. Reefs in places like the Great Barrier Reef, the Caribbean, and Southeast Asia are in danger because rapid acidification has weakened their structure, harmony the variety of life they support.
• Polar regions: Polar oceans, including the Arctic and Antarctic, are also at high risk. These areas are experiencing rapid acidification due to the absorption of CO2 from the atmosphere, combined with colder waters that hold more CO2. The impact on polar marine ecosystems, including shell-forming species like krill and certain types of algae, can have cascading effects on the food web.
• Upwelling zones: Coastal upwelling zones, where deep, colder waters rich in CO2 rise to the surface, are particularly vulnerable. Regions such as the coasts of Peru, Chile, and the Northwest U.S. are affected. The naturally high levels of CO2 in these areas are worsened by acidification, impacting local fisheries and marine life.
• Sheltered coastal areas: Coastal areas with limited water exchange, such as estuaries and bays, can experience higher levels of acidification due to the accumulation of organic matter and lower water movement. These environments, like those along the U.S. East Coast and parts of Southeast Asia, are at risk of severe impacts on shellfish and other marine organisms.
• Small island states: Small island nations in the Pacific and Indian Oceans, such as Kiribati and the Maldives, are also vulnerable. Their reliance on coral reefs for coastal protection and livelihoods makes them highly susceptible to the impacts of ocean acidification, which threatens their marine ecosystems and economies.

Each of these environments faces unique challenges that make acidification worse, highlighting the need for targeted research and conservation efforts to protect these important marine areas.

What Are the Economic Implications for Global Fisheries?

Ocean acidification directly impact the livelihoods of millions of people worldwide in the following ways:

• Impact on shellfish farming: Ocean acidification weakens shells and slows growth rates of species like oysters, clams, and mussels. This leads to lower yields and higher production costs. For example, oyster farms in the Pacific Northwest have reported huge losses.
• Rising seafood prices: Reduced fish and shellfish stocks can drive up prices for seafood. Consumers may face higher costs for these products due to decreased availability and increased production challenges.
• Economic disruption to local industries: Communities that depend on fishing for employment and food security are at risk. Lower fish stocks and shellfish yields can undermine local economies and threaten livelihoods. The decline in seafood production also affects related businesses, such as seafood processing and distribution, further impacting local economies dependent on these industries.
• Increased costs for management and adaptation: Governments and organizations may need to invest in research, monitoring, and adaptation strategies to address ocean acidification. These costs can be substantial and impact public funding and resources.

Can Ocean Acidification Affect Drinking Water?

Ocean acidification itself does not directly affect drinking water, as freshwater systems, including lakes, rivers, and groundwater, are typically the sources of drinking water. However, if ocean acidification disrupts coastal ecosystems, such as wetlands and estuaries, it could indirectly impact freshwater quality. Coastal areas act as natural filters for water, and their degradation could lead to saltwater intrusion into freshwater supplies, especially in areas where rising sea levels and coastal erosion are already concerns. This could make water desalination more necessary, increasing costs and resource strain in some regions.

Ready to transform your tap water into a crisp, clean refreshment?

HomeWater’s UPSTREAM™ 4-Stage Whole Home Water Filter is your perfect solution. Our advanced system uses catalytic carbon to effectively remove a wide range of contaminants, including pesticides, herbicides, chloramines, hydrogen sulfide, volatile organic compounds, PFOS/PFAS, heavy metals, sediment, microplastics, and more. With the UPSTREAM™ 4-Stage Whole Home Water Filter, you can be confident that every drop from your tap is safe and great tasting.