Often considered the “evil twin” of climate change, take a closer look at what ocean acidification truly entails, its causes, and the far-reaching consequences it holds for marine ecosystems and humanity.

Ocean acidification is a pressing environmental concern stemming from the absorption of carbon dioxide (CO2) emitted into the atmosphere through human activities. As CO2 dissolves into the world’s oceans, it significantly alters their chemical composition, leading to the phenomenon we know as ocean acidification. This process poses a significant threat to marine life and, in turn, affects our own well-being.

In simple terms, ocean acidification refers to the decrease in the pH of seawater as it absorbs CO2. pH is a measure of acidity or alkalinity, with lower values indicating higher acidity. Over the past two centuries, since the Industrial Revolution, the oceans have absorbed approximately one-third of the CO2 emitted by human activities, leading to a significant rise in acidity levels.

The primary cause of ocean acidification is the excess carbon dioxide in the atmosphere, which dissolves in seawater and reacts with water molecules to form carbonic acid. This acidification process alters the delicate balance of carbonate ions in the ocean, making it harder for marine organisms such as corals, shellfish, and plankton to build and maintain their protective shells and skeletons.

You may have heard of the term “coral bleaching” in the past few years, particularly, coral bleaching events in places like the Great Barrier Reef. In 2022, this magnificent reef suffered its sixth mass bleaching event with 91% of reefs surveyed affected.

Coral bleaching refers to the phenomenon where coral reefs lose their vibrant colors and turn pale or white. It occurs when corals expel the symbiotic algae (zooxanthellae) living in their tissues, which provide them with food and give them their color. The expulsion of these algae is often a stress response to changes in environmental conditions. This stress response can be caused by changes in ocean temperature, runoff and pollution, and overexposure to sunlight.

Ocean acidification is best known for its osteoporosis-like effects on shellfish including oysters, clams, lobsters, shrimp, which makes building and maintaining shells difficult for these creatures. Acidification also affects other species vital to the marine ecosystem, including reef-building corals and pteropods.

Coral provides food and shelter from larger fish. The larger fish eat the smaller fish. Blue whales, the largest animals in the world, eat krill. A 2010 study found increased CO2 in the water can kill off krill embryos before they have the chance to develop. From the tiniest creatures to giant whales, this eventually affects all life in the ocean. 

Presently, over a billion people across the globe heavily depend on ocean-derived food as their main protein source. Approximately 20 percent of the world’s population relies on fish to meet at least one-fifth of their animal protein requirements.

The livelihoods of numerous individuals and the economies of both the United States and other countries are closely tied to the thriving marine fisheries and shellfish industries. The decline in fish and shellfish harvests poses a significant threat, particularly to the most vulnerable populations in the least developed nations, where alternative agricultural options are limited.

A 2015 study showed acidification-hotspots across the US posed a threat to the $1 billion U.S. shellfish industry. Globally, areas like Norway, Scotland, and the Caribbean are already being affected. 

Additionally, in laboratory studies, many harmful algal species produce more toxins and bloom faster in acidified waters. A similar response in the wild could harm people eating contaminated shellfish and sicken fish and marine mammals.

Looking even further out, the loss of coral reefs means the loss of storm protection vital to many coastal communities, as well as tourism.

To combat ocean acidification, we must work towards reducing greenhouse gas emissions from various sources, including burning fossil fuels, deforestation, and industrial processes. While these are big tasks, we can take small steps in our own lives in the right direction.

• Use energy efficiently: Opt for energy-efficient appliances, LED light bulbs, and programmable thermostats. Turn off lights and electronics when not in use, and consider using renewable energy sources like solar panels if possible.
• Practice waste reduction by minimizing (or eliminating!) single-use plastics and recycling paper, glass, metal, and plastic items. Composting organic waste can also help reduce methane emissions from landfills.
• Choose sustainable transportation: Walk, bike, carpool, or use public transportation whenever possible. If feasible, consider switching to electric or hybrid vehicles to reduce emissions from fossil fuels.
• Eat a plant-based diet: Limiting meat consumption, especially beef and lamb, can significantly reduce greenhouse gas emissions from livestock farming.
• Choose sustainable products: Opt for products with minimal packaging, eco-friendly certifications, and those made from recycled or sustainable materials.
• Support local and sustainable businesses: Buy locally produced goods to reduce emissions associated with transportation and support businesses that prioritize sustainability.
• Support renewable energy: If you have the option, choose a green energy provider that supplies electricity from renewable sources like wind, solar, or hydro power.

You can calculate your home’s carbon footprint and get more ideas here.