Ocean acidification occurs when the pH level of seawater decreases, which is most frequently caused by the ocean absorbing excess CO₂ from the atmosphere. Ocean acidification has negative effects on a variety of ocean ecosystems and life forms, including clams.

This article will explain how clams are affected by ocean acidification, as well as the importance of clams to ecosystems, people, and the economy.

Background information: Ocean Acidification Infographic

Table of Contents

How Are Clams Affected by Ocean Acidification?

The Importance of Clams

The Importance of Clams to the Ecosystem

The Importance of Clams to People and the Economy

How Are Clams Affected by Ocean Acidification?

Clams and other shell-forming marine species are particularly vulnerable to ocean acidification. As rising acidity in seawater reduces the number of carbonate ions, shell-forming organisms like clams don’t have enough carbonate to build their shells. Here are some of the negative effects of ocean acidification on clams.

Thinner Shells 

Hard and healthy clam shells are made from the combination of carbonate ions and calcium ions (both naturally present in seawater). When ocean acidification increases, the amount of available carbonate ions decreases. As a result of ocean acidification, clams have fewer resources to develop or reconstruct their shells, causing them to become thinner over time. According to research, the thickness of clamshells significantly reduces after only 3 months of exposure to acidic seawater.

Smaller Clams

Based on the result of an experiment in 2010, juvenile clams that are exposed to acidic water don’t grow as large. In acidic water, clams have less carbonate to develop their shells, so they adjust to the low availability of their environment by using less carbonate, and thus not growing as large.

Increase in Mortality Rate

The negative effects of ocean acidification on clams don’t stop at the shell’s durability and growth. According to research, clams that are exposed to ocean acidification show an increase in mortality rate after 6 months. If ocean acidification continues to rise, this will pose a serious threat to the ecological balance of marine ecosystems and the people who rely on shellfish – particularly clams, in the aquaculture industry, which covers 38% of production globally.

The Importance of Clams

Clams play an unexpectedly important role in maintaining a healthy ocean ecosystem and provide products that benefit both marine life and people. However, the increasing threat of ocean acidification puts the important services that clams provide at risk. Here are some of the ways clams are important to ecosystems and people.

The Importance of Clams to the Ecosystem

Seawater Filtration

Considered filter feeders, clams filter seawater through their respiration and feeding process. The water flows into the clam through their cilia, and all the particles that are pulled in are trapped by their gills and transferred to their mouth to feed, while the filtered seawater is released back into the ocean. This filter-feeding activity contributes to maintaining the ocean’s water quality.

Here is an example of an experiment conducted by the University of Florida/IFAS that demonstrates the efficiency of clams in water filtration:

Ocean Nitrogen Remover

Clams accumulate nitrogen by filtering water and feeding on phytoplankton, which are rich in nitrogen. When clams are removed from the ocean, nitrogen is also removed. Through shellfish culturing and farming, clams can be utilized in nutrient bioextraction, the removal of nitrogen from the seas. This can help create the right balance of nutrients in the ecosystem. Clam’s nitrogen uptake can also help bodies of water prevent excessive algae growth that often results from too much nitrogen in the water.

Natural Nutrient Cycling 

Clams cycle nutrients within an ecosystem, which help other plants and animals thrive. After digestion, clams distribute nutrients through their nitrogen-rich urine and fecal deposits that fertilize various types of marine plants such as kelp.  Other marine species such as krill, sea urchins, and crabs rely on these nitrogen-fertilized plants for food.

Carbon Sequestration

Clams are also considered a carbon sink because they utilize carbon to produce calcium carbonate to develop their shells. This contributes to the sequestration of dissolved atmospheric CO₂ , which can help take carbon out of the atmosphere. This in turn can help reduce climate change and ocean acidification. 

If the ocean continues to acidify, we might lose a great number of clams and other shellfish populations. Without the services that clams provide, the ocean may face an ecological imbalance that would affect many marine species. 

The Importance of Clams to People and the Economy

How Clams Benefit Aquaculture and the Tourism Industry 

Shellfish farming, including clam farming, is very common in coastal areas. Many people that are living in these areas rely on clams as a main source of income. For example, in 2014, the clam farming sector in Washington County, Maine employed around 640 individuals. Clamming generates many economic advantages, such as clamming-related employment possibilities, the chance to expand tourism through the clam business, and tax revenue to strengthen various programs and services.

Another example of clams’ benefits to the economy is giant clam ecotourism in Samal Island, Philippines. Today, local communities on the island, as well as resort owners, are collaborating to protect giant clam species, which increases tourism and creates new employment opportunities for seniors and women on the island. Clam tourism also generates revenue to improve community programs and services. 

With higher mortality rates, smaller sizes, and poor clam quality, the clam aquaculture and tourism sector as a whole may suffer due to ocean acidification. These negative consequences of ocean acidification on clams may harm people who rely on clams for a living, as well as the local economy that majorly depends on the clam industry.

Health Benefits from Clams in the Diet

Eating clams provides more than great flavor, as clams also provide seafood eaters with various health benefits and nutrients. Here are some examples: 

• Clams are rich in vitamin b12, zinc, and iron, nutrients that are important in boosting the immune system.
• Clams also provide collagen, which is important for our joints, skin, and bones. 
• Clams contain iodine, which is important to thyroid hormone production in our body. 
• Just like any other fish, clams are rich in omega 3 fatty acids. This fatty acid is great for maintaining a healthy heart.
• Clams are a good source of choline. This nutrient is essential for liver protection against diseases such as the fatty liver. A study also suggests that choline could prevent or lower the risk of having Alzheimer’s disease. 
• Clams are rich in selenium, which can increase male fertility. A study found that consuming shellfish like clams improves sperm motility.

However, research has found that clams’ exposure to ocean acidification significantly increased the amount of cobalt that clams absorb. This could be toxic to people who eat clams and may put their health at risk if the cobalt is highly concentrated. This is an indication that if ocean acidification continues, it could negatively impact not only the shellfish industry, but also human health.