According to the National Oceanic and Atmospheric Administration (NOAA), the ocean absorbs about 30 percent of the CO2 in the air. This causes the seawater to become more acidic and makes carbonate ions less abundant. Carbonate ions are an important building block of structures such as sea shells and coral skeletons and can affect the behavior of other organisms as well. For example, some fish's ability to detect predators is decreased in more acidic waters, which could disturb the food chain. Ocean acidification is affecting the entire world’s oceans, coastal estuaries, and waterways.
What to do? Reducing overall CO2 emissions would be best and we should pursue that avidly. For now, we can sequester carbon with plants.
Ocean plants include: algae, seagrasses, and various varieties of kelp.
Algae includes some 7,000 currently recognized species. The types that anchor to the ocean floor are consumed raw as a vegetable in Asia and are farmed in that region. All varieties of algae are very good at sequestering CO2.
Seagrasses are flowering plants that grow in shallow ocean water just about everywhere. They are important carbon sinks and provide food and shelter to many types of marine life, comparable to coral reefs.
In the US, we are more familiar with kelp. There are about 30 different types of kelp. They grow mainly in temperate zones but have been found in some tropical zones, too. Kelp farming is now happening along the coasts of Japan, South Korea, North America, and Australia.
NOAA sponsored a test farm off the California coast. Washington and Maine universities have run tests on their respective coasts. In none of these tests did the farming activity harm native stands of kelp. In all cases, the farms reduced carbon and nitrogen pollution in local waters. Kelp forests have been shown to capture CO2 in volumes comparable to terrestrial forests. Kelp has the added benefit of reducing acidity in the surrounding water.
One study found that half to three quarters of organic dairy farmers in the northeastern US feed kelp to their cows as a supplement. Kelp is rich in minerals, especially iodine. It also contains a plethora of other nutrients and helps pastured cattle meet their daily nutritional requirements that may not always be met by grass and legumes. Early research also shows that adding kelp to cow feed reduces methane emissions. That would be a boon.
Kelp shows promise as a means of reducing excess CO2. It cannot cure all our problems but it could certainly help.