Fixing ocean acidification requires both cutting the root cause (CO2 emissions) and actively restoring the ocean’s chemistry. Since the start of the Industrial Revolution, the ocean’s surface pH has dropped from about 8.2 to 8.1, a shift that sounds small but represents a 30% increase in acidity. No single solution can reverse this on a global scale, but a combination of approaches, from dissolving minerals to growing seaweed to electrochemical engineering, can slow the damage and protect vulnerable ecosystems while emissions reductions take effect.
Why the Ocean Is Becoming More Acidic
The ocean absorbs roughly a quarter of the CO2 humans release into the atmosphere. When CO2 dissolves in seawater, it forms carbonic acid, which lowers pH and reduces the availability of carbonate ions that corals, shellfish, and many plankton species need to build their shells and skeletons. This process has been accelerating alongside rising emissions, and it won’t reverse until atmospheric CO2 concentrations stabilize or decline. Every serious strategy for fixing ocean acidification starts with reducing fossil fuel use, because the ocean will keep absorbing excess CO2 as long as we keep producing it.
Adding Minerals to Restore Ocean Chemistry
The most widely discussed direct intervention is ocean alkalinity enhancement: dissolving naturally occurring minerals in seawater to neutralize acidity, much like adding an antacid to an upset stomach. This mimics the natural weathering of rocks, which has regulated ocean pH over millions of years. The difference is speed. Natural weathering is far too slow to keep pace with current CO2 emissions, so researchers are exploring ways to accelerate it.
Olivine, a green mineral abundant in the Earth’s mantle and in mining waste, is a leading candidate. When olivine dissolves in seawater, it reacts with CO2 and converts it into stable bicarbonate. One ton of olivine can theoretically sequester up to 1.25 tons of CO2. Limestone works too, though it captures less CO2 per ton because its chemistry is simpler: one molecule of limestone reacts with one molecule of CO2.
The practical challenges are significant. Olivine dissolves slowly in cold water, and its breakdown can be limited by silicic acid buildup, which acts like a chemical brake on further dissolution. Crushing the mineral into fine powder speeds things up but requires energy. There are also ecological concerns. Dissolving large quantities of olivine could raise the pH in rivers and coastal zones to levels that disrupt local ecosystems. Heavy metals present in some olivine deposits could leach into the water. Large-scale environmental assessments are still needed before deployment moves beyond pilot projects.
Electrochemical Carbon Removal
A newer category of technology uses electricity to split seawater (or a salt brine) into acid and base streams. The base, typically sodium hydroxide, is returned to the ocean to increase alkalinity. This approach allows precise control over how much alkalinity is added and where, which is a major advantage over mineral dissolution.
There are two main variants. One simply adds the base to boost the ocean’s capacity to absorb CO2 from the air over time. The other goes a step further by first acidifying a batch of seawater to force dissolved CO2 out as a gas, which can then be captured and stored. This second approach requires pumping much larger volumes of seawater through the system, which drives up both equipment and energy costs.
Both methods produce hydrochloric acid as a byproduct, roughly 1 to 1.2 tons of acid for every ton of CO2 removed. Disposing of or neutralizing that acid safely is an unsolved logistical problem at scale. The energy source matters enormously: if the electricity comes from fossil fuels, the process could generate more CO2 than it removes.
Seaweed and Kelp as Local Buffers
Kelp forests and seaweed farms absorb CO2 through photosynthesis, and the water flowing through them becomes measurably less acidic. Studies measuring pH inside and outside natural kelp forests have found increases ranging from 0.01 to 0.8 pH units in the surrounding water. That’s a wide range, and the effect depends on the density of kelp, water flow, and time of day (photosynthesis only happens in daylight).
This won’t fix ocean acidification globally. The pH boost is localized and temporary. But for specific high-value ecosystems like coral reefs or shellfish beds, strategically placed seaweed cultivation could create pockets of less acidic water that help vulnerable species survive. Seaweed farming also produces a harvestable crop, which makes it one of the few approaches with a built-in economic model.
Protecting Shellfish Right Now
While large-scale solutions remain in development, some industries are already adapting. Oyster hatcheries along the U.S. Pacific coast were among the first to feel the economic impact of acidification, when upwelling events brought corrosive deep water into their intake systems and killed larvae by the billions. Their fix has become something of a success story in localized mitigation.
Hatcheries now dose their incoming seawater with soda ash (sodium carbonate) to raise pH back to around 8.0 to 8.1. Staff monitor temperature, pH, dissolved oxygen, and salinity twice daily and adjust dosing continuously based on ambient conditions. The goal is to push the aragonite saturation state, a measure of how easily shell-building organisms can form their calcium carbonate structures, to levels well above the corrosive threshold. This approach works for enclosed facilities but isn’t practical for open-ocean shellfish beds.
What the Law Currently Allows
International regulation of ocean-based interventions is still catching up to the science. The London Protocol, which governs dumping of materials at sea, was amended to address marine geoengineering, but those amendments have not entered into force. In practice, this means there is no binding international framework specifically regulating most alkalinity enhancement or electrochemical removal projects.
Ocean fertilization (adding iron or nutrients to stimulate phytoplankton blooms that absorb CO2) is more tightly controlled. In 2008, parties to the London Convention agreed that ocean fertilization beyond legitimate scientific research should not be allowed. At their 2023 meeting, parties went further and urged that all marine geoengineering activities other than legitimate scientific research should be deferred, given the remaining risks and uncertainties. CO2 injection into sub-seabed geological formations is explicitly permitted under the protocol’s approved list, making it one of the few ocean carbon removal methods with a clear legal pathway.
What a Realistic Path Forward Looks Like
No single technology will reverse ocean acidification. The scale of the problem, trillions of tons of dissolved CO2 spread across 1.3 billion cubic kilometers of water, dwarfs even the most ambitious geoengineering proposals. The most realistic path combines aggressive emissions cuts with a portfolio of ocean-based interventions, each suited to different scales and settings.
Alkalinity enhancement with olivine or limestone could eventually operate at a meaningful scale if environmental risks are well understood and managed. Electrochemical methods offer precision but need cheap clean energy and a solution for acid byproducts. Seaweed cultivation and hatchery buffering can protect specific ecosystems and industries right now. All of these buy time, but none replace the need to stop adding CO2 to the atmosphere in the first place.