Challenge 8: Combating the Effects of Ocean Acidification

## THE PROBLEM

The oceans absorb approximately a quarter of the carbon dioxide emitted into the atmosphere by human activities. When dissolved in water, carbon dioxide (CO2) forms carbonic acid. As a result, in the last 150 years—since the beginning of the industrial revolution—the oceans have become 30% more acidic. This increasing acidity disrupts the carbonate system upon which almost all marine organisms are dependent, from the phytoplankton at the bottom of the food chain, which produce the majority of the planet’s oxygen, to the shellfish, coral, and even finfish that form marine food webs. While our ability to measure changes in ocean acidification has advanced rapidly, innovations to adapt and resolve the impacts remain woefully inadequate or non-existent.

## THE CHALLENGE

Develop technologies and innovations that strengthen resilience and help habitats adapt to the effects of ocean acidification, and mitigate its effects. These may include techniques as wide-ranging as harnessing synthetic biology or microbiology, manipulating ecosystem dynamics, utilizing selective breeding, or geo-engineering ecosystems to change local pH.

## PROBLEM STATEMENT

The ocean’s chemistry facilitates conditions for species-rich biodiversity and sets the foundation for many of the cycles and systems that sustain all life. However, human-caused influx of carbon pollution into our atmosphere, which is deposited into our oceans, is drastically altering the chemical makeup of the oceans, threatening the physical, chemical, and biological processes that are necessary for life.

The ocean surface absorbs around 27% of the excess carbon dioxide from human activity, leading to a reduction in pH and shift in the carbonate chemistry of the seas. This particularly affects organisms with shells, including mollusks, corals, and many phytoplankton that form the base of the food chain. Calcification, the process by which organisms create their shells (such as the building blocks of coral), is greatly affected by acidification; as the saturation state of the necessary compounds for shell formation (calcium carbonate) decreases, organisms require more energy for shell formation and maintenance. In some cases, such as is seen with Northeast Pacific pteropods, even adult shells can dissolve in the more acidic water.

Ocean acidity is one of the first changes to be measurable as atmospheric CO2 concentrations rise. Acidity is expected to increase a further 40—50% if CO2 concentrations reach the projected end-of-century concentration according to current emission rates. The oceans have already become about 30% more acidic since the start of the Industrial Revolution, in tandem with a 39% decline in marine species populations in the past 40 years.

This fundamental and ongoing alteration of our ocean’s chemistry threatens the survival of ecosystems in a way not seen in tens of millions of years. Such change will accelerate the rate of erosion for many shell-building creatures and will cause significant biodiversity loss as pH levels become increasingly more acidic.

In a preview of the types of impacts to come, an acidification event that occurred in the Pacific Northwest of the United States led to widespread mortality in young oyster larvae. With over 80% mortality in most oyster hatcheries, an entire industry was placed at risk as a result of more acidic waters. Without reducing atmospheric CO2, acidification will continue to cause widespread changes in the fundamental processes that create the overall structure and function of marine ecosystems. However, the reality is that ocean acidification is an active process, and both natural systems and our communities will have to grapple with its impacts. Innovations to help us and our ecosystems cope with ocean acidification will be a necessary step to conserve marine biodiversity.

## EMERGING SOLUTIONS

**Mapping & Monitoring:** The recently- awarded Wendy Schmidt Ocean Health XPRIZE has resulted in dozens of new and improved pH sensing devices providing unprecedented accuracy in environments ranging from coastal waters to the deep sea. The prize was awarded to ultra-high performance sensors as well as sub- $1,000 sensors that can be deployed with minimal effort. This prize has given the conservation community the opportunity to rapidly scale up the measurement of ocean pH. Coupled with advances in measuring the concentration of carbon dioxide, total alkalinity, and dissolved inorganic carbon, scientists’ ability to measure changes to the carbonate system are advancing rapidly.

Scientists with the European Space Agency and several other institutions have recently demonstrated the ability to map surface ocean acidity remotely by using **satellite-based thermal and microwave sensors**. This approach had previously been limited to in-situ sensors, which are difficult to place and maintain in remote ocean locations. The newly demonstrated technique holds the promise of improved global measurements of ocean acidification, and may lead to the development of additional space-based sensors, though it is limited to the surface and open- ocean environments.

In addition to a diversity of useful sensors, some notable innovations in how monitoring can be accomplished were revealed during the Ocean Health XPRIZE. One notable example is SmartpHin, a surfboard-fin that includes pH, salinity, and/or temperature sensors. SmartpHin wirelessly downloads data after a surf session and integrates it into cloud-based analytics and data repositories. This type of citizen science application is critical for cheaply scaling up the global monitoring of the ocean.

Assimilating this increasing data stream on ocean acidification into both science and management remains an area of critical need. Moving from data to acidification forecasting systems, which would allow targeted interventions in local habitats, remains a rich opportunity for innovation.

**Adaptation&Geo-engineering:** Corals, like many shelled organisms, make their skeletons out of calcium carbonate, making them vulnerable to changes in ocean acidity. Recently, scientists have begun to identify species and populations of coral that are adapted to large fluctuations in pH, opening the possibility of selective breeding, transplants, or genetic engineering to produce more robust coral species in areas of high concern.

The Paul G. Allen Ocean Challenge identified several finalist projects that are now being funded to expand adaptation techniques. Leading innovations include modifying ecosystem dynamics through the use of seaweed that can mitigate local pH, human-assisted evolution by changing the species abundance and makeup in a habitat to produce greater ecosystem level resilience to acidification, and genetically engineering corals to extend their functional range and resilience to the more acidic and warmer conditions predicted for the oceans of the future.

Lawrence Livermore National Laboratory (LLNL) has recently demonstrated a chemical process for capturing CO2 from the air, which results in the production of hydrogen and an alkaline solution (carbonate) [Rau et al, 2013]. Although the process requires energy input, if it were run with renewable electricity (possibly from off-peak periods), it could potentially provide a carbon-negative source of hydrogen, and an alkaline solution that could be added to the ocean as a de-acidification measure [LLNL].