From Bivalves To Blue Crabs: Acidification Brings Challenges To New Marine Life
In school, most students learn to measure acidity or pH with a litmus test. Unfortunately, monitoring the acidity of the ocean is not as simple as dunking a small piece of paper in liquid and waiting for the color to change, and the impacts of acidity changes to marine life are more complex than a simple change in color. Atmospheric carbon dioxide is absorbed by the ocean, which makes it difficult for marine calcifiers (a group comprised of many different organisms, such as molluscs, crustaceans, and corals) to make their own shells and skeletons. Ocean acidification doesn’t just harm these creatures. It threatens our nation’s economic stability, from our $7.3 billion seafood industry to our $101.1 billion recreation and tourism sector. But it doesn’t stop there – it also affects our homeland security.
Ocean acidification increases risk to coastal communities by altering the near shore ecosystems that provide shoreline protection, such as coral reefs and aquatic vegetation. Between direct economic effects and decreased protection for our shores, ocean acidification threatens the $26.8 trillion contribution of coastal areas to the global economy and the 164 million Americans living in coastal watershed counties. Why is the chemistry of seawater changing? Increasing amounts of carbon dioxide in the atmosphere are being absorbed by the ocean. COL, in conjunction with Representatives Sam Farr (CA-20) and Suzanne Bonamici (OR-1) hosted a briefing of ocean experts speaking about these changes generated by ocean acidification and the associated impacts on both marine and human life, including effects on the economy and homeland security.
Bivalve molluscs, more commonly known as clams, oysters, mussels, and scallops, are a substantial component of the seafood industry. On the west coast, these marine calcifiers contribute approximately $110 million annually to the local economy and around 3,000 jobs in rural communities. Dr. George Waldbusser (Associate Professor, Oregon State University) is on the front line of the battle against increasingly acidic waters in the Pacific Northwest, and he provided new research in the fight to keep ocean life healthy. Willapa Bay, Washington, provides the nation with 10-20 percent of all its oysters. Dr. Waldbusser and his colleagues found that increased carbon dioxide levels can curtail the period of time for favorable growing conditions of oyster larvae, which need a certain range for both temperature and water acidity to grow best. “The addition of that anthropogenic CO2 makes the probability of having good times far less,” Dr. Waldbusser explained. He and his colleagues also found excess carbon dioxide reduces the possibilities of oyster larvae being able to survive and reproduce. To mitigate ocean acidification levels on a local scale, Dr. Waldbusser and his colleagues turned to seagrass beds. After growing oysters both inside and outside of seagrass beds, he found that oyster survival was two to ten times higher and oyster growth was two times higher within the beds. Dr. Waldbusser concluded that seagrass is likely responsible for the oysters’ growth spurts because it lowered carbon dioxide levels, setting up better growing conditions.
While you may have read the term ‘ocean acidification,’ the effects of acidification on estuaries are not often mentioned in society today. Estuaries are where fresh and saltwater mix, so acidification still occurs, but not in the same way it happens in the ocean. Estuaries see higher fluctuation in daily pH changes than the ocean does. Dr. Tom Miller (Director and Professor, University of Maryland’s Chesapeake Biological Laboratory) explained that for this reason, the modeling used to predict future impacts of ocean acidification cannot be applied to estuaries. One estuarine species, the blue crab, is the heart of commercial and recreational fisheries throughout the Chesapeake Bay and is an essential part of the ecosystem’s food web. Dr. Miller studies crab growth and food consumption in light of the changing climate, looking at impacts of both warming waters and estuarine acidification. Blue crabs regulate their blood’s pH to deposit calcium carbonate that hardens their carapace, or shell. This shell is shed at different life stages, so the hardening process has to occur throughout their lifetime. When molting during the winter months, crabs go into a period of suspended development (diapause) because of unfavorable temperatures. Now, with increasing average water temperatures, crabs end this diapause a month earlier than usual; Dr. Miller believes that in 50-75 years, the crabs will not undergo a diapause at all. Commercial and recreational harvesting is sometimes regulated based on the time periods when female crabs are still growing to ensure overfishing does not occur. Therefore, changes to the molting and growing periods could cause regulations to be reconsidered.
While Dr. Miller and his colleagues have found that temperatures do have an effect on growth, acidification does not. They concluded that because the environment in which crabs live sees ever-changing pH conditions, the crabs have evolved to accommodate the highly variable acidity. However, they also found that crabs must eat more to cope with the physiological stress of temperature changes – acidified conditions required crabs to work harder to mobilize and re-deposit calcium to harden their carapace, so they had to eat more. Dr. Waldbusser and Dr. Miller’s presentations showed that there is no single way that all marine organisms respond to acidification but instead a wide array of differing consequences. Dr. Miller put the challenge of acidification into simple terms: “probably a few species may be winners, but many more species will be losers.”
The National Oceanic and Atmospheric Administration’s (NOAA) Ocean Acidification Program (OAP) monitors ocean acidification and examines and analyzes its impacts. The program’s deputy director, Dr. Dwight Gledhill, attested to the far-reaching effects of acidification, which do not just harm the environment. There are socio-economic impacts of acidification, and Dr. Gledhill explained that the objective of OAP is to “assess the vulnerability of the U.S.” OAP not only monitors the progressing acidification of the earth’s waters via ship observations, surveys, and buoys, but also funds and executes modeling studies that provide projections on how ocean acidification will affect fisheries, aquaculture, and coastline protection by coral reefs. Dr. Gledhill spoke of OAP research in the east coast’s Gulf of Maine, which is a prime location for monitoring acidification rates and the resulting effects on marine life. He also noted that many marine organisms are most vulnerable to acidification in their early life stages when they do not possess the physiological capabilities to react to and compensate for changes in the environment. Over the past few decades, an increasingly large portion of fisheries revenue in the northeastern U.S. has been from marine calcifiers (in some areas, several species of shellfish, such as sea scallops, comprise over half of the catch of the fisheries). Thus, if ocean acidification affects the early life stages of many marine calcifiers, fisheries in the Northeast may see a profound loss of life, and the local economies will suffer in the process. Representative Farr reiterated this harrowing possibility, stating “there is a huge economic value to figure out the causes and how we combat ocean acidification.”
The consequences of ocean acidification are felt from coast to coast, as demonstrated by the experts’ eyewitness accounts of their findings. However, the challenge remains to make the public aware of the pervasive and profound ramifications that affect more than just the ocean itself. Representative Bonamici echoed this issue at the briefing, stating “ocean health is important not just to people who live in work in coastal communities. It’s important to everybody across the country, and … ocean health is important to a healthy planet as well.”
For photos of the briefing, see our Flickr album here.