Protecting Ocean Ecosystems
The mud in Casco Bay, Maine, is changing. According to an article last fall in the Bangor Daily News, areas that used to contain vast quantities of economically valuable clams are now “dead mud.” Local clammers are finding that sites of former abundance are now completely devoid of shellfish. Even efforts to seed the formerly thriving areas with shellfish larvae are not yielding results. Some scientists think that the increasing acidity of the mud, due partly to the increased carbon dioxide being absorbed from the atmosphere, is making conditions unsuitable for shellfish larvae to form, well, shells. Shellfish need to pull calcium carbonate out of the water to grow. As ocean water becomes more acidic from carbon pollution, the calcium carbonate it contains becomes unavailable to shellfish and other organisms. It essentially gets tied up “buffering” the more acidic oceans. For an excellent “Ocean Acidification 101” course, see this video by NOAA. Here are the basics on what they call “Osteoporosis of the Sea”:
- Increasing CO2 in the atmosphere = increasing CO2 in the oceans. The world’s oceans have absorbed about 1/3 of the CO2 that humans have released into the atmosphere in the past couple of centuries.
- CO2 in the ocean forms carbonic acid. Thus, “Ocean Acidification.”
- The acidity is corrosive, beyond what marine life is adapted to, and not only dissolves the calcium carbonate shells of existing organisms, but prevents new ones from growing.
- The surface of the ocean is 0.1 pH units lower than it was prior to the Industrial Revolution and recent studies suggest that the ocean pH will drop another 0.3 to 0.4 pH units by the end of the century, which is 100 to 150 percent more acidic than it is now.
Atmospheric carbon is not the only reason shellfish populations are struggling. River water is generally more acidic than ocean water. As New England precipitation increases in response to climate change, rivers increasingly empty acidic plumes into our bays and estuaries,and further lower the pH of these ecologically sensitive areas. And, according to a recent study at the University of New Hampshire, the rivers are contributing this extra acid burden just at the time larval shellfish are trying to grow their shells. This, as they put it, “is not good news for the Gulf of Maine’s $450-million-per-year shellfish industry.”
To worsen the odds of this shell game, the relentless flow of nutrient pollution from our watersheds into the ocean is taking a toll on coastal ecosystems, including shellfisheries. Excess nutrients, especially nitrogen, can cause algae to bloom excessively where it otherwise wouldn’t. When algae dies and decomposes it releases more carbon dioxide into the water, which further increases the acidity.
There is some uncertainty about how all of these factors will collectively affect ocean ecosystems. But there is an enormous amount of ongoing research on the topic. Scientists are sure the oceans are getting more acidic, and there is no doubt that we are dumping unprecedented levels of nutrient pollution into our coastal waters. Disappearing shellfish beds and failures in shellfish propagation are but some of the negative consequences we are increasingly experiencing in New England.
Other effects of OA will likely cascade through our ocean ecosystems. For example, pteropods, a tiny shell-forming planktonic mollusk, are a vital food source for many of our economically and culturally important animals including herring, mackerel, and right whales. Pteropods are very vulnerable to OA – they dissolve in lower pH conditions. If this happens on a large scale many of our important ocean going animals may have a harder time finding food. For an interesting project about the imperiled pteropods, check out this upcoming art show by fine artist Cornelia Kubler Kavanagh. Kavanagh has collaborated with Woods Hole Oceanographic Institute pteropod researcher Gareth Lawson to create amazing, over-sized sculptures of the tiny pteropods as part of an effort to raise awareness of their plight.
We may not yet be able to quantify the damage OA will cause in New England waters – although researchers are trying. But we don’t want to sit on our hands and wait to see how bad it will get. We can work hard to prevent further harm, to protect our special places, to give our abundant ocean life a chance to thrive.
So, that’s what CLF is doing. We are working to stop the nutrient pollution that is choking out life in our coastal ecosystems. We are helping to restore New England’s estuaries. We are promoting clean energy and reductions in greenhouse gas emissions to help stop the acidification of our oceans and other negative effects of climate change. And we support our National Ocean Policy and regional ocean planning, which call for immediate steps to protect critical marine habitats, ensure a sustainable future for our fishing industry and coastal communities, reduce coastal pollution and promote the responsible development of offshore renewable energy.