Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
Page 8
Page 9
Page 10
Page 11
Page 12
Page 13
Page 14
Page 15
Page 16
These animals depend on combining calcium Ca which is abundant in seawater with carbonate CO3 - to make calcite calcium carbonate CaCO3 the hard crys- talline material that makes up their shells. Increasing the CO2 in seawater leaves less carbonate for sea creatures to combine with calcium to make shells. The hydrogen ions produced in the chemical equation result in lower pH but its really the theft of that carbonate molecule by the hydrogen atoms that causes the problem for shell-making organisms. See Figure 1. In the last century humans have increased the con- centration of CO2 in the atmosphere by about 44. The concentration of CO2 in the atmosphere has not been this high in the last 800000 years. The same is true for ocean acidity. The rate of change in acidity may be greater now than at any time in the last 300 million years. How is changing the pH of the oceans relevant to humans We wouldnt know or feel the dierence in seawater of pH 8.2 and 8.1 or even 6.0 because our skeletons arent in contact with seawater unlike shellsh which experience the change in acidity in their bones. The real concern for humans is how ocean acidi- cation will aect the marine ecosystems we rely on. Worldwide sheries supply 15 of the animal protein consumed by humans provide employment for 200 mil- lion people and contribute 230 billion to the global economy. Fish and sheries are a big deal for both our economy and our dinner tables. A recent study by United Nation experts estimated that by 2100 ocean acidication will cost the global economy over a trillion dollars.1 This gure only reects the potential economic loss linked to coral reefs which are considered to be the most vulnerable species to ocean acidication. Coral reefs provide diverse ecosystem ser- vices such as shoreline protection food services for mil- lions of people tourism revenue for many countries and raw materials for a diverse array of other industries such as the pharmaceutical industry. If coral reefs dissolve humans across the globe will feel the impact. Science is ramping up fast to test marine animals abil- ity to cope with increasing acidity. Dierent species have dierent resiliencies to acidication that are still poorly understood. Most studies show that juvenile shellsh are especially vulnerable showing higher mortality in more acidic water. Mark Green a marine scientist from Saint Josephs College in Maine has been researching the eects of ocean acidication on juvenile soft shell clams for over a decade. His research shows that juvenile clam growth begins to be compromised at a pH of 7.8 and that below 6.8 clam spat and baby clams simply dissolve.2 However results can be variable. One study showed that the shell mass of several crustaceans including lob- sters actually increased with acidity. But the net eect CO2 INCREASES CO2 Dissolved carbon dioxide H2 O Water H2 CO3 Carbonic acid HCO3 - Bicarbonate ion Bicarbonate ion HCO3 - Hydrogen ion H Carbonate ion CO3 2- Figure 1. CO2 enters the ocean at a predefined rate depending on how much CO2 is in the atmosphere and the temperature of the water. When CO2 enters the ocean it reacts with water to form a weak acid carbonic acid. Since the acid is weak it easily breaks down into bicarbonate and hydrogen ions. The increase of hydrogen ions decreases the amount of available carbonate ions which shellfish need to construct their shells. 1 Secretariat of the Convention on Biological Diversity. 2014. An Updated Synthesis of the Impacts of Ocean Acidification on Marine Biodiversity. Available online at httpwww.cbd.intdocpublicationscbd-ts-75-en.pdf 2 Green M. et al. 2009. Death by dissolution Sediment saturation state as a mortality factor for juvenile bivalves. Limnology and Oceanography. 10371047 pp. Available online httpwww.aslo.orglotocvol_54issue_41037.pdf 8 MANOMET PARTNERSHIPS WINTER 2014