Megan, Harmoni, Lucie and Camille Ocean Acidification Megan, Harmoni, Lucie and Camille

What is Ocean Acidification? When carbon dioxide (CO2) is absorbed by seawater, chemical reactions occur that reduce seawater pH, carbonate ion concentration, and saturation states of biologically important calcium carbonate minerals. These chemical reactions are termed "ocean acidification" or "OA" for short. Calcium carbonate minerals are the building blocks for the skeletons and shells of many marine organisms. In areas where most life now congregates in the ocean, the seawater is supersaturated with respect to calcium carbonate minerals. This means there are abundant building blocks for calcifying organisms to build their skeletons and shells. Figure 1: Diagram of Ocean Acidification

Causes of Ocean Acidification Ocean acidification is occurring because too much carbon dioxide is being released  into the atmosphere. The 2 major sources for the influx of atmospheric CO2 are fossil fuel emissions and deforestation. Oceans absorb huge amounts of CO2 each year. This exchange helps to regulate the planet’s atmospheric CO2 concentrations but it also increases the CO2 concentration in the oceans.  When CO2 dissolves into the oceans, it forms carbonic acid, making it more acidic.

Effects of Ocean Acidifications Likely to be the most significant impact of climate change on the Great Barrier Reef Ocean acidification results in chemical changes in the ocean. The pH of the ocean is estimated to decrease to a value of 7.8 from 8.2 (alkaline) by 2100. This is where the name ‘ocean acidification’ came form as the ocean is more acidic.  Ocean acidification has a major affect on marine life and thus connecting food webs. Small increases on the oceans acidity can effect corals and their ability to build skeletons and therefore their ability to form a habitat for reef marine life By affecting the corals, related species that depend on the corals for habitats or protection suffer. Species, such as fish, squid and other gilled marine animals may find it harder to breathing. This is because extracting dissolved oxygen from acidic waters is much more difficult.

Increased concentrations of dissolved carbon dioxide’s impact on coral reefs Because of the increased acid levels in the ocean, corals cannot absorb calcium carbonate needed to maintain their skeletons and stony skeletons that support corals and reefs will dissolve. Furthermore, increased concentrations of dissolved carbon dioxide affects ecosystems in that some organisms will not be able to survive in such conditions. Already, ocean acidification has lowered the pH of the ocean by about 0.11 units, meaning the ocean is about 30% more acidic now than it was in 1751 (according to SCOR 2009). Present day ocean acidification impact on coral reefs: