Marine Atlas: Maximizing Benefits for Solomon Islands

TURNING SOUR: OCEAN ACIDITY CO 2 emissions are not only causing the temperature and level Solomon Islands’ waters to rise, but also its acidity, which causes serious problems for many marine organisms.

Seawater acidity can be measured using the pH, a numeric scale to specify the acidity or basicity of a solution; a pH of 7 is neutral—neither acidic nor basic. A decrease in pH by one means a solution is twice as acidic, whereas an increase by one means a solution twice as basic (see graphic). The pH of the global oceans ranges from around 7.5 to 8.4. Solomon Islands’ waters are at the higher end of this range, with pH between 8.23 and 8.31. Increasing CO 2 in the surface water leads to increased acidification (lower pH). Already, CO 2 emissions have resulted in a

26 per cent increase in the acid content in the ocean (see small map).

How does acidification affect calcite levels? Firstly, CO 2 in the water transforms into carbonic acid and the carbonate satura- tion decreases. This is problematic for all animals that use carbonate to make their shells, such as mussels, snails, corals and sea urchins, among many others (see also chapter “Travellers or homebodies”). The less carbonate there is in the water, the more difficult it is for them to make suit- able shells. The effects can already be seen among foraminifera: tiny calcifying creatures that make up an important part of the plank- ton. The shell-thickness of animals in the

In this context, it is important to look at calcite, which is another vital element found in seawater (see map), as calcium carbonate is a building block of the skeletons of most marine organisms, including corals. Globally, calcite concentrations are highest in the high latitudes and in coastal areas. The calcite concentrations in Solomon Islands’ oce- anic waters are low, with the coastal areas around the islands having a higher concen- tration (see calcite map).

pH

8.41

Ocean acidification Solomon Islands is suffering the effects of global warming, with greenhouse gas emissions not only heating the nation’s sea, but also ending up in it. In fact, worldwide the oceans have absorbed about one third of the carbon dioxide (CO 2 ) produced by human ac- tivities since 1800 and about half of the

8.23

Solomon Islands Provisional EEZ Boundary

5°S

CO 2 produced by burning fossil fuels (Sabine et al., 2004). As CO 2 in the ocean increases, ocean pH decreases, resulting in the water becoming more acidic. This is called ocean acidifica- tion, the “evil twin” of sea temperature and sea level rise, described in the previous maps.

50

100

200 km

Copyright © MACBIO Map produced by GRID-Arendal Sources : Becker et al, 2009; Claus et al, 2016; Smith and Sandwell 1997; Tyberghein et al, 2011.

10°S

15°S

160°E

155°E

165°E

170°E

CLIMATE CHANGE THREATS MAXIMIZING BENEFITS FOR SOLOMON ISLANDS

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