Climate change’s hidden damage

looks at the damage caused to underwater life by global warming

Leonardo DiCaprio recently spoke of the threat of global climate change as part of his Oscar acceptance speech. In December of last year, the COP21 Climate Change Summit in Paris agreed to limit global temperature to less than a 2°C rise above levels of the pre-industrial era. Although there are still skeptics, it appears global acknowledgement and a cultural shift towards addressing climate change is a reality.

Image: Scyrene

Image: Scyrene

We know that each year massive amounts of carbon dioxide are released into the atmosphere through anthropogenic sources. Cars, energy production and manufacturing all produce large amounts of the compound.If you were to look into your carbon footprint, it is likely to be over 10 tonnes per year; this is equivalent to 24 million balloons. We are most familiar with the terrestrial effects: summer heat waves, warm winters and even more rain.

However, much less is known about the impact on aquatic ecosystems. This is because they are harder to access for research.Carbon saturation of marine ecosystems is a significant problem, due to increased atmospheric carbon dioxide from pre-industrial levels of carbon, although plastic pollutants and melting sea ice are much more high profile marine issues. In an effort to sustain chemical equilibrium, more carbon dioxide is absorbed into water. This results in decreased pH, commonly reported as ocean acidification, and saturation state of carbonate minerals. Ocean acidification presents a major threat to marine organisms.

Calcifiers such as oysters, crabs and corals rely on a delicate balance of carbon minerals in order to survive. Acidification results in their delicate shells dissolving, entirely destroying coral reefs and making shelled animals vulnerable. An imbalance of minerals means they cannot rebuild their shells after shedding, a necessary process for growth or after damage.

Corals are animals. They are classifed as marine invertebrates of phylum Cnidaria, related to jellyfish and sea anemones. Coral reefs are regarded as one of the most vulnerable marine organisms. Their architecture is reliant on organisms that shed their carbonate shells. Corals can only thrive through a process of accretion. Small carbonate particles accumulate to form corals, attracted by gravity to the larger existing structure.

Nature reports that in this century coral reefs are projected to shift from a state of net accretion to one of net dissolution. However new findings suggest this may happen much sooner. Determining the contribution of acidification as the source of dissolution is difficult as other factors such as temperature, pollution, and careless tourism play a role in the health of these precious ecosystems.

Australian scientists have conducted the first seawater chemistry manipulation of a natural coral reef community. The One Tree Reef community was treated with alkaline solutes, which worked to restore ocean chemistry closer to pre-industrial conditions.
They found that net community calcification increased, indicating that ocean acidification may already be impairing coral reef growth.

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