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Sea levels are rising as a result of climate change, but that’s not all that happening in the oceans. The ocean plays a major role in the carbon cycle, storing 93% of the carbon on earth. So when we unbalance the carbon cycle we stress both terrestrial and marine ecosystems.
The ocean is separated into two layers: surface ocean, and deep ocean. The surface of the ocean is warmer and floats, while the deep areas are cooler and dense. The deep ocean holds most of the nutrients (they sink) and most of the CO2, since CO2 is more soluble at colder temperatures.
As the atmosphere, and thus the seas warm up, some of the CO2 stored in the deep ocean will separate out of the water. The higher temperatures having reduced the solubility of CO2. It’s likely that in the future the oceans will be a CO2 source, not a CO2 sink.
Marine nutrients will also be affected. Some scientists have argue that since sea organisms need CO2, increased levels of atmospheric carbon will increase their growth. However CO2 isn’t a growth-limiting nutrient. There isn’t won’t be enough iron, nitrogen or phosphate for them to grow at a faster rate.
We’re not positive yet whether climate change is going to affect the supply of those nutrients positively or negatively. On the one hand, most of them are in the deep ocean: The more the surface ocean heats up, the bigger the temperature difference between the surface and deep ocean, and the less mixing between the two will occur. Mixing is how marine organisms get those sunken nutrients back into play.
Of course, another climate change prediction says that we will have more storms in the future. Storms can do significant ecosystem damage, but they also help mix the surface and deep ocean, and reduce stratification. The scientific debate on this issue is ongoing.
The final, and most depressing aspect of the marine ecosystem is a direct result of elevated CO2 levels, not climate change. So even climate sceptics should be worried about this! In the oceans there’s currently balance between CO2 and CO3–.
25% of the CO2 humans emit enters the oceans, and that pushes the balance towards CO2 and away from CO3– , making the oceans more acidic.
The main problem with this is that CaCO3 is used to make a lot of the shells, scales and skeletons of marine organisms. With decreased amounts of CO3– available, organisms that use CO3– in their bodies will be put under increasing stress.
Coral especially will suffer and become less competitive, but so will molluscs and pteropods (a type of planktonic snail).
No one wants to lose the beauty that the oceans offer us, but can we act in time to prevent the damage already being done?
This article was also published on Chronicles of Everything