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The melting of glacial ice and the thermal expansion of ocean water will cause sea levels to rise in future years. While this is unlikely to have a great global effect on most ocean life, there are some local cases cases where the change might be too fast for certain ecosystems to adapt. This could be a particular problem with coral reefs, which might not be able to grow fast In particular, coral reefs are very sensitive to increases in seawater temperatures. Also, when slow growing corals cannot grow quickly enough to counteract the rise in sea level, reefs can fall below the photic zone and perish (Harley, 2006).
The change in temperature will cause changes in water chemistry, which in turn may have drastic effects on certain species, especially those with low tolerances. Many life processes in animals and plants are dependent on temperature, and could be significantly altered by a rise of Many biological processes are temperature dependent and could be adversely affected by even a few degrees in of temperature change (Harley, 2006). Higher temperature waters, such as those in the tropics have less primary production in the form of phytoplankton, which almost all fish derive their energy from. Addition of fresh water from melting ice caps decreases the salinity of surface salinities in ocean regions, which can be detrimental to species with low tolerances to changes in salinity (Harley, 2006). Significant freshwater input in high latitude regions can also stifle downwelling and stop global thermohaline circulation, radically altering global climate and current patterns.
Projected surface temperature changes by 2099. ("Climate Change 2001: The Scientific Basis," 2001)
Climate change has the potential to cause changes in water chemistry, especially with regards to oxygen solubility and the carbonate buffering cycles. Such changes may have drastic effects on certain species. As seawater warms, it also loses its ability to dissolve certain gases. the solubility of most gases in it decrease. One of these gases is O2oxygen, which is essential to all animals for respiration (Harley, 2006). Geological records of from past global warming events show has shown evidence of severe periods of anoxia on large to global scales , large-scale hypoxic episodes (Bralower, 2002). A significant, eustatic drop in the dissolved oxygen levels of O2 would result in result in a decrease of metabolism of animal life. CO2, however, is not near its saturation levels in the ocean. As CO2 levels rise, it will be taken in by the ocean where it reacts to form Carbonic acid, thus lowering the pH of the water would detrimentally influence species worldwide. On the other hand, deep waters are generally not saturated in carbon dioxide. The ocean thus has an enormous capacity as a carbon dioxide sink. However, as atmospheric carbon dioxide levels rise, the equilibrium of the carbonate-bicarbonate-carbonic acid cycle will be shifted towards increasing water acidity (Harley, 2006). Acidic conditions could Ocean acidification would have detrimental effects on sea life, especially those that depend on significant amount of CaC03including important calcareous primary producers, such as shellfishcoccolithophores.
The introduction of fresh water from melting ice caps can also affect deep-water thermo-haline currents. Because it lowers the density of water in polar region, it can prevent the sinking of water here, thus weakening or stopping the overturn of the ocean. A current location where some models predict such an event occurring is in the north Atlantic with the shutdown of the Ocean conveyor (Gagosian, 2007). Historically this has resulted in severe cases that cause a build up of toxins in the ocean, which is linked to mass-extinction events (Bralower, 2002). It is also possible that a similar event could prevent the transport of water from the tropics to the poles, causing a period of rapid climate change.
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