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Figure 1. Annual anomalies of global average land-surface air temperature (Jones et al., 2001).
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 effect on most ocean life, there are some 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 enough to counteract the rise in sea level (Harley, 2006). The loss of these ice sheets is also expected to contribute to global warming, as it would lower the albedo of the earth, causing less solar radiation to be reflected back out into space (IPCC, 2001).
Climate change has the potential to cause significant changes in water chemistry, especially with regards to oxygen solubility. As seawater warms, its ability to dissolve gases decreases dramatically. One of these gases is oxygen, which of course essential to most living things for respiration (Harley, 2006). Geological records from past global warming events has shown evidence of severe, large-scale hypoxic episodes (Bralower, 2002). A significant drop in dissolved oxygen levels would detrimentally influence species worldwide. Another critical area of seawater chemistry that will likely be affected by global warming is the carbonate buffering system. The ocean have an enormous capacity to take up carbon dioxide. However, as atmospheric carbon dioxide levels rise, the equilibrium of the carbonate-bicarbonate-carbonic acid cycle will be increasingly shifted toward the acidic side of the equation, lowering the pH of the water (Harley, 2006). Ocean acidification would have detrimental effects on sea life, especially important calcareous primary producers, such as coccolithophores.
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Another of the most visible effects of climate change is coral bleaching. When hermatypic corals are stressed by high water temperatures or other effects, they expel their symbiotic zooxanthelle from their tissues. This process deprives corals of the color, as well as of their primary source of nutrition. If corals are without their symbionts for too long they can perish from starvation. The impact of coral death then spreads through the reef ecosystem. Secondary effects are most obvious in fish, especially among those that feed specifically on corals, such as butterfly fish. Studies have indicated that such fish were gradually starving to death and that their decline in numbers resulted from a failure to breed in the months and years following the destruction of their reef. As it stands today, more than 30% of coral reefs throughout the world are already severely degraded and up to 60% of corals may be lost by 2030 due to temperature induced bleaching (ARC, 2007). Coral reefs are also threatened by the sea level risFor example, when slow growing corals cannot grow quickly enough to counteract the rise in sea level, reefs can fall below the depths at which photosynthesis can occur and perish (Harley, 2006).
It is also likely that climate change will have severe, direct effects on humans. Thermal expansion of seawater alone is expected to cause a rise of between 0.09 and 0.37 meters over the next century (IPCC, 2001). This modest sounding rise is nevertheless enough to threaten many coastal cities and in some cases entire island nations. It is also predicted that storms, such as monsoons and hurricanes, may increase in number and intensity as a result of global warming (IPCC, 2001). Global warming can affect land-based agriculture in certain areas by changing patterns of precipitation. For example, desertification is a major threat in areas such as the southwestern United States, while excessive flooding is the threat in other regions (IPCC 2001). Increased carbon dioxide levels will also alter the growth rates of crops and weeds. In certain environments, changes in the productivity of traditional, land agriculture could lead to a changes in fish demand.
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