Increased sea surface temperature impact to coral reef ecosystem, its implication to fisheries.
A greater understanding of on-going changes in climate regime can help people take necessary steps to successfully adapt and survive. This article explores the consequences of one of the notable manifestations of climate change, i. e., increased sea surface temperature (SST) due to trapped greenhouse gases in the atmosphere.
The superfluous emission of greenhouse gases, particularly carbon dioxide into the atmosphere, has become a global cause of concern in the past few decades. The accumulated greenhouse gases lead to an overall increase in average global temperature (Meehl et al. 2007). As a result, the ability of the global system to maintain a dynamic equilibrium appears to be compromised as indicated by notable climate changes which are believed to be exacerbated by extant human activities.
How can increased sea surface temperature influence the lives of people dependent on the productivity of the coastal areas? Here are studies that reveal the significance of this global phenomenon.
Impact of Increased SST
Increased SST can have significant impacts on marine life especially in the tropics. These include primarily the corals, fishes, and species composition in the marine ecosystem.
The effect of increased SST presents problems on marine food web productivity and sustainability, especially to vulnerable locations and ecosystems. These effects include the direct effect of SST to coral reefs specifically in terms of mass bleaching events that lead to consequential obliteration of biological processes founded on the productivity of healthy reef ecosystems.
Considering that marine organisms are closely interconnected and interrelated, the damage accorded by increased SST will have significant implications to the dynamics of the entire food web, which, as studies indicate, have more negative than positive impacts to reef life and society in general due to decreased fish productivity.
Bleaching of Coral Reefs
Wilkinson (2004) reported that coral reef bleaching due to increased sea temperatures lead to the destruction of reefs around the world. Reef bleaching results when the symbiotic zooxanthellae vital to coral reef metabolism is expelled from the body of the coral. Lack of photosynthetic activity in the coral will eventually lead to coral death if high temperature is sustained in the long-term.
As a result of damage to reefs as a consequence of bleaching, there will be a significant reduction in the diversity and abundance of reef fishes (Wilson et al. 2008, Coker et al. 2009, Munday et al. 2009, Pratchett et al. 2009, Wilson et al. 2010) especially in vulnerable locations such as those with structurally less complex systems (Graham et al. 2006). Up to 75% of fish species may decline in abundance within a 5-10 year period including species which are not coral reef dependent (Munday 2008a).
Reduced Fish Growth
Munday et al. (2008b) demonstrated in an experiment on a common coral-reef fish (Acanthochromis polyacanthus) that at an elevated temperature of 31 degrees Centigrade, growth of fish with low food supply and with high food supply is the same. This means that temperature can restrict growth in fish. On a larger scale, this means that increased sea surface temperature can reduce the amount of biomass present in reef ecosystems, which will mean reduced fish productivity. This also means less food available for people dependent on what the coastal ecosystem yields.
Source: Ofer Ben-Tzvi@Palawaniana.net
Reduced Availability of Nutrients
Another interesting finding is that increase in SST makes sea waters more stable, hence, this prevents the important process of vertical mixing of large bodies of water that make available nutrients from the ocean bottom to the surface. This means that the upper surface of the sea will have less nutrients to start up the marine food chain. Reduced nutrient supply will mean less organic material available to initiate primary production which lies at the base of food chains supporting fisheries (Munday 2009).
Resiliency of Coral Reef Ecosystems
Many coral reef ecosystems are resilient to short-term increase in SST. Resiliency depends on many factors including reef complexity; marine species biodiversity; presence of exacerbating, human-induced factors; mobility of marine organisms, among others.
One of the foremost consideration of the SST problem lies on sustained, elevated sea temperature regimes that can exceed the tolerance level of coral reefs ecosystems especially in the tropics, thus possibly result to irreversible direct damage to coral reefs and overall imbalance in reef ecosystem that may threaten the livelihood and very existence of people who largely depend on the goods and services it provides. Ultimately, man as the end-of-pipe recipient of such effect, will bear the brunt of the consequences.
Applying the Precautionary Approach
Taking the precautionary approach stance in dealing with the global threat of climate change, certain pro-active adaptation options may be adopted to reduce, if not eliminate, the negative consequences of increased sea surface temperature to coastal, fishery-based societies. There is a need to generate adaptive options that will cushion the effects of climate change.
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