Introduction
Human activities, and more so, burning of fossil fuel has greatly contributed to increase in a number of greenhouse gasses in the atmosphere which has consequently raised world temperature. Compared to the 1880s, today’s world temperature has substantially risen, increasing by 1 degree Celsius. Moreover, following the current rate of industrialization and emission of carbon and other greenhouse gasses to the atmosphere, world temperatures are set to rise by between 2.6 and 4.8 degrees above pre-industrial levels by the year 2100 (Johnson, 2016). Such a high and unprecedented level of temperature could easily spell doom for planet Earth. Other than the increase in world temperature, other direct consequences of emission of these greenhouse gasses to the environment include melting of glaciers which end up raising the sea level, acidifying oceans, change of regional weather patterns and change of nutrient loads and alteration of ocean circulation. Given the indispensable roles played by oceans regarding its planetary functions such as cycling of carbon, nitrogen, and other key elements plus its provision of human nourishment, this paper is going to assess the consequences or effects of global warming particularly rise of sea temperature on the ocean and marine life.
Carbon Concentration and the Rise in Global Temperature
The increase in global temperature is directly linked to increasing in the emission of greenhouse gasses especially carbon. The increase of temperature on the earth’s surface is as a result of ‘greenhouse’ effect brought about by the ever-increasing greenhouse gasses such as carbon dioxide, methane gas among other gasses. Since 1979, the global ocean surface temperature has been increasing at the rate of 0.13°C per decade which has seen the global ocean interior temperature rising by >0.1°C since 1961. This increase in ocean temperature has contributed to the currently experienced increase in wind speed and storm occurrences, alterations in ocean circulation and nutrient loads plus the rise in sea level (more than 15 cm in the last 100 years). Higher ocean temperature has also changed oceanic evaporation rate hence changing the precipitation pattern which today stands at an average of approximately 3.3 mm per year (Brierley & Kingsford, 2009).
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Similarly, this high concentration of CO2 in the atmosphere will lead to increase in carbonic acid as carbon dioxide in the atmosphere dissolves in the ocean as the ocean tries to maintain equilibrium between CO2 in the atmosphere and ocean. In the last 200 years, the ocean PH has reduced by 0.1 due to a 30% upsurge in hydrogen ion concentration. This change in ocean temperature and PH brought by the increase in carbon in the air causes unprecedented physical changes within the ocean greatly impacting the marine life. If CO2’ s concentration passes its critical threshold of 450 ppm, causing an increase of 2°C global temperatures above pre-industrial values then the subsequent effects of this increase will be catastrophic and irreversible. At the present rate of emission of carbon into the atmosphere, this threshold might be passed by 2040.
Impact of Rising Sea Temperature on Marine Ecosystem
At the height of global warming, sea temperature from the surface to depths of about 2300 feet have been changed. Most of marine life thrives within this depths and research has shown that marine ecosystem is quite sensitive even to the slightest of temperature change. Some of the consequences of the rise in temperature of sea water include coral reef bleaching, the rise in sea level, altered lifestyles, decreased mixing and change of PH of ocean water.
Coral Bleaching
One impact of an increase in sea temperature is coral reef bleaching. Coral reef bleaching is a stress response brought about by high water temperatures. Just like all marine organisms, the evolution of coral reefs over the years has happened within a very small temperature range. However, with the varied increase of sea water temperature in different areas, those areas whose temperature has risen beyond the limit tolerable by coral reefs have reported cases of coral reef bleaching. The higher than tolerable water temperature stresses the reefs, leading them to expel the algae that thrive inside their tissues resulting into their bleaching something which if prolonged, lead to the death or the organisms (Great Barrier Reef Marine Park Authority, 2016). In the recent time's episodes of coral bleaching around the world has been experienced with a mortality rate of the organism reaching 70% in some areas.
Coral reefs contain the most varied ecosystem on the planet providing shelter and habitat for many marine organisms. As such, the extinction of coral reefs poses a big danger to types of organisms which are limited in variety. Such a reduction in biodiversity through extermination of species inexorably contributes to the interruption in ecology health and purpose, reducing natural resources. Crucial services that we rely on such as recycling and sanitization of air and water, the formation of soil and removal of contaminants from the ecosystem are all hampered with. Apart from these, the coral reefs also play an important role in carbon and nitrogen fixation in the water, recycling nutrients and protecting the coastlines from the effect of tropical storms and wave action.
Change of Weather Patterns and Stormy Weather
With the increase in sea temperature, weather patterns are also changed. Notably, increase in sea temperature has been associated with unpredictable and extreme weather conditions. Strong tropical storms and heavier rainfall have the ability of physically damaging coral reefs and other coastal ecosystems. Also as the sea temperatures increase, the location of ideal water temperatures for several species also changes something which causes the animals to move homes. For instance, fish in the North Sea have changed their homes, moving further north or into the deeper water due to the rising sea temperatures. For other species, this rise in temperature could cause them lose their homes completely, for example, the polar bears, penguins, and seals who are faced by receding sea ice due to global warming.
Change in Sea Level
On average, since 1880, the world’s ocean and sea level have been rising at the rate of six-tenths of an inch every decade. However, the last few years has seen an increase of this rate to approximately an inch per year (US Environmental Protection Agency, 2016). This rise in sea level has been as a result of thermal expansion of warmer water, melting of polar ice and glaciers. This rise in sea water affects the marine ecosystem in several ways. One example is that the rise in sea level reduces the amount of light that reaches algae and other off show plants affecting the photosynthesis process and alters nutrient flux. Also, rise in sea level leads to floods of coastal habitat affecting organisms that live there, influencing diversity and speciation (Peters, 2008). Ecosystems such as the mangrove which depend on stable sea level for survival could be at risk of distinction due to the rise of sea level.
Altering of Life Styles
The rise in sea temperature has a direct impact on the rate of metabolism, life cycle and the behavior of marine ecosystem. For many species, change in sea temperature provides the signal for breeding and reproduction. From the current rise in temperature, the organisms could be tricked into starting to reproduce before the right time affecting the breeding process. Examples of marine animals whose breeding and the number of male and female offspring depend on temperature are the sea turtle, fish, and copepods. For these animals, the change in sea temperature could play an important role in changing the sex ratio of their offspring causing a skewed relationship between males and females hence threaten population survival.
Acidification of the Ocean
Oceans play an important role in absorbing CO2 from the atmosphere hence reducing greenhouse effect which consequently leads to global warming. Carbon dioxide from the atmosphere is absorbed in oceans in an effort to maintain equilibrium between the two biospheres. By dissolving in water carbon dioxide forms carbonic acid lowering the PH of the ocean. Higher acidity levels affect the availability of minerals in the water, hampering the ability of certain animals to build their shells and exoskeletons. At the time, the higher acidity level may cause the shells or protective skeletons to fall off.
On this aspect, the rising sea temperature brings about some reprieve. The rate of carbon dioxide absorption is usually subject to temperature and strength of the wind. As such, colder waters are more prone to acidification since it absorbs more carbon dioxide than warm water. From this, the rise of sea temperatures counteracts the acidification of sea water, however, this is insufficient to provide a long-term solution to the lack of absorption of CO2 means more CO2 in the atmosphere hence increase of world temperature which could affect the ecosystem in different other ways.
Conclusion
Rise in sea temperatures negatively impacts marine life affecting marine biological processes, its diversity and quite frankly threaten human food security. In several cases, the rate of change within the marine ecosystem is highly unprecedented and if we cannot find ways of reducing the amount of CO2 in the atmosphere, the only hope of sustaining the ecosystem is resistance and resilience species of the organisms. The only challenge with this is organisms and ecosystems are highly variable and adapted differently to cope with the challenge of rising sea temperatures. References
Brierley, A & Kingsford, M (2009). Impacts of Climate Change on Marine Organisms and Ecosystems. Current Biology : 19(14), 602-614.
Great Barrier Reef Marine Park Authority (2016). Impacts of rising sea temperatures on the Reef. Retrieved from http://www.gbrmpa.gov.au/managing-the-reef/threats-to-the-reef/climate-change/how-climate-change-can-affect-the-reef/rising-sea-temperatures
Johnson, I (2016) .Climate change may be escalating so fast it could be 'game over', scientists warn. Independent . Retrieved from http://www.independent.co.uk/news/science/climate-change-game-over-global-warming-climate-sensitivity-seven-degrees-a7407881.html
Peter, S (2008). Environmental determinants of extinction selectivity in the fossil record. Nature : 454(58), 626-632.
US Environmental Protection Agency (2016). Climate Change Indicators: Oceans. Retrieved from https://www.epa.gov/climate-indicators/oceans
