The incessant and reckless burning of fossil fuels, land clearing, agriculture, and other human activities are some of the prominent causes resulting in the increase of greenhouse gases such as methane and carbon dioxide. This, in turn, is increasing the temperature of the Earth’s atmosphere and the oceans. This phenomenon of temperature rise has been termed as ‘Global Warming’. Scientists of the Intergovernmental Panel on Climate have made a prediction regarding the average global climate and are fearful that by the end of this century, the average temperature may rise between 1.4°C and 5°C.
One of the most vulnerable ecosystems in peril because of the threats imposed by global warming is the marine ecosystem. The marine ecosystem is the aquatic ecosystem with water having high salt content. They constitute the largest aquatic ecosystem of Earth. The physical nature of oceans has started changing because of global warming and this is having severe impacts on the entire marine ecosystem.
Phytoplankton, which forms the basis of marine food chains, is a unicellular plant that lives on the ocean’s surface. Just like algae, these planktons also use photosynthesis for nutrients and can only survive in cooler regions. The temperature rising because of global warming is destroying the plankton’s favorable habitat, disturbing the entire marine ecosystem eventually. Similarly, the algae, too, is on the verge of extinction because of global warming.
As the oceans are becoming warmer and less dense, the oxygen-rich surface water is getting separated from the nutrient-rich deeper water. This, as a result, is preventing the vertical mixing of ocean water and thereby preventing the traveling of oxygen and nutrients in the water. As the oceans become warmer, the ideal water temperature for the living condition of several species will change, thereby, forcing them to migrate in search for the situations appropriate for their survival. Fishes living in the North Sea have moved further towards the northern direction or into the deeper waters because of the rising temperature.
One of the most drastic effects of global warming can be seen on the coral reefs. Due to the excessive rise of temperature of the water, corals tend to expel the organisms living within their structure. These organisms are known as zooxanthellae and as the corals lose them they turn completely white, which even results in their death.
Global warming also poses a threat to the climatic conditions in the form of extreme and unpredictable weather conditions. Tropical storms and excessive rainfall causes physical damage to coral reefs, and other coastal ecosystems and communities. Huge damage was done to the corals of St. John coast, a part of US Virgin Island, by the hurricanes named Hugo and Marilyn that had hit the coast in 1989 and 1995 respectively.
The rising temperature also affects the metabolism, reproduction, life cycle, and behavior of organisms living in the marine ecosystem, thereby, affecting the sex ratio of species and threatening their population.
One of the serious impacts of global warming is the melting of glacier and polar ice, and thermal expansion of warmer water because of which the global sea level may rise as much as 69cm in the upcoming century. This, in turn, will pose a survival threat to mangrove ecosystem that requires stable sea levels to survive for a long time.
Carbon dioxide, released because of various human activities, gets dissolved in the water making it acidic and reducing its oxygen carrying capacity. This proves fatal for the gilled marine organisms like fishes, squids, and other organisms like crabs, lobsters, shellfish and corals.
The United Nations Environment Programme (UNEP) aims at protecting oceans and seas and promoting environment-friendly use of marine resources. It has established the Global Programme of Action for the Protection of the Marine Environment from Land-based Activities, which is the only global intergovernmental mechanism for direct addressing of the relationship between terrestrial, freshwater, coastal and marine ecosystems.