The Southern Ocean receives about 70% of the global oceanic pollution by the external nitrogen despite it’s covering only 30% of the global ocean area.
The reactive nitrogen ( NOx, NHy, and dissolved organic nitrogen) input to the open ocean has increased significantly since 1860, especially in the last two decades, and it’s deposition to the global ocean is expected to rise significantly owing to human activities.
Such consistent increase in the reactive nitrogen input could lead to changes in the ocean nitrogen and carbon cycles apart from affecting the marine biological productivity.
Nitrogen is harmful to all forms of life just like carbon and is the worst pollutant in the world affecting the oceans because it causes harmful algal blooms, eutrophication and oceans hypoxia.
Algal blooms deplete dissolved oxygen, causing marine wildlife to suffer and become more vulnerable to toxins and disease.
As a result, it makes marine life more vulnerable to disease, reduces biodiversity, degrades ocean ecosystems and contributes to global warming.
Anthropogenic nitrogen released by human activities such as industrial nitrogen fixation and combustion of fossil fuel has contributed the most towards this increase.
During the 1990s to the 2010s, a study found that external nitrogen in the Pacific, Indian, and Atlantic sectors grew at the rate of 24 , 42 , and 0.02 Tg-N per year, respectively, and that for the entire Southern Ocean grew at the rate of 67 Tg-N per year.
The Southern Ocean covers approximately 30% of the global ocean surface area, and it is an important pathway that drives external influences such as anthropogenic impact into the global ocean interior owing to the strong movement of water masses.
Much of the sea surface water flowing into the Southern Ocean touches the borders of several industrial countries such as China, India, and South-East Asian countries. This makes the Southern Ocean to receive about 70% of the global oceanic input of external nitrogen despite it’s covering only one-third of the global ocean area, the study says, and which emphasizes the important role of the Southern Ocean in integrating anthropogenic impacts in the global ocean.