Hypoxia is killing the oceans!

Although vast, the ocean is not infinite, so it is not immune to human influence, and the reasons for declining numbers of marine species are varied!

by Mónica Barbosa 08 JAN. 2019

There are many causes of fish kill, but oxygen depletion is the most common cause.

Alarmingly, a dangerous transformation is underway in the oceans of the planet. However, these reasons may be identified as a result of the convergence of a number of factors, such as overfishing or pollution.

That is, all actions result in consequences! For example, the flow of nitrogenous nutrients, synthetic fertilizers (and animal waste) from cultivated soils into streams has profoundly altered coastal ecosystems.

In the same way as fertilizers used in the soil, increase the productivity of agricultural activities, their presence in the water stimulates the development of toxic forms of phytoplankton, which proliferate rapidly, leading to the so-called eutrophication.

At the same time, at the end of their life cycle, when they die, the algae are deposited on the seabed, where they decompose. During this process, they consume oxygen, reducing their quantity in the water, contributing to the so-called zones of hypoxia, commonly known as "dead areas".

Results of ongoing monitoring since the 1960s have found that the polluting activity has degraded the quality of sea water in such a way that the number of hypoxic zones has doubled every 10 years, and approximately 250 million km² of oceanic area - predominantly densely populated coasts such as the Baltic and Black Seas, East China Sea and Gulf of Mexico.

Research published earlier this month by Oceanography magazine, as a result of the monitoring of O₂ concentrations in rivers in North Caroline, demonstrated the effective impact of human activity on the flow regime of watercourses.

That is, in densely urbanized areas, "barriers" such as the waterproofing created either by the communication channels or by the rainwater pipes, dams and other human alterations, imply determinant erosion processes, reducing the flow, and leading to increased stagnation of water.

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