Recent years have seen a sharp rise in concern about ocean “dead zones”. These areas are defined as areas of low-oxygen water in the ocean, where levels are too low for marine animals to survive. The prevalence of dead zones has increased in recent decades and not only appeared in the ocean, but also extended to lakes.
In a study new published on June 2 in the journal Science Advances, a team of researchers revealed that dead zones have occurred frequently over the past 1.2 million years. Their appearance coincided with hypnotic events common in the geological record, those that occurred during warm icy periods, such as those we live in today. Read also How did the Earth’s ice ages happen? .. Scientists find the answer in the depths of the ocean WMO Ocean Warning A new discovery paves the way for the commercial use of marine algae to produce sustainable biofuels Threatens to poison marine life.. The first global assessment of the catastrophic spread of marine algae
Ice Age and Dead Zones
An international team of researchers, from various American universities and a Japanese university, has analyzed a core of ancient sediment drilled from the bottom of the Bering Sea in the North Pacific Ocean, and has been able to identify 27 separate instances of dead zones – officially called ‘dead zones’. Oxygen minimums (OMZs) – which have evolved over the past 1.2 million years.
As the notes, study UC Santa Cruz recurrent episodes of hypoxia were arguably a regular feature of the Pacific Ocean through the Pleistocene years.
The end of the last ice age (about 12 thousand years ago) witnessed a widespread decrease in oxygen levels in the North Pacific, some of which lasted for a thousand years, while others lasted for about 40 thousand years. The warming events at that time caused the melting of the ice sheet, which led to the supply of the ocean with huge amounts of fresh water.
Algae and dead zones
The areas of hypoxia are caused by harmful algal blooms, which are microscopic organisms that eventually decompose and sink to the sea floor and consume this oxygen in the water.
The study showed that rising sea levels, which occur during a warm icy climate, contributed to hypoxic events and thus increased the likelihood of dead zones appearing.
As sea level rises, dissolved iron can be transported from flooded continental shelves to the open ocean, which in turn promotes intense phytoplankton growth in surface waters.
Global warming and dead zones
The researchers expect that oxygen levels will continue to decline in the global ocean over the next millennium, which means more dead zones in the oceans.
Here, it can be said that environmental pollution is a major factor in this problem, as human-caused waste (especially agricultural fertilizers) flows into the ocean and waterways, and acts as a nutrient source, attracting an abundance of marine algae that consumes oxygen and suffocates marine animals over thousands of years every year. Once.
The researchers were unable to determine the extent of the spread of the dead zones in the Pacific Ocean, but they are certain that they are many and spread over large areas.
Finally, we must raise awareness about the extent to which climate change affects the biological balance on the planet, including water bodies, especially as it affects the formation of a “tipping point” in the oceans in terms of sudden and severe oxygen deficiency that would destroy systems environment, food sources, and thus the economy.