Model Question and Answers for APSC | What are the consequences of the spreading ‘Dead Zones’ on marine ecosystems?

Ans : Dead zones are low-oxygen or hypoxic areas in the world’s oceans and lakes. Because most organisms need oxygen to live, few organisms can survive in hypoxic conditions.
Formation:
1. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels.
2.Enhanced primary production results in an accumulation of particulate organic matter, which encourages microbial activity and the consumption of dissolved oxygen in bottom waters.
The consequences of the spreading ‘Dead Zones’ on marine ecosystems
1. The reduced dissolved oxygen in ocean water results in loss of marine life
2. Toxic algal blooms release toxins that can poison fish, molluscs and marine mammals like dolphins
3. The reproductive problems emanate when the oxygen level depletes
4.Slow-moving bottom-dwelling creatures like clams, lobsters and oysters are unable to escape the dead zone and face extinction
5. When fast-moving marine species flee from the dead zones and occupy a new habitat, they
cause overcrowding of their new habitats
Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. Dead zones have now been reported from more than 400 systems, affecting a total area of more than 245,000 square kilometres, and are probably a key stressor on marine ecosystems.