the consequences of spreading of ‘Dead Zones’ on marine ecosystem

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. That is way these areas are called dead zones. Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. One of the largest dead zones forms in the Gulf of Mexico every spring. Hypoxic zones can occur naturally but climate change, nutrients run-off from the land, and eutrophication are leading to algal bloom and causing further depletion of oxygen level in water. As a result dead zones are spreading at much faster pace. 

Consequences of spreading of Dead Zones on Marine Ecosystem 

•The reduced dissolved oxygen in ocean water results in loss of marine life thus the habitats which were once teeming with life are transformed into biological deserts. 

•Elevated nutrient levels and algal blooms can also cause problems in drinking water in communities nearby and upstream from dead zones. The released toxins are also detrimental to the survival of marine life. 

•By depriving organisms of sunlight and oxygen, algal blooms negatively impact a variety of species that live below the water’s surface. The number and diversity of benthic, or bottom-dwelling, species are especially reduced. 

•When fast moving marine species flee from the dead zones and occupy a new habitat, they cause overcrowding of their new habitats and affect the ecosystem services over there. 

•Several reproductive problems emanate when the oxygen level depletes, such as, lower egg count and less spawning. 

•Algal blooms can also lead to the death of shore birds that rely on the marine ecosystem for food. With fewer fish beneath algal blooms, these animals lose an important food source. 

•With the loss of marine biodiversity in these areas, the economic stability of the local communities also takes a hit.