User:Aeking104/sandbox

Implications of OMZ on climate change and Ocean health. (loss of N, OMZs expanding or becoming more permanent/ formation of dead zones ⇒ eutrophication, fisheries).

While OMZs can occur naturally, they can be exacerbated by human impacts like climate change and land-based pollution from agriculture and sewage. The prediction of current climate models is substantial warming and loss of oxygen throughout the majority of the upper ocean .Global warming increases ocean temperatures, especially in shallow coastal areas, and when water temperature increases, its ability to hold oxygen decreases, leading to oxygen concentrations going down in the water. Nutrients found in both agricultural runoff and sewage can contribute to excessive primary production, creating a bloom, that introduces large quantities of organic carbon which accumulates on the seafloor. This organic carbon is then broken down through respiration, using up the available oxygen in the water.

Open ocean areas with no oxygen have grown more than 1.7 million square miles in the last 50 years, and coastal waters have seen a tenfold increase in low-oxygen areas in the same time. Consequences of even a small decrease in oxygen levels can hinder reproduction, growth, and can lead to disease and death in marine animals. If there is enough decrease of oxygen in the water, it could become unlivable for the majority of the organisms living there, resulting in what are commonly called dead zones.

Short term effects can be seen in acutely fatal circumstances, but other sublethal consequences can include impaired reproductive ability, reduced growth, and increase in diseased population. These can be attributed to the co-stressor effect. When an organism is already stressed, for example getting less oxygen than it would prefer, it doesn’t do as well in other areas of its existence like reproduction, growth, and warding off disease. Additionally, warmer water not only holds less oxygen, but it also causes marine organisms to have higher metabolic rates, resulting in them using up available oxygen more quickly, lowering the oxygen concentration in the water even more and compounding the effects seen. Finally, for some organisms, habitat reduction will be a problem. Habitable zones in the water column are expected to compress and habitable seasons are expected to be shortened. If the water an organism's regular habitat sits in has oxygen concentrations lower than it can tolerate, it won’t want to live there anymore. This leads to changed migration patterns as well as changed or reduced habitat area.

Long term effects can be seen on a broader scale of changes in biodiversity and food web makeup. Due to habitat change of many organisms, predator-prey relationships will be altered. For example, when squeezed into a smaller well-oxygenated area, predator-prey encounter rates will increase, causing an increase in predation, potentially putting strain on the prey population. Additionally, diversity of ecosystems in general is expected to decrease due to decrease in oxygen concentrations.