Ocean deoxygenation Flashcards
(17 cards)
What is ocean deoxygenation?
The reduction of oxygen levels in ocean waters
Ocean deoxygenation can lead to hypoxic conditions that negatively impact marine life.
How do temperature and atmospheric pressure affect the solubility of gases in seawater?
Oxygen solubility is higher in cold water and increases with pressure at depth
However, surface waters can be supersaturated with oxygen due to photosynthesis and turbulence.
Where is oxygen produced in the ocean?
By marine plants and microbes in the surface layer
This production occurs primarily in the top 200m where light is available.
What processes consume oxygen in ocean waters?
Respiration and organic matter decomposition
These processes occur throughout the water column.
What is the oxygen minimum zone (OMZ)?
A region in the ocean where oxygen concentrations are particularly low
OMZs can exist in all ocean basins and cover about 8% of the global ocean.
What are the oxygen concentration classifications for ocean waters?
Oxygen deficient: [O2] < 6 mg/l, Hypoxic: [O2] < 2 mg/l, Anoxic: [O2] < 0.5 mg/l
These classifications indicate the severity of oxygen depletion.
What causes dead zones in the ocean?
When the supply of oxygen from the surface is less than its utilization in deep water
This phenomenon can be exacerbated by increased stratification and temperature.
What are upwelling systems?
Regions where ocean currents and winds bring nutrient-rich but oxygen-poor water to the surface
These areas are important for commercial fishing.
What is the Southern Benguela Upwelling System (SBUS)?
A highly productive region that supports valuable commercial fisheries and is prone to seasonal hypoxic events
The SBUS relies heavily on regenerated nutrients from microbial respiration.
What are the predicted changes in ocean oxygen levels by 2100?
A decline of 1-7% in oxygen levels
This is due to warming, reduced solubility, and decreased ventilation of the deep ocean.
What is the ARGO program?
A program that monitors ocean conditions with floats reporting temperature, salinity, and pressure
Some floats are now equipped with sensors for oxygen and other parameters.
How does ocean deoxygenation impact marine species?
It favors hypoxia-tolerant species and affects fish populations, especially larger species
This can have significant implications for marine ecosystems.
Fill in the blank: Oxygen is produced in the ocean by _______.
[marine plants and microbes]
True or False: Most ocean water is oxic with oxygen levels greater than 6 mg/l.
True
What is the relationship between temperature, salinity, and oxygen solubility?
As temperature and salinity increase, the solubility of oxygen decreases
This can lead to reduced oxygen availability in warmer waters.
What is the significance of the oxygen depth profile in the ocean?
It varies by layer: surface layer produces O2, middle layer consumes O2, and bottom layer has less O2 consumption
This profile indicates the distribution of oxygen in ocean waters.
What happens in stagnant waters regarding oxygen levels?
Oxidative decomposition can exhaust O2, leading to anoxic conditions
This is common in restricted basins like the Black Sea.
