Lecture 15/16 - Gases, Particles & Trace Elements Flashcards
What is the concentration of oxygen in the
- ) Surface ocean?
- ) Deep ocean?
Maximum at surface from mixing and abundant by photosynthesis
Minimum at depth (oxygen minimum). The intensity of this depends on amount of organic matter being respired, as no photosynthesis takes place.
How is oxygen distributed within the ocean
1) Its solubility at the relevant T & P
2) Biological processes which control production and consumption
3) Physical processes which control rate of input and circulation - mixing
What is the OMZ?
Oxygen Minimum Zone - regions of the global ocean that present low dissolved oxygen concentrations at depths. due to a reduced ventilation and high respiration rates of the settling organic matter produced in the surface waters.
Why is the Oxygen Minimum Zone important?
An important sink for fixed nitrogen, contributing 30-50% of the oceanic nitrogen removal, mainly through the process of denitrification.
What controls the carbon dioxide and carbonate chemistry of seawater?
Carbon dioxide resides from both the atmosphere and carbonate sediments. It can also react within the water column through biological and chemical processes. CO2 is on the increase, this can cause acidification of areas of the ocean.
How does the CO2 content vary through the oceans?
This can be through the amount of primary production from certain species of phytoplankton. CO2 can also be deposited in certain regions more so than areas of fast moving currents.
What is the CCD?
Carbonate Compensation Depth – depth at which rate of carbonate solution = or exceeds rate of supply
What might happen over time if CO2 in the atmosphere increases?
In the long term many regions could result with high levels of Ocean Acidification.
What are the impacts of Ocean Acidification?
Once dissolved in seawater CO2 can form into carbonic acid.As carbonate ion gets depleted, seawater becomes undersaturated with calcium carbonate minerals vital for shell-building.
Calcifying organisms will be increasingly limited in their ability to deposit hard parts – a disaster to the biological carbon pump.
What are several different forms of biological debris?
Phytoplankton, Zooplankton
Faecal matter
Shell debris
Fish and waste products
Apart from CaCO3 what other particles are there in the ocean?
Suspended, biological, airborne and cosmic particulates. These can be both organic and inorganic.
What controls the distribution of particles in the ocean?
Horizontal and vertical distribution is controlled by relative rates of supply and removal
Where can Manganese be found?
Black smokers at mid ocean ridges have high Mn content.
How might a black/white smoker plume behave on the ocean bed?
Hot water, less dense, rise to a neutrally buoyant position, moved around by bottom currents, impacted by topography of the seafloor
What happens to particulates in anoxic waters?
Minor elements like Fe and Mn are more soluble in reducing conditions and are in particulate form in oxidising conditions e.g. Black Sea
