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Question 1

In a majority of ecosystem, what nutrients are most likely to be limiting?

Answer 1

Nitrogen and phosphorus

Question 2

!!!!!!How to figure out what nutrient is limiting?

Question 3

??Solve limiting nutrient problems

Question 4

Phosphorus cycle?

Answer 4

Phosphorus is present in rocks, and then dominated by internal cycling. Some is absorbed to freshwater sedimented and soils. It is a slow cycle with no atmospheric component.

Question 5

Why is phosphorus often limiting?

Answer 5

•Organisms are far better at detecting and taking up P from water than our instruments and even standard water purification methods can.
•Highest demand:supply ratio, and lowest concentration of major elements
•Chlorophyll (measure of algal primary productivity) increases with P.

Question 6

Colimitation?

Answer 6

Limitation of both essential nutrients, even if one is more limiting than another. This is because if biomass increase, and the less limiting nutrient becomes limiting.

Question 7

What is more abundance in newer soils, N or P?

Answer 7

Phosphorus

Question 8

Rhizobia?

Answer 8

The bacteria responsible for nutrient fixation.

Question 9

What is the primary source of nitrogen in ecosystems?

Answer 9

Decomposition from other organisms (internal cycling)

Question 10

Is all phosphorus recycled in an ecosystem?

Answer 10

Overtime, phosphorus is being used by the organisms that are not recycled, and it is lost, either by leaching or is occluded (process of chemical complexing of phosphorus to aluminum or iron, which isn’t available to plants).

Question 11

Occluded?

Answer 11

A substance that was once biologically available becomes non biologically available.

Question 12

???Why are older islands more likely to be P-limited while younger islands are N-limited?

Question 13

Ratios (N:P) if only N concentration added changes, what happens to green algae dominant and N fixing Cyanobacteria?

Answer 13

14:1 N:P ratio can allow green algae to dominance, but a 5:1 N:P ratio will not for green algae, but N fixing Cyanobacteria will dominate.

Question 14

How can phytoplankton reduce oxygen levels?

Answer 14

When they die, other organisms will need to consume them, thus using oxygen. Additionally at night, there is a lower oxygen concentration of oxygen due to photosynthesis being off and oxygen used for respiration. So if both occur together, then lakes will be oxygen deficient.

Question 15

!!!!!Why don’t N-fixing bacteria fix N until it doesn’t become limiting?

Answer 15

•Fixing nitrogen is costly due to its triple bond and high bond enthalpies.