Lec 27 (Nutrient cycle part 2)

Question 1

Nutrients and Organisms… talk about them.

Answer 1

Organisms can modify the distribution and
cycling of nutrients in ecosystems.

Although same ecological processes occur in
terrestrial and aquatic habitats, there are
consistent differences

Question 2

Aquatics vs Terrestrial when it comes to organisms and nutrients

Answer 2

Aquatic systems tend to have greater proportion
of autotrophs consumed by herbivores compared
to terrestrial system, where autotrophs consumed
by detritivores

Question 3

Even if aquatic and terrestrial NPP are the same…?

Answer 3

Aquatic tends to have…

lower autotroph biomass

more herbivore and herbivory

Fewer detritivores, detritus, and decomposers

than terrestrial systems

Question 4

Aquatic life has less autotroph biomass (less detritus) and more herbivore (less detritus) which results in?

Answer 4

Overall quicker cycling of nutrients

Question 5

Terrestrial life has more autotroph biomass (More detritus) and fewer herbivores (More detritus)

Answer 5

Overall slower cycling of nutrients

Question 6

Streams and vertebrate move nutrients across systems are examples of?

Answer 6

Aquatic nutrient cycling

Question 7

Water in streams

moves…..

Answer 7

As a result, nutrient cycling doesn’t occur in

a single stationary location, leading to nutrient spiraling

Question 8

Spiraling Length?

Nutrient Retentiveness?

Answer 8

The length of stream required for
an atom of a nutrient to complete a cycle from
release into the water column to re-entry into the
benthic environment

The inverse of spiraling
length, or the tendency of a stream to retain
nutrients.

Question 9

Longer spiraling length?

Short spiraling length?

Answer 9

Longer spiraling length = low nutrient retentiveness

Short spiraling length = high nutrient retentiveness

Question 10

Where spiralling lengths are short, a particular nutrient atom may be used only once before it is washed out of a stream system.

True or False

Answer 10

False… a particular nutrient atom may be used MANY times before it is washed out of a stream system.

Question 11

If there is a photo of a lake or stream with red and purple lines… What does the red line indicate? What about the purple line?

Answer 11

Red = short spiraling
length, long nutrient
retentiveness (nutrients
stay close to where they
started)

Purple = long spiraling
length, short nutrient
retentiveness (nutrients
moved further from where
they started)

Question 12

How does nutrient cycling work in streams?

Answer 12

Nutrients move up the food web, then down as organisms decompose, all the while being pushed forever downstream!

Question 13

_______ only contain 10% of the retained aquatic nitrogen but consumes a large
proportion of available nitrogen.

Answer 13

Macroinvertebrates

Question 14

-What all contributes to nitrogen retention in creeks and streams?

Answer 14

Increase in biomass combined with rapid flux of nitrogen between consumers and primary producers contribute to nitrogen retention.

Question 15

High abundances of macroinvertebrates can?

Answer 15

speed up the nutrient cycling in streams

Faster nutrient cycling = Greater primary production

Question 16

Nutrient Cycling in Aquatic Ecosystems:

Vertebrate move nutrients across systems… What’s an example?

Answer 16

• Salmon migration from ocean → freshwater to spawn
• Transfer huge amounts of
  nutrients (e.g. nitrogen) from the
  ocean to forest ecosystems

Question 17

Nutrient Cycling in Terrestrial Ecosystems:

Grasslands… What’s an example?

Answer 17

Pocket Gophers can…
• Increased light penetration to high nitrogen soil

• Bring up nitrogen rich soil to the
surface, where soil is usually poor in nitrogen

Question 18

Why are grasses growing on prairie dog colonies containing more nitrogen?

Answer 18

Gophers burrow/build mounds which increase heterogeneity in soil nitrogen and light penetration.

Question 19

What effect do large grazers have on nutrient availability in terrestrial ecosystems?

Answer 19

• Large grazers, like deer, may increase primary productivity of ecosystem through increased rates of nutrient cycling.
• On top of this nutrient cycling shift, heavy grazing shifts composition of plants (east more palatable species, leaving behind seedlings of less palatable species!)

Question 20

Without large grazers…?

Answer 20

nutrient cycling occurs more slowly
(by decomposition and feeding of
small grazers)

Question 21

How have humans messed up the nitrogen cycle?

Answer 21

We have converted massive amounts of nitrogen from

the atmosphere reservoir to terrestrial reservoirs through the use of fertilizers.

Question 22

Haber Process?

Answer 22

artificial nitrogen fixation. Combines N gas and H gas using a metal catalyst under high heat and pressure to form NH3

Question 23

Nitrogen fixation by humans has now exceeded non-human nitrogen fixation.

True or False

Answer 23

True

Question 24

-What are some consequences for the effect of human on the nitrogen cycle? (too much nitrogen)

Answer 24

Acid rain (NOx)

Methemoglobinemia (“Blue baby syndrome”)

Shift from grasslands to forests

Question 25

-What is Acid rain (NOx) and Methemoglobinemia (“Blue baby syndrome”)?

Answer 25

Acid rain (NOx): Nitrogen oxides, produced by internal
combustion engines, when combined with water vapor
form acid (= why cars have catalytic converters)

Methemoglobinemia (“Blue baby syndrome”): nitrates in drinking water (usually from agricultural runoff) can cause hemoglobin in blood to oxidize, reducing its capacity to carry O2

Question 26

-Why is there a shift from grasslands to forests?

Answer 26

• Increases in nitrogen (from both combustion engines and agriculture runoff) allows trees to competitively exclude many grasses

• Increased N deposition across the prairies is causing
expansion of forests into areas historically covered by prairie habitats.

Question 27

History of atmospheric composition of CO2 has been

recreated by studying?

Answer 27

studying air bubbles that get trapped in ice. Ice cores allows estimates going back 160,000 years.

Question 28

-When we see population size increase we usually see?

Answer 28

-Forest areas increase due to nitrogen increase (grasslands was an exception… might be due to a limited effect by humans)

Question 29

-What were the findings from air bubbles

in Vostok ice core?

Answer 29

CO2 oscillated between 190 – 280

ppm (parts per million) over past 160,000 years.

Question 30

Temperature has change has directly mirrored CO2 change.

True or False

Answer 30

True

Question 31

-What trends/patterns have we seen human impact have on the carbon cycle?

Answer 31

Atmospheric CO2 Over The Past 1,000 years shows rapid increase in starting in 1800s (Industrial revolution)

Atmospheric CO2 concentrations were 413 ppm in April 2019 – an unprecedented 100 ppm increase.

*300ppm highest CO2 level ever recorded in previous 160,000 yrs

Question 32

-How are humans causing this effect on the carbon cycle?

Answer 32

Industrial activities…

Human industrial activities center on burning fossil fuels
→ combustion reaction that releases CO2

Question 33

What are some past interruptions of global economic activity (and fossil fuel burning) related deviations fromCO2
increase.

Answer 33

WW1 and WW2

Great depression

Corona Virus most likely

Question 34

What are the three human Influence on Carbon Cycles

Takeaways…

Answer 34

1. CO2 in the atmosphere has varied widely during the last 160,000 years and closely parallels global temperature. High CO2 → high temperatures.
2. Atmospheric CO2 has increased substantially in the past two centuries, exceeding all levels reached during the past 160,000 years.
3. Present levels of CO2 in the atmosphere are strongly
   influenced by the burning of fossil fuels (i.e. activities of us humans).

Question 35

How does deforestation affect nitrogen levels?

Answer 35

Clear cutting causes more nitrogen to be tied up in the soil. (Soil erosion)

Question 36

What is a way to combat forest cutting such as forest fires or logging?

Answer 36

Work by Turner and colleagues (2003) has shown that young, rapidly growing understory vegetation can act as a NUTRIENT SINK after a disturbance such as
logging or forest fire.

Question 37

How does flooding effect nutrient cycles?

Answer 37

-This effects Phosphorus Movement
• Inputs (inputting phosphorus into the stream)
– Geological (weathering of rocks causes the release of phosphorous into the water)
– Meteorological (precipitation into the stream)

• Exports (export of phosphorus out of the stream)
– Geological (phosphorous dissolved into the stream)

Question 38

-When is most phosphorus lost? Gained?

Answer 38

Lost: During storms and spring (melting of snow)

Gain: During fall/autumn when leaves are falling