BIEB 174: Test 1

What is radiative equilibrium?

When incoming radiation is equal to outgoing radiation

What is albedo? When is albedo high? When is it low?

The reflectivity of the Earth's surface. Albedo is high when the earth is very reflective, such as when it is snow-covered. Albedo is low when the earth is not reflective, such as when there's a dark tree covered forest.

Explain the greenhouse effect and why the planet needs it

The greenhouse effect is when gaseous molecules get stuck in the earth's atmosphere and insulate the planet's warmth like a greenhouse. If this phenomenon did not happen or the atmosphere was not there, the earth would be too cold to host life.

What causes atmospheric circulation?

Differential/uneven heating of the earth's surface due to be at different angles from the sun

Name the processes of the hadley cell

At the equator, the air gets warmed by the sun at the intertropical convergence zone and rises. There is high rainfall here because the air is warm and moist. It then cools as it makes its way to the higher latitudes and sinks as cool, dry air. It gains moisture as it travels back to the equator.

Where are the westerlies? What direction do they go in?

Westerlies occur in the mid latitudes. They go FROM the west to the east.

Where are the easterlies/trade winds? What direction do they go in?

Easterlies occur in the poles (high latitudes). Trades occur in lower latitudes. They go FROM the east to the west.

What is the relationship between sea surface height and currents?

Gravity affects sea surface height, gradients caused by this process causes currents.

How does Ekman flux vary SSH in subtropical vs subpolar gures?

High SSH in subtropical, low SSH in subpolar

What direction does Coriolis force deflect in the northern hemisphere?

to the right

What direction does Coriolis force deflect in the southern hemisphere?

to the left

If wind is blowing in a certain direction 0 degrees, at what angle do we expect the surface current to travel from it? What angle do we expect Ekman transport to travel from it?

Sea surface current will travel 45 degrees from the wind. Ekman transport will travel 90 degrees from the wind.

Which direction will Ekman transport go in the northern hemisphere?

To the right

Which direction will Ekman transport go in the southern hemisphere?

to the left

Which direction do we expect geostrophic currents to flow in the northern hemisphere? What mechanism causes it?

Water will flow to the right due to the pressure gradient caused by the Coriolis effect

Do subtropical gyres have upwelling or downwelling? How does this affect temperature, nutrients, and chlorophyll?

Downwelling

Higher temperatures, lower nutrients, lower chlorophyll

Do subpolar gyres have upwelling or downwelling? How does this affect temperature, nutrients, and chlorophyll?

Upwelling

Lower temperatures, higher nutrients, higher chlorophyll

What drives ocean gyres?

Wind

What determines the distributions of Earth's biomes?

Spatial variations in temperature, precipitation, nutrients, light, and other environmental factors

Define features of the biome tropical wet forest

consistently warm, rainy

found largely along the equator and near the ITCZ

Define features of the biome tropical dry forest

consistently warm, seasonally dry

typically have wet summer season and drier winter

Define features of the biome tropical grassland/savannahs

consistently warm, seasonally rainy

tree cover limited by precipitation but also fire

Define features of the biome warm deserts

exceptionally dry

very hot summers, cool in the winter

Define features of the biome temperate forest

seasonally cold and low light, relatively high precipitation

coniferous or deciduous

Define features of the biome boreal forest/taiga

very cold, low light in winters, warmer in summer

generally found in continental interior of the northern hemisphere

List some of the global carbon pools

Most held in rocks on very long timescales
After that, most in oceans as DIC
Then other ones are atmosphere, soils, terrestrial biota, and fossil fuels

List some of the global carbon fluxes

ocean uptake, rivers, volcanoes, burial to sediments, deforestation and land use change, photosynthesis, respiration, and burning of fossil fuels

What is the solubility pump?

Solubility increases with lower temperatures, that cold dense water sinks in the north Atlantic and southern ocean.

Very little water sinks in the north pacific ocean, so water in the deep pacific ocean has been away from the atmosphere for a very long time

What is the relationship between DIC and depth

DIC increases with depth

What is the relationship between DIC and time and why

it is constant because the solubility pump is constant

What does solubility of CO2 depend on?

temperature and salinity. Colder water is more soluble

How does dissolution of CO2 affect the water's pH?

dissolution of CO2 will cause a reaction that will release an H+ ion, so an acid will be created and therefore the water's pH will be lowered and it will become more acidic

What does it mean when the pH is lowered by one?

The H+ concentration has increased by a factor of 10

What happens if high DIC water upwells?

It can lead Co2 to outgass into the atmosphere

What is the Redfield Ratio?

The ratio of different nutrients are required in different proportions. For phytoplankton, it is 106:16:1 for N:P:C

What is remineralization?

Nutrients that were once taken up by phytoplankton are ultimately released back into the water (respiration increases DIC)

Describe how the biological pump works

Organic matter is created at the surface, but sinks due to gravity. As it falls, its broken down mechanically or chemically. As you go further down, less and less material is leftover and it is used by respiration. Most of the organic matter is remineralized and returns the nutrients back into the water. Less than 1% of the organic matter flux from the surface arrives into the deep ocean. This flux increases DIC and nutrients in the deep ocean

Does solubility pump or biological pump add more DIC to deep ocean?

Solubility pump. 90% of deep ocean DIC is because of the solubility pump while 10% is because of the biological pump.

If there was no biological pump, what effect would we see on climate?

We would expect atmospheric CO2 to increase by about 200ppm and the climate would be much warmer

How are anthropogenic carbon emission accumulations divided up by atmosphere, terrestrial, and marine systems?

1/2 atmosphere, 1/4 marine, 1/4 terrestrial

How does the addition of nutrients influence primary production and biomass?

More nutrients means more primary production and more biomass

Major pools of nitrogen

Atmosphere, sedimentary rocks, and the ocean. Smaller ones include soil organics, land biota, and marine biota

Major nitrogen fluxes

Fertilizer, burning of fossil fuels, deposition, N2 fixation, denitrification, nitrification, atmospheric deposition

Why is atmospheric N2 not important for ecosystems?

It is not available to be used as-is, it must be fixed through nitrogen fixation into a bioavailable form

Is N fixation more on land or in the ocean?

They are approximately equal

How has anthropogenic N inputs changed through time?

Historically they were negligible but now they are almost equal to total terrestrial nitrogen fixation

What is denitrification?

Removes nitrogen from the ecosystems back into N2 gas. Anaerobic process facilitated by heterotrophic bacteria. Occurs in low O zones (oxygen minimum zones) and in soils where nitrate and carbon is present

Why is nitrogen important?

It is a key macronutrient required by plants and phytoplankton

Explain the steps in the MARINE nitrogen cycle

atmospheric n2
n fixation into ecosystem and bioavailable as ammonia (NH4)
nitritification into no2- nitrite
nitrification into no3- nitrate

>nitrate can be denitrificated into atmospheric n2
>OR assimilated into phytoplankton then remineralized into ammonia from detritus

Explain the steps in the TERRESTRIAL nitrogen cycle

atmospheric n2
nitrogen fixing bacteria in root nodules
OR n fixation into ecosystem and bioavailable as ammonia (NH4)
nitritification into no2- nitrite
nitrification into no3- nitrate

>nitrate can be denitrificated into atmospheric n2
>OR assimilated into plants
>then remineralized into ammonia by decomposers
> then consumed by animals, who are then remineralized into ammonia by decomposers

What is nitrogen fixation

Atmospheric N2 is converted into bioavailable ammonium

Where can we expect to find nitrogen fixers?

In areas of low nitrogen but high phosphorous, ample light and aerobic conditions

What is the Haber-Bosch process? What is it used for and why is it unique?

Converts N2 to NH3 (not NH4) under higher temperatures and pressure than traditional N fixation. It is used to produce N for fertilizer and is unique because it is a man-made process of artificial fixation

What is nitrogen assimilation?

Takes up nitrogen (and C and P and others) from the environment to make organic matter. N can be a limiting factor. N is assimilated through molecular diffusion.

Why is the assimilation of nutrients limited in phytoplankton?

Cells have limited number of membrane transport proteins due to their size.

What is nitrogen remineralization?

A process that returns fixed nitrogen into ammonium in water/soil from organic matter. Ultimately facilitated by heterotrophic bacteria.

How does nitrogen remineralization change with water temperature?

Faster with warmer water temperature

What is nitrification

A 2 step process where ammonia goes to nitrite and nitrite goes to nitrate. It is aerobic and inhibited by light. It acidifies the soil/water and the reactions and driven by bacteria

where do we expect the highest levels of denitrification?

In anaerobic soils with high nitrate levels

Where do most ammonium levels peak?

At around 50-100m because most decomposition occurs there

What are the expected projections for changes in anthropogenic N inputs?

Fertilizer and agricultural inputs will likely increase but combustion inputs will likely decrease

What are the expected projections for changes in biological N2 fixation?

May increase but by how much is uncertain

What causes oxygen minimum zones?

sinking organic matter, which consumed oxygen (more likely to occur if surface productivity is high and biological matter to depth is strong)

How can burning of fossil fuels lead to forest die-offs?

Burning fossil fuels emits large amounts of nitrogen oxides, which can react with water to create nitric acid. Acid deposition can lower the pH of soil in areas of high depositions well as change soil and water chemistry. Forest die-offs can occur because of the change in soil pH and the addition of a new acid

How can addition of N change plant diversity?

Adding N to plant communities can increase primary productivity but lower species diversity. More N causes plants to grow faster and taller, which can out-shade and out-compete understory plants

What are the major pools of the phosphorous cycle

rocks and sediments; deep ocean have long residence times

terrestrial biota holds more P than the ocean, as there are faster turnover rates

What are the major fluxes of the phosphorous cycle

weathering, recycling, river flux, biological pump, upwelling, fertilizer. burial, remineralization

Why is P important?

Used in the creation of DNA/RNA and for ATP and phospholipid membranes

Why is P difficult to obtain? How is it made bioavailable?

Tightly bound in insoluble compounds. Made bioavailable slowly through weathering processes

What is the most limiting nutrient in terrestrial primary production?

P

What is the most limiting nutrient in marine primary productioin?

Fe

How have humans interfered with the P cycle?

Recently we've seen an increase of P added into fertilizer, so there has been an increase of flux of P in the ocean through runoff due to human activities

Why is the sulfur cycle important in providing stabilizing feedback for climate?

The S cycle is responsible for cloud condensation nuclei and aerosols, and increased CCN can lead to high albedo and cool climate.

Explain how the S cycle works

Aqueous dimethyl sulfate turns into atmospheric dimethyl sulfate, which turns into cloud condensation nuclei

Why is S important

Required for proteins and enzymes (Including nitrogenase)

What are the major pools of the sulfur cycle

rocks, ocean

small amount in the atmosphere

What are the major fluxes of the sulfurcycle

volcanoes, aerosols, acid deposition

How can S acid deposition affect pH in soils?

It can lower it and cause the soil to be more acidic. Can chemically change soil and water and thus ecosystems

Explain how sulfate aerosols can affect albedo

Sulfate aerosols in the atmosphere can accumulate and increase albedo in the atmosphere, potentially leading to cooling effects on climate

Why is iron a necessary nutrient

Needed for photosynthesis, respiration, and N fixation

What is the largest pool of iron? Why is it still scarce?

Continental rocks. It is highly scarce in a bioavailable form and almost doesn't exist on the oceans surface its that rare

Why is Fe so rare in the ocean?

Competition for scavenging, binding with organic ligands, and is taken up by phytoplankton

What is the most important source of Fe in the ocean?

Dust

If most Fe is taken up by phytoplankton, then how is it used by others?

Through recycling of organic matter

What is Liebig's Law of the Minimum?

Production is limited by the factor in least abundance

What's interesting and special about Diazotrophs?

They are a symbiotic N fixing bacteria living in phytoplankton. But they can be found in areas of low nitrogen and are limited by low iron and P

What is an HNLC region and why does it occur?

An HNLC region is an area with high nutrient but low chrlorophyll.

This occurs because even though there is high abundance of nutrients as a whole, there is a severe scarcity of a limiting nutrient

Explain what the Iron fertilization experiments were and what they showed us

Experiments where adding Fe to the ocean increased chlorophyll and changed the community structure to a large cell dominated regime shift. It spurred growth until N and P were consumed as they were the new limiting factors

Shows us that Changes in iron availability throughout earth's history may be linked to large scale changes in climate's state

Explain the difference between a food chain and a food web

A food chain is a group of organisms that are linked together by consumption

A food web is a conjoining of many complex and interwoven food chains

Contrast heterotrophs and autotrophs. How are mixotrophs related?

Autotrophs create organic matter through photosynthesis while heterotrophs derive energy from eating organic matter

Mixotrophs are able to consume organic matter but also photosynthesize

What is a typical trophic efficiency?

About 10%

What does it mean if trophic efficiency is at 20%?

Production by trophic level 1 is 5x greater than trophic level 2. Production by level 2 is 1/5th as much as trophic level 1.

What is consumption efficiency?

The proportion of lower trophic level that is ingested by the next level (ie. half of deer eaten by wolves would be 0.5)

AMOUNT OF PREY BEING EATEN

What is assimilation efficiency?

Proportion of ingested energy that is assimilated into an organism (ie. diffused across the stomach lining)

AMOUNT OF NUTRIENTS FROM PREY BEING ABSORBED

What is production efficiency?

Proportion of assimilated energy that is converted into consumer production (ie. whats left over after basic cost of living that can be used for growth)

AMOUNT OF OF SURPLUS NUTRIENTS FROM PREY BEING ABSORBED THAT CAN BE USED FOR EXTRA PROCESSES SUCH AS GROWTH

What is the trophic efficiency formula

Trophic Efficiency=Consumption Efficiency x Assimilation Efficiency x Production Efficiency

What is top-down control

Higher trophic levels control structure of lower trophic levels (ex. predators present, reduced herbivores, more plants; predators absent, herbivores abundant, less plants)

What is bottom-up control

Environmental conditions and primary producers control ecosystem structure (ex. plant defenses to protect against herbivores limit how much the herbivores can eat; harmful algal blooms produce toxins that can be harmful to all other organisms)

Why is consumption efficiency low for ecosystems with woody plants

Large fraction of biomass is not eaten by herbivores

Why are aquatic primary producers more rich in N and P than terrestrial plants? Why does this increase their trophic efficiency?

Aquatic primary producers dont need to build tall carbon structures to compete for light, so they can save that N and P.

heterotrophs need that N and P, so they are a better food source than plants are and they have a higher grazing pressure on them