Quiz 8

Question 1

What is biogeochemistry?

Answer 1

The cycling of biologically important elements between living (biotic) and non-living (abiotic) components of an ecosystem

Question 2

What are the 2 approaches for studying nutrient dynamics?

Answer 2

Nutrient budgets

Nutrient cycles

Question 3

How do we study nutrient dynamics using nutrient budgets? (4)

Answer 3

We study the nutrient inputs to and nutrient outputs from the ecosystem

If inputs > outputs = storage increasing
If inputs < outputs = storage decreasing
Inputs = outputs = steady state

Question 4

How do we study nutrient dynamics using nutrient cycles? (2)

Answer 4

Cycles are just pools and fluxes of nutrients

Think of pools as “tanks” that nutrients transfer between (“fluxes”)

Question 5

What are the 4 basic analytical fractions of phosphorus in natural waters?

Answer 5

Soluble reactive phosphorus (SRP)
Soluble unreactive phosphorus (SUP)
Total phosphorus (TP)
Particulate phosphorus (PP)

Question 6

What type of filter is used to differentiate between soluble and particulate phosphorus?

Answer 6

A 0.45u membrane filter

Question 7

What is total phosphorus? (3)

Answer 7

Total phosphorus = Particulate phosphorus PP (organic and inorganic) + Total dissolved phosphorus TDP (organic and inorganic)

TP is not very useful as it contains bits and pieces of particulate matter that are not bioavailable to algae

However, it is the most often analyzed and used

Question 8

Which lake nutrients have a gaseous cycle? (3)

Answer 8

Unlike carbon, nitrogen, and oxygen, phosphorus does not have a gaseous cycle and so it will never leave the lake via diffusion

This is problematic as you can have huge loading issues with phosphorus

But nitrogen has a large gaseous phase, so there is lots of cycling occurring outside of the lake and there can be significant losses to the atmosphere

Question 9

What is total dissolved phosphorus (TDP)? (4)

Answer 9

The phosphorus fraction filtered through

TDP = SRP + SUP

TDP is a better indicator of lake productivity and nutrient limitation than TP

TDP still contains a fraction that is not readily bioavailable (eg. Long chain polyphosphates, DNA/RNA, phospholipids), but can still be used if you don’t have SRP (reactive) data

Question 10

What is particulate phosphorus? (4)

Answer 10

The fraction of TP that does not pass through the filter

It includes all material, inorganic and organic, particulate and colloidal, that was captured on the filter

Contains bacteria, algae, detritus, clays, plant material etc.

Not bioavailable to algae

Question 11

What is soluble unreactive phosphorus? (5)

Answer 11

Part of what was filtered, but only the organic part)

Is the difference between TDP and SRP

It is not indicative of lake productivity as most of it is not bioavailable

Compounds in this fraction are organic forms of DNA/RNA, phospholipids etc.

Also contains forms of filterable phosphorus that do not react to the SRP test

Question 12

What is soluble reactive phosphorus? (4)

Answer 12

Part of what was filtered, but only the inorganic part

Consists largely of the inorganic orthophosphate (PO4-3) form of phosphorus

It is 100% bioavailable, is preferred by algae, and is the best indicator of nutrient limitation

Used to give an accurate index of phosphorus available and algal growth

Question 13

What is APA? (3)

Answer 13

Extracellular alkaline phosphatase enzyme activity (APA) is important for algae to acquire phosphorus in freshwater ecosystems that are P-limited

Therefore, it is often used as an indicator of P deficiency

APA helps algae access organic P but the regulation of APA in response to the availability of inorganic and organic P is poorly understood

Question 14

What is total nitrogen? (4)

Answer 14

TN = NO2-N + NO3-N + NH3-N + organic N (particulate and dissolved)

Similar to TP, TN is not very useful as it contains bits and pieces of particulate matter that are not bioavailable to algae

Most TN is not bioavailable in the short term

Same as P, soluble and particulate N are differentiated by whether or not they pass through a 0.45u membrane filter

Question 15

What is TKN? (3)

Answer 15

TKN stands for Total Kjeldahl Nitrogen

TKN = NH3-N + organic nitrogen (dissolved and particulate)

It is used in civil/environmental engineering (eg. Sewage treatment), but we don’t really use it

Question 16

What is DIN? (4)

Answer 16

Dissolved inorganic nitrogen

DIN = NO2-N + NO3-N + NH3-H (all inorganic and dissolved)

It is 100% bioavailable, NH3 is the fraction that is preferred by algae

It is the best indicator of nutrient limitation for N and constitutes an index for the amount of nitrogen immediately available for algae growth

Question 17

What are the best indicators of nutrient limitation for P and N? (3)

Answer 17

N:P ratios are best approximated by DIN/SRP

For P = SRP (soluble reactive phosphorus)

For N = DIN (dissolved inorganic nitrogen)

Question 18

What are the nutrients in lakes? (4)

Answer 18

An element essential for an organisms growth, survival, and reproduction

Macronutrients include: phosphorus, carbon, hydrogen, nitrogen, oxygen, sulphur, calcium, and silicon

Micro nutrients include: manganese, iron, molybdenum, and others (rarely limited in lakes but can happen (eg. Lake Okanagan)

P and N are the primary limiting macronutrients in freshwater

Question 19

What are the 4 nutrient assessment techniques?

Answer 19

Bioassays to determine nutrient limitation

Synoptic surveys of biota

Low-level water chemistry analysis

Qualitative assessment

Question 20

When is P limiting in lakes and reservoirs? (3)

Answer 20

P is limiting when SRP < 1ug/L and/or TDP < 2-3ug/L

Algae are extremely efficient at extracting P from water

Some small algae have growth rates as high as ~0.7 ug/L, which allows them to extract more P than large algae due to a high surface area to volume ratio

Question 21

When is N limiting in lakes and reservoirs, and streams? (3)

Answer 21

N is limiting in lakes and reservoirs when DIN < 30ug/L

N is limiting in streams when DIN < 20ug/L

The threshold for N limitation is lower in rivers because the flowing water and turbulence increases the nutrient concentration over an area

Question 22

Nitrogen and silicon limitation

Answer 22

Both can vary seasonally and spatially

It is possible to shift from P limited to N limited

Si is critical for diatoms to form shells, so if Si is limiting (SiO2 < 0.5mg/L) the food web might be severely affected

Question 23

When does blue green algae appear?

Answer 23

When N becomes limiting and P loading is very high, there is a high risk of Cyanobacteria

Question 24

How do Cyanobacteria obtain nitrogen if N is limiting?

Answer 24

They can obtain N from the air via nitrogen fixation, which will usually cross a major threshold for the lake

Question 25

Blue-green algae (5)

Answer 25

Also called Cyanobacteria Nutritionally deficient (don’t give back to the ecosystem) Often toxic Highly undesirable Extremely energetic, so they take 16ATP to fix nitrogen

Question 26

Reaction for biological nitrogen fixation by blue green algae (4)

Answer 26

N2 + 8H+ + 8e- + 16ATP ==> 2NH3 + H2 + 16ADP + 16Pi Two moles of ammonia are produced from one mole of nitrogen gas at the expense of 16 moles of ATP and a supply of electrons and protons (hydrogen ions) The reaction is performed by prokaryotic bacteria using an enzyme complex termed nitrogenase Nitrogen fixation occurs in specialized cells in Cyanobacteria called Heterocysts

Question 27

Cyanobacterial toxins (4)

Answer 27

Toxins are the naturally produced poisons stored in the cells of certain species of Cyanobacteria They fall into two categories: hepatotoxins (attack the liver) and neurotoxins (attack the nervous system), others just simply irritate the skin Toxins are usually released into the water when the cells rupture and die microcystin-LR is now classified as a carcinogen by Health Canada

Question 28

Hepatotoxins in Cyanobacteria (4)

Answer 28

They are produced by various species within the genera including Microcystis, Anabaena, Oscillatoria, Nodularia etc. Although all can be lethal, not all strains are lethal So far scientists have found about 50 kinds of microcystins One of them is Microcystin-LR

Question 29

Microcystins and Microcystin-LR (3)

Answer 29

Microcystins are well established as potent liver toxins to humans and other mammals They have been classified as possible carcinogens in humans by Health Canada Most research has focused on Microcystin-LR because it is the more common

Question 30

Hepatotoxins vs neurotoxins

Answer 30

Hepatotoxins are more focused on by scientists because neurotoxins aren’t as common or widespread in water supplies

Question 31

Redfield Ratio (4)

Answer 31

The Redfield Ratio is the cellular atomic weight ratio of Carbon, Nitrogen, and Phosphorus in marine phytoplankton C:N:P For every 1 unit of phosphorus, there should be 16 units of nitrogen, and 106 units of carbon 106C:16N:1P If this balance is thrown off and P is relatively higher than N, Cyanobacteria begin fixing from the atmosphere However, there is a middle transition zone (from ~10:1 to 20:1) where both or either may be limited

Question 32

When do blue green algae begin fixing nitrogen from the atmosphere?

Answer 32

When the N:P ratio is low (low nitrogen, high phosphorus)

Question 33

The normal situation in the ocean for the Redfield Ratio

Answer 33

106CO2 + 16NO3- + 1HPO42- is photosynthesized (or alternatively respired) to transform C106 H263 O110 N16 P1 + 138O2

Question 34

What is the “next best” for approximating N:P ratios if you cannot use SRP?

Answer 34

DIN (for N) and TDP (for P)

Question 35

Why are N:P ratios using TN/TP useless?

Answer 35

Because these don’t show how much of the fractions are dissolved and therefore we don’t know how much is limiting, which is the whole point of the Redfield ratio in the first place

Question 36

How can we tell an N and P limitation using the Redfield Ratio? (3)

Answer 36

N:P < 10:1 = N limitation N:P > 20:1 = P limitation N:P between 10:1 and 20:1, either N or P limited, or N and P co-limited

Question 37

How do we determine which of C, N, or P are limiting? (3)

Answer 37

Divide the concentrations of each nutrient by the Redfield Ratio value Eg. 42,400 ug/L C divide by 106C 2400 ug/L N divide by 16N 20 ug/L P divide by 1P * whichever is smallest will run out first C = 400

Question 38

Who discovered phosphorus?

Answer 38

Alchemist Hennig Brandt in Germany in 1669

Question 39

Where did phosphorus get it’s name?

Answer 39

Phos-light Photos-bringing Light bearing - Venus, the morning star

Question 40

What short-lived molecules are formed when oxygen reacts with liquid or solid phosphorus?

Answer 40

HPO and P2O2, and they both emit visible light

Question 41

What compounds does phosphorus form due to its P3+ valency?

Answer 41

Phosphorus forms phoshorous and phosphoric compounds

Question 42

Why is phosphorus considered the giver of life? (4)

Answer 42

What makes P unique and critical to life is that P cannot circulate freely in the atmosphere = it has no gaseous cycle It plays a major role in biological molecules such as DNA and RNA It is a building block of DNA, cellular membranes, and energy metabolism Phosphorus is essential for all living organisms and the regular human body contains approximately 1.5 kg of phosphorus

Question 43

Why is it so important to conserve phosphorus? (5)

Answer 43

It has no known substitute It cannot be created It cannot be destroyed (since it has no gaseous phase) It is crucial for the worlds food supply as it is one of the three components of fertilizers (N-P-K) Approximately 80% of the phosphorus contained in rock mined for food production never reaches the food consumed globally

Question 44

Why is phosphorus also considered the destroyer of life? (4)

Answer 44

Contact with skin can cause severe burns and the vapours caused phossy jaw Used in the creation of incendiary bombs, smoke screens, and tracer bullets Weaponized chemically as nerve agents It’s in pesticides and herbicides

Question 45

Who wrote the Algal Bowl?

Answer 45

Jack Vallentyne

Question 46

What was the Lake 226 experiment? (3)

Answer 46

Experimental lakes area in northwestern Ontario was used to compare phosphorus nutrient loading and algae blooms N and C were put into one side of the lake, and N, P, and C on the other The side with P had an algae bloom

Question 47

How did the Algal Bowl summarize the eutrophication situation? (2)

Answer 47

In the 1960s it led to legislation that reduced P in detergents and waste water Vallentyne successfully predicted we would be living in an algal bowl by 2000

Question 48

What was the Broad Street Pump incident? (6)

Answer 48

Manure and human waste used to be recycled - even removing sheep droppings was illegal Cities began as an attempt to ward off outside threats, and populations began moving there during the Industrial Revolution Disease and terrible living conditions led to “night-soil” men removing waste from cities and transporting it to the fields Then the toilet was created in 1775 which increased the problem through cesspool flooding into the Thames River Dirty rag disposal into cesspool then led to the outbreak of cholera through polluted drinking water called the “Broad Street Pump” incident This showed people that infection and disease did not spread by smell but through water

Question 49

What societal changes happened after the Broad Street Pump incident? (6)

Answer 49

Hundreds of kilometres of sewers were constructed between 1859 and 1865 Bacteriology was created Water was chlorinated Water based disposal of human wastes fundamentally changed societal management of p nutrients from a cycling society to a through-put society The net result = water pollution and the start Of eutrophication Resulting in cultural eutrophication and public concern