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ECOR 9220 > Quiz 9 > Flashcards

Quiz 9 Flashcards

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1
Q

What is a nutrient loading model? (3)

A

A model that shows the max amount of nutrients that can be added to a lake without it becoming eutrophic given certain parameters (eg. Mean depth, residence time)

Lakes and reservoirs have a critical nutrient loading rate beyond which they become eutrophic

The objective is to stay in the “meso-oligotrophic” range

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2
Q

What are the main components that determine a lake’s productivity? (4)

A

Edaphic influence
Geographic influence
Morphometric influence
Human influence

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3
Q

history of fisheries biologists and predicting fish yield (5)

A

1927 - thienemann proposed that oligotrophic lakes were > 18m and eutrophic lakes were < 18m

1939 - Rawson produced chart showing inter-related factors affecting lake productivity

During WWII, the Canadian government asked Rawson to develop a method to predict sustainable fisheries production

He used mean depth to develop hyperbolic curves for variation in zooplankton, zoobenthos, and fish for various lakes in North America

Then after 1950, it was found that TDS actually have a larger effect than depth and models were created to take both into account, as well as residence time

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4
Q

What was discovered in the 1950s pertaining to plankton and fish production? (5)

A

Significant increases in plankton, bottom fauna, and fish quantities occurred with increases in total dissolved solids content (nutrients)

There was a significant difference demonstrated between summer epilimnion temperature and plankton

It was found that total dissolved solids were even more of a determinant of production than depth

However, depth and total dissolved solids could not be used alone or together to predict productivity within a region

Therefore, Dick Ryder came up with the Morphoedaphic Index to distinguish between regions

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5
Q

What is the generalization for the relationship between mean depth and production of plankton, bottom fauna, and fish?

A

Amount of fauna from lakes of great mean depth are never as high as those found in SOME lakes of low mean depth

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6
Q

Morphoedaphic Index (4)

A

Dick Ryder thought about using both parameters, TDS and mean depth, and combined them into an index expressed in log 10 units to compare regions

A very simple equation to predict fish yield:

MEI = total dissolved solids/mean depth

Yield increases from polar to tropical regions

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7
Q

Assumptions of the Morphometric Index (3)

A

Relationship between mean depth of lakes and various hydrologic characteristics (flushing rate and stratification regime)

water transparency characteristics (water colour and turbidity)

and the stoichiometric relationship among ions (expressed as a proportion between TDS and the concentration of primary nutrients, total phosphorus, and total nitrogen)

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8
Q

What happened to the predictive power of the MEI with increasing tropic levels? (2)

A

It became progressively weakened, even though these basic assumptions could be supported empirically

MEI could account for 85% of the variation in TP and TN, 50% of the variation in chlorophyll a, but none of the variation in biomass of herbivorous zooplankton (higher on the food chain)

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9
Q

Vollenweider’s first loading model (4)

A

Richard Vollenweider developed the critical loading rate theory and equations for lakes, based on the analysis of numerous lakes in Europe and North America

First model only used mean depth to determine critical P and N loading

Determined lake tolerance to P loading depending on size and depth

Was imperfect but useful for establishing permissible and dangerous loading levels of P and N

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10
Q

What is the general tolerance of lakes to P loading according to Vollenweider’s first model (2)

A

In general lakes can tolerate higher P loading rates as they increase with size and depth due to dilution

This is described as a higher flushing rate, so nutrients are diluted or flushed out = less effect of nutrient loading

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11
Q

Vollenweider’s second model (3)

A

Included water residence time, putting the flushing rate into the equation

This is a better model to use

Lp=P*z(1+sqrt(Tw))/Tw

Where:
Lp=critical annual P load (mg P/m2/yr)
P=spring overturn phosphorus concentration (mg P/m3) 
Tw=water residence time (yr)
z=mean depth (m)
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12
Q

What are the 9 major phytoplankton groups?

A 
Cyanobacteria 
Green algae 
Yellow-green algae
Golden-brown algae
Diatoms
Cryptomonads
Dinoflagellates 
Euglenoids
Brown and red algae
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13
Q

What are phytoplankton? (4)

A

Complex mix of algae and Cyanobacteria that are floating in standing water and slow moving rivers

Almost all phytoplankton species are obligate photoautotrophs

Some are mixotrophic

Some are heterotrophic

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14
Q

What is Cyanobacteria? (4)

A

True bacteria with simple prokaryotic cell structure

Reproduce by binary fission

Have chlorophyll a so can photosynthesize

Are structured like bacteria but function like an aquatic plant (no chloroplast or mitochondria)

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15
Q

Green algae (3)

A

Large and morphologically diverse group

Many members are flagellated

Can reproduce asexually and sexually

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16
Q

Yellow-green algae (2)

A

Unicellular, colonial, or filamentous

Characterized by carotenoids instead of chlorophylls which is why they’re yellow-green

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17
Q

Golden-brown algae (2)

A

Most are unicellular, some are colonial, but they are rarely filamentous

B carotene is dominant in addition to chlorophyll so they show a golden brown colour

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18
Q

Diatoms (4)

A

Very important group - the Bacillariophyceae

Primary characteristic is their silicified cell walls

Two types: Centric Diatoms which have radial symmetry

And Pennate Diatoms which have bilateral symmetry

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19
Q

Cryptomonads (2)

A

Unicellular and motile (single celled and capable of motion)

Have a variety of pigments, hence they can appear green, blue, red, or brown

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20
Q

Dinoflagellates (3)

A

Unicellular flagellates algae which are motile (single celled and mobile)

Reproduce sexually and asexually

Large body size (400um) which makes them relatively inedible to most grazing zooplankton

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21
Q

Eulenoids (4)

A

Large and diverse group

Few species are planktonic

Almost all are unicellular

They lack a distinct cell wall and have 2-3 flagella

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22
Q

Brown and red algae (4)

A

Brown algae are filamentous or thalloid

Most are marine, can be planktonic but not in freshwater

All attach to substrate

Red algae is rare in freshwater, none are planktonic, and if in freshwater are restricted to fast flowing streams of well-oxygenated cool water

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23
Q

Algae as nutrition (5)

A

Algae are a variety of sizes

Some are too small or too large to be eaten or are undesirable

The very middle size category (nanoplankton) are preferred for optimizing carbon flow to higher trophic levels (2.0-20.0um)

Cyanobacteria are inedible, non-nutritious, and or toxic

They also have a mucilaginous coating that protects them from being digested during passage through Daphnia

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24
Q

Algae that are too small (2)

Study These Flashcards
A

Picoplankton are undesirable as they are too small for larger zooplankton to consume (0.2 to 2.0um)

They expend much of their energy in metabolism and less carbon is available to transfer up to food web

25
Algae that are too large
Undesirable because microplankton that are bigger than 20.0um are too large for zooplankton to handle
26
What is the objective of lake and reservoir management? (3)
To maximize the number of edible algae, and ensure that carbon is being passed up the food web to zooplankton and eventually fish species This means increasing the relative number of nanoplankton
27
Microcosm experiment in Okanagan Lake (3)
Used 20L bag microcosms which showed a response to N and P additions This response was a classic sign of N and P co-limitation They also found micronutrient limitation which is rare
28
Daphnia growth depending on food type (2)
Grow at a much higher rate eating diatoms, over cryptoplankton, over chloroplankton, and even less eating cyanoplankton Same with reproduction - clutch size is much larger given diatoms over cyanoplankton etc.
29
What is the key to efficient energy transfer in lakes and reservoirs? (3)
Nanoplankton algae that have a lot of EPA and DHA as it makes their cells more flexible and better to absorbing nutrients These are classified as Omega-3 long chain PUFA which is essentially an Omega-3 fatty acid (same as humans)
30
What does DHA stand for?
Docosahexaenoic acid
31
What does EPA stand for?
Eicosaprntaenoic acid
32
The microbial loop (3)
Described a side-street trophic pathway in the aquatic microbial food web In this process, dissolved organic carbon (DOC) is returned to higher trophic levels via its incorporation into bacterial biomass This occurs because when zooplankton eat phytoplankton they are messy, and the remnant pieces of dissolved carbon is absorbed by bacterioplankton Heterotrophic phytoplankton then eat the bacterioplankton, returning the food chain to its classic form: phytoplankton-zooplanton-nekton
33
What is the problem with the microbial loop energy transfer?
The extra steps that occur in a microbial loop cause less energy transfer to higher trophic levels because there is just too many steps
34
Why do ultra-oligotrophic coastal lakes have longer food webs than interior lakes? (3)
Because their food webs start at picoplankton which means that there are more steps and less dissolved carbon being transferred directly from phytoplankton to zooplankton to fish Coastal microbial food web up to fish is 5 steps from small plankton to fat fish, while interior microbial food web is 3 steps from fat zooplankton to fat fish The goal in oligotrophic coastal lakes is to reverse this through controlled nutrient enrichment
35
Oligotrophication (4)
Reduction in nutrients Opposite of eutrophication Nutrients in waterways are never evenly distributed They’re either anthropogenically depleted or concentrated (eg. Upper watershed is nutrient deficient because of logging and damming, lower watershed has too much because of mills and sewage dumping)
36
What is oligotrophication caused by? (6)
Overfishing/collapse of anadromous salmonids Nutrient entrapment by impoundments Reservoir level fluctuations which reduce littoral productivity (which is about 10X pelagic productivity) Impoundments which flood wetlands and eliminate wetland and riverine production Forest harvesting Draining/ditching and channelization of wetlands
37
What is meant by the paradox and duality of P? (3)
Too much anthropogenic P causes pollution and algal blooms Strong anti-pollution laws are required to protect society and nature from pollution Too little anthropogenic P causes a collapse of fish stocks, and a loss of ecosystem goods and services
38
What are the major zooplankton groups? (4)
Calanoid Copepods Cyclopoid Copepods Cladocerns Rotifers
39
Calanoid copepods (3)
Small crustaceans 1-5 mm in length Commonly found as part of the free living zooplankton in freshwater lakes and ponds Can be distinguished from other planktonic Copepods by having first antennae at least half the length of its entire body
40
Cyclopoid Copepods (2)
Distinguished by other Copepods by having first antennae shorter than the length of the head and thorax Often predacious but can be herbivorous too
41
Cladocerns (5)
Small crustaceans found in most freshwater habitats including lakes, ponds, streams, and rivers Some are predacious but most are herbivorous feeding mainly on phytoplankton, decaying OM, and bacteria Some other species live either on or near vegetation at the bottom of lakes Can be problematic - holopedium (show up in calcium deficient lakes and are inedible) Can be essential - daphnia is a keystone species
42
Daphnia (5)
Keystone species in lakes Large, slow, and easy to capture Very nutritious - best possible food for fish Typically appear in mid to late summer and fall The energy that salmonids obtain from daphnia determines whether they survive or die during the winter when food supplies are low
43
Daphnia reproduction (3)
They have 2 modes of reproduction: sexual and non-sexual When daphnia reproduce sexually, they produce “ephippeal eggs” meaning that their purpose is to increase genetic diversity so that they can make it through bad conditions (eg. Produce sexually before winter) When daphnia reproduce non-sexually, they clone themselves — this is called parthenogenesis reproduction meaning there is no gene sharing (eg. Occurs in summer/healthy lake when daphnia are perfectly suited to their environment)
44
What is the goal of lake and reservoir enrichment in terms of daphnia? (2)
Create an environment with ideal conditions do that daphnia reproduce rapidly through pathenogenetic reproduction (cloning) Do this by conducting enrichment at the right times - eg. Reduce P loading rates in the late summer as sufficient P is already present (due to P excretions from daphnia and other zooplankton = messy eaters), and to avoid summer algae blooms
45
Rotifers (2)
Rotifers have a crown of cilia around their mouth that makes them appear to whirl like a wheel (“wheel-bearer”) Multicellular animals with specialized organs and a complete digestive tract so they are recognized as animals even though they are microscopic
46
What is the protocol for applying limiting nutrients? (7)
Desired concentration of nutrients Type of nutrients Seasonal timing of application Frequency of application Location of application N:P ratio of nutrients to be added Application techniques
47
Desired concentration of nutrients (4)
Use Vollenweider’s critical loading equation to find the optimal concentration of nutrients Incorporates mean depth and residence time Do not exceed oligo-mesotrophic loading rates, or BC provincial regulations of 10ug/L for drinking water or recreation lakes, or 5ug/L to 15 ug/L for aquatic life Ensure epilimnetic N:P Ratio is >10:1 during growing season (>10:1 you have an N deficiency, >20:1 you have a P deficiency)
48
What type of nutrients are usually used for lake enrichment? (3)
Liquid inorganic fertilizers (10-34-0, 28-0-0, 32-0-0) In some cases, solid agricultural fertilizer has been used by deploying a floating fertilizer dispenser box carrying Mono Ammonium Phosphate (11-52-0) and Diammonium Phosphate (18-46-0) The only option for N is Ammonium Nitrate (34-0-0)
49
Fertilizer terminology (4)
10-34-0 10 is % weight of nitrogen (can be NO3- and/or NH3N) 34 is % by weight as P2O5 - NOT P Therefore, must convert weight to P by dividing whatever the percentage is (in this case: 34) by 2.29 (which is half the molecular weight of P2O5) Eg. 34/2.29 = 14.8 P by weight 10kg of 10-34-0 contains 1.48 kg of P by weight K is expressed as K2O and is not used is stream enrichment so will always be 0
50
Storage and handling of fertilizer (3)
Most solid fertilizers absorb moisture, so they should be stored in a cool, dry place to avoid caking Nutrients in liquid fertilizer, ie. 10-34-0 will precipitate (salt out) in cold weather when mixed with 32-0-0 so best to blend with 28-0-0 if you expect to be operating under 10 degrees C Some fertilizers such as Ammonium Nitrate (34-0-0) are extremely explosive so are considered hazardous cargo
51
Seasonal timing of fertilizer application (4)
For lakes, there is a 20-22 week application window from late April to early September Nutrients can be added at a constant rate or “front end loaded” to mimic spring freshet P loading N is increased during the summer to prevent epilimnetic depletion of DIN and formation of Cyanobacteria (due to low Redfield Ratio) Remember: always adding 10x the nitrogen than phosphorus (20mg/m2 for N, 2mg/m2 for P) because ecosystem is sucking up 10N for every 1P (Redfield Ratio)
52
Frequency of nutrient addition (2)
Basic principle is to add as often as economically and technically feasible, however, in lakes and reservoirs, more frequent pulses favour smaller sized phytoplankton due to higher surface area to volume ratio Therefore, weekly loading is the standard for reservoirs
53
Location of application sites (2)
Lakes and reservoirs - apply near center Shore based pumps can be effective in small lakes
54
N:P ratio of nutrients to be added (6)
The Redfield Ratio is the cellular atomic weight ratio of C,N, and P in marine phytoplankton N:P ratios best approximated by DIN/TDP TN/TP is useless! N:P < 10:1 = N limitation N:P > 20:1 = P limitation N:P between 10:1 and 20:1 could be N or P limited, or N and P co-limited
55
What determines the current N:P ratio in a watershed? (3)
Underlying geology - Streams and lakes in volcanic geology is typically high in P and N limited Seasonal variation due to biological uptake and changes in runoff sources from major tributaries (Eg. Ground water vs snow melt) Most of BCs reservoirs are P limited or N limited or P and N co-limited
56
Application techniques: Lakes and reservoirs (3)
Typicaluse liquid fertilizer Can be dispensed aerially, from barges or boats, from shore-based pumping Density of fertilizer is very high, so it just be highly diluted first to prevent sinking (~10,000 to 1 is ideal; minimum is 1000 to 1)
57
Legal application of fertilizer and notification requirements (3)
Addition of nutrients is controversial is some areas but it is legal in Canada and the US Ensure all regulatory agencies are notified well in advance Do not exceed oligotrophic-mesotrophic loading rates, or BC provincial regulations of 10ug/L P
58
Project planning (4)
1-2 years planning required Involves collection and analysis of water chemistry, biota, residence time, stratification depth, water licenses, escapement trends Min 1-2 years of pre-enrichment data is required Monitoring is essential

ECOR 9220 (11 decks)

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