Practice Questions for Mid-term Exam
I.) Multiple Choice. You might expect about 20 multiple choice questions more or less
like these examples on the exam. They would be worth 1 mark each.
1.) On a graph of average stream discharge (m3/sec) (y-axis) against watershed area (km2)
(x-axis) a series of streams ranging from 1st to 3rd order all lie directly on a line that has a
slope of 0.01m3/sec per km2. This means that
a) all of these streams have the same watershed area.
b) the r value for the small watersheds is much lower than the large ones.
c) the r value for all these watersheds is 0.95m/yr.
d) the r value for all these watershed is very similar and equal to 0.31m/yr
e) none of the above is true.
2.)In a report on stream flow you find the hydrological balance equation given as follows:
R=(P─ E)DA ─ S , with P and E in mm/d, DA in m2, S in m3/d, and R in m3/d.
You attempt to apply this equation to your study stream; however, you find a large
disparity between your measurements of stream flow (R in m3/d) and the estimates
derived from the equation even though you have checked your flow measurements and
the estimates for the parameters P, E,S, DA and found them to be accurate.
The most likely reason for this disparity is:
a) the time units are in days and not years and the hydrological balance equation will
not work on such a short time scale
b) the estimates of drainage area should be in km2.
c) the precipitation and evapotranspiration values need to be expressed as m/d for
the equation to balance.
d) the equation will not provide accurate predictions until the rain stops
e) the hydrological balance equation does not take into consideration changes in
watershed storage occurring during the time interval over which the
measurements were made.
3.) To estimate the average flow in a stream you multiply the watershed area (m2) by the
runoff coefficient (r in m/yr) to obtain a flow estimate. The appropriate units for this
flow estimate are:
a) m/s
b) m3/s
c) m3/yr
d) m3/km2
e) m3/yr per km2 of watershed
4.)In general a stream of 3rd order is larger than a stream of 2nd order, but this need not
always be the case. The reason for this is
a) the 3rd order stream may come from a region with lower average runoff than the 2nd order
stream
b) some 2nd order streams may have larger watersheds than some 3rd order streams
c) some 2nd order streams have 3rd order tributaries
d) some 2nd order streams may have many 1st order tributaries, which together make them
larger than some 3rd order streams.
e) a, b and d are all correct
5.)A stream flowing from a region with high average runoff (r, m/yr) into a downstream
reach where evapotranspiration exceeds precipitation will
a) tend to decrease in discharge (m3/t) in its downstream reach
b) will likely not have a forested watershed in its downstream reach
c) will tend to decrease in width, depth and velocity in its downstream reach
d) will likely have a very large watershed for its discharge
e) all of the above are likely to be correct.
6.) The largest river in Alberta is
a) the Bow River downstream of Calgary
b) the South Saskatchewan River at Medicine Hat
c) the Athabasca River where it flows into Lake Athabasca
d) the Peace River where it flows into Lake Athabasca
e) the Slave River
7.) Alberta has more lakes and ponds in its northern portion than in its southern region
because
a) only the northern half of the province was glaciated
b) much of the northern half of the province is underlain by clay sediments from
proglacial lakes, whereas such deposits are not common in the southern half of the
province
c) the southern half of the province is mostly agricultural and most of the lakes and
ponds have been drained
d) In the northern half of the province most areas receive much more precipitation and
have therefore more runoff than similar sized areas in the southern half of the
province
e) None of the above statements are true.
8.) The lakes and ponds across most of Alberta tend to be much shallower than most of those
found in Ontario and Quebec, because
a) Alberta had fewer proglacial lakes than Ontario and Quebec
b) Alberta has much softer bedrock and deeper deposits of glacial till than Ontario and
Quebec and basins in such terrain tend to fill in with sediments than those found in
hard bedrock basin.
c) Alberta is much drier and has less runoff (except in the mountains) than most of
Ontario or Quebec
d) b and c are both true
e) a, b and c are all true
9.) Many people are not easily convinced that rivers flow faster in their downstream reaches
than in their upstream tributaries because
a) rivers tend to be much wider downstream with their most rapid sections toward the
middle and away from shore, where most people stand and look at the river.
b) upstream tributaries tend to be more turbulent than downstream reaches and thus
appear to be flowing faster.
c) Downstream reaches tend to be flatter (less steep) and thus appear to flow slowly
d) All of these are likely true
10.) Rivers that flow from mountainous regions tend to have most of their salmonid fry
(newly hatched fish) habitat in their 1st and 2nd order tributaries because
a) high elevation streams are generally cold year around and salmonid fry need cold
water
b) salmonids tend to spawn in the gravels of 1st and 2nd order streams and fry tend to
stay near their place of birth
c) stream velocities and depths tend to increase downstream and juvenile providing
better habitat for juveniles and adults.
d) a, b, and c are all true
e) none of these are true.
Exceedance probability (percentiles)
99.9
99
90
70
50
30 20
10
1
0.1
1.0
o
0.1
Runoff
coefficient
(r)
m/yr
o
o
o
o
0.01
11
Non-exceedence probability (percentiles)
11.) A region has the above probability distribution for runoff. Based on this the
discharge in a stream with a 1km2 watershed should be expected have a discharge that
exceeds 1 x 105 m3/yr once in
a) 4 yr
b) 10 yr
c) 20 yr
d) 100 yr
e) none of the above
12.)Which of the following is not an important reason why river managers have
traditionally tried to constrain the seasonal variability of discharge?
a) flood events that occur during rainy periods can be very costly
b) storing the water from flood events can be very useful for agriculture
c) stable flow regimes are better for fish populations
d) stable flow regimes are better for assimilating pollutants such as sewage
e) stable flow regimes are better for shorebirds, dabbling ducks and amphibians
13.) Two nearby streams have similar runoff values (Q/DA) and precipitation regimes,
but stream A has much more variable discharge, responding to precipitation events more
rapidly and with higher runoff peaks, followed by a sharper decline to a lower basefly
level. The most likely reason for this difference is
a) stream A has had its watershed clearcut whereas stream B has not
b) stream A flows out of a lake and stream B does not
c) stream A has more gravel in its streambed than stream B
d) all three are equally likely
e) b and c are both likely.
14.) Two nearby streams had similar long-term mean runoff values and precipitation
regimes, but recently stream A has had higher and more variable discharge, responding to
precipitation events more rapidly and with higher runoff peaks, followed by a sharper
decline to a lower base level. Winter flows in this stream are much lower than they were
in the past. Stream B has not changed. The most likely reason for this difference is
a) stream A has had its watershed clearcut whereas stream B has not
b) stream A has been dammed in its upper reaches
c) Stream A has recently had more rain
d) A ski-hill in a neighboring watershed has been drawing water from Stream A for
snow-making
e) All of these are likely
15.) Increased algal growth is often seen in streams whose watershed have been clearcut
because
a) the temperature tends to rise
b) the water has become more turbid and coloured
c) export of nutrients from the clearcut watershed to the stream has increased
d) the clearcutting has reduced shading so more sunlight strikes the stream bed
e) both c and d are correct
16.) Siltation is a problem for fish eggs in the gravel because
a) silt is toxic to the eggs
b) silt stimulates algal and fungal growth on the eggs
c) silt plugs up interstitial spaces in the gravel so that throughflow of oxygenated
water is impaired
d) silt accumulation provides an excellent environment for certain benthic
invertebrates which eat the eggs
e) silt stimulates bacterial growth which depletes oxygen and produces toxic
substances.
17.) Temporary ponds and swamps are very suitable habitats for aquatic insects and some
other invertebrates because
a) the habitat persists long enough to allow such organisms to complete their life
cycle
b) many of the larger animals that prey on or compete with these invertebrates are
not able to invade and complete their life-cycles in temporary water bodies.
c) Temporary ponds are warm and nutrient rich and algal growth is very rapid
d) a and b are both true
e) a, b, and c are all true
18.) Damming of rivers often reduces flood plain habitat in downstream reaches because
a) peak flood waters are generally held back in reservoirs and not immediately
released to the downstream reaches
b) seasonal variation in the discharge to downstream reaches is reduced
c) damming is often accompanied by levees and other channel alterations aimed at
flood control or improving navigability.
d) damming is often accompanied by river diversion for irrigation and other
domestic or industrial purposes, which reduces the downstream discharge.
e) All of these are true
20.) Silt and mud tends to accumulate on the inside of meander loops because
a) this is where most of the stream bank erosion takes place
b) this is where stream velocities are slowest and thus fine particles, which are
usually eroded from the stream bank on the outside of meander loops, are able to
settle out and not be resuspended
c) material eroded from riffles tend to settle in pools
d) Cross-sectional flow is generally strongest at a bend causing fine particles to settle
out by centrifugal force
e) None of these are true.
21.) Oxbow lakes are important to the biodiversity of a river because
a) they are a stable source of standing water on the flood plain and many species in
the river ecosystem thrive better there than in the mainstream
b) many fish and other species are trapped in the oxbow basin and can only get back
into the river during flood events
c) these lakes are usually warm, shallow and productive, and many fish, amphibians
and insects are produced in them.
d) a, b and c are all true
e) a and c are true.
22.) Which of the following features of rivers are not indicative of past changes in course
over the years
a) the presence of many intersecting dried up channels
b) the presence of oxbows, beaverdams and wetlands in the river flood plain
c) the presence of braided sections in the river bed
d) the presence of steep canyons along the river
e) none of these
23.) A road with a bridge crossing a river can significantly alter the long-term course of
the river’s meander, even without obstructing its present pattern of flow because
a) pilings and other physical structures placed along the river bank may deflect water
during floods and affect the pattern of scouring
b) bridge pilings are strongly reinforced to stabilize the bridge, and can preventing the
river from shifting at the bridge crossing.
c) old river channels can be blocked by the roadbed leading up to the bridge, and this can
prevent the river from occupying these old channels in the future.
d) a, b and c are all true
e) only a and b are true.
24.) Feedlots located within a river flood plain or along its terraces can dramatically
affect it because
a) river bed gravels are very permeable and nutrients from livestock will seep into
the bank and find their way into the river
b) pathogenic bacteria growing in the soil under the feedlot can find their way into
the river.
c) The smells from the feedlot can influence animals and/or people using riparian
woodlands along the river
25.) Which of the following is not a way in which glaciation has contributed to lake
formation
a) glaciers can impound and divert the flow of rivers and produce large proglacial
lakes
b) moraines or glacial till pushed along by advancing glaciers can impound water
courses and produce lakes
c) mountain glaciers can scour out deep basins that will later be occupied by lakes
d) large blocks of ice in thick till deposits can produce “kettle” basins when they
melt
e) tectonic basins (grabens) can be created when the heavy weight of glaciers
produce faults in the earth’s crust.
26.) The lake trout (Salvelinus namaycush) is thought to have evolved in glaciated North
America during the ice age because
a) its natural range consist mostly of deep, thermally stratified lakes that are either
remnants of proglacial lakes or easily accessible from them.
b) It is one of the few salmonids that has no tendency to run to the sea and is found
only in North America.
c) Its distribution south of the glacial boundary has resulted entirely from human
introductions
d) it is our most coldwater adapted fish species
e) all of these reasons are important contributors to this idea
27.) Glacial relicts such as mysid shrimp are found in very few Alberta lakes because
a) Most Alberta lakes tend to be too shallow to form thermoclines
b) Many Alberta lakes are too productive to maintain high oxygen levels in their
hypolimnia
c) Mysids were present, but have mostly been eliminated by fish predators
d) a, b and c are all true
e) only a and b are true.
28.) Although mysid shrimps are an important source of food for young lake trout in
many Canadian lakes, their introduction beyond their native range has proved disastrous
to the fisheries in many lakes because
a) mysids feed on larval stages of many fish species
b) mysids compete for the zooplankton food sources that many fish require
c) mysids carry diseases that have proved lethal for many fish species
d) mysids carry on vertical migrations that provide them with a refuge from
predation from many epilimnetic fishes
e) b and d are both correct
29.) Tectonic lakes like Baikal and the Rift Valley lakes in Africa contain more species
than glacial lakes because
a) their basins are deeper and thus have more habitat diversity
b) they have survived uninterrupted for millions of years old and have had time to
develop rich endemic faunas
c) they are remnants of inland seas and thus contain many ancient marine lineages
d) b and c are both true
e) a and b are both true
30.) Cirque lakes are often milky or pale blue in colour because
a) The water frequently contains a great deal of suspended glacial clay which
scatters light
b) The unique phytoplankton found in these lakes imparts this milky appearance to
the water
c) They reflect ultraviolet light
d) The waters are rich in organic matter from the watershed
e) None of these are true.
31.) Crater lake is very unique in comparison to other lakes because
a) it has almost no watershed and any nutrient input that it has comes from rain.
b) its waters are among the least turbid and lowest in dissolved organic matter
content of any known lakes
c) it has no rooted plants and almost no plankton growing in it
d) sediments don’t start to accumulate in it until depths > 90 m are reached
e) all of the above are true.
32.) Lake trout from all over western Canada, as far east as Manitoba and western
Ontario, share genetic similarities with those from Waterton Lakes, because
a) lake trout can disperse down rivers and find their way into other lakes
b) lake trout from Waterton Lakes have been raised in hatcheries and introduced to
many other lakes
c) Waterton lake is a remnant of a large lake that was formed when mountain glacier
runoff was impounded by a continental glacier. This lake shifted toward the north
and east gradually as the glacier receded, dispersing lake trout widely.
d) Waterton Lake habitat is very similar to that found in other Canadian lakes.
e) None of these are true.
33.) How much water flows into a lake from its watershed if the drainage area is 6 km2
and the runoff coefficient is 0.2 m/yr. The area of the lake is 2.5 km2, and evaporation
exceeds precipitation on the lake by 0.085 m.
a) 1.2 x 106 m3/yr
b) 1.2 x 103 m3/yr
c) 9.9 x 105 m3/yr
d) 5.88 x 106 m3/yr
e) none of the above
34.) What would you expect the mean flushing rate to a lake to be if it had a drainage
area is 6 km2 and the runoff coefficient is 0.2 m/yr. The area of the lake is 2.5 km2, its
mean depth is 15 m and evaporation exceeds precipitation on the lake by 0.085 m.
a) 0.032 /yr
b) 0.032 yr
c) 3.9 yr
d) 0.028/yr
e) 0.32/yr
35.) A lake has a drainage area is 6 km2 and the runoff coefficient is 0.2 m/yr. The area of
the lake is 2.5 km2, its mean depth is 15 m and evaporation exceeds precipitation on the
lake by 0.085 m. How much of the water flowing into this lake could be allocated for
irrigation before its water level would be expected to decline?
a) 82.5 %
b) 92 %
c) 8.25%
d) 51%
e) none of these
36.) The sea of Aral in the former Soviet Union has nearly dried up over the last 50 yr.
because
a) all of the inflowing water has been allocated to irrigating cotton farms
b) evaporation from the lake was not properly factored into the allocation for
irrigation
c) climate change has resulted in a series of excessively dry years
d) the increasing salinity of the lake has increased its evaporation rate
e) none of these are true.
37.) The area under the hypsographic curve of a lake represents its
a) mean depth
b) the surface area of the lake minus the area of its islands
c) volume
d) the depth ratio
e) none of the above
38.) A lake with a surface area of 3.5 km2 and a mean depth of 10 m will have a volume
of
a) 0.035 km3
b) 0.35 km3
c) 3.5 x 106 m3
d) 3.5 x 108 m3
e) none of the above
39.) The depositional boundary for mud in a lake with a large surface area lake will
usually be found at greater depth than in a lake with small surface area because
a) lakes with large surface area are usually deeper
b) lakes with large surface area have more steeply sloped shorelines
c) lakes with large surface area have larger waves, and therefore wind induced currents
move water and resuspend particles at greater depths
d) suspended sediment particles sink faster in larger lakes
e) larger lakes have less suspended sediment particles.
40.) If two lakes have the same surface area, the depositional boundary for mud will tend
to be deeper in the one with a more steeply sloped basin because
a) lakes with steep shores will tend to have larger waves
b) wind induced current will not attenuate with depth as rapidly in steep lakes
c) sediments that have settled on steeper shores are less stable and more easily
resuspended
d) particles sink faster in lakes with steep basins
e) none of the above explanations are likely to be true.
41.) Varved sediments commonly occur in glacial lakes because
a) streams flowing off glaciers carry a great deal of clay during the summer months
which appears whitish compared to organic sediments.
b) Glacial lakes have more calcium carbonate precipitates during summer which
imparts a whitish layer to the sediment
c) Glacial lakes have more diatoms which settle during spring and give a banded
appearance to the sediment core
d)
e) none of the above are true.
42.) Lead-210 is less abundant farther down in a sediment core because
a) it is produced from the decay of Uranium-238 which is not abundant deep in
sediments
b) lead-210 fallout from the atmosphere did not occur prior to the nuclear age
c) lead-210 decays to lead-206 with a half-life of 22 yr so that deeper sediments tend
to lose their lead-210.
d) Lead-210 is not well attached to particles and tends to be upwardly mobile in
sediments
e) None of the above are true.
43.) Cesium-137 cannot be used to date old sediments in the manner that lead-210 can
because
a) this isotope has a short half-life and will be depleted from deep sediment layers
b) this isotope did not exist prior to the nuclear age and is therefore absent from deep
sediment layers
c) this isotope was produced in large amounts from volcanic ash and this old
sediment layers contain large cesium peaks
d) it is not well attached to particles and in some sediments tends to diffuse within
the sediment core
e) b and d are both correct
44.) In a lake with a Secchi disk transparency of 4m we would expect the 1% light level
to be at which depth contour
a) 8.1
b) 10.8 m
c) 1.1
d) 9.5
e) none of these
45.) The outer boundary of the littoral zone is determined by
a) the 1% light level
b) the depth at which fine sediments begin to accumulate
c) the position of the thermocline
d) the amount of convective circulation in the water column
e) the depth at which sufficient light reaches the substrate for aquatic macrophytes to
begin growing
46.) Water in a deep lake with very little dissolved organic matter is blue because
a) blue wavelengths are absorbed preferentially by this water
b) the red end of the visible spectrum is preferentially absorbed by water, and thus
backscattered light from deep in the lake is nearly all blue.
c) The colour of the sky is reflected back from the lake making it appear blue
d) The phycocyanin pigment of cyanobacteria imparts a blue colour to the water
e) None of these is true
47.) Water with high dissolved organic matter content appears to have a yellow-brown
colour
a) water absorbs red wavelengths the most, and the organic matter absorbs mainly
the blue and green wavelengths allowing the yellowish part of the spectrum to
penetrate the farthest into the water
b) yellowish wavelengths are absorbed preferentially by the organic matter
c) many of the chrysophyte algae that live in these lakes have carotenoid accessory
pigments that impart a yellowish tinge to the water.
d) Suspended soil particles scatter mainly the long and short end of the visible
spectrum causing the water to look yellowish.
e) None of the above.
48.) Plant growth at the lower photic zone boundary of the littoral is very poor in
brownish coloured lakes because
a) the dissolved humic matter is toxic to plants
b) the most photosynthetically active wave lengths cancel each other out
c) the coloured water absorbs mainly the red and blue end of the spectrum which are
the most photosynthetically active, leaving less active wave lengths to penetrate
the deepest
d) soil humic particles tend to settle out in deep water on top of the plants covering
them with sediment
e) none of the above.
49.) Gross Primary productivity during a measurement time interval can be estimated by
a) the increase in O2 that takes place in the light bottle because photosynthesis
exceeds respiration, plus the decrease in dissolved oxygen that takes place in the
dark bottle due to respiration.
b) The increase in O2 that takes place in the light bottle because photosynthesis
exceeds respiration.
c) The increase in O2 that takes place in the light bottle minus the decrease that takes
place in the dark bottle
d) The increase in O2 that takes place in the light bottle plus twice the decrease that
take place in the dark bottle
e) None of the above
50.) The carbon-14 method of measuring primary productivity works on the principle that
a) all of the C taken up by the phytoplankton in the sample bottle is radioactive
b) the same proportion of radioactive C is taken up as non-radioactive C, and that all
of this is retained by the Millipore filter.
c) that none of the radioactive C incorporated is released in respiration during the
experiment
d) that each molecule of radioactive C produces causes a photon to be released by
the fluorescent medium that the algae are dissolved in.
e) inorganic C will be taken up by all organisms present in the sample bottle.
51.) Diurnal changes in O2 within the water column of a lake
a) will tend to make the O2concentration supersaturated at night
b) will tend to make the O2 concentration supersaturated in the deep waters below
the photic zone
c) result only from photosynthesis in the water column
d) will reflect the combined effects of photosynthesis, respiration and atmospheric
exchange with the lakewater
e) are solely a result of the diurnal changes in temperature and its effect on O2
solubility
Three species of algae found in the phytoplankton community of a lake have the
photosynthesis/irradiance curves designated A, B, and C
A
GPP/t
per unit of
biomass
B
C
10%
25%
50%
Light
intensity
53.) Assuming that A and B are equal in all respects other than their P/I curves, under
what conditions would you expect B to outperform A?
a) in the epilimnion of a clear stratified lake, (25% light level at the thermocline)
b) in the well-mixed water column of a deep lake (25% light level at 10m, max depth
100 m)
c) in the hypolimnion of a clear stratified lake (25% light level at the thermocline)
d) growing on the substrate near shore in the littoral zone of a clear lake (25 % light
level at the outer boundary of the littoral)
e) a and d are both true
f) b and c are both true.
54.) Assuming that A, B and C are similar in all respects other than their P/I curves,
which of these species would you expect to perform best in the well mixed water column
of a deep lake (25% light level at 10 m, max depth 100 m)
a) A
b) B
c) C
d) A and B would do equally well
e) A and C would do equally well
55.) You find that C outperforms both A and B during the summer months but not in the
early spring. Assuming that all three species have similar temperature optima and
nutrient uptake affinities, which of the following explanations is most plausible
a) C is the least palatable species to herbivorous zooplankton
b) B does best at low light intensity, and A does best at high light intensity, but C
does best under fluctuating light intensities
c) C has the most eccentric shape
d) a and b are both plausible
e) a and c are both plausible
56.) Consider the following diurnal oxygen cycles in a river, C represents the 100%
saturation level
A
B
O2
mg/L
C
Day
Night
A and B are recorded at two sites: (1) is at the outlet of a sewage plant where microbial
treatment breaks down all organic matter in the sewage to mineralized nutrients (eg N, P
and CO2), (2) is at an untreated sewage outlet.
a) Curve A most likely represents site 1 because mineralized nutrients will contribute to
higher photosynthetic rates and lower respiration rates.
b) Curve A most likely represents site 2 because untreated sewage will likely lead to
higher respiration rates.
c) Curve B most likely represents 1 because mineralized nutrients will likely lead to
higher respiration rates
d) Curve B most likely represents 2 because the saturation level of oxygen will likely be
lower in the presence of untreated sewage.
e) none of these are true.
57.) In situations where light can reach the substrate,
a) submerged macrophytes and benthic algae will be the dominant 1o producers,
since the substrate will generally provide more nutrients than the water column
b) the phytoplankton will be the dominant 1o producers since they will have first
access to light
c) submerged macrophytes and benthic algae will be the dominant 1o producers
because they will have first access to light.
d) Phytoplankton will be the dominant 1o producers because they will use up all the
nutrients in the water column.
e) None of these are true.
58.) Which of the following is not a plausible reason why macrophyte beds constitute
excellent habitat for many species of fish?
a) they provide abundant refuges for small fish from predators
b) they provide enough primary productivity to support a rich community of
invertebrates and fish
c) they provide a continuous supply of dissolved oxygen
d) they provide many ambush sites for predators
e) they attenuate waves and enhance sedimentation rates, leading to enhanced
nutrient accumulation in sediments.
59.) High benthic algal biomass and productivity below hypolimnion release dams can be
expected because
a) hypolimnic waters in the reservoir are usually nutrient rich as a result of
sedimentation of phytoplankton and inorganic particles.
b) year-round ice free conditions will be present below the dam
c) the watershed will likely provide a rich supply of organic matter.
d) a and b are both true
e) b and c are both true
1.) Phosphorus is not an important constituent in which of the following?
a) DNA
b) membranes
c) proteins
d) ATP
e) RNA
3) Which of the following an essential nutrient only for diatoms
a) K
b) N
c) P
d) Fe
e) Si
6.) Macrophytes and benthic algae generally outcompete phytoplankton in littoral regions
of oligo- and mesotrophic lakes and rivers because
a) they can outcompete phytoplankton for light
b) they produce substances that are toxic to phytoplankton
c) they are generally more limited by carbon than by N and P
d) they can access N and P from sediments, which phytoplankton cannot
e) they have very low nutrient requirements
Correlational studies can sometimes provide a more accurate picture of the resource that
is limiting to primary producers than experimental manipulations because
a) experiments are often limited in duration by practical constraints and sometimes
only tell us which nutrient is limiting on the short-term
b) experiments often involve simplified treatments that isolate the primary producers
from consumers which is a situation that doesn’t often occur in nature.
c) While experiments can be conducted on a variety of spatial and temporal scales,
they are usually conducted on smaller spatial scales than real systems operate,
making the results an abstraction
d) Many systems, eg large rivers are too spatially complex for clear-cut experimental
treatments to be carried out.
e) None of the above are true
f) All of the above are true
Schindler’s studies on whole lake systems in the Experimental Lakes area of western
Ontario, were unique in that
a) they were the first attempt to manipulate P, N and C simultaneously
b) they completely controlled for all physical factors that could affect the primary
productivity of the ecosystem
c) they were thoroughly replicated and therefore very statistically conclusive
d) they were the first attempt to manipulate the nutrient loading regime of a lake
e) they were the first attempt to study whole lakes in a controlled experimental
framework
The Lake Washington “experiment” influenced our ideas about the functioning of lake
ecosystems because by diverting sewage from the lake and monitoring the responses
a) it showed that Phosphorus was a key limiting nutrient
b) it showed that sewage input to a lake could grossly change the nature of the
ecosystem
c) it showed that environmental science could have a great impact on social
decisions
d) it showed that nutrient diversion always leads to significant improvements in
water quality of a lake
e) both b and c are true
f) both a and b are true
Which of the following is not a reason why nutrient diversions like the Lake Washington
sewage diversion experiment don’t always lead to significant improvements in water
quality.
a) the lake in question may not be limited by any of the nutrients being diverted
b) the internal nutrient load may be so great that the external load diversion may be a
small fraction of the total load
c) the water may be so turbid from clay or other sediment loading that the light
regime is actually limiting to primary producers
d) the water renewal rate may be so slow (water retention time so long) that it takes
many years for a change in the nutrient loading regime to have a significant effect
on the lakes nutrient concentration
e) the non-point source loadings may be so large that the diversion may constitute a
tiny fraction of the total nutrient load to the lake
f) all of these reasons are reasonable possibilities.
Trophic classifications are usually based on either the total Phosphorus content of the
water or the concentrations of Chlorophyll a because
a) P is the only important limiting nutrient that can determine the productivity of the
primary producers
b) This is a convient approach to classification that uses easily measured parameters.
c) P and chlorophyll a are so well correlated that they always lead to the same
trophic status determination.
d) Lakes that are limited by other nutrients like, say N or Si are rare, are too rare or
unimportant to worry about
e) The effects of other limiting nutrients was not known at the time that the P-chl
approach became popular.
II.) The density vs temperature graph of fresh water is
For each of the following properties or observations indicate yes, if the information in the
above graph helps you to infer it, and no, if it does not (1 mark each)
a) ice will always float on water
b) The thermocline will become less stable as the surface waters cool from 20oC
down to 10oC.
c) under ice cover colder water will float on top of warmer water
d) ice will tend to crack on very cold days
e) plankton will sink more slowly at 4oC than they will at 20oC
f) in a small pond convection currents can be very strong during summer
g) The mud layer under the lake will tend to warm and cool more slowly than the
water
h) The diffusion rate of heat through the thermocline will be greater in a large than a
small lake.
i) The sinking speed of an algal cell with=1.0004 g/cm3 likely be at least twice as
fast at 11oC as it will at 4oC.
j) River water flowing into a lake during the spring and early summer will tend to
form a thermal bar rather than mix with the lakewater.
III.) Explain why in a few sentences, that is give a reason to explain the observations
listed below. You might expect to have to do around 4 such short answer explanations on
the exam.
1.) On a graph of average stream discharge (m3/sec) (y-axis) against watershed area (km2)
(x-axis) a series of streams with the same runoff coefficients but different watershed
areas, all lie directly on a line whose slope equal the runoff coefficient for the area.
2.) Watershed processes are becoming a subject of major importance to many large cities.
3.) Aquatic ecosystems provide many services to society,that would be very costly or
impossible to replace with human-made substitutes.
4.) Governments are beginning to strongly question the utility of many dams on rivers.
5.) Explain why it is necessary to integrate over the photic zone to obtain accurate
estimates of areal primary productivity.
6.) Stream flow is quantified in two different ways that mean very different things,
volume/t and distance/t. Explain.
7.) Third order streams are not always larger than second or first order streams.
8.) Upstream reaches tend to have more habitat for salmonid fry, whereas juvenile and
adults tend to find more suitable habitat farther downstream.
9.) River managers have traditionally tried to constrain the variability of discharge
regimes.
10.) Streams whose watersheds have been clearcut, typically exhibit shorter hydrographic
lag-times and lower base-flows
11.) Stream primary producers can be affected by clear-cutting in a variety of ways.
12.) Siltation changes the dissolved oxygen regime in gravel.
13.) Temporary ponds and swamps significantly enhance biodiversity
14.) Flood plains can greatly enhance biodiversity in river ecosystems
15.) Damming of rivers can dramatically impact flood plain ecology downstream
16.) Three-quarters of the lakes in the world are found in glaciated regions
17.) Radon-222 can be a health hazard even though it is an inert (non-reactive) gas.
18.) Lead-210 occurs in the atmosphere as a result of natural processes, not nuclear
testing.
19.) Nutrient addition experiments in stream communities often failed to demonstrate nutrient
limitation
20.) Algae with different photosynthesis/irradiance curves can coexist in lakes
IV) Answer in a well organized paragraph of around 200 words. Use illustrations if
necessary to explain your ideas. On the exam you would have to write 1 essay of this
kind and you will have several to choose from.
Two key features of stream and river flow are extreme temporal variability, and the tendency to
meander. Explain how these create habitat diversity for aquatic organisms, through its effects on
channel morphology, sediment deposition, erosion, and the flood plain.
With reference to the hydrological balance equation explain why most streams on the landscape
flow continuously (albeit with huge variance) despite the episodic nature of precipitation. Contrast
this with the situation you might expect in a storm sewer—a man-made drainage system designed
to conduct storm runoff—which has high discharge for a few hours after a storm and then dries up
completely.
Show how the processes of photosynthesis and respiration are linked to changes in O2, and explain
how oxygen concentrations in a lake water column change throughout the daily cycle and how
these changes can be used to estimate the rates of photosynthesis and respiration of the lake
community.
Outline the general pattern of seasonal succession in lake phytoplankton, and explain it with
reference to seasonal changes in lake temperature and stratification, nutrient availability, and
herbivorous zooplankton.
Outline the major ways that aquatic ecosystems provide free services to the human economy that
are difficult or impossible to replace with human-made substitutes.
Outline the role of wind and wave action, light, and lake basin shape in determining the boundaries
of the littoral zone, the thermocline, photic zone depth and the boundaries of the depositional zone.
With reference to the hydrological balance equation explain why most streams on the landscape
flow continuously (albeit with huge variance) despite the episodic nature of precipitation. Contrast
this with the situation you might expect in a storm sewer—a man-made drainage system designed
to conduct storm runoff—which has high discharge for a few hours after a storm and then dries up
completely.
Two key features of stream and river flow are extreme temporal variability, and the tendency to
meander. Explain how these create habitat diversity for aquatic organisms, through its effects on
channel morphology, sediment deposition, erosion, and the flood plain.
Most lakes in the world are found in glaciated regions. Explain how glacial processes form lakes.
Although there are fewer lakes in non-glaciated regions, in what ways are they different from those
in glaciated areas.
What are the factors that determine the apparent colour of a water. How would the colour of water
be an important environmental factor for photosynthetic organisms?
Explain how physical and biological factors interact to produce a seasonal pattern of species
replacements in lake phytoplankton.
What is meant by nitrogen fixation and why is it ecologically important. Explain which organisms
can perform this function and how they can exploit this capability in aquatic ecosystems. How have
humans exploited this in agriculture?
Explain how oxygen concentrations in a lake water column change throughout the daily cycle and
how these changes can be used to estimate the rates of photosynthesis and respiration of the lake
community.
Contrast the effect that nutrient enrichment, and the invasion of zebra mussels, would be
expected to have on the outer boundary of the littoral zone in a lake.
Explain the differences that one expects to see in the vertical oxygen gradient in a eutrophic and
an oligotrophic lake. Assume that the lake is deep enough to stratify and form a stable
hypolimnion during the summer.
What are the nutrients that most commonly limit primary production in aquatic ecosystems? Explain
the biological basis for the requirement for these nutrients, and explain how nutrient limitation in
aquatic ecosystems is demonstrated.