WRITTEN EXAM LIMNOLOGY II, 15 hp, March 17, 2010
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Give your answer to each question on a separate sheet of paper,
Put you name on each sheet
Each question is evaluated at a scale from 0 top 5 points
----------------------------------------------------------------------------------------------------------1. Illustrate and describe a pelagic food web including the microbial loop. Which are the main
sources and sinks of matter and energy?
2. Per Lindström, a hobby gardener, noticed recently that his garden pond became more and more
dominated by phytoplankton, leading to a decreased visibility and increasing “greenish” water. His
neighbor, Fredrik Johansson, has taken limnology classes back in the good old days and he
remembers that by introducing piscivorous fish, you could reduce phytoplankton via a trophic
cascade. Per wants to be sure and hires you to model the scenario. He tells you that he has roach and
bleak in his pond; both are planktivorous fish and potential prey items for a piscivorous predator.
Your job is to construct a population model that describes the population dynamics of the
piscivorous predator, its two planktivorous prey, roach and bleak, and their common resource,
zooplankton in his garden pond. Remember, that zooplankton is self-limited at high densities.
Construct the model above. Do not forget to characterize ALL parameters that you include.
3. At the global scale, inland waters receive a substantial amount of organic carbon from the
terrestrial environment, but they deliver substantially less organic carbon to the oceans.
a) Describe the fate and processing of the terrestrially derived carbon that is not transported down to
the sea. (3 p)
b) How and why is the construction of hydroelectric reservoirs and other impoundments affecting
this pattern? (1 p)
c) Give an example of how climate change may affect the pattern. (1 p)
4. In the picture at the end of this form, there are three boxes with “P/R” (production to respiration
ratio) to the left of them, and four additional boxes. Indicate in the “P/R boxes” whether the P/R
ratio in the respective river sections is greater or smaller than 1 (>1 or <1). What is the form of
organic matter in the stream/river sections at the position of the other four boxes?
5. a) Explain the relationships between dispersal, , , and  diversity. (1 p)
b) Why is the global species richness ( diversity) of inland waters relatively high compared to
marine and terrestrial environments (1 p)
c) Which lakes and river systems have the highest  diversity (as far as we know) and why are they
so species rich? Give examples. (2 p).
d) Which lakes and river systems may have low diversity? Why? Give examples. (1 p)
6. Describe how ecosystem functioning and different aspects of biodiversity are related.
a) Define what Ecosystem Functioning means and the difference to Ecosystem Processes and
Ecosystem Services is (1 p).
b) Illustrate and describe at least three different scenarios of diversity-functioning relationship (2 p).
c) Explain the two main mechanisms that may explain a positive richness-functioning relationship
(2 p).
7. Sweden has to adjust the water quality assessment to EU guidelines. Name two major differences
between the Sweden specific guidelines that previously have been used and the new EU guidelines
when assessing the status of lake and river waters.
8 There are many obstacles that make the assessment of the ecological status of lakes and rivers
difficult. Give 4 different suggestions how the assessment could be improved.
LYCKA TILL !
GOOD LUCK !