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River and Lake Ecology

Ludwig Triest and Iris Stiers

1. Algal height

A. x-axis September and October, y-axis height of an algae (cm) attached on rock in shallow (5-20cm) and and deeper

(>20cm)water

Experiment 1: 1. addition of predator (perch) 2. addition of herbivorous fish

B.graph with September and October on x-axis, algae height Experiment 2: 1.no herbivorous fish

2.herbivorous fish present

Answer: fish is to big to go to the shallower areas so herbi-fish more present algal height lower

to prove that this fish is really eating on this filamentous algal graph B. No fish higher plants. fish grazing pressure lower algae 2. Migration of Zooplankton

several graphs with free Cladocera in temperate and subtropical lakes. Turbidity increasing, x-axis day and night, cladocera in submerged vegetation and open water

and a little graph showing that Fish are 10 times more abundant in subtropics than in temperate climates and that they are more

abundant in submerged vegetation in the subtropics

Answer: more vertical migration in subtropics because fish to abundant in submerged vegetation for horizontal migration 3. Changes in Zooplankton Dominant Species

2 lakes: One with natural dynamics, and one with fish removal. For each lake there was a series of graphs: Relative dominance (%) of the total groups of zooplankton (copepods, cladocera…); Average size of zooplankton; Dominant species of cladocera; Abundance of

cladoceras > 1mm; ratio zoo:phyto biomass; ratio of chla:TP. You had to explain the system in each lake.

Then they asked what was the main difference between them (so what the fish removal caused, and why); asked if the ratio phyto:zoo changed because of a change in each group, and the same for the ratio Chla:TP; how you could relate both graphs.

Iris also asked how we measured Chla in the praticals, and why we measure two peaks in the spectrophotometer (one for chla and one for

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pheophytin, it’s what I said). She also asked me to mention on large cladocera without being Daphnia

4. Introduction of Zebra Mussel It was 4 graphs:

1) Time (years) in x-axis, Zebra-mussel abundance in the right-y-axis, another mussel abundance in left-y-axis.

2) Time (years) in x-axis, Zebra-mussel abundance in the right-y-axis, abundance of rotifers in left-y-axis.

3) Time (years) in x-axis, Zebra-mussel abundance in the right-y-axis, Secchi Disk depth in left-y-axis.

4) Time (years) in x-axis, Zebra-mussel abundance in the right-y-axis, and chl-a in left-y-axis.

So you had to say what changes you could see, how the ZM impacted the system, and why. And what could expect from the zooplankton, macroinvertebrates and macrophytes.

5.nutrient loading

you have to draw the profiles of NH4, NO3, PO4, chironomids, heterotrophic bacteria, protozoans and Tubilex

6.Graphs with T Phosphorous concentrations, large and small

phytoplankton biomass, Secchi depth, Daphnia abundance over a month period. What happens in an experiment when a silver Carp (filter-feeding) is introduced and when is not present.

7.I had three graphs: change in Total zooplankton, large and small zooplankton densities over a year period in an east-asian river. Explain the dynamics in each group according to the rain and dry seasons

8.My first graph was about three sections of river with different concentrations of periphyton, and shrimps as the model organism. So you have to tell what's is happening with the algae concentration in each section

9. Concentration of zooplankton in dry and rainy season. I had two graphs showing concentrations of rotifers and copepods through the year. Then you have to explain what is happening with the

concentration of each one

10. Graphs about the relations between carp, vegetation and waterfowl.

11. How chl-a, transparency and phytoplankton change after filter feeding fish is introduced.

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12. First question: There were four graphs showing the relationship between the zebra mussels vs Unionid mussels, zebra mussels vs rotifer, zebra mussels vs Secchi depth and zebra mussels vs chl a from the year 1991 to 2009. You have to compare the relationship and discuss what happened in the four graphs.

Questions raised during oral:

What do you expect for other zooplankton groups, macroinvertebrates and macrophytes?

How the chl a sample was prepared? The process of chl a determination in the lab?

13. Second question: There were two lakes with six graphs each that must be compared. The first two graphs of both lakes showed the presence of the zooplankton. In Lake 1, it was dominated by the copepods while cladocerans dominated the Lake 2. The third graphs of both lakes showed the cladoceran percentage. The last graphs showed the ratio of zooplankton and phytoplankton and the chl a:TP (constant). 14. I had graphs about the relations between carp, vegetation and waterfowl. The second one was how chl-a, transparency and

phytoplankton change after filter feeding fish is introduced

15. My first graph was about three sections of river with different concentrations of periphyton, and shrimps as the model organism. So you have to tell what's is happening with the algae concentration in each section

16. And the second one about the concentration of zooplankton in dry and rainy season. I had two graphs showing concentrations of

rotifers and copepods through the year. Then you have to explain what is happening with the concentration of each one

17. Graphs with T Phosphorous concentrations, large and small

phytoplankton biomass, Secchi depth, Daphnia abundance over a month period. What happens in an experiment when a silver Carp (filter-feeding) is introduced and when is not present.

18. I had three graphs: change in Total zooplankton, large and small zooplankton densities over a year period in an east-asian river. Explain the dynamics in each group according to the rain and dry seasons

OLD EXAM:

River and lakes:

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1. Explaination of the differencies in feeding behaviour of

common carp among different macrophytes (submerged, submerged,

floating, emergent)

Girl question:

2. Comparison between two different lakes of zooplankton and

phytoplankton community. The two lakes show different pattern

in seasonal species and numbers of individuals in a normal

situation; explaination of what can determine this difference.

In a second experiment a fish-free enclosure is created in

both lakes using a net which does not allow the entrance of

the fishes. Compare the change in phytoplankton and

zooplankton community in both "open lakes" and "fish-free

Lake".

triest part:

1 graph with underwater vegetation cover in the X-axis and

chlorophyll A in the Y-axis and distribution of population of

cladocera of different sizes along the two variables;

1 graph with chlorophyll A in function of cladocera length

(without vegetation);

1 graph of chlorophyll A in function of population density

(without vegetation);

explain the patterns taking into account the food chain.

During the discussion he asked: what does the presence of big

cladocera tell you about the lake color? why do you have big

cladocera? what is their interest of being bigger? what are

they predators?

isabel george part:

several longitudinal profiles of a river after a input of

human waste:

1st: O2, BOD and sediments;

2nd: NH4, NO3, Ph(something)

3rd: bacteria, algae, protozoa and another one

4th: 3 different organism with different resistance to O2

concentration and "normal flora from the river"

You had to explain all the patterns, the relations between

them, how the system evolved, etc. In the end she also asked

me about some characteristics about the organisms that where

in the last profile.

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