River and Lake Ecology
Ludwig Triest and Iris Stiers1. 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
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.
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