Exam – 8:00-10:00 AM, Friday 15 December; 212 Marshall Hall

Let me know ASAP if you have a conflict with this time; alternate exam is Monday, 11 December 10:00-noon in 127 Illick

Format:

Extra Office Hours:
Schulz (456 Illick):
   

Mon 8:30-9:30 AM, 1-2 PM, Tues 4-5 PM, Thurs 3-4 PM                 

            Or email with questions. I will check at least daily.

                        Can perform nitrogen fixation

                        Require large amounts of Si to build new cells

                        Chemical factors called morphogens have been found to induce
                                    developmental  polymorphisms in these animals.

                        These animals are important components of benthos in streams.

                        These animals only reproduce asexually

Essays

1. Describe two reasons why attempts at top down control of food webs often fail (3 points).

2. Lake Mjosa is the largest lake in Norway at 449 m deep and 117 km long.  The mountains around the lake contain many glaciers, and the inflow of glacial melt waters replaces 1/6^th of the volume of the lake each year.  From 1950 to 1976 the algal biomass increased and cyanophyta became common.  This condition deprived nearly 200,000 people who lived near the lake their drinking water supply (0.5 points per short answer; others as marked; 8 points total)

(a)    Lake Mjosa was probably experiencing increased loading of the chemical element                                 .

(b)   What was probably responsible for this increase? (1 point)

(c)    The river water flowing into Mjosa from natural areas (like glaciers) was probably richer / poorer / about the same in dissolved nutrients as was the lake itself in 1976.

(d)   Secchi disk transparency in Lake Mjosa increased / decreased / stayed the same from 1950 to 1976, and late-summer hypolimnetic oxygen concentrations increased / decreased / stayed the same.

(e)    What course of action would you recommend to the Norwegian government to alleviate these problems? (2 points)

(f)     What features of Lake Mjosa and its basin make it more or less likely that the nuisance conditions are reversible and would affect the time of recovery? (3 points)

FINAL PRACTICE QUESTION ANSWERS
 

Short answer

1. Top down control of food webs predicts that if nutrients / piscivorous fish / lake volumes are increased, then the amount of phytoplankton / zooplankton / water level will be decreased. 

2. Acid rain has especially large effects in lakes with high / low alkalinity, and lakes that are affected by acid rain often have increased / decreased levels of colored DOC.  Recently, regulations have caused large decreases in the amount of NO₃^- / SO₄^2- that is being deposited on the Northeastern region of the United States, and this may help to alleviate acidic conditions in many Adirondack lakes.

 
Matching (you will have a few extra potential answers, but there is only one correct answer per question)

a. Bdelloid rotifers
b. Calanoida
c. Plecoptera
d. Anabaena
e. Daphnia
f. Mysis
g. Asterionella
h. Dinoflagellates

d      Can perform nitrogen fixation
g      Require large amounts of Si to build new cells
e      Chemical factors called morphogens have been found to induce
               developmental  polymorphisms in these animals.
c      These animals are important components of benthos in streams.
a      These animals only reproduce asexually
 

Essays

1. Describe two reasons why attempts at top down control of food webs often fail (3 points).

Some examples include:

• Ontogeny -- often piscivorous fish are planktivorous when young, and will eat large zooplankton, thus decreasing the amount of zooplankton grazing and decreasing water clarity
• Predator-Prey cycles -- due to natural predator/prey cycles there are periodic releases from top-down predation and decreases in the amount of top-down control
• Replacement of species -- (rearrangement of trophic structure)
• smaller zooplankton may become abundant, and they don't generally reduce phytoplankton standing stock
• during eutrophication there are frequently shifts to inedible algae (such as blue-green algae), and these resist top-down control
• Variability in predator diet; plasticity in feeding

(a) Lake Mjosa was probably experiencing increased loading of the chemical element  phosphorus  .
(b) What was probably responsible for this increase? (1 point)

Increased population and sewage (or detergents) that increased the nutrients

(c) The river water flowing into Mjosa from natural areas (like glaciers) was probably richer / poorer / about the same in dissolved nutrients as was the lake itself in 1976.

(d) Secchi disk transparency in Lake Mjosa increased / decreased / stayed the same from 1950 to 1976, and late-summer hypolimnetic oxygen concentrations increased / decreased / stayed the same.

(e) What course of action would you recommend to the Norwegian government to alleviate these problems? (2 points)
 

• Treat the sewage to reduce nutrients (especially phosphorus) or reroute the sewage out of the lake
• Reduce phosphorus inputs from detergents and/or fertilizers

    Any two OK

• Rapid turnover rate
• Deep (big hypolimnion -- won't go anoxic quickly)
• Glacial (pure water input)

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