Oceanography 320 Mid-term Examination 03/07/02

Transcription

1 Oceanography 320 Mid-term Examination 03/07/02 Name Social Security Number 1) Conversion of solar energy into chemical energy constitutes a) photosynthesis b) primary production c) respiration d) a and b e) a and c f) b and c g) a, b, and c 2) The natural eutrophication process is associated with which of the following conditions a) the production of organic matter exceeds the loss of organic matter via respiration b) the loss of organic matter via respiration exceeds the production of organic matter c) the loss of organic matter via excretion exceeds the production of organic matter d) all of the above e) none of the above 3) A nutrient-poor lake may be referred to as a) phytotrophic b) oligotrophic c) mesotrophic d) eutrophic e) hypotrophic 4) The ecological efficiency in a food chain is 20%. The concentrations of pollutant X on trophic levels 2 and 5 are 20 ppm and 160 ppm, respectively. If the increase in concentration of pollutant X between trophic levels 2 and 5 is due entirely to food chain magnification, with what efficiency is X transferred from one trophic level to the next higher trophic level? Wastewater with a N/P ratio of 4 is being discharged into a lake. The N:P ratio of the algae in the lake is 16. The wastewater is the only significant source of nutrients for the lake. 1

2 5) What will happen to the algae in the lake if the N in the wastewater is reduced by a factor of 12? a) Reduced by a factor of 12 b) Reduced by a factor of 4 c) Reduced by a factor of 3 d) No change 6) What will happen to the algae in the lake if the P in the wastewater is reduced by a factor of 12? a) Reduced by a factor of 12 b) Reduced by a factor of 4 c) Reduced by a factor of 3 d) No change 7) What will happen to the algae in the lake if the N in the wastewater is increased by a factor of 12? a) Increased by a factor of 12 b) Increased by a factor of 4 c) Increased by a factor of 3 d) No change 8) What will happen to the algae in the lake if the P in the wastewater is increased by a factor of 12? a) Increased by a factor of 12 b) Increased by a factor of 4 c) Increased by a factor of 3 d) No change 9) The aphotic zone a) Is located above the euphotic zone b) Is a part of the water column where production is nutrient limited c) Has insufficient light to support photosynthesis d) Is associated with a high rate of primary production e) All of the above f) None of the above 10) Aquatic pollution can a) Reduce the depth of the euphotic zone b) Increase water turbidity c) Decrease net community production d) All of the above e) None of the above 2

3 11) Studies have shown that the nutrients most commonly limiting photosynthesis in aquatic systems are a) molybdenum and iron b) nitrogen and carbon dioxide c) phosphorus and iron d) nitrogen and phosphorus 12) Precipitation of phosphate and nitrogen fixation are much more important processes in lakes than in most parts of the ocean. What single factor accounts for both of these facts? a) the average depth of the ocean is much greater than the depth of any lake b) the residence time of bottom water in the ocean is much longer than the residence time of bottom water in a typical lake c) most of the volume of the ocean lies below the base of the euphotic zone d) the concentration of iron is much lower in the ocean than in most lakes e) the mixed layer in the ocean rarely extends to the bottom 13) In temperate latitude aquatic systems, primary production in the mixed layer is low during the winter because a) the critical depth is shallower than the mixed layer b) the mixed layer is shallower than the critical depth c) the mixed layer is shallower than the euphotic zone d) the euphotic zone is shallower than the critical depth 14) Explain why the development of anoxic conditions in the bottom waters of Lake Erie has frustrated attempts to reduce phosphorus loading to the lake. 15) Seasonal anoxia was a serious problem in the central basin of Lake Erie for many years. How would you account for the fact that seasonal anoxia was never a problem in Lake Washington, although phosphorus concentrations in Lake Washington just prior to diversion of sewage discharges from the lake in the 1960s were about four times higher than the phosphorus concentrations in Lake Erie at the peak of eutrophication? 16) The graph on the next page shows concentrations of nitrate and phosphate from late winter until early summer in a lake. The straight line is a linear regression fit to the data. The concentrations of both nutrients are high at the end of the winter and low by the beginning of summer. The drawdown of both nutrients is due to uptake by phytoplankton. Based on the pattern of nitrate and phosphate concentrations, which nutrient would you judge to be limiting phytoplankton biomass in the lake? Explain your reasoning. 3

4 Nitrate (µm) Phosphate (µm) 17) City A is located in a place where there is a rainfall event every week. City B is located in a place where there is a rainfall event every month. In which city is the first flush effect likely to be more important and why? 18) The two most serious water quality problems associated with land runoff are a) heavy metals and BOD b) nutrients and heavy metals c) suspended solids and nutrients d) BOD and suspended solids 19) Why would construction of a sedimentation basin on the Manoa-Palolo drainage canal reduce the overall costs of removing sediment from the Ala Wai Canal, i.e., why not just remove the sediment after it gets into the Ala Wai Canal? 20) Federal law requires that primary sewage treatment plants remove at least 30% of the BOD and 30% of the suspended solids from the raw wastewater. Why do you suppose primary treatment plants have had a more difficult time meeting the requirement for 30% BOD removal? 21) The principal mechanisms used to remove nitrogen from wastewater are ammonia stripping and denitrification. Which one of these two methods is more likely to lead to eutrophication problems caused by high concentrations of inorganic nitrogen in rainwater? Explain your reasoning. 22) How would you account for the fact that only about 2% of the wastewater produced in the United States is recycled for irrigation purposes, but 36% of municipal sewage sludge is applied 4

5 to the land as a soil conditioner? 23) The rationale for stream hardening, i.e., channelizing natural streams, is e) to reduce habitat for mosquitoes and other insects f) to control floods g) to distribute water to agricultural areas h) to control sediment pollution i) to provide a benign environment for aquatic wildlife 24) A friend of yours goes swimming in a lake. About a week later he develops an annoying case of dermatitis. Which of the following pathogens might be the cause of the dermatitis? a) Naegleria and Leptospira b) Cryptosporidium and Giardia c) E. coli and Campylobacter d) Pseudomonas and Schistosoma 25) You and a friend go hiking up a stream. Your friend cuts his hand on some sharp rocks. He washes the cut in the stream before applying a Band-Aid. Several weeks later your friend comes down with a serious infection of his kidney and liver. What organism is the likely cause of his illness? 26) The State of Hawaii Department of Health (DOH) monitors recreational waters to ensure that they are safe for water contact. The principal concern from a public health standpoint is the presence of pathogens derived from human excrement. Why is it that the DOH does not directly determine whether such pathogens are present or absent, but instead monitors for the presence of so-called indicator organisms, which are not themselves pathogens? 27) Which one of the following statements is true? a) Trickling filter plants achieve higher SS and BOD removal than activated sludge plants b) Activated sludge plants produce less secondary sludge than trickling filter plants c) Trickling filter s biological communities are less affected by sudden changes in the character of the sewage d) Activated sludge process is less expensive to operate than trickling filters and may 5

6 be preferred when the wastewater is primarily domestic 28) The most cost effective way to remove phosphorus in tertiary sewage treatment is a) reverse osmosis b) ion exchange c) distillation d) chemical precipitation e) air stripping 29) Assuming that the interaction between two toxic substances is strictly additive will cause one to underestimate the toxicity of a mixture of the two substances if a) there is no interaction between the toxic substances b) the interaction is antagonistic c) the interaction is infra-additive d) the interaction is supra-additive e) none of the above 30) Complete the following table by calculating the number of chronic toxicity units for toxic substances A, B, C, and D. Toxic substance Concentration in water 96-hr TLm Acute/chronic ratio Chronic toxicity units A B C D ) Assume that we discover that the water in question 43 is exerting a chronic stress on aquatic species W. Which of the following may be true (more than one answer may be correct)? a) The interaction between A, B, C, and D is antagonistic. b) There is no interaction between A, B, C, and D c) The interaction between A, B, C, and D is infra-additive d) The interaction between A, B, C, and D is strictly additive e) The interaction between A, B, C, and D is supra-additive 32) Assume that we discover that the water in question 43 is not exerting a chronic stress on aquatic species W. Which of the following may be true (more than one answer may be correct)? a) The interaction between A, B, C, and D is antagonistic. b) There is no interaction between A, B, C, and D c) The interaction between A, B, C, and D is infra-additive d) The interaction between A, B, C, and D is strictly additive 6

7 e) The interaction between A, B, C, and D is supra-additive 33) In country Hambriento Para el Pez, people eat an average of 100 grams of fish and shellfish per day. Water quality criteria in that country specify that for surface waters used as sources of drinking water, the maximum permissible concentration C of a noncarcinogenic toxic substance should be calculated from the expression C = ADI/( R) where ADI is the acceptable daily intake of the substance and R is the average biological concentration factor for fish/shellfish taken from the given surface water. The calculation assumes that people drink 2 liters (2 kilograms) of the water and eat kilograms (100 grams) of fish and shellfish daily from the same body of water. If the biological concentration factor for toxic substance X is 980 and the ADI is 40 micrograms per day, what is the maximum allowable concentration of X in the water? 34) The graph on the next page shows the concentration of pollutant X versus median survival time of a certain species of fish. Judging from this graph, what would you estimate the incipient lethal level of pollutant X to be for this species of fish? 7

8 1500 Median survival time (minutes) Concentration of X (ppm) 35) The graph on the next page shows the concentration of pollutant X versus percent survival of a species of fish after 96 hours of exposure to X. Judging from the figure, what would you estimate to be the 96-hour TLm in this case? 8

9 Percent survival Concentration of X (ppm) 9