Physics, Chemistry, and Biology in Ponds and Lakes

Transcription

1 Physics, Chemistry, and Biology in Ponds and Lakes

2 Ponds and Lakes Dominated by Heterotrophic Processes Example. A well mixed lake with V = 5x10 8 L is fed by a stream flowing at Q=2.4x10 7 L/d that contains 8mg/L DO and has L =10mg/L. Waste from a small municipality (L =95mg/L, DO = 0 mg/l) enters the lake at 4.8 x 10 6 L/d. k d, k r, and DO* in the lake are 0.10 d 1, 0.05 d 1, and 11.2 mg/l, respectively. Assuming that the lake is at steady state: a) Determine L and DO in the lake. b) Compute the rates (kg/d) at which advection, reaeration, and biological reaction, each acting alone, increase or decrease DO and L in the lake.

3 Q 1 (stream), L 1, DO 1 Q 2 (waste), L 2, DO 2 V, k d L in lake Q 3, L 3, DO 3 DO in lake, k r Q 1 = 2.4 x 10 7 L/d Q 3 = Q 1 + Q 2 = 2.88 x 10 7 L/d DO 1 = 8 mg/l DO 3 =? L 1 = 10 mg/l L 3 =? Q 2 = 4.8 x 10 6 L/d DO 2 = 0 mg/l L 2 = 95 mg/l k r = 0.05 d 1 k d = 0.10 d 1 DO* = 11.2 mg/l

4 Q 1 (stream), L 1, DO 1 Q 2 (waste), L 2, DO 2 V, k d L in lake Q 3, L 3, DO 3 DO in lake, k r MB on L: 0 = QL 1 1+ QL 2 2 QL 3 3 kvl d in lake L mg L mg = + d L d L x x10 95 L ( 0.10 d )( 5 10 L) d L x x L L 3 = L in lake = 8.83 mg/l

5 MB on DO: Q 1 (stream), L 1, DO 1 Q 2 (waste), L 2, DO 2 V, k d L in lake Q 3, L 3, DO 3 DO in lake, k r d dt ( DO ) = ( DO ) + ( DO ) ( DO ) ( ) + ( DO* DO ) V Q Q Q k L V k V in lake d in lake r in lake ( ) ( ) ( ) ( ) ( ) 0 = Q DO + Q DO Q DO k L V + k DO* DO V d 3 r 3 L mg L mg L = + d L d L d mg mg + L L DO 3 = DO in lake = 0.57 mg/l ( ) x x x10 DO ( 0.1 d ) 8.83 ( 5x10 L) ( 0.05 d ) 11.2 DO3 ( 5x10 L)

6 Q 1 (stream), L 1, DO 1 Q 2 (waste), L 2, DO 2 V, k d L in lake Q 3, L 3, DO 3 DO in lake, k r Advective outflow of biochemical oxygen demand: (2.88 x 10 7 L/d)(8.83 mg/l) (10 6 kg/mg) = 254 kg/d Rate of L utilization (i.e., the rate of DO utilization by biochemical reactions): r L V = k d (L in lake ) V = (0.10 d 1 ) (8.83 mg/l) (5 x 10 8 L) = 4.42 x 10 8 mg/d = 442 kg/d

7 240 Stream (a) Lake 442 Bioactivity 254 Outlet (b) 192 Stream 266 Reaeration Lake 442 Bioactivity 16 Outlet 456 Waste 0 Waste Mass Balance Terms for L (kg/d) Mass Balance Terms for DO (kg/d)

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11 Cladocerans

12 Copepods Cyclopoid Calanoid nauplii

13 Limiting Nutrients for Algal Growth and Lake Productivity: Nitrogen, Phosphorus & Carbon Nutrient Source Cycling Nitrogen [Atmosphere], Biological Geologic Phosphorus Geologic Physical, Chemical Carbon Atmosphere Chemical, Biological Redfield Ratio C: N : P P limited N limited 106 : 16: 1 N:P >20 N:P < 10

14 Carbon: rarely limiting due to ready availability from the atmosphere Nitrogen: can be limiting especially at very high phosphorus loading rates Phosphorus: most common limiting nutrient and best predictor of algal biomass Colimitation: very common for both nitrogen and phosphorus in combination to be limiting in short term (3-5 day) bioassays

15 Chlorophyll(µg L -1 ) Phosphorus vs. Phytoplankton Biomass y = 0.08x 1.5 r 2 = Total Phosphorus (µg L -1 ) Jones and Bachmann (1976)

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17 Common Threats to Lake and Stream Water Quality Point Sources: sewage and industrial effluent Non-Point Sources: fertilizers, animal wastes, erosion, failing septic systems, Canada geese Point sources have for the most part been controlled A key area for future research in limnology and lake management is the development of methods for quantifying and controlling non-point source nutrients

18 CAFOs = Factory Farms

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20 The Impact of Temperature on Water Density Density (grams/cm 3 ) Max. 4 C Temperature (C )

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22 Summer Stratification 0 5 Epilimnion Depth (m) Metalimnion Hypolimnion Temperature (C )

23 Depth (m) Time of Year Temperature ( C)

24 Temperate Lakes Deep = usually Dimictic Shallow = often Polymictic

25 Thermal Stratification in a Dimictic Lake 0 Summer Stratification 0 Fall Mixing 5 5 Depth (m) Depth (m) Temperature (C ) Temperature (C ) Winter Inverse Stratification 0 0 Spring Mixing 5 5 Depth (m) Depth (m) Temperature (C ) Temperature (C )

26 A Eutrophic Dimictic Lake During the Summer 0 Temperature 0 Light 5 5 Depth (m) Depth (m) Dissolved Oxygen 0 Nutrients 5 5 Depth (m) Depth (m)

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28 Eutrophication and Nuisance algal blooms

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30 Chlorophyll vs. Water Clarity 8 Secchi depth (m) Chlorophyll a (µg L 1 )

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33 0 10 Depth (m) Time of Year Chlorophyll concentration (µg/l)

34 7 6 Vol. Wt. Chlorophyll Conc. (µg/l) Lake Washington Temperature Chlorophyll Time of Year Vol. Wt. Temperaure ( C)

35 Aquatic foodweb top consumers planktivores zooplankton phytoplankton

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37 Fish Zooplankton Phytoplankton Clear Lake Peruvian Upwelling

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39 The phytoplankton-zooplankton interrelationship appears to be particularly dependent on the species composition of the biota; hence, if the phytoplankton is composed primarily of species edible [and of nutritional value] for zooplankton, one may find a relatively low phytoplankton standing crop R.A. Vollenweider (1976) Mem. Ist. Ital. Idrobiol. 33:

40 Hypereutrophy and N limitation Anoxic hypolimnion (bottom layer) Denitrification (NO 3 converted to N 2 ) Reduced conditions in sediments (Fe 3+ Fe 2+ ) Supply of NO 3 and PO 4 3-

41 Cyanobacteria Competitive Advantages Can fix atmospheric nitrogen Buoyancy regulation Luxury P uptake (polyphosphate crystals) Poor food quality and edibility to zooplankton Competitive Disadvantages Slow growers relative to other phytoplankton

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44 "On May 2, 1878, George Francis of Adelaide, Australia, published the first scholarly description of the potentially lethal effects produced by cyanobacteria... in a letter to Nature... Symptoms--stupor and unconsciousness, falling and remaining quiet, as if asleep, unless touched, when convulsions come on, with head and neck drawn back by rigid spasm, which subsides before death. Time--sheep, from one to six or eight hours; horses, eight to twenty-four hours; dogs, four to five hours; pigs, three or four hours."

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47 From the website for CellTech, the company harvesting and selling Super Blue Green Algae. 1. Super Blue Green Algae is over 60% high quality (complete) protein 2. and is the richest source of chlorophyll known to man. 3. It is a (vegetable) source of vitamin B-12, and in fact contains more B-12 than any other vegetable! 4. Super Blue Green Algae is 100% vegetarian, 100% natural and 100% wildgrown. 5. It is enzyme active for super absorption by your body and, it contains over 60 minerals and trace minerals. 6. Are there any medically proven health benefits? Super Blue Green is a food, not a drug or medicine. Therefore, we cannot promote it as having proven health consequences.

48 Mean depth 32 m Max depth 61 m HRT = 2.4 yr -1 Lake Washington Story

49 Case Study: Lake Washington Dissolved P Inputs (metric tons yr. -1 ) Sewage Effluent Watershed Loading Year From: W.T. Edmondson (1994) Lake & Reservoir Management 10:

50 Change in Lake Washington phytoplankton composition and biomass Phyto. Bioviol. (mm 3 L -1 ) Cyanobacteria Other Phytoplankton Year From: W.T. Edmondson (1994) Lake & Reservoir Management 10:

51 Change in Lake Washington nutrient concentrations, and phytoplankton biomass after waste water diversion 125 Percent of 1964 Value Inorganic Carbon Nitrate Phosphate Phytoplankton Year From: W.T. Edmondson (1991) The Uses of Ecology.

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53 Secchi (m) Daphnia Trophic Equilibrium Daphnia L -1 8 Secchi Depth Year

54 Secchi (m) Daphnia Trophic Equilibrium Daphnia L -1 8 Secchi Depth Year

55 Secchi (m) Daphnia Trophic Equilibrium Daphnia L -1 8 Secchi Depth Year

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57 10 Lake Washington seasonal phytoplankton succession Diatoms Biomass (µg Chla/l) Cryptos Greens Cyanos Others Time of Year