1. LAKE ECOLOGY Unit 1: Module 2/3 Part 4 – Spatial and Temporal variability January 2004

2. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s2 Modules 2/3 overview  Goal – Provide a practical introduction to limnology  Time required – Two weeks of lecture (6 lectures) and 2 laboratories  Extensions – Additional material could be used to expand to 3 weeks. We realize that there are far more slides than can possibly be used in two weeks and some topics are covered in more depth than others. Teachers are expected to view them all and use what best suits their purposes.

3. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s3 Modules 2/3 outline 1. Introduction 2. Major groups of organisms; metabolism 3. Basins and morphometry 4. Spatial and temporal variability – basic physical and chemical patchiness (habitats) 5. Major ions and nutrients 6. Management – eutrophication and water quality

4. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s4 4. Spatial & temporal variability – basic physical and chemical patchiness (habitats)

5. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s5 4. Spatial & temporal variability – basic physical and chemical patchiness (habitats)  Physical structure – morphometric features  Physical properties – vertical patterns of light, temperature and density  Density stratification effects on chemistry  O2  pH, EC25 (specific conductivity/salinity)  nutrients (in section 5)

6. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s6 The size and shape of the lake matter  Shoreline development  Habitat  Aquatic plants  Water movement  Erosion potential  Privacy for people  Here’s 40 acre Ice Lake compared to 14,500 acre Lake Minnetonka

7. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s7 Lakes: spatial variability 1  How might water quality vary between site 1 and site 2?  How might their aquatic organism communities differ?  Fish  Zooplankton  Algae  Plants

8. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s8 Lakes: spatial variability 2  How might water quality vary between sites 1, 2 and 3?  How might aquatic organism communities differ? Fish ZooplanktonAlgaePlants

9. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s9  How might water quality vary across this lake?  How might aquatic communities differ?  Fish  Zooplankton  Algae  Plants Minnesota or Wisconsin bass-bluegill lake Lakes: spatial variability 3

10. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s10 Lakes: spatial variability 4 Here’s a western US reality check What are major sources of variation for this system ? Water Quality Fish Zooplankton Algae Plants California bass-bluegill lake Z-max ~ 4 m Area ~ 10 acres Watershed - ?? (urban runoff) Wind & water flow – westerly

11. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s11 Riverlake, Sacramento, CA  Price: $798,000 (Sep ’03)  Sq Ft: 3511  Year Built: 1990  Bedrooms: 4 “…Just minutes from downtown, you'll feel like you are living at a resort in the city! Dynamic architecture brings the lake view to all major rooms”. … an upscale community … commenced development in 1987… Currently, it consists of 11 villages comprising approximately 1,000 home sites (incl. 150 lake front lots),…

12. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s12  Persistent seasonal and short-term longshore currents in Lake Superior  Upwelling and downwelling regions  Sediment transport from shoreline erosion and deepwater resuspension  Where do you sample ? How might water quality and aquatic communities vary spatially and temporally ?  Where do stormwater and sewage overflows from Duluth go ? Duluth Horizontal variations from physical factors

13. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s13 Water movements- currents and waves  Waves consist of the rise and fall of water particles, with some oscillation but no net flow  Currents consist of net unidirectional flows of water credit: www.aquatic.uoguelph.ca/lakes/waves

14. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s14 Surface waves  Surface waves are wind-driven. Regular patterns of smooth, rounded waves are called swells.  Capillary waves have wavelengths less than 6 cm and are restored to equilibrium due to the surface tension of the water  Gravity waves have wavelengths greater than 6 cm and fall due to the force of gravity

15. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s15 Resuspension important particularily in shallow lakes but also in deep lakes Resuspension of nutrients and sediments

16. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s16  Generated by steady wind  Surface water driven downward  Water piles up on the lee shore  Water flows back due to gravity  Standing wave rocks back and forth with decreasing motion = "surface seiches"  Sloshes at resonant frequencies based on basin shape  Can also result from landslides, air pressure, and earthquakes Standing waves - surface seiches

17. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s17 Standing waves - surface seiches cont.

18. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s18 www.northernimages.com St. Louis River – Lake Superior seiches  The St. Louis River enters western L. Superior at the Duluth Aerial Lift Bridge  The site is influenced not only by river water flowing downstream but also occasionally by Lake Superior water flowing upstream due to the lake's seiche

19. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s19 St. Louis River – Duluth inlet data  Brown stripes are periods when water flows out into the lake  Blue indicates “negative” velocity when the lake is sloshing back into the bay  Which water body has higher EC ?  What factors influence the turbidity plot ?

20. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s20 Horizontal & vertical variability How do light, temperature, sediments vary across these zones ? How do plants, periphyton, invertebrates, fish and algae vary ? LITTORAL ZONELIMNETIC ZONE Major Lake Zones

21. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s21  Littoral zone – usually shallow, nearshore region where sufficient light can penetrate to the bottom for plants to grow (~ 1% of midday surface light intensity)  Often estimated as that area of the lake’s surface either <10 ft (3m) or <15 ft (~5 m) deep  Where the majority of aquatic plants are found; a primary habitat for young fish NRRI image Littoral Zone

22. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s22 A "natural" shoreline An altered shoreline WI DNR Shorelines

23. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s23 Can you explain each seasonal pattern ? What might cause the mid-summer nutrient spikes ? Is this likely to be a stratified or unstratified lake and why ? Secchi depth Nutrients N or P Bottom water- O 2 winterspring summer fall winter Temporal variations - seasonality

24. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s24 Lake Ecology Module – light, temp, density, O 2  The following slides represent the temperature, density, dissolved oxygen, and stratification portion of the Lake Ecology introductory lecture module 3+4, subtopic 4  Additional explanatory information is available by viewing the attached Notes for each slide

25. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s25 Density, Thermal and Oxygen Stratification  Temperature and oxygen levels are major factors regulating aquatic organisms  The layering of lake waters due to density differences is a major factor structuring the ecosystem and creating distinct habitats  The seasonal pattern of turbulent mixing is also a critical determinant of ecosystem function and community structure

26. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s26 A Review of Some Basic H 2 O Physics DENSITY  The warmer the water, the better it floats, but ice floats too  Water becomes less dense as it warms  The difference in density per degree of warming increases as temperatures rise SO ….

27. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s27 Density layering Surface water is very buoyant because of the big density difference between it and cold bottom water (leading to stable thermal stratification) Bottom water is colder than the surface in summer (and a bit warmer in winter)

28. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s28 Gas Solubility Temp (o C) Temp (o F) O2- Sol (mg/L) 03215 54113 105011 155910 20689 25778 Warmer water holds less gas (warm beer goes flat) As 100% air-saturated water warms, it loses O 2

29. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s29 Depth Light x x x x Plotting profiles - light

30. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s30 Heat and Light  Light intensity decreases exponentially with depth in a lake  Which curve is the clear lake – blue or black ?  What shape would you expect for the profile of temperature ?

31. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s31 Vertical light extinction Light intensity decreases exponentially with depth and is well described by the Beer- Bouguer-Lambert Law which states that: I(z) = I( 0 ) * [ e -kz ] Where: I(z) = intensity of light as a function of depth z I(0) = intensity of light at the surface (0 m) k = the vertical extinction or attenuation coefficient.

32. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s32 The lake surface is exposed to the wind, which mixes the surface water, but the turbulent energy from the wind dissipates with depth, having less impact further down. The greater the density difference (mostly from temperature) between layers of water, the harder it is to mix them together. Heat, as indicated by temperature would also be expected to decrease exponentially with depth, BUT …. Wind: turbulent mixing

33. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s33 Wind mixing links Also see slides in Section 5 (Water Chemistry) of this module that discuss gases (O 2, N 2,CO 2 and H 2 S)

34. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s34 Depth Temperature x x x x The Temperature profile would look just like the light profile – at least on a perfectly calm day Temperature – calm day

35. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s35 Depth Temperature x x x x But when the wind blows, it mixes the surface water with deeper water And its energy dissipates with depth x x Temperature – windy day

36. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s36 Depth Temperature 0oC0oC

37. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s37 Depth Temperature 0oC0oC

38. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s38 Depth Temperature 0oC0oC

39. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s39 Depth Temperature 0oC0oC 10 o C

40. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s40 Depth Temperature 0oC0oC 10 o C

41. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s41 Depth Temperature 0oC0oC 10 o C20 o C

42. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s42  Bottom water colder than surface in summer  Surface water is very buoyant  BIG density difference between surface and cold bottom water = resistance to mixing Mid-summer thermal stratification

43. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s43 Depth Temperature 0oC0oC 10 o C

44. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s44 Depth Temperature 0oC0oC 10 o C

45. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s45 Depth Temperature 0oC0oC Fall Turnover

46. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s46 Depth Temperature 0oC0oC

47. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s47 Thermal stratification sequences Ice Lake, MN Apr 23 – Jun 3, 2003 Shagawa Lake, MN May 7 – Jun 24, 2003 Lake Independence, MN Apr 12 – Jun 29, 1999 Temperature ( o C) time

48. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s48 Oxygen  What are the sources of oxygen to a lake?  What are the sinks for oxygen in a lake?

49. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s49 Wind energy Photosynthesis Two Major Sources of O 2

50. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s50 Major Sinks (losses) O2O2 O2O2 O2O2 Diffusion Water column respiration Sediment respiration (bacteria and benthos)

51. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s51 Factors affecting dissolved oxygen levels How far down can light penetrate ? Is the lake thermally stratified ? How windy is it ? Are there a lot of aquatic plants and algae ? How warm is the lake ? Is there a lot of organic “gunk” in the water ? Are there sources of fertilizer, ag & urban runoff, wastewater, etc. coming in ? How much organic sediment area is there relative to hypolimnetic volume ?

52. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s52 “Idealized” Stratification Curves Unproductive Productive

53. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s53 Mid-summer thermal stratification - summary  Surface water is very buoyant – it floats on top of the thermocline  BIG density difference between surface and cold bottom water  It takes a lot of wind energy to push the surface water down long enough to mix with the water below Bottom water is colder than the surface in summer

54. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s54 Annual cycle of thermal stratification - dimixis

55. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s55  Illustrations of Water on the Web lake data visualization tools (DVT’s):  Profile plotter (all parameters vs depth)  Color mapper (2 parameters vs depth)  DxT (depth vs time) Reality – “real” data

56. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s56 Profile Plotter  West Upper Bay of Lake Minnetonka  8/31/2000 Temperature Thermocline Dissolved oxygen Scales: o C and ppm O 2 Strong temperature and DO stratification No O 2 below thermocline

57. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s57 Color MapperBackground Scale DO Temp Line plot Scale Anoxic below thermocline

58. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s58 Color Mapper - Shallow Lake DO Temp

59. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s59 Seasonal Cycles of Temperature & Oxygen

60. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s60 Partial Mixing in Medicine Lake, MN Temp DO 8/31/2001 Is it totally mixed ?

61. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s61 Interpreting profiles – Ice Lake #1 Questions 1.Time of year ? 2.Explain profiles Temp DO pH Temp pH DO

62. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s62 Interpreting profiles – Ice Lake #2 Questions 1.Time of year ? 2.Explain profiles Temp DO pH Temp pH DO

63. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s63 Seasonal Cycles in Ice Lake, MN (Profile Plotter) Temp pH DO Here’s the full annual cycle on a monthly time step

64. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s64 Seasonal Cycles in Ice Lake, MN (Color Mapper)

65. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s65 Interesting Summer O 2 Depth Profiles Ice LakeGrindstone Lake 6/14/996/20/99

66. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s66 Compare with Three Nearby Lakes (June 1999) Q1: Why is West Upper temperature so different? Q2: What caused the strange West Upper O 2 profile? Halsted’s Bay, MinnetonkaWest Upper, L. M’tonkaL. Independence

67. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s67 Onondaga midsummer – color mapper Set the color mapper for mid Aug 2003 (this profile is from Aug 22, 2003. Set EC to 1200- 2200 uS/cm (in red), DO to % sat (black) and pH in blue DO > 150% from 0-3m and then <10% down to the bottom ! pH drops >1 unit from 3 down to 5 m EC jumps up and down by 400 uS/cm ! Very dynamic data set

68. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s68 Depth versus Time Plotter (DxT) Time of YearLocationParameter Scale Depth

69. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s69 Annual Temp & O 2 in a Shallow, Productive Bay – Halsteds Bay, L. Minnetonka Temp O 2

70. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s70 Compare two bays of the same lake Halsteds and West Upper, Minnetonka, MN Halsteds West Upper

71. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s71 Medicine Lake - summer stratification

72. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s72 Ice Lake, MN - Interannual variation Fall mixing Fall mixing ? Fall mixing spring mixing rate of thermocline descent No spring mixing “rate of hypolimnetic O 2 –depletion”

73. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s73 Ice Lake, MN: 1998-2003 Complete Mixing Spring: No-98,99,01 Yes- 00,02,03 Fall: No-00 ?? Yes- 98,99,01,02

74. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s74 DO-Temperature squeeze on fish  Thermal stratification can be a challenge for coldwater & coolwater fish  Too little DO where the temperature is optimal  How would a warm water discharge from a new power plant affect the fish community ?  How would global climate change affect the fish ?

75. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s75 Case study of density layering - reservoirs  The influent water “seeks” its own density (and destiny)  Balance of temperature, dissolved salts and silt load  Varies seasonally  See movies in the WOW Lake Ecology Primer showing aquarium lake models at http://wow.nrri.umn.edu/wow/under/ primer/page5.html Schematic from NALMS. 1990. The lake and reservoir restoration guidance manual. 2 nd edition. North American Lake Management Society and USEPA Office of Water, Washington, D.C. EPA-440/4-90-006 August 1990.

76. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s76 USBR: http://www.hooverdam.usbr.gov/ Lake Mead, NV-AZ, USA

77. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s77  Mainstem Colorado R.  Lifeblood of SW US  Largest reservoir in US  National Recreation Area  A: 158,000 acres  V: ~ 21-26 million acre-feet  z-max: ~ 150 m (main basins)  z- max ~ 2-55 m (LV Bay ) power for 500,000 homes (2,074,000 kilowatts) drinking water ~20 million irrigation ~1 million acres wastewater ~ 153 mgd oligotrophic - main basins eutrophic Las Vegas Bay municipal sewage density plumes can combine wastewater & drinking water Lake Mead, NV-AZ, USA - features

78. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s78 DW intake Las Vegas Bay Boulder Basin- Sentinel I. Hoover Dam Lake Mead, Las Vegas Bay – images

79. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s79 Lake Mead – Boulder Basin images Inner LV Bay LV Bay Sentinel I. Effluent Inflow About 120 million gallons of treated wastewater flows into the inner Las Vegas Bay each day

80. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s80 April 1996 Density due to temperature vs salt load from sewage controls where the plume goes EC TEMP DO pH DEPTH (m) Bottom scale: miles from LV Wash inlet Salinity (EC25) overrides temp and the water mass sinks as it moves into bay This is the approximate location of the Saddle I. drinking water intake Warm over cool Graphs from LaBounty, J.F. and M.J.Horn. 1997.

81. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s81 Density plumes – Outer Vegas Bay, L. Mead AZ pH DO EC TEMP DEPTH These graphs show how LV Bay water moves into the main lake in Boulder Basin Drinking Water intake Hoover Dam– 10 miles out Low salinity, narrow stratum of water is the “remains” of the Colorado River flowing down lake for over 70 miles High salinity (EC25), low DO plume from wastewater Graphs from LaBounty, J.F. and M.J.Horn. 1997.

82. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s82 Lake Mead – Las Vegas Bay RUSS DxT data Data from ~ mid Bay for April – August 2003 T DO EC pH Explain the pattern for each parameter

83. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s83 Lake Mead – Las Vegas Bay DxT scaling An example of how playing with the scale adjustment on the DxT tool can highlight the behavior of a stratum of water

84. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s84 Lake Onondaga – also has a density layer Corresponding DO (% saturation) South Deep site DxT: start 6/21/03 for 85 d What’s causing the high salinity layer that is ~ 10 m thick ?

85. Developed by: R.Axler and C. Hagley Draft Updated: January 14, 2004 U1-m2/3Part 4-s85