Lake Productivity and Water Quality

1. Lake Productivity and Water Quality

2. Problem Statement • What are the various factors affecting the water quality and productivity of our lakes?

3. Learning Objectives • List and describe the various types of water bodies in Minnesota. • List and describe the elements that affect lake productivity and water quality. • List and describe the productivity zones of a lake. • List and describe the productivity categories of a lake. • List and describe the thermal stratification levels of a lake. • List and describe the stages of seasonal lake turnover.

4. K.Q.#1: What are the various types of water bodies in MN?

5. Swamps • Woody Vegetation Within

6. Marshes • Emergent Vegetation Throughout Basin

7. Ponds • Rooted Vegetation at all depth in basin

8. Lakes • Basin too deep to support rooted vegetation throughout

9. K.Q.#2: What elements affect the productivity of a lake?

10. A: Parent materials, organic matter in a watershed. • Northeast MN. very rocky, granite. Will not breakdown easily to help form organic matter/ humus. • Rest of MN parent material is sedimentary parent material, which has broken down more easily and contributed to the formation of organic matter/ humus.

11. B: Type of bottom • Rocky • Sandy • Mud and Sand • Muddy • % of mud bottom likely indicates shallower, more productive lakes, but of course lower water quality for recreation and purifying.

12. C: Contour of the basin • Steep, Sharp angled bottom • Gently sloping land • The flatter the grade (slope) of a basin, the higher the potential for lake productivity.

13. Contour Continued • Which one has more productivity potential? • (A) Right? Why?

14. D: Size of the water Body • Larger water volumes distributes nutrients more widely and makes nutrients less available for the amount of energy needed to obtain the nutrients and phosphorous.

15. E: Depth of the water body (Basin) • Thermal stratification changes the productivity of a lake through nutrient cycling (turnover).

16. F: Shape of the lake • Irregular shoreline (many bays, ect.) • Circular shape lake (few bays) • Is Dead or Big Pine lake more productive?

17. G: Water Temperature • Speeds and slows algal production • Initiates lake turnover through water density changes.

18. H: Plant and fish species • Carp will stir up lake bottom and cut out light to starve plants. Increases turbidity. • Eurasian water milfoil. Currently choking lakes out!

19. I: Chemical Composition • Phosphorus levels • P.H. Levels (Especially out east) • Calcareous Fens on Lake Agassiz beach ridges.

20. J: Pollution • Point Source- Sewer pipes, septic systems, smoke pipes. Simply, pollution you pinpoint. • Non-Point Source- Field fertilizers, lawn fertilizers, and feedlots. Simply pollution that is hard to pinpoint its source.

21. K: Presence of Lotic (Running) Water • Simply stated, how much water is following through the lake via rivers or springs. • The more standing water (Lentic) the more productive the lake will be.

22. K.Q. #3: What are productivity zones of a lake? • Littoral Zone • Pelagic (limnetic) Zone: • Profundal Zone:

23. Littoral Zone • The shallow, productive margin of the lake. • Characterized by rooted vegetation • Littoral zone % closely linked to lake productivity. • Lots of photosynthesis and O2 from phytoplankton & lake surface (wind/wave action)

24. Pelagic (Limnetic) Zone • Region of open water beyond the littoral zone. • Extends from the surface to depth where photosynthesis ceases. Plankton: Phytoplankton/zooplankton present.

25. Profundal Zone: • Beneath the limnetic zone • Green plants absent • Organic matter accumulation, Bacterial/Fungi- decomposers present. Dissolved O2 sometimes absent here.

26. Productivity Zone Map

27. Another Productivity Zone Map

28. K.Q.#4: What are the three productivity categories of a lake. • Oligatrophic • Mesotrophic • Eutrophic What is this natural process of ever increasing lake productivity?

29. Eutrophication Progression Rated based on: • Time • Sedimentation • % Littoral Zone • Phosphorous content of sedimentation • Adjacent (connected) ponds, marshes, swamps. • Improvement requires dredging • Cultural Eutrophication (caused by humans) • Lotic (Running) vs. Lentic (Still) Series water

30. Oligatrophic • Nutrient Poor • 3-26 parts of phosphorous per billion parts of water • Little amount of food for producers and consumers who feed on the producers.

31. Mesotrophic • (27-83) ppb of Phosphorous • Medium amount of nutrients • Fair amount of food for producers.

32. Eutrophic • (84+) ppb of Phosphorus • Nutrient Rich • Wide variety and abundance of food • If it becomes too productive in the summer it may winter kill in upper midwest.

33. K.Q. #5: What are the features of seasonal lake cycles that affect lake productivity and water quality? • Virtually thermal stratification due to seasonal temperature changes. • This phenomena happens in the northern united states and in mountain elevations. • Found in lakes deeper than 25 feet and 10 acres or larger.

34. Thermal Stratification Levels of a lake. • Epilimnion 15-25~ (45`): Photic zone • Metalimnion: Thermocline ~ temperature changes one degree F per meter. • Hypolimnion: Coldest, as low as 39 degrees F, 4C. Water is most dense at 39 degrees, the warmer the water the less dense, the cooler is less dense. What would happen in MN if the colder the water the more dense?

35. Thermal Stratification Levels Layout

36. K.Q. #6: What are the four stages of thermal stratification. • Summer Stagnation • Fall Turnover • Winter Stagnation • Spring Turnover

37. Summer Stagnation • Thermal stratification very pronounced (no mixing of layers). • Coolest water on bottom (39 F, 4 C). • Photsynthesis starts algal production early on, but will cease as it runs out of food with no mixing of water except on lakes where nutrient pollution is a problem. • Decomposition of organic matter by aerobic bacteria depletes oxygen in hypolimnion. Fish move up!

38. Summer Stagnation

39. Fall Turnover • Upper H20 (warm) begins cooling (heavier) and begins sinking (mixes more readily). • Eventually H20 temp becomes uniform. • Nutrients from bottom decomposition become available in photic zone which may result in an algal bloom. • O2 is circulated to all depths (may be wind aided) • This part continues until all water is 4 C. • Rough fish removal with rotenone is done at this time!

40. Fall Turnover

41. Winter Stagnation • Lake is frozen over • Inverse temperature stratification • Photosynthesis continues until snowfall depth cuts out the sun. • If the snow cover ceases photosynthesis, O2 reduction starts at the bottom and works up!

42. Winter Stagnation

43. Spring Turnover • Ice Melts • Bottom continues to warm top. • Changing water densities+ heavy winds all 4 C water mix and heads into summer stagnation. • Photosynthesis resumes and DO is replaced by plant production and melting water.

44. Spring Turnover

45. The End, Lets Review!