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Trophic Classification of Lakes

Trophic Classification of Lakes. Created by Diane Gravel. The Trophic Concept . Nutrient richness of lakes is the basis of classification. Super clear lakes to poor water clarity Oligotrophic lakes to Eutrophic Place limits along continuum Classic Definitions: Forsberg, Ryding.

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Trophic Classification of Lakes

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  1. Trophic Classification of Lakes Created by Diane Gravel

  2. The Trophic Concept • Nutrient richness of lakes is the basis of classification. • Super clear lakes to poor water clarity • Oligotrophic lakes to Eutrophic • Place limits along continuum • Classic Definitions: Forsberg, Ryding

  3. Oligotrophic • Low concentrations of nutrients required for plant growth. • Productivity is low • Small populations: zoop and phytoplankton • Many species, low populations

  4. Organic Matter in Oligotrophic • Low amounts of organic matter • Small populations of bacteria • Small numbers of plankton, low oxygen consumption in deep H2O

  5. Water Transparency • Secci Disk 10 meters depth • Few suspended algae. • Low chlorophyll readings 1.7 mg m-3 • Low nutrients • Low phosphorous 8.0 mg m-3

  6. More Characteristics: Oligotrophic • Nice clean water • Bottoms are sandy and rocky • No weed problems • Poor fishing • Deep and cold water • Seldom in populated areas

  7. Where are Oligotrophic Lakes Found? • Seldom in populated areas, tends to shift the classification • Seldom in agricultural areas • Michigan - upper peninsula

  8. Eutrophic Classification • In Contrast to the oligotrophic lakes the other end of the continuum. • Rich in plant nutrients • Productivity is high • high numbers of phytoplanton (suspended algae), cloud H2O • Poor Secchi disk readings of 2.5 meters

  9. Zoop and MinnowsLots of food for all • High numbers of zooplankton and small fish • Growth of larger fish

  10. Organic Matter in Eutrophic • Considerable depth of organic matter In the bottom of the lake • Provides Food for high numbers of bacteria.

  11. Oxygen in the Lower Waters • Decending plankton and bacteria use O2 in lower depths • Summertime depletion of O2 below the thermocline (below 5.5 meters)

  12. Phosporus and Chlorophyllin Eutrophic Lakes • High phytoplankton produced • Resulting in high chlorphyll concentrations, 14 mg m-3 or higher • Phosphorous averages 80 mg m-3

  13. Weeds and Depth of Eutrophic • Weed beds grow due to available nutients • Light penetrates shallow depths • Organic matter in the bottom makes great soil for their roots

  14. Great Fishing for Humans • Good growth rates of fish • Due to high production of plankton and benthic (bottom dwelling) organisms

  15. Where are Eutrophic Lakes Found? Hyptothesis….. • Lower 2/3 of Michigan’s lower Penninsula in study • Drawing comparisons to Russell Pond in northern NH to Barbados and Stonehouse Pond in southern, NH • More north, the more oligotrophic lakes found.

  16. Transition in Classification: Mesotrophic • “little beyond oligtrophic” • “not quite eutrophic” • 1000’s of years from oligotrophic lakes aging to eutrophic. • Intermediate stage

  17. Cultural Eutrophication • Can occur in one human generation • Chemical enrichment by human activity in drainage basin

  18. Mesotropic Classification • Plankton is intermediate • Some organic sediment • Some loss of O2, usually in lower depths • Water is moderately clear with Secchi Depths • Chlorophyll and Phosphorus concentrations between Oligotrophic and Eutropic lakes

  19. Weeds and Fishing: Mesotrophic • Scattered weed beds, sparse • Fishing is reasonably good • Lake cannot handle great amounts of fishing pressure as in Eutrophic Lakes.

  20. PHOSPHORUS AND CHLOROPHYLL CONCENTRATIONS AND SECCHI DISK DEPTHS CHARACTERISTIC OF THE TROPHIC CLASSIFICATION OF LAKES MEASURED PARAMETER Oligotrophic Mesotrophic Eutrophic Total Phosphorus (mg/m3)   Average 8 26.7 84.4                                                 Range 3 .0 - 17.7 10.9 - 95.6 16 – 386 Chlorophyll a  (mg/m3)        Average 1.7 4.7 14.3                                                Range 0.3 - 4.5 3 – 11 3 – 78 Secchi Disk Depth (m)          Average 9.9 4.2 2.45                                                Range 5.4 - 28.3 1.5 – 8.1 0.8 – 7.0 Table I – Data from Wetzel, 1983

  21. Carlson, Robert TSI 0-100Alternative Definitions Trophic states use by DEP TSI Trophic state Attributes Aquatic life < 30 Oligotrophic Clear water Trout possible in Oxygenated hypolimnion in deep waters   Low Production  30 – 50 Mesotrophic Moderately clear water  Warm water fishery   Possible Anoxia in summer  50 – 70 Eutrophic Low transparency Warm water fishery Anoxic hypolimnion in summer > 70 Hypereutrophic Dense algae and macrophytes Noticeable Odor Fish Kills Possible • Notes: Table from USEPA, 1999, p.4-2.

  22. Research Data: Field Limn

  23. Research Data: Field Limn

  24. THE ENDPlease fill out your evaluationsThank You

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