Trophic Classification of Lakes Created by Diane Gravel


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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



Oligotrophic

  • Low concentrations of nutrients required for plant growth.

  • Productivity is low

  • Small populations: zoop and phytoplankton

  • Many species, low populations



Organic Matter in Oligotrophic

  • Low amounts of organic matter

  • Small populations of bacteria

  • Small numbers of plankton, low oxygen consumption in deep H2O



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



More Characteristics: Oligotrophic

  • Nice clean water

  • Bottoms are sandy and rocky

  • No weed problems

  • Poor fishing

  • Deep and cold water

  • Seldom in populated areas



Where are Oligotrophic Lakes Found?

  • Seldom in populated areas, tends to shift the classification

  • Seldom in agricultural areas

  • Michigan - upper peninsula



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



Zoop and Minnows Lots of food for all

  • High numbers of zooplankton and small fish

  • Growth of larger fish



Organic Matter in Eutrophic

  • Considerable depth of organic matter

  • In the bottom of the lake

  • Provides Food for high numbers of bacteria.



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)



Phosporus and Chlorophyll in Eutrophic Lakes

  • High phytoplankton produced

  • Resulting in high chlorphyll concentrations, 14 mg m-3 or higher

  • Phosphorous averages 80 mg m-3



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



Great Fishing for Humans

  • Good growth rates of fish

  • Due to high production of plankton and benthic (bottom dwelling) organisms



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.



Transition in Classification: Mesotrophic

  • “little beyond oligtrophic”

  • “not quite eutrophic”

  • 1000’s of years from oligotrophic lakes aging to eutrophic.

  • Intermediate stage



Cultural Eutrophication

  • Can occur in one human generation

  • Chemical enrichment by human activity in drainage basin



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



Weeds and Fishing: Mesotrophic

  • Scattered weed beds, sparse

  • Fishing is reasonably good

  • Lake cannot handle great amounts of fishing pressure as in Eutrophic Lakes.



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



Carlson, Robert TSI 0-100 Alternative 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.



Research Data: Field Limn



Research Data: Field Limn



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