Lake SuccessionLake Succession

Change in LakesChange in Lakes Lakes not static - always changingLakes not static - always changing

Change is not random, but directionalChange is not random, but directional

Change in LakesChange in Lakes In general, lakes proceed from a stage in In general, lakes proceed from a stage in

which productivity is low, to a stage of high which productivity is low, to a stage of high productivityproductivity

Change in LakesChange in Lakes Concurrent with change in productivity, the Concurrent with change in productivity, the

lake gradually fills in with organic matter lake gradually fills in with organic matter and inorganic sedimentsand inorganic sediments

Change in LakesChange in Lakes Filling in and increasing productivity together Filling in and increasing productivity together

produce produce lake aginglake aging or or eutrophicationeutrophication Gradual process that takes 100s or 1000s of Gradual process that takes 100s or 1000s of

yearsyears

The ProcessThe Process Start with a newly Start with a newly

formed lake - formed lake - glaciated regionglaciated region

OligotrophicOligotrophic - low - low productivity - productivity - severely limited by severely limited by cold climatecold climate

The ProcessThe Process Leeching from Leeching from

basin, runoff from basin, runoff from watershed carries watershed carries low amount of low amount of nutrientsnutrients

Produces low Produces low productivity, productivity, primarily from primarily from phytoplanktonphytoplankton

The ProcessThe Process Low productivity Low productivity

maintained by maintained by continued low inputs continued low inputs of inorganic nutrients of inorganic nutrients from outside basinfrom outside basin

Low productivity -> Low productivity -> low levels of organic low levels of organic matter -> low rates of matter -> low rates of decompositiondecomposition

The ProcessThe Process High dissolved OHigh dissolved O22

in hypolimnion in hypolimnion results in low results in low release of nutrients release of nutrients from sedimentsfrom sediments

Low Productivity CycleLow Productivity Cycle“Oligotrophic”“Oligotrophic”

Medium Productivity CycleMedium Productivity Cycle“Mesotrophic”“Mesotrophic”

Med.

Med.

Med.

Med.

Med.Med.

Med.

Med.

Med.

High Productivity CycleHigh Productivity Cycle“Eutrophic”“Eutrophic”High

High

High

High

HighHigh

Low

High

High

Early SuccessionEarly Succession High OHigh O22

Low COLow CO22 Inorganic soilInorganic soil Sparse vegetationSparse vegetation Sparse food (chiefly pelagic)Sparse food (chiefly pelagic) High transparencyHigh transparency Low fertilityLow fertility Usually alkalineUsually alkaline ““Coldwater” fishesColdwater” fishes

Late SuccessionLate Succession Low OLow O22

High COHigh CO22 Organic soilOrganic soil Abundant vegetationAbundant vegetation Abundant foodAbundant food Low transparencyLow transparency High fertilityHigh fertility Increasing acidityIncreasing acidity ““Warmwater” fishesWarmwater” fishes

Human-caused Lake AgingHuman-caused Lake Aging

Cultural eutrophicationCultural eutrophication Slow Slow

turnoverturnover

Accumulation Accumulation of nutrients, of nutrients, excessive plant excessive plant growth, algae growth, algae bloomsblooms

Case Study: The Great LakesCase Study: The Great Lakes

Littoral EncroachmentLittoral Encroachment

Littoral EncroachmentLittoral Encroachment