Paleolimnology and Succession in Aquatic Systems
Feb 22, 2016
Paleolimnology and Succession in Aquatic Systems
Sediments of Lakes
• Hold records of past lake conditions• Hold records of past terrestrial conditions
From Hutchinson Treatise on Limnology(a) General zonation and processes in lakes. (b) Processes and sediments in lakes with abundant supply of terrestrial sediment. (c) Processes and sediments in lakes with dominant carbonate sediment and little influx of terrestrial sediment. (Sketched from data in Hutchinson (1957) A treatise on limnology, Wiley; Reeves (1968) Introduction to paleolimnology, Elsevier; and Matter and Tucker (1978) Modern and ancient lake sediments, International Association of Sedimentologists, Special Publication No. 2, Blackwell.)
Glacial Pleistocene Lake Vermont
• From Tufts University Varve Project
Varve Project
Varve Project
Some Biogenic Substances Occur in Lake Sediments
Isolate Pigments by Thin Layer Chromatography
Paleolimnology Studies the Record of Change in Aquatic Systems
• Erosion --> Sedimentation (mineral deposits)• Then organic input > rate of degradation
(organic deposits)
Standard Dogma for Lake Succession
Oligotrophic Lake Eutrophic Lake
Nutrient Loading Low High
Primary Production Low High
Oxygen Demand in Sediment Low High
Oxygen Demand in Hypolimnion Low High
Nutrient Cycling Low High
Initial Stages in the Development of a Lake
• Phytoplankton production depends on nutrient input
• In eutrophic condition, dense algal layers create:– Decreased light penetration– Decreased trophogenic zone
Development of Hardwater lakes
• Ca inactivates P, Fe, Mn• May be counteracted by high organic loading• Thus, very rapid change from oligotrophic to
eutrophic environment• Can be counteracted by cation exchange
mechanisms of plants (particularly mosses like Sphagnum)
The End of Lake Development
• A change from phytoplankton to littoral production
• Environment can become dystrophic (usually with high levels of humic acids)
Stratigraphy of Lago di Monterosi
35,000 BP Formed by volcanic blast Basin filled
Until 10,000 BP
Shallow; ~ 10m deep Oligotrophic, acidic
10,000 BP Less than 1 m Bog during dry period
171 BC Romans built Via Cassia Rapid eutrophication
After 171 BC to 1000 AD
Decline in tree pollen/ increased sedimentation
Maintains eutrophic state
After 1000 AD Sedimentation declined Eutrophic/mesotrophic
Swamp
• Woody vegetation through basin
Marsh
• Wetland dominated by herbaceous plants
The Everglades
Mire
• High humidity and high rainfall lead to thick peat accumulations
Fen
• Minerotrophic Mire: groundwater supplies nutrients; usually circum neutral or basic
Bog
• Ombotrophic Mire: inorganic nutrients from rainwater; pH drops as Sphagnum increases