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