Transcript Paleolimnology and Susccession in Aquatic Systems

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