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SMALL LAKES, PONDS, & SEDIMENTS

SMALL LAKES, PONDS, & SEDIMENTS. Small Ponds. Most common form of limnetic environment Usually in depressions in lowland areas Tend to accumulate organic and mineral sediments. Shallow lakes also tend to be dominated by macrophytes

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SMALL LAKES, PONDS, & SEDIMENTS

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  1. SMALL LAKES, PONDS, & SEDIMENTS

  2. Small Ponds • Most common form of limnetic environment • Usually in depressions in lowland areas • Tend to accumulate organic and mineral sediments

  3. Shallow lakes also tend to be dominated by macrophytes • Submerged macrophytes become established in water that is protected

  4. Submerged Macrophytes and Phytoplankton • Macrophytes dominate by • Sequestering nitrogen and phosphorus • Providing refugia for large zooplankton that feed on phytoplankton • Providing large surface area for growth of periphyton, which competes with phytoplankton • Releasing compounds that inhibit growth of phytoplankton • Causing large fluctuations in daily oxygen, pH, etc.

  5. Submerged Macrophytes and Phytoplankton • Phytoplankters dominate by • Shading out submerged macrophytes, especially in conditions of high nutrient loading • Surviving in conditions of high turbidity • Thriving in conditions of the absence of refugia for zooplankton; situations which usually support sight-feeding fish

  6. Temporary Pools

  7. Temporary Streams

  8. Components of Sediments • Organics • Particulate minerals (e.g. carbonates, clays, and silicates) • Inorganics of biogenic origin (frustules, scales, calcium carbonate)

  9. Humus

  10. Dy • Pronounced dee • Slightly acidic with unsaturated colloids • Soft and brown • >50% organic • If C:N ratio > 10, it is acid and sediment is dy

  11. Gyttja • Pronounced yit-ya • Neutral • Soft, gray-green to black • <50% organic • If C:N ratio <10 humus is neutral and sediment is gyttja

  12. Humics from littoral and wetland floras • Lignins degrade to humic compounds • Heavily lignified emergent flora make more humics • If alkaline, sapropel • See Table 21-1

  13. Decomposition rates in sediments Carbohydrates-amino acids-amino sugars > Humic compounds > Lipids

  14. autolysis most bacterial decay

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