Chlorophyll a averages about 38 mg per g in marine plants, 29 in freshwater pondweeds, 25 in marine algae, and 8 in brackish water pondweeds and algae on a dry-weight ash-free basis. Pheophytin a, a degradation product of chlorophyll a, amounts to 200-600 ppm of dry organic matter (ash free and corrected for carbonate) in Minnesota lake sediments from localities related to the plant data, but only about 70 ppm in silty tidal flat sediments from Tomales Bay, California. Contents of pheophytin a decrease rapidly in the first few cm beneath the surface. Tentatively identified flavinoids, indole acids and other heterocyclic substances occur in lake and bog deposits and probably represent metabolic products of organisms living in the sediments.

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