ABSTRACT

The content of chlorophyll a of a group of plant species from freshwater, brackish-water and nearshore marine environments was found spectrophotometrically to range from 1 to nearly 300 mg/g on a dry-weight, ash-free basis. The average chlorophyll content of marine, mostly algal, plants from Dillon Beach area, California, was highest among collections studied (38 mg/g), followed by freshwater pondweeds from Minnesota lakes (29 mg/g), marine algae from Coos Bay, Oregon, (25 mg/g) and brackish water pondweeds and algae from Chesapeake Bay (8 mg/g). The low values in Chesapeake Bay species are partly due to the absence of forms that in the other areas studied have chlorophyll values of 100 mg/g or higher.

The content of pheophytin a in Minnesota lake sediments from the same, as well as different, localities from which plants were studied amounts to 200-600 ppm of dry organic matter (ash free and corrected for carbonate) in surface samples but only about 70 ppm in silty tidal flat sediments from Tomales Bay, California. In both the marine and freshwater sediments a rapid decrease in pheophytin takes place a few cm beneath the surface. The downward decrease probably results from the utilization of pheophytin as food in the microzone just beneath the surface.

The relative pheophytin content of lake sediments although mainly due to the prevailing level of productivity of the lake, is in part governed by the morphometry of the basin and prevailing wind action. Smooth margined, steeply sloping basins show generally not only lower organic productivity but also lower pheophytin content than those with irregular margins and gentle slopes. Some tendency for sedimentary pheophytin enrichment was noted on the lee sides of the latter type of lake due to wave transport.

A period of relatively high organic productivity between depths of 500 and 700 cm in sediments of Blue Lake, Minnesota is reflected in an increase in chlorinoid pigments at these depths.

A variety of fluorescent substances tentatively identified as flavinoids, indole acids and other heterocyclic substances have been found in lake and bog deposits and associated plants. These are believed to have been formed by organisms living in the sediments. In a general way the fluorescent substances represent the products of animal metabolism under poorly oxidative conditions, and the amount reflects the level of such activity in individual deposits.

An episode of increased sedimentary-biologic activity of depths of 8 to 10 meters (dark copropel layer) in Cedar Creek Bog, Minnesota is suggested by an increase in flavinoid pigments in sediments at these depths.