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<br />laboratory for analysis. Chlorophyll ~ extraction and analysis was performed <br />according to methods outlined in Parsons and Strickland (1963). <br /> <br />Particulate organic material. - Organic material composed of living or dead <br />suspended particulate material is important to the ecosystem since it <br />represents a potential food source for aquatic fauna such as zooplankton or <br />larval fish. Two size-fractions (>25 pm and <25 pm) of inorganic and organic <br />suspended particulate material in the river and backwaters were determined as <br />follows; fifty liters of water were filtered through a 25 ~m pore-size net. <br />About 10 l of the filtrate passing through the 25-pm net was retained in a <br />clean container. The >25 pm fraction retained by the net was collected and <br />preserved with sufficient formalin to yield about a 2 percent solution for <br />subsequent laboratory analysis. From the 10 l of filtrate that passed through <br />the net (the <25 pm fraction), two replicate 500 to 1500 mL volumes were <br />vacuum-filtered through separate, preweighed, preashed Gelman AlE fiberglass <br />filters, and returned to the laboratory. These preweighed and numbered <br />filters were dried in an oven, weighed, ashed to burn off the organic portion <br />of the filtered material, and weighed to determine the percent of organic vs. <br />inorganic material. The same procedure was used to separate organic from <br />inorganic material in the >25 ~ size-fraction. <br /> <br />Phytoplankton and zooplankton. - Duplicate 25-L water samples were collected <br />and filtered through an 80 pm plankton net (in 1987) to determine abundance <br />and identity of net phytoplankton and zooplankton in both the main river and <br />backwaters. Samples were preserved in sufficient buffered formalin to yield a <br />5 percent concentration. In 1988, plankton samples were collected using a <br />25 pm plankton net. At selected sites, 1 liter of the <25 ~ filtrate was <br /> <br />21 <br />