The use of corn pollen and glass beads to estimate fine particulate organic matter retention

Abstract

Corn pollen and glass beads were used as surrogates of natural fine particulate organic matter (FPOM). These particles were released into ten streams in three different physiographic regions, Appalachian Mountains, Rocky Mountains, and Central Plains, within the United States. Mean travel distance for corn pollen was 121 m and that for glass beads 40 m. Rates of deposition through the water column for both particles were 0.484 mm/sec and 0.643 mm/sec, respectively. This empirically derived deposition velocity was only a fraction of the still water fall velocity. Hydraulic parameters indicate that flow conditions at the stream bed prevent establishment of a laminar sublayer. As a result, corn pollen and glass beads should be entrained and moved as bed- or suspended load. Gradient was the single best stream characteristic to explain variation in retention rates for both corn pollen and glass beads. Based on deposition velocities, estimates of benthic FPOM turnover times ranged from 20 hours to 8.3 days, rate of FPOM downstream movement was 1-24 m/d, and carbon turnover length was 1-24 km.