Influence of Particle Shapes and Size Distributions on Fine Particulate Organic Matter Surface Area in Streams

The objective of this study was to determine whether fine particulate organic matter (FPOM) from different sources would have similar surface areas. Individual FPOM particles collected from Grasshopper Creek (clear-cut), Mack Creek (old-growth coniferous forest), and Quartz Creek (second-growth) in Oregon were photographed using scanning electron microscopy, and their surface area was calculated by assuming spherical or cylindrical shapes. In Grasshopper Creek, FPOM cylinders (n = 326) represented 89% of the total surface area (124.9 m2) and 68% of the total FPOM numbers. In Mack Creek, FPOM cylinders (n = 231) contributed 77% of the total surface area (114.2 m2) even though they represented only 55% of the total numbers. In Quartz Creek, FPOM cylinders (n = 185) represented 79% of the total surface area (61.8 m2) and 60% of the total numbers. There was a significant difference in the distribution of particle sizes and shapes from the different streams, particularly between Mack Creek and the other two streams. These differences are likely due to the differences in riparian vegetation. The importance of FPOM surface area to physical, chemical, and biological processes in aquatic ecosystems is usually overlooked in favor of more easily measured FPOM mass.