Size Separation of Marine Seston by Membrane and Glass‐fiber Filters1

The average minimum sizes of particles retained by metal membranes (Selas Flotronics) and perforated polycarbonate membranes (General Electric Nuclepore) were similar to the stated pore sizes when relatively small seawater samples with moderate concentrations of particles were filtered. When large samples or high concentrations were filtered, the average retention size was less than the stated pore size. All cellulose ester membranes (Millipore) retained particles much smaller than the stated pore size, even from small samples with low particle concentrations. Glass‐fiber filters had retention characteristics similar to membrane filters.