Estimating the Standing Biomass of Aquatic Macrophytes

The accuracy, precision, and cost-efficiency of estimation techniques for macrophyte standing biomass are examined, and solutions are offered to problems encountered in the design of efficient sampling programs. Five sizes of quadrats (100 cm 2 to 1 m 2 ) were compared on seven occasions and ail five yielded equivalent biomass estimates in six of these tests. Published and unpublished values of biomass sampling variance measured around the world were predictable from average standing biomass and size of sampler. The sampling cost was predictable from sampler size. Analysis of these relationships allows optimization of sampling design. The use of small quadrat samplers with great replication is recommended. Adherence to this protocol can result in a 30-fold reduction in sampling cost. Recommendations are compared with techniques actually used by aquatic ecologists. A brief analysis of spatial heterogeneity of aquatic macrophyte biomass is presented.