Species-specific wet-dry mass calibrations for common submersed macrophytes in the Upper Mississippi River

Abstract

• We examined the relationship between wet and dry mass of 13 submersed macrophyte species. • Standardized major axis tests indicate predictable relationship between wet and dry mass. • Dry mass can be estimated from fresh mass for submersed species. • Species-specific dry mass ranged from 5-13% of wet mass. • Additional research will permit examination of sources of within-species variation in dry matter. Submersed freshwater macrophytes can provide numerous crucial ecosystem functions and influence biotic assemblages across multiple trophic levels. These functions are dependent on abundance, which has been most often reported as biomass in terms of dry mass per unit area. Determining dry mass is a time- and labor-intensive process that may not be practical at the assessment scale of interest. We examined the relationship between wet and dry mass during the approximate peak growing season for thirteen submersed species common on the Upper Mississippi River and other aquatic systems in the midwestern USA and beyond ( Ceratophyllum demersum , Elodea canadensis , Heteranthera dubia, Myriophyllum sibericum , Myriophyllum spicatum , Narrow-leaf pondweeds (likely included Potamogeton foliosus , P. pusillus), Potamogeton crispus , Potamogeton nodosus , Potamogeton richardsonii , Potamogeton zosteriformis, Ranunculus longirostris , Stuckenia pectinata , and Vallisneria americana). All species exhibited a predictable linear relationship between wet and dry mass. The species-specific dry: wet mass ratios of 5.0–13.1% presented here supplement previously published data for some species, represent novel information for others and allow for estimations of dry mass from fresh material when direct measurement of the former is impractical. Pairwise comparisons of the individual estimates indicated four distinct groups of species within the overall gradient of dry:wet mass ratios. Lowest estimates of percent dry mass were for species previously associated with higher flow ( V. americana and H. dubia ) and highest values were for species typically found in still water ( P. zosteriformis and the P. foliosus / P. pusillus group).