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

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).

Automated summary

The study examined the relationship between wet and dry mass for thirteen common submersed freshwater macrophytes during the peak growing season, finding a predictable linear relationship for all species. The species-specific dry:wet mass ratios provided supplemental data for some species and introduced novel information for others.