Rake Sampling to Estimate Biomass of Submersed Aquatic Vegetation in Coastal Wetlands
2020
Masto, Nicholas M. | Bauer, Beau A. | Kaminski, Richard M. | Sharpe, Caroline | Leland, Robert C. | Wiggers, Ernie | Gerard, Patrick D.
We evaluated two rake-enclosure sampling methods for estimating biomass of submersed aquatic vegetation (SAV) within managed tidal impoundments (MTIs) in the Ashepoo-Combahee-Edisto Rivers Basin, South Carolina. We collected SAV using a modified rake within 0.086 m² cylindrical sampler (CS), a non-modified rake within 0.2-m² quadrat (QS), and after raking, hand-collected remaining SAV within each enclosure (i.e., rake + hand = total SAV biomass). We used linear mixed models to evaluate rake sampling methods to estimate total (QS and CS) and species-specific SAV biomass (QS). The marginal coefficient of determination (R²) for both rake sampling methods was 0.95 for estimating total SAV biomass and model fitted values met our a priori acceptable level of precision (CV ≤ 15–20%). Furthermore, the QS-rake method explained 95% of the variation in total widgeongrass biomass (Ruppia maritima), 97% of dwarf spikerush biomass (Eleocharis parvula), and 97% of muskgrass (Chara spp.) biomass but model fitted values only met a priori precision for widgeongrass biomass. We conclude that our rake-SAV sampling estimates total SAV and widgeongrass biomass with little unexplained variation. Furthermore, abiotic variables had no significant effect when estimating SAV biomass. We suggest managers and researchers use our rake methods to estimate biomass of SAV in wetlands with similar species compositions, and resulting estimates may be used to estimate foraging carrying capacity for habitat conservation planning and management.
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