Submerged aquatic plant diversity and growth form distribution in north temperate lakes

Water chemistry is known to be an important driver of submerged aquatic plant community composition in lakes. However, our understanding of the extent that water chemistry and biotic interactions influence the submerged aquatic plant growth forms–elodeids, taller statured plants with stems, and isoetids, shorter statured plants with basal rosettes–is still developing. This research assesses submerged aquatic plant growth form frequency and species richness along an alkalinity gradient–a proxy for bicarbonate availability–in lakes in Vilas County, Wisconsin selected for the North Temperate Lakes LTER Regional Lakes Survey. We additionally assess frequency of the regionally rarer isoetid growth form as a function of local plant coverage and compare growth form frequency in 2015 and 2022. Twenty-eight lakes were surveyed with the Point-intercept (PI) aquatic plant survey method along a spaced grid of points in the littoral zone. We found an increase in elodeid frequency and species richness and decrease in isoetid frequency and species richness along a bicarbonate availability gradient, demonstrating the importance of modes of carbon uptake for submerged aquatic plant growth form distribution. We also found a discernable decline in isoetid frequency and increase in elodeid frequency in oligotrophic, low development lakes from 2015 to 2022, suggesting abrupt ecological change by introduction of competitive vegetation.

Primary Presenter: Linden Taylor, University of Wisconsin-Madison (lataylor6@wisc.edu)

Authors:

Linden Taylor, University of Wisconsin-Madison  (lataylor6@wisc.edu)

Ken Keefover-Ring, University of Wisconsin-Madison  (ken.keefoverring@wisc.edu)

Noah Lottig, University of Wisconsin-Madison  (nrlottig@wisc.edu)