Investigating ecological tolerances of submerged aquatic vegetation in two spring-fed Central Texas rivers for the purpose of informing ecological restoration.

Abstract

Efforts to restore native aquatic vegetation in two ecologically unique spring-fed streams in Central Texas have elucidated the need to characterize conditions under which these restored communities might persist under future scenarios of reduced spring-flow. First, we tested the extent to which submerged aquatic vegetation (SAV) can utilize bicarbonate (HCO3-). Prolonged low-flow conditions induce shifts in the dissolved inorganic carbon (DIC) available for photosynthetic processes, and our results indicate that some species are incapable of fixing HCO3- while others readily or can be induced to do so. Second, we carried out an in situ distributed planting of the preferred native, Ludwigia repens, across various environmental conditions to determine those in which it succeeded. While results varied across locations, there appear to be ideal ranges in flow, depth, sediment type, and riparian canopy cover. Our findings have implications for plant choice in restoration projects and suggest a likely shift in SAV community composition under some projected flow conditions.