Title: Do constructed wetlands support aquatic top predators?
Author: Ethan Isaac, Akira Terui
Abstract
Over the past few decades, significant efforts have been invested in wetland restoration. Many of these restoration projects assumed that rebuilding basal habitat is sufficient to underpin sustainable populations, including those occupying higher trophic levels. However, evidence remains limited on whether constructed wetlands foster populations of top predators. This study aims to evaluate whether constructed wetlands can support populations of aquatic snakes, top predators in wetland ecosystems. We hypothesized that constructed wetlands are less likely to be occupied by aquatic snakes because they provide limited supplies of prey resources, such as fish and amphibians. To test this hypothesis, we collected preliminary data on snake distributions, prey densities (fish and amphibians), and terrestrial habitat structures near the water (plant cover and height). Compared with natural wetlands and streams, prey densities were lower in constructed wetlands, particularly when they are hydrologically isolated from the river network in the landscape. In addition, plant cover and height in constructed wetlands were significantly higher relative to natural wetlands. Snake distributions appeared to follow these differences in prey densities and habitat structure. In total, we detected three occurrences of Northern water snake, Nerodia sipedon, and all of these occurrences were recorded in either natural wetlands or streams. However, the limited detections of snake occurrences did not allow us to statistically test the influence of wetland types on their distribution. Our preliminary results imply that constructed wetlands may not support viable populations of aquatic top predators. However, given the lack of sufficient statistical replicates in our data, these results must be interpreted carefully, and additional data collection would help draw robust conclusions.