Temporal variation in dissolved oxygen and phosphorus concentrations in Vermont restored riparian wetlands
Gillespie, Xia R
Gillespie, Xia R
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Abstract
As part of efforts to improve the water quality of Lake Champlain, the state of Vermont is working to reduce phosphorus (P) loading. One method of P load reduction is restoring riparian wetlands, which often trap sediment-bound P during floods and release dissolved P under certain conditions. Understanding the magnitude and impact of dissolved P release relative to particulate P capture is crucial to estimating the overall net P retention benefits of restored riparian wetlands. This project explores how water level and concentrations of dissolved oxygen (DO), total suspended solids, total phosphorus, and soluble reactive phosphorus compare across annual flood cycles, during different temperature regimes, and across different site attributes. We monitored five restored, riparian wetland sites along the Otter Creek and Lemon Fair River in central Vermont from 2022 through the summer of 2024. Each site included plots for wetland and adjacent river water quality monitoring, at least one high frequency water level logger and one dissolved oxygen sensor. Surface water grab samples were collected from rivers during the rising limb, and wetlands during the falling limb of flood events. Across both watersheds, there was typically no change in wetland DO between the rising and falling flood stages, despite generally more aerobic river water during the rising stage. The magnitude of yearly flooding had the greatest effect on wetland oxygen regime. The findings suggest that while aerobic conditions are relatively stable across flood events, both oxygen regime and P retention can be influenced by annual flood magnitude and watershed.
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2025-01-01