Sediment and nutrient retention by freshwater wetlands: Effects on surface water quality

TLDR

Freshwater wetlands improve downstream water quality, but the magnitude and reversibility of their sediment and nutrient retention vary among wetland types. This review aims to summarize how freshwater wetlands interact with sediment and nutrients to influence surface water quality. Retention occurs through sedimentation, plant uptake and litter decomposition, soil sorption, and microbial processing, with sedimentation providing permanent deposition and plant and microbial pathways offering short‑to‑long‑term nutrient removal. The review discusses wetland storage compartments, fluxes, and net retention rates for nitrogen and phosphorus.

Abstract

Abstract Freshwater wetlands alter surface water quality in ways which benefit downstream use. This review summarizes the mechanisms of freshwater wetland interaction with sediment and nutrients that affect surface water quality. The mechanisms vary in magnitude and reversibility, and differ among wetland types. They include sedimentation, plant uptake, litter decomposition, retention in the soil, and microbial processes. Sedimentation is a relatively permanent retention mechanism whereby particulates and associated contaminants are physically deposited on the wetland soil surface. Plant uptake and litter decomposition provide short‐to long‐term retention of nutrients, depending on rates of leaching, translocation to and from storage structures, and the longevity of plant tissues. Plant litter can also provide a substrate for microbial processing of nutrients. Wetland soils sorb nutrients, and provide the environment for aerobic and anaerobic microorganisms that process nutrients. Wetland storage compartments, fluxes, and net retention rates are discussed for nitrogen and phosphorus.