Forthcoming Research Paper

Coastal Stormwater Pond Age and Phosphorus Cycling within Water and Sediment

by Morolake M. Fatunmbi, Debabrata Sahoo, Amy E. Scaroni, Calvin B. Sawyer, Erik Smith, Sarah A. White

Abstract

Effective management of coastal stormwater ponds (SWPs) requires an understanding of how pond age affects nutrient dynamics, particularly in reducing eutrophication and regulating nutrient loading to downstream waterbodies. The objectives of our study were to (1) assess the impact of pond age on water quality and (2) evaluate whether pond sediments behave as a phosphorus (P) source or sink. Nine SWPs in residential areas of Charleston, South Carolina, were studied and categorized into three distinct age groups: Young (0-5 years), Middle-age (5-15 years), and Old (15+ years). Water samples and sediment cores were collected in summer 2023 and winter 2024. Water quality and sediment characteristics were analyzed, with a focus on the estimation of equilibrium P concentration (EPC0) to determine if sediment behaved as a P source or a sink. Water quality varies across pond ages. Old ponds had higher total P and nitrogen levels. Sediments in all ponds served as a source of P, releasing P back into the water column. These findings highlight the need for targeted management strategies to address P release from sediment to maintain water quality in coastal stormwater ponds.