The three ponds are located in the high marsh (1.43-1.46 m above North American Vertical Datum of 1988) of the Plum Island Ecosystems – Long Term Ecological Research (PIE-LTER) site. Suspended POM in pond surface waters was collected weekly in 1 L combusted glass bottles and filtered through combusted glass fiber filters (June 25-August 13, November 11-25, 2014) and analyzed for TOC, TN, δ¹³C, and δ¹⁵N. All samples were frozen (-20 ℃) until analysis. Samples were prepared for elemental and isotopic analyses by drying to constant mass (60 °C) and fuming with hydrochloric (HCl) acid to remove carbonates (Hedges and Stern 1984). Analyses were performed by the Stable Isotope Laboratory at the Marine Biological Laboratory (Woods Hole, MA). Isotopic data are reported in the conventional δ-notation in units of per mil (‰).