Characterization of suspended particles in Everglades wetlands

Abstract

We report the concentration, phosphorus (P) and nitrogen (N) content, and size and chemical fractionation of fine suspended particles (0.2‐100 µm) and colloids (3 kilodalton [kDa]‐0.1 µm) in the surface water of Everglades wetlands along regional and P‐enrichment gradients. Total suspended sediment concentrations ranged from 0.7 to 2.7 mg L−1. Total particulate P concentrations increased from 0.05 µmol L21 to 0.31 µmol L−1 along the Penrichment gradient. Particles contained from 20% to 43% of total P but <12% of total N in surface water. Dissolved (<0.2 µm) organic N contained about 90% of total N, with the 3‐100‐kDa colloidal size class containing the most N of any size class. The 0.45‐2.7‐µm size fraction held the most particulate P at all sites, whereas particulate N was most abundant in the 2.7‐10‐µm size class at most sites. Standard chemical fractionation of particles identified acid‐hydrolyzable P as the most abundant species of particulate P, with little reactive or refractory organic P. Sequential chemical extraction revealed that about 65% of total particulate P was microbial, while about 25% was associated with humic and fulvic organic matter. The size and chemical fractionation information suggested that P‐rich particles mostly consisted of suspended bacteria. Suspended particles in Everglades wetlands were small in size and had low concentrations, yet they stored a large proportion of surface‐water P in intermediately reactive forms, but they held little N.