SEDIMENT DRIVES PHOSPHORUS STORAGE IN SMALL AGRICULTURAL STREAMS

A major driver of eutrophication in aquatic ecosystems is phosphorus (P) pollution. While controlling P loss at its source is important, P export to lakes and estuaries may be influenced by P storage and transformation within lotic ecosystems. However, spatial patterns in P storage in different pools (plants, algae, and sediment) across watersheds has received little attention, but likely varies considerably with flow and stream size. We examined the form, quantity, and location of phosphorus stored in an agriculturally dominated small watershed (20 km²) in northwest Ohio, USA. We measured the P stored in sediment, plant, and algae pools in 15 reaches varying in size and flow regime from grassed waterways to a third order stream. Sediment-P dominated P-pools at all sites regardless of stream type or habitat. Variation in total sediment accounted for the largest amount in variation of total P among sites. The P content of sediment, algae, and plants were similar among pools and reaches. P concentration of plants and algae ranged from less than 1 to 3.5 times the P concentration in sediment. By contrast, sediment mass was 1.3-326 times larger than the plant mass across sites. At each site, more P was associated with sediment than all other pools combined. Additionally, measurements indicate that streambed sediments acted as a phosphorus sink across all sites sampled. In streams with high sediment loads, processes determining sediment stores along the stream reach also drive phosphorus storage.

Primary Presenter: Joseph Gentine, The Ohio State University (gentine.3@buckeyemail.osu.edu)

Authors:

Martin Jay, The Ohio State University  (martin.1130@osu.edu)

Laura Johnson, Heidelberg University  (ljohnson@heidelberg.edu)

James Hood, The Ohio State University  (hood.211@osu.edu)