Polyphosphate accumulation tracks incremental P-enrichment in a temperate watershed (Pennsylvania, USA) as an indicator of stream ecosystem legacy P

Authors: TAYLOR, SHAYNA - Central Michigan University; SAIA, SHEILA - North Carolina State University; Buda, Anthony; REGAN, JOHN - Pennsylvania State University; WALTER, TODD - Cornell University; CARRICK, HUNTER - Cornell University

Submitted to: Frontiers in Environmental Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2022
Publication Date: 7/6/2022
Citation: Taylor, S., Saia, S.M., Buda, A.R., Regan, J.M., Walter, T.M., Carrick, H.J. 2022. Polyphosphate accumulation tracks incremental P-enrichment in a temperate watershed (Pennsylvania, USA) as an indicator of stream ecosystem legacy P. Frontiers in Environmental Science. 10:920733. https://doi.org/10.3389/fenvs.2022.920733.
DOI: https://doi.org/10.3389/fenvs.2022.920733

Interpretive Summary: Understanding how microbial organisms control phosphorus cycling in agricultural streams is an essential facet of water quality management and protection. In this study, we exposed bottom-dwelling groups of bacteria, algae, and diatoms (biofilms) to six different levels of phosphorus loading and measured the amount of phosphorus that was taken up by the biofilms. Study results showed that the capacity of stream biofilms to take up and store phosphorus decreased as phosphorus loading increased. Findings reveal the importance of studying stream biofilms as indicators of legacy phosphorus pollution in agricultural watersheds.

Technical Abstract: Legacy P concentrations resulting from historic additions of phosphorus (P) to the landscape may impede rapid remediation of P pollution and achievement of water quality management goals. Herein, we hypothesized that the capacity of stream biofilms to assimilate new polyphosphate is controlled by the degree of stream legacy phosphorus (P). To test this hypothesis, a series of in situ enrichment experiments were deployed at five sites of varying land cover in central Pennsylvania, USA. Incremental P-loading was delivered using vials fitted with porous lids, that contained agar enriched with 6 levels of P (as DIP, dissolved inorganic P) loading with rates ranging from 0 to 1,540 µg PO4-3/day; these loading rates mimicked natural stream P loadings. Substrata were incubated at stream sites for a relatively short incubation period (12 days), to measure uptake rates; after which, biofilms growing on the lids were removed and their tissue content was analyzed for biomass (as chlorophyll) and various forms of particulate phosphorus. Polyphosphate (polyP) accumulated by stream biofilms at all sites closely tracked the release of dissolved inorganic P from experimental enrichment assays. Comparatively, biofilms accumulated a relatively little amounts of PIP (Particulate inorganic P) and other forms of organic P (e.g., DNA, RNA, lipids, proteins). Viewed at the watershed scale, land use appeared to affect P accumulation, where sites dominated by forest cover had a higher capacity for P storage, while sites dominated by agriculture did not; this underscores the importance of polyP storage as an indicator of legacy P pollution.