Apportionment of bioavailable phosphorus loads entering Cayuga Lake, New York

Abstract

The integration of the phosphorus (P) bioavailability concept into a P loading analysis for Cayuga Lake, New York, is documented. Components of the analyses included the: (1) monitoring of particulate P (PP), soluble unreactive P (SUP), and soluble reactive P (SRP), supported by biweekly and runoff event‐based sampling of the lake's four largest tributaries; (2) development of relationships between tributary P concentrations and flow; (3) algal bioavailability assays of PP, SUP, and SRP from primary tributaries and the three largest point sources; and (4) development of P loading estimates to apportion contributions according to individual nonpoint and point sources, and to represent the effects of interannual variations in tributary flows on P loads. Tributary SRP, SUP, and PP are demonstrated to be completely, mostly, and less bioavailable, respectively. The highest mean bioavailability for PP was observed for the stream with the highest agriculture land use. Point source contributions to the total bioavailable P load (BAPL) are minor (5%), reflecting the benefit of reductions from recent treatment upgrades. The BAPL represented only about 26% of the total P load, because of the large contribution of the low bioavailable PP component. Most of BAPL (>70%) is received during high flow intervals. Large interannual variations in tributary flow and coupled BAPL will tend to mask future responses to changes in individual inputs.

Modeling the Ecological Impact of Phosphorus in Catchments with Multiple Environmental Stressors

“…Seminatural land cover was estimated to be have a stronger positive influence on EQR TDI than the negative influence of either TP or SRP (Supplemental Tables S4.1, S5.1, S5.2, S6), and combined evidence from different modeling approaches shows that land cover had an overriding influence on the ecological response, which is in line with other studies that also found a hierarchy of stressors from land cover, followed by physicochemical (e.g., sediment and nutrient concentrations) and hydromorphological (e.g., river bed and riparian corridor characteristics) variables (Villeneuve et al, 2018). Here, seminatural land cover is likely acting as a proxy for other factors (Segurado et al, 2018), such as varying bioavailability of P fractions (Ellison and Brett, 2006; Prestigiacomo et al, 2016; Stutter et al, 2018), river morphology, riparian and/or aquatic habitat structure, and absence of toxic contaminants (e.g., herbicides). In addition, the bioavailability of P forms has been shown to vary between 12 and 73% for TP and between 6 and 81% for particulate P in catchments dominated by different land cover types (Ellison and Brett, 2006; Egemose and Jensen, 2009; Poirier et al, 2012; Baker et al, 2014).…”

“…In addition, the bioavailability of P forms has been shown to vary between 12 and 73% for TP and between 6 and 81% for particulate P in catchments dominated by different land cover types (Ellison and Brett, 2006; Egemose and Jensen, 2009; Poirier et al, 2012; Baker et al, 2014). Some land cover types, such as agriculture and urban land use, make TP more bioavailable (Ellison and Brett, 2006; Prestigiacomo et al, 2016), while TP from seminatural land cover is likely to be less bioavailable (Stutter et al, 2018). …”

Testing and application of a two-dimensional hydrothermal/transport model for a long, deep, and narrow lake with moderate Burger number

“…Nearly 40% of the total tributary inflow to the lake, as well as 3 point-source discharges, enter its southern end. Large quantities of sediment (Effler et al 2010), P (Prestigiacomo et al 2014), and dissolved color (Effler et al 2015) are delivered to the southern end of the lake by the tributaries during runoff events. A shallow region, designated "the shelf," with a maximum depth of 6 m extends 1.6 km from the southern end of the lake before a sharp drop-off in depth ( Fig.…”

Long-Term Study of Soluble Reactive Phosphorus Concentration in Fall Creek and Comparison to Northeastern Tributaries of Cayuga Lake, NY: Implications for Watershed Monitoring and Management

“…Cayuga Lake is the subject of a total maximum daily load (TMDL) development process resulting from phosphorus impairment to its southern shelf [20]. Movement of phosphorus in the watershed is runoff-driven, and approximately 95% percent of the bioavailable phosphorus load entering Cayuga Lake is nonpoint in origin [21]. High discharge periods produce most of the bioavailable phosphorus loading in the Fall Creek and Cayuga watersheds [22][23][24].…”

“…Historic monitoring has examined a diversity of Cayuga Lake's tributaries [32], but has largely focused on bigger tributaries that drain into the southern portion of the lake [21][22][23][24][25]. The motivation for major studies has included large scale undertakings, such as the Cornell lake source cooling project [33], and the ongoing TMDL development process that began in 2013 [20].…”