Partitioning the contributions of minerogenic particles and bioseston to particulate phosphorus and turbidity

Protocols to partition the contributions of bioseston and minerogenic particles to turbidity (T n ) and particulate phosphorus (PP), as described by summations of the 2 components, are developed, tested, and applied. The analysis is based on coincident observations of T n , PP, chlorophyll a (Chl), and the summation of the projected areas of individual minerogenic particles per unit volume (PAV m ) for the wide variations encountered in time and between near-shore and pelagic sites over an 8-year study of Cayuga Lake, New York. PAVm was determined from an individual particle analysis technique, scanning electron microscopy interfaced with automated image, and X-ray analyses (SAX). The partitionings are based on a stoichiometric approach that adopts Chl and PAVm as the metrics of bioseston and minerogenic particles, respectively, and estimates developed here for stoichiometric ratios that relate Tn and PP to these 2 components. The systematically higher T n and PP levels at the near-shore site, particularly following runoff events, are demonstrated to be a result of elevated PAV m associated with allochthonous inputs. A reasonably good match of the partitioned 2-component summations with bulk observations is reported. Application of the 2-component PP model establishes minerogenic particles made, on average, noteworthy (~10%) to substantial (≥20%) contributions to PP. The minerogenic particle component of PP was largely responsible for the greater summer average total phosphorus (TP) concentrations at the near-shore versus the pelagic site, the interannual variations in the differences between these sites, and exceedance of the TP water quality limit at the near-shore site. Minerogenic particles were the dominant component of T n , a finding that is demonstrated to be consistent with optical theory, based on the much greater efficiency of side-scattering for minerogenic versus organic particles.