Steven W. Effler

Apportionment of bioavailable phosphorus loads entering Cayuga Lake, New York

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 lakes 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.

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

Abstract Protocols to partition the contributions of bioseston and minerogenic particles to turbidity (Tn) 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 Tn, PP, chlorophyll a (Chl), and the summation of the projected areas of individual minerogenic particles per unit volume (PAVm) 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 Tn and PP levels at the near-shore site, particularly following runoff events, are demonstrated to be a result of elevated PAVm 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 Tn, 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.

Phytoplankton absorption and the chlorophyll a–specific absorption coefficient in dynamic Onondaga Lake

Abstract Phytoplankton absorption and its dependence on the concentration of chlorophyll a(Chl-a), as represented by the Chl-a–specific absorption coefficient (a*φ(λ)), is important to support models of growth and for bio-optical remote sensing algorithms to retrieve Chl-a. The dynamics of the phytoplankton absorption coefficient (aφ(λ)) and a*φ(λ), and their dependencies on Chl-a, are described for Onondaga Lake, New York, over a 6-year period for which major changes in trophic state, Chl-a, and community composition occurred. Strong positive dependencies of aφ(λ) on Chl-aare reported for absorption peaks in both the blue and red spectral regions that are qualitatively similar to relationships for ocean waters but differ quantitatively. Average values of a*φ at wavelengths of 440 and 676 nm were 0.0347 and 0.0171 m2 mg−1, respectively, with coefficients of variation of 37 and 31%. Significant negative relationships between a*φ and Chl-a were observed for blue and green wavelengths that were qualitatively consistent with the influences of pigment packaging and the contribution of accessory pigments to absorption. The operation of these influences is demonstrated through various forms of data analysis that resolved the following significant relationships: (1) negative dependence of the ratio aφ(440):aφ(676) on Chl-a; (2) flattening of aφ spectra in the blue and increases at the red maximum, with increases in Chl-a; and (3) negative dependence of aφ(490):aφ(676) on Chl-a. Values of a*φ(440) and a*φ(676) obtained for Onondaga Lake are considered in the context of the limited population reported for other inland waters and selected marine systems.

Characterizations and modeling of turbidity in a water supply reservoir following an extreme runoff event

Abstract The findings from an integrated program of short- and long-term monitoring, individual particle analyses (IPA), and mechanistic modeling to characterize and simulate the turbidity (Tn) effects of an extreme runoff event (2011) on a water supply reservoir were documented. A robotic profiling platform and rapid profiling instrumentation resolved turbidity and temperature (T) patterns in time and space in the reservoir. Metalimnetic enrichment in Tn following the event was reported and attributed to the entry of turbid stream water as density currents, or plunging inflows. The diminishment of high Tn levels following the event was well represented by a first-order loss rate of about 0.023 d−1. The highest Tn levels were avoided in water withdrawn for the water supply following the event by selection of vertical intake alternatives, although Tn values in the withdrawal remained distinctly above typical baseline conditions for nearly 2 months. Based on IPA, the Tn-causing particles were mostly clay minerals in the 1–20 μm size range. The operation of sorting processes determining settling losses from the minerogenic particle population, according to their size and shape, following the runoff event was resolved. The set-up and testing of a mechanistic Tn model, composed of 2 submodels, a 2-dimensional hydrothermal/transport submodel, and a Tn kinetics submodel, is described. The hydrothermal/transport submodel was tested separately and performed well in simulating the dynamics of the reservoir’s stratification regime and the entry of the dense streams as plunging inflows during the extreme runoff event. The overall Tn model needed to represent the loss processes of both settling and coagulation to perform well in simulating the in-reservoir and withdrawal Tn patterns following the runoff event.

Calibration and application of a sediment accumulation rate model - a case study

Abstract A mechanistic mass balance model for sediment accumulation rate (SAR) that accommodates the dry density and burial velocity of solids and the depth dependency of porosity was tested and applied to Onondaga Lake, New York, for a 130-year period. The modeling for this case study is supported by a rich history of multiple anthropogenic drivers and coupled date horizons from the paleolimnological record, characterization of physical attributes of the sediments, and long-term monitoring of the water column and lake inputs. The consistency of predictions of SAR and measurements of downward flux of suspended particulate material (DFSPM) from a long-term sediment trap program was also evaluated. The model was demonstrated to perform well in simulating the lake’s history of SAR, which was supported by 10 different depth–date horizons. This history for 100 years was regulated by the production of soda-ash at an adjoining industry, which enhanced autochthonous formation and deposition of calcium carbonate (CaCO3), proportional to the level of production of this chemical. The SAR was extraordinarily high (~5 kg m−2 yr−1) during the 40 years of peak soda-ash production. An abrupt, more than 2-fold decrease in SAR occurred when the industry closed. The contemporary SAR remains relatively high as a result of multiple drivers but is serving to enhance burial of contaminants, including mercury, as part of an ongoing rehabilitation program. A high level of consistency (within 30%) between the contemporary SAR and an annual estimate of DFSPM was documented. The utility of the model was demonstrated through applications that depict the amount of deposits contributed by the industry, the effect of compaction on burial velocity, the dilution effect of the high SAR values on the paleolimnological record, and the resolution of sediment diagenesis kinetics.

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

Abstract Setup, testing, and application of a 2-dimensional longitudinal–vertical hydrothermal/transport model (the transport submodel of CE-QUAL-W2) was documented for Cayuga Lake, New York, where the Rossby radius is on the order of the lake’s width. The model was supported by long-term monitoring of meteorological and hydrologic drivers and calibrated and validated using in-lake temperature measurements made at multiple temporal and spatial scales over 16 years. Measurements included (1) temperature profiles at multiple lake sites for 10 years, (2) near-surface temperatures at one end of the lake for 16 years, (3) high frequency temperature at multiple depths for 2 years, and (4) seasonal measurements of a conservative passive tracer. Seiche activity imparted prominent signatures within these measurements. The model demonstrated excellent temporal stability, maintaining good performance in uninterrupted simulations over a period of 15 years. Performance was improved when modeling was supported by on-lake versus land-based meteorological measurements. The validated model was applied through numeric tracer experiments to evaluate various features of transport of interest to water quality issues for the lake, including (1) residence times of stream inputs within the entire lake and a smaller region defined bathymetrically as a shallow shelf, (2) transport and fate of negatively buoyant streams, and (3) the extent of transport from the hypolimnion to the epilimnion. This hydrothermal/transport model is appropriate to serve as the transport submodel for a forthcoming water quality model for this lake and for other high aspect (length to width) ratio lacustrine systems for which the internal Burger number is order one or greater.Setup, testing, and application of a 2-dimensional longitudinal–vertical hydrothermal/transport model (the transport submodel of CE-QUAL-W2) was documented for Cayuga Lake, New York, where the Rossby radius is on the order of the lake’s width. The model was supported by long-term monitoring of meteorological and hydrologic drivers and calibrated and validated using in-lake temperature measurements made at multiple temporal and spatial scales over 16 years. Measurements included (1) temperature profiles at multiple lake sites for 10 years, (2) near-surface temperatures at one end of the lake for 16 years, (3) high frequency temperature at multiple depths for 2 years, and (4) seasonal measurements of a conservative passive tracer. Seiche activity imparted prominent signatures within these measurements. The model demonstrated excellent temporal stability, maintaining good performance in uninterrupted simulations over a period of 15 years. Performance was improved when modeling was supported by on-lake versus land-based meteorological measurements. The validated model was applied through numeric tracer experiments to evaluate various features of transport of interest to water quality issues for the lake, including (1) residence times of stream inputs within the entire lake and a smaller region defined bathymetrically as a shallow shelf, (2) transport and fate of negatively buoyant streams, and (3) the extent of transport from the hypolimnion to the epilimnion. This hydrothermal/transport model is appropriate to serve as the transport submodel for a forthcoming water quality model for this lake and for other high aspect (length to width) ratio lacustrine systems for which the internal Burger number is order one or greater.

Quantifications and water quality implications of minerogenic particles in Cayuga Lake, New York, and its tributaries

Abstract An individual particle analysis technique, scanning electron microscopy interfaced with automated image and X-ray analyses (SAX), was applied to characterize the minerogenic particle populations of Cayuga Lake (New York) and its primary tributaries and quantify their effects on common water quality metrics. The primary summary metric of SAX results is demonstrated to be the total projected area of minerogenic particles per unit volume of water (PAVm). PAVm is documented to be linearly related to the minerogenic components of particulate phosphorus (PPm), turbidity (Tn/m), and the light scattering coefficient, and inversely related to Secchi depth (SD). SAX is demonstrated to support partitioning of PAVm into contributions of multiple size and geochemical classes. Clay mineral particles dominated in the tributaries and the lake, although they shifted somewhat to smaller sizes (1–15 μm) in the lake. Levels of PAVm were higher in a lake area that adjoins the tributary inputs than in pelagic waters, particularly after runoff events. This increased PAVm degraded water quality, including higher PPm and Tn/m and lower SD relative to the pelagic waters, although diminished (still recognizable) signatures are documented lake-wide. Advantages of SAX over gravimetric analyses for the minerogenic particle populations of lakes include (1) improved analytical performance, (2) insights from the more robust size and composition information, (3) theoretical advantages for optical impacts, and (4) stronger relationships with water quality metrics.

Linking CDOM patterns in Cayuga Lake, New York, USA, to terrigenous inputs

Abstract Lacustrine patterns of the light absorption of colored dissolved organic matter (aCDOM) and its composition proxies were resolved and linked to concurrent conditions of tributary inputs for Cayuga Lake, New York. We analyzed fixed-frequency samples of the lake at 3 sites and runoff event-based samples at the mouths of 3 gauged tributaries over a 7 month interval and measured dissolved organic carbon (DOC) and aCDOM over the visible wavelengths (400–700 nm) and at 254 nm. The tributaries are demonstrated to be enriched in aCDOM and DOC, with widely different proxy conditions compared to the lake, which further diverge during runoff events. DOC, aCDOM, and the composition proxies for the tributaries had significant, and mostly strong, dependencies on flow rate, described by power-law relationships. The differences in the composition proxies indicated lower contributions of CDOM to the DOC pool, reduced aromaticity, decreased molecular size of CDOM, and decreased amounts of humic versus fulvic acids in the lake compared to the tributaries, all accepted signatures of photobleaching. Dynamics of aCDOM in the upper waters of the lake depended primarily on composition (e.g., color quality) and secondarily on a quantity metric (DOC), as demonstrated in a 2-component linear least-squares regression format. Signatures of linkages between the terrestrial inputs and in-lake aCDOM patterns and the effects of photobleaching include (1) the preferential in-lake loss of aCDOM relative to DOC, estimated from budget calculations; (2) the intermediate characteristics resolved at a near-shore site adjoining multiple tributary inflows; and (3) the magnitude and charactero f the dynamics observed at the pelagic sites.

Optical characterization and tests of closure for Oneida Lake, New York, U.S.A.

Abstract Optical characteristics are a central feature of water quality and are increasingly used as a basis for monitoring concentrations of optically active constituents (OACs) through satellite-based remote sensing. This study presents a robust optical characterization of the near-surface waters of eutrophic Oneida Lake, New York, USA, that features in situ spectral measurements of inherent optical properties (IOPs) and remote sensing reflectance (Rrs(λ)), an apparent optical property (AOP) critical to remote sensing initiatives. The IOP measurements included the absorption coefficient, (a(λ)), and particulate scattering (bp(λ)) and backscattering (bbp(λ)) coefficients. Supporting measurements included Secchi depth (SD), the OACs, chlorophyll a, phycocyanin, suspended particulate material, and laboratory determinations of components of a(λ) (ax(λ)), including colored dissolved organic matter, nonalgal particles, and phytoplankton. The strong spectral patterns of a, ax, and Rrs, and more modest wavelength dependencies of bp and bbp, are documented. The credibility of the optical characterizations is demonstrated through (1) the consistency of relationships between SD−1 and bp, and ax and the OACs; (2) the extent of closure between in situ and laboratory measurements of a and ax; and (3) the extent of closure between predicted Rrs spectra, based on the observed IOP (a and bbp) spectra and application of a widely used radiative transfer relationship, and observations. Major temporal and substantial spatial variations in OACs, IOPs, SD, and Rrs(λ) are documented. Much of the variability in the OACs and SD were well predicted by system-specific empirical relationships that used Rrs values at specified wavelengths (consistent with the Medium Resolution Imaging Spectrophotometer [MERIS]) as the independent variables, supporting the potential for effective monitoring of these features through remote sensing in the future.

Daphnia grazing, the clear water phase, and implications of minerogenic particles in Onondaga Lake

Abstract We evaluated the influence of Daphnia grazing on water clarity in Onondaga Lake, New York, by testing 2 related hypotheses: (1) that the high clarity (Secchi disk depth [SD]) events observed in 18 years of a 27-year record were occurrences of the clear water phase (CWP) associated with elevated levels of Daphnia grazing, and (2) that reductions in minerogenic (i.e., inorganic) particle concentrations and the accompanying reductions in light scattering (quantified by bm) due to grazing contributed importantly to the SD signatures of the CWPs. Our analysis is based on a 27-year record of the Daphnia population, SD, and the concentration of chlorophyll a (Chl-a), as well as shorter-term characterizations of minerogenic particle concentrations in the lake and application of an optical theory-based SD model previously tested for the lake. The first hypothesis is supported by (a) the consistency of seasonal patterns of Chl-a, SD, and Daphnia biomass, (b) the consistency of Daphnia biomass maxima with literature values associated with the CWP, (c) the positive relationships demonstrated between interannual differences in Daphnia biomass (and estimated grazing rates) and peak SD and duration of high clarity events, and (d) because during CWPs, estimated grazing rates exceed by a wide margin reasonable maximum values of phytoplankton growth rates. The second hypothesis is supported by (a) demonstration that the minerogenic particle sizes responsible for bm (and so its influence on SD) are within the size range subject to Daphnia grazing, and (b) application of the SD model, in the context of SD and Chl-a observations, showing that a reduction in bm is necessary to explain the high SD values observed during CWPs. Finally, a review of the growing literature on the contribution of bm to the overall particle scattering coefficient in various lakes suggests that minerogenic particles are often important to the SD signature of CWPs.