Management of the phosphorus-cladophora dynamic at a site on lake Ontario using a multi-module bioavailable P model

The filamentous green alga Cladophora grows to nuisance proportions in Lake Ontario. Stimulated by high phosphorus concentrations, nuisance growth results in the degradation of beaches and clogging of industrial water intakes with attendant loss of beneficial uses. We develop a multi-module bioavailable phosphorus model to examine the efficacy of phosphorus management strategies in mitigating nuisance algal growth. The model platform includes modules simulating hydrodynamics (FVCOM), phosphorus-phytoplankton dynamics (GEM) and Cladophora growth (GLCMv3). The model is applied along a 25 km stretch of the Lake Ontario nearshore, extending east from Toronto, ON and receiving effluent from three wastewater treatment plants. Simulation results identify the Duffin Creek wastewater treatment plant effluent as a driving force for nuisance conditions of Cladophora growth, as reflected in effluent bioavailable phosphorus concentrations and the dimensions of the plant’s phosphorus footprint. Simulation results demonstrate that phosphorus removal by chemically enhanced secondary treatment is insufficient to provide relief from nuisance conditions. Tertiary treatment (chemically enhanced secondary treatment with ballasted flocculation) is shown to eliminate phosphorus-saturated conditions associated with the Duffin Creek wastewater treatment plant effluent, providing local relief from nuisance conditions. Management guidance presented here has wider application at sites along the highly urbanized Canadian nearshore of Lake Ontario

Management transition to the Great Lakes nearshore: Insights from hydrodynamic modeling

The emerging shift in Great Lakes management from offshore to nearshore waters will require attention to complexities of coastal hydrodynamics and biogeochemical transformations. Emphasizing hydrodynamics, this work resolves transport processes in quantifying discharge plume and pollutant of concern (POC) footprint dimensions, the latter being the portion of the plume where water quality standards are not met. A generic approach, isolated from pollutant-specific biokinetics, provides first-approximation estimates of the footprint area. A high-resolution, linked hydrodynamic-tracer model is applied at a site in the Greater Toronto Area on Lake Ontario. Model results agree with observed meteorological and hydrodynamic conditions and satisfactorily simulate plume dimensions. Footprints are examined in the context of guidelines for regulatory mixing zone size and attendant loss of beneficial use. We demonstrate that the ratio of the water quality standard to the POC concentration at discharge is a key determinant of footprint dimensions. Footprint size for traditional pollutants (ammonia, total phosphorus) meets regulatory guidelines; however, that for soluble reactive phosphorus, a presently unattended pollutant, is ~1–2 orders of magnitude larger. This suggests that it may be necessary to upgrade treatment technologies to maintain consistency with regulatory guidelines and mitigate manifestations of the eutrophication-related soluble reactive phosphorus POC

TOWARD A NEW MODELING APPROACH FOR MANAGEMENT OF NUISANCE CLADOPHORA GROWTH IN THE GREAT LAKES

Cladophora glomerata, a filamentous green alga that grows on hard substrate, first started to attract significant attention in the mid-1970s, when the species spread in Lakes Huron, Erie, and Ontario. High concentrations of soluble reactive phosphorus in discharges led to increased Cladophora growth, which impaired beaches, ecosystem services, and water intakes. The Great Lakes Water Quality Agreement of 1972 (amended in 1978) presumably helped curb the algal proliferation by setting phosphorus limits for any discharges to the Great Lakes. The scientific literature indicates success in this management strategy as measured maximum biomass values decreased. Recent studies, however, show that – while phosphorus limitations are still in effect – Cladophora has returned, and at greater depths. The introduction and establishment of invasive zebra and quagga mussels (Dreissena polymorpha and Dreissena rostriformis bugensis) to the Great Lakes in the late 1980s to early 1990s cause perturbations in the light environment that lead to favorable conditions for Cladophora. This dissertation first investigates the potential drivers of the Cladophora resurgence by comparing historical data and conducting a modeling exercise that – for the first time – quantifies the effect of each driving force on the Cladophora resurgence (Chapter 2). In the spirit of monitoring and analyzing existing data, this section establishes that the Cladophora resurgence is not only perceived but real and that changes in light conditions following the invasion of dreissenids allow for renewed algal proliferation. Chapter 3 of this work describes the development, calibration, and confirmation of a hydrodynamic model, which is applied to describe mass transport in the nearshore of northern Lake Ontario. This work is in response the Great Lakes Water Quality Protocol of 2012, which recognizes that a whole-lake (offshore) approach to controlling nuisance algal growth will not be effective where effluent and tributary discharges are received immediately and locally in the nearshore. Chapter 4 focuses on the development, calibration, and confirmation of the Great Lakes Cladophora Model version 3 (GLCM v3), which includes several improvements of the previous version of the GLCM: redefined light/temperature rate of photosynthesis and respiration response curves, inclusion of a growth-inhibiting self-shading term, a newly defined relationship between the phosphorus uptake rate and stored phosphorus content, replacement of the Droop relationship between the rate of photosynthesis and stored phosphorus content with a similar relationship based on experimental results, and treatment of self-shading and sloughing for an improved understanding and algorithm describing those processes. The GLCM v3 will serve to set a phosphorus standard specific to managing Cladophora, an ecosystem objective that has never been quantitatively defined before

The canopy effect in filamentous algae: Improved modeling of Cladophora growth via a mechanistic representation of self-shading

For decades, nuisance algal growth has wreaked havoc in systems across the world. It has been particularly problematic in the Laurentian Great Lakes. Although managing nutrient loads has resulted in some mitigation, ecosystem perturbations in the last two decades have resulted in favorable conditions for a Cladophora resurgence. This paper reports on improvements to the Great Lakes Cladophora Model, which has been used to inform management of Great Lakes nuisance algal growth since it was first developed over 30 years ago (Auer et al., 1982; Auer and Canale, 1982; Canale and Auer, 1982a,b). Like earlier versions, this recent configuration of the model, GLCM v3, simulates algal biomass density (g dry mass m−2) and stored (or cellular) phosphorus content (P as % dry mass) over the spring, summer and fall growth cycle. Two major advances over previous versions of the model are presented: a) an improved characterization of the light and temperature response surfaces driving gross growth and respiration and b) the development and implementation of a segmented-system (canopy) approach for simulating the impact of self-shading (carrying capacity) on growth. Prior versions of the GLCM treated the algal mat as a lumped system, utilizing the logistic model to simulate the carrying capacity effect. In that approach, a carrying capacity coefficient (Xmax, maximum biomass density) placed a ceiling on biomass accrual. However, that approach was not mechanistic (i.e., physiologically supported) and empirical specification of the coefficient is undermined by significant intra- and inter-site variability. This uncertainty places too much emphasis on Xmax as a tuning parameter. The signal contribution of this work to the development of the GLCM v3 is the replacement of the lumped system approach with a vertically segmented, mechanistic treatment of self-shading: the “canopy effect.” Here, biomass accrual is mechanistically governed by light attenuation through the canopy as quantified by kalg, the vertical extinction coefficient for light passing through the mat. This coefficient may be determined by direct, in situ measurement and offers much less freedom for use as a tuning parameter. The advances in Cladophora growth modeling provided here and embodied in the GLCM v3 offer a more mechanistic and robust tool than previous versions, strengthening its credibility for the management of nuisance algal growth such as that mandated by the Great Lakes Water Quality Agreement of 2012. Further, the vertical determination of net growth provides a more mechanistic basis for future modeling of other key processes such as sloughing (detachment) in both the Great Lakes and other natural waterbodies

Determination of bioavailable phosphorus in water samples using bioassay methods.

The total phosphorus analyte (TP) has a long history of use in monitoring and regulatory applications relating to management of cultural eutrophication in freshwaters. It has become apparent, however, that the fraction of the TP analyte ultimately available to support algal growth varies significantly spatially (within a system), seasonally, and among systems. The algal bioassay methods described here provide an approach for determining the bioavailable fraction of the three operationally defined components of TP: soluble reactive phosphorus (SRP), dissolved organic phosphorus (DOP), and particulate phosphorus (PP) in effluents and tributaries discharging to lakes and reservoirs. Application of the technique facilitates a quantitative ranking and targeting of bioavailable phosphorus sources for management.•One congruent method to fractionate particulate and soluble phosphorus (found in aquatic samples) into bioavailable and unavailable fractions was developed based on compilation, adaptation and expansion of two methods from the late 1970s and early 1980s.•Detailed descriptions for culturing phosphorus-starved algae, sub-sampling schedules, kinetics determination, and data presentation are provided•Reproducibility is demonstrated by replication and closure of a mass balance on phosphorus

Management of the Phosphorus–Cladophora Dynamic at a Site on Lake Ontario Using a Multi-Module Bioavailable P Model

The filamentous green alga Cladophora grows to nuisance proportions in Lake Ontario. Stimulated by high phosphorus concentrations, nuisance growth results in the degradation of beaches and clogging of industrial water intakes with attendant loss of beneficial uses. We develop a multi-module bioavailable phosphorus model to examine the efficacy of phosphorus management strategies in mitigating nuisance algal growth. The model platform includes modules simulating hydrodynamics (FVCOM), phosphorus-phytoplankton dynamics (GEM) and Cladophora growth (GLCMv3). The model is applied along a 25 km stretch of the Lake Ontario nearshore, extending east from Toronto, ON and receiving effluent from three wastewater treatment plants. Simulation results identify the Duffin Creek wastewater treatment plant effluent as a driving force for nuisance conditions of Cladophora growth, as reflected in effluent bioavailable phosphorus concentrations and the dimensions of the plant’s phosphorus footprint. Simulation results demonstrate that phosphorus removal by chemically enhanced secondary treatment is insufficient to provide relief from nuisance conditions. Tertiary treatment (chemically enhanced secondary treatment with ballasted flocculation) is shown to eliminate phosphorus-saturated conditions associated with the Duffin Creek wastewater treatment plant effluent, providing local relief from nuisance conditions. Management guidance presented here has wider application at sites along the highly urbanized Canadian nearshore of Lake Ontario

The Cladophora resurgence in Lake Ontario: characterization and implications for management

Nuisance growth of the alga Cladophora, reported from Lake Ontario since the 1930s, abated in the decades following implementation of phosphorus control measures in the 1970s. Our examination of beach fouling records and historical observations of algal biomass has confirmed literature reports that a resurgence in nuisance growth of Cladophora has occurred since invasion of Great Lakes waters by dreissenids. Our findings indicate that the growth rate of Cladophora(specific rate of net photosynthesis) has decreased by 44% since 1972 in response to phosphorus controls. However, improved transparency, a response to mussel activity, has increased the maximum depth colonizable by Cladophora by a factor of 5 over that same interval. The net result is a sixfold increase in production potential since the late 1980s (the Post-P Management II Period) and a threefold increase since the 1970s (the Pre-P Management Period). Although the Cladophora resurgence has been driven by dreissenid modification of the light environment, phosphorus management remains the only alternative for reversing and ameliorating nuisance conditions. Elucidation of the nature of the Cladophora resurgence will aid decision-makers in maintaining a focus on phosphorus management as the appropriate means of remediating nuisance growth of the alga

Management Transition to the Great Lakes Nearshore: Insights from Hydrodynamic Modeling

The emerging shift in Great Lakes management from offshore to nearshore waters will require attention to complexities of coastal hydrodynamics and biogeochemical transformations. Emphasizing hydrodynamics, this work resolves transport processes in quantifying discharge plume and pollutant of concern (POC) footprint dimensions, the latter being the portion of the plume where water quality standards are not met. A generic approach, isolated from pollutant-specific biokinetics, provides first-approximation estimates of the footprint area. A high-resolution, linked hydrodynamic-tracer model is applied at a site in the Greater Toronto Area on Lake Ontario. Model results agree with observed meteorological and hydrodynamic conditions and satisfactorily simulate plume dimensions. Footprints are examined in the context of guidelines for regulatory mixing zone size and attendant loss of beneficial use. We demonstrate that the ratio of the water quality standard to the POC concentration at discharge is a key determinant of footprint dimensions. Footprint size for traditional pollutants (ammonia, total phosphorus) meets regulatory guidelines; however, that for soluble reactive phosphorus, a presently unattended pollutant, is ~1−2 orders of magnitude larger. This suggests that it may be necessary to upgrade treatment technologies to maintain consistency with regulatory guidelines and mitigate manifestations of the eutrophication-related soluble reactive phosphorus POC

Keeping up with the math: Advancing the ecological foundation of the Great Lakes Cladophora Model

The nearshore waters of the Laurentian Great Lakes have historically suffered from beach fouling and clogged water intakes due to proliferation of the native, filamentous green alga Cladophora. A resurgence in nuisance growth of the alga has led to a demand for an improved model platform to better guide management. The Great Lakes Cladophora model (GLCM v3) predicts algal biomass (g dry matter m−2) and stored phosphorus content (P as % of dry matter) based on simulations forced by time series of incident light (I), water temperature (T) and water column soluble reactive phosphorus concentration (SRP, μgP L-1). A particular strength of the GLCM v3 is its foundation in ecologically sound biokinetic mechanisms, supported by field and laboratory measurements. These measurements, advancing the credibility and reliability of the biokinetic framework, include improved characterization of the growth and respiration responses to light and temperature, addition of a self-shading algorithm replacing an overly deterministic carrying capacity term, a new treatment of phosphorus uptake based on radioisotope experiments, additional observational support for Droop-based simulation of growth as a function of stored P, and implementation of a new physiologically and physically driven sloughing function. Uncertainty associated with processes collectively termed “environmental friction” (the I, T, and P growth forcing functions) is reduced, leaving the model sensitive to the maximum specific growth rate and the coefficient for extinction of photosynthetically active radiation through the algal mat. The model was performance tested by multi-lake (Erie, Huron, Ontario, and Michigan) calibration employing a common set of biophysical coefficients. This common set of calibration coefficients provides enhanced corroboration that GLCM v3 is suitable for examining the phosphorus–Cladophora dynamic across the Great Lakes. In particular, it greatly strengthens the model\u27s efficacy for establishing a phosphorus standard to maintain levels of algal biomass below those constituting a nuisance condition, as per the Great Lakes Water Quality Agreement of 2012. In addition, the model structure can be applied to other lakes experiencing problems with attached filamentous algae

Dissolved phosphorus concentrations in Cayuga Lake system and differences from two analytical protocols

© 2016, © Copyright by the North American Lake Management Society. Effler SW, Prestigiacomo AR, Hairston NG, Auer MT, Kuczynski A, Chapra SC. 2016. Dissolved phosphorus concentrations in Cayuga Lake system and differences from two analytical protocols. Lake Reserve Manage. 32:392–401. Differences in the concentrations of dissolved forms of phosphorus (P) measured with 2 widely used spectral protocols were documented and evaluated for Cayuga Lake, New York, and 4 of its primary tributaries. The analysis focuses on 2 operationally defined forms of dissolved P, soluble reactive P (SRP) and soluble unreactive P (SUP), which together constitute dissolved P (TDP). Direct comparisons were based on analysis of the results from the 2 protocols of split samples of year-round deep water representative of the entire water column during turnover and the respective dependencies of tributary concentrations on stream flow. Although the TDP concentrations converged for the 2 protocols, there were systematic differences for the contributions of SRP versus SUP (i.e., one protocol yielding lower SRP but higher SUP). The interpretive implications of the differences in the operationally defined concentrations from the 2 analytical protocols were considered in the context of common limnological and bioavailable paradigms for these forms of P, and the needs and structures of mechanistic P-eutrophication models. The lower SRP analytical protocol was favored because of its greater consistencies with the independent bioavailability results, limnological paradigms for dissolved forms of P, and contemporary mechanistic modeling. The differences between the 2 protocols are particularly problematic where contemporary mechanistic models are to be applied, requiring compensating differences in kinetic representations, and likely structure, for cases of higher SRP datasets attributable to the protocol