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's 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.

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.

Stimulated by excess levels of phosphorus, the attached, filamentous green alga Cladophora grows to nuisance proportions in Lake Michigan, one of the Laurentian Great Lakes. While nearshore waters impacted by local sources of the nutrient continue to support nuisance conditions, offshore waters have undergone oligotrophication in response to reductions in phosphorus loading and benthification of phosphorus cycling by invasive dreissenid mussels. A concept termed the Dual Challenge recognizes that implementation of more stringent phosphorus-loading objectives (to control Cladophora in the nearshore) stands in conflict with a foreseen need to mitigate oligotrophication in the offshore (to sustain a healthy fishery). Attention to this nearshore–offshore dynamic calls into play the role of cross-margin phosphorus transport in mediating both endmembers of the conflict. We applied a biophysical model simulating soluble reactive (SRP) and particulate (PP) phosphorus, mussel biokinetics, and cross-margin mass transport in addressing the Dual Challenge. Pre- and post-dreissenid monitoring results suggest that a reduction in offshore PP levels (food web nutrition) in excess of 40% (2.4 to 1.4 mgP·m−3) has driven oligotrophication and attendant food web dysfunction. Yet, in the absence of local sources, model-predicted nearshore SRP levels remain at or below those required to prevent nuisance growth. These findings indicate that there is a margin of ~1 mgP·m−3 over which offshore PP levels could be increased (to the benefit of the food web and the fishery) without hindering efforts to reduce nuisance algal growth through local source control.

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.

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 (X-max, 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 X-max 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 k(alg), 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.

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.

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 ( BAP L ) are minor (5%), reflecting the benefit of reductions from recent treatment upgrades. The BAP L represented only about 26% of the total P load, because of the large contribution of the low bioavailable PP component. Most of BAP L (>70%) is received during high flow intervals. Large interannual variations in tributary flow and coupled BAP L will tend to mask future responses to changes in individual inputs.

Phosphorus (P) associated with minerogenic particles delivered from watersheds can interfere with the common use of total P (TP) concentration as a trophic state metric in lacustrine systems, particularly proximate to tributary entries, because of its limited bioavailability. The concentration of unavailable minerogenic particulate P (PP m/u ), where it is noteworthy, should be subtracted from TP in considering primary production potential and trophic state levels. A first mass balance model for PP m/u is developed and tested here for Cayuga Lake, New York. This is supported by a rare combination of detailed information for minerogenic particle level dynamics for the tributaries and lake, the bioavailability of tributary particulate P (PP), and previously tested hydrothermal/transport and minerogenic particle concentration submodels. The central roles of major runoff events and localized tributary loading at one end of the lake in driving patterns of PP m/u in time and space are well simulated, including (1) the higher PP m/u concentrations in a shallow area (“shelf”) adjoining the inputs, relative to pelagic waters, following runoff events, and (2) the positive dependence of the shelf increases on the magnitude of the event. The PP m/u component of P was largely responsible for the higher summer average TP on the shelf vs. pelagic waters and the exceedance of a TP water quality limit on the shelf. The effective simulation of PP m/u allows an appropriate adjustment of TP values to avoid overrepresentation of potential primary production levels.

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.

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.

Forty-seven polychlorinated biphenyls (PCBs), 9 polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBPA) and its mono-, di- and tri-bromo-analogs, and bisphenol A (BPA) were investigated in sediments (56 samples; collected in spring 2004) from the western, central and eastern basins of Lake Erie. Surficial (0–10 cm) sediment from the western basin contained significantly greater (p < 0.05) concentrations of ΣPCBs, ΣPBDEs and BPA than the other two basins. Σ47PCBs were 144 ± 141, 33 ± 34, and 13 ± 15 ng/g (mean ± standard deviation (SD); dry weight, d.w.) in the western, central, and eastern basins respectively. For two of the surveyed sites, the Σ47PCBs in sediment exceeded the Canadian sediment quality probable effect level of exposure guideline (PEL, 277 ng/g) for aquatic biota, indicating a risk to biota health in 2004. Σ8PBDE concentrations (BDE-28, -47, -99, -100, -138, -153, -154 and -183) were 1.33 ± 2.54, 0.17 ± 0.11, and 0.30 ± 0.38 ng/g (mean ± SD; d.w.) in the western, central, and eastern basins, respectively. BDE-209 was the predominant PBDE congener in sediment samples, and was quantifiable in 56% of the samples with a concentration range of < 0.3 to 12 ng/g (d.w.). BPA concentrations up to 6.1 ng/g (d.w.) were detected in 65% of the samples. For these chemicals, the Detroit River outflow is strongly suggested to be the major source/vector for Lake Erie. TBBPA was detectable in one sample (0.5 ng/g d.w.) from a site near the Detroit River, suggesting degradation and/or a low level deposition of polybrominated-BPAs to Lake Erie.

The development of a vertically-segmented, mechanistic mass balance model (Sed2K) for particulate organic matter (POM) diagenesis in lake sediments is described. The model is parsimonious in its requirements for input data and versatile in its accommodation of kinetic formulations. An application is provided for hypereutrophic Lake Alice, Minnesota, which includes a well-constrained calibration to downcore POM constituents (carbon, nitrogen, and phosphorus) and their efflux at the sediment-water interface. The application then considers the system response to a reduction in POM deposition to the sediments (i.e., addressing the critical “when and to what extent” question fundamental to lake restoration programs).

Within the Lake Superior benthic macroinvertebrate community, Diporeia spp. are the most abundant organisms and account for the largest proportion of biomass. As detritivores that feed on organic material in surficial sediments, Diporeia play a major role in transferring energy and nutrients to higher trophic level consumers and are favored prey for Lake Whitefish and other benthivorous fish species. The objective of this study is to quantify and model the response of the Diporeia consumption rate to changes in food availability. Diporeia were introduced to microcosms containing various concentrations of 14C-labeled green algae (Selenastrum capricornutum) and incubated for 24hours. Consumption was calculated as the radioisotope content of each animal divided by the specific activity of the labeled algae. A hyperbolic (Michaelis–Menten) function was fit to the data, yielding a maximum consumption rate of 1.76±0.4 SE mg C/g DW/d. The predicted consumption rate corresponding to average Lake Superior algal carbon fluxes was 0.08±0.15mg C/g DW/d. For the observed range of carbon fluxes to benthic habitats in the Great Lakes, the relationship between consumption and food supply is well described by a linear function, with consumption rates ranging from 0.08–0.38mg C/g DW/d. The parameter estimates presented here may act as inputs for a bioenergetics model used to predict Diporeia growth and production in Lake Superior.

Phosphorus (P) concentrations in the open waters of Lake Ontario have been reduced markedly through load management. Yet, nuisance growth of Cladophora persists in the nearshore where urban P inputs are received. Elimination of nuisance conditions will require application of more effective phosphorus treatment technologies with particular attention to phosphorus bioavailability. One such technology, ballasted flocculation, was implemented in 2005 at the Metropolitan Syracuse Wastewater Treatment Plant (Metro) in Syracuse, NY which discharges 68 MGD (257 MLD, million liters per day) to Lake Ontario via the Seneca–Oneida–Oswego River system. Wet chemistry measurements and soluble- and particulate-phase bioassays of phosphorus bioavailability are used here in assessing the efficacy of the technology. Effluent total (TP) and soluble reactive (SRP) phosphorus concentrations using ballasted flocculation technology over the period 2005–2012 averaged 86 and 3μg P/L, respectively, and the effluent BAP (bioavailable phosphorus) concentration was 10μg P/L. In operation now for a decade, Metro has reduced its effluent total phosphorus by 86%, soluble reactive phosphorus by 99% and bioavailable phosphorus by 97% compared with the conventional chemical treatment used previously (iron salts and gravity clarification). The reduction in BAP was accomplished through direct removal of the SRP, dissolved organic (DOP) and particulate (PP) phosphorus fractions, but also by reducing the bioavailability of DOP and PP. Retrofit implementation of ballasted flocculation at Metro is described and the effectiveness of load reductions in altering the trophic state of the immediate receiving water, Onondaga Lake, is examined. The role of ballasted flocculation in an integrated phosphorus management program for the Lake Ontario nearshore is considered.

The Chapter 4.17 has described the geological evolution of the Great Lakes and their hydrology and introduced selected features of lake physics, chemistry, and biology. In this chapter, two of the most important pollutant classes in the Great Lakes, nutrients and persistent bioaccumulative toxins, and biogeochemically mediated interactions between water, atmosphere, and lake sediments are examined. Next, the role of satellite remote sensing in enhancing our understanding these features of lake behavior is reviewed. Finally, policy and the regulatory environment, the bases for management of sustainable futures is looked at. As with the previous chapter, two key points are emphasized: (1) we should look to nature before the fact for help in differentiating sustainable and unsustainable practices and (2) it is critical that we increase our awareness of those things that ‘we don't know we don't know’ about the response of the Great Lakes to human perturbation. Adoption of an outlook that embraces an ethic, sensitivity, and understanding represents an excellent start to ensuring a sustainable future for these Great Lakes.

The nearshore phosphorus shunt hypothesis and the potential for mussels to excrete phosphorus sufficient to meet the growth requirements of Cladophora are now well accepted by scientists studying Great Lakes biogeochemistry. The response of algal growth to near bottom water column phosphorus concentrations and the interplay between excretion and mass transport in yielding those concentrations have, however, not been elucidated. Here we present soluble reactive phosphorus profiles from the near bottom environment of Lake Michigan at a site near Good Harbor Bay, Michigan, where both mussels and Cladophora were present. Soluble reactive phosphorus was observed to accumulate under quiescent conditions, establishing a concentration boundary layer (CBL), 5–15 cm thick, with near bottom concentrations on the order of 2–8 μg P/L. A one-dimensional model was applied to determine mass transport conditions mediating the transition from CBL formation to CBL destruction. Significant wave height (SWH) was used as an indicator of mass transport intensity, and it was determined that the formation/destruction transition occurred at a SWH of 0.2 m at the 8-m study site depth. The Great Lakes Cladophora Model was applied to determine the time intervals required to saturate (1 day with the CBL present) and deplete (14 days with the CBL absent) algal internal P stores. A review of SWH conditions at the study site indicated that a CBL would be expected to form at a frequency sufficient to support the phosphorus nutrition of Cladophora over the entire May to August interval.

The freshwater amphipod Diporeia is a dominant macroinvertebrate species in Lake Superior’s benthic community and an important prey item for many fish. A capacity to predict growth and production rates of Diporeia using a bioenergetics model requires information on physiological processes of the species. The objective of this study is to quantify oxygen consumption of Lake Superior Diporeia and to determine if respiration rate changes with body length. Diporeia were collected from Lake Superior and kept over natural sediment maintained at 4°C. Dissolved oxygen levels for groups of immature (2mm), juvenile (4mm), and adult (6mm) Diporeia in 20ml microcosms were measured using a polarographic microelectrode. Mass-specific respiration rates for Lake Superior Diporeia ranged from 32.0 to 44.7 mg O2 g DW−1 day−1. A significant relationship between body length and mass-specific respiration rate (p>0.1) was not found. The estimate of Diporeia respiration presented here is significantly higher (p<0.05) than previous findings from populations in Lakes Michigan and Ontario. This study provides new data on respiration rates of Lake Superior Diporeia and compares findings to studies for other connecting Great Lakes.