Fox River Research Articles

Contaminants of emerging concern in tributaries to the Laurentian Great Lakes: II. Biological consequences of exposure.

The Laurentian Great Lakes contain one fifth of the world’s surface freshwater and have been impacted by human activity since the Industrial Revolution. In addition to legacy contaminants, nitrification and invasive species, this aquatic ecosystem is also the recipient of Contaminants of Emerging Concern (CECs) with poorly understood biological consequences. In the current study, we documented the presence, concentrations, and biological effects of CECs across 27 field sites in six Great Lakes tributaries by examining over 2250 resident and caged sunfish (Lepomis ssp.) for a variety of morphological and physiological endpoints and related these results to CEC occurrence. CEC were ubiquitous across studies sites and their presence and concentrations in water and sediment were highest in effluent dominated rivers and downstream of municipal wastewater treatment plant discharges. However, even putative upstream reference sites were not free of CEC presence and fish at these sites exhibited biological effects consistent with CEC exposure. Only the Fox River exhibited consistent adverse biological effects, including increased relative liver size, greater prominence of hepatocyte vacuoles and increased plasma glucose concentrations. Canonical Redundancy Analysis revealed consistent patterns of biological consequences of CEC exposure across all six tributaries. Increasing plasma glucose concentrations, likely as a result of pollutant-induced metabolic stress, were associated with increased relative liver size and greater prominence of hepatocyte vacuoles. These indicators of pollutant exposure were inversely correlated with indicators of reproductive potential including smaller gonad size and less mature gametes. The current study highlights the need for greater integration of chemical and biological studies and suggests that CECs in the Laurentian Great Lakes Basin may adversely affect the reproductive potential of exposed fish populations.

Current-Use Flame Retardants in the Water of Lake Michigan Tributaries.

In this study, we measured the concentrations of 65 flame retardants in water samples from five Lake Michigan tributaries. These flame retardants included organophosphate esters (OPEs), brominated flame retardants (BFRs), and Dechlorane-related compounds. A total of 59 samples, including both the particulate and the dissolved phases, were collected from the Grand, Kalamazoo, Saint Joseph, and Lower Fox rivers and from the Indiana Harbor and Ship Canal (IHSC) in 2015. OPEs were the most abundant among the targeted compounds with geometric mean concentrations ranging from 20 to 54 ng/L; OPE concentrations were comparable among the five tributaries. BFR concentrations were about 1 ng/L, and the most-abundant compounds were bis(2-ethylhexyl) tetrabromophthalate, 2-ethylhexyl 2,3,4,5-tetrabromobenzoate, and decabromodiphenyl ether. The highest BFR concentrations were measured in either the IHSC or the Saint Joseph River. The dechlorane-related compounds were detected at low concentrations (<1 pg/L). The fraction of target compounds in the particulate phase relative to the dissolved phase varied by chemical and tended to increase with their octanol-water partition coefficient. The chemical loading from all the five tributaries into Lake Michigan were <10 kg/year for the BFRs and about 500 kg/year for the OPEs.

A comparative evaluation of anaerobic dechlorination of PCB-118 and Aroclor 1254 in sediment microcosms from three PCB-impacted environments

Aroclor 1254 (A1254) is the most toxic commercial PCB mixture produced, primarily due to its relatively high concentrations of dioxin-like congeners. This study demonstrates a comparative evaluation of dechlorination of A1254 and PCB-118 by indigenous organohalide respiring bacteria enriched from three PCB impacted sites: Grasse River (GR), NY; Fox River (FR), WI; and Baltimore Harbor (BH), MD. PCB-118 dechlorination rates in GR, BH, and FR was 0.0308, 0.015, and 0.0006 Cl−/biphenyl/day, respectively. A1254 dechlorination rates in GR, FR, and BH were 0.0153, 0.0144, and 0.0048 Cl−/biphenyl/day, respectively. A1254 dechlorination was achieved through the removal of doubly-/singly-flanked chlorines in meta and para positions of mostly penta- followed by hexa- and hepta-chlorinated congeners by 88%, 69%, and 51% in GR, and 88%, 87%, and 83% in FR, respectively, while in BH mostly hepta- (70%) followed by hexa-chlorinated congeners (66%) were dechlorinated. A previously developed Anaerobic Dechlorination Model (ADM) quantified a total of 17 toxicity-related dechlorination pathways in all three sediment microcosms. The toxic equivalency of A1254 based on seven dioxin-like congeners decreased by about 53%, 45% and 21%, in GR, FR and BH microcosms, respectively. The dechlorination products were generally tetra- and tri-chlorinated congeners with unflanked chlorines, all of which is susceptible to further degradation by aerobic bacteria. Concerning the toxic congeners, ADM can be useful to initiate further research focusing on the stimulation of the toxicity reducing pathways for risk assessment and effective remediation strategies.

DIRECT DATING OF ULTRAMAFIC SILLS AND MAFIC INTRUSIONS ASSOCIATED WITH Ni-SULFIDE MINERALIZATION IN THE THOMPSON NICKEL BELT, MANITOBA, CANADA

The Paleoproterozoic Thompson nickel belt, a segment of the northwest margin of the Archean Superior craton in Manitoba, is one of the largest nickel-producing regions in the world and the second largest Ni-Cu-PGE (platinum group elements) mining camp in Canada after Sudbury. The nickel sulfide ores are hosted in or associated with ultramafic sills of komatiitic affinity that were emplaced into sulfur-rich metasedimentary rocks of the Ospwagan Group and subsequently strongly deformed and metamorphosed (amphibolite to granulite facies) during the Trans-Hudson orogeny. A U-Pb zircon age of 1880.2 ± 1.4 Ma for a metaperidotite (olivine orthopyroxenite) from the upper part of a boudinaged ultramafic sill at the Pipe 2 deposit is interpreted as the age of crystallization of the intrusion, the first age from an ultramafic sill containing mined nickel sulfide in the Thompson nickel belt. This age confirms a direct petrogenetic relationship between Ni-Cu-PGE mineralization and widespread mafic-ultramafic magmatic activity (Molson igneous events) at ca. 1.88 Ga along the Superior province craton margin (e.g., Thompson nickel belt, Fox River belt, Cape Smith belt, New Quebec orogen). At the south pit of the Thompson mine, a U-Pb zircon age of 1860.7 ± 0.7 Ma for a composite mafic intrusion (garnet amphibolite to layered metagabbro) identifies a new age of mafic magmatic activity in the Thompson nickel belt that is unrelated to nickel sulfide mineralization. The thermal effects of the Trans-Hudson orogeny are recorded by a range of zircon dates and ca. 1760 Ma metamorphic titanite from the South pit intrusion and are consistent with interpretations that regional metamorphism occurred as a single progressive event. The results of this study open up the possibility of using the high-precision U-Pb geochronology of mineralized ultramafic rocks to precisely constrain the duration of mafic-ultramafic magmatism in the Thompson nickel belt and assess potential age differences between ultramafic sills across and along strike of this world-class nickel metallotect.

Project Spotlight: Bridge for highway widening progresses smoothly thanks to precast concrete girders

Replacing the Fox River Bridge in Elgin, Ill., was part of the rebuilding and widening of the Interstate 90 (I-90) Jane Addams Memorial Tollway. The six-lane bridge has been replaced with two 1315 ft (400.8 m) long side-by-side four-lane bridges that stand 40 ft (12 m) above the Fox River. By installing precast concrete girders that increased the structural depth of the bridge, it became possible to construct the entire substructure of the new bridges underneath the existing bridge. Janesville, Wis.–based County Materials was selected to manufacture the 144 prestressed concrete bulb-tee girders, which are 168 ft (51.2 m) long and 90 in. (2300 mm) high.

“Like a Second Home”: Conceptualizing Experiences within the Fox River Watershed through a Framework of Emplacement

We propose and implement a new emplacement framework through exploration of the socio-spatial landscape of the Fox River Watershed (FRW) in Northeastern Wisconsin from a particular cultural perspective. Based primarily upon interviews conducted with 16 Hmong people to better understand and learn from the experiences of an important but overlooked FRW stakeholder group, we present our findings through the components of this framework: displacement, misplacement, replacement, and emplacement. Our research reveals that the strength of Hmong culture has persisted through tremendous loss and displacement, to survive and evolve in a new setting. The resettlement of Hmong people in the FRW has afforded relatively widespread access to landscapes that facilitate recreation, social interaction, and food production, enhancing physical and mental health and augmenting household incomes. It has also led to empowerment of women and the emergence of a generation of group members with formal ecological knowledge to add to their existing ethnobiological understanding and cultural foundation of ecological conscience. For such reasons, conservation organizations, policy makers, and departments of natural resources should look to build linking social capital between those in power and marginalized groups such as the Hmong.

Spatiotemporal variations in the abundance and composition of bulk and chromophoric dissolved organic matter in seasonally hypoxia-influenced Green Bay, Lake Michigan, USA

Green Bay, Lake Michigan, USA, is the largest freshwater estuary in the Laurentian Great Lakes and receives disproportional terrestrial inputs as a result of a high watershed to bay surface area ratio. While seasonal hypoxia and the formation of “dead zones” in Green Bay have received increasing attention, there are no systematic studies on the dynamics of dissolved organic matter (DOM) and its linkage to the development of hypoxia. During summer 2014, bulk dissolved organic carbon (DOC) analysis, UV–vis spectroscopy, and fluorescence excitation-emission matrices (EEMs) coupled with PARAFAC analysis were used to quantify the abundance, composition and source of DOM and their spatiotemporal variations in Green Bay, Lake Michigan. Concentrations of DOC ranged from 202 to 571μM-C (average=361±73μM-C) in June and from 279 to 610μM-C (average=349±64μM-C) in August. In both months, absorption coefficient at 254nm (a254) was strongly correlated to bulk DOC and was most abundant in the Fox River, attesting a dominant terrestrial input. Non-chromophoric DOC comprised, on average, ~32% of bulk DOC in June with higher terrestrial DOM and ~47% in August with higher aquagenic DOM, indicating that autochthonous and more degraded DOM is of lower optical activity. PARAFAC modeling on EEM data resulted in four major fluorescent DOM components, including two terrestrial humic-like, one aquagenic humic-like, and one protein-like component. Variations in the abundance of DOM components further supported changes in DOM sources. Mixing behavior of DOM components also indicated that while bulk DOM behaved quasi-conservatively, significant compositional changes occurred during transport from the Fox River to the open bay.

Interpretation of resistivity and magnetic anomalies from the Fox River Sill, Trans Hudson Orogen, Canada

SUMMARY The Fox River Belt is a sequence of rocks at the margin of the Proterozoic Trans Hudson Orogen in Canada that have been intruded by the Fox River Sill, a stratiform ultramafic‐mafic sill. An earlier 2-D magnetotelluric (MT) study of the sill revealed a conductor that is spatially correlated with a sheared serpentinite unit in the Lower Central Layered Zone of the sill. Re-analysis of the data from 10 MT sites lying on a 1.4 km north‐south profile, approximately perpendicular to geological strike, across a 1 km wide portion of the sill produced a resistivity model containing a conductor with an average resistivity of <1 ohm.m. Using aeromagnetic data from a profile subparallel to the MT profile, a geologically constrained magnetic model of the sill was constructed. Empirical susceptibility-magnetic mineral content relationships were used to estimate the magnetite content of the different geological units from the magnetic model. The results indicated a susceptibility of 0.2 SI for the sheared serpentinite unit, suggesting a magnetite content of ~5% which compares with petrological estimates of up to 10%. The bulk resistivity of geological units in the resistivity model was interpreted in terms of metallic mineral content using published resistivity relationships and a range of connectivity models. Integration of these results with magnetic and geological analyses suggests the enhanced conductivity in the sheared serpentinite is a result of a higher degree of magnetite interconnectivity due to the shear fabric. The analysis also reveals that although portions of the adjacent Marginal Zone in the sill contain concentrations of magnetite similar to those in the sheared serpentinite, the significantly higher resistivity of the Marginal Zone can be explained by a lower degree of magnetite interconnectivity.

Dynamics of dissolved and particulate phosphorus influenced by seasonal hypoxia in Green Bay, Lake Michigan

Despite major investments in point source reductions, portions of the Great Lakes, like Green Bay, remain hypereutrophic and are subject to persistent seasonal hypoxia. Phosphorus (P) is generally a limiting nutrient in the Great Lakes ecosystem, but not all P species are equally bioavailable, and the dynamics of nutrients and their correlation to algal bloom remain poorly characterized, in part, due to a lack of adequate quantification of P chemical speciation. During summer 2014, water samples were collected from seasonally hypoxic Green Bay for measurements of dissolved and particulate inorganic and organic P to examine P cycling dynamics along a steep nutrient gradient ranging from Fox River inflow dominated eutrophic waters in the southern bay to mesotrophic northern waters near the bay's connection with open Lake Michigan. River-derived dissolved and particulate P was quickly removed from the water column in southern Green Bay through biological uptake and sedimentation. Concentrations of phosphate or dissolved inorganic P (DIP) dramatically decreased from 828±216nM in the Fox River, comprising 57±1% of the total dissolved P, to 24±9nM in northern Green Bay where dissolved organic P (DOP) became predominant (>80%). Generally low phosphate concentrations and extremely high dissolved organic C/P ratios (2090±1160 in August 2014) suggested high DOP turnover rates and active transformation between DOP and DIP through organic degradation during P-limited conditions in Green Bay. Elevated DIP levels were accompanied by low dissolved oxygen in deeper waters (10–15m) of central Green Bay where hypoxia-development occurred, suggesting the release of DIP through particle regeneration under hypoxic conditions enhanced by lateral transport and sediment resuspension. High partition coefficients (Kd) of both inorganic and organic P and their significant negative correlation with suspended particulate matter concentrations indicated the particle-reactive nature of P in freshwater environments and may imply that DOP could also be bioavailable under P-limitation.

Importance of Natural and Anthropogenic Environmental Factors to Fish Communities of the Fox River in Illinois.

The dominant environmental determinants of aquatic communities have been a persistent topic for many years. Interactions between natural and anthropogenic characteristics within the aquatic environment influence fish communities in complex ways that make the effect of a single characteristic difficult to ascertain. Researchers are faced with the question of how to deal with a large number of variables and complex interrelationships. This study utilized multiple approaches to identify key environmental variables to fish communities of the Fox River Basin in Illinois: Pearson and Spearman correlations, an algorithm based on information theory called mutual information, and a measure of variable importance built into the machine learning algorithm Random Forest. The results are based on a dataset developed for this study, which uses a fish index of biological integrity (IBI) and its ten component metrics as response variables and a range of environmental variables describing geomorphology, stream flow statistics, climate, and both reach-scale and watershed-scale land use as independent variables. Agricultural land use and the magnitude and duration of low flow events were ranked by the algorithms as key factors for the study area. Reach-scale characteristics were dominant for native sunfish, and stream flow metrics were rated highly for native suckers. Regression tree analyses of environmental variables on fish IBI identified breakpoints in percent agricultural land in the watershed (~64%), duration of low flow pulses (~12 days), and 90-day minimum flow (~0.13 cms). The findings should be useful for building predictive models and design of more effective monitoring systems and restoration plans.

English

A pilot learning was performed at the Fox River Fiber improved paper dispensation company in DePere, Wisconsin, to establish the amount to which inoculation of oxygen and ozone could decrease the high chemical oxygen command, COD, in the sewage and the efficiency of the ozone/oxygen stream in suppressing construction of hydrogen sulfide gas in downstream sewage appearance. Adaptive Ozone Solutions, LLC, complete the oxygen/ozone making and injection scheme. Samples were analyzed both before and after oxygen/ozone insertion. Hydrogen sulfide gas was incessantly monitored at sewer stations downstream of Fox River filament. Consequences showed that with an extremely short contact time, effluent COD was concentrated by over 20%. A straightforward kinetic model predicts that a contact time of fewer than 40 minutes possibly will decrease COD by as much as 65%. In calculation, downstream hydrogen sulfide gas manufacture in the sewage mains was also improved proscribed, such that expensive Bioxide applications could be concentrated. Hydrogen sulfide gas, fashioned as an effect of these conditions, is the most common odorous gas found in municipal wastewater compilation and management systems.

Green Bay: Spatial variation in water quality, and landscape correlations

We conducted a high-resolution survey along the nearshore (369 km) in Green Bay using towed electronic instrumentation at approximately 15-m depth contour, with additional transects of the bay that were oriented cross-contour (49 km). Electronic sensor data provided an efficient characterization of a spatial pattern in water quality parameters. Nearshore water quality was correlated with adjacent landscape characterization. The regressions were able to explain over 80% of the alongshore variability for some parameters. The parameters with the strongest correlation were specific conductivity, beam attenuation, and chlorophyll. A clear feature of Green Bay is the loading introduced by the Fox River at the head of the bay. River loading sets up the conditions for a longitudinal gradient along the bay. Nutrient and chlorophyll gradients have persisted since first observed in monitoring surveys decades ago in spite of rapid flushing of the bay and efforts for remedial actions to restore areas of concern (AOCs). The water quality gradients were steepest in the 25-km closest to the mouth of the Fox River decreasing inversely with distance to where the bay opens to Lake Michigan. Summarized data from our 2010 tow and a concurrent National Coastal Condition Assessment (NCCA) survey compared to historical data (1971–1989) show a bay-wide rise in specific conductivity and chlorides, but only suggest highly variable total phosphorous and chlorophyll a in the inner bay. The tools employed (towed sensors, landuse characterization, and NCCA) can provide an efficient approach to a more regular and comprehensive bay-wide assessment.

Stimulated rejuvenation of dormant Aulacoseira granulata (Bacillariophyta) by Gloeocystis planctonica (Chlorophyta) in a eutrophic river.

The abundance of Aulacoseira granulata (Ehrenburg) Simonsen and Gloeocystis planctonica (West & G.S.West) Lemmermann was assessed during the summers of 2005 and 2010 in the eutrophic Fox River, Wisconsin, USA. In both years, a mid-summer bloom of G.planctonica was followed by the rapid growth of A.granulata. Laboratory experiments in which A.granulata was grown in cell-free filtrate of a G.planctonica culture revealed that the growth of A.granulata was stimulated in the G.planctonica-treated medium relative to controls. This effect was detected when dormant A.granulata cells were used as the source culture for the experiment but not when actively growing cells were used. Dormant A.granulata also grew more rapidly in river water collected after the 2010 G.planctonica bloom relative to river water collected before the bloom. These results suggest that the summer bloom of A.granulata in the river was stimulated by G.planctonica. This relationship can be described as stimulated rejuvenation, an interaction where the transition of an algal resting stage into active growth is triggered by exposure to another species.

PCBs refocused: Correlation of PCB concentrations in Green Bay legacy sediments with adjacent lithophilic, invasive biota

Green Bay sediments exhibit a gradient of polychlorinated biphenyl (PCB) concentrations from the mouth of the Fox River to the northern end of the bay. This study explored whether the sediment concentration gradient was reflected along Green Bay's rocky (non-depositional) eastern coast in a suspension feeder, the invasive quagga mussel (Dreissena bugensis), as well as in the main predator on quagga mussels, the invasive round goby (Neogobius melanostomus). We performed congener-specific PCB analyses on quagga mussels and round gobies collected from ten sites along the east shore of Green Bay. PCB results were compared with sediment data. Regression analyses showed that mussel tissue PCB concentrations followed sediment PCB concentrations (F1,6=16.4, P=0.007) except at two sites near Sturgeon Bay where cleaner Lake Michigan water enters in tidal pulses. Round goby PCB concentrations also followed the sediment trends (F1,7=8.17, P=0.024). However, only a weak relationship between PCB concentrations in quagga mussel and round goby was found (P=0.085), even though the species are trophically linked. Here, ontogenetic and seasonal details of round goby diet strongly influenced PCB concentrations such that in areas adjacent to high sediment PCB concentrations, fish length dictated round goby's PCB concentration (F1,14=7.46, P=0.016). Overall, our findings indicate that these exotic benthos refocus PCBs in near-shore regions in a pattern similar to that observed in sediments. Our results also highlight the need to understand trophic details in order to track contaminant bioaccumulation accurately.

Predicted effects of future climate warming on thermal habitat suitability for Lake Sturgeon (Acipenser fulvescens , Rafinesque, 1817) in rivers in Wisconsin, USA

Summary The Lake Sturgeon (Acipenser fulvescens, Rafinesque, 1817) may be threatened by future climate warming. The purpose of this study was to identify river reaches in Wisconsin, USA, where they might be vulnerable to warming water temperatures. In Wisconsin, A. fulvescens is known from 2291 km of large-river habitat that has been fragmented into 48 discrete river-lake networks isolated by impassable dams. Although the exact temperature tolerances are uncertain, water temperatures above 28–30°C are potentially less suitable for this coolwater species. Predictions from 13 downscaled global climate models were input to a lotic water temperature model to estimate amounts of potential thermally less-suitable habitat at present and for 2046–2065. Currently, 341 km (14.9%) of the known habitat are estimated to regularly exceed 28°C for an entire day, but only 6 km (0.3%) to exceed 30°C. In 2046–2065, 685–2164 km (29.9–94.5%) are projected to exceed 28°C and 33–1056 km (1.4–46.1%) to exceed 30°C. Most river-lake networks have cooler segments, large tributaries, or lakes that might provide temporary escape from potentially less suitable temperatures, but 12 short networks in the Lower Fox and Middle Wisconsin rivers totaling 93.6 km are projected to have no potential thermal refugia. One possible adaptation to climate change could be to provide fish passage or translocation so that riverine Lake Sturgeon might have access to more thermally suitable habitats.

Evaluating impairment in Wisconsin Areas of Concern using relative abundance of Smallmouth Bass

Smallmouth Bass (Micropterus dolomieu) is an important sportfish and has been suggested as a restoration target species in degraded aquatic environments such as “Areas of Concern” in the Great Lakes basin. Determining expected relative densities of fish and wildlife populations, such as Smallmouth Bass, in least-impacted situations is central to developing effective monitoring programs, assessing the level of relative impairment, determining appropriate restoration goals, and evaluating the efficacy of restoration efforts. We tested a straightforward classification scheme of Smallmouth Bass populations in least impacted non-wadeable rivers in Wisconsin based on parameters related to substrate and geographic location as both variables have been associated with relative Smallmouth Bass density. Coarse-substrate rivers tended to have higher Smallmouth Bass catch per effort values than fine-substrate rivers and southern rivers tended to have higher catch per effort values than northern rivers in Wisconsin. We used the expected Smallmouth Bass relative density estimates to assess the level of impairment of Smallmouth Bass populations in three Areas of Concern in Wisconsin (Milwaukee River and Estuary, Sheboygan River and Estuary, and the Fox River and Green Bay). We found that Smallmouth Bass catch per effort values were significantly higher in Areas of Concern than both the minimum and 25th percentile values for least-impacted rivers and were not significantly different from the median least-impacted values. Based on abundance, it does not appear that Smallmouth Bass populations are particularly impaired in these three Areas of Concern.

Perspectives from the Field: Cost Ramifications of Toxic Substance Control Act In Situ Characterization Policy on Contaminated Sediment Cleanup Projects

A good portion of the effort and funding going into Great Lakes restoration targets the removal via dredging of contaminated sediments from the designated areas of concern (AOCs). In fact, contaminated sediments are the underlying cause of several Beneficial Use Impairments that keep the AOCs from being delisted and restoration success claimed. A common contaminant in the Great Lakes AOCs, as elsewhere throughout the United States (US), is a class of persistent and bioaccumulating compounds called polychlorinated biphenyls (PCBs). There have been 15 sediment projects conducted to date under the Great Lakes Legacy Act program (Tuchman, 2013 ), and 11 have involved PCB-contaminated sediment. Contaminated sediment is also being removed from the Great Lakes through other programs such as the Superfund; to date, the Lower Fox River Superfund Remedial Action is the largest sediment removal project in the nation, with approximately 2.5 million cubic yards (1.9 million cubic meters) removed through 2012 and the planned removal of another 1.5 million cubic yards (1.2 million cubic meters).

Designing a connected nature reserve using a network flow theory approach

Establishing nature conservation reserves is an effective and widely accepted practice to protect biodiversity. In order to promote the effectiveness and efficiency of the reserve, spatial attributes of the reserve should be considered. Connectedness (contiguity) is one of these important spatial attributes. Currently in the biological literature there are only a few formal/exact optimization approaches to endogenously designing a connected nature reserve. This article adds a new approach by adapting a spatial unit allocation model to the reserve design problem. Using concepts from network flow theory, the model defines a sink site from which no flow directs out and ensures contiguity by specifying the outflow and inflow relationship of the potential sites. Computational performance of the model is tested using hypothetical problems with various sizes including up to 400 potential sites. Results show that the time needed to solve the problem to optimality increases exponentially both as number of potential sites increases and as species distribution gets more sparse. An empirical application involving 80 potential sites and 15 bird species in part of Fox River watershed, Illinois USA is presented. Factors influencing an IP model’s computational performance and potential extensions of the model were discussed.

The next dam on the Vistula River below Włocławek

This paper presents reasons for a decision on construction of the dam on the Vistula River below Wloclawek. It includes a justification of the overriding public interest for this construction, the benefits that it will bring and a short description of the project. In addition the criteria for choosing the location are given and parameters of the Wloclawek and Siarzewo dams are compared. DOI: 10.12736/issn.2300-3022.2013307 The Vistula River (Wisla) below Wloclawek may be perceived as Europe’s last wonderful wild river or as a huge unused commodity which has been abandoned for some reason. The dispute between the supporters of each point of view is a dispute over values. Therefore, it is very difficult to reach a compromise. The supporters of the wild river idea are convinced that the natural state of river is actually a basic value and any human interference is unacceptable. This wildness should in their opinion be protected by all available means to be passed on to future generations in an intact condition. Those who see the Vistula River (Wisla) as an unused resource think that its economic potential should be used reasonably as soon as possible for the common good. Of course the way of developing a navigable river and benefitting from it does not mean the destruction of its natural values and this is possible at the current technical level. Until the partitions of Poland the Vistula River (Wisla) had constituted the economic axis of Poland and in the 17th century it was the most navigable European river. Annually more than 250 thousand tons of goods, mainly cereal, were transported along it. In the second half of the 17th century the significance of the Vistula River (Wisla) started to decrease. It gradually became a peripheral river. As we know the lower Vistula River (dolna Wisla) section from the mouth of the Drweca River (Drweca) to Gdansk fell under Prussian rule. At the end of the 19th century that section was regulated and the mouth section was completely reconstructed. The excavation of the new outlet (Przekop) eliminated the risk of floods which had been worrying Gdansk citizens for centuries, especially in spring, when ice starts to float. I cannot help feeling that today these investments would be impossible. The 19th century was an era of many important discoveries and inventions which completely changed the economic life. At the end of the 19th century the possibility of transforming energy of flowing water, usually dammed, into electric power appeared. The first hydroelectric power station in the world was established in 1882 in Appleton (USA) on the Fox River. It was developed to supply power to a paper factory. The first hydroelectric power station in Europe was established in the Godalming tannery in England (1881). It was constructed to supply power for street and home lighting. The first large hydroelectric power station was opened in Deptford, a London district, in 1889. In Poland in the interwar period 12 hydroelectric power stations with a total capacity of 18 MW operated. Before World War II the largest hydroelectric power station in Poland with the capacity of 4 MW was in Grodek on the Wda River (Wda). It was constructed to supply energy to the dynamically developing town of Gdynia. After World War II Poland gained more than a dozen hydroelectric plants in the western parts of the country, among others in Pilchowice and Dychow on the Bobr River (Bobr). In 1946 the total capacity of Polish power stations came to 160 MW. In the 1960s large hydroelectric power stations were constructed in Solina, Wloclawek and Koronowo. Lower Vistula River – current state The theoretical energy potential of Polish rivers is estimated at approx. 23 TWh/year. However, only 12–14 TWh/year may be used due to technical reasons. Use of 8–8.5 TWh/year is economically justified. This potential is unequally distributed. Approx. 80% is on the Vistula River (Wisla) and approx. 50% of the whole energy potential is on the lower Vistula River (dolna Wisla). In Poland only 11% of energy potential of watercourses is used which puts us in last place in Europe. Plans of energy use of the Vistula River (Wisla) date at the beginning of 20th century. However, only in 1945 did T. Tillinger present the first concept of using the Vistula River (Wisla) energy potential. It was a bold project developed by an eminent Polish hydroengineer. He included in it his thoughts from the period when he had been developing designs of artificial waterways, regulation of the Vistula River (Wisla), canalling of the Bug River (Bug) and J. Granatowicz | Acta Energetica 3/16 (2013) | 99–105

Chloride and total phosphorus budgets for Green Bay, Lake Michigan

Green Bay is an elongated freshwater embayment located in northwestern Lake Michigan. Due to its short residence time, the lower bay is heavily influenced by the Fox River's large nutrient load. The inner bay is classified as hypereutrophic and a well-defined trophic gradient is observed moving away from the Fox River towards Lake Michigan, where the bay is nearly oligotrophic. Recent chloride and total phosphorus loading estimates were used to update a chloride and total phosphorus mass-balance model for the bay for 1994–2008. The chloride model provided a means to estimate turbulent eddy diffusion within the bay and exhibited excellent agreement with observed data. The total phosphorus model agreement with observed data was generally good, with the exception of a large deviation in lower Green Bay during 1999–2004. The model was used to estimate the internal loadings necessary to account for the deviation in phosphorus concentrations. The source of the unexpected increase remains unclear, but we speculate significant internal loading due to wind-driven sediment resuspension and hypoxia-induced phosphorus diffusion was significant. These models allow needed reductions to be identified and sourced and also indicate the role internal loading may play in the Green Bay phosphorus budget.