Mechanisms contributing to the deep chlorophyll maximum in Lake Superior

The seasonal appearance of a deep chlorophyll maximum (DCM) in Lake Superior is a striking phenomenon that is widely observed; however its mechanisms of formation and maintenance are not well understood. As this phenomenon may be the reflection of an ecological driver, or a driver itself, a lack of understanding its driving forces limits the ability to accurately predict and manage changes in this ecosystem. Key mechanisms generally associated with DCM dynamics (i.e. ecological, physiological and physical phenomena) are examined individually and in concert to establish their role. First the prevailing paradigm, “the DCM is a great place to live”, is analyzed through an integration of the results of laboratory experiments and field measurements. The analysis indicates that growth at this depth is severely restricted and thus not able to explain the full magnitude of this phenomenon. Additional contributing mechanisms like photoadaptation, settling and grazing are reviewed with a one-dimensional mathematical model of chlorophyll and particulate organic carbon. Settling has the strongest impact on the formation and maintenance of the DCM, transporting biomass to the metalimnion and resulting in the accumulation of algae, i.e. a peak in the particulate organic carbon profile. Subsequently, shade adaptation becomes manifest as a chlorophyll maximum deeper in the water column where light conditions particularly favor the process. Shade adaptation mediates the magnitude, shape and vertical position of the chlorophyll peak. Growth at DCM depth shows only a marginal contribution, while grazing has an adverse effect on the extent of the DCM. The observed separation of the carbon biomass and chlorophyll maximum should caution scientists to equate the DCM with a large nutrient pool that is available to higher trophic levels. The ecological significance of the DCM should not be separated from the underlying carbon dynamics. When evaluated in its entirety, the DCM becomes the projected image of a structure that remains elusive to measure but represents the foundation of all higher trophic levels. These results also offer guidance in examine ecosystem perturbations such as climate change. For example, warming would be expected to prolong the period of thermal stratification, extending the late summer period of suboptimal (phosphorus-limited) growth and attendant transport of phytoplankton to the metalimnion. This reduction in epilimnetic algal production would decrease the supply of algae to the metalimnion, possibly reducing the supply of prey to the grazer community. This work demonstrates the value of modeling to challenge and advance our understanding of ecosystem dynamics, steps vital to reliable testing of management alternatives.

Glomerular filtration rate estimates decrease during high altitude expedition but increase with Lake Louise acute mountain sickness scores

AIM: Acute mountain sickness (AMS) can result in pulmonary and cerebral oedema with overperfusion of microvascular beds, elevated hydrostatic capillary pressure, capillary leakage and consequent oedema as pathogenetic mechanisms. Data on changes in glomerular filtration rate (GFR) at altitudes above 5000 m are very limited. METHODS: Thirty-four healthy mountaineers, who were randomized to two acclimatization protocols, undertook an expedition on Muztagh Ata Mountain (7549 m) in China. Tests were performed at five altitudes: Zurich pre-expedition (PE, 450 m), base camp (BC, 4497 m), Camp 1 (C1, 5533 m), Camp 2 (C2, 6265 m) and Camp 3 (C3, 6865 m). Cystatin C- and creatinine-based (Mayo Clinic quadratic equation) GFR estimates (eGFR) were assessed together with Lake Louise AMS score and other tests. RESULTS: eGFR significantly decreased from PE to BC (P < 0.01). However, when analysing at changes between BC and C3, only cystatin C-based estimates indicated a significant decrease in GFR (P = 0.02). There was a linear decrease in eGFR from PE to C3, with a decrease of approx. 3.1 mL min(-1) 1.73 m(-2) per 1000 m increase in altitude. No differences between eGFR of the two groups with different acclimatization protocols could be observed. There was a significant association between eGFR and haematocrit (P = 0.01), whereas no significant association between eGFR and aldosterone, renin and brain natriuretic peptide could be observed. Finally, higher AMS scores were significantly associated with higher eGFR (P = 0.01). CONCLUSIONS: Renal function declines when ascending from low to high altitude. Cystatin C-based eGFR decreases during ascent in high altitude expedition but increases with AMS scores. For individuals with eGFR <40 mL min(-1) 1.73 m(-2), caution may be necessary when planning trips to high altitude above 4500 m above sea level.

Paleomagnetic Study of the Portage Lake Volcanics exposed in the Quincy Mine

A detailed paleomagnetic and rock-magnetic investigation was conducted on thirty six basaltic flows of the ~1095 Ma Portage Lake Volcanics. The flows were sampled along the East Adit of the Quincy Mine (Hancock, MI). Thirty two flows yielded well-defined primary magnetization directions carried by magnetite. A secondary magnetization component carried by hematite was also found in twenty nine flows. After correction for serial correlation between the flows, nineteen independent mean directions were calculated. The corresponding paleomagnetic pole is located at 25.5 °N, 182.1 °W (A95 = 3.5°). The new pole overlaps with the pole from the ~1087 Ma Lake Shore Traps suggesting a standstill of the North American plate during that time period. The low angular dispersion of virtual geomagnetic poles (S = 7.9°) suggests that the flows were erupted within a short time period, or that the strength of geomagnetic secular variation was lower than that of the recent field.

Isolation of plant growth promoting bacteria from torch lake sediments and their role in phytoremediation of metal contaminated soil

In this study, we isolated eight copper-resistant bacteria from Torch Lake sediment contaminated by copper mine tailings (stamp sand). Sequence analysis of gyrB and rpoD genes revealed that these organisms are closer to various Pseudomonas species. These eight bacterial isolates were also resistant to zinc, cesium, lead, arsenate and mercury. Further characterization showed that all the strains produced plant growth promoting indole-3-acetic acid (IAA), iron chelating siderophore and solubilized mineral phosphate and metals. The effect of bacterial inoculation on plant growth and copper uptake by maize (Zea mays) and sunflower (Helianthus annuus) was investigated using one of the isolates (Pseudomonas sp. TLC 6-6.5-4) with higher IAA production and phosphate and metal soubilization, which resulted in a significant increase in copper accumulation in maize and sunflower, and an increase in the total biomass of maize. Genes involved in copper resistance of Pseudomonas sp. TLC 6-6.5-4 was analyzed by transposon mutational analysis. Two copper sensitive mutants with significant reduction in copper resistance were identified: CSM1, a mutant disrupted in trp A gene (tryptophan synthase alpha subunit); CSM2, a mutant disrupted in clpA gene (ATP-dependent Clp protease). Proteomic and metabolomic analysis were performed to identify biochemical and molecular mechanisms involved in copper resistance using CSM2 due to its lower minimum inhibitory concentration compared with CSM1 and the wild type. The effect of different bacterial inoculation methods on plant growth, copper uptake and soil enzyme activities was investigated. Four different delivery methods were used including soil inoculation (before or after plant emergence), seed coating and root dipping. Soil inoculation before sowing seeds and coating seeds with PGPB led to better growth of maize, higher copper uptake and an increase in soil invertase and dehydrogenase activities. Proteomic and metabolomic analyses were performed to investigate the effect of bacterial inoculation on maize grown in normal soil and stamp sand. Our results revealed that bacterial inoculation led to environment-dependent effects on maize proteome and metabolome.

DEVELOPMENT OF A CONCEPTUAL MODEL AND PARAMETERIZATION OF A MATHEMATICAL MODEL FOR SEDIMENT PHOSPHORUS DIAGENESIS, SORPTION AND RELEASE FROM ONONDAGA LAKE SYRACUSE, NEW YORK

Eutrophication is a persistent problem in many fresh water lakes. Delay in lake recovery following reductions in external loading of phosphorus, the limiting nutrient in fresh water ecosystems, is often observed. Models have been created to assist with lake remediation efforts, however, the application of management tools to sediment diagenesis is often neglected due to conceptual and mathematical complexity. SED2K (Chapra et al. 2012) is proposed as a "middle way", offering engineering rigor while being accessible to users. An objective of this research is to further support the development and application SED2K for sediment phosphorus diagenesis and release to the water column of Onondaga Lake. Application of SED2K has been made to eutrophic Lake Alice in Minnesota. The more homogenous sediment characteristics of Lake Alice, compared with the industrially polluted sediment layers of Onondaga Lake, allowed for an invariant rate coefficient to be applied to describe first order decay kinetics of phosphorus. When a similar approach was attempted on Onondaga Lake an invariant rate coefficient failed to simulate the sediment phosphorus profile. Therefore, labile P was accounted for by progressive preservation after burial and a rate coefficient which gradual decreased with depth was applied. In this study, profile sediment samples were chemically extracted into five operationally-defined fractions: CaCO3-P, Fe/Al-P, Biogenic-P, Ca Mineral-P and Residual-P. Chemical fractionation data, from this study, showed that preservation is not the only mechanism by which phosphorus may be maintained in a non-reactive state in the profile. Sorption has been shown to contribute substantially to P burial within the profile. A new kinetic approach involving partitioning of P into process based fractions is applied here. Results from this approach indicate that labile P (Ca Mineral and Organic P) is contributing to internal P loading to Onondaga Lake, through diagenesis and diffusion to the water column, while the sorbed P fraction (Fe/Al-P and CaCO3-P) is remaining consistent. Sediment profile concentrations of labile and total phosphorus at time of deposition were also modeled and compared with current labile and total phosphorus, to quantify the extent to which remaining phosphorus which will continue to contribute to internal P loading and influence the trophic status of Onondaga Lake. Results presented here also allowed for estimation of the depth of the active sediment layer and the attendant response time as well as the sediment burden of labile P and associated efflux.

A Balance Shifted: The Unionization of Michigan’s Lake Copper District, 1935-1955

Three decades after the unsuccessful 1913-1914 strike at the Lake District copper mines of Michigan, workers organized as Local 584 of the International Union of Mine, Mill, and Smelter Workers (Mine Mill) signed a union contract with Calumet & Hecla Consolidated Copper Company. C & H was the last and most significant of the region’s three major copper mining companies to unionize during the three-year period from 1939 to 1942. This paper tells the untold history of the successful union drives in the Lake District’s copper mines, starting with Copper Range Company in 1939 and encompassing the subsequent unionizations of Quincy Mining Company and finally C & H. The paper develops thematic connections between the 1913-1914, including Mine Mill’s lineage to the Western Federation of Miners, parallel ethnic dimensions, and, most significantly, the contrasting role of state authority between the two time periods. The paper carries the Lake District’s labor history forward to 1955 to include United Steelworkers’ successful challenge to Mine Mill in 1950 and the strike of 1955. This history also incorporates source material from the papers of highly influential union organizer and representative Eugene Saari, material which to date has not been integrated into the labor history of the region. This paper has not yet been submitted.

Divergence along a steep ecological gradient in lake whitefish (Coregonus sp.)

To understand mechanisms structuring diversity in young adaptive radiations, quantitative and unbiased information about genetic and phenotypic diversity is much needed. Here, we present the first in-depth investigation of whitefish diversity in a Swiss lake, with continuous spawning habitat sampling in both time and space. Our results show a clear cline like pattern in genetics and morphology of populations sampled along an ecological depth gradient in Lake Neuchâtel. Divergent natural selection appears to be involved in shaping this cline given that trait specific P(ST)-values are significantly higher than F(ST)-values when comparing populations caught at different depths. These differences also tend to increase with increasing differences in depth, indicating adaptive divergence along a depth gradient, which persists despite considerable gene flow between adjacent demes. It however remains unclear, whether the observed pattern is a result of currently stable selection-gene flow balance, incipient speciation, or reverse speciation due to anthropogenic habitat alteration causing two formerly divergent species to collapse into a single gene pool.

Archeological Investigations at the Big Creek Lake Site (24RA34)

In August 1977 excavation was conducted at the Big Creek Lake site -24RA34- at the outlet of the 91g Creek Lakes, Selway-Bitterroot Wilderness Area, Ravalli County, Montana. The site contained shallow, disturbed deposits and lacks any statisgraphic separation. One of these occupations was identified by a projectile point type not previously reported from the area. This was termed Big Creek Corner Notched and its temporal affiliation is not precisely known. Comparative material from Colorado and Alberta suggest either Early Archaic or Late Archaic affiliation. The occupations exemplified by Big Creek Corner Notched points and by Pelican Lake-Elko points (Late Archaic 1000 B.B – A.D. 200) were the most prevalent at the site. Less intensive occupations are by ·Middle Plains Archaic McKean points and Late Prehistoric small side notche arrow points. Microscopic analysis of tool working edges shows several of the projectile point forms were used as multi-functional implements. especially as butchering tools. Many of the types of chipped stone recovered from the site are from known sources in western Montana; indicating group movements within the eastern portion of the Intermountain region. Based on the numerous projectile points and cutting tools, the site is interpreted as a seasonally occupied base camp for hunters.

The Testing and Concentration of Lake Chelan Copper Ore

The geologic history of the Holden area and Lake Chelan district is an integral part of the history of the Cascade Mountain Range. The structure is very complex and the rocks, which have been subjected to intense metamorphic action, are portions of a roof pendant and consists of gneisses, schists and quartzites that are often difficult to correlate.

Ground Water in the Lake Basin Field and Adjacent Area

This thesis consists of studying the stratigraphic and structural features of the Lake Basin Field and an adjacent area with special emphasis upon the ground water conditions present.

Study of particle movement in the nearshore region of Lake Superior with radioisotope tracers

Biogeochemical processes in the coastal region, including the coastal area of the Great Lakes, are of great importance due to the complex physical, chemical and biological characteristics that differ from those on either the adjoining land or open water systems. Particle-reactive radioisotopes, both naturally occurring (210Pb, 210Po and 7Be) and man-made (137Cs), have proven to be useful tracers for these processes in many systems. However, a systematic isotope study on the northwest coast of the Keweenaw Peninsula in Lake Superior has not yet been performed. In this dissertation research, field sampling, laboratory measurements and numerical modeling were conducted to understand the biogeochemistry of the radioisotope tracers and some particulate-related coastal processes. In the first part of the dissertation, radioisotope activities of 210Po and 210Pb in a variability of samples (dissolved, suspended particle, sediment trap materials, surficial sediment) were measured. A completed picture of the distribution and disequilibrium of this pair of isotopes was drawn. The application of a simple box model utilizing these field observations reveals short isotope residence times in the water column and a significant contribution of sediment resuspension (for both particles and isotopes). The results imply a highly dynamic coastal region. In the second part of this dissertation, this conclusion is examined further. Based on intensive sediment coring, the spatial distribution of isotope inventories (mainly 210Pb, 137Cs and 7Be) in the nearshore region was determined. Isotope-based focusing factors categorized most of the sampling sites as non- or temporary depositional zones. A twodimensional steady-state box-in-series model was developed and applied to individual transects with the 210Pb inventories as model input. The modeling framework included both water column and upper sediments down to the depth of unsupported 210Pb penetration. The model was used to predict isotope residence times and cross-margin fluxes of sediments and isotopes at different locations along each transect. The time scale for sediment focusing from the nearshore to offshore regions of the transect was on the order of 10 years. The possibility of sediment longshore movement was indicated by high inventory ratios of 137Cs: 210Pb. Local deposition of fine particles, including fresh organic carbon, may explain the observed distribution of benthic organisms such as Diporeia. In the last part of this dissertation, isotope tracers, 210Pb and 210Po, were coupled into a hydrodynamic model for Lake Superior. The model was modified from an existing 2-D finite difference physical-biological model which has previously been successfully applied on Lake Superior. Using the field results from part one of this dissertation as initial conditions, the model was used to predict the isotope distribution in the water column; reasonable results were achieved. The modeling experiments demonstrated the potential for using a hydrodynamic model to study radioisotope biogeochemistry in the lake, although further refinements are necessary.