Contemporary limnology of the rapidly changing glacierized watershed of the world's largest High Arctic lake.

Glacial runoff is predicted to increase in many parts of the Arctic with climate change, yet little is known about the biogeochemical impacts of meltwaters on downstream freshwater ecosystems. Here we document the contemporary limnology of the rapidly changing glacierized watershed of the world's largest High Arctic lake (Lake Hazen), where warming since 2007 has increased delivery of glacial meltwaters to the lake by up to 10-times. Annually, glacial meltwaters accounted for 62-98% of dissolved nutrient inputs to the lake, depending on the chemical species and year. Lake Hazen was a strong sink for NO3--NO2-, NH4+ and DOC, but a source of DIC to its outflow the Ruggles River. Most nutrients entering Lake Hazen were, however, particle-bound and directly transported well below the photic zone via dense turbidity currents, thus reinforcing ultraoligotrophy in the lake rather than overcoming it. For the first time, we apply the land-to-ocean aquatic continuum framework in a large glacierized Arctic watershed, and provide a detailed and holistic description of the physical, chemical and biological limnology of the rapidly changing Lake Hazen watershed. Our findings highlight the sensitivity of freshwater ecosystems to the changing cryosphere, with implications for future water quality and productivity at high latitudes.

Sulfide production kinetics and model of stormwater retention ponds.

Stormwater retention ponds can play a critical role in mitigating the detrimental effects of urbanization on receiving waters that result from increases in polluted runoff. However, the benthic oxygen demand of stormwater facilities may cause significant hypoxia and trigger the production of hydrogen sulfide (H2S). This process is not well-documented and further research is needed to characterize benthic processes in stormwater retention ponds in order to improve their design and operation. In this study, sediment oxygen demand (SOD), sediment ammonia release (SAR) and sediment sulfide production (SSP) kinetics were characterized in situ and in the laboratory. In situ SOD and SSP data were utilized to develop a stormwater retention pond water sulfide concentration model which demonstrates strong correlation with sulfide concentrations observed in situ (r = 0.724, N = 91, p < 0.001) and in laboratory experiments (r = 0.691, N = 38, p < 0.001). At 4 °C, in situ rates of SOD, SAR and SSP were higher than those measured in laboratory. Sulfate-reducing bacteria (SRB) represented 4.99% of the bacteria present in the top 30 cm of the pond sediment, with Desulfobulbaceae spp., Desulfobacteraceae spp. and Desulfococcus spp. being the dominant SRB taxa identified.

Heliobacteria Reveal Fermentation As a Key Pathway for Mercury Reduction in Anoxic Environments.

The accumulation of mercury (Hg) in rice, a dietary staple for over half of the world's population, is rapidly becoming a global food safety issue. Rice paddies support the anaerobic production of toxic methylmercury that accumulates in plant tissue, however the microbial controls of Hg cycling in anoxic environments remain poorly understood. In this study, we reveal a novel reductive Hg metabolism in a representative of the family Heliobacteria ( Heliobacterium modesticaldum Ice1) that we confirm in model chemotrophic anaerobes. Heliobacteria served as our initial model because they are a family of spore-forming fermentative photoheterotrophs commonly isolated from terrestrial environments. We observed that H. modesticaldum reduced up to 75% of HgII under phototrophic or fermentative conditions. Fermentative HgII reduction relied on the ability of cells to oxidize pyruvate whereas phototrophic HgII reduction could be supported even in the absence of a carbon source. Inhibiting pyruvate fermentation eliminated HgII reduction in all chemotrophic strains tested, whereas phototrophic cells remained unaffected. Here we propose a non mer-operon dependent mechanism for Hg0 production in anoxic environments devoid of light where external electron acceptors are limited. These mechanistic details provide the foundation for novel bioremediation strategies to limit the negative impacts of Hg pollution.

Lead(ii) soaps: crystal structures, polymorphism, and solid and liquid mesophases.

The long-chain members of the lead(ii) alkanoate series or soaps, from octanoate to octadecanoate, have been thoroughly characterized by means of XRD, PDF analysis, DSC, FTIR, ssNMR and other techniques, in all their phases and mesophases. The crystal structures at room temperature of all of the members of the series are now solved, showing the existence of two polymorphic forms in the room temperature crystal phase, different to short and long-chain members. Only nonanoate and decanoate present both forms, and this polymorphism is proven to be monotropic. At higher temperature, these compounds present a solid mesophase, defined as rotator, a liquid crystal phase and a liquid phase, all of which have a similar local arrangement. Since some lead(ii) soaps appear as degradation compounds in oil paintings, the solved crystal structures of lead(ii) soaps can now be used as fingerprints for their detection using X-ray diffraction. Pair distribution function analysis on these compounds is very similar in the same phases and mesophases for the different members, showing the same short range order. This observation suggests that this technique could also be used in the detection of these compounds in disordered phases or in the initial stages of formation in paintings.

A little bit of light goes a long way: the role of phototrophs on mercury cycling.

Among toxic metals, mercury (Hg) is a global priority contaminant due to the biomagnification of the most toxic form methylmercury (MeHg) in food webs, even in remote regions, such as the high Arctic. The importance of Hg as a chemical of major concern to human health was underscored by the recent adoption of the Minamata Convention on Mercury, a legally binding treaty that requires government agencies be equipped to monitor processes affecting global mercury transport and cycling. For several decades now, field and laboratory experiments have shown that phototrophs can directly interact with Hg and affect its speciation and fate. While an important body of work on the role of chemotrophic microbes on Hg cycling has been undertaken, the role of phototrophs is too often overlooked. Strikingly, what is known about phototroph-Hg interactions pertains mostly to oxygenic phototrophs with relatively little being known about anoxygenic phototrophs. Ongoing environmental change will no doubt affect the physical and chemical properties of aquatic ecosystems, which in turn will alter all phototrophic community dynamics. How these changes will affect the Hg cycle represent an important knowledge gap. After synthesizing what is currently known about chemotrophic Hg transformations, we describe the current state of knowledge on what is known about how phototrophs (bacteria and algae) affect Hg cycling (i.e., alteration of Hg redox state, Hg scavenging, potential for methylation) as well as describe the cellular and molecular targets of Hg toxicity in phototrophs. We discuss these interactions in an evolutionary context and provide recommendations for future research directions.

Temperature and the sulfur cycle control monomethylmercury cycling in high Arctic coastal marine sediments from Allen Bay, Nunavut, Canada.

Monomethylmercury (MMHg) is a neurotoxin of concern in the Canadian Arctic due to its tendency to bioaccumulate and the importance of fish and wildlife in the Inuit diet. In lakes and wetlands, microbial sediment communities are integral to the cycling of MMHg; however, the role of Arctic marine sediments is poorly understood. With projected warming, the effect of temperature on the production and degradation of MMHg in Arctic environments also remains unclear. We examined MMHg dynamics across a temperature gradient (4, 12, 24 °C) in marine sediments collected in Allen Bay, Nunavut. Slurries were spiked with stable mercury isotopes and amended with specific microbial stimulants and inhibitors, and subsampled over 12 days. Maximal methylation and demethylation potentials were low, ranging from below detection to 1.13 pmol g(-1) h(-1) and 0.02 pmol g(-1) h(-1), respectively, suggesting that sediments are likely not an important source of MMHg to overlying water. Our results suggest that warming may result in an increase in Hg methylation - controlled by temperature-dependent sulfate reduction, without a compensatory increase in demethylation. This study highlights the need for further research into the role of high Arctic marine sediments and climate on the Arctic marine MMHg budget.

A new oral contraceptive based on the normophasic method.

62 women were treated for 554 cycles with normophasic oral contraceptive Fisioquens. A treatment cycle consists of 7 tablets of 0.05 mg ethinyloestradiol, followed by 15 tablets with a combination of 0.05 mg ethinyl-oestradiol and 1 mg lynestrenol. No pregnancies occurred. Both tolerance of the preparation and cycle control were good. Irregular bleeding occurred sporadically. Various side-effects diminished during treatment and even disappeared completely. Fisioquens appears to be a reliable contraceptive with a minimum of side-effects.

PIP: A trial involved 62 women for over 554 cycles during which time a new normophasic oral contraceptive, Fisioquens, was administered. The preparation was tested with particular reference to the following parameters: contraceptive reliability, cycle control, frequency of possible side effects, and drug tolerance. A treatment cycle consisted of 7 tablets of .05 mg ethinyl estradiol followed by 15 tablets of a combination .05 mg ethinyl estradiol and 1 mg lynestrenol. Pregnancies were absent and irregular bleeding occurred sporadically. Various side effects diminished during treatment. The number of dropouts which could probably be attributed to the preparation itself was 4 (6.4%). These data indicate that Fisioquens appears to be a reliable contraceptive with a minimum number of side effects.