Bakterien: StŠbchenbakterien. Geobacter metallireducens
Das Bild zeigt Uran-abbauende Bakterien auf einem Schwermetall- Erz. Mikroorganismen der Gattung Geobacter kšnnen gelšstes Uran in Pechblende (Uraninit) umwandeln. Uraninit ist nicht wasserlšslich, verbleibt an Ort und Stelle und kann deshalb einfach entsorgt werden. Geobacter-Bakterien finden sich Ÿberall in Sedimenten, allerdings nur in geringer Zahl. Durch Zugabe von Acetat kšnnen sie zur Vermehrung angeregt werden. Das Verfahren soll schon bald in der Praxis angewandt werden.  Damit haben Mikrobiologen eine Mšglichkeit gefunden, uranverseuchtes Grundwasser durch Bakterien zu sŠubern.
Raster-Elektronen-Mikroskop,   3600:1

Oct. 14 – Can microbes at the sediment-water interface be used as a reliable source of energy?

Using fuel cell technology, Tender et al. provides insight into the application of harvesting electrical energy from the seafloor (2002). A voltage gradient naturally occurs between reductant-rich sediment on the seafloor and oxygen-rich seawater. Reductants such as sulfide are built up as a result of microorganisms oxidizing detrital organic carbon found within the sediment. Tender et al. sought to utilize this unique voltage gradient by placing fuel cells on the seafloor outside of Tuckerton, New Jersey and Newport, Oregon. Results suggest that the energy generated from these fuel cells remains relatively stable over time (one deployed fuel cell averaged a power density of 28 mW/m2 at 0.27 V for five months). Upon examination of microbial communities surrounding the anode, delta-Proteobacteria made up 76% of the 16S rDNA sequenced. Tender et al. suggests this power source can be used to provide energy to oceanographic equipment.

Image via US Department of Energy

  • Article – Harnessing microbially generated power on the sea floor
  • Citation – Tender, L.M., Reimers, C.E., Stecher III, H.A., Holmes, D.E., Bond, D.R., Lowy, D.A., Pilobello, K., Fertig, S.J., & Lovley, D.R. (2002). Harnessing microbially generated power on the seafloor. Nature Biotechnology, 20, 821-825.
  • Presenter – Lauren

Oct. 7 – Is it possible to reduce hurricanes strength while generating electricity?

As coastal populations and infrastructure continue to grow, hurricane damage is increasing in coastal regions. Jacobsen et al. (2014) propose that the installation of large arrays offshore wind turbines upwind of coastal regions will mitigate the impacts of hurricanes by reducing storm surge and wind speed of the storms before it makes landfall. Additionally, these offshore wind turbine arrays would generate large quantities of sustainable energy to address heightened energy demands of global population growth. To test this hypothesis, Jacobsen et al. (2014) modeled the impacts (wind, storm surge, and movement) of hurricanes Katrina and Sandy as both as they occurred (without offshore arrays), and again with offshore. Model output revealed that large turbine arrays could diminish peak near-surface wind speeds by 25-41 m s-1 and storm surge by 6-79%. Installation of these arrays presents high costs upfront. However, cost-benefit analysis reveals that these arrays would generate enough energy and reduce hurricane related damage enough in the long-term to actually be cheaper than the net cost of seawall installation and fossil fuel consumption in coastal regions. – Tyler

Image via US NOAA

  • Article – Taming hurricanes with arrays of offshore wind turbines
  • Citation – Jacobson, M. Z., Archer, C. L., & Kempton, W. (2014). Taming hurricanes with arrays of offshore wind turbines. Nature climate change, 4(3), 195-200.
  • Presenter – Tyler

Sept. 30 – Management trade offs, the needs marine mammals vs commercial fisheries

This week in Journal Club, we discussed a paper investigating the interaction between marine mammals and commercial fishing on fishery stocks in the Eastern North Atlantic.  As marine mammal populations continue to recover, and the human population continues to grow, both groups will rely more and more heavily on the marine environment to meet their nutritional needs.  Currently, marine mammal populations and fishery stocks are managed separately.  Smith et al. use a multi-species production model to demonstrate the interactions between a changing marine mammal population and different degrees of fishing effort. The model shows the codependence of the six test groups and the effectiveness of this approach at dealing with ecosystem level management questions, but leaves plenty of room for improvement as new life history and diet composition data become available for these different species. – Nick

Image via NOAA

  • Article – Stimulations to evaluate management trade-offs among marine mammal consumption needs commercial fishing fleets and finfish biomass.
  • Citation – Smith, L., Gamble, R., Gaichas, S., & Link, J. (2015). Simulations to evaluate management trade-offs among marine mammal consumption needs, commercial fishing fleets and finfish biomass. Marine Ecology Progress Series, 523, 215-232.
  • Presenter – Nick

Sept. 23 – Record of European settlement through sediment flux on corals

McCulloch et al. (2003) reveal that Ba/Ca ratios preserved in Porites corals sampled from the inner Great Barrier Reef (GBR) can act as proxy for sediment fluxes into the catchment. These increased sedimentary fluxes (sourced from the Burdekin river) can be detrimental to coral reef cover. Fluxes into this inner GBR have been preserved through time, except that after European Settlement (ca. 1870), a five-to tenfold increase in the amount of sedimentary delivery has been recorded (often more than 107 tonnes of sediment per single discharge event). Particularly, the largest discharge events have been recorded after intense drought, due to increased erosion during those times. The GBR remains an excellent study site to determine how anthropogenic impacts affect large, biodiverse areas, such as coral reefs. McCulloch et al. (2003) provide an insight on how land use practices impact both regional geomorphology and communities offshore.- Annie

Image via Narissa Spies

  • Article – Coral record of increased sediment flux to the inner Great Barrier Reef sinceEuropean settlement
  • Citation – McCulloch, M., Fallon, S., Wyndham, T., Hendy, E., Lough, J., & Barnes, D. (2003). Coral record of increased sediment flux to the inner Great Barrier Reef since European settlement. Nature421(6924), 727-730.
  • Presenter – Annie

Sept. 16 – Using a multicriteria, hierarchical diagnosis on the impacts of sediment deficit in the Ain River

While previous studies have demonstrated the negative impacts of hydroelectric dams on the surrounding environment, this one explicitly examines the effects of sediment deficit on different biotic and abiotic factors using a multi-criteria approach. Taking place along the lower river valley of the Ain River in France, the authors separated this region into four separate reaches (R1-R4) where R1 was bounded by a large dam (Allement Dam) upstream. Aerial images and on-site samples were taken to assess spatiotemporal changes along this span of river for gravel bar area, grain size pattern of sediment, bed degradation, channel mobility, number and quality of floodplain lakes, habitat diversity/richness, and fish diversity/richness. While many of these variables were hard to clearly distinguish as resulting from sediment deficit, gravel bar area did appear to show a strong correlation. There was a tendency for ecological integrity to increase further downstream away from the dam, however. Our discussion of this paper focused on the important use of a multi-criteria approach and how other factors may be contributing to changes along this span of the Ain River. A large factor that appeared to be missing from inclusion was the measure of water discharge from the dam, which would affect sediment load and transport from upstream to downstream reaches. This would be important in the assessment of restoring the river, particularly the degraded upstream reaches. – Josh

Image via PRA

  • Article: Assessment of consequences of sediment deficit on a gravel river bed downstream of dams in restoration perspectives: Application of a multicriteria, hierarchical and spatially explicit diagnosis.
  • Citation: Rollet, A. J., Piégay, H., Dufour, S., Bornette, G., & Persat, H. (2014). Assessment of consequences of sediment deficit on a gravel river bed downstream of dams in restoration perspectives: application of a multicriteria, hierarchical and spatially explicit diagnosis. River Research and Applications,30(8), 939-953.
  • Presenter: Josh

Sept. 9 – Soy bean fish feed and the use of digestive enzymes to enhance fish growth and reduce waste

People have long turned to the sea as an excellent source of high protein food, in many cases fish populations have been pushed to their limits or collapsed. Fish farms use a high protein fishmeal feed made of anchoveta but with price increases have switched to using trash fish. However, this is an unreliable form of feed in terms of quality and price increases as well. This article investigates the possibility of turning away from fish based protein, to soybean based protein feed pellets. Also, with the addition of the digestive enzyme papain, they look at the aid of digestive enzymes in increasing fish growth as well as feed conversion ratio. By studying diets of various amounts of fishmeal replaced with soy bean protein and varying amounts of papain, the authors found the soy bean protein overall did not show significant increases in fish growth. Papain was linked to increased feed conversion ratio as well as better growth. The soybean diets also resulted in reduced nitrogenous wastes produced by the fish into the surrounding water column. – Shawna 

Image via Erik Christensen 

Wind Turbines

Sept. 2- Population-energy-climate nexus

By the year 2100, the per capita energy demand of areas such as North America and Western Europe, combined with the growth of China and India will create an energy demand too high to be met solely by non-renewable resources. As non-renewable energy is finite, peak reserves are also discussed and their role in future energy production. Additionally, with higher energy consumption and use of fossil fuels, there is expected to be a continued rise in climate change to the extent of irreparable damage. The IPCC has stated that above a 2°C rise in temperature, there will be a tipping point form which we will struggle to come back from. The authors outline two scenarios regarding how we as a society meeting growing energy needs, one that is not constrained by environmental concerns, continuing to burn fossil fuels and surpass the 2°C change in temperature. The second scenario, climate constrained, acts with climate change in mind, encouraging renewable energy sources as the dominant source of energy production. – Shawna


Image by: Kwerdenker