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 


April 22 – Silky Sharks Are Highly Impacted By Purse Seining at FADs

Bycatch of non-target species is a chronic problem in pelagic purse seine fisheries.  In the Western and Central Pacific tuna fishery, 95% of the elasmobranch by-catch is composed of juvenile silky sharks (Carcharinus falciformis), which are attracted to fish aggregating devices (FADs) deployed by fisherman to aggregate skipjack and yellowfin tuna.  Currently, sharks captured during purse seining operations are released alive, but little is known regarding their survival rate once released.  We discussed a paper by Hutchinson et al. (2015) that sought to determine the post-release survival of silky sharks captured in the Pacific purse seine fishery and identified the point during fishing operations when silky sharks endure injuries that ultimately lead to mortality.  The study revealed that 84% of sharks released after being captured in the purse seine ultimately die after being released and early removal of sharks from the net is the key to increasing their chances of survival. –Travis

Image via Joi Ito


April 15 – Forams Provide High-Resolution Climate Record from Santa Barbara Basin

Sediment cores collected from the Santa Barbara basin have recorded changes in ocean circulation and climate change from the past 20,000 years. Previous paleo-climate research has been focused in the North Atlantic basin, however this research provides evidence that ocean basins in the Pacific are just as useful in reconstructing climate change over the Holocene. Radiocarbon dating, sediment analysis, and benthic foraminifera provide evidence for four major global cooling and warming events, which also correspond with changes in ocean circulation. The first event was the last Ice age, followed by the Bolling-Allerod warming period (~14.5 kya), the Little Ice Age (~11 kya), and finally the modern warming event. In conclusion, the Santa Barbara basin in the Pacific ocean provides excellent evidence of changes in global climate over the past 20,000 years. – Jacque

Image via By Dr. Josef Reischig, CSc.


April 8 -Coccolith Abundance on the Rise with Increasing Ocean pCO2

The goal of this paper was to investigate the increase of coccolithophore abundance in the North Atlantic since the 1960s, with one of the major theories being the rising concentrations of carbon dioxide in the North Atlantic as the driving factor. Basic information was provided about coccolithophores, such as being calcifying primary producers that live in ocean surface waters . The accepted paradigm up until this point was that increases in atmospheric CO2 would drive an increase in pCO2 in the ocean, thereby contributing to ocean acidification that would be detrimental to organisms with calcareous exoskeletons. Random forest models were implemented to determine which variables may have the greatest effect on coccolith occurrence over the multiple decades that were sampled. The results of these models concluded that increasing CO2 concentrations are the main predictor of occurrence on both a local and global scale. –Shawna

Image via NEON ja/Richard Bartz talk/Papa Lima Whiskey