Hormone loads exported by a tile‐drained agroecosystem receiving animal wastes

Little is known regarding hormone export from tile‐drained agricultural fields despite the widespread presence of tile drains in the Midwestern United States. By intensively measuring water flow rates and hormone concentrations in four subsurface tile drains and three receiving ditches at a working Midwest farm, hormone fluxes and loads from the tile‐drained fields were quantified. Before and during the 17‐month study period (January 2009 – May 2010), the associated farm fields received various animal waste applications (beef, dairy, poultry, sheep, and swine). Hormones monitored included the estrogens17β‐ and 17α‐estradiol, estrone, and estriol; the natural androgens testosterone, and androstenedione; and the synthetic androgens 17β‐ and 17α‐trenbolone, and trendione. Hormone loads measured in the ditches for three drainage areas during the entire 17‐month study period were in ranges of 16–58 mg/ha for total estrogens, 6.8–19 mg/ha for natural androgens, and 4.2–44 mg/ha for synthetic androgens. Because higher hormone concentrations generally occurred during discrete periods of increased flow, high flow rates often were associated with a disproportionately high hormone flux. For example, 80% of total estrogens and natural androgens exported into the ditches occurred during only 9–26% of the study period, coinciding with the most significant storm events. In addition, hormone fluxes were highest during storm events that occurred shortly after animal waste applications. Therefore, to effectively reduce hormone loads exported to downstream aquatic ecosystems in the absence of any application reduction, the short periods during which high‐flow events occur must be targeted. Copyright © 2012 John Wiley & Sons, Ltd.     

Reply to discussion of Jamaican cenozoic ichnology: review and prospectus: (v. 50, p. 364–382)

Mitchell and Ramsook comment on the lithostratigraphic assignment of Jamaican Cenozoic ichnofossils discussed in Donovan et al. They argue that the Paleogene Richmond Formation should be subdivided to produce a ‘Moore Town formation’ in eastern Jamaica, but the latter remains undefined as a lithostratigraphic unit and no new lithostratigraphic evidence is produced to support their supposition. Further, their use of a flawed table of trace fossil distributions does not support their thesis. The distribution of trace fossils in the White Limestone Group presented by Donovan et al. follows the lithostratigraphic scheme that was current at the time that the research was originally undertaken in the early 2000s. Yet, whatever lithostratigraphic scheme is utilised for the island, it is apparent that the more accurate data is provided by the biostratigraphy of the larger benthic foraminifers. Copyright © 2015 John Wiley & Sons, Ltd.     

Geothermal Energy for Northern Canada: Is it Economical?

We examined the potential of geothermal energy development in northern Canadian communities to support local energy demand, along with providing an initial assessment of the economic viability of geothermal energy resources for (a) low enthalpy heating systems and (b) electrical power generation from high temperature resources. We estimate yearly energy production and cost per kWh for geothermal systems using scenarios for thermal and electrical production sustained over 15 years from temperatures reached in the 2–6-km depth range. All the calculations are based on a borehole fluid productivity of 30 kg/s. We assume this to be feasible in sedimentary aquifers and through fractured granites. Under such an assumption and assumptions made on the efficiency of heat exchangers, our modeling shows that thermal energy output for 120°C from 3- to 5-km wells can be as low as 5–8 cents/kWh thermal. For a 6 km depth, the cost of thermal energy can be as low as 1–2 cents/kW thermal for thermal energy production of 100–200 MWh annually.     

Changing sea ice conditions and marine transportation activity in Canadian Arctic waters between 1990 and 2012

Declining sea ice area in the Canadian Arctic has gained significant attention with respect to the prospect of increased shipping activities. To investigate relationships between recent declines in sea ice area with Arctic maritime activity, trend and correlation analysis was performed on sea ice area data for total, first-year ice (FYI), and multi-year ice (MYI), and on a comprehensive shipping dataset of observed vessel transits through the Vessel Traffic Reporting Arctic Canada Traffic Zone (NORDREG zone) from 1990 to 2012. Links to surface air temperature (SAT) and the satellite derived melt season length were also investigated. Between 1990 and 2012, statistically significant increases in vessel traffic were observed within the NORDREG zone on monthly and annual time-scales coincident with declines in sea ice area (FYI, MYI, and total ice) during the shipping season and on a monthly basis. Similarly, the NORDREG zone is experiencing increased shoulder season shipping activity, alongside an increasing melt season length and warming surface air temperatures (SAT). Despite these trends, only weak correlations between the variables were identified, although a step increase in shipping activity is apparent following the former summer sea ice extent minimum in 2007. Other non-environmental factors have also likely contributed to the observed increase in Arctic shipping activity within the Canadian Arctic, such as tourism demand, community re-supply needs, and resource exploration trends.     

Relationships between chironomids and water depth in Bosten Lake,Xinjiang, northwest China

A significant relationship between the distribution and abundance of chironomids and water depth has long been recognized. Few studies on this topic, however, have been carried out in arid regions where the chironomid community is usually controlled by water salinity. Bosten Lake, northwest China, the largest inland freshwater lake (~1,260 km²) in the country, provides a unique opportunity to investigate this relationship in an arid region. A total of 42 surface sediment samples from water depths of 0.9–17.0 m, and 12 chironomid taxa, were used in the analysis. The first principal component analysis (PCA) axis explained 59.3 % of the variance in the chironomid assemblage and there was a significant correlation between PCA axis 1 scores and water depth (R² = 0.84, P < 0.001). The chironomid assemblages change significantly at 8.0 m water depth. This threshold corresponds to an abrupt change in the basin slope and the spatial distribution of aquatic vascular plants. Redundancy analysis showed that abundances of Chironomus plumosus-type, Microchironomus and Cryptochironomus are positively correlated with water depth, whereas abundances of Tanytarsus, Polypedilum nubifer-type, Cricotopus and Psectrocladius sordidellus-type are negatively correlated with water depth. These ecological relationships are supported by published data. Qualitative chironomid-inferred changes in lake level and diatom-inferred changes in salinity from sediment core BSTC001 were compared. Close agreement in trends for these two variables validates the use of chironomid assemblages to study palaeo-hydrological variability in this westerlies-dominated, arid region of central Asia.     

Climate influences on water and sediment properties of Genovesa Crater Lake,Galápagos

Genovesa Crater Lake is a remote, hypersaline lake in the northern Galápagos archipelago that contains a finely laminated sediment record. This sediment record has the potential to provide a high-resolution history of past climate variability in the eastern tropical Pacific. Here we present modern climate, lake, and sediment observations from 2009 to 2012 to explore how local climate variability influences Genovesa Crater Lake and its sediments. Surface lake temperature is strongly linked to air temperature and is highly seasonal. Temperature stratification is strongest during the warm season, whereas temperature becomes more uniform through the water column in the cool season. Deeper and earlier mixing occurred during the 2010 La Niña, which subsequently delayed 2011 cool season mixing and maximum warm season surface temperatures in 2011 and 2012. Lake salinity changes are influenced by precipitation, evaporation and persistent seawater influx. The largest declines in subsurface salinity follow months after the rainy season, when temperatures cool and fresher surface water from the previous warm/wet season mixes into the subsurface. Between 2009 and 2012, more calcium carbonate precipitated during a period of higher salinity. The period of highest calcium carbonate abundance measured in sediment records that span the late nineteenth to twentieth century coincides with the failure of two consecutive rainy seasons in 1988 and 1989 as well as the coldest monthly sea surface temperature measured at Puerto Ayora in 1989. More calcium carbonate-rich laminae from AD 1550 ± 70 to 1675 ± 90 may indicate a greater frequency of prolonged droughts or cooler temperatures, although enhanced productivity may also modulate carbonate precipitation. More Ca-rich laminae in Genovesa coincide with dry conditions inferred from other Galápagos sediment proxies, as well as prolonged dry and cool conditions inferred from reconstructions of the Southern Oscillation Index and NINO3 sea surface temperatures.