Tracking habitat and resource use for the jumbo squid Dosidicus gigas: a stable isotope analysis in the Northern Humboldt Current System

To determine the habitat and resource use of Dosidicus gigas in the Northern Humboldt Current System, we analysed carbon and nitrogen stable isotopes of 234 individuals collected during 2008–2010. Large variations in mantle stable isotope ratios were recorded, with values ranging from −19.1 to −15.1 ‰ (δ¹³C) and from 7.4 to 20.5 ‰ (δ¹⁵N). Most of the variation was explained by latitude, followed by distance to shelf break for carbon and by squid size for nitrogen. Latitudinal variations with increasing values from north to south were also found in zooplankton samples and were related to changes in isotope baseline values probably due to oxygen minimum zones that occur off Peru. This similar latitudinal trend in both zooplankton and D. gigas samples reveals that D. gigas is a relatively resident species at the scale of its isotopic turnover rate (i.e. a few weeks), even if this is not necessarily the case at the scale of its life. A small but significant size effect on δ¹³C values suggests that jumbo squid perform offshore–onshore ontogenic migration, with juveniles distributed offshore. For nitrogen, the high inter-individual variability observed with mantle length indicates that D. gigas can prey on a high variety of resources at any stage of their life cycle. This large-scale study off the coast of Peru provides further evidence that D. gigas have the capability to explore a wide range of habitats and resources at any stage of their life.     

Experimental warming shows that decomposition temperature sensitivity increases with soil organic matter recalcitrance

Soil C decomposition is sensitive to changes in temperature, and even small increases in temperature may prompt large releases of C from soils. But much of what we know about soil C responses to global change is based on short-term incubation data and model output that implicitly assumes soil C pools are composed of organic matter fractions with uniform temperature sensitivities. In contrast, kinetic theory based on chemical reactions suggests that older, more-resistant C fractions may be more temperature sensitive. Recent research on the subject is inconclusive, indicating that the temperature sensitivity of labile soil organic matter (OM) decomposition could either be greater than, less than, or equivalent to that of resistant soil OM. We incubated soils at constant temperature to deplete them of labile soil OM and then successively assessed the CO2-C efflux in response to warming. We found that the decomposition response to experimental warming early during soil incubation (when more labile C remained) was less than that later when labile C was depleted. These results suggest that the temperature sensitivity of resistant soil OM pools is greater than that for labile soil OM and that global change-driven soil C losses may be greater than previously estimated.     

Flooding impacts on responses of a riparian consumer to cross-ecosystem subsidies

Landscape-driven processes impact the magnitude and direction of cross-ecosystem resource subsidies, but they may also control consumers' numerical and functional responses by altering habitat availability. We investigated effects of the interaction between habitat availability and subsidy level on populations of a riparian fishing spider, Dolomedes aquaticus, using a flood disturbance gradient in the Waimakariri River catchment, New Zealand. D. aquaticus predominantly eat aquatic prey as they hunt from the water surface. However, D. aquaticus biomass peaked at rivers with intermediate flood disturbance, rather than at less flood-prone rivers where the biomass of aquatic insect prey was markedly higher. Flooding positively influenced spider habitat quality, and an experimental manipulation at stable rivers indicated that unembedded cobbles, preferred D. aquaticus habitat, were a limiting factor, preventing response to the increased prey resource at stable sites. Potential terrestrial prey abundance was low, did not vary across the disturbance gradient, and is likely to have been a much smaller component of the fishing spiders' diet than aquatic insect prey. Thus landscape-driven factors not only controlled the magnitude of resource subsidies, but also influenced the ability of consumers to respond to them by altering the physical nature of the ecosystem boundary.     

Antibiotic resistance profiles to determine sources of fecal contamination in a rural Virginia watershed

Antibiotic resistance analysis (ARA) was used to determine if enterococci of human origin were present in a stream (Spout Run) that passes through a rural nonsewered community (Millwood, VA). Millwood consists of 82 homes, all served by individual septic systems, and Spout Run drains a 5,800-ha karst topography watershed that contains large populations of livestock and wildlife. Periodic monitoring by state regulatory officials had resulted in Spout Run being placed on the Virginia impaired stream list and Millwood being categorized as an at-risk community. Stream samples were collected monthly and analyzed for fecal coliforms and enterococci (May 1999-May 2000); ARA was performed on enterococci stream isolates on a quarterly basis. All 117 stream samples were positive for fecal coliforms, and 32% exceeded the Virginia recreational water standard (1,000 fecal coliforms/100 mL). A library of 1,174 known source Enterococcus isolate antibiotic resistance profiles was constructed, and yielded correct classification rates of 94.6% for 203 human isolates, 93.7% for 734 livestock isolates, and 87.8% for 237 wildlife isolates. Antibiotic resistance analysis of 2,012 enterococcal isolates recovered from stream samples indicated isolates of human origin appeared throughout the stream as it passed through Millwood, with a yearly average of approximately 10% human, 40% wildlife, and 50% livestock. There were no human origin isolates in samples collected upstream from Millwood, and the percent human origin isolates declined downstream from Millwood. While a human signature was found in Spout Run, it was small compared with the proportion of isolates from livestock and wildlife.     

A determination of the prevalence of gender-based violence among conflict-affected populations in East Timor

The Reproductive Health Response in Conflict (RHRC) Consortium designed a standardised questionnaire to measure gender-based violence (GBV) prevalence in conflict-affected settings. A preliminary field test was undertaken July-August 2002 in one urban and one rural district in East Timor to assess the prevalence of GBV among women 18-49 years of age during and after conflict. The field test used a cross-sectional survey design with a two-stage random selection process. During the year preceding East Timor's 1999 crisis, 23.8 per cent of respondents reported physical assault by an intimate partner; this rate was not significantly different in the year preceding the survey (24.8 per cent). Assault by perpetrators outside the family declined significantly from 24.2 per cent during the crisis to 5.8 per cent post-crisis for physical assault (p<.001) and 22.7 per cent during the crisis to 9.7 per cent post-crisis for sexual assault (p=0.046). The field test stimulated and informed additional research in East Timor, and the complementary findings of these research initiatives continue to be used to develop local policies and programming to prevent and address GBV.     

Drawing the battle lines: tracing the "Science War" in the construction of the chloroform and human health risks debate

The United States Environmental Protection Agency (US EPA) and the Chlorine Chemistry Council, the Chemical Manufacturers Association, and others have been embroiled in a legal challenge concerning the US EPA's "reversal" regarding the scientific assessment of chloroform's carcinogenicity. This issue arose during the US EPA's November 1998 promulgation of a Maximum Contaminant Level Goal for chloroform in the Stage 1 Final Rules for Disinfectants and Disinfection Byproducts in drinking water. In this paper we adopt a claimsmaking approach: to trace the development and outcome of the chloroform court challenge in the USA, to examine the construction of scientific knowledge claims concerning chloroform risk assessments, and to investigate how different interpretations of scientific uncertainties regarding the evidence are contested when such uncertainties are brought into a regulatory and judicial arena. This "science war" (Chlorine Chemistry Council and others v. US EPA and others) took place in the US Court of Appeals for the District of Columbia Circuit. The scientific "authority" in the construction of scientific claims in this dispute is based on the International Life Sciences Institute expert panel report on chloroform. Examining these science wars is important because they signal critical shifts in science policy agendas. The regulatory outcome of the chloroform science war in the United States can have profound implications for the construction and acceptance of scientific claims regarding drinking water in other jurisdictions (e.g., Canada). In this challenge, we argue that the actors involved in the dispute constructed "boundaries" around accepted and credible scientific claims.     

Microspectrophotometric evidence for cone monochromacy in sharks

Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks—the rays and chimaeras—are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λ_max 484–518 nm) and cone (λ_max 532–561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.     

Modelling potential habitat for cougars in midwestern North America

Cougars (Puma concolor) are of considerable interest to wildlife biologists and the general public in midwestern North America, yet no researchers have modelled potential habitat in the region. We created a model of potential cougar habitat in 9 midwestern states using geospatial data, expert-opinion surveys, the analytical hierarchy process, and a GIS. About 8% of the study region contained highly favorable habitat (with favorability scores ≥75%) for cougars; the states of Arkansas (19%) and Missouri (16%) contained the highest proportions of potentially favorable habitat. We identified 6 large (≥2500 km² in size), contiguous areas of highly favorable habitat for cougars. Model testing procedures indicated a valid model when compared to an independent set of cougar locations, a null dataset, and similar studies. Our model is useful as a planning tool to proactively address future human-cougar conflicts should cougars re-colonize the Midwest via subadult dispersal.     

An inequality study of ambient nitrogen dioxide and traffic levels near elementary schools in the Tampa area

Environmental equity has been identified as a challenge and goal of national to global air quality management. Here, relationships between traffic-related air pollution measures and the social demographics of elementary schools are investigated. Ogawa passive samplers were used to measure ambient nitrogen dioxide (NO(2)) levels near 75 randomly selected elementary schools in the county containing Tampa, FL over one week in March 2008. Concentrations were determined using colorimetric reaction using Hach nitrite reagent and photometric detection at 545 nm. NO(2) levels, two metrics of traffic (highest annual average daily traffic count within 500 m and 1000 m), and school enrollment data by demographic subgroup (racial/ethnic and socioeconomic) were then compared. Data were analyzed for distribution statistics, linear correlations, and differences in subgroup category means. Weighted average values of NO(2) and traffic count were also calculated for each subgroup. All measured NO(2) levels were low, with a mean of 2.7 ppbv and range from 0.8 to 4.7 ppbv. Values were largest at sites near downtown. Results from all analyses show comparatively higher potential exposures to measured NO(2) and traffic count for black school children, and lower values for white and Asian or Pacific Islander school children. The economically disadvantaged and Hispanic subgroups were also associated with higher levels of NO(2) and traffic counts, but the relationship was not as strong or robust. Although measured NO(2) levels were low and the differences between groups are small, results suggest disparities by racial/ethnic and economic status in children's exposures to air pollution for the Tampa area.