Substrate size mediates thermal stress in the rocky intertidal

Variation in physical factors, such as slope, orientation, and wind exposure, shapes thermal conditions. Variation in substrate size is common in many habitats, but its thermal consequences for organisms are not well characterized. Larger substrates should remain more thermally stable and act as thermal refuges for associated organisms during short, thermally stressful periods such as midday temperature peaks or tidal exposure. In observations and a transplant and thermal integration experiment, we found that larger rock substrates stayed cooler and facilitated greater survival of the barnacle Semibalanus balanoides in the high intertidal relative to small substrates during the hot summer months in southern New England, USA. However, in thermally benign northern New England, rock substrate size had no effect on barnacle distributions, indicating that the thermal effects of substrate size are mediated by regional climate.     

Anaerobic degradation of naphthalene in a fluvial aquifer: a radiotracer study

A radiotracer study was conducted in a creosote-contaminated aquifer beneath the Fraser River, British Columbia Canada to investigate the in situ degradation of naphthalene. The groundwater is anaerobic, with abundant methane, ferrous iron and carbon dioxide. This study followed earlier work at the site where the contaminant distribution could only be explained by invoking a mass loss through degradation, even though extensive field and laboratory microcosm studies closer to the source zone onshore could not confirm degradation. Accordingly, 14C-naphthalene was injected into the aquifer offshore, further from the source zone where modeling suggested degradation was occurring. During the 230-day monitoring period, 14CO2 was detected, confirming the degradation of the radio-labeled naphthalene tracer. A zero-order degradation rate of naphthalene of 5 microg/L-day was estimated based on the decrease in 14C-naphthalene concentration with time. While the degradation pathway could not be determined from the radiotracer study alone, the geochemistry of the site suggests that either iron reduction or methanogenesis is the terminal electron accepting processes responsible for naphthalene oxidation.     

Alternative method of groundwater sparging for petroleum hydrocarbon remediation

An alternative method of in-situ groundwater sparging, termed density-driven convection (patent pending), is presented. This method has been successfully used to remediate eight underground storage tank releases involving a wide distillation range of petroleum hydrocarbons (gasoline to waste oil) and in a variety of site soils (clay to sandy gravel). Application of the density-driven convection method is detailed in a case study. The system, installed to remediate a gasoline and diesel release from an underground storage tank, was operated and monitored for a period of one year. Monitoring data indicate reductions in total petroleum hydrocarbon concentrations in groundwater and in soil. Concentrations of aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylenes, and naphthalene) also decreased in both media. Stimulation of natural biodegradation, the primary mechanism of removal, occurred rapidly. Natural biological activity gradually declined over the subsequent 150 days. After one year of operation, the sparging system has achieved or is rapidly approaching the regulatory cleanup goals for both soil and groundwater, including reduction of dissolved concentrations below maximum contaminant levels established under the Safe Drinking Water Act.     

Prevalence and drivers of poison use by South African commercial farmers and perceptions of alternative livestock protection measures

The use of poison to eliminate predators is causing African vulture populations to collapse. To understand the prevalence and motivations of this practice we conducted an extensive survey with South African commercial farmers. Using a specialised questioning technique and ad hoc quantitative methods we found that an estimated 22% and 31% of farmers used poison over a 1-year and 5-year period, respectively. Poison use hotspots generally coincided with small stock farming areas. The strongest predictor of poison use was whether farmers believed the practice to be common amongst their peers. Our results suggest that farmers’ attitudes to vultures are primarily positive, and farmers are less likely to use poisons if they frequently encounter vultures on their farm. Overall, our findings provide an understanding on poison use that provides leverage points to change farmers’ behaviour and help avert the African vulture crisis and possible cascading ecosystem impacts.Supplementary informationThe online version of this article (10.1007/s13280-020-01461-2) contains supplementary material, which is available to authorized users.     

Ecosystem service lens reveals diverse community values of small-scale fisheries

The ocean provides benefits to coastal communities around the world, however, the depth and complexity of people’s interactions with marine ecosystems are not well represented in many marine management initiatives. Many fisheries are managed to maximize provisioning value, which is readily quantified, while ignoring cultural values. An ecosystem services approach that includes both provisioning and cultural services will enable managers to better account for the diverse values marine fisheries provide to coastal communities. In this study, we assess community values related to a top fished species, the Mexican chocolate clam, Megapitaria squalida, in Loreto, Baja California Sur, Mexico. We conducted an exploratory analysis based on 42 household surveys, and found that community members perceive multiple provisioning and cultural benefits from the clam, including community economic, historical, and identity values. Despite reporting infrequent harvest and consumption of clams, participants perceive the species as an important part of community identity, highlighting the role of Mexican chocolate clams as a cultural keystone species in the Loreto region. Fisheries management that recognizes the full range of ecosystem services a species contributes to coastal communities will be better equipped to sustain these diverse values into the future.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01405-w) contains supplementary material, which is available to authorized users.     

Volatiles from the bark of trembling aspen, Populus tremuloides Michx. (Salicaceae) disrupt secondary attraction by the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae)

Summary. Coupled gas chromatographic-electroantennographic detection (GC-EAD) analysis of the Porapak Q-captured volatiles from the bark of trembling aspen, Populus tremuloides Michx., revealed four compounds that consistently elicited antennal responses by mountain pine beetles (MPBs), Dendroctonus ponderosae Hopkins. One of these, 1-hexanol, disrupted the capture of MPBs in multiple-funnel traps baited with the aggregation pheromones trans-verbenol and exo-brevicomin and the host kairomone myrcene, a blend of semiochemicals that mediates the secondary attraction response in which beetles mass attack and kill living pines. The other three EAD-active aspen bark volatiles, benzyl alcohol, benzaldehyde and nonanal, were inactive alone, but in binary and ternary combinations contributed to a disruptive effect in an additive and redundant manner when all four aspen bark volatiles were tested in all possible binary and ternary blends. The best ternary blend and the quarternary blend achieved ≥ 80% disruption. The quarternary blend enhanced the disruptive effect of the antiaggregation pheromone verbenone in traps, raising the disruptive effect to 98%, and also enhanced the inhibition of attack on attractant-baited lodgepole pines. This is the first demonstration of specific compounds from the bark of angiosperm trees that disrupt the secondary attraction response of sympatric coniferophagous bark beetles. The results support the hypothesis that such bark beetles are adapted to recognize and avoid non-host angiosperm trees by responding to a broad spectrum of volatiles that can act in various blends with equal effect. Received 27 October 1997; accepted 20 February 1998.     

SCALE PROBLEMS IN INTERDISCIPLINARY WATER RESOURCES INVESTIGATION1

ABSTRACT The problems encountered in estimating scale parameters in interdisciplinary watershed research are discussed. Meteorology, hydrology, geology and water quality are discussed with respect to their individual strengths and weaknesses when applied to different scale problems. Areas where incompatibilities exist are pointed out and suggestions are made for effecting compromise. A watershed scale of roughly a hundred acres may be the scale at which all disciplines can effect optimum interaction.     

Elemental composition of Jamaican foods 1: A survey of five food crop categories

The concentrations of 27 elements in Jamaican food categories consisting of fruit, legumes, leafy and root vegetables and other root crops are reported. The main analytical techniques used were neutron activation analysis and flame and graphite furnace atomic absorption spectrophotometry. The results are compared, where possible, with values from Denmark, the United Kingdom, the United States and Nigeria, and with some regulatory limits. Over 75% of the results for antimony, arsenic, barium, cerium, thorium and uranium were below the respective sample detection limits but even among these, some of the maximum values observed indicate that further examination may be useful for those foods grown in the regions of highest uptake and consumed in large amounts. The other elements reported are bromine, cadmium, calcium, caesium, cerium, chromium, copper, europium, hafnium, iron, lanthanum, lead, magnesium, manganese, phosphorus, potassium, rubidium, scandium, samarium, sodium, strontium, thorium, uranium, and zinc. Many of these elements occur at concentration levels above those reported from the other countries but it seems unlikely that most of these will contribute significantly to public health risk. However, at this stage cadmium clearly appears to be the element of greatest concern in the Jamaican food chain. The observed range of cadmium concentrations suggests that factors such as land selection, coupled perhaps where necessary, with suitably modified agricultural practices, is a feasible way to reduce the cadmium content of certain local foods.     

Characterization and phosphate stabilization of dusts from the vitrification of MSW combustion residues

The use of soluble PO₄³⁻ as a heavy metal chemical stabilization agent was evaluated for a dust generated from melting or vitrification of municipal solid waste combustion residues. Vitrification dusts contain high concentrations of volatile elements such as Cl, Na, K, S, Pb, and Zn. These elements are present in the dusts largely as simple salts (e.g. PbCl₂, ZnSO₄) which are highly leachable. At an experimental dose of 0.4 moles of soluble PO₄³⁻ per kg of residue, the pH-dependent leaching (pH 5,7,9) showed that the treatment was able to reduce equilibrium concentrations by factors of 3 to 100 for many metals; particularly Cd, Cu, Pb and Zn. Bulk and surface spectroscopies showed that the insoluble reaction products are tertiary metal phosphate [e.g. Zn₃(PO₄)₂] and apatite [e.g. Pb₅(PO₄)₃Cl] family minerals. Geochemical thermodynamic equilibrium modeling showed that apatite family and tertiary metal phosphate phases act as controlling solids for the equilibrium concentrations of Ca²⁺, Zn²⁺, Pb²⁺, Cu²⁺, and Cd²⁺ in the leachates during pH-dependent leaching. Both end members and ideal solid solutions were seen to be controlling solids. Soluble phosphate effectively converted soluble metal salts into insoluble metal phosphate phases despite the relatively low doses and dry mixing conditions that were used. Soluble phosphate is an effective stabilization agent for divalent heavy metals in melting dusts where leachable metals are present in high concentrations.