Slower Recovery Rate Research Articles

Leaf litter arthropod responses to tropical forest restoration.

Soil and litter arthropods represent a large proportion of tropical biodiversity and perform important ecosystem functions, but little is known about the efficacy of different tropical forest restoration strategies in facilitating their recovery in degraded habitats. We sampled arthropods in four 7‐ to 8‐year‐old restoration treatments and in nearby reference forests. Sampling was conducted during the wet and dry seasons using extractions from litter and pitfall samples. Restoration treatments were replicated in 50 × 50‐m plots in four former pasture sites in southern Costa Rica: plantation – trees planted throughout the plot; applied nucleation/islands – trees planted in patches of different sizes; and natural regeneration – no tree planting. Arthropod abundance, measures of richness and diversity, and a number of functional groups were greater in the island treatment than in natural regeneration or plantation treatments and, in many cases, were similar to reference forest. Litter and pitfall morphospecies and functional group composition in all three restoration treatments were significantly different than reference sites, but island and plantation treatments showed more recovery than natural regeneration. Abundance and functional group diversity showed a much greater degree of recovery than community composition. Synthesis and applications: The less resource‐intensive restoration strategy of planting tree islands was more effective than tree plantations in restoring arthropod abundance, richness, and functional diversity. None of the restoration strategies, however, resulted in similar community composition as reference forest after 8 years of recovery, highlighting the slow rate of recovery of arthropod communities after disturbance, and underscoring the importance of conservation of remnant forests in fragmented landscapes.

Correlation of Mycoplasma pneumoniae resistance gene detection and refractory Mycoplasma pneumoniae pneumonia

Objective To understand the correlation of gene detection of Mycoplasma pneumoniae and clinical refractory Mycoplasma pneumoniae pneumonia. Methods (1)For children with Mycoplasma pneumoniae pneumonia in our hospital with serum Mycoplasma pneumoniae antibody positive, we collected the pharyngeal swab specimens over the same period, applied nested PCR to amplify 23SrRNA gene and undergoing electrophoresis and find out 97 cases of both positive, conducted DNA sequencing analysis of macrolide resistant gene to isolate the mutants, compared clinical manifestations of drug-resistance gene group with no drug-resistance gene mutation group.(2)Ninety-seven cases of mycoplasma pneumonia(MPP)patients were devided into the general MPP group(68 cases)and refractory MPP group(29 cases), retrospectively analyzed clinical manifestation, laboratory examination and differences of imaging performance.Multivariate logistic regression analysis for the performance of refractory Mycoplasma pneumoniae pneumonia was carried out to examine whether there is relevance between the mutant of drug-resisting gene and refractory Mycoplasma pneumonia. Results (1)Seventeen of 97 cases(17.5%)were found out without mutations, the other 80 cases(82.5%)exist drug-resistance gene mutations.(2)Mutation of drug-resistance gene group showed high CRP values, heating time, hospitalization time, macrolide drug application time, application of macrolides fever time and longer cough, by statistical analysis with statistical significance, higher incidence of lobar pneumonia.(3)Compared to general MPP group, refractory MPP group showed high peripheral blood neutrophil percentage percentage, CRP, calcitonin)and lactate dehydrogenase(LDH)values, heating time, hospitalization time, macrolide drug application time, application of macrolides fever time and longer cough.There was significant difference(P<0.05); macrocyclic lactones drug application time and resistance gene mutation and refractory Mycoplasma pneumonia were correlated. Conclusion MPP drug-resistant genes are widespread.Drug resistance gene mutations group shows long clinical symptoms duration, slow recovery rate, higher CRP value, higher rates of lobar pneumonia.Compared with ordinary MPP group, there are higher drug resistance mutation rate, inflammatory indexes and lactate dehydrogenase value, large ring lactone class drugs after a longer time of cough and fever in RMPP group.Drug application time and resistant gene mutations are associated with RMPP. Key words: Refractory Mycoplasma pneumoniae pneumonia; Drug resistance; 23SrRNA gene; Mutation

Prolonged mechanical ventilation and chronic critical illness.

Intensive care medicine has grown effectively in recent decades, parallel to multiple scientific and technological advances of our society. However, patients who survive the initial insult may have significant functional dependency, with slow recovery and high mortality rates (1-3).

Effects of surface washing on the mitigation of concrete corrosion under sewer conditions

This study systematically investigated the potential of mitigating sulfide induced sewer concrete corrosion by surface washing. Washing interrupted the corrosion activity of concrete coupons by increasing the surface pH and decreasing the H2S uptake rates (SUR). The SUR recovered to the level prior to washing within 60–140 days. The slowest recovery rate was from the most severely corroded coupon. However, no significant difference was observed for concrete mass loss of the washed and unwashed coupons after 54 months. The results suggest that frequent washing at short intervals of a few months might be needed to control corrosion over a long term.

Losses and recovery of organic carbon from a seagrass ecosystem following disturbance.

Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences.

Chronotropic Incompetence and Dynamic Postexercise Autonomic Dysfunction Are Associated with the Presence and Severity of Erectile Dysfunction.

Exercise stress testing (EST) is crucial to determine cardiovascular (CV) risk in men with erectile dysfunction (ED). Low exercise workload, a slower rate of recovery following exercise, and an impaired capacity to increase heart rate (HR) during exercise testing (chronotropic incompetence) are independent predictors of adverse CV outcomes. Aim of this study was to investigate the association between ED and EST parameters. A total of 180 ED patients and 50 men without ED underwent maximal EST. Exercise parameters including exercise capacity (metabolic equivalents, METS), peak exercise time, HR at six METS, peak exercise, HR recovery (HRR) at 1 and 2 minutes and chronotropic index (CI) were evaluated in all individuals. Endothelial function was evaluated with flow-mediated dilatation (FMD) of the brachial artery. ED patients had lower peak exercise time and thus lower calculated exercise capacity (P < 0.001) and reduced CI (P < 0.01) compared to men without ED. There was a significant association of ED severity with duration of exercise, peak workload, HRR 2minutes after exercise, and CI (all P < 0.05). There also was a positive relation of HRR and CI with FMD (all P < 0.05). This study shows interrelationships between exercise capacity, HRR, CI, and ED. Abnormal HRR and CI are associated with systemic endothelial dysfunction. These findings imply pathophysiological links and may have important implications for the estimation of cardiovascular risk in ED patients.

Climatic controls on ecosystem resilience: Postfire regeneration in the Cape Floristic Region of South Africa

Conservation of biodiversity and natural resources in a changing climate requires understanding what controls ecosystem resilience to disturbance. This understanding is especially important in the fire-prone Mediterranean systems of the world. The fire frequency in these systems is sensitive to climate, and recent climate change has resulted in more frequent fires over the last few decades. However, the sensitivity of postfire recovery and biomass/fuel load accumulation to climate is less well understood than fire frequency despite its importance in driving the fire regime. In this study, we develop a hierarchical statistical framework to model postfire ecosystem recovery using satellite-derived observations of vegetation as a function of stand age, topography, and climate. In the Cape Floristic Region (CFR) of South Africa, a fire-prone biodiversity hotspot, we found strong postfire recovery gradients associated with climate resulting in faster recovery in regions with higher soil fertility, minimum July (winter) temperature, and mean January (summer) precipitation. Projections using an ensemble of 11 downscaled Coupled Model Intercomparison Project Phase 5 (CMIP5) general circulation models (GCMs) suggest that warmer winter temperatures in 2080-2100 will encourage faster postfire recovery across the region, which could further increase fire frequency due to faster fuel accumulation. However, some models project decreasing precipitation in the western CFR, which would slow recovery rates there, likely reducing fire frequency through lack of fuel and potentially driving local biome shifts from fynbos shrubland to nonburning semidesert vegetation. This simple yet powerful approach to making inferences from large, remotely sensed datasets has potential for wide application to modeling ecosystem resilience in disturbance-prone ecosystems globally.

Dominant tree species are at risk from exaggerated drought under climate change.

Predicting the consequences of climate change on forest systems is difficult because trees may display species-specific responses to exaggerated droughts that may not be reflected by the climatic envelope of their geographic range. Furthermore, few studies have examined the postdrought recovery potential of drought-susceptible tree species. This study develops a robust ranking of the drought susceptibility of 21 tree species based on their mortality after two droughts (1990s and 2000s) in the savanna of north-eastern Australia. Drought-induced mortality was positively related to species dominance, negatively related to the ratio of postdrought seedlings to adults and had no relationship to the magnitude of extreme drought within the species current geographic ranges. These results suggest that predicting the consequences of exaggerated drought on species' geographic ranges is difficult, but that dominant species like Eucalyptus with relatively slow rates of population recovery and dispersal are the most susceptible. The implications for savanna ecosystems are lower tree densities and basal area.

Combinatorial Structures of Graphene Oxide and SnO2 for Sensing various VOCs

Graphene (GR) and reduced graphene oxide (r-GO) are outstanding candidates for gas-sensing elements due to extremely high surface-to-volume ratio and excellent electrical properties [1]. Their unique and attractive properties can lead to novel sensors with minimum power consumption, room temperature sensing, and sensitivity. But limitations of slow reaction speed and recovery rate of the GR based sensors were observed [2]. The addition of metal oxide to make combinatorial structures with GR is being exploited as a potential way to overcome such limits The nanostructured metal oxides such as zinc oxide (ZnO) and tin oxide (SnO2) have been demonstrated as gas sensing materials with excellent semiconducting properties [3]. However, gas sensing of the metal oxide typically requires elevated temperatures, which causes energy consumption, and limits wide range of applications. Combination of GR/r-GO and metal oxide, especially SnO2, may present potential benefits by reducing energy consumption and enhancing response rate. Several approaches were attempted to make this combinatorial structure for gas sensing, but the approaches were mostly to utilize good electrical properties of r-GO. Few studies were conducted in applying non-treated graphene oxide (GO) for gas sensing. Since multilayer of GO has been demonstrated as good semiconducting materials [4], systematic approach to combine non-treated GO and metal oxide with changing the ratio as well as their combinatorial structures on gas sensing behaviors are investigated in this study. Combinatorial structures of GO and SnO2 were fabricated via electrophoretic deposition (EPD). The hierarchical oxide nanostructure of GO and SnO2 was analyzed by SEM and XRD as shown in Fig. 1. Mixture ratio was adjusted by adding different amount of SnO2 nanoparticles, and its effect on gas sensing behaviors was investigated. Fig. 2 shows the gas sensing behaviors of the GO/SnO2 composite films with 100 ppm of formaldehyde gas (HCHO). Gas sensing performance with non-treated GO and GO/SnO2mixture were demonstrated at room temperature. The strategies to construct combinatorial structure and their sensing behaviors in conjunction with sensing mechanisms are discussed in detail. This research was partially supported by a grant from a Strategic Research Project (2013-0132) funded by the Korea Institute of Construction Technology, and Auburn University IGP. [1] Lu, G., Ocola, L. E., & Chen, J. Applied Physics Letters, 94(8), 083111. (2009). [2] Dreyer, D. R., Park, S., Bielawski, C. W., & Ruoff, R. S. Chemical Society Reviews, 39(1), 228-240. (2010). [3] Park, H., Ahn, H., Chung, Y., Cho, S. B., Yoon, Y. S., & Kim, D. J. Materials Letters, 136, 164-167. (2014). [4] Wang, C., Yin, L., Zhang, L., Xiang, D., & Gao, R. 10(3), 2088-2106. (2010). Figure 1

NADPH oxidase 1 (Nox1)‐mediated Reactive Oxygen Species generation stimulate gut homeostasis and restitution

It is well established that physiological generation of low levels of ROS act as critical second messengers in multiple signaling pathways. These include the regulatory networks that control growth and differentiation in disparate biological systems, including the gut of many metazoans. However, the molecular mechanism of ROS production within the intestine is unknown. Recent reports have shown that the ROS‐generating enzyme NADPH oxidase 1 (Nox1) is highly expressed by colon epithelia. Here, we report that ROS generation by Nox1 in the murine colon is necessary for normal intestinal stem cell proliferation and differentiation. Gut epithelial‐specific Nox1‐null mice exhibited increased cell‐death at the base of the crypt, altered differentiation, and slower recovery rates following gut injury. Together, these results implicate Nox1 as an essential protein in epithelial cell homeostasis and response to injury, and reveal a novel mechanism for the maintenance of intestinal tissue structure.

The UK's Productivity Puzzle

The 2008 Great Recession was notable in the UK for three things: the enormity of the output shock; the muted unemployment response; and the very slow rate of recovery. We review the literature which finds most of the decline in productivity is within sector and within firm before presenting new micro-analysis of workplace-level behaviour between 2004 and 2011 to gain insights into the processes that may have contributed to this aggregate picture. We find clear evidence of labour intensification but employers appeared incapable of turning this effort into improved workplace level productivity. Widespread pay freezes and cuts were often initiated in direct response to the recession. Workplace closure rates were little different to those experienced prior to the recession, but there is some evidence of a cleansing effect with poorer performing workplaces being more likely to close. There is some evidence of labour hoarding, especially hoarding of high skilled labour: this has had no discernible impact on the rate of innovation. There is no impact of recession on either the number of HRM practices workplaces invested in, nor their returns on those investments. There is no evidence that workplaces have benefitted from Britain's labour market as indicated by using recruitment channels used by welfare recipients or the use of numerically flexible workers. On the contrary, workplaces with increasing unionisation appeared to benefit in terms of improved workplace performance.

Assessing the importance of multiple threats to an endangered globose cactus in Mexico: Cattle grazing, looting and climate change

Cacti are a priority for conservation because their slow recovery rates and high habitat specificity make their populations particularly susceptible to looters who raid their populations, anthropogenic disturbance and climate change (CC). Identifying the most damaging threat is critical to the direction and efficiency of conservation efforts. We analyzed the impacts of looting, disturbance and CC on the geographically rare globose cactus Coryphantha werdermannii in Coahuila, Northern Mexico. We collected evidence on looting and estimated the impacts of seed and adult plant extraction through demographic models. We compared 10 sites differing in disturbance intensity and analyzed the effect on plant density, size structure and reproduction. The potential distribution of C. werdermannii under current conditions and future CC was assessed through ecological niche modeling. We found that looting is mostly confined to seeds, which have little impact on population growth and therefore not responsible for population decline. As in many globose cacti, the density of C. werdermannii populations increased with disturbance, likely because cattle grazing increases recruitment rates. Contrastingly, even the most optimistic CC scenarios suggest a 90% reduction in the potential distribution area by 2050, indicating that C. werdermannii is an endangered species most threatened by CC. We suggest that relocation programs and the maintenance of livestock levels appropriate for this species (moderate-high) may effectively counteract or delay the effects of CC. Our results suggest that current efforts are devoted to relatively minor threats, while CC is neglected, and highlight the importance of formal assessments of multiple threats.

Inequities in Long-Term Housing Recovery After Disasters

Problem, research strategy, and findings: Disaster impacts result from interactions between hazard exposure, physical vulnerability, and social vulnerability. We report empirical work from 1992′s Hurricane Andrew in Miami-Dade (FL) and 2008′s Hurricane Ike in Galveston (TX) to assess long-term trends in housing recovery. Longitudinal, parcel-level data on housing units along with neighborhood sociodemographic data permit analysis of the pace of recovery for different neighborhoods, populations, and housing types. Housing recovery is highly uneven for different population groups. Unsurprisingly, damage has major consequences; even after four years, the effects of damage are evident in the rebuilding process. Social vulnerability factors play differently in different settings. In Miami, income and race and ethnicity were critical determinants of higher losses and slower recovery rates, while in Galveston income was the more critical factor, with housing in lower-income areas suffering more damage and lagging significantly in the recovery process.Takeaway for practice: Effective land use policy and building codes can reduce physical vulnerability and ultimately damage, thus enhancing resilience for all. Differentials in impact and recovery trajectories suggest that assessment and the monitoring of recovery is critical to target resources to areas that are lagging. Perhaps most important is having an effective plan in place that addresses housing recovery issues to help reduce long-term consequences. Pre-event planning for housing and social change can help support community vision and overcome inequities.

Electromechanical and atrial and ventricular antiarrhythmic actions of CIJ-3-2F, a novel benzyl-furoquinoline vasodilator in rat heart

This study was designed to examine the antiarrhythmic efficacy and the underlying mechanisms of the benzyl-furoquinoline vasodilator, CIJ-3-2F, in rat cardiac preparations. Conduction electrograms and left ventricular pressure were determined in Langendorff-perfused hearts. Action potentials were assessed with microelectrode techniques, calcium transients by fura-2 fluorescence and ionic currents by whole-cell patch-clamp techniques. In isolated hearts, CIJ-3-2F prolonged sinus cycle length, QT interval, Wenckebach cycle length, atrio-His bundle and His bundle-ventricular conduction intervals, refractory periods in atrium, AV node, His-Purkinje system and ventricle, and also increased left ventricular pressure. CIJ-3-2F reduced the incidences of both ischaemic and reperfusion-induced ventricular arrhythmias and prevented the induction of atrial tachyarrhythmias. In both atrial and papillary muscles, CIJ-3-2F decreased upstroke velocity and prolonged duration of the action potential. In ventricular myocytes, CIJ-3-2F moderately increased the amplitude of [Ca(2+)]i transients and cell shortening. CIJ-3-2F inhibited the transient outward K(+) current (Ito ) (IC₅₀ = 4.4 μM) with accelerated inactivation, a slower rate of recovery from inactivation and use-dependency. CIJ-3-2F also suppressed the steady-state outward K(+) current (Iss , IC₅₀ = 3.6 μM, maximum inhibition = 65.7%) and both the inward Na(+) current (INa , IC₅₀ = 2.8 μM) and L-type Ca(2+) current (ICa,L , IC₅₀ = 4.9 μM, maximum inhibition = 69.4%). CIJ-3-2F blocked Na(+) and Ito channels and, to some extent, also blocked Ca(2+) and Iss channels, modifying cardiac electromechanical function. These effects are likely to underlie its antiarrhythmic properties.

Effect of a pain diary use on recovery from acute low back (lumbar) sprain.

The aim of the study was to examine the effect of a daily pain diary on recovery from acute low back sprain. Pain diaries are often recommended to or used by patients suffering with acute lumbar (low back) sprain. Diaries have been shown to be associated, however, with a slower rate of recovery after whiplash (neck) injury. The effect of diary use on recovery from low back injury is unknown. Subjects with acute lumbar (low back) sprain were randomly assigned to one of the two groups: a diary group and control group. A total of 58 out of 62 initially recruited subjects were seen in follow-up 3-month post-injury, 29 in the diary group, and 29 in the control group. Data were gathered within 1 week of injury on sex, age, and Oswestry Disability Questionnaire (ODQ) scores. The diary group was asked then to keep a record of their overall pain experience, rating their pain on a scale of 1-10 on a daily basis for 4 weeks. At the outset, both groups had similar mean age, sex distribution, and mean ODQ scores. After 4 weeks of pain diary use, fewer diary group subjects reported recovery at 3 months compared with the control group (52 vs. 79 %, respectively, p < 0.05). The use of a pain diary for 4 weeks in acute lumbar sprain subjects is associated with a reduced rate of recovery.

Relating food web structure to resilience, keystone status and uncertainty in ecological responses

Food webs often include substructures that occur in much higher numbers than would be expected in random networks. These are referred to in the literature as network motifs. Here we explore how feedbacks within the most common food web motifs influence their responses to external factors such as environmental change or harvesting of species. We have used qualitative modelling approaches to demonstrate that simple three‐ and four‐member motifs that include a closed feedback loop can exhibit a diverse range of qualitative responses, some of which are non‐intuitive. The same outcomes are demonstrated to be emergent behaviors of larger food webs represented in complex ecosystem models. The sensitivity of ecological responses to small differences in food web motifs underlines the broader importance of structural uncertainty in ecological models. It is also argued that the resilience of species and their keystone status may be strongly influenced by their ecological role within particular motifs. Examples are provided from fisheries off southeastern Australian, where the slow recovery rates of some species have not previously been explained.

Fire frequency, agricultural history and the multivariate control of pine savanna understorey plant diversity

AbstractQuestionHuman‐altered disturbance regimes and agricultural land uses are broadly associated with reduced plant species diversity in terrestrial ecosystems. In this study, we seek to understand how fire frequency and agricultural land‐use history influence savanna understorey plant diversity through complex relationships (i.e. indirect effects) among multiple biophysical variables.LocationFort Bragg, NC, US, Savannah River Site, SC, US and Fort Stewart, GA, US.MethodsWe use structural equation modelling (SEM) to evaluate the relationships among six groups of predictor variables and their influence on local‐scale species richness in pine savannas at 256 sites from three locations in the southeastern USA. In the model, fire frequency and agricultural history are hypothesized to control richness through a combination of direct effects, and indirect effects mediated by resource availability, tree abundance, understorey plant abundance and the O horizon (litter and duff depth).ResultsFrequent fires promote richness by limiting tree abundance, which increases understorey abundance and reduces the O horizon. Frequent fires also limit the O horizon independent of tree abundance. Of the total positive effect of fire on richness, 70% is attributable to reductions in the O horizon and 30% to reduced tree abundance. Agricultural history has a negative effect on richness through a positive correlation with tree abundance, which decreases understorey abundance and increases the O horizon. Agricultural history has a modest negative effect on richness by reducing resource availability as well as a strong direct negative effect (38% of the total effect) that is unrelated to other modelled variables.ConclusionsThrough a multivariate framework and large‐scale data set, this study unites and tests our understanding of the factors that control plant species diversity in a fire‐dependent ecosystem. We show that the effects of fire frequency and agricultural history on richness are largely mediated through other ecosystem attributes, including vegetation structure (i.e. tree and understorey abundance), resource availability and the O horizon. Persistent, negative effects of agricultural history demonstrate the slow rates of savanna plant community recovery on post‐agricultural land and highlight the conservation value of frequently burned savanna remnants.

Blow me down: A new perspective on Aloe dichotoma mortality from windthrow

BackgroundWindthrow, the uprooting of trees during storms associated with strong winds, is a well-established cause of mortality in temperate regions of the world, often with large ecological consequences. However, this phenomenon has received little attention within arid regions and is not well documented in southern Africa. Slow rates of post-disturbance recovery and projected increases in extreme weather events in arid areas mean that windthrow could be more common and have bigger impacts on these ecosystems in the future. This is of concern due to slow rates of post-disturbance recovery in arid systems and projected increases in extreme weather events in these areas. This study investigated the spatial pattern, magnitude and likely causes of windthrown mortality in relation to other forms of mortality in Aloe dichotoma, an iconic arid-adapted arborescent succulent and southern Africa climate change indicator species.ResultsWe found that windthrown mortality was greatest within the equatorward summer rainfall zone (SRZ) of its distribution (mean = 31%, n = 11), and was derived almost exclusively from the larger adult age class. A logistic modelling exercise indicated that windthrown mortality was strongly associated with greater amounts of warm season (summer) rainfall in the SRZ, higher wind speeds, and leptosols. A statistically significant interaction term between higher summer rainfall and wind speeds further increased the odds of being windthrown. While these results would benefit from improvements in the resolution of wind and substrate data, they do support the hypothesised mechanism for windthrow in A. dichotoma. This involves powerful storm gusts associated with either the current or subsequent rainfall event, heavy convective rainfall, and an associated increase in soil malleability. Shallow rooting depths in gravel-rich soils and an inflexible, top-heavy canopy structure make individuals especially prone to windthrown mortality during storms.ConclusionsResults highlight the importance of this previously unrecognised form of mortality in A. dichotoma, especially since it seems to disproportionately affect reproductively mature adult individuals in an infrequently recruiting species. Smaller, more geographically isolated and adult dominated populations in the summer rainfall zone are likely to be more vulnerable to localised extinction due to windthrow events.

Experimental characterization of CVOC removal from fractured clay during boiling

A series of experiments was conducted to evaluate the mass transport of a chlorinated volatile organic compound (CVOC) at boiling temperatures in low permeability clays where 20–100% of the pore water was removed. A kaolin clay matrix saturated with water containing 1,2-dichloroethane (DCA) and bromide (Br−) was packed into two columnar cells, a rigid-wall and a flexible-wall tube, which created different external boundary conditions. Both cells were heated to boiling temperatures and the recovered outflow was condensed and analyzed for DCA and bromide, and the clay remaining in the cell was cooled and analyzed for water and DCA content. Clay in the vertically oriented rigid-wall cell was heated to 130°C with a power density of ∼80kW/m3 and then depressurized at its upper end. DCA was nearly completely removed in approximately 15min after 0.3 of pore volume water was recovered. The recovered condensate was enriched to more than 10 times the DCA concentration of the pore water. The flexible-wall cells were heated to 110°C with a lower power density of ∼44kW/m3. These tests resulted in slower recovery rates, and condensate concentrations that were approximately twice the pore concentration of DCA. The concentration of DCA in the clay was reduced by two orders of magnitude after approximately 0.5 of the pore volume was removed. Boiling was inferred to occur within the clay matrix because (a) DCA concentrations were enriched; (b) pressure and temperature conditions in the clay intersected the saturated vapor pressure curve; (c) Br− was absent from all but the initial outflow; (d) change in DCA and water content was roughly uniformly distributed over the length of the cell. Fractures appeared to have formed during heating, increasing the permeability, dropping the internal pressure and enabling stripping of DCA during boiling.

Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea

Abstract. Deep-sea ecosystems are in general adapted to a limited variability of physical conditions, resulting in high vulnerability and slow recovery rates from anthropogenic perturbations such as bottom trawling. Commercial trawling is the most recurrent and pervasive of human impacts on the deep-sea floor, but studies on its consequences on the biogeochemistry of deep-sea sediments are still scarce. Pigments, fatty acids, amino acids and carbohydrates were analysed in sediments from the flanks of the La Fonera (Palamós) submarine canyon (NW Mediterranean Sea), where a commercial bottom trawling fishery has been active for more than 70 yr. More specifically, we investigated how trawling-induced sediment reworking affects the quality of sedimentary organic matter which reaches the seafloor and accumulates in the sediment column, which is fundamental for the development of benthic communities. Sediment samples were collected during two oceanographic cruises in spring and autumn 2011. The sampled sites included trawl fishing grounds as well as pristine (control) areas. We report that bottom trawling in the flanks of the La Fonera Canyon has caused an alteration of the quality of the organic matter accumulated in the upper 5 cm of the seafloor. The use of a wide pool of biochemical tracers characterized by different reactivity to degradation allowed for us to discriminate the long-term effects of trawl-induced sediment reworking from the natural variability caused by the seasonal cycle of production and sinking of biogenic particles. Differences between untrawled and trawled areas were evidenced by labile amino acids, while differences between spring and autumn samples were detected only by the more labile indicators chlorophyll a and monounsaturated fatty acids. These results suggest that changes in the biochemical composition of the sedimentary organic matter caused by bottom trawling can be more relevant than those associated with natural seasonality and pose serious concerns about the ecological sustainability of deep-sea trawling activities.