Summer Sampling Period Research Articles

The elusive search for an effective repellent against voles: an assessment of anthraquinone for citrus crops

Vole (Cricetidae) girdling of tree trunks is a common form of damage experienced by tree and vine growers throughout much of the Northern Hemisphere. Management programs that effectively incorporate chemical repellents and vegetation management would be of substantial assistance to growers that experience such damage. Anthraquinone has proven effective as a repellent against voles in lab trials, yet controlled field tests of combined anthraquinone and vegetation management programs are lacking. Therefore, we established a mesocosm-based study in central California, USA, to test the efficacy of anthraquinone and vegetation management for reducing girdling damage caused by California voles Microtus californicus to Clementine citrus trees Citrus clementine under semi-field conditions. We observed a 90–100% reduction in girdling damage for trees following a single application of anthraquinone during two trials in summer and spring, respectively. Removal of vegetation around the base of trees further reduced damage during the summer sampling period, with no girdling observed on anthraquinone-treated trees that were surrounded by bare soil. We did not observe this same relationship during spring, and we observed no relationship between vegetation management in the absence of anthraquinone treatments in either seasonal trial, suggesting that vegetation management had a lesser impact on vole girdling than anthraquinone applications. We observed no decrease in efficacy of anthraquinone across the duration of both sampling periods (5–6 weeks), indicating substantial longevity for anthraquinone. Anthraquinone appears to have substantial utility for minimizing vole girdling damage. Field testing is warranted for additional mammalian species to determine potential uses for other taxa.

A network model for primary production highlights linkages between salmonid populations and autochthonous resources

AbstractSpatial variation in fish densities across river networks suggests that the influence of food and habitat resources on assemblages varies greatly throughout watersheds. Conceptual models predict that in situ primary production should vary with river characteristics, but the influence of autochthonous resource availability on the capacity for river reaches to support fish is poorly understood. We estimated primary production throughout the South Fork and Middle Fork of the John Day River, Oregon, by measuring diel cycles in dissolved oxygen (DO) during July 2013. Using these data, we (1) evaluated the extent to which juvenile salmonid abundance and resource limitation correlated with areas of high gross primary production (GPP), (2) developed models to predict GPP from both site‐level measurements and remotely sensed data, and (3) made predictions of GPP across the entirety of the Middle Fork John Day River (MFJD) network and assessed the utility of these spatially continuous predictions for describing variation fish densities at broad scales. We produced reliable estimates of GPP at sites where DO loggers were deployed using measurements of solar exposure, water temperature, and conductivity measured at each site, as well as surrogates for these data estimated from remote sensing data sources. Estimates of GPP across fish sampling sites explained, on average, 58–63% of the variation in juvenile salmonid densities during the summer sampling period, and 51–83% during the fall sampling period, while continuous network predictions of GPP explained 44% of the variation in fish densities across 29 km of the MFJD. Further, GPP explained nearly half of the variation in juvenile steelhead dietary resource limitation, as inferred from bioenergetics modeling results. These results comprise a first effort at quantifying variation in autochthonous production across an entire river network and, importantly, provide a much‐needed food‐web context for guiding more effective fish and habitat management.

Seasonal variation of nutrients and hydrological conditions in the State Marine Park of Laje de Santos (SMPLS) and adjacent continental shelf areas (South Atlantic Ocean - Brazil)

Abstract Marine parks constitute important areas for the conservation of marine life and the genetic heritage around the world. The creation of such marine parks must be accompanied by careful measures to guarantee the coexistence of natural biota and human activities in these systems. The State Marine Park of Laje de Santos (SMPLS) is so close to an industrial pole and urban area that its creation and maintenance is an example for humanity. However, no program has yet been installed for the monitoring of its biotic and abiotic water parameters. Thus, the objective of this study is to provide hydrological and hydrochemical parameters with emphasis on dissolved nutrients to establish a starting point for the monitoring of these waters. The presence of the South Atlantic Central Water (SACW) in the marine park during the spring and summer sampling periods was evidenced by the observation of low temperatures (< 17ºC) associated with salinity around 35 at the bottom of the water column, indicating a thermohaline feature. The dissolved oxygen presented high values, with few data below 4 mL L-1 occurring at the bottom of the water column. The pH was always in accordance with marine values (~8). Dissolved silicate and phosphate presented high values associated with inputs from the SACW intrusion, continental runoff and bottom resuspension processes, reaching maximum values of 15.86 and 1.23 µmol L-1, respectively. Nitrogen compounds were also associated with a natural fertilization process by the presence of the SACW at the bottom of the water column, as evidenced by the high nitrate concentrations (> 7.00 µmol L-1), while the concentration of N-ammonium (maximum 9.86 µmol L-1) demonstrated a rapid regeneration of the organic matter, mainly in the euphotic zone. Analysis of the data from summer periods revealed an annual difference, showing January 2014 to be drier than January 2015, which influenced the availability of some nutrients and the standard distribution of hydrochemical parameters in this region. The results of the distribution of hydrochemical parameters in the marine park confirms the preserved conditions of the seawater around the Laje de Santos, demonstrated by the excellent water quality, concluding the need to implant monitoring actions based on these reference data to preserve this important reserve of marine life.

Genetic analysis reveals the diversity of larval Gobiidae in a temperate estuary

Using molecular tools to examine Gobiidae, the second most abundant taxon in ichthyoplankton samples in the Gulf of Riga (Baltic Sea), the sand goby Pomatoschistus minutus was the most abundant taxon (82% of all individuals analysed), the common goby Pomatoschistus microps constituted 12% and the black goby Gobius niger 6%. The spatiotemporal distribution of P. microps and G. niger indicated a preference for habitats closer to the river inlet and their abundances increased slightly towards the end of the sampling period in summer. The species composition was interpreted in the context of the prevailing habitat conditions, characterized by extremely low water transparency, low salinity, limited spread of vegetated area and dominance of sandy-muddy substrata.

Revisited Syllidae of the English Channel coarse sediment communities

Among the polychaetes, the Syllidae comprise numerous species whose study over many years has benefitted from valuable revisions and descriptions of new species in Europe. This abundant literature proves very useful for revisiting the taxonomy and distribution of the Syllidae in the English Channel (EC), mainly as regards existing studies on coarse sediment communities in the eastern part of the Channel. This habitat is one of the most widespread in the EC and is known as favourable for the small polychaete fauna including Syllidae. A 2-year survey (winter and summer sampling periods) covering 19 stations, associated with theBranchiostoma lanceolatumcoarse sand community offshore Dieppe-Le Tréport, led to the identification of 6537 individuals from 29 taxa including 27 species. Six fine sand stations were also sampled in which only 12 individuals were collected. Among these species, seven are new for the EC polychaete fauna and six others are observed for the first time in the eastern part of the EC. All the new species for the EC are warm temperate species previously only known south of the Bay of Biscay. The Syllidae list given in Dauvinet al. (2003) has been re-analysed and amended with our list and that of the Chausey Archipelago study (Olivieret al., 2012). To date, 91 Syllidae species have been recorded in the EC and are established mostly in coarse sediments.

Spatial distribution of atmospheric PAHs and their genotoxicity in petrochemical industrialized Lanzhou valley, northwest China.

The present study investigated the spatial and seasonal variations and sources of 16 priority polycyclic aromatic hydrocarbons (PAHs) in Lanzhou, a petrochemical industrialized and the capital city of Gansu province, northwest China. The human health risks to these PAHs were assessed using an in vitro genotoxic bioassay technique. Associations among direct genotoxic potency, atmospheric PAH concentrations, and potential carcinogen risks were examined. Due to high PAH emissions from fossil fuel combustion and petrochemical industries, considerable higher PAH levels in the atmosphere were observed in Xigu district, a suburb featured by heavy petrochemical industry, compared with those collected at downtown and rural sampling sites. Ambient PAH levels at all sampling sites during the wintertime were higher than that in the summertime due to the winter domestic heating. BaP equivalent (BaPeq) concentrations in winter (41ng/m3) and summer (28ng/m3) exceeded the China's new national daily BaPeq standard. The average excess inhalation cancer risks (ECR) due to human exposure to PAHs during winter and summer sampling periods were 45-3540 cancer cases and 31-2451 cases per million people, respectively. The average ECR in the industrial area of Lanzhou valley was 1.97 (winter) and 1.88 times (summer) higher than that in other sampling areas. The higher ECR in the industrial area was resulted primarily by industrial activities and insufficient emission control measures. Extracts from passive air samples in genotoxicity SOS/umu test demonstrated that the genotoxic effect of atmospheric PAHs in Lanzhou was seasonal dependent. PAH air samples collected in winter showed more statistically significant genotoxicity, as manifested by a strong correlation between in vitro genotoxicity and atmospheric PAH concentrations. This indicates that the local residents were under higher potential cancer risk through the inhalation of ambient PAH air concentrations in Lanzhou valley during the wintertime.

Coccolithophore assemblage response to Black Sea Water inflow into the North Aegean Sea (NE Mediterranean)

This study aims to presents the species composition of living coccolithophore communities in the NE Aegean Sea, investigating their spatial and temporal variations along a north-south transect in the area receiving the inflowing surface Black Sea Water (BSW) over the deeper Levantine Water (LW) layer. Coccolithophores in the area were relatively diverse and a total of 95 species over 3 sampling periods studied were recognized using Scanning Electron Microscope (SEM) techniques. R-mode hierarchical cluster analysis distinguished two coccolithophore Groups (I, IIa, IIb, IIc) with different ecological preferences. Emiliania huxleyi was the most abundant species of Group I, whereas Syracosphaera spp., Rhabdosphaera spp. and holococcolithophores were prevailing in the highly diversified Group II assemblages. Biometric analysis conducted on E. huxleyi coccoliths from Aegean water column and Black Sea sediment trap samples, indicated that during autumn, NE Aegean specimens in samples under BSW influence were featured by unimodal distribution concerning the coccolith relative tube width, with values similar to those provided by the Black Sea specimens. In early spring, coccoliths in the stations with increased BSW influx displayed a bimodal pattern of relative tube width with smaller values found mostly in the surface layers, while the distribution became again unimodal and dominated by larger values within the deeper LW layers. In the summer period, the typical LW holococcolithophore species (Group II) presented low cell numbers in the surface layer (<20m), which is their usual ecological niche in the Aegean Sea, compared to greater depths, therefore marking LW mass flowing beneath the less saline BSW surface lid. In contrast to Black Sea early summer bloom conditions, E. huxleyi was almost absent in the NE Aegean during the summer sampling period.

Assessment of in situ fluorometry to measure cyanobacterial presence in water bodies with diverse cyanobacterial populations

A YSI EXO2 water quality sonde fitted with fluorometric sensors for chlorophyll-a (Chl-a) and phycocyanin (CPC) was used to determine its applicability in cyanobacterial quantification in three small urban ponds in Sydney, Australia displaying considerable variations in cyanobacterial community composition and abundance, as well as eukaryotic algae, turbidity and chromophoric dissolved organic matter. CPC and Chl-a measured in situ with the instrument was compared against laboratory measures of cyanobacterial biovolume over two summer sampling periods. A good correlation was found between CPC and total cyanobacterial biovolume in two of the three ponds. The poor correlation in the third was due to the frequent dominance of picoplanktonic sized cyanobacteria. CPC did not correlate well with cell counts, and Chl-a was a poor measure of cyanobacterial presence. The relationship between CPC measured by fluorometry varied according to the dominant cyanobacterial taxa present in the ponds at any one time. Fluorometry has good potential for use in environmental monitoring of cyanobacterial biovolume, but may need to be based on predetermined relations applicable to local water bodies. Management guidelines based on CPC concentrations would also enhance the usefulness of in situ CPC measurements.

Gastrointestinal nematode species diversity in Soay sheep kept in a natural environment without active parasite control

Molecular methods based on ITS2 sequence analysis were used to identify strongylid parasites and describe their diversity in a management intervention and anthelmintic drug treatment-free sheep flock. Fourteen different nematode parasite species were identified in the flock and the results showed a greater level of nematode species diversity than is normally reported in managed farmed flocks, with the presence of parasites such as Bunostomum trigonocephalum, Ostertagia leptospicularis, Spiculopteragia houdemeri and Trichostrongylus retortaeformis that are considered to be absent or rare in sheep kept in comparable localities. The implied prevalences of Haemonchus contortus in lambs, and of Trichostrongylus axei in lambs, ewes and rams, were higher than those in farmed sheep kept in similar regions, while those of Teladorsagia circumcincta and Trichostrongylus vitrinus were lower. Comparison of the patterns of nematode parasite infection between the summer and autumn sampling periods showed differences from the scenarios that are commonplace in comparable managed flocks; with T. vitrinus burdens of the lambs being higher in the summer than in the winter, and Oesophagostomum venulosum being the predominant nematode species in the adult sheep during the summer, while more-or-less absent from these groups during the winter. Rams played an important role in the epidemiology of certain parasitic nematode species. The relatively non-pathogenic O. venulosum was the only parasitic nematode species to predominate in any group during the study. This preliminary characterisation of the nematode parasite burdens of sheep extensively grazed on diverse unimproved pastures will aid in the understanding of the parasitological consequences of intensive grazing management and of the manner in which modern agriculture upsets the equilibrium between parasites and their hosts. These factors must be accounted for when defining the concept of sustainable parasite control and informing sustainability with reference to commercially efficient sheep farming.

Effects of microbial transformation on dissolved organic matter in the east Taiwan Strait and implications for carbon and nutrient cycling

Dissolved inorganic and organic carbons (DIC and DOC) provide two of the largest pools of carbon in the ocean. However, limited information is available concerning the relationship between DIC and different constituents of dissolved organic matter (DOM), such as fluorescent compounds. This study investigates the dynamics of DOM and their implications for carbon and nutrient cycling in the east Taiwan Strait, using DOC, absorption spectroscopy, and fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC). The study area was dominated by the waters from the South China Sea during the sampling period in summer 2013. The dynamics of DOM were influenced strongly by microbial activities, as indicated by the close correlations (the absolute value of r: 0.75–0.97, p < 0.001) between apparent oxygen utilization (AOU) and DOM parameters, including DOC, the absorption coefficient at 280 nm, the fluorescence intensity of protein-like component C3, and the humification index HIX. The contribution of DOC degradation to the net increase in DIC was approximately 15% and 21% in the north and the south of the east Taiwan Strait, respectively. The DIC was correlated negatively with protein-like fluorescence, revealing the production of DIC by the microbial degradation of labile components. The DIC was correlated positively with humic-like fluorescence and HIX, suggesting that the storage of carbon by produced refractory humic substances could not compensate for the release of DIC in the deeper waters. The correlations of nutrients with DOM parameters were similar to those of DIC, further indicating the profound impacts of the dynamics of labile DOM on nutrient cycling.

Carbonyls in the urban atmosphere of Monterrey, Mexico: sources, exposure, and health risk

Characteristics and sources of carbonyls in the ambient urban atmosphere of Monterrey, Mexico, were studied from April 10, 2012 to March 12, 2013. A total of 184 samples were collected using silica-gel cartridges impregnated with DNPH during morning (08:00–12:00 h) and afternoon (15:00–19:00 h) sampling periods. Samples were analyzed using high-performance liquid chromatography with an UV detector. Acetaldehyde was the most abundant carbonyl with mean concentrations of 13.08, 21.26, 12.19, and 11.78 μg m−3 for spring, summer, autumn, and winter, respectively. Corresponding seasonal concentrations of formaldehyde were 7.11, 10.42, 5.93, and 8.48 μg m−3. Both carbonyls showed a clear seasonal pattern and exhibited significantly higher levels in summer. Formaldehyde showed higher concentrations during the morning sampling period for all seasons except autumn, whereas acetaldehyde showed higher levels during the morning sampling period in summer and winter but higher concentrations during the afternoon sampling period in spring and autumn. Meteorological parameters and criteria air pollutants were measured and correlated with measured carbonyls using a principal component analysis. Prevailing winds showed that carbonyl levels were influenced by sources located to the SSE (during spring and summer), which include industrial, vehicular, and area sources. During autumn and winter, prevailing winds were from the NNE. Health risk assessment results show that values for the integrated lifetime cancer risk and non-cancer risk exceed acceptable risk levels and that long-term exposure to both carbonyls may result in a significant risk of cancer and adverse health effects.

Evaluating a sampling protocol for assessing plant diversity in prairie fens

Prairie fens are globally vulnerable wetlands that are considered a conservation priority due to threats to their high biodiversity and hydrological functions. Establishing a thorough and repeatable plant sampling protocol is critical to evaluating conservation and management initiatives. Our goal was to evaluate a sample methodology designed to assess prairie fen plant diversity and determine if it produced results (1) representative of site diversity, (2) comparable among fens, and (3) efficient to collect. Nineteen fens between 8.5 and 28.4 ha were surveyed twice within one growing season during 2012 and 2013 field seasons using an area-proportional, random design. The turnover in species between spring and summer sampling periods within a site ranged from 8 to 50 %. Sample coverage of total estimated plant species richness ranged from 84.8 to 95.0 % with a mean of 90.1 %. We compared results from our area-proportional, random design to simulated random samples of 10, 15, 20, 25, 30, 35 and 40 quadrats per site. No significant difference was found in sample coverage per fen when using sampling rates of 25, 30, or 35 quadrats per site versus the area-proportional design. Shannon’s diversity index and floristic quality index differed by sample period and number of quadrats sampled per fen. Our sample design produced acceptable levels of coverage and facilitated comparisons across fens. Our methodology could be applied to future research, restoration monitoring, and conservation planning efforts in Midwestern prairie fens.

Seasonal variations in fate and removal of trace organic chemical contaminants while operating a full-scale membrane bioreactor

Trace organic chemical (TrOC) contaminants are of concern for finished water from water recycling schemes because of their potential adverse environmental and public health effects. Understanding the impacts of seasonal variations on fate and removal of TrOCs is important for proper operation, risk assessment and management of treatment systems for water recycling such as membrane bioreactors (MBRs). Accordingly, this study investigated the fate and removal of a wide range of TrOCs through a full-scale MBR plant during summer and winter seasons. TrOCs included 12 steroidal hormones, 3 xeno-estrogens, 2 pesticides and 23 pharmaceuticals and personal care products. Seasonal differences in the mechanisms responsible for removing some of the TrOCs were evident. In particular the contribution of biotransformation and biomass adsorption to the overall removal of estrone, bisphenol A, 17β-estradiol and triclosan were consistently different between the two seasons. Substantially higher percentage removal via biotransformation was observed during the summer sampling period, which compensated for a reduction in removal attributed to biomass adsorption. The opposite was observed during winter, where the contribution of biotransformation to the overall removal of these TrOCs had decreased, which was offset by an improvement in biomass adsorption. The exact mechanisms responsible for this shift are unknown, however are likely to be temperature related as warmer temperatures can lower sorption efficiency, yet enhance biotransformation of these TrOCs.

Fish and cephalopod assemblage structure of green alga Caulerpa prolifera (Chlorophyta) meadow in the eastern Mediterranean Sea (Elounda Bay, Crete Island)

The present study investigated for the first time in the eastern Mediterranean Sea species composition, density, wet biomass and body size of fish and cephalopod species associated with a Caulerpa prolifera meadow in a shallow semi-enclosed coastal marine ecosystem (Elounda Bay, Crete Island). Quantitative sampling with a local boat seine, revealed 34 fish species belonging to 22 families and three cephalopod taxa. The number and density of species peaked during the summer sampling period due to high numbers of juveniles, while the highest wet biomass was observed during the autumn sampling period. The fish species Boops boops, Spicara smaris, Mullus barbatus and the non-indigenous Siganus luridus were dominant, making up a high proportion of the total fish fauna of the studied area. The cephalopod Sepia officinalis was the most important species, in terms of wet biomass. The results of the study indicated that the semi-enclosed coastal marine ecosystem of Elounda Bay, characterized by a dense monospecific C. prolifera bed as well as specific abiotic and biotic features could be regarded as an important habitat for the development of fish and cephalopod species, thus contributing to the conservation and maintenance of marine biological resources of the area.

Production of hydroxyl radicals from Fe-containing fine particles in Guangzhou, China

Abstract Reactive oxygen species (ROS) production from ambient fine particles has been correlated with the soluble transition metal content of PM2.5, which also has clear association with particle-mediated cardiopulmonary toxicity. Hydroxyl radical ( OH) is the most harmful ROS species through chemical reactions of redox-active particle components. Atmospheric Fe, as the dominant species of the transition metals in the atmosphere, is associated with OH generation in ambient particle extracts. Our results revealed that Fe-containing particles (18,730 in total number) contributed approximately 3.7% on average to all detected particles throughout the summer and winter sampling period in Guangzhou, which was clustered into four distinct particle classes, including Fe-rich, Metal-rich, NaK-rich and Dust-rich. Fe-rich class was the dominant one with a fraction of 61%, followed by Dust-rich (14%), Metal-rich (13%). and NaK-rich (12%). The iron oxide was enriched in the Fe-rich class. OH generation induced by Fe-containing fine particles collected in Guangzhou (GZ) was quantified in a surrogate lung fluid (SLF), and it was found that Fe-containing fine particles were generally much reactive in generating OH in the presence of four antioxidants (200 μM ascorbate, 300 μM citrate, 100 μM reduced l -glutathione, and 100 μM uric acid). The annual average OH amount produced in our samples was 132.98 ± 27.43 nmol OH mg−1 PM2.5. OH production had a clear seasonal pattern with higher amount in summer and lower in winter. By measuring the amount of total and SLF-soluble metal in our PM2.5 samples using ICP-MS, we found that ROS activities were associated with the ionizable Fe through Fenton type reactions in the Guangzhou PM2.5. Expected burdens of PM2.5 derived OH in human lung lining fluid suggests that typical daily particulate matter exposure in Guangzhou is already a concern, and it could produce much higher levels of OH, leading to higher cytotoxicity.

English

Phytophthora root rot is considered as the most damaging disease for citrus production in Morocco. Phytophthora species are generally present as propagules in citrus fields colonizing the root zone of rootstocks and representing a source of infection for the aerial parts and a risk of dissemination to new fields. This study aimed to monitor the seasonal evolution of the inoculum density of Phytophthora spp. in heavy ground at the Gharb region in Morocco in the rhizospher of two rootstocks: Citrus aurantium L. and Citrus macrophylla. Soil samples were taken at monthly intervals over a period of 14 months between April 2013 and June 2014. The inoculum density of Phytophthora species was estimated using the dilution technique in conjunction with the selective BARPHY 72 medium. Phytophthora isolates were identified based on colonies’ morphological and taxonomic criteria as well as mycelial characteristics. In both plots, Phytophthora parasitica was the predominant isolated species, followed by P. citrophthora. The inoculum density of Phytophthora fluctuated throughout sampling period in spring and summer, depending on environmental conditions, and rootstocks.

Site occupancy of foraging bats on landscapes of managed pine forest

The ability to fully evaluate potential relationships between forest management and bats is limited without information from relevant spatial scales. Further, knowledge of bat ecology in intensively managed forests is fairly limited even though these forests are a substantial portion of the forested landscape in the southeastern U.S. Therefore, we used occupancy models to examine influence of small-scale vegetation characteristics and large-scale spatial features on foraging patterns of bats within 6 managed-pine (Pinus spp.) forest landscapes in the southeastern U.S. Coastal Plain. We conducted repeated acoustic surveys to determine species presence/non-detection and evaluated a priori models relating detection probability and occupancy to site- and landscape-level metrics for 6 species/genera. Detection of big brown (Eptesicus fuscus) and eastern red (Lasiurus borealis)/Seminole (L. seminolus) bats (eastern red and Seminole bats combined) decreased with increasing basal area, and detection of big brown and Brazilian free-tailed bats (Tadarida brasiliensis) increased over the summer sampling period. Relationships between occupancy and habitat metrics were species-specific but consistent with previous studies. Occupancy for most bat species was lower at sampling sites with higher vegetation clutter and higher basal area. In contrast to most previous studies, occupancy of all bat species investigated was unrelated to or negatively influenced by distance to water. Although site- and landscape-level features influenced occupancy, our results indicate that site-specific features (vegetation clutter and basal area) influenced most species. Therefore, stand-level management activities that decrease vegetation structure, such as thinning intermediate-aged stands and/or controlling midstory vegetation (e.g., fire or herbicide applications), likely will maintain or increase suitability of managed pine forest stands and landscapes for many bat species in the southeastern Coastal Plain. The forest mosaics that we sampled, consisting primarily of managed pine stands intermingled with non-production habitat types, supported a large proportion of the bat community associated with forests of the Coastal Plain which suggests the compatibility of timber production and bat conservation objectives.

Freshwater fluxes in the Weddell Gyre: results from δ18O.

Full-depth measurements of δ(18)O from 2008 to 2010 enclosing the Weddell Gyre in the Southern Ocean are used to investigate the regional freshwater budget. Using complementary salinity, nutrients and oxygen data, a four-component mass balance was applied to quantify the relative contributions of meteoric water (precipitation/glacial input), sea-ice melt and saline (oceanic) sources. Combination of freshwater fractions with velocity fields derived from a box inverse analysis enabled the estimation of gyre-scale budgets of both freshwater types, with deep water exports found to dominate the budget. Surface net sea-ice melt and meteoric contributions reach 1.8% and 3.2%, respectively, influenced by the summer sampling period, and -1.7% and +1.7% at depth, indicative of a dominance of sea-ice production over melt and a sizable contribution of shelf waters to deep water mass formation. A net meteoric water export of approximately 37 mSv is determined, commensurate with local estimates of ice sheet outflow and precipitation, and the Weddell Gyre is estimated to be a region of net sea-ice production. These results constitute the first synoptic benchmarking of sea-ice and meteoric exports from the Weddell Gyre, against which future change associated with an accelerating hydrological cycle, ocean climate change and evolving Antarctic glacial mass balance can be determined.

Temporal changes in the sensitivity of coastal Antarctic zooplankton communities to diesel fuel: A comparison between single‐ and multi‐species toxicity tests

Despite increasing human activity and risk of fuel spills in Antarctica, little is known about the impact of fuel on Antarctic marine fauna. The authors performed both single- and multi-species (whole community) acute toxicity tests to assess the sensitivity of an Antarctic coastal zooplankton community to the water-accommodated fraction of Special Antarctic Blend diesel. Single-species tests using abundant copepods Oncaea curvata, Oithona similis, and Stephos longipes allowed comparisons of sensitivity of key taxa and of sensitivity estimates obtained from traditional single-species and more novel multi-species tests. Special Antarctic Blend diesel caused significant mortality and species compositional change in the zooplankton community within 4 d to 7 d. The sensitivity of the community also increased across the summer sampling period, with decreasing 7-d median lethal concentration (LC50) values for total petroleum hydrocarbons (TPH): 1091 µg TPH/L in early January 2011, 353 µg TPH/L in mid January 2011, and 186 µg TPH/L in early February 2011. Copepods showed similar sensitivities to Special Antarctic Blend diesel in single-species tests (7-d LC50s: O. curvata, 158 µg TPH/L; O. similis, 176 µg TPH/L; S. longipes, 188 µg TPH/L). The combined use of single- and multi-species toxicity tests is a holistic approach to assessing the sensitivity of key species and the interactions and interdependence between species, enabling a broader understanding of the effects of fuel exposure on the whole zooplankton community.

Seasonal variation and spatial distribution of atmospheric mercury and its gas-particulate partition in the vicinity of a semiconductor manufacturing complex

This study investigated the tempospatial variation of atmospheric mercury and its gas-particulate partition in the vicinity of a semiconductor manufacturing complex, where a plenty of flat-monitor manufacturing plants using elemental mercury as a light-initiating medium to produce backlight fluorescence tubes and may fugitively emit mercury-containing air pollutants to the atmosphere. Atmospheric mercury speciation, concentration, and the partition of total gaseous mercury (TGM) and particulate mercury (Hgp) were measured at four sites surrounding the semiconductor manufacturing intensive district/complex. One-year field measurement showed that the seasonal averaged concentrations of TGM and Hgp were in the range of 3.30-6.89 and 0.06-0.14ng/m(3), respectively, whereas the highest 24-h TGM and Hgp concentrations were 10.33 and 0.26ng/m(3), respectively. Atmospheric mercury apportioned as 92.59-99.01% TGM and 0.99-7.41% Hgp. As a whole, the highest and lowest concentrations of TGM were observed in the winter and summer sampling periods, respectively, whereas the concentration of Hgp did not vary much seasonally. The highest TGM concentrations were always observed at the downwind sites, indicating that the semiconductor manufacturing complex was a hot spot of mercury emission source, which caused severe atmospheric mercury contamination over the investigation region.