Our current understanding of the cosmic star formation history at
z
> 3 is primarily based on UV-selected galaxies (Lyman-break galaxies, i.e., LBGs). Recent studies of
H
-dropouts (HST-dark ...galaxies) have revealed that we may be missing a large proportion of star formation that is taking place in massive galaxies at
z
> 3. In this work, we extend the
H
-dropout criterion to lower masses to select optically dark or faint galaxies (OFGs) at high redshifts in order to complete the census between LBGs and
H
-dropouts. Our criterion (
H
> 26.5 mag & 4.5 < 25 mag) combined with a de-blending technique is designed to select not only extremely dust-obscured massive galaxies but also normal star-forming galaxies (typically
E
(
B
−
V
) > 0.4) with lower stellar masses at high redshifts. In addition, with this criterion, our sample is not contaminated by massive passive or old galaxies. In total, we identified 27 OFGs at
z
phot
> 3 (with a median of
z
med
= 4.1) in the GOODS-ALMA field, covering a wide distribution of stellar masses with log(
M
⋆
/
M
⊙
) = 9.4 − 11.1 (with a median of log(
M
⋆med
/
M
⊙
) = 10.3). We find that up to 75% of the OFGs with log(
M
⋆
/
M
⊙
) = 9.5 − 10.5 were neglected by previous LBGs and
H
-dropout selection techniques. After performing an optical-to-millimeter stacking analysis of the OFGs, we find that rather than being limited to a rare population of extreme starbursts, these OFGs represent a normal population of dusty star-forming galaxies at
z
> 3. The OFGs exhibit shorter gas depletion timescales, slightly lower gas fractions, and lower dust temperatures than the scaling relation of typical star-forming galaxies. Additionally, the total star formation rate (SFR
tot
= SFR
IR
+ SFR
UV
) of the stacked OFGs is much higher than the SFR
UV
corr
(SFR
UV
corrected for dust extinction), with an average SFR
tot
/SFR
UV
corr
= 8 ± 1, which lies above (∼0.3 dex) the 16–84th percentile range of typical star-forming galaxies at 3 ≤
z
≤ 6. All of the above suggests the presence of hidden dust regions in the OFGs that absorb all UV photons, which cannot be reproduced with dust extinction corrections. The effective radius of the average dust size measured by a circular Gaussian model fit in the
uv
plane is
R
e(1.13 mm)
= 1.01 ± 0.05 kpc. After excluding the five LBGs in the OFG sample, we investigated their contributions to the cosmic star formation rate density (SFRD). We found that the SFRD at
z
> 3 contributed by massive OFGs (log(
M
⋆
/
M
⊙
) > 10.3) is at least two orders of magnitude higher than the one contributed by equivalently massive LBGs. Finally, we calculated the combined contribution of OFGs and LBGs to the cosmic SFRD at
z
= 4 − 5 to be 4 × 10
−2
M
⊙
yr
−1
Mpc
−3
, which is about 0.15 dex (43%) higher than the SFRD derived from UV-selected samples alone at the same redshift. This value could be even larger, as our calculations were performed in a very conservative way.
We analyzed liver samples from 322 ringed seals (Pusa hispida) collected from Cumberland Sound (southeast Baffin Island) to test our ability to differentiate between carbon sources in near apex ...predators. Highly branched isoprenoids (HBIs) were present in all samples, and their distributions were consistent with recognized seal habitat use. HBI distributions in mature seals (≥ 5 yr) confirmed a less variable carbon source during winter, consistent with geographically restricted sexually mediated territorialism. In contrast, HBI distributions were more variable for immature seals (< 5 yr old), consistent with increased movements and body growth–mediated habitat selection. The ubiquitous presence of sea ice–derived HBIs (e.g., the ‘Ice Proxy with 25 carbons’) in every seal collected throughout January–December indicates that springtime sea ice primary production remains important for ringed seals throughout the year. HBI distributions remain largely unaltered by trophic transfer, enabling them to document short-term (< 4 weeks) and seasonal changes in carbon. This important characteristic of HBIs facilitated interpretation of sea ice–derived carbon use by seals over annual and interannual timeframes and identified strong associations between sea ice carbon use and insolation as well as sea ice extent. Analysis of HBI distributions could be used to monitor and predict the response of Arctic organisms to reducing sea ice extent and the associated decline in future sea ice primary production over a range of temporal scales.
Killer whales (
Orcinus orca
) occur in the eastern Canadian Arctic during the open-water season, but their seasonal movements in Arctic waters and overall distribution are poorly understood. During ...August 2009, satellite transmitters were deployed onto two killer whales in Admiralty Inlet, Baffin Island, Canada. A whale tracked for 90 days remained in Admiralty and Prince Regent Inlets from mid-August until early October, when locations overlapped aggregations of marine mammal prey species. While in Admiralty and Prince Regent Inlets, the whale traveled 96.1 ± 45.3 km day
−1
(max 162.6 km day
−1
) and 120.1 ± 44.5 km day
−1
(max 192.7 km day
−1
), respectively. Increasing ice cover in Prince Regent Inlet in late September and early October was avoided, and the whale left the region prior to heavy ice formation. The whale traveled an average of 159.4 ± 44.8 km day
−1
(max 252.0 km day
−1
) along the east coast of Baffin Island and into the open North Atlantic by mid-November, covering over 5,400 km in approximately one month. This research marks the first time satellite telemetry has been used to study killer whale movements in the eastern Canadian Arctic and documents long-distance movement rarely observed in this species.
Metal halide lights are currently used as standard in commercial Atlantic salmon sea cages as a means of enhancing productivity through grilse inhibition. However, such systems create bright point ...light sources that are neither environment specific nor species specific and could potentially compromise fish welfare. Light emitting diodes (LEDs) are a new form of lighting technology currently being developed for the fish farming industry that can be tuned to environment and species sensitivities through narrow bandwidth outputs. However, prior to implementing these new high energy alternatives, any potential adverse effects must be determined in fish. The objectives of this study were thus (1) to determine the effect of increasing intensities of blue LED light (0.199–2.7 W m
−
2, at 0.1 m from the light source) on light perception and stress response
, and (2) to examine potential retinal damage under these conditions in post-smolt Atlantic salmon,
Salmo salar. A white LED light was also tested, as well as a very high intensity metal halide positive control. Results demonstrated firstly that salmon perceived blue LED light (basal melatonin levels maintained) irrespective of intensity. Secondly, fish exposed to high intensity blue LED light showed an increase in plasma cortisol and glucose levels within 3 h, returning to a basal state 24 h post-light onset. This typical acute stress response was not observed in fish exposed to the white LED light and lower blue light intensities which could indicate differential sensitivities to spectral content of the light. No effects on the non-specific immune system (lysozyme activity) were observed. Finally, extensive histological examination of the retina from fish exposed to these various light treatments revealed no signs of damage. This demonstrates the efficiency of the adaptive mechanisms to light developed in fish.
In situ chemical oxidation (ICO) has been identified as a potential technology for the remediation of petroleum hydrocarbon contaminated sites in Antarctica. ICO involves introducing reactive ...chemicals to contaminated soils so that organics such as petroleum hydrocarbons are oxidised to environmentally innocuous compounds. This paper details two field trials that were undertaken to evaluate the feasibility of using a surface application of these oxidative treatments (Fenton's reagent, hydrogen peroxide and sodium hypochlorite) to remediate petroleum contaminated soil at Old Casey Station, East Antarctica. Results show that the ICO technology used at this site, where contamination occurred over a decade ago, did not significantly reduce petroleum hydrocarbon concentrations and would likely hinder biodegradation through the destruction of subsurface microbial communities. Further treatment testing and optimisation is required before ICO would be an effective remediation strategy for petroleum contaminated sites in Antarctica. However, the near complete destruction of subsurface microbiota, coupled with a discoloured orange soil residue and soil heating, mean that other more environmentally sensitive techniques such as bioremediation are our preferred treatment methodology.
Chinook salmon from New Zealand were shown to have a generalized membranous glomerulonephritis that was most severe in large fish. Marked thickening of the glomerular basement membrane was the most ...consistent lesion, with the presence of an electron‐dense deposit beneath the capillary endothelium. Severely affected glomeruli also had expansion of the mesangium and loss of capillaries, synechiae of the visceral and parietal epithelium and mild fibrosis of Bowman’s capsule. Chinook salmon from British Columbia, Canada with bacterial kidney disease caused by Renibacterium salmoninarum had similar histological lesions. They also had thickened glomerular basement membranes that were recognized by rabbit antiserum to rainbow trout immunoglobulin. This was true only when frozen sections of kidney were used and not formalin‐fixed tissue. An attempt to experimentally produce a glomerulopathy in rainbow trout by repeated immunization with killed R. salmoninarum was not successful. Case records from the Fish Pathology Laboratory at the University of Guelph over a 10‐year period revealed that a range of species were diagnosed with glomerulopathies similar to those seen in Chinook salmon. The majority of these cases were determined to have chronic inflammatory disease. This report has identified the presence of immunoglobulin within thickened basement membranes of Chinook salmon with glomerulonephritis and supports the existence of type III hypersensitivity in fish.
Recent unidirectional climatic trends and changes in top predator population ecology suggest that long-term modifications may be happening in Hudson Bay, Canada. Effects of such changes on ...ice-obligated seal populations are expected but long-term studies are required to differentiate climate-induced changes from natural variation. We conducted strip-transect surveys in late spring in 1995–1997, 1999–2000 and 2007–2008 to estimate distribution, density and abundance of ice-obligated ringed (
Phoca hispida
) and bearded (
Erignathus barbatus
) seals in western Hudson Bay. When hauled out, ringed seals preferred land-fast and consolidated pack ice, whereas bearded seals preferred unconsolidated pack ice. Bearded and ringed seal density estimates varied from 0.0036 to 0.0229 seals/km
2
of ice and from 0.46 to 1.60 seals/km
2
of ice, respectively. Strong inter-annual variations were recorded in the abundance estimates of both species, with the largest abundance estimates in 1995 (104,162 and 1,494 ringed and bearded seals, respectively) and the lowest in 2008 for ringed seals (33,701) and 1997 for bearded seals (278). A sine function best described seal density estimates in western Hudson Bay and suggested a decadal cycle. Previous studies that reported low ringed seal demographic parameters in the 1990s and a recovery in the 2000s supported our interpretation of the survey results. We discuss our results in the context of climate warming and suggest that a long-term decline in ice-obligated seal density estimates may overlay a possible natural decadal cycle.
We present the results of a new, ultra-deep, near-infrared imaging survey executed with the Hawk-I imager at the ESO VLT, of which we make all the data (images and catalog) public. This survey, named ...HUGS (Hawk-I UDS and GOODS Survey), provides deep, high-quality imaging in the K and Y bands over the portions of the UKIDSS UDS and GOODS-South fields covered by the CANDELS HST WFC3/IR survey. In this paper we describe the survey strategy, the observational campaign, the data reduction process, and the data quality. We show that, thanks to exquisite image quality and extremely long exposure times, HUGS delivers the deepest K-band images ever collected over areas of cosmological interest, and in general ideally complements the CANDELS data set in terms of image quality and depth. In the GOODS-S field, the K-band observations cover the whole CANDELS area with a complex geometry made of 6 different, partly overlapping pointings, in order to best match the deep and wide areas of CANDELS imaging. In the deepest region (which includes most of the Hubble Ultra Deep Field) exposure times exceed 80 hours of integration, yielding a 1 − σ magnitude limit per square arcsec of ≃28.0 AB mag. The seeing is exceptional and homogeneous across the various pointings, confined to the range 0.38–0.43 arcsec. In the UDS field the survey is about one magnitude shallower (to match the correspondingly shallower depth of the CANDELS images) but includes also Y-band band imaging (which, in the UDS, was not provided by the CANDELS WFC3/IR imaging). In the K-band, with an average exposure time of 13 hours, and seeing in the range 0.37–0.43 arcsec, the 1 − σ limit per square arcsec in the UDS imaging is ≃27.3 AB mag. In the Y-band, with an average exposure time ≃8 h, and seeing in the range 0.45–0.5 arcsec, the imaging yields a 1 − σ limit per square arcsec of ≃28.3 AB mag. We show that the HUGS observations are well matched to the depth of the CANDELS WFC3/IR data, since the majority of even the faintest galaxies detected in the CANDELS H-band images are also detected in HUGS. Finally we present the K-band galaxy number counts produced by combining the HUGS data from the two fields. We show that the slope of the number counts depends sensitively on the assumed distribution of galaxy sizes, with potential impact on the estimated extra-galactic background light.
Narwhals (
Monodon monoceros
) are an entirely arctic odontocete, living in upwards of 95 % pack ice and complete darkness over the winter. As a result of the harsh conditions in which they live, ...there are few studies of their social structure; however, it has been hypothesized that narwhals display a matrilineal social structure where pods are centered on the mother. A fortuitous opportunity arose to study social structure when an ice entrapment event near the community of Pond Inlet, Nunavut, Canada captured many females and their offspring. Using genetic analyses and fatty acids as a dietary marker, we investigated whether individuals that are closely related forage together, which would support a matrilineally driven social structure where females teach their young foraging strategies, and/or travel and forage together. We found no evidence that genetic relatedness was correlated with the fatty acid biomarkers, which provides some evidence against a matrilineal social structure. The possibility of narwhals displaying a fission–fusion societal structure is discussed, but further observational and experimental techniques are needed to support or refute this hypothesis.
In South Africa, particularly Gauteng Province, populations of the large, explosive-breeding Giant Bullfrog (Pyxicephalus adspersus) are suffering increasing habitat loss due to encroaching ...urbanization. To investigate the spatial habitat requirements of this regionally threatened species, 70 adult frogs were radio- or spool-tracked during five summers around a periurban breeding site. Male and female P. adspersus moved a maximum overnight distance of 350 m when returning to their burrows postspawning. On average, animals of either sex used one long-term burrow (LTB) in a summer. Four males each used a single LTB or burrowing area for two or three consecutive summers. The LTBs of females were situated almost 4 times further (mean = 446.8 m) from the seasonal dams where spawning occurred than those of males (mean = 131.0 m). Female body condition was significantly positively correlated with distance of their burrows from the seasonal dams (rs = 0.77). Limited evidence indicated that adult P. adspersus probably forage mostly within 20 m of their burrows. To protect the LTBs of all radiotracked animals a 950-1,000-m wide buffer would be necessary around the seasonal dams. Because adult P. adspersus seem to be philopatric, juvenile dispersal is predicted to be largely responsible for gene flow among populations.
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