Entanglement‐scar acquisition rates and scar frequency for Bering‐Chukchi‐Beaufort Seas bowhead whales using aerial photography

The Bering‐Chukchi‐Beaufort Seas (BCBS) bowhead whale (Balaena mysticetus) has been considered at low‐risk for entanglement injuries and ship strikes because their range is mainly north of commercial fisheries; nevertheless, changes to their arctic habitat, including a longer open water period and declining sea ice, have resulted in increasing commercial activity and concern about fisheries interactions. We examined interyear matches (between 1985 and 2011) from a photo identification project and identified whales that had acquired entanglement injuries. We estimated the probability of a bowhead acquiring an entanglement injury using two statistical methods: interval censored survival analysis and a simple binomial model. Both methods give similar results, suggesting a 2.2% (95% CI: 1.1%–3.3%) annual probability of acquiring a scar. We also include an entanglement scar frequency analysis of aerial photographs from the 2011 spring and fall surveys near Point Barrow, Alaska, which suggest 12.4% of live bowheads show evidence of entanglement scarring. Entanglement rates for the BCBS bowhead stock are lower than many other large whale stocks, and abundance has increased over the past 35 yr; however, our findings indicate that fishing gear entanglement is a more serious concern for the BCBS bowhead whale population than previously thought.     

Effects of fleas on nest success of Arctic barnacle geese: experimentally testing the mechanism

Parasites have detrimental effects on their hosts’ fitness. Therefore, behavioural adaptations have evolved to avoid parasites or, when an individual is already in contact with a parasite, prevent or minimize infections. Such anti‐parasite behaviours can be very effective, but can also be costly for the host. Specifically, ectoparasites can elicit strong host anti‐parasite behaviours and interactions between fleas (Siphonaptera) and their hosts are one of the best studied. In altricial bird species, nest fleas can negatively affect both parent and offspring fitness components. However, knowledge on the effects of fleas on precocial bird species is scarce. Research on geese in the Canadian Arctic indicated that fleas have a negative impact on reproductive success. One possible hypothesis is that fleas may affect female incubation behaviour. Breeding females with many fleas in their nest may increase the frequency and/or duration of incubation breaks and could even totally desert their nest. The aim of our study was to 1) determine if a similar negative relationship existed between flea abundance and reproductive success in our study colony of Arctic breeding barnacle geese Branta leucopsis and 2) experimentally quantify if such effects could be explained by a negative effect of nest fleas on female behaviour. We compared host anti‐parasite and incubation behaviour between experimentally flea‐reduced and control nests using wildlife cameras and temperature loggers. We found that flea abundance was negatively associated with hatching success. We found little experimental support, however, for changes in behaviour of the breeding female as a possible mechanism to explain this effect.     

The influence of predator community composition on photoprotective traits of copepods

Trait expression of natural populations often jointly depends on prevailing abiotic environmental conditions and predation risk. Copepods, for example, can vary their expression of compounds that confer protection against ultraviolet radiation (UVR), such as astaxanthin and mycosporine‐like amino acids (MAAs), in relation to predation risk. Despite ample evidence that copepods accumulate less astaxanthin in the presence of predators, little is known about how the community composition of planktivorous fish can affect the overall expression of photoprotective compounds. Here, we investigate how the (co‐)occurrence of Arctic charr (Salvelinus alpinus) and threespine stickleback (Gasterosteus aculeatus) affects the photoprotective phenotype of the copepod Leptodiaptomus minutus in lake ecosystems in southern Greenland. We found that average astaxanthin and MAA contents were lowest in lakes with stickleback, but we found no evidence that these photoprotective compounds were affected by the presence of charr. Furthermore, variance in astaxanthin among individual copepods was greatest in the presence of stickleback and the astaxanthin content of copepods was negatively correlated with increasing stickleback density. Overall, we show that the presence and density of stickleback jointly affect the content of photoprotective compounds by copepods, illustrating how the community composition of predators in an ecosystem can determine the expression of prey traits that are also influenced by abiotic stressors.     

Reproductive investment and parental roles in Sabine's gulls<Emphasis Type="Italic"> Xema sabini</Emphasis>

More than 90% of avian species exhibit biparental care, though parental activities are often shared unequally between the members of a pair. Among gull species (Laridae), males and females generally share parental activities, although there appear to be considerable differences between species in the relative contribution of each sex. This study examined the behaviour of male and female Sabine's gulls (Xema sabini) during the incubation period and immediately post-hatch; particularly the amount of time they each invested in breeding activities. Although considered an aberrant species in aspects of behaviour and biology, the Sabine's gull showed a high reproductive investment by both sexes, as other gull species do. Males fed females prior to egg laying and contributed equally to incubation and chick provisioning, and females contributed equally to nest defence. Overall, there was no difference between the sexes in the extent of their contributions to parental care, although there was considerable individual variation within pairs. Sabine's gulls are Arctic breeders and the extent of their contributions to parental activities could have been influenced by their extreme breeding environment and short breeding season.     

Moisture Effects on Temperature Sensitivity of CO<Subscript>2</Subscript> Exchange in a Subarctic Heath Ecosystem

Carbon fluxes between natural ecosystems and the atmosphere have received increased attention in recent years due to the impact they have on climate. In order to investigate independently how soil moisture and temperature control carbon fluxes into and out of a dry subarctic dwarf shrub dominated heath, monoliths containing soil and plants were incubated at three different moisture levels and subjected to four different temperature levels between 7 and 20 °C. Ecosystem CO₂ exchange was monitored continuously day and night during the 16 to 18 days that each of three experiments lasted. Additionally, the carbon allocation pattern of the plants was investigated by labelling monoliths with ¹⁴CO₂ followed by harvest of above and below ground plant parts. The results revealed that the three different soil moisture levels caused distinctly differing levels of CO₂ fluxes. Also, both carbon fixation calculated as gross ecosystem production (GEP) and carbon release measured as ecosystem respiration (ER) increased with increasing temperatures, with ER increasing faster than GEP. Hence, short term carbon loss from the ecosystem accelerated with raised temperatures. Temperature sensitivity of the ecosystem was dependent on the soil moisture level, shown by differing Q10 values of both GEP and ER at different soil moisture levels. It is therefore highly important to take soil moisture levels into consideration when evaluating responses of ecosystem carbon balance to changes in temperature. The greatest C fixation took place via the two most dominant species of the ecosystem, Vaccinium uliginosum and Empetrum hermaphroditum, with the former being responsible for the different size of C fixation at the three moisture levels.     

Modeling Sustainability of Arctic Communities: An Interdisciplinary Collaboration of Researchers and Local Knowledge Holders

How will climate change affect the sustainability of Arctic villages over the next 40 years? This question motivated a collaboration of 23 researchers and four Arctic communities (Old Crow, Yukon Territory, Canada; Aklavik, Northwest Territories, Canada; Fort McPherson, Northwest Territories, Canada; and Arctic Village, Alaska, USA) in or near the range of the Porcupine Caribou Herd. We drew on existing research and local knowledge to examine potential effects of climate change, petroleum development, tourism, and government spending cutbacks on the sustainability of four Arctic villages. We used data across eight disciplines to develop an Arctic Community Synthesis Model and a Web-based, interactive Possible Futures Model. Results suggested that climate warming will increase vegetation biomass within the herd’s summer range. However, despite forage increasing, the herd was projected as likely to decline with a warming climate because of increased insect harassment in the summer and potentially greater winter snow depths. There was a strong negative correlation between hypothetical, development-induced displacement of cows and calves from utilized calving grounds and calf survival during June. The results suggested that climate warming coupled with petroleum development would cause a decline in caribou harvest by local communities. Because the Synthesis Model inherits uncertainties associated with each component model, sensitivity analysis is required. Scientists and stakeholders agreed that (1) although simulation models are incomplete abstractions of the real world, they helped bring scientific and community knowledge together, and (2) relationships established across disciplines and between scientists and communities were a valuable outcome of the study. Additional project materials, including the Web-based Possible Futures Model, are available at http://www.taiga.net/sustain.     

Functional diversity and community structure of microorganisms in rhizosphere and non-rhizosphere Canadian arctic soils

Functional diversities of microorganisms in arctic soil samples at three incubation temperatures were assessed using sole-carbon-source-utilization (SCSU). Soil samples from four sites were collected from the rhizosphere and non-rhizosphere soils. Microorganisms were extracted from samples and inoculated into ECO-Biolog plates and incubated at 4, 10 and 28 °C. Calculations of Shannon–Weaver diversity and Shannon–Weaver evenness were based on the substrate utilization in the Biolog plates. Shannon–Weaver diversities (H) in rhizosphere samples were significantly greater ( _H = 3.023 ± 0.197; P < 0.005) than in non-rhizosphere samples ( _H = 2.770 ± 0.154). Similarly, the evenness (E) of the inoculated microbial cells exhibited significant differences (P < 0.005) between the rhizosphere and non-rhizosphere soil samples ( _E = 0.880 ± 0.057 for soils with rhizosphere; _E = 0.807 ± 0.044 for non-rhizosphere samples). Higher microbial diversity and evenness were observed in samples incubated at 4 °C than at 28 °C [least significant difference (lsd) = 0.29], and evenness indices were higher in rhizosphere samples than in non-rhizosphere soils incubated at all three temperatures (lsd = 0.02). Principal component analysis (PCA) of the multivariate data set differentiated the soil samples on the relatively gross scale of microbial communities isolated from rhizosphere and non-rhizosphere soils at all three temperatures.     

Diurnal patterns of CO2 and H2O exchange of the Arctic sedges Eriophorum angustifolium and E. vaginatum (Cyperaceae)

Eriophorum vaginatum and E. angustifolium are dominant arctic sedges of the well-drained tussock tundra and the permanently flooded wet-sedge tundra, respectively. We determined diurnal courses of gas exchange and water relations of the two species in their natural habitat and compared their responses to changes in light, air temperature, and humidity. Mean photosynthetic response to light was similar between E. angustifolium and E. vaginatum and carbon gain in both species was light limited during most of the growing season. On sunny and dry days, both species closed stomata in response to high leaf-to-air vapor pressure deficits. Even though E. angustifolium was growing in standing water, it exhibited a tighter control of transpirational water loss and had lower hydraulic conductivity in the soil-root-shoot pathway than E. vaginatum. The different response pattern between the two species is discussed in the context of differences in habitat conditions.     

Microsatellite and mitochondrial DNA assessment of population structure and stocking effects in Arctic charr Salvelinus alpinus (Teleostei: Salmonidae) from central Alpine lakes

Despite geographical isolation and widespread phenotypic polymorphism, previous population genetic studies of Arctic charr, Salvelinus alpinus , have detected low levels of intra- and interpopulation variation. In this study, two approaches were used to test the generality of low genetic diversity among 15 Arctic charr populations from three major drainages of the central Alpine region of Europe. First, a representative subsample of each drainage was screened by PCR–RFLP analysis of mtDNA using 31 restriction enzymes. All individuals but one shared an identical haplotype. In contrast, microsatellite DNA variation revealed high levels of genetic diversity within and among populations. The number of alleles per locus ranged from six to 49, resulting in an overall expected heterozygosity from 0.72 ± 0.09 to 0.87 ± 0.04 depending on the locus. Despite evidence for fish transfers among Alpine charr populations over centuries, genetic diversity was substantially structured, as revealed by hierarchical Φ statistics. Eighteen per cent of total genetic variance was apportioned to substructuring among Rhône, Rhine, and Danube river systems, whereas 19% was due to partitioning among populations within each drainage. Cluster analyses corroborated these results by drainage-specific grouping of nonstocked populations, but also revealed damaging effects of stocking practices in others. However, these results suggest that long-term stocking practices did not generally alter natural genetic partitioning, and stress the importance of considering genetic diversity of Arctic charr in the Alpine region for sound management. The results also refute the general view of Arctic charr being a genetically depauperate species and show the potential usefulness of microsatellite DNAs in addressing evolutionary and conservation issues in this species.     

Dehydration and cold hardiness in the Arctic Collembolan Onychiurus arcticus Tullberg 1876

Specimens of the Arctic Collembolon Onychiurus arcticus were exposed to desiccation at several subzero temperatures over ice and at 0.5 °C over NaCl solutions. The effects of desiccation on water content (WC), body fluid melting point (MP), supercooling point (SCP) and survival were studied at several acclimation temperatures and relative humidities. Exposure to temperatures down to −19.5 °C caused a substantial and increasing dehydration. At the lowest exposure temperature unfrozen individuals lost 91.6% of the WC at full hydration but more than 80% of the individuals survived when rehydrated. Exposure at 0.5 °C to decreasing relative humidities (RH) from 100% to 91.3% caused increasing dehydration and increasing mortality. Survival of equally dehydrated individuals was higher at subzero temperatures than at 0.5 °C. Concurrent with the decline in WC a lowering of the MP was observed. Animals exposed to −3 °C and −6 °C over ice for 31 days had a MP of −3.8 and < −7.5 °C, respectively. Specimens from a laboratory culture had a mean SCP of −6.1 °C, and acclimation at 0 or −3 °C had little effect on SCPs. Exposure at −8.2 °C over ice for 8 days, however, caused the mean SCP to decline to −21.8 °C due to the severe dehydration of these individuals. Dehydration at 0.5 °C in 95.1 and 93.3% RH also caused a decline in SCPs to about −18 °C. Individuals that had been acclimated over ice at −12.4 °C or at lower temperatures apparently did not freeze at all when cooled to −30 °C, probably because all freezeable water had been lost. These results show that O. arcticus will inevitably undergo dehydration when exposed to subzero temperatures in its natural frozen habitat. Consequently, the MP and SCP of the Collembola are substantially lowered and in this way freezing is avoided. The increased cold hardiness by dehydration is similar to the protective dehydration mechanism described in earthworm cocoons and Arctic enchytraeids. Accepted: 5 January 1998