Ringed Seals Research Articles

SEASONAL VARIATION OF BLOOD ANALYTES ASSOCIATED WITH SKIN HEALTH IN ALASKAN ICE SEALS.

Recent unusual mortality events involving skin pathology in bearded (Erignathus barbatus), ringed (Pusa hispida), and spotted seals (Phoca largha) in Alaska highlight the potential sensitivity of ice-associated species to the complex effects of climate change. The regulation of thyroid hormones, cortisol, and vitamin A have been shown to play essential roles in skin health and seasonal molt in some pinnipeds. Unfortunately, the lack of available reference data for healthy Alaskan ice seals has prevented the adequate evaluation of these factors in cases associated with mortality events. To improve understanding of blood analytes that may serve as useful markers of skin health, we compiled diagnostic information for individuals in long-term managed care following short-term rehabilitation. Thyroid hormones (TT4, TT3, and FT4d), cortisol, and vitamin A levels are reported for four ringed seals, four spotted seals, and three bearded seals at the Alaska SeaLife Center in Seward, Alaska, with serial samples obtained when possible and referenced to time of year. For ringed and spotted seals, the thyroid hormones and vitamin A showed a strong seasonal pattern with peak values obtained during the annual molt in spring, whereas cortisol values did not vary predictably between molting and non-molting periods. Trends were similar for individuals across both sex and species. Bearded seals had fewer available data for younger individuals only, but observed analyte values are provided for this understudied species. Collectively, these measurements can be used to support veterinary management of ice seals under human care and to provide initial baselines for skin health monitoring in wild populations and in stranded individuals with known skin lesions or pathology.

Predesign of a Radial Inflow Turbine That Uses Supercritical Methane for a Mid-Scale Thruster for Upper Stage Application

The worldwide concern regarding the harmful effects of old polluting and toxic propellants has led to increased interest in new, green propellants and higher efficiency thrusters. This fact requires that a new generation of turbopumps, fit for these propellants, is developed. This paper focuses on the design of a radial inflow turbine, which was developed to power a single-shaft turbopump system for a 30 kN upper stage expander cycle thruster engine. The objective was to create a high-efficiency, compact, cheap-to-manufacture, 3D-printable turbine suitable to simultaneously power the methane and Oxygen pumps that feed the thruster. The total power consumed by the pumps for which this turbine was designed is 152 kW. The solution proposed in this paper includes measures such as elimination of the bladed diffuser, which was carried out to reduce the weight and the overall dimensions of the turbine. Comparing it with an axial turbine with the same power output, it has lower overall dimensions because it does not require a direction change at the inlet to the turbine bladed components, it does not require a stator to work, and its casing has a conical shape and is not cylindrical like the axial construction one. The proposed design has been analysed by CFD, which revealed that it can power the pumps. Analysis performed in off-design conditions indicated that the turbine has the best efficiency if the rotation speed and mass flow are varied at the same time. A breadboard model of the turbopump for which the turbine in this paper has been designed has been built using plastic and tested at pressures up to 6 bars using compressed air. The results indicate that above 1.5 bars of inlet pressure the turbine can overcome the internal resistances of the components and the rotor starts to spin. No indication of imbalance of the rotor was observed at maximum test pressure. Two configurations of the seals between the turbine and the adjacent pump have been tested, indicating that labyrinth seals must be doubled by floating ring seals.

Mapping of Ligula plerocercoids in the freshwater bream Abramis brama in Lake Syamozero and some other lakes of Northwestern Russia

The tapeworm Ligula intestinalis (Linnaeus, 1758) is a broadly distributed parasite with high epidemiological significance. Its first intermediate hosts are crustaceans, its second intermediate hosts are fish, while the definitive hosts are various fish-eating birds and, as recently shown, ringed seals. The stages of Ligula intestinalis in fish are called plerocercoids. In this study we obtained new data on the occurrence of plerocercoids of L. intestinalis in freshwater bream Abramis brama in six lakes in Karelia (Northwestern Russia). Infection of freshwater bream with L. intestinalis in Lakes Onego, Ladoga, Svyatozero and Konchezero was found for the first time. In Lake Syamozero, where long-term parasitological monitoring has been conducted, infection indices of bream with L. intestinalis were similar to those recorded in 1975. Using two mitochondrial genes (cytb and COI), we examined the genetic structure of L. intestinalis from different localities. Phylogenetic analysis showed that all specimens of of L. intestinalis examined in our study belonged to “Lineage A” identified by Nazarizadeh et al. (2023). We found 40 haplotypes of concatenated cox1+ cytb in freshwater bream from different water bodies in Northwestern Russia and Europe. Plerocercoids from Karelian lakes were represented by 22 haplotypes, of which 21 were unique. Our molecular analysis of L. intestinalis from freshwater bream in European part of the Palearctic shows that this parasite lineage is genetically diverse and rapidly expanding.

Dynamic Performance Analysis of Gas Film Floating Ring Seals Based on the Reynolds–Bernoulli Small-Perturbation Model

Gas film floating ring seals are extensively utilized in aircraft engines, and precise analysis of gas film performance is crucial for ensuring reliable seal design. For this reason, this paper proposes the Reynolds–Bernoulli small-perturbation (RBSP) model to analyze the performance of the gas film based on the conservation of mechanical energy. Through experimental verification and comparison with other analytical models, the results of the RBSP model calculations are both reliable and more broadly applicable. Analyses using the finite element method revealed that the differential pressure effect of Poiseuille flow and the dynamic pressure effect of Couette flow are the primary factors enabling the floating ring to overcome resistance and establish a non-contact seal. Additionally, an appropriate sealing clearance and an increased width of the floating ring could significantly enhance the dynamic performance of the seal. The research findings offer a dependable performance analysis method for designers of gas film floating ring seals.

Linking PVA models into metamodels to explore impacts of declining sea ice on ice-dependent species in the Arctic: the ringed seal, bearded seal, polar bear complex

Arctic ecosystems are especially vulnerable to the impacts of climate change because of the limit to possible northward shifts for species dependent on land or continental shelf and because the rate of warming of the region has been 2-4 x the global average in recent decades. The decline in sea ice in the Arctic has both direct and indirect impacts on the species that live in association with ice, breeding on it, traveling over it, feeding on other ice-dependent species or avoiding competition with subarctic species that cannot exploit resources in ice-covered areas. Herein, we present a metamodel of a top-level predator, the polar bear (Ursus maritimus), and two of its key prey species, ringed seals (Pusa hispida) and bearded seals (Erignathus barbatus), which are important in maintaining current polar bear densities and in turn are strongly influenced by bear predation. We used a metamodel that links Population Viability Analyses of the three species in order to examine how the impacts of declining spring land-fast sea ice on the fjords of Svalbard (Norway) and Frans Josef Land (Russia) can cascade through this predator-prey system. As the ice conditions that allow ringed seals to raise pups in snow-covered lairs on the frozen fjords diminish, or even disappear, ringed seal populations using the land-fast sea ice will collapse due to lack of successful recruitment. Consequently, the polar bear population, which relies heavily on hunting ringed seals in the land-fast sea ice to be able to raise their own offspring is also likely to decline. Our models suggest time-lags of decades, with the polar bear population not entering into decline until the lack of recruitment of ringed seals results in the depletion of breeding age ringed seals – starting in the third decade from the start point of the model and dropping below the initial population size only some decades later. Although lags between climate change and impacts on the ice-associated fauna are expected, the sea ice conditions have already changed dramatically in the northern Barents Sea region, including the Svalbard Archipelago, and the collapse of this Arctic species assemblage might already be underway.

Lack of differences in anatomical structures of the head associated with thermoregulation between Saimaa (Pusa hispida saimensis) and Baltic ringed seals (Pusa hispida botnica)

Lack of differences in anatomical structures of the head associated with thermoregulation between Saimaa (Pusa hispida saimensis) and Baltic ringed seals (Pusa hispida botnica)

Major Histocompatibility Complex Class II Genes Allele Diversity in Landlocked Seals.

The allelic diversity of exon 2 (DQB gene) and exon 3 (DRB gene) of major histocompatibility complex class II was studied for the first time in two species of the landlocked pinnipeds, Baikal (N = 79) and Caspian (N = 32) seals, and these were in compared with the widespread Arctic species, the ringed seal (N = 13). The analysis of the second exon comprising the antigen-binding region revealed high allelic diversity in all three species but the pattern of the diversity was the most specific for the Baikal seal. This species differs from the other two by the smallest number of alleles in the population, yet they have the largest number of alleles per individual and by the maximum similarity of individual genotypes. Presumably, this specificity is a consequence of the spatial and temporal homogeneity of the Lake Baikal environment. Analysis of the third exon encoding the conserved β2-domain showed that the Baikal seal differs by the greatest number of amino acid sequences per individual, while the Caspian seal has the lowest number of variants. A single variant of the β2-domain, the same as in the ringed seal, predominates in the Caspian seal, whereas in the Baikal seal the two other variants predominate. At the same time, three species-specific amino acid sequences were observed among minor variants in the Caspian seal, while only one was found in the Baikal seal. This fact may suggest a longer period of independent evolution in the Caspian seal compared to the Baikal seal.

Seasonal habitat use of ringed seals in the Thule area, northwestern Greenland

Recent rapid environmental changes along the Greenland coast have significantly impacted Arctic marine mammals. The melting of tidewater glaciers influences ocean environments and ecosystems, potentially changing the distribution and behavior of Arctic marine mammals. The ringed seal (Pusa hispida) is a keystone species in the Arctic marine ecosystem. In this study, four ringed seals were equipped with Argos conductivity-temperature-depth (CTD) satellite relay data loggers close to tidewater glaciers in the Thule area of northwestern Greenland to investigate the relationship between their behavior and the marine environment. All seals spent most of their time in the vicinity of tidewater glacier fronts during the open-water period. After that period, the two seals moved out of the glacial fjords due to the formation of land-fast ice and stayed in the North Water Polynya area, where sea ice was relatively thin and sparse during the ice-covered period. Furthermore, CTD data suggest that ringed seals mainly dove to the depths of the water inhabited by the polar cod (Boreogadus saida). These habitat use characteristics, associated with distribution of ice and prey species, could potentially affect the distribution and ecology of this species under future climate change.

Evaluation of cement ring sealing under cyclic loading conditions

Abstract As exploration and development continue to advance, incidents of cement ring seal failures are occurring more frequently. Such failures can directly impact the safe development of oil and gas wells. To effectively assess the sealing performance of cement rings, this paper explores the mechanisms behind sealing failures at both the cementing interface and the cement ring body under cyclic loading conditions. It also examines the sealing capabilities of the initial cementing interface and the cement ring body by developing a finite element model of the ‘casing-cement ring-facility’ and incorporating the Cohesive cementing unit. The findings indicate that the pressure within the casing is extremely high, and the cement ring is tightly sealed. The results indicate that fluctuations in pressure within the casing can compromise the sealing effectiveness of the cement ring, leading to micro-annular gaps at either the first or second cementing interface. Additionally, damage to the Cohesive unit initiates during the first loading cycle, with increased displacement of the initial cement surface correlating to higher pressure cycles.

Structural Optimization Analysis of Combined Sealing Ring

Abstract In this paper, the effect of the contact forces of the combined sealing ring by the pre-compressibility of the O-ring seal and the working pressure is studied. The influence of the structural parameters (width, thickness and chamfer) of the friction ring on the contact forces of the combined sealing ring is analyzed. The results show that, in the combined seal, it is not that the higher the pre-compressibility, the higher the sealing efficiency. Under certain working conditions, the chamfer of the friction ring increases, the contact forces of the friction ring decreases; the thickness of the friction ring increases, the contact forces of the friction ring is almost unchanged; The contact force increases with the increase of the width of the friction ring. Under the condition of a given medium pressure of 25 MPa and a compressibility of 22.5%, the optimal values of friction rings L, R, and H and three contact forces and contact forces F under the corresponding conditions are calculated by the optimization algorithm.

Seroprevalence of Erysipelothrix rhusiopathiae in Beaufort Sea Polar Bears (Ursus maritimus) is Linked to Ringed Seal (Pusa hispida) Demographics.

Polar bear (Ursus maritimus) life history is intimately associated with the distribution of sea ice and their prey in Arctic ecosystems. These ecosystems are changing in response to climate warming, resulting in the increased prevalence of pathogens in polar bears. Erysipelothrix rhusiopathiae has a long history of infection in domestic species and more recently in wildlife in the Canadian Arctic. As a result of increasing reports of E. rhusiopathiae causing morbidity and mortality in Arctic terrestrial mammals, we tested the seroprevalence of E. rhusiopathiae in Beaufort Sea polar bears sampled in 1985-87, 1992, 1994, and 2003-11. Our sample of 180 polar bears (117 females, 61 males, two unknown) with a median age of 9 yr (range 1-26 yr) had a seropositivity of 27.2% (49/180 individuals). We used binomial logistic regressions to investigate biotic and abiotic factors that may be linked to seropositivity. The resulting top model found that increased predation on adult ringed seals (Pusa [Phoca] hispida) and negative winter Arctic Oscillation Index (AOI) years were associated with a higher probability of seropositivity. Ringed seals may be a reservoir for E. rhusiopathiae via their consumption of infected prey, as the pathogen can persist in marine fish, molluscs, and crustaceans. Negative winter AOIs in our data set reflected high ice volume years, which reduced ringed seal natality, resulting in fewer seal pups available as prey. Our results suggest that exposure to E. rhusiopathiae in Beaufort Sea polar bears is modulated by a predator-prey mechanism.

Exploring novel North Water Polynya ecosystems under climate change

Climate change is rapidly reshaping species distributions in the Arctic, which could profoundly impact ecosystem structure and function. While considerable effort has focused on projecting future species distributions, assessing the impacts of range-shifting species on recipient communities and subsequent disruptions to food webs remains largely unstudied. Here, we address this gap by combining species distribution models and ecosystem models to explore the emergence of novel ecosystems in the North Water Polynya. The North Water Polynya is an open-water area between Greenland and Canada, surrounded by sea ice and one of the world’s most productive ocean ecosystems. Using existing literature and projections from species distribution models of four marine species, we develop six plausible future ecosystem scenarios for the North Water Polynya. These scenarios include changing biomass of primary producers, changing biomass and size structure of copepods, shifting abundances of forage fish species, and the establishment of killer whales. We find that the biomass of higher trophic levels show pronounced decreases in response to the decrease in pelagic primary producers, with polar bear biomass halving compared to present conditions. Changes in the copepod size structure has the largest impact on the entire ecosystem compared to the other novel ecosystem scenarios, suggesting a strong reliance of higher trophic levels on large, lipid-rich copepods. We further show that increasing capelin with a simultaneous decrease in Arctic cod biomass causes large decreases in the biomass of marine mammals such as polar bear, beluga and ringed seal. Finally, we show the establishment of killer whales as a key novel predator could have cascading top-down effects on the North Water Polynya ecosystem. The framework presented here provides an approach for exploring the emergence of novel ecosystems and highlights how climate change could disrupt a high Arctic ecosystem.

Are narwhals critical for the meat supply in East Greenland ?

In East Greenland, the recommendations for the closure of the narwhal (Monodon monoceros) hunt coincide with a pressing demand to continue hunting for meat to supply local communities. By analysing catch statistics and estimating average meat yields, the available meat from marine mammals, polar bears (Ursus maritimus), and muskox (Ovibos moschatus) in East Greenland can be assessed. On average, there was approximately 426 tonnes of meat available per year during this period. However, this quantity declined due to reduced catches of hooded seals (Cystophora cristata) and ringed seals (Phoca hispida) after 2007. This decline was somewhat offset by the inclusion of new species in the hunt, such as dolphins (Delphinidae), killer whales (Orcinus orca), and pilot whales (Globicephala melas). The average annual meat availability per inhabitant decreased from 150 kg before 2008 to 94 kg afterward. Narwhals consistently contributed approximately 5–6% of the total annual meat supply in Greenland over the observed period, which suggests that narwhal meat is not critical for the overall food supply. The inclusion of the need for meat in discussions surrounding sustainable harvest levels has been a point of controversy, particularly in cases where an urgent halt to hunting is needed.

Seal of approval: Public preferences for the conservation of endangered Saimaa ringed seal

In species conservation, various options for conservation measures typically exist, yet their implementation may lead to conflicts among different population groups. Heterogenous preferences toward conservation measures often stem from the utilization of natural resources, whether for livelihood or recreational purposes. This study, focusing on the Saimaa ringed seal, a symbol of nature conservation in Finland, examines both population size and conservation measures. We distinguish the stated preferences between recreational visitors to Lake Saimaa, fishers at the lake, and individuals residing in other parts of Finland without direct use of the lake. To measure preferences, we utilize a choice experiment that incorporates both population size and the most promising conservation measures as attributes. The findings reveal significant variations in willingness-to-pay estimates between visitors and non-visitors, as well as between fishers and non-fishers. Interestingly, all population groups expressed a preference for a moderate increase in the seal population and a small extension of conservation measures, rather than opting for a substantial extension of measures. This insight emphasizes the importance of considering diverse stakeholder perspectives when designing and implementing species conservation strategies.

A comparative analysis of life-history features and adaptive strategies of Arctic and subarctic seal species—who will win the climate change challenge?

Understanding and predicting species range shifts is crucial for conservation amid global warming. This study analyzes life-history traits of four seal species (ringed ( Pusa hispida (Schreber, 1775)), bearded ( Erignathus barbatus (Erxleben, 1777)), harp ( Pagophilus groenlandicus (Erxleben, 1777)), and harbour ( Phoca vitulina Linnaeus, 1758) seals) in the Canadian Arctic using data from Inuit subsistence harvests. Bearded seals are largest, followed by harp seals, harbour seals, and ringed seals. Seasonal blubber depth patterns show minimal variation in bearded seals, whereas harbour and ringed seals accumulate fat in open-water seasons and use it during ice-covered seasons. Endemic Arctic seals (ringed and bearded) exhibit greater longevity and determinate body growth, reaching maximum size by 5 years, while harbour and harp seals grow indeterminately, physically maturing around 10–15 years. Age of maturation varies, with ringed and harbour seals being more sensitive to environmental fluctuations. Most bearded seals reproduce successfully each year, while ringed seals exhibit more variability in their annual reproductive success. Analysis of isoprenoid lipids in liver tissue indicates that ringed and bearded seals rely on ice-algal production, whereas harp and harbour seals depend on open-water phytoplankton production. Bearded seals appear more specialized and potentially face less competition, while harp seals may adapt better to changing habitats. Despite expected range shifts to higher latitudes, all species exhibit trade-offs, complicating predictions for the evolving Arctic environment.

Analysis of friction vibration characteristics of the end face of a T-slot sealing ring under thermal deformation

Aiming at the friction vibration problem caused by dry friction contact during the start-stop process of a dry gas sealing device, this paper takes the end face of a T-slot dry gas sealing ring as the research object and establishes a numerical calculation model of the end face of the T-slot sealing ring. The thermal coupling method is used to obtain the thermal deformation law of the seal ring end face. The transient dynamics analysis method was applied to study the frequency and vibration mode of the friction vibration instability of the seal ring end face under thermal deformation. A vibration test bench was set up for the friction ring, and the friction vibration signals of the test pieces were collected, and the characteristic frequencies were extracted. The results show that: After thermal deformation, the end face of the sealing ring changes from a parallel surface to an inward converging surface, and the friction system of the sealing ring will become unstable. When considering the influence of thermal deformation, there are more unstable frequencies and lower frequency values that are most prone to frictional vibration. As the thermal deformation of the sealing ring increases, the frictional vibration becomes greater. In areas where the characteristic frequency values of frictional vibration are concentrated during thermal deformation, the occurrence rate of frictional vibration noise is higher.

Species assignment from seal diet samples using shape analyses in a machine learning framework

Abstract The identification and quantification of prey ingested is a limiting factor in trophic ecology studies and is fundamental for assessing the impact of a predator on prey populations. Vendace (Coregonus albula) and whitefish (C. lavaretus) are two congeneric species, which are commonly preyed on by Baltic ringed seals (Pusa hispida). The otoliths of these two species are, however, very similar and distinguishing between them in the seal diet using visual inspection has so far been challenging. Here, otolith shape outline analyses were used in combination with machine learning techniques to discriminate between eroded vendace and whitefish otoliths from ringed seal diet samples. An experiment of in vitro digestion of the otoliths was performed to train a machine learning model. Our model is able to self-assign known digested otoliths back to their species of origin with >90% accuracy. Furthermore, 89% (N = 690) of the otoliths collected from digestive tract samples could be successfully assigned to species level, i.e. vendace or whitefish. This method is readily applicable for improved understanding of ringed seal feeding habits and predator–prey interactions, as well as large-scale applications to generate seal-predation matrix inputs for stock assessments of vendace and whitefish. Further development of the machine learning techniques to discriminate between prey species in seal and other piscivorous diets is strongly encouraged.

Harvest sustainability assessments need rethinking under climate change: A ringed seal case study from Svalbard, Norway

AbstractThroughout the Arctic, ice‐affiliated marine mammals constitute local subsistence resources but detrimental effects of declines in their sea ice habitats create a need for harvest sustainability assessments in light of climate change. At the same time, empirical data required for thorough population analysis of these species are often sparse at best, as illustrated by the focal species in this study, ringed seals in Svalbard: the last population survey took place two decades ago (2002–2003), demographic data are limited to age, sex, and reproductive status of a small subset of shot individuals, and harvest reporting is patchy and incomplete. Data sparsity is one of the main reasons why potential biological removal (PBR) became a commonly used tool for assessing sustainability of marine mammal harvests. Herein, we calculated PBR for Svalbard ringed seals using both recommended default parameters and population‐specific parameters obtained from an integrated population model (IPM). PBR estimates were highly uncertain, suggesting the number of sustainably harvestable individuals could lie anywhere between 0 and 91, with a substantial chance of any harvest being unsustainable under current environmental conditions and trends. Subsequent population viability analyses (PVAs) further confirmed that the current harvest was likely unsustainable, even in a scenario in which sea ice conditions would not deteriorate (and therefore lower pup survival) further. However, uncertainty in population projections was high, and forecasts thus not ideal for formulating management advice. Better forecasts will require more frequent population surveys and obtaining more knowledge regarding the links between vital rates and environmental conditions, both of which may be facilitated by the adoption of novel technology (e.g., drone monitoring, genetic studies). The modeling framework created in this study can be readily updated with new data as they become available, and can serve as a tool for adaptive management of this and other marine mammal populations.

Marine Hunting of Pinnipeds (Pinnipedia) on the Coats of the White Sea in the Eneolithic

This is a study of initial stages of adaptation of the ancient human population to the use of aquatic food supplies in the White Sea. The main aim of archaeozoological analysis was to study the processes of formation of faunal remains and strategies on seals hunting during the Eneolithic in the White Sea region. The archaeological source material consists of faunal remains recovered from two Eneolithic sites of the Kandalaksha bay. The results of archaeozoological studies confirmed the high importance of the ringed seal and harp seal in the hunting prey of the inhabitants of the studied sites. Eneolithic hunting strategies of the White Sea region were closely related to the behavioral and ecological patterns of seals. The seal hunt was based on a model of exploiting a massive seasonal resource. Hunting pressure on the ringed seal and harp seal populations was significant. Seals were the main suppliers of meat, skin and fat for the inhabitants of the Eneolithic sites of this part of Fennoscandia. The studies of the lithic tools from the Early Metal period settlements from Kandalaksha bay provide additional evidences of a specialized marine hunting. Apparently, in the Eneolithic (IV – III millennia calBC), the economic and cultural type of sea hunters was formed on the shores of the White Sea.

Multi-Physical Field, Coupled, Mixed Lubrication Analysis of Hydraulic Reciprocating Vacuum Lip Seal

Engineering practice has demonstrated that seal failure can result in severe leakage and wear, reducing the efficiency of hydraulic systems and even leading to major safety risks. Currently, analyses of the thermal aspect of seal interfaces are relatively limited, with most studies focusing on mechanical analysis. However, in actual applications, temperature has a significant impact on sealing performance. In this paper, nonlinear elastomechanics, viscous fluid mechanics, micro-contact mechanics, micro-deformation theory, and thermodynamics are coupled to establish a mixed lubrication model considering the thermal effect. The reliability of the mixed lubrication model is verified through experiments, and the temperature distribution of the oil film in the sealing area and the temperature distribution of the seal ring are simulated. Finally, the effects of the reciprocating speed, root mean square roughness, fluid medium pressure, and seal pre-compression on seal friction force and leakage are investigated. The results show that the heat generated in the sealing area accumulates at the bottom of the V-ring. Under the same conditions, compared with the instroke, the temperature-rise area of the outstroke is biased to the left and the increase in temperature is greater. In addition, the piston rod speed and the preliminary compression of the seal ring have a greater impact on the overall seal friction force and leakage. Under a lower seal pre-compression, the RMS roughness has a great influence on the leakage and friction in the outstroke, while the impact of the internal stroke is limited.