Polar Biology最新文献

Integration and coordination among monitoring programs are needed to better assess the impacts of climate change on Arctic marine ecosystems. The use of common indicators and methods could facilitate this comprehensive understanding. We completed a systematic review of published marine research in the western Canadian Arctic from 1962 to 2021 to identify the commonalities in methods and indicators present in assessments of coastal and offshore ecosystems. Most abundant in our sample were indicators addressing the environmental context, followed by indicators concerning trophic webs and biological organisms, and finally indicators associated with anthropogenic stressors and threats. Ship-based studies located far offshore were by far the most common and focused on indicators that characterized the physical environment and lower trophic levels. Commonalities in data collection methods suggest possibilities for standardization among programs for some parameters. Differences and data gaps highlighted areas for future coordination and the potential to integrate among indicators, especially as some indicators may span coastal to offshore ecosystems whereas individual monitoring programs may not. The results of this review could be used to identify and gather data into broad-spanning datasets. Overall, this systematic review highlights opportunities to link indicators and methods among coastal to offshore programs and will therefore facilitate connectivity and coordination of ecological research and monitoring in the western Canadian Arctic.

A wide variety of nipple locations and configurations exist among pinnipeds. Like all marine mammals, pinnipeds can have supernumerary nipples that form in utero. Supernumerary nipples have been documented in several species of pinnipeds, the only taxonomic group of marine mammals with variation in nipple number. We document multiple observations (n = 4) of female Weddell seals (Leptonychotes weddellii) with supernumerary nipples in Erebus Bay, Antarctica, including a female Weddell seal with four nipples that was observed nursing two pups. Intraspecific variation in the number of supernumerary nipples observed included both one and two supernumerary nipples. The majority of the observed supernumerary nipples were nursed on by pups, but lactation was unable to be confirmed. These are the first documented observations of supernumerary nipples in Weddell seals.

Spotted wolffish (Anarhichas minor) is a poorly understood species which is often captured as part of mixed demersal fisheries across its range. Abundance has declined in many regions and there is a need for greater knowledge on its biology. To improve our understanding of reproduction of A. minor, we investigated inter- and intra- annual differences in fecundity, the influence of condition on fecundity and time scale of ovary development. From 2006 to 2021, 150 females A. minor were sampled in Icelandic waters. Of these females, 73 were also used to estimate spawning time together with an additional 334 females from commercial catch and surveys from 2006 to 2023. Backwards extrapolation of oocyte size indicates that vitellogenesis begins in December and is likely completed after 8–10 months. There was no evidence of either intra- or inter-annual differences in fecundity, indicating that downregulation is minimal and that fecundity of A. minor is stable between years. A positive relationship between oocytes size and fish length was detected, while body condition and hepatosomatic index had only a small influence on fecundity in comparison with weight. There was a negative relationship between length and relative fecundity and the exponent of the fecundity–length relationship was lower than exponent of the weight–length relationship. Therefore, total egg production is likely not proportional to the spawning stock biomass of A. minor, and unusually, total egg production would decrease with increasing proportion of larger fish in the population. The spawning season was estimated to be from middle of August to middle of October with peak of spawning in September.

Abstract

Due to climate change and human activities, Antarctic shag populations are experiencing shifts in their distribution range, habitat, and population size. To assess their health, we collected hematological and biochemical of male and female South Georgia shags (Phalacrocorax georgianus) during breeding on Laurie Island, South Orkney Island, Antarctica. Leukocyte profile, heterophil/lymphocyte ratio, hematocrit, and concentrations of glucose, total proteins, cholesterol, and triglycerides were measured. None of the measured metrics showed signs of clinical pathology or disease. Overall, the parameters measured were consistent with those previously reported for other cormorant species. Males had higher protein and cholesterol concentrations, indicating differences in nutritional status between the sexes during reproduction. This study is the first report on blood parameters of South Georgia shags in Antarctica and may be useful for future meta-analyzes comparing blood parameters of different species and geographic areas.

Abstract

Microbial communities in the active layer play a crucial role in the biogeochemical cycles of Antarctic pristine ecosystems. Here, 16S rRNA gene sequencing was used to investigate bacterial communities in active layer of five different geological sites related to the compositional variation of the geological bedrock, including Neogene volcanic or Cretaceous rocks and or marine sediments areas of distinct elevation. Local variations in the thickness of the active layer (50–80 cm) were observed on the Ulu Peninsula, James Ross Island, and the southwest coast of Vega Island, Antarctica during sampling in 2019. High bacterial diversity was detected in all sampling sites. Significant site effects on bacterial composition with increased Chloroflexota and decreased Flavobacteriaceae were only observed between the highest elevation Johnson Mesa 2 plateau and coastal areas. The overall effect of the depth was reflected by the increased of e.g., Cyanobacteria, Propionibacterium, Staphylococcus in the upper surface and Chloroflexota, Acidobacteriota, Actinomycetota at depths below 30 cm. The huge number of unassigned bacteria indicated a potential source of new bacterial species and their ecological role in this extreme environment. For the first time, we showed that the effect of depth on bacterial composition was more significant than the effect of geological bedrock from these previously unexplored regions.

Abstract

Birds often have to choose their nest site location along a food safety axis, balancing nest predation danger with the food requirements of themselves and their offspring. This is probably most important for precocial species, such as most shorebirds, in which both chicks and parents need access to food resources in the surroundings of the nest, at least during the first days of life of the chicks. In many Arctic ecosystems, shorebird nests are typically prone to predation by both avian and terrestrial predators, especially in lemming-poor years. Among other factors, the strength of the trophic interactions between shorebirds, their prey, and their predators depend on how all of these are distributed across space. During two breeding seasons in northern Taimyr, North-Central Russia, we investigated how the spatial distribution of red knot Calidris canutus and little stint Calidris minuta nests and broods overlaps with the local food landscape and also with the distribution of avian predators and their main prey, lemmings. We found that the two shorebird species use different habitats that vary in arthropod community structure in accordance with the birds’ diet: while little stints selected lower elevations where chironomid midges Chironomidae are more abundant, red knots selected higher elevations where crane flies Tipulidae are more abundant. Furthermore, little stints share low-elevation habitats with lemmings and predators, while red knots inhabit higher elevations averted by both lemmings and avian predators. We found higher nest predation for little stint nests than for red knots nests, especially in a low-lemming year. Our results thus support the idea that food web interactions are driven by landscape and community aspects.

Over the past 40 years, the significance of microzooplankton grazing in oceanic carbon cycling has been highlighted with the help of dilution experiments. The ecologically relevant Western Antarctic Peninsula (WAP) ecosystem in the Southern Ocean (SO), however, has not been well studied. Here we present data from dilution experiments, performed at three stations around the northern tip of the WAP to determine grazing rates of small zooplankton (hetero- and mixotrophic members of the 0.2–200 µm size fraction, SZP) on auto- and heterotrophic members of the < 200 µm plankton community as well as their gross growth. While variable impacts of SZP grazing on carbon cycling were measured, particulate organic carbon, not the traditionally used parameter chlorophyll a, provided the best interpretable results. Our results suggested that heterotrophic picoplankton played a significant role in the carbon turnover at all stations. Finally, a comparison of two stations with diverging characteristics highlights that SZP grazing eliminated 56–119% of gross particulate organic carbon production from the particulate fraction. Thus, SZP grazing eliminated 20–50 times more carbon from the particulate fraction compared to what was exported to depth, therefore significantly affecting the efficiency of the biological carbon pump at these SO sites.

Southern Rockhopper Penguins Eudyptes chrysocome chrysocome exhibit marked intra-clutch egg size dimorphism and engage in obligate brood reduction of the first and smaller laid egg, with the rearing of the two nestlings occurring only on rare occasions. Studying the sex ratio of hatchlings within a brood in this species, under this breeding strategy context, is essential to understanding population dynamics. The objectives of this study were to analyze egg size dimorphism within the broods, determine the offspring sex ratio, and investigate if the hatchling sex ratio was determined by hatching order and egg volume to discuss potential biases in the context of brood reduction. We molecularly assessed hatchlings’ sex ratio according to the hatching order at Isla Pingüino, Argentina (3 years, n = 68 broods). Sex ratio was not different from the expected 50:50 proportion in all the studied years. In this sense, we found a balanced sex ratio in the first hatchlings, typically the survivors of the brood reduction process. Although not significant, we found a bias toward females in the second hatchlings. Assuming less energy is required to raise a female compared to a male, because of its smaller size; this strategy might enhance the chances of raising two nestlings if conditions are optimal. Southern Rockhopper Penguins at Isla Pingüino appear to exhibit a strategic sex allocation evident in the second but not in the first hatchlings, which might be consistent with its out-of-the-norm exponential growth population.

Blue mussels Mytilus have returned to the high Arctic region of Svalbard in the beginning of twenty-first century after being absent for almost a 1000 years. Not only M. edulis had arrived in Svalbard, but also a complex of sympatric species including M. edulis, M. galloprovincialis, M. trossulus, and some of their hybrids, which may have a wide range of origins from both sides of the North Atlantic. Mussels were first found in the sublittoral at the entrance to Isfjorden, west coast of Spitsbergen island, and are spreading in other areas, and recently were also found in the intertidal zone. Here, we report viable larvae that were recovered from within the mantle cavity of mussels from the lower intertidal shore collected in late July 2019 and 2021 in Trygghamna, Isfjorden. The identity of larval and adult mussels was confirmed by sequencing of barcode region. Larvae ranged in size from 178 to 376 µm, from mussels 21 to 57 mm in shell length, and estimated to range over 3 to 12 years. It remains unclear whether the larval retention within the mantle cavity results from an intake of near shore concentrations and whether this may lead to larviphagy.

Antarctica is considered one of the most inhospitable places to life due to its low temperatures and lack of liquid water. However, meiofauna taxa such as tardigrades not only thrive, but also show remarkable biodiversity in this habitat. Tardigrades are a phylum of small animals (less than 1 mm in length) mainly known for their ability to withstand freezing and desiccation, which are common stressors in Antarctica. The tardigrade genus Mesobiotus is widely distributed and abundant in Antarctica, particularly in the Antarctic Peninsula, where it is been hypothesized it was present even before the continent froze. Different Mesobiotus species have been recorded from the Antarctic Peninsula, but most are based on DNA data and lack assignment to described species. We used integrative taxonomy methods (DNA and morphology combined) on a novel population of Mesobiotus aradasi from Antarctic Peninsula. The latter allowed us to link previous molecular and morphological records of this species and to build a comprehensive map of its distribution. We show that this species is present across almost all the Antarctic Peninsula, whereas there are no records of it for any other Antarctica region. This study highlights the importance of integrating molecular and morphological methodologies and their complementarity when working with biodiversity and distribution data. The M. aradasi distribution highlights its endemicity in the Antarctic Peninsula and calls for attention to possible future threats to this species.