<Emphasis Type="Italic">Stephanthus antarcticus,</Emphasis> a new genus and species of sea anemone (Actiniaria,Haloclavidae) from the South Shetland Islands,Antarctica

Stephanthus antarcticus gen. nov. et sp. nov. is described and illustrated from six specimens collected in the Antarctic Peninsula on the Polarstern cruises ANT XV/3 and ANT XIX/3. The new genus is characterised by the absence of sphincter and basilar musculature, the presence of a single strong siphonoglyph with a basal enlargement, distinct parietobasilar musculature, tentacles without acrospheres, two cycles of six pairs of mesenteries (only one of them perfect), and a deep fosse with parapet; another remarkable feature is the absence of microbasic p-mastigophores. The new genus shows characteristics of three families of soft-bottom-dwelling sea anemones, namely Haloclavidae Verrill, 1899, Halcampoididae Appellöf, 1896, and Andresiidae Stephenson, 1922. The generic characters of Stephanthus gen. nov. are discussed and it is tentatively placed in the family Haloclavidae.     

Population genetic structure and gene flow patterns between populations of the Antarctic icefish Chionodraco rastrospinosus

Aim A lack of genetic structure is predicted for Antarctic fish due to the duration of pelagic larval stages and the strength of the currents in the Southern Ocean, particularly the Antarctic Circumpolar Current. In this study we explored the population structure of the ocellated icefish, Chionodraco rastrospinosus, by means of analysing a total of 394 individuals collected at four geographical areas off the Antarctic Peninsula in the period 1996–2006. Location Elephant Island, southern South Shetlands, Joinville Island and South Orkneys in the Southern Ocean. Methods The spatio‐temporal genetic structure of Chionodraco rastrospinosus was explored using seven microsatellite loci. Existence and direction of gene flow across sampling locations were investigated using the isolation‐by‐migration procedure. Results Microsatellite data showed a lack of genetic structuring in the area studied, with no differences found at both the geographical or temporal level, and an eastward unidirectional gene flow among sites. This suggested a lack of genetic barriers for this species, attributable to larval dispersal following the Antarctic Circumpolar Current, which fits well with the predicted pattern for Antarctic fish. Re‐examination of genetic data of the closely related icefish Chaenocephalus aceratus, with similar larval duration but displaying genetically structured populations, indicated a weak but significant bidirectional gene flow. Main conclusions Our results point to a relationship that is more complex than expected between potential for dispersal and realized gene flow in the marine environment. In addition to ocean circulation and larval dispersal, other major life‐history traits might be driving connectivity, particularly larval retention.     

2018年夏秋季南设得兰群岛周边水域南极磷虾集群类型及其影响因素

南极磷虾是一种典型的集群性海洋生物,其集群特征为行为生态学研究领域的重要内容之一。南极磷虾在南设得兰群岛周围高度密集分布,然而磷虾集群形状和大小的机制解释仍存在较大的争议。基于南设得兰群岛周边水域收集的Simrad EK80声学数据,本研究利用Echoview V6.16软件,对声学数据进行了分析,并对磷虾集群特征进行了划分。通过主坐标分析(PCoA)检验了环境因素(表温和海况)以及时空因素对各类型磷虾集群产生的影响。结果表明:海况对磷虾集群影响较大,光照强度次之;块状小型集群的时空分布较广,夜间与白天均占有较高比例(>30%);小型集群更易出现在白天,而大型集群则更多出现在深夜; 2月,磷虾集群与海况及纬度显著相关; 3月,集群与时段显著相关; 4月,集群与时段及海况显著相关。     

Amphipod crustaceans as an important component of zoobenthos of the shallow Antarctic sublittoral

Benthic quantitative samples were taken in 1988 in the soft bottom sublittoral of Admiralty Bay (King George Island, South Shetlands) using a Tvärminne-type bottom sampler and SCUBA-diving technique at 7 successive stations situated at depths from 4 to 30 m.Dominant animal groups in terms of abundance were Amphipoda, Polychaeta and Bivalvia, whereas in terms of biomass Echinoidea were also dominant. Amphipod crustaceans clearly dominated the zoobenthos at depths from 10 to 25 m (the numerical share surpaising 60%) with maximal abundance of abt. 17 000 ind m^–2; in terms of biomass at specific depths amphipods occupied the 1st, 2nd or 3rd place with maximal biomass of abt. 100 g m^–2 where the maximal total biomass of zoobenthos reached 260 g m^–2 (10 m).Amphipoda were the most diversified group with some 35 taxa belonging to 14 families. Most species belonged to Eusiridae s.l. and Lysianassidae s.l. Dominant forms were Pontogeneiella brevicornis, Prostebbingia gracilis, Schraderia gracilis, Hippomedon kergueleni, Orchomenella cf. ultima, Cardenio paurodactylus and Paraphoxus rotundifrons.     

Changing wind patterns linked to unusually high Dinophysis blooms around the Shetland Islands,Scotland

During the summer of 2013, 70 people received Diarrhetic Shellfish Poisoning following consumption of mussels harvested in the Shetland Islands, Scotland. At this time, large numbers of the biotoxin-producing phytoplankton genus Dinophysis was observed around the Shetland Islands. Analysis indicated this increase was not due to in situ growth but coincided with a change in the prevalent wind direction. A previous large bloom of Dinophysis during 2006 also coincided with a similar change in the prevalent wind patterns. Wind direction and speed in the North East Atlantic and the North Sea is strongly influenced by the North Atlantic oscillation (NAO) with a positive relationship between it and wind direction. It has been noted that a positive trend in the NAO is linked to climate change and predictions suggest there will be an increasingly westward component to prevalent wind directions in the North Sea which could lead to an increase in the occurrence of these harmful algal blooms. Analysis of wind patterns therefore offers a potential method of early warning of future bio-toxicity events.     

基于地理加权模型的南设得兰群岛北部南极磷虾渔场空间分布影响分析

结合南极磷虾渔业科学观察员收集的渔业数据和海洋环境数据,本研究利用地理加权回归模型(GWR),分析了具有空间属性的虾群深度和离岸距离两个因子,以及海水表温对南设得兰群岛北侧水域南极磷虾渔场空间分布的影响.结果表明:各年南极磷虾渔业单位捕捞努力量渔获量(CPUE)在空间上的分布无显著的集聚性;2010和2013年,3个因子之间存在空间自相关性(正相关),而2012和2016年则无自相关性.GWR模型结果显示,3个因子对CPUE的空间分布具有不同程度的影响,影响程度大小依次为虾群深度>离岸距离>温度.拟合结果发现,南设得兰群岛东、西两侧水域中表温对CPUE空间分布的影响与其他两个因子具有相反的趋势.虾群深度和离岸距离对CPUE的空间效应主要表现为负相关,但存在着年际和区域性差异.本研究结果可为南极磷虾渔场形成机制研究提供方法上的参考.     

Population ecology and juvenile density hotspots of thornback ray (Raja clavata) around the Shetland Islands,Scotland

Elasmobranchs are facing global decline, and so there is a pressing need for research into their populations to inform effective conservation and management strategies. Little information exists on the population ecology of skate species around the British Isles, presenting an important knowledge gap that this study aimed to reduce. The population ecology of thornback ray (Raja clavata) around the Shetland Islands, Scotland, was investigated in two habitats: inshore (50–150 m deep) and shallow coastal (20–50 m deep), from 2011 to 2022, and 2017 to 2022, respectively. Using trawl survey data from the annual Shetland Inshore Fish Survey, the size composition of R. clavata catches was compared between shallow and inshore habitats across 157 trawl sets, and 885 individuals, over the years 2017–2022. Catch per unit effort (CPUE) of R. clavata was significantly higher in shallow than that in inshore areas (ANOVA, F = 72.52, df = 1, 5, p < 0.001). Size composition also significantly differed between the two habitats (analysis of similarities, R = 0.96, p = 0.002), with R. clavata being smaller in shallow areas and juveniles (<60 cm) occurring more frequently. Spatial distribution maps confirmed density hotspots of juveniles in shallow habitats, with repeated use of certain locations consistent over time. The results of this study provide the first evidence for R. clavata using shallow areas for potential nurseries in Shetland, which can inform the IUCN's Important Shark and Ray Area process. Furthermore, this study provides important new population ecology information for R. clavata around Shetland, which may have important conservation implications and be valuable for informing species and fisheries stock assessments in this region.     

Isolation and characterization of microsatellite loci in the icefish Chionodraco rastrospinosus (Perciformes,Notothenioidea, Channichthyidae)

We characterized eight polymorphic microsatellites in the icefish Chionodraco rastrospinosus (Perciformes, Notothenioidea, Channichthyidae). Microsatellites were isolated from a partial genomic library enriched for an AC motif. Chionodraco rastrospinosus is an endemic species inhabiting southern ocean waters surrounding the Antarctic Peninsula, the South Shetland Islands, and the South Orkney Islands. An excess of homozygotes was observed in seven out of the eight investigated loci; however, presence of null alleles was detected only for three of them suggesting that other factors may act in reducing heterozygosity. These molecular markers will be useful to investigate icefish genetic structure, possibly providing insights on its effective population size and demographic history.     

Demersal fish parasite fauna around the South Shetland Islands: high species richness and low host specificity in deep Antarctic waters

A total of nine Antarctic fish species belonging to five families were examined for their endohelminth parasite fauna. The fishes Parachaenichthys charcoti (Bathydraconidae), Chaenocephalus aceratus (Channichtyidae), Paradiplospinus gracilis (Gempylidae), Muraenolepis microps (Muraenolepididae), Gobionotothen gibberifrons, Lepidonotothen larseni, L. nudifrons, L. squamifrons, and Trematomus eulepidopus (Nototheniidae) were caught between 80 and 608 m trawling depth off the Antarctic Peninsula (Elephant Island, King George Island) in 1996. Nineteen different parasites species comprising five Digenea, two Cestoda, four Nematoda, and eight Acanthocephala were found. Pseudophyllidean cestodes, the nematodes Contracaecum radiatum and C. osculatum as well as the acanthocephalan Corynosoma bullosum were the most common, infesting eight of the fish species studied with prevalences reaching 100%. Pseudoterranova decipiens s.l. was the only parasite that was isolated from all studied fish species; however, at a lower intensity. The observed parasite host specificity was low, and the species richness in a single fish ranged from one to eleven in a C. aceratus. This icefish and the moray cod M. microps were the most heavily infested fish, harbouring many adult and larval parasitic stages. The benthodemersal P. gracilis had only two larval parasite species, while the nototheniids had very similar parasite communities, harbouring a total of 8–14 species. Larval mammalian parasites were found to utilize fish, especially the nototheniids and channichthyids, as a common transmission route into their final hosts. The fish parasites parallel explored different benthic host systems to reach the most suitable host. In contrast to the coast and continental shelf, the meso/bathypelagiac zone appears to be species poor and is inhabited by few larval forms. The fish parasite fauna off the South Shetland Islands can be characterized by generalistic parasites that distribute within Antarctic waters according to the feeding ecology and depth range of their teleost hosts, not only horizontally but also extending vertically into the deep sea.     

Macrobenthic mollusc assemblages and diversity in the West Antarctica from the South Shetland Islands to the Bellingshausen Sea

Although frequent studies have been made on the benthos assemblages living in the Southern Ocean, few studies have dealt with molluscan assemblages and ecology. During the research programmes BENTART carried out in austral summers of 2003 and 2006 in a study area including Low Island, West Antarctic Peninsula, Bellingshausen Sea and Peter I Island, 45 stations were sampled using quantitative box-corer, Agassiz trawl, epibenthic sledge and rock dredge, at depths of 53–3,304 m. These data were used to search and analyse the malacological assemblages. A total of 2,889 living specimens of molluscs belonging to 139 species of shelled Gastropoda, Bivalvia and Scaphopoda were recoded. Gastropods were the best-represented in species richness, but the bivalves accounted the major abundance and Cyamiocardium denticulatum (460 individuals) was the most abundant species. Species richness varied from 1 to 37 species and diversity showed great variations at different stations. Four groups of stations of low similarities and some differences in faunistic composition were observed: one that gathers the Antarctic Peninsula and Peter I Island, one that also includes the Low Island, and two composed by stations of Bellingshausen Sea.     

Aspects of the foraging behaviour of the Antarctic Tern Sterna vittata gaini at Harmony Point, South Shetland Islands

During January and February of 2002 and 2003, we studied the diet of the Antarctic Tern Sterna vittata gaini at two colonies in Nelson Island, South Shetland Islands, by identifying the prey fed to chicks by breeders. The fish Notothenia coriiceps was the main prey in both seasons, followed by the myctophid Electrona antarctica, Antarctic krill Euphausia superba and gammarid amphipods. The contribution of fish to the diet increased as chicks grew older. Fish and amphipods were brought to chicks during the day, whereas adults brought Antarctic krill at sunrise and sunset. Both the duration of the feeding trips and the number of trips per foraging bout varied according to the type of prey caught. Preliminary information suggests that, among other causes, the foraging strategy is strongly influenced by the predation pressure of skuas on chicks. Results are compared with the only two previous study on the diet of the Antarctic Tern at the South Shetland Islands.     

Summer macroalgal biomass in Potter Cove,South Shetland Islands,Antarctica: its production and flux to the ecosystem

Summer macroalgal biomass and production were analyzed at Potter Cove, King George Island, Antarctica and the potential carbon transfer of macroalgal production to the coastal ecosystem of the cove was estimated. A total of 38 algal species were found, with Desmarestia anceps, D. menziesii and Himantothallus grandifolius accounting for almost 80% of the biomass. Biomass data and published growth rates were combined to calculate the production of the five most abundant species. The standing stock for each summer month was estimated as the product of the average biomass and the area of the macroalgal stands. The monthly biomass production was calculated for each species by difference between the expected biomass and the observed biomass at the previous month. The macroalgal production showed a decreasing trend during the summer months. The average standing stock in the whole cove was 792.84 MT and the production was 1,401.33 MT during the summer 1994–1995. The flux of biomass to the ecosystem during the summer period was 1,370.61 MT, which is almost as much as the total summer production. The study demonstrates that macroalgae are one of the main energy sources in Potter Cove, and probably support a large fraction of the secondary production of the benthos.     

The diet of the Weddell seal <Emphasis Type="Italic">Leptonychotes weddellii</Emphasis> at Laurie Island,South Orkney Islands

The diet of the Weddell seal Leptonychotes weddellii at the South Orkney Islands was investigated by the analysis of 44 and 26 faecal samples collected from the beaches of Laurie Island from May 1999 to January 2000 and from October to December 2001, respectively. The diet was diverse and both pelagic and benthic-demersal organisms were represented in the samples. Fish were the most frequent prey of the samples in both seasons, and fish and krill were the most numerous prey items. Octopods predominated by mass in 1999, whereas krill constituted the bulk of the diet in 2001, a fact that was not observed previously. Among fish, Gobionotothen gibberifrons was largely the species that contributed mostly to the diet, whereas pelagic fish could not be identified in the samples. The results are compared with information from other study areas and discussed in relation to the consumption of krill.     

Linking structural variability in long bone diaphyses to habitual behaviors: foragers from the southern African Later Stone Age and the Andaman Islands

The cross-sectional distribution of cortical bone in long bone diaphyses is highly responsive to mechanical loading during life, yet the relationship between systemic and localized influences on skeletal structure remains unclear. This study investigates postcranial robustness throughout the body among adults from two groups of foragers with different patterns and modes of mobility, to determine whether there is evidence for upper vs. lower body localization of skeletal robustness. The samples used for this comparison are from the southern African Later Stone Age (LSA; n = 65, male = 33, female = 28) dating from ca. 10,000 to 2,000 B.P., and 19th century indigenous Andaman Islanders (AI; n = 36, male = 17, female = 16). The LSA were highly mobile foragers who did not exploit offshore marine resources. In contrast, the AI had tightly constrained terrestrial, but significant marine, mobility. Geometric properties of cortical bone distribution in the diaphyses of the clavicle, humerus, femur, tibia, and first metatarsal are compared between the samples, providing a representation of skeletal robustness throughout the body. Multivariate ANOVA shows the AI to have significantly stronger clavicles and humeri, while the LSA femora, tibiae, and first metatarsals are stronger than those of the AI. These patterns, in which upper and lower limbs show biomechanical properties that are consistent with habitual behaviors, suggest localized osteogenic response. Although postcranial robustness appears to be correlated with overall limb function, the results suggest that more proximal elements within the limb may be more responsive to mechanical loading.     

Phytoplankton structure and dynamics in a volcanic lake in Deception Island (South Shetland Islands,Antarctica)

This work constitutes the first floristic and ecological analysis of the phytoplankton community of a volcanic freshwater lake in Deception Island (62°57′S, 60°38′W, South Shetland Islands, Antarctica). The main limnological features and phytoplankton size fractions were analyzed. Samples were taken during the austral summer of 2002 at two opposite sites. According to ANOVA results performed with abiotic variables, no significant differences between sites were found. The phytoplankton community showed low algal species richness, with an important contribution of the tychoplanktonic taxa. In terms of species number, Bacillariophyceae was the dominant class. Autotrophic picoplankton registered the highest densities from the second sampling date onwards. Nanophytoplankton was represented by unidentified chrysophycean organisms, which showed different distribution patterns between sites. The net phytoplankton abundance remained low during the sampling period and was strongly correlated with chlorophyll a concentration. Both nutrient concentrations and chlorophyll a values indicated oligotrophic conditions.     

Macroscopic network properties and short-term dynamic simulations in coastal ecological systems at Fildes Bay (King George Island,Antarctica)

A trophic mass-balanced of the benthic/pelagic system dominated by large brown macroalgae in Fildes Bay (Antarctica) was constructed by integrating biomass, production, food spectrum, and consumption related information. The resulting trophic model was used to determine the macroscopic (emergent) properties, overall health and propagation of dynamical higher order effects within this complex Antarctic ecological system in response to simulated impacts. The magnitude of the Relative Ascendency, Relative Overhead, and Redundancy values indicates that the coastal benthic/pelagic Fildes Bay system is likely to remain less developed and therefore more resistant to perturbations than other ecological systems dominated by brown macroalgae. In terms of model component contributions to the Ascendency, detritus accounted for ∼33% of the value, followed by the phyto-zooplankton complex (∼26%), macroalgae (∼19%), filter-feeders (∼7%), small epifauna (5%), and top predators (2%). Short-term or transient Ecosim dynamical responses to increase the total mortality of each model component-given mixed and top-down vulnerabilities-revealed that changes in macroalgae levels had a limited impact on the other components of the system. The filter feeder, small epifauna and benthic fishés functional groups had the greatest effects on the remaining Fildes Bay system components. The magnitude of the System Recovery Time indicated that the Nacella concinna and small epifauna components would take the longest time to return to their initial state. Based on the outcomes obtained from the model, we suggest that this preliminary trophic model, including simulated impacts, provides promising possibilities for the determination of macroscopic baseline conditions and the most sensitive components of the Fildes Bay ecological system.     

Deep-Sea Polychaetous Annelida from Central America to the Antarctic Peninsula and South Sandwich Islands

Based on the 1958 Vema cruise and the 1965 Anton Bruun cruise 11 off the west coast of Central America and south through the islands east of the tip of South America, 143 trawl samples were examined for abyssal polychaetous annelida. The cruise tracks designated 7 major areas: Central America (1), Ecuador-Peru (II), Central and Southern Chile (III), Chile and the Magellan Strait (IV), Tierra del Fuego (V), the Island Complex (Falkland, South Georgia and South Sandwich Islands) (VI), the Drake Strait and Antarctic Peninsula (VII). The collections yielded 7,015 individuals and 322 species from 52 families. The relatively small number of species was attributed mainly to sampling effort, collecting gear and processing techniques. Each major area was characterized in terms of the number of individuals, the number of species, mean number of individuals, mean number of species and mean H′, SR, J′ and DI. Species diversity was significantly higher in Central America (I) than in the other areas. The relationships between biotic and abiotic measures (depth and areas of upwelling) were examined. There were no significant associations for the entire data base with depth. Moreover, there was no association between abundance of polychaetes and areas of upwelling which was hypothesized. In fact, relative abundance was highest in the deepest portions of Central America (I) (Guatemala Basin) and Ecuador—Peru (II) (Milne—Edwards Deep) compared to shallower areas closer to areas of upwelling. Quantitative collecting gear and refined processing techniques will be required to more accurately address these relationships. Dominant families were identified in terms of number of species and number of individuals. These families conformed well with world wide generalizations of dominant families. Dominant species were identified based on the Biological Index Value. The top twenty or dominant species for each major area were identified. A number of these dominant species occurred widely throughout the major areas. The dominant species for the entire data set were determined. In general these species were very eurybathic which was consistent with other worldwide depth distributions of abyssal polychaetes. Based on biotic measures (mean number of species, mean H', SR, J′ and DI) and the Simpson and Dice similarity co-efficients, several zoogeographic patterns emerged. The polychaete fauna from Central America (I) to southern Chile (II) formed a relatively homogeneous group. Polychaetes from Central America (I) had affinities with faunas studied off western Mexiko. The Chile and Magellan Strait (IV) area seemed to be a transition area which yielded to another relatively homogeneous fauna comprising areas V—VII. The latter fauna belonged to an Antarctic polychaete fauna which was documented earlier in other studies with a larger data base and more sophisticated analysis. It is hoped that the present study will help to provide a start to fill the zoogeographic gap of this enormous and bathymetrically diverse area.     

Age and early life history of juvenile scotia sea icefish, <Emphasis Type="Italic">Chaenocephalus aceratus</Emphasis>, from Elephant and the South Shetland Islands

The otolith microstructure of juvenile Scotia Sea icefish (Chaenocephalus aceratus) was analyzed from samples collected around Elephant and South Shetland Islands, with the aim to validate previous annual ageing and to give new insight into its early life history timings. Fish were caught by bottom trawl fishing conducted on the continental shelf between 100 and 500 m depth. To determine the timing and position of the first annulus on sagittal otoliths, microincrements were counted on juvenile otoliths previously aged 1+ year old by counting annuli in sectioned otolith. Assuming that microincrements were laid down daily, age ranged from 406 to 578 days in fish measuring 13–19 cm TL, thus corroborating previous results. The relationship between fish size and otolith size/weight was estimated using the least square linear regression method. The relationship between age and otolith size was also estimated to determine the otolith length in 1-year old fish, which was approximately 1.58 mm. In all samples the otolith core was characterized by an evident strong check, assumed to be laid down at the beginning of exogenous feeding of yolk sac larvae. The yolk sac duration estimated from hatch to the first feeding check was longer than other channichthyids, lasting 29–45 days. Hatching dates were backcalculated from the date of capture using the age estimates, indicating C. aceratus sampled off Elephant and South Shetland Islands hatched over a long period lasting from July to December, with a peak in November. As a result, the potential larval dispersion driven by local oceanographic features is discussed.     

南沙群岛渚碧礁大型底栖动物群落特征

利用2002年5月12日至5月21日在南沙群岛渚碧礁用轻潜水(SCUBA)方法于该礁盘不同位置设立的4个定量取样站采集的调查资料,采用IRI指数、ABC曲线方法和大型多元统计分析软件PRIMER对渚碧礁大型底栖动物进行等级聚类分析(CLUSTER)和非度量MDS标序,研究群落结构格局以及用Shannon-Wiener指数、物种丰富度指数和物种均匀度指数分析物种多样性和群落种类组成的相似程度,对渚碧礁大型底栖动物的群落结构进行了初步研究。结果表明:调查获得渚碧礁调查站大型底栖动物总种数314种,平均栖息密度为357.94个/m2,平均生物量为64.85g/m2;群落中主要的重要种或优势种为粗糙毛壳蟹(Pilodius scabriculus)和鼓虾(Alpheus spp.),但IRI指数相对较低;群落结构聚类分析和MDS标序表明,4个取样站的群落结构非常相似,Bray-Curtis相似性系数达到80%以上。