Amundsen Sea Mollusca from the BIOPEARL II expedition (original) (raw)
Related papers
Benthic mollusc assemblages in West Antarctica: taxa composition and ecological insights
Marine and Freshwater Research, 2017
Although different studies in Antarctica have dealt with benthic communities, few studies have focused on molluscan assemblages and their ecology. During the austral summer of 2011, 17 stations between depths of 68.5 and 754m were sampled in West Antarctica using a demersal bottom trawl pilot net on board RV ARA Puerto Deseado. In all, 1848 specimens of shelled molluscs were recorded. Gastropods were the most diverse group (species richness=74) and bivalves were the most abundant (n=1344). Shannon–Wiener diversity index values ranged between 0.58 and 2.99, with great variation at different stations. Cluster analysis using the Bray–Curtis coefficient showed three distinct assemblages types: one dominated by suspension feeders; a second with representatives from different trophic groups, including suspension feeders, grazers, scavengers, predators and deposit feeders; and a third, more differentiated, with few taxa and dominated by deposit feeders. Finally, multivariate analysis sugge...
Marine Biodiversity, 2009
Concerted efforts are being made to understand the current and past processes that have shaped Antarctic biodiversity. However, high rates of new species discoveries, sampling patchiness and bias make estimation of biodiversity there difficult. Antarctic continental shelf benthos is better studied in the Ross, Weddell and Scotia seas, whilst the Amundsen Sea has remained biologically unexplored largely because of severe ice conditions yearround. Here we report results from examination of the first benthic biological samples taken from the Amundsen Sea. We compare relative abundance, taxonomic richness and faunal composition of isopod families, and genera and species within two example families (i.e. Desmosomatidae and Nannoniscidae) from the Amundsen Sea with complementary sampling from the Scotia Sea. Benthic samples were taken from inner and outer Pine Island Bay (eastern Amundsen Sea) sites using an epibenthic sledge at 500 m. Similar samples were also collected from 15 Scotia arc sites at 160-to 500-m depths. The relative abundance of isopods in the Amundsen Sea samples was high and surprisingly less variable than across samples in the Scotia Sea. The abundance structure of isopods at family level was compared across different Antarctic seas. We found that in the Amundsen, Scotia and Ross Seas two families dominated abundance. In contrast, isopod abundance reported in the literature from Weddell Sea samples was much more evenly distributed across families. The Amundsen continental shelf isopod fauna appears to be rich, with 96% of individuals belonging to currently undescribed species. Most of the genera have either been described or found elsewhere, but for many of these genera it is the first time they have been recorded away from the Antarctic continental slope or deep sea. The Amundsen Sea assemblages differed greatly from the Scotia Sea sites in terms of both composition and (species and generic) richness. This was largely due to high consistency between samples compared with the highly variable Scotia Sea samples. Thorough biological analyses implementing well-structured geographic sampling regimes and the application of phylogeographic analyses on a variety of taxa are required to further explore the geographic structure of biodiversity and the evolutionary history of the Amundsen Sea.
Diversity and Distributions, 2007
The aim of this study was to use data for gastropod and bivalve molluscs to determine whether the fauna of the Southern Ocean is sufficiently well known to establish robust biogeographical and macroecological patterns. We chose molluscs for this work because they have been collected by almost every biological expedition to Antarctica, and are relatively well known taxonomically. Sampling of the continental shelf fauna is reasonably full and extensive, although new species are still being described and there are significant gaps in sampling off Wilkes Land and in the Bellingshausen and Amundsen Seas. Species richness was highest in those areas that have been subject to the most intense research activity and this pattern remained even after correction for sampling intensity. The low species richness of the Southern Ocean molluscan fauna compared with many tropical sites is confirmed, and is related principally to the absence of the large number of rare taxa that characterize some tropical assemblages. There is as yet no convincing evidence for a latitudinal cline in molluscan diversity within the Southern Ocean. Multivariate analyses defined biogeographical provinces very similar to those established previously, though they also identified a number of finer-scale sub-provinces including a small area of high diversity off Enderby Land. Most Southern Ocean gastropods and bivalves are rare, with limited distributions; relatively few taxa have circumpolar distributions.
Polar Biology, 2008
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 bestrepresented 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 diVerent stations. Four groups of stations of low similarities and some diVerences 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.
2008
The knowledge of the systematics and distribution of molluscs from the area of West Antarctica, mainly of the Bellingshausen Sea, remains relatively poor. Only 3 families and 11 species of molluscs were recorded in the Bellingshausen Sea, while 2 families and 3 species were recorded from Peter I Island. This apparently low number of species is the result of poor sampling in this area. An integral study of the benthic ecosystem was carried out in this area by the Spanish Antarctic Program: BENTART research cruises during the austral summer season in 2003 and 2006 on the continental shelf and lower slope from 53 to 3304 metres. A total of 3133 individuals belonging to 118 species of shelled molluscs were identified, of which 571 individuals corresponding to 71 species of gastropods, 2200 individuals to 42 species of bivalves and 362 individuals to 5 species of scaphopods. <em>Neobuccinum eatoni </em>with 89 individuals, <em>Genaxinus debilis </em>with 674 indiv...
Polar Biology, 2001
During the research program BENTART 95, carried out from 16 January to 4 February 1995 on board RV Hesperides, a semi-quantitative Agassiz trawl and quantitative Van-Veen grabs were used at 31 subtidal stations between 40 and 850 m depth around Livingston Island, at Deception Island and in the Brans®eld Strait. These data were used to search for and analyse the malacological assemblages. Among the molluscs sampled were 1,786 individuals belonging to 70 species of Solenogastres, Gastropoda Prosobranchia and Opisthobranchia, Scaphopoda and Bivalvia. The values of Shannon-Wiener diversity index ranged between 0.00 (one specimen) and 3.95, while Pielou's evenness index varied between 0.0 and 1.00. The bivalve Thyasira cf. dearborni was the most abundant species (227 specimens). Species richness varied from 1 to 19 species. Diversity showed great variations at dierent stations. The clustering analysis applying the Bray-Curtis coecient allowed species classi®cation according to constancy and ®delity, and distinguished four groups of stations: one that gathers clearly the stations of the inner bay of Deception Island, excepting station 1, and the other three ®tting the remaining stations, located north and south of Livingston Island and in the Brans®eld Strait, and correlated with environmental factors (granulometric composition, organic matter and carbonates).
2007
The abyssal depths of the polar oceans are thought to be low in diversity compared with the shallower polar shelves and temperate and tropical deep-sea basins. Our recent study on the gastropod fauna of the deep Southern Ocean gives evidence of the existence of a rich gastropod assemblage at abyssal depths. During the ANDEEP I and II expeditions to the southern Drake Passage, Northwestern Weddell Sea, and South Sandwich Trench, gastropods were collected by bottom and Agassiz trawls, epibenthic sledge, and multicorer, at 40 stations in depths between 127 and 5194 m. On the whole, 473 specimens, corresponding to 93 species of 36 families, were obtained. Of those, 414 specimens were caught below 750 m depth and refer to 84 (90%) benthic species of 32 (89%) families. Most families were represented by a single species only. The numerically dominant families were Skeneidae and Buccinidae (with 10 and 11 species, respectively), Eulimidae and Trochidae (with 9 species each), and Turridae (6 species). Thirty-Seven benthic deep-sea species (44%) were represented by a single specimen, and another 20 species (24%) were found at a single station, suggesting that more than two thirds of Antarctic deep-sea gastropod species are very rare or have a very scattered distribution. Of the 27 species occurring at two or more deep-sea stations, 14 were collected with different gear. Approximately half of the deep-water species are new to science or have been recently described. The present investigation increases the total number of recorded benthic Antarctic deep-sea gastropods (below 750 m) from 115 to 177. The previously known depth ranges have been extended, often considerably, for 31 species. The collected deep-sea gastropods comprise both eurybathic shelf species (29%) and apparently true deep-sea species (58%); some of the latter may belong to a so far unknown Antarctic abyssal fauna. Geographical ranges of the collected Antarctic benthic deep-sea gastropod species appear limited, and all these 84 species seem endemic to Antarctica south of the Polar Front. Comparing diversity and abundances based on epibenthic sledge samples, there is no clear relationship between Antarctic deep-sea gastropod abundance and species richness with depth. However, both Antarctic and adjacent deep-sea areas are still far from being adequately sampled to allow more comprehensive conclusions. r
The Latitudinal Gradient Program (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011) aimed at understanding the marine and terrestrial ecosystems existing along the Victoria Land coast (Ross Sea), an area characterized by strong latitudinal clines in environmental factors. During the program's voyage of the Italian RV ''Italica'' in 2004, a fine-mesh towed gear, the ''Rauschert dredge'', was deployed for the first time at 18 stations in four latitudinal distinct shelf areas between *71°S and *74°S. The collected samples contained undescribed species and new records for the Ross Sea from a variety of different marine taxa. Here, we describe the molluscan fauna and investigate evidences for latitudinal effects on molluscan diversity, abundance and assemblage composition. No significant latitudinal trends were detected: while diversity did not vary significantly with latitude, species richness showed an apparent but non-significant decrease with increasing latitude. Beta-diversity was found to be high both within and between latitudinally distinct shelf areas. A large fraction (*20 %) of the collected molluscs corresponded to new species records for the Ross Sea or undescribed species. Rarity in Antarctic molluscan occurrences was confirmed, with singletons (i.e. species represented by only a single individual) accounting for a 22 % and uniques (i.e. species occurring in one sample only) for a 43.5 % of the total presence. Our study of the smaller macrofaunal benthic fraction showed that Antarctic marine research still has far to go to have robust reference baselines to measure possible changes in benthic communities, even in the case of the assumed well-known, wellsampled and well-studied group of Ross Sea shelf molluscs. We advocate the use of fine-mesh trawling gears for routine sampling activities in future Antarctic expeditions to assess the full marine biodiversity.
Spatial patterns of benthic diversity in molluscs from West Antarctica
Antarctic Science, 2009
Despite several works that have documented patterns of diversity in deep sea organisms, trends of diversity and the processes responsible for such trends still remain unclear. To date very few studies have documented the effects of variables such as latitude and longitude in deep-sea organisms in the Antarctic region. We explored the spatial patterns of diversity of benthic gastropods and bivalves in an extensive region about 2200 km long and 500 km wide from the South Shetland Islands to the Bellingshausen Sea in West Antarctica. A total of 134 species from 54 sites was recorded. Alpha diversity and beta diversity (measured as Whittaker's and Bray-Curtis similarity indices) were highly variable among areas. None of the species richness estimators measured as S obs , Chao2, Jacknife1 and Jacknife2, stabilized towards asymptotic values in any area. The number of rare species was large with almost half of species represented by 1 or 2 individuals (41%) and most species (62%) restricted to 1 or 2 sites. The partial Mantel test revealed that similarity between sites increased with the decrease of depth differences, but not with horizontal separation.