Biodiversity and function of bacteria in the Southern Ocean

A short overview of the biodiversity of Antarctic marine bacteria is given with respect to morphology and metabolic activity. The importance of spatial and temporal variability is described. The physiological adaptation and ecological function of Antarctic marine bacterioplankton are discussed.     

Towards a generalized biogeography of the Southern Ocean benthos

Aim To investigate whether the biogeographical regions proposed by J. W. Hedgpeth and widely adopted by other authors hold true, are an oversimplification or with further data might show a unified Antarctic province. Location Southern Hemisphere. Methods The distributions of 1318 species of bivalves, 4656 species of gastropods, 1465 species of cheilostome and 167 species of cyclostome bryozoans were analysed for 29 regions in the Southern Hemisphere, including South American, South African, Tasmanian, New Zealand, sub‐Antarctic and Antarctic regions. We present data on species richness, rates of endemism, patterns of radiation, faunal similarities and multivariate biogeographical analyses. Results The most striking pattern to emerge from our data set of species counts per region was a strong east–west hemispheric asymmetry, with high species numbers in New Zealand, Tasmania and South Africa and low numbers in South America. In contrast, no difference was found in richness between the east and west parts of the Southern Ocean. We compared findings in our model taxa with published data on ascidians, cephalopods and pycnogonids. Further evidence of strong faunal links between the Antarctic and South America is reported in this study, although we found little evidence for a biogeographical relationship between the Antarctic or South America and New Zealand/Tasmania. Strong evidence exists for a long‐term influence of the Antarctic Circumpolar Current upon the distribution of Southern Ocean benthos. This is demonstrated by the reduced prevalence of South American species in the Antarctic and sub‐Antarctic with increasing distance from South America in the direction of the current. Three of our four study taxa (bivalves, cheilostomes and cyclostomes) show the Southern Ocean as a ‘single functional unit’ with no evidence for a biogeographical split between east and west. Main conclusions Unlike the biogeographical schemes previously proposed, we show that biogeographical regions in the Southern Ocean differ depending upon the class of animals being considered. Despite this we suggest that some general rules are viable, including species endemism rates of around 50%, a single Antarctic province and a definite distinction between the sub‐Antarctic islands influenced by South America and those of New Zealand.     

Biodiversity and biogeography of the atmosphere

The variation of life has predominantly been studied on land and in water, but this focus is changing. There is a resurging interest in the distribution of life in the atmosphere and the processes that underlie patterns in this distribution. Here, we review our current state of knowledge about the biodiversity and biogeography of the atmosphere, with an emphasis on micro-organisms, the numerically dominant forms of aerial life. We present evidence to suggest that the atmosphere is a habitat for micro-organisms, and not purely a conduit for terrestrial and aquatic life. Building on a rich history of research in terrestrial and aquatic systems, we explore biodiversity patterns that are likely to play an important role in the emerging field of air biogeography. We discuss the possibility of a more unified understanding of the biosphere, one that links knowledge about biodiversity and biogeography in the lithosphere, hydrosphere and atmosphere.     

The development of planktonic biogeography in the Southern Ocean during the Cenozoic

Deep-sea drilling at high latitudes of the Southern Hemispheres has provided almost the only available data to evaluate the biogeographic development of the planktonic biota in the Southern Ocean during the Cenozoic (65 m.y. to Present Day). Paleontological investigations on Deep Sea Drilling Project (DSDP) materials have shown that the development of Cenozoic planktonic biogeography of the Southern Ocean is intimately linked with the evolution of the Southern Ocean water masses themselves. During the Cenozoic, this has included the development of the Circum-Antarctic Current system as obstructing land masses moved apart, the refrigeration and later extensive glaciation of the continent, and the development of the Antarctic Convergence (Polar Front) with related oceanic upwelling.Almost all evolution of calcareous planktonic microfossils has occurred outside of the Antarctic—Subantarctic region followed by limited migration into these water masses. Virtually no endemism occurs amongst calcareous microfossil groups at these latitudes. In contrast, conspicuous and widespread evolution has occurred within the siliceous microfossil groups especially during the Neogene. Low diversity and differences in stratigraphic ranges of Antarctic calcareous microfossils makes them only broadly useful for correlation. Relatively higher diversities within the Subantarctic provide a firmer basis for more detailed correlation, although the ranges of fossils are often different than at lower latitudes because of different paleoceanographic and paleoclimatic controls. Within the Antarctic water mass south of the Antarctic Convergence, siliceous microfossilsbiostratigraphy, oxygen isotopic stratigraphy and magnetostratigraphy, provide the only firm basis for correlation with low-latitude sequences.Eocene (55-38 Ma) sediments contain abundant calcareous microfossils even closely adjacent to the continent. Antarctic calcareous planktonic microfossils of this age exhibit relative high diversity, although this is lower than assemblages of equivalent age at middle and low latitudes. Within the Subantarctic region, Eocene planktonic foraminifera exhibit strong affinities with those in the temperate regions. Biogeographic differences exist between various sectors of the Southern Ocean related to biogeographic isolation preceding the development of the Circum-Antarctic Current. Subantarctic calcareous nannofossil assemblages of Paleocene and Eocene age exhibit higher diversity than Oligocene and Neogene assemblages. Siliceous microfossils are poorly represented or at best poorly known.One of the most dramatic changes in Southern Ocean planktonic biogeography occurred near the Eocene/Oligocene boundary (38 Ma). Since then, Antarctic planktonic foraminiferal assemblages have exhibited distinct polar characteristics, marked in particular by low diversity, and this event thus reflects the initiation of the Antarctic faunal and floral provinces. Profound paleoceanographic changes at this time, which triggered the biogeographic crisis, appear to be related to the initiation of widespread Antarctic sea-ice formation, and rapid cooling of deep and intermediate waters, in turn associated with increased Antarctic glaciation. During the Oligocene, planktonic microfossil diversity was low in all groups throughout the world's oceans. In Antarctic waters, the early Oligocene foraminiferal fauna is monospecific (Subbotina angiporoides), while in the later Oligocene two species (S. angiporoides and Catapsydrax dissimilis) were recorded. Calcareous nannofossil assemblages are of low diversity compared with the Eocene. Subantarctic foraminiferal faunas of Oligocene age display much higher diversity than those in the Antarctic, but early and middle Oligoceae faunas still exhibit the lowest diversities for the entire Cenozoic. Siliceous assemblages remain relatively inconspicuous in most regions of the Southern Ocean.The Paleogene-Neogene transition (22 Ma) is marked by a major change in the global planktonic biogeography, i.e. modern patterns developed in which permanent, steep faunal and floral diversity gradients existed between tropical and polar regions; a gradient which has persisted even during the most severe glacial episodes. Oligocene assemblages of low diversity and almost cosmopolitan distribution were replaced by distinctive belts of planktonic assemblages arranged latitudinally from the tropics to the poles. The establishment of the steep planktonic diversity gradients and latitudinal provinces near the beginning of the Neogene almost certainly were linked to the development of the Circum-Antarctic Current in the late Oligocene which effectively separated high- and low-latitude planktonic assemblages. These fundamental global circulation and biogeographic patterns have persisted through the Neogene.During the Neogene (22 Ma to Present Day), Antarctic calcareous microfossil assemblages exhibit persistent low diversity and high dominance, while Subantarctic assemblages are of much greater diversity. The beginning of the Neogene (= beginning of Miocene) heralded the development of the high-latitude siliceous microfossil assemblages towards their present-day dominant role. Siliceous biogenec productivity began to increase. These changes were linked to the initial development and later intensification of circulation associated with the Antarctic Convergence and Antarctic Divergence. The Antarctic Convergence sharply separates dominantly siliceous assemblages to the south from calcareous assemblages to the north. Radiolarian assemblages became more endemic. Relatively warm early and middle Miocene conditions are reflected by slightly higher diversity of planktonic foraminifera and by the presence, in the northern Subantarctic, of conspicuous discoasters in early Miocene sediments. In Antarctic waters, calcareous nannofossils become unimportant as biogenic elements after the middle Miocene.The latest Miocene ( 5 m.y. ago) was marked by northward movement of the Antarctic Convergence, corresponding expansion of the Antarctic water mass, and low diversity of calcareous assemblages. Pliocene planktonic foraminifera seem to be largely monospecific in Antarctic and southern Subantarctic sequences. During the Quaternary, Antarctic waters reached a maximum northward expansion and exhibit highest siliceous biogenic productivity for the Cenozoic. In the Subantarctic, Quaternary foraminiferal diversities are much higher than in Pliocene sequences. Although calcareous nannofossil diversity may be high, only a few species are abundant. Large northward shifts of Antarctic and Subantarctic water masses have occurred during the Quaternary although no southward penetrations have occurred much beyond that of the present day. Several radiolarian and foraminiferal species disappeared or appeared at or close to a number of paleomagnetic reversals during the last 4 m.y. These faunal events, which provide valuable datums, do not seem to be associated with major climatic changes.     

Biodiversity and biogeography of Henderson Island's insects

Henderson Island is an example of a raised coral atoll, and as such supports a much more diverse biota than geographically similar low atolls. It is also, due to its remote location, largely undisturbed by the activities of humans. It is therefore unique in the Pacific Ocean, and comparable to Aldabra in the Indian Ocean. Biogeographically it is also interesting as it is amongst the most easterly islands of the Indo-West Pacific region, and has been largely colonized by species dispersing from island to island across the ocean from the west. New and extensive collections of insects were made in 1991. Although not fully identified yet, it is clear that the fauna is depauperate, with only about 180 species known to date. Despite its easterly location almost all species are derived from the west, and much of the fauna is likely to be indigenous. The most diverse orders are the Lepidoptera ( c. 53 spp.), Coleoptera ( c. 38 spp.), Diptera ( c. 37 spp.), Hymenoptera ( c. 21 spp.), Homoptera ( c. 14 spp.) and Heteroptera (4 spp.). Of particular interest are the weevils, Heteroptera and Homoptera which exhibit considerable endemism with perhaps some examples of intra-island radiation. Although depauperate, Henderson supports a much larger insect fauna than that of nearby Ducie Atoll (total known insect fauna =15 spp).     

Diatoms shape the biogeography of heterotrophic prokaryotes in early spring in the Southern Ocean

The interplay among microorganisms profoundly impacts biogeochemical cycles in the ocean. Culture-based work has illustrated the diversity of diatom–prokaryote interactions, but the question of whether these associations can affect the spatial distribution of microbial communities is open. Here, we investigated the relationship between assemblages of diatoms and of heterotrophic prokaryotes in surface waters of the Indian sector of the Southern Ocean in early spring. The community composition of diatoms and that of total and active prokaryotes were different among the major ocean zones investigated. We found significant relationships between compositional changes of diatoms and of prokaryotes. In contrast, spatial changes in the prokaryotic community composition were not related to geographic distance and to environmental parameters when the effect of diatoms was accounted for. Diatoms explained 30% of the variance in both the total and the active prokaryotic community composition in early spring in the Southern Ocean. Using co-occurrence analyses, we identified a large number of highly significant correlations between abundant diatom species and prokaryotic taxa. Our results show that key diatom species of the Southern Ocean are each associated with a distinct prokaryotic community, suggesting that diatom assemblages contribute to shaping the habitat type for heterotrophic prokaryotes.     

A Hierarchical Classification of Benthic Biodiversity and Assessment of Protected Areas in the Southern Ocean

An international effort is underway to establish a representative system of marine protected areas (MPAs) in the Southern Ocean to help provide for the long-term conservation of marine biodiversity in the region. Important to this undertaking is knowledge of the distribution of benthic assemblages. Here, our aim is to identify the areas where benthic marine assemblages are likely to differ from each other in the Southern Ocean including near-shore Antarctica. We achieve this by using a hierarchical spatial classification of ecoregions, bathomes and environmental types. Ecoregions are defined according to available data on biogeographic patterns and environmental drivers on dispersal. Bathomes are identified according to depth strata defined by species distributions. Environmental types are uniquely classified according to the geomorphic features found within the bathomes in each ecoregion. We identified 23 ecoregions and nine bathomes. From a set of 28 types of geomorphic features of the seabed, 562 unique environmental types were classified for the Southern Ocean. We applied the environmental types as surrogates of different assemblages of biodiversity to assess the representativeness of existing MPAs. We found that 12 ecoregions are not represented in MPAs and that no ecoregion has their full range of environmental types represented in MPAs. Current MPA planning processes, if implemented, will substantially increase the representation of environmental types particularly within 8 ecoregions. To meet internationally agreed conservation goals, additional MPAs will be needed. To assist with this process, we identified 107 spatially restricted environmental types, which should be considered for inclusion in future MPAs. Detailed supplementary data including a spatial dataset are provided.     

Biodiversity and biogeography of southern temperate and polar bryozoans

Aim To describe the distribution of biodiversity and endemism of bryozoans in southern temperate and polar waters. We hypothesized that we would find: (1) no strong latitudinal richness gradient; (2) striking contrasts in richness and endemism between clades and between regions; and (3) that faunal similarity of regions would cluster geographically around each southern continent. Location South Atlantic, Indian and Pacific Oceans and the Southern Ocean. Methods We constructed a data base from known literature, regional data bases and recent finds. We regionalized each southern continent, calculated levels of richness and endemism for each region and continent, and used primer 5 to perform multivariate statistical analysis. Results A third (1681) of global bryozoan species described occur south of 30° S, of which c. 87% were cheilostomes. In richness we found no latitudinal cline and change across longitude was stronger. New Zealand was richest and had the most (60%) endemic species, followed by Antarctica at 57%. There were striking contrasts in regional richness and endemism between clades but the highest levels of between‐region similarity were around Antarctica. The timing of past continent connectivity was reflected. Main conclusions Bryozoans show strong hemispherical asymmetry in richness and, like molluscs and corals, decrease away from Australasia rather than with latitude. Species endemism is much lower in Antarctic bryozoans than previously thought, and as this taxon is not particularly dispersive and is now amongst the best studied regionally, maybe Antarctic endemism in general is lower and Antarctica less cut‐off to species dispersal than previously thought. However, Antarctic generic endemism is double the level previously calculated and regional faunal similarities are much higher than around other continents – both reflecting long‐term isolation. Bryozoans, in contrast to the paradigm of Antarctic fauna, may be fairly robust to predicted climate change. Paradoxically, they may also be one of the best taxa to monitor to sensitively detect marine benthic responses.     

Biodiversity and emerging biogeography of the neutrophilic iron-oxidizing Zetaproteobacteria

Members of the neutrophilic iron-oxidizing candidate class Zetaproteobacteria have predominantly been found at sites of microbially mediated iron oxidation in marine environments around the Pacific Ocean. Eighty-four full-length (>1,400-bp) and 48 partial-length Zetaproteobacteria small-subunit (SSU) rRNA gene sequences from five novel clone libraries, one novel Zetaproteobacteria isolate, and the GenBank database were analyzed to assess the biodiversity of this burgeoning class of the Proteobacteria and to investigate its biogeography between three major sampling regions in the Pacific Ocean: Loihi Seamount, the Southern Mariana Trough, and the Tonga Arc. Sequences were grouped into operational taxonomic units (OTUs) on the basis of a 97% minimum similarity. Of the 28 OTUs detected, 13 were found to be endemic to one of the three main sampling regions and 2 were ubiquitous throughout the Pacific Ocean. Additionally, two deeply rooted OTUs that potentially dominate communities of iron oxidizers originating in the deep subsurface were identified. Spatial autocorrelation analysis and analysis of molecular variance (AMOVA) showed that geographic distance played a significant role in the distribution of Zetaproteobacteria biodiversity, whereas environmental parameters, such as temperature, pH, or total Fe concentration, did not have a significant effect. These results, detected using the coarse resolution of the SSU rRNA gene, indicate that the Zetaproteobacteria have a strong biogeographic signal.     

3. Biodiversity, biogeography and conservation of diatoms

Recent morphometric and breeding studies of diatoms show that the present species classification is too coarse and hides significant diversity. Many species are subdivided into phenodemes, which often differ in cell size, shape, stria density and pattern, but may also have different ultrastructural features. In raphid diatoms these can include the form of the raphe endings, details of the pore occlusions, and the structure of the girdle, while chloroplast structure can also vary. The phenodemes can be sympatric or allopatric. In Sellaphora pupula and other species, sympatric phenodemes are reproductively isolated. It is recommended that such demes are recognized as separate species; the total number of diatom species worldwide may thus be at least 2 × 10⁵. Use of a fine-grained classification reveals that many diatom species may be endemics, some restricted to a single lake or catchment, others to wider areas. Environmental impact assessments and conservation strategies must begin to take account of endemism and rarity among microscopic algae and protists.     

Biodiversity of Pacific Ocean fishes

Table of Contents

Biodiversity of Pacific Ocean fishes     

The deep-water pycnogonids (Arthropoda: Pycnogonida) of the northeastern Atlantic Ocean

Over 2000 specimens of pycnogonid from deep-sea collections made in the northeastern Atlantic Ocean by IOS and SMBA between 1971 and 1994 have been analysed. Thirty-five species were identified, two being new to science, viz Nymphon akanthochoeros and an unnamed Anoplodactylus species. The deep-sea Pycnogonida of the northeastern Atlantic are reviewed using these data and records from the literature. Keys are presented for the six families represented by more than one species. The pycnogonid fauna of this area is characterized particularly by Paranymphon spinosum and Colossendeis clavata , with other dominant species including Colossendeis species, notably C. macenima , and Nymphon laterospinum, Anoplodactylus typhlops and A. arnaudae. Of the 54 species recorded below 200 m in the northeastern Atlantic, available evidence suggests that nine are 'endemic'. Relative distributions of the other species are discussed. A distinct change in the pycnogonid fauna with depth was found at around 1400 m. There is latitudinal separation of species groupings, shown most conspicuously by the shallower water species.     

海洋微型底栖生物的多样性与地理分布

海洋微型底栖生物是指生活于海洋沉积物中及表面的所有单细胞原核和真核微型生物,包括原核微生物、真核微藻及原生动物等光合自养和异养的类群.与水体相比,海洋底栖生境孕育了形态和功能多样性更高的微型生物,在陆架浅海单位体积沉积物中其丰度较之水体中同类生物高一至几个数量级,而深海则孕育着特殊进化环境下新奇多样且数量庞大的微型底栖生物,是维持海洋生物多样性、海洋生态系统结构和功能不可或缺的部分.迄今对于微型生物是全球性还是限定性分布一直存在争议,对其解答受到分类研究欠缺及采样不足的制约.分子生物学从正反两方面提供了理论依据,但无法得出一个普遍接受的观点.海洋微型底栖生物的多样性研究侧重于物种多样性及群落结构与分子多样性,较为显著的进展体现在原核微生物的分子多样性及底栖真核微藻的物种多样性研究,对于海洋底栖原生动物的多样性研究则相较滞后.本文综述了国内外对海洋微型底栖生物各主要类群的分类学和多样性研究进展,探讨了各类群在全球的潜在物种多样性,并就我国未来加强海洋微型底栖生物多样性构成、分布与变动及驱动变化的因子以及底栖微食物网的研究提出了建议.     

The Evolutionary Origins of the Southern Ocean Philobryid Bivalves: Hidden Biodiversity,Ancient Persistence

Philobryids (Bivalvia: Arcoida) are one of the most speciose marine bivalve families in the Southern Ocean and are common throughout the Southern Hemisphere. Considering this diversity and their brooding reproductive mode (limiting long-distance dispersal), this family may have been present in the Southern Ocean since its inception. However Philobrya and Adacnarca appear only in the Quaternary fossil record of the Antarctic, suggesting a much more recent incursion. Molecular dating provides an independent means of measuring the time of origin and radiation of this poorly known group. Here we present the first combined molecular and morphological investigation of the Philobryidae in the Southern Ocean. Two nuclear loci (18S and 28S) were amplified from 35 Southern Ocean Adacnarca and Philobrya specimens, with a combined sequence length of 2,282 base pairs (bp). Adacnarca specimens (A. nitens and A. limopsoides) were resolved as a strongly supported monophyletic group. Genus Philobrya fell into two strongly supported groups (‘sublaevis’ and ‘magellanica/wandelensis’), paraphyletic with Adacnarca. The A. nitens species complex is identified as at least seven morpho-species through morphological and genetic analysis of taxon clustering. Phylogenetic analyses resolve Philobryidae as a strongly supported monophyletic clade and sister taxon to the Limopsidae, as anticipated by their classification into the superfamily Limopsoidea. Bayesian relaxed clock analyses of divergence times suggest that genus Adacnarca radiated in the Southern Ocean from the Early Paleogene, while P. sublaevis and P. wandelensis clades radiated in the late Miocene, following the formation of the Antarctic Circumpolar Current.     

Biodiversity and structure of the suprabenthic assemblages from South Shetland Islands and Bransfield Strait,Southern Ocean

During the austral summer 1995, suprabenthic samplings were carried out at 24 stations (depth range 45–649 m) located around Livingston Island, within the caldera of Deception Island and in the Bransfield Strait. At each station, the near-bottom motile fauna was simultaneously collected with a multinet Macer-GIROQ sled in three water layers above the bottom. This study presents original data on the occurrence, diversity, vertical distribution and abundance of suprabenthic taxa in this near-bottom environment. The most speciose taxa were amphipods (at least 140 spp.), followed by isopods (66 spp.), pycnogonids (31 spp.) and mysids (19 spp.). Total abundances ranged between 31 ind./100 m² (Bransfield Strait, 361 m depth) and 6817 ind./100 m² (South Livingston Island, 163 m depth). According to stations, the groups numerically dominant and more frequent were amphipods (17 stations) or mysids (seven stations). Four suprabenthic assemblages were discriminated in the study area, apparently more structured by the degree of shelter-exposure and development of sessile epifauna than by water depth or sediment features.     

Temperature-driven biogeography of the deep-sea family Lithodidae (Crustacea: Decapoda: Anomura) in the Southern Ocean

Species’ distributions are dynamic and are linked to the changing physical environment. Temperature is considered to be a major factor influencing biogeography, especially in ectotherms such as the family Lithodidae. Lithodids are rare amongst decapods in their ability to inhabit the higher latitudes of the Southern Ocean; however, they are usually found in locations where water temperature is above 0.5°C. This study, for the first time, provides a baseline indication of the limits of the lithodid distribution around Antarctica, which will be instrumental in any future work on range extensions in this group. The distribution of lithodids is likely to change as temperatures along the West Antarctic Peninsula continue to rise, and range extensions by durophagous predators, such as the lithodids, are regarded as a potential threat to the unique structure of Antarctic continental-shelf ecosystems.