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The biophysics of water, has been debated over more than a century. Although its importance is still underestimated, significant breakthroughs occurred in recent years. The influence of protein condensation on water availability control was documented, new findings on water-transport proteins emerged, and the way water molecules rearrange to minimize free energy at interfaces was deciphered, influencing membrane thermodynamics. The state of knowledge continued to progress in the field of deep-sea marine biology, highlighting unknown effects of high hydrostatic pressure and/or temperature on interactions between proteins and ligands in extreme environments, and membrane structure adaptations. The role of osmolytes in protein stability control under stress is also discussed here in relation to fish egg hydration/buoyancy. The complexity of water movements within the cell is updated, all these findings leading to a better view of their impact on many cellular processes. The way water flow and osmotic gradients generated by ion transport work together to produce the driving force behind cell migration is also relevant to both marine biology and cancer research. Additional common points concern water dynamic changes during the neoplastic transformation of cells and tissues, or embryo development. This could improve imaging techniques, early cancer diagnosis, and understanding of the molecular and physiological basis of buoyancy for many marine species. [ABSTRACT FROM AUTHOR]

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In the 1950s, the Danish Galathea Expedition undertook one of the first and most comprehensive explorations of our ocean's hadal zone, depths extending from 6,000 to nearly 11,000 m, and presented a rich collection of the diversity of Amphipoda. The subsequent papers, however, concluded that these established 'nothing essentially new' to the existing knowledge of amphipod biology. Since Dahl's foundational paper in 1959, amphipods, primarily from the superfamilies Lysianassoidea and Alicelloidea, emerged as one of the best-sampled hadal fauna, as these mobile invertebrates are readily recovered by different sampling techniques. Importantly, amphipods have become the model taxon, helping us to unlock knowledge about life in the hadal zone. In this review, we collate the knowledge gained since the Galathea Expedition and summarise the current understanding of how amphipods that appear during hadal exploration survive the trench environments. We discuss population structures across depth, inter-trench distribution and connectivity, applications in hadal microbiology, and, critically, how the hadal zone is being impacted by anthropogenic activity. [ABSTRACT FROM AUTHOR]

In the field of image processing, due to the need of expertise and skills in deep-sea biology and the disadvantages of high labor cost and long time consuming, it has always been a difficult task to mark the images of deep-sea benthic organisms. To solve this problem, this paper proposes a new image intelligent labeling algorithm LACP AL (Localization-Aware-Choice and Pseudo Label Active Learning) which is based on Localization-Aware Active Learning. LACP AL is an active learning framework based on Faster R-CNN, it finds the "valuable" samples from unlabeled samples by clustering algorithm for every training; it selects hard-toidentify samples for manual annotation and further optimizes the model; and it proposes an improved pseudo-labeling mechanism to expand the training set and improve the model accuracy. According to the publicly available dataset provided by 2020 China Underwater Robot Professional Contest, a series of experiments has been done to verify that our algorithm can achieve higher recognition accuracy with fewer training samples compared with the existing algorithms for Marine benthic image recognition. [ABSTRACT FROM AUTHOR]

Deep coral-dominated communities play paramount roles in benthic environments by increasing their complexity and biodiversity. Coral-associated microbes are crucial to maintain fitness and homeostasis at the holobiont level. However, deep-sea coral biology and their associated microbiomes remain largely understudied, and less from remote and abyssal environments such as those in the Clarion-Clipperton Fracture Zone (CCZ) in the tropical Northeast (NE) Pacific Ocean. Here, we study microbial-associated communities of abyssal gorgonian corals and anemones (>4,000 m depth) in the CCZ; an area harboring the largest known global reserve of polymetallic nodules that are commercially interesting for the deep-sea nodule mining. Coral samples (n = 25) belonged to Isididae and Primnoidae families, while anemones (n = 4) to Actinostolidae family. Significant differences in bacterial community compositions were obtained between these three families, despite sharing similar habitats. Anemones harbored bacterial microbiomes composed mainly of Hyphomicrobiaceae, Parvibaculales, and Pelagibius members. Core microbiomes of corals were mainly dominated by different Spongiibacteraceae and Terasakiellaceae bacterial members, depending on corals' taxonomy. Moreover, the predicted functional profiling suggests that deep-sea corals harbor bacterial communities that allow obtaining additional energy due to the scarce availability of nutrients. This study presents the first report of microbiomes associated with abyssal gorgonians and anemones and will serve as baseline data and crucial insights to evaluate and provide guidance on the impacts of deep-sea mining on these key abyssal communities. [ABSTRACT FROM AUTHOR]

The reproductive biology of deep-sea fishes is largely unknown because of the difficulty of behavioral observations in this environment. In this study, the reproductive behavior of the deep-sea snailfish, Careproctus pellucidus, which lives at depths > 200 m, was observed in an aquarium. Fishes were collected at a depth of approximately 300 m in the North Pacific Ocean (36°70′N; 141°00′E) in July and August 2018 and kept for observation until March 2019. We observed that spawning events usually took place between one male and one female. Males defended a spawning substrate against other males and exhibited body-wiggling behavior for both courtship and aggressive display. Females visited the male's territory and spawned a demersal adhesive egg mass on the substrate. The territorial male then sought the spawned eggs using the filamentous rays in the lower pectoral-fin lobe and released sperm when he located the eggs. Males remained near the spawning substrate after spawning but did not perform any parental care. Notably, sneaking behavior by a non-territorial male was observed in one case; this is the first report of this alternative reproductive strategy (or tactic) in a deep-sea fish. Our study reveals the spawning of C. pellucidus appear to use the mechanosensory lateral line and the chemical sense heavily to adapt to the dim sunlight deep-sea environment. [ABSTRACT FROM AUTHOR]

Deep-sea octocorals are common habitat-formers in deep-sea ecosystems, however, our knowledge on their early life history stages is extremely limited. The present study focuses on the early life history of the species Dentomuricea aff. meteor, a common deep-sea octocoral in the Azores. The objective was to describe the embryo and larval biology of the target species under two temperature regimes, corresponding to the minimum and maximum temperatures in its natural environment during the spawning season. At temperature of 13 ±0.5 °C, embryos of the species reached the planula stage after 96h and displayed a median survival of 11 days. Planulae displayed swimming only after stimulation, swimming speed was 0.24 ±0.16 mm s−1 and increased slightly but significantly with time. Under a higher temperature (15 °C ±0.5 °C) embryos reached the planula stage 24 h earlier (after 72 h), displayed a median survival of 16 days and had significantly higher swimming speed (0.3 ±0.27 mm s−1). Although the differences in survival were not statistically significant, our results highlight how small changes in temperature can affect embryo and larval characteristics with potential cascading effects in larval dispersal and success. In both temperatures, settlement rates were low and metamorphosis occurred even without settlement. Such information is rarely available for deep-sea corals, although essential to achieve a better understanding of dispersal, connectivity and biogeographical patterns of benthic species. [ABSTRACT FROM AUTHOR]

Resazurin (RZ) is a weakly fluorescent blue dye and can be reduced irreversibly to highly fluorescent pink resorufin (RF) that is reduced reversibly to colorless dihydroresorufin (hRF) by photo, deoxygenation, chemical reaction and reductive organic compounds produced through cell metabolism. Because of the reliable and sensitive fluorescence-color change and noninvasive features, RZ has been used widely as a redox indicator in cell viability/proliferation assays for bacteria, yeast, and mammalian cells. However, RZ is used rarely for physiological characterization of marine microorganisms. Here, we developed a custom-made irradiation and absorption-analysis device to assess the reducing capacity and physiologic status of marine bacterial cultures. We measured the absorption spectra of RZ, RF, and hRF in the presence of the reducing compound Na2S and under visible-light irradiation. After establishing appropriate parameters, we monitored the color changes of RZ and its reduced derivatives to evaluate the coherence between reducing capacity, bioluminescence and growth of the deep-sea bacterium Photobacterium phosphoreum strain ANT-2200 under various conditions. Emission of bioluminescence is an oxidation process dependent upon cellular reducing capacity. Growth and bioluminescence of ANT-2200 cell cultures were impeded progressively with increasing concentrations of RZ, which suggested competition for reducing molecules between RZ at high concentration with reductive metabolism. Therefore, caution should be applied upon direct addition of RZ to growth media to monitor redox reactions in cell cultures. Analyses of the instantaneous reduction velocity of RZ in ANT-2200 cell cultures showed a detrimental effect of high hydrostatic pressure and high coherence between the reducing capacity and bioluminescence of cultures. These data clearly demonstrate the potential of using RZ to characterize the microbial metabolism and physiology of marine bacteria. [ABSTRACT FROM AUTHOR]

William Beebe (1877–1962) was a very popular 20th century naturalist and an early proponent of studying all organisms in a habitat. Beebe's deep-sea work began with his Arcturus Oceanographic Expedition in 1925 with sampling closely modelled on the Michael Sars deep-sea expedition. Dissatisfied with ship-based sampling of stations for a few days at best, he established a field laboratory in Bermuda to do intensive deep-water sampling. From 1929 to 1934, plankton net tows were carried out at the same site, over several months each year, totalling over 1500 net tows in deep waters. Here, the sampling efforts and results are reviewed from both the Arcturus Expedition and the Bermuda station. Study of the deep-sea samples yielded 43 scientific articles, published from 1926 to 1952, on a large variety of taxa. Beebe is still a popular figure connected in the public view with deep-sea exploration from his famous Bathysphere dives at the Bermuda site. However, his name rarely, if ever, appears in academic reviews of deep-sea biology or deep-sea expeditions. This study is an attempt to draw attention to Beebe's considerable scientific deep-sea work and provide some speculation as to why his contributions might be neglected. [ABSTRACT FROM AUTHOR]

Nineteenth-century investigations of the deep sea provide a case study for black box science. Naturalists were forced to theorize about a space for which they had no direct sensory observations. This study traces the emergence of bathymetry and deep-sea biology and then analyzes how men of science dealt with the uncertainty associated with their black box practices. I argue that these investigators created multiple types of black boxes based on their uncertainties and that these black boxes did not operate equivalently. Consequently, scholars should be aware of the different categories of black boxes when they describe scientific practices. [ABSTRACT FROM AUTHOR]

Visual signals rapidly relay information, facilitating behaviors and ecological interactions that shape ecosystems. However, most known signaling systems can be restricted by low light levels--a pervasive condition in the deep ocean, the largest inhabitable space on the planet. Resident visually cued animals have therefore been hypothesized to have simple signals with limited informationcarrying capacity. We used cameras mounted on remotely operated vehicles to study the behavior of the Humboldt squid, Dosidicus gigas, in its natural deep-sea habitat. We show that specific pigmentation patterns from its diverse repertoire are selectively displayed during foraging and in social scenarios, and we investigate how these behaviors may be used syntactically for communication. We additionally identify the probable mechanism by which D. gigas, and related squids, illuminate these patterns to create visual signals that can be readily perceived in the deep, dark ocean. Numerous small subcutaneous (s.c.) photophores (bioluminescent organs) embedded throughout the muscle tissue make the entire body glow, thereby backlighting the pigmentation patterns. Equipped with a mechanism by which complex information can be rapidly relayed through a visual pathway under low-light conditions, our data suggest that the visual signals displayed by D. gigas could share design features with advanced forms of animal communication. Visual signaling by deep-living cephalopods will likely be critical in understanding how, and how much, information can be shared in one of the planet's most challenging environments for visual communication. [ABSTRACT FROM AUTHOR]

Kaikōura Canyon, offshore Aotearoa/New Zealand, is a hotspot for deep-sea benthic biology with globally high faunal abundance. The M w 7.8 Kaikōura earthquake in 2016 triggered a severe disturbance that reshaped the canyon, evacuating an estimated 850 metric megatonnes of sedimentary material down canyon. The Kaikōura Canyon habitat is now recovering from this removal of both seafloor substrate and associated organisms. We measured post-event benthic macrofauna density together with biomass and sediment properties and related these to infaunal bioturbation activity, sediment community oxygen consumption (SCOC) and associated benthic macronutrient biogeochemical fluxes. Three legacy sites were used as reference along a depth transect of the canyon axis at 917, 1249, and 1480 m water depths. We found distinct differences in benthic functioning between sites. While many parameters measured followed the expected relationships of decreasing with depth some benthic biological activity metrics did not. Our data suggests that the sites differ based on the relative impact and type of disturbance experienced during the earthquake-triggered, canyon-flushing event. We find SCOC was linked to bioturbatory behaviour and sediment organic matter content, rather than taxa density or biomass. While the greatest bioturbation activity was measured at the shallowest site, the greatest SCOC was measured at the middle depth site due to elevated sediment organic matter content. These observations provide a wider benchmark for infaunal bioturbation and faunal-mediated biogeochemical processes in deep-sea canyon environments and provide rare insights of recovery trajectories for deep-sea benthic communities and ecosystem function after large seafloor disturbances. • Post-event canyon benthic community abundance and function metrics decrease with depth for most parameters quantified. • Higher than expected sediment community oxygen consumption (SCOC) was measured at the middle depth site. • SCOC in the canyon is relatively high co mpared to other comparable Pacific deep-sea locations. • SCOC was linked to bioturbatory behaviour and sediment organic matter content, rather than faunal abundance or biomass. [ABSTRACT FROM AUTHOR]

Deep sea is the largest and likely the most biologically diverse ecosystem of the world, but it is also the most unknown. The Mediterranean Sea (< 1% of the ocean surface and contains only the 0.3% of its volume) is a hot spot of marine biodiversity containing ca 7.5% of the world marine biodiversity, associated with a multitude of habitats spreading from the coast to its dark portion (e.g., coral banks, seamounts, canyons, and hydrothermal vents). Its deep-sea ecosystems are increasingly subjected to direct anthropogenic impacts (including overfishing, chemical pollution, dumping, litter, and plastics), which are often over-imposed to the increasing effects of global change. Here, are illustrated the expected impacts of shifts in the main variables such as temperature, food supply, pH, and oxygen on the deep Mediterranean Sea ecosystems. One of the most consequences is related to shifts in the quality and quantity of the inputs of organic matter to the deep seafloor. The deep Mediterranean Sea is far more oligotrophic than other oceans at equal depths, and although deep-sea biota reacts to food shortage by increasing their efficiency in its use, a decrease in food availability can have dramatic effects on its food webs. The deep Mediterranean Sea is showing a clear rise of deep-water temperatures. In the last decades, deep-water warming is accelerating at unprecedented rates, causing a significant shift in biodiversity even for variations in the order of 0.1 °C. Higher temperatures increase deep-sea metabolism, thus exacerbating the effects of food limitation. Moreover, ocean acidification reduces the calcification capacity of corals and alters their metabolism. Although it can be expected that increasing temperatures might increase the potential spread of oxygen minimum zone, so far, only hypoxic events were reported in Mediterranean Sea. The analysis of potential ecosystem vulnerability indicates that the ecosystems that are most sensitive to global change are deep-water coral systems and deep-sea plains. In addition, deep-sea canyons are also likely increasingly subjected to physical disturbance as a result of the increase in the frequency and intensity of climate-driven episodic events. Available information also suggests that biodiversity and ecosystem functioning of the deep Mediterranean Sea is undergoing dramatic changes, which result in accelerated organic matter biogeochemical cycling, miniaturization of the organisms’ size, increased metabolism, dominance of the microbial components, and mortality rates of deep-sea biota. Given the high sensitivity of the Mediterranean Sea to global change in comparison with other oceanic regions, and the vulnerability of its deep-sea habitats/ecosystems, specific policy measures are needed to protect its biodiversity, restore damaged habitats, and increase deep-sea ecosystems resistance and resilience to the ongoing impacts of global change. [ABSTRACT FROM AUTHOR]

Vanhoeffenella is a common deep-sea monothalamous foraminifer, some species of which have a unique eye-like test morphology. Owing to its world-wide distribution, it has been recorded numerous times since the “heroic age” of the deep-sea exploration in the early 20th century. So far, only 4 species have been described, and no attempts have been made to estimate the real diversity of this peculiar genus. Over the last fifteen years, we have collected specimens of Vanhoeffenella from various deep-sea areas, providing the basis for an integrative taxonomy and biogeography of this genus. Here, we clarify the phylogenetic position of Vanhoeffenella and give an account of its diversity in the Atlantic, Arctic and Southern Oceans (the Weddell Sea) as revealed by genetic marker (SSU rDNA) and morphology. Our study shows that Vanhoeffenella branches within Clade F of monothalamids and incorporates at least 10 putative species. Some could be distinguished by either morphological or molecular features, but only the integrative taxonomic approach provides a robust way to assess their diversity. We examine the new material of the type species ( V. gaussi Rhumbler), redescribe the poorly-known V. oculus Earland and describe formally a fifth species, V. dilatata sp. nov. [ABSTRACT FROM AUTHOR]

Pollen from deep-sea sedimentary sequences provides an integrated regional reconstruction of vegetation and climate (temperature, precipitation, and seasonality) on the adjacent continent. More importantly, the direct correlation of pollen, marine and ice indicators allows comparison of the atmospheric climatic changes that have affected the continent with the response of the Earth's other reservoirs, i.e., the oceans and cryosphere, without any chronological uncertainty. The study of long continuous pollen records from the European margin has revealed a changing and complex interplay between European climate, North Atlantic sea surface temperatures (SSTs), ice growth and decay, and high- and low-latitude forcing at orbital and millennial timescales. These records have shown that the amplitude of the last five terrestrial interglacials was similar above 40°N, while below 40°N their magnitude differed due to precessionmodulated changes in seasonality and, particularly, winter precipitation. These records also showed that vegetation response was in dynamic equilibrium with rapid climate changes such as the Dangaard-Oeschger (D-O) cycles and Heinrich events, similar in magnitude and velocity to the ongoing global warming. However, the magnitude of the millennial-scale warming events of the last glacial period was regionally-specific. Precession seems to have imprinted regions below 40°N while obliquity, which controls average annual temperature, probably mediated the impact of D-O warming events above 40°N. A decoupling between high- and low-latitude climate was also observed within last glacial warm (Greenland interstadials) and cold phases (Greenland stadials). The synchronous response of western European vegetation/climate and eastern North Atlantic SSTs to D-O cycles was not a pervasive feature throughout the Quaternary. During periods of ice growth such as MIS 5a/4, MIS 11c/b and MIS 19c/b, repeated millennial-scale cold-air/warm-sea decoupling events occurred on the European margin superimposed to a long-term air-sea decoupling trend. Strong air-sea thermal contrasts promoted the production of water vapor that was then transported northward by the westerlies and fed ice sheets. This interaction between long-term and shorter timescale climatic variability may have amplified insolation decreases and thus explain the Ice Ages. This hypothesis should be tested by the integration of stochastic processes in Earth models of intermediate complexity. [ABSTRACT FROM AUTHOR]

The stress corrosion cracking (SCC) properties of X70 pipeline steel in simulated deep-sea environments was investigated in a high-pressure vessel with a constant loading device. The results reveal that the threshold stress, σ SCC , for SCC is 0.89σ b , 0.78σ b and 0.68σ b in a 3.5% NaCl solution (pH = 7) of 0.1 MPa, 5 MPa and 10 MPa, respectively. When the 3.5% NaCl solution pH value decreased to 3, σ SCC decreased further to 0.83σ b , 0.68σ b and 0.53σ b , corresponding to 0.1 MPa, 5 MPa and 10 MPa, respectively. These results indicate that the hydrostatic pressure (HP) promotes SCC, particularly in an acidified sodium chloride solution. Scanning electron microscopy (SEM) and confocal scanning laser microscopy showed that on the sample surface, the HP promoted pitting propagation and linkage, which then initiated microcracks in SCC. The hydrogen concentration was 0.10 ppm, 0.17 ppm and 0.23 ppm after a 200-h immersion in a 3.5% NaCl solution (pH = 7) of 0.1 MPa, 5 MPa and 10 MPa, respectively, revealing that the hydrogen concentration increased approximately linearly with the HP. This result indicated that much more hydrogen was involved in the SCC process in a solution under a higher hydrostatic pressure. The SCC mechanism is controlled by both anodic dissolution and hydrogen-induced cracking in deep-sea environment. [ABSTRACT FROM AUTHOR]

Large vesicomyid clams (Veneroida: Vesicomyidae: Pliocardiinae) are prominent members of the communities associated with sulphide-rich deep-sea habitats. Taxonomic uncertainties within the Pliocardiinae result from both plasticity in shell morphologies and the common occurrence of cryptic species. Molecular taxonomic studies have now clarified many species-level assignments and provided DNA-barcodes for more than 50 species worldwide. Nonetheless, genus-level assignments remain uncertain, because the existing COI barcode sequences are not sufficient for identifying higher-level groupings. To construct a robust phylogeny for this subfamily, we conducted a combined Bayesian analysis of the COI mitochondrial fragment and five additional independent nuclear gene segments. The phylogenetic results provide a better foundation for assessing genus-level assignments within the subfamily and reveal goals for future taxonomic research. Furthermore, morphological examinations helped to clarify and solidify generic classifications. Calibration of molecular clocks with recently verified fossil data permitted realistic estimates for the origins and evolutionary age of pliocardiins during the Cenozoic Era from a deep-dwelling ancestor. http://zoobank.org/urn:lsid:zoobank.org:pub:2554122D-96D4-4CBF-BC70-B017998AF64D [ABSTRACT FROM AUTHOR]

The Lago Sofia conglomerate in southern Chile is a deep-marine gravelly deposit, which is hundreds of meters thick and kilometers wide and extends laterally for more than 100 km, filling the foredeep trough of the Cretaceous Magallanes Basin. For understanding the depositional processes and environments of this gigantic deep-sea conglomerate, detailed analyses on sedimentary facies, architecture and paleoflow patterns were carried out, highlighting the differences between the northern (Lago Pehoe and Lago Goic areas) and southern (Lago Sofia area) parts of the study area. The conglomerate bodies in the northern part occur as relatively thin (< 100 m thick), multiple units intervened by thick mudstone-dominated sequences. They show paleoflows toward ENE and S to SW, displaying a converging drainage pattern. In the southern part, the conglomerate bodies are vertically interconnected and form a thick (> 400 m thick) conglomerate sequence with rare intervening fine-grained deposits. Paleoflows are toward SW. The north-to-south variations are also distinct in sedimentary facies. The conglomerate bodies in the southern part are mainly composed of clast-supported conglomerate with sandy matrix, which is interpreted to be deposited from highly concentrated bedload layers under turbidity currents. Those in the northern part are dominated by matrix- to clast-supported conglomerate with muddy matrix, which is interpreted as the products of composite mass flows comprising a turbidity current, a gravelly hyperconcentrated flow and a mud-rich debris flow. All these characteristics suggest that the Lago Sofia conglomerate was formed in centripetally converging submarine channels, not in centrifugally diverging channels of submarine fans. The tributaries in the north were dominated by mass flows, probably affected by channel-bank failures or basin-marginal slope instability processes. In contrast, the trunk channel in the south was mostly filled by tractive processes, which resulted in the vertical and lateral accretion of gravel bars, deposition of gravel dunes and filling of scours and channels, similar to deposits of terrestrial gravel-bed rivers. The trunk channel developed along the axis of foredeep trough and its confinement within the trough is probably responsible for the thick, interconnected channel fills. The large-scale architecture of the trunk-channel fills shows an eastward offset stacking pattern, suggesting that the channel migrated eastwards most likely due to the uplift of the Andean Cordillera. [ABSTRACT FROM AUTHOR]

Sinking of large organic food falls i.e. kelp, wood and whale carcasses to the oligotrophic deep-sea floor promotes the establishment of locally highly productive and diverse ecosystems, often with specifically adapted benthic communities. However, the fragmented spatial distribution and small area poses challenges for the dispersal of their microbial and faunal communities. Our study focused on the temporal dynamics and spatial distributions of sunken wood bacterial communities, which were deployed in the vicinity of different cold seeps in the Eastern Mediterranean and the Norwegian deep-seas. By combining fingerprinting of bacterial communities by ARISA and 454 sequencing with in situ and ex situ biogeochemical measurements, we show that sunken wood logs have a locally confined long-term impact (> 3y) on the sediment geochemistry and community structure. We confirm previous hypotheses of different successional stages in wood degradation including a sulphophilic one, attracting chemosynthetic fauna from nearby seep systems. Wood experiments deployed at similar water depths (1100–1700 m), but in hydrographically different oceanic regions harbored different wood-boring bivalves, opportunistic faunal communities, and chemosynthetic species. Similarly, bacterial communities on sunken wood logs were more similar within one geographic region than between different seas. Diverse sulphate-reducing bacteria of the Deltaproteobacteria, the sulphide-oxidizing bacteria Sulfurovum as well as members of the Acidimicrobiia and Bacteroidia dominated the wood falls in the Eastern Mediterranean, while Alphaproteobacteria and Flavobacteriia colonized the Norwegian Sea wood logs. Fauna and bacterial wood-associated communities changed between 1 to 3 years of immersion, with sulphate-reducers and sulphide-oxidizers increasing in proportion, and putative cellulose degraders decreasing with time. Only 6% of all bacterial genera, comprising the core community, were found at any time on the Eastern Mediterranean sunken wooden logs. This study suggests that biogeography and succession play an important role for the composition of bacteria and fauna of wood-associated communities, and that wood can act as stepping-stones for seep biota. [ABSTRACT FROM AUTHOR]

The Lau Integrated Study Site (ISS) has provided unique opportunities for study of ridge processes because of its back-arc setting in the southwestern Pacific. Its location allows study of a biogeographical province distinct from those of eastern Pacific and mid-Atlantic ridges, and crustal compositions along the ridge lie outside the range of mid-ocean ridge crustal compositions. The Lau ISS is located above a subduction zone, at an oblique angle. The underlying mantle receives water and other elements derived from the downgoing lithospheric slab, with an increase in slab influence from north to south. Water lowers the mantle melting temperature and leads to greater melt production where the water flux is greater, and to distinctive regional-scale gradients along the ridge. There are deeper faulted axial valleys with basaltic volcanism in the north and inflated axial highs with andesites in the south. Differences in igneous rock composition and release of magmatic volatiles affect compositions of vent fluids and deposits. Differences in vent fluid compositions and small-scale diffuse-flow regimes correlate with regional-scale patterns in microbial and megafaunal distributions. The interdisciplinary research effort at the Lau ISS has successfully identified linkages between subsurface processes and deep-sea biological communities, from mantle to microbe to megafauna.

Larval dispersal is an important ecological process of great interest to conservation and the establishment of marine protected areas. Increasing numbers of studies are turning to biophysical models to simulate dispersal patterns, including in the deep-sea, but for many ecologists unassisted by a physical oceanographer, a model can present as a black box. Sensitivity testing offers a means to test the models’ abilities and limitations and is a starting point for all modelling efforts. The aim of this study is to illustrate a sensitivity testing process for the unassisted ecologist, through a deep-sea case study example, and demonstrate how sensitivity testing can be used to determine optimal model settings, assess model adequacy, and inform ecological interpretation of model outputs. Five input parameters are tested (timestep of particle simulator (TS), horizontal (HS) and vertical separation (VS) of release points, release frequency (RF), and temporal range (TR) of simulations) using a commonly employed pairing of models. The procedures used are relevant to all marine larval dispersal models. It is shown how the results of these tests can inform the future set up and interpretation of ecological studies in this area. For example, an optimal arrangement of release locations spanning a release area could be deduced; the increased depth range spanned in deep-sea studies may necessitate the stratification of dispersal simulations with different numbers of release locations at different depths; no fewer than 52 releases per year should be used unless biologically informed; three years of simulations chosen based on climatic extremes may provide results with 90% similarity to five years of simulation; and this model setup is not appropriate for simulating rare dispersal events. A step-by-step process, summarising advice on the sensitivity testing procedure, is provided to inform all future unassisted ecologists looking to run a larval dispersal simulation. [ABSTRACT FROM AUTHOR]

The spread of human activities into the deep sea may pose a high risk to benthic communities and affect ecosystem integrity. The deep sea is characterized by physical and biological heterogeneity and different habitat types are likely to differ in their vulnerability to anthropogenic impacts. However, across-habitat comparisons are rare, and no comprehensive ecological risk assessment has yet been developed. To address this gap in our knowledge, we compared macro-infaunal community structure in four habitats (slope, canyons, seamounts and methane seeps) at depths between 700 and 1500 m in the Hikurangi Margin and Bay of Plenty regions off New Zealand. The most striking contrast in community structure was between the two study regions, due to an order of magnitude difference in macro-infaunal abundance that we believe was caused by differences in surface productivity and food availability at the sea bed. We found differences in structural and functional attributes of macro-infaunal communities among some habitats in the Hikurangi Margin (slope, canyon and seep), but not in the Bay of Plenty. We posit that differences between canyon and slope communities on the Hikurangi Margin are due to enhanced food availability inside canyons compared with adjacent slope habitats. Seep communities were characterized by elevated abundance of both symbiont-bearing and heterotrophic taxa, and were the most distinct, and variable, among the habitats that we considered on the Hikurangi Margin. Communities of seamounts were not distinct from slope or canyon communities on the Hikurangi Margin, probably reflecting similar environmental conditions in these habitats. The communities of deep-sea canyon and seep habitats on the Hikurangi Margin were sufficiently dissimilar from each other and from slope habitats to warrant separate management consideration. By contrast, the low dissimilarity between communities of canyon and slope habitats in the Bay of Plenty suggests that habitat-based management is not required in this region, for macro-infauna at least. Although the two study regions share similar species pools, populations of the Hikurangi Margin region may be less vulnerable than the sparser populations of the Bay of Plenty due to the higher availability of potential colonizers and faster population growth. Thus regions, and habitats in some regions, should be subject to separate ecological risk assessment to help identify the key risks and consequences of human activities, and to inform options for reducing or mitigating impacts. [ABSTRACT FROM AUTHOR]

ABSTRACT Temperature is considered to be a fundamental factor controlling biodiversity in marine ecosystems, but precisely what role temperature plays in modulating diversity is still not clear. The deep ocean, lacking light and in situ photosynthetic primary production, is an ideal model system to test the effects of temperature changes on biodiversity. Here we synthesize current knowledge on temperature-diversity relationships in the deep sea. Our results from both present and past deep-sea assemblages suggest that, when a wide range of deep-sea bottom-water temperatures is considered, a unimodal relationship exists between temperature and diversity (that may be right skewed). It is possible that temperature is important only when at relatively high and low levels but does not play a major role in the intermediate temperature range. Possible mechanisms explaining the temperature-biodiversity relationship include the physiological-tolerance hypothesis, the metabolic hypothesis, island biogeography theory, or some combination of these. The possible unimodal relationship discussed here may allow us to identify tipping points at which on-going global change and deep-water warming may increase or decrease deep-sea biodiversity. Predicted changes in deep-sea temperatures due to human-induced climate change may have more adverse consequences than expected considering the sensitivity of deep-sea ecosystems to temperature changes. [ABSTRACT FROM AUTHOR]

Fishing is a significant threat to marine biodiversity in areas beyond national jurisdiction (ABNJ). Bottom fishing in particular can impact deep-sea ecosystems, and the UN General Assembly has called on regional fisheries management organisations and arrangements (RFMO/As) to take actions to regulate bottom fisheries, including to close areas to bottom fishing activities where there is likely to be significant adverse impacts to vulnerable marine ecosystems (VMEs). This paper provides an update on the current status of closures, suggesting that RFMO/A biodiversity conservation efforts continue to advance slowly. RFMO/As have been slow to implement additional closures and to act in a precautionary manner based on available scientific evidence. Existing powers are not being fully utilised and best practice is not always followed. Closures have often been temporary or representative, or have not in fact restricted ongoing fishing activity. Some positive outcomes provide examples of good practice, though RFMO/As will need to fully utilise their powers and follow best practice before authorising bottom fishing to proceed in ABNJ. [ABSTRACT FROM AUTHOR]

Monetary valuation of non-market environmental goods and services such as marine ecosystems is a difficult task, usually approached by stated preference methods. Valuation results are often unstable since preferences for unfamiliar, often highly abstract and complex environmental goods depend on the level of previous knowledge of the participant stakeholders and the information provided to them. In this paper, Q methodology has been applied to explore subjective perspectives on Mediterranean deep sea, which is among the least explored environment in the world. The participant sample consisted in eight Ph.D. students, half of which with a Marine Life Sciences degree. They were asked to perform a Q-sorting experiment, and rank a Q sample of 36 underwater photographs of the marine wildlife, landscapes, and ecosystems in the Mediterranean deep sea. Photographs were sorted by each topic according to a subjective priority relative to (a) a personal overall view; (b) their perception of the potential interest for fishermen; and (c) as if they were fishermen. The study revealed three distinct discourses on the subjective importance of deep-sea ecosystems in the Mediterranean Sea: “Noah’s Ark Fans”, “Ecosystem Functions Supporters” and “Deep Coral Lovers”. Data analysis showed that the main differences between factors could be related to the experience and the cultural background of the participants. This study improved our knowledge about individuals’ perceptions on Mediterranean deep-sea ecosystems and represents a preliminary step for their monetary valuation. [ABSTRACT FROM AUTHOR]

Hydrothermal vents at the seafloor release large volumes of metal-rich fluids into the ocean. Some of these metals are biologically essential (such as Fe), while others may be toxic (e.g. Cu). Organisms living at these habitats produce small organic molecules, ligands that are able to form complexes with different metals, to either enhance their bioavailability or to decrease their toxicity. While some deep-sea vents have been studied with respect to metal complexation, comparable studies at shallow marine hydrothermal vent systems are rather rare. In this study, total dissolved Cu concentrations ([Cu] T ) and corresponding Cu binding ligand concentrations ([L] Cu ) at the shallow water hydrothermal vent fields off the coast of Milos (Greece), Dominica (Lesser Antilles) and the Bay of Plenty (New Zealand) were examined by a voltammetric ligand titration, using competitive ligand equilibration–adsorptive stripping voltammetry (CLE–AdCSV). Milos, Dominica and the Bay of Plenty are three very different environments and our data show that they are relatively depleted in total dissolved Cu, compared to deep-sea hydrothermal vents where [Cu] T and [L] Cu concentrations up to 400 nM and 4000 nM have been found, respectively. In this data set, [Cu] T rises up to 21.53 nM, however, most samples are in the range of 0.5 nM–3 nM. [L] Cu varies between 2.07 nM and 23.9 nM, with one exception, reaching 56.8 nM. Conditional stability constants (Log K) range between 11.57 and 14.01. Assuming that the three investigated sites are representative for shallow marine hydrothermal vents, the Cu-flux into the ocean due to complexation appears to be relatively low compared to deep-sea systems. Our data indicate a stable complexation of Cu in most cases, which may lower the toxic effect of Cu on these mixed photic–chemosynthetic communities. However one pore water sample from Dominica showed an excess [Cu] T over [L] Cu , which would create a highly toxic environment for most marine organisms. We further show that ligand–Cu ratios and complex stability constants are in a similar range as the ones at deep-sea vents, which may indicate similar complexation parameters and processes at shallow and deep-sea hydrothermal vents. [ABSTRACT FROM AUTHOR]

The article discusses a research which examines the taxonomy of deep-sea shrimps Plesionika quasigrandis which were collected from Sakthikulangara fishing port in the city of Kollam and from Kalamukku fishing port in Cochin, Kerela, India during 2013-2014. The study describes Plesionika quasigrandis as the dominant species among the deep sea shrimps landed in Kerala state. Also indicated is the connectivity between the Indian and Philippine shrimp populations.

The new features of the vertical phytoplankton distribution in the central and southern deep-water parts of the Caspian Sea are identified on the basis of long-term observations (2004-2012, 419 samples). Systematic study of phytoplankton in the Middle Caspian for nine years has shown that the interannual variability in the dominant summer phytoplankton complex is due to traditional species of diatoms and dinoflagellates and also coccolithophores, a new systematic group for the Caspian Sea (June 2010). It was first determined that summer phytoplankton of the deep-water parts in the Middle and Southern Caspian is similar in species, quantitative, and spatial (vertical) structure. A zone of higher phytoplankton productivity was first found in the area of the Absheron Sill. Two types of communities and their boundary were first distinguished in the vertical structure of summer phytoplankton of the deep-sea parts: warm-water and cold-water (below the thermocline). The boundary between them corresponds to the lower boundary of the seasonal thermocline (maximum depths up to 50-60 m) with the highest wet total phytoplankton biomass and chlorophyll a concentrations. The intensity of stratification of the water column by temperature mainly causes the vertical phytoplankton structure. The anomalously large deep-sea accumulations of diatoms cells containing chlorophyll (remains of winter-spring blooms) were first found in the near-bottom layers of the northern slope of the Derbent Depression. Their presence at the depths of 300-400 m is probably caused by the slope cascading. The lower boundary (500 m) of phytoplankton abundance in the Caspian Sea with chlorophyll-containing cells of fresh water green algae were registered by the authors for the first time in the central areas of the Derbent and South Caspian depressions. This phenomenon was caused by the contribution of cold Caucasus rivers through a system of submarine canyons from the shelf to the deep sea areas. [ABSTRACT FROM AUTHOR]