Distribution and diel vertical movements of mesopelagic scattering layers in the Red Sea

© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Biology 159 (2012): 1833-1841, doi:10.1007/s00227-012-1973-y.The mesopelagic zone of the Red Sea represents an extreme environment due to low food concentrations, high temperatures and low oxygen waters. Nevertheless, a 38 kHz echosounder identified at least four distinct scattering layers during the daytime, of which the 2 deepest layers resided entirely within the mesopelagic zone. Two of the acoustic layers were found above a mesopelagic oxygen minimum zone (OMZ), one layer overlapped with the OMZ, and one layer was found below the OMZ. Almost all organisms in the deep layers migrated to the near-surface waters during the night. Backscatter from a 300 kHz lowered Acoustic Doppler Current Profiler indicated a layer of zooplankton within the OMZ. They carried out DVM, yet a portion remained at mesopelagic depths during the night. Our acoustic measurements showed that the bulk of the acoustic backscatter was restricted to waters shallower than 800 m, suggesting that most of the biomass in the Red Sea resides above this depth.This research is based in part on work supported by Award Nos. USA 00002, KSA 00011 and KSA 00011/02 made by KAUST to the Woods Hole Oceanographic Institution

Metabolic suppression in thecosomatous pteropods as an effect of low temperature and hypoxia in the eastern tropical North Pacific

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Marine Biology 159 (2012): 1955-1967, doi:10.1007/s00227-012-1982-x.Many pteropod species in the eastern tropical north Pacific Ocean migrate vertically each day, transporting organic matter and respiratory carbon below the thermocline. These migrations take species into cold (15-10ºC) hypoxic water (< 20 µmol O2 kg-1) at depth. We measured the vertical distribution, oxygen consumption and ammonia excretion for seven species of pteropod, some of which migrate and some which remain in oxygenated surface waters throughout the day. Within the upper 200 meters of the water column, changes in water temperature result in a ~60-75% reduction in respiration for most species. All three species tested under hypoxic conditions responded to low O2 with an additional ~35-50% reduction in respiratory rate. Combined, low temperature and hypoxia suppress the metabolic rate of pteropods by ~80-90%. These results shed light on the ways in which expanding regions of hypoxia and surface ocean warming may impact pelagic ecology.This work was funded by National Science Foundation grants to K. Wishner and B. Seibel (OCE – 0526502 and OCE – 0851043) and to K. Daly (OCE – 0526545), the University of Rhode Island, and the Rhode Island Experimental Program to Stimulate Competitive Research Fellowship program.2013-06-3

Taxonomic diversity and identification problems of oncaeid microcopepods in the Mediterranean Sea

The species diversity of the pelagic microcopepod family Oncaeidae collected with nets of 0.1-mm mesh size was studied at 6 stations along a west-to-east transect in the Mediterranean Sea down to a maximum depth of 1,000 m. A total of 27 species and two form variants have been identified, including three new records for the Mediterranean. In addition, about 20, as yet undescribed, new morphospecies were found (mainly from the genera Epicalymma and Triconia) which need to be examined further. The total number of identified oncaeid species was similar in the Western and Eastern Basins, but for some cooccurring sibling species, the estimated numerical dominance changed. The deep-sea fauna of Oncaeidae, studied at selected depth layers between 400 m and the near-bottom layer at >4,200 m depth in the eastern Mediterranean (Levantine Sea), showed rather constant species numbers down to ∼3,000 m depth. In the near-bottom layers, the diversity of oncaeids declined and species of Epicalymma strongly increased in numerical importance. The taxonomic status of all oncaeid species recorded earlier in the Mediterranean Sea is evaluated: 19 out of the 46 known valid oncaeid species are insufficiently described, and most of the taxonomically unresolved species (13 species) have originally been described from this area (type locality). The deficiencies in the species identification of oncaeids cast into doubt the allegedly cosmopolitan distribution of some species, in particular those of Mediterranean origin. The existing identification problems even of well-described oncaeid species are exemplified for the Oncaea mediacomplex, including O. media Giesbrecht, O. scottodicarloi Heron & Bradford-Grieve, and O. waldemari Bersano & Boxshall, which are often erroneously identified as a single species (O. media). The inadequacy in the species identification of Oncaeidae, in particular those from the Atlantic and Mediterranean, is mainly due to the lack of reliable identification keys for Oncaeidae in warm-temperate and/or tropical seas. Future efforts should be directed to the construction of identification keys that can be updated according to the latest taxonomic findings, which can be used by the non-expert as well as by the specialist. The adequate consideration of the numerous, as yet undescribed, microcopepod species in the world oceans, in particular the Oncaeidae, is a challenge for the study of the structure and function of plankton communities as well as for global biodiversity estimates

30 years in the life of an active submarine volcano: A time-lapse bathymetry study of the Kick-‘em-Jenny Volcano, Lesser Antilles

Effective monitoring is an essential part of identifying and mitigating volcanic hazards. In the submarine environment this is more difficult than onshore because observations are typically limited to land-based seismic networks and infrequent shipboard surveys. Since the first recorded eruption in 1939, the Kick-‘em-Jenny (KeJ) volcano, located 8km off northern Grenada, has been the source of 13 episodes of T-phase signals. These distinctive seismic signals, often coincident with heightened body-wave seismicity, are interpreted as extrusive eruptions. They have occurred with a recurrence interval of around a decade, yet direct confirmation of volcanism has been rare. By conducting new bathymetric surveys in 2016 and 2017 and reprocessing 4 legacy datasets spanning 30 years we present a clearer picture of the development of KeJ through time. Processed grids with a cell size of 5m and vertical precision on the order of 1-4m allow us to correlate T-phase episodes with morphological changes at the volcano's edifice. In the time-period of observation 7.09x106 m3 of material has been added through constructive volcanism – yet 5 times this amount has been lost through landslides. Limited recent magma production suggests that KeJ may be susceptible to larger eruptions with longer repeat times than have occurred during the study interval, behavior more similar to sub-aerial volcanism in the arc than previously thought. T-phase signals at KeJ have a varied origin and are unlikely to be solely the result of extrusive submarine eruptions. Our results confirm the value of repeat swath bathymetry surveys in assessing submarine volcanic hazards

Species replacement dominates megabenthos beta diversity in a remote seamount setting

Seamounts are proposed to be hotspots of deep-sea biodiversity, a pattern potentially arising from increased productivity in a heterogeneous landscape leading to either high species co-existence or species turnover (beta diversity). However, studies on individual seamounts remain rare, hindering our understanding of the underlying causes of local changes in beta diversity. Here, we investigated processes behind beta diversity using ROV video, coupled with oceanographic and quantitative terrain parameters, over a depth gradient in Annan Seamount, Equatorial Atlantic. By applying recently developed beta diversity analyses, we identified ecologically unique sites and distinguished between two beta diversity processes: species replacement and changes in species richness. The total beta diversity was high with an index of 0.92 out of 1 and was dominated by species replacement (68%). Species replacement was affected by depth-related variables, including temperature and water mass in addition to the aspect and local elevation of the seabed. In contrast, changes in species richness component were affected only by the water mass. Water mass, along with substrate also affected differences in species abundance. This study identified, for the first time on seamount megabenthos, the different beta diversity components and drivers, which can contribute towards understanding and protecting regional deep-sea biodiversity

The genetic basis and evolution of red blood cell sickling in deer

Crescent-shaped red blood cells, the hallmark of sickle-cell disease, present a striking departure from the biconcave disc shape normally found in mammals. Characterized by increased mechanical fragility, sickled cells promote haemolytic anaemia and vaso-occlusions and contribute directly to disease in humans. Remarkably, a similar sickle-shaped morphology has been observed in erythrocytes from several deer species, without obvious pathological consequences. The genetic basis of erythrocyte sickling in deer, however, remains unknown. Here, we determine the sequences of human β-globin orthologues in 15 deer species and use protein structural modelling to identify a sickling mechanism distinct from the human disease, coordinated by a derived valine (E22V) that is unique to sickling deer. Evidence for long-term maintenance of a trans-species sickling/non-sickling polymorphism suggests that sickling in deer is adaptive. Our results have implications for understanding the ecological regimes and molecular architectures that have promoted convergent evolution of sickling erythrocytes across vertebrates

SNAGA, TEORIJA I PRAKSA (Kraft, Theorie und Praxis)

We have developed a global biogeographic classification of the mesopelagic zone to reflect the regional scales over which the ocean interior varies in terms of biodiversity and function. An integrated approach was necessary, as global gaps in information and variable sampling methods preclude strictly statistical approaches. A panel combining expertise in oceanography, geospatial mapping, and deep-sea biology convened to collate expert opinion on the distributional patterns of pelagic fauna relative to environmental proxies (temperature, salinity, and dissolved oxygen at mesopelagic depths). An iterative Delphi Method integrating additional biological and physical data was used to classify biogeographic ecoregions and to identify the location of ecoregion boundaries or inter-regions gradients. We define 33 global mesopelagic ecoregions. Of these, 20 are oceanic while 13 are ‘distant neritic.’ While each is driven by a complex of controlling factors, the putative primary driver of each ecoregion was identified. While work remains to be done to produce a comprehensive and robust mesopelagic biogeography (i.e., reflecting temporal variation), we believe that the classification set forth in this study will prove to be a useful and timely input to policy planning and management for conservation of deep-pelagic marine resources. In particular, it gives an indication of the spatial scale at which faunal communities are expected to be broadly similar in composition, and hence can inform application of ecosystem-based management approaches, marine spatial planning and the distribution and spacing of networks of representative protected areas

Remineralization of particulate organic carbon in an ocean oxygen minimum zone

This work was funded by a NERC standard grant NE/E01559X/1