Active mud volcanoes on the continental slope of the Canadian Beaufort Sea

The major geochemical characteristics of Red Sea brine are summarized for 11 brine-filled deeps located along the central graben axis between 19°N and 27°N. The major element composition of the different brine pools is mainly controlled by variable mixing situations of halite-saturated solution (evaporite dissolution) with Red Sea deep water. The brine chemistry is also influenced by hydrothermal water/rock interaction, whereas magmatic and sedimentary rock reactions can be distinguished by boron, lithium, and magnesium/calcium chemistry. Moreover, hydrocarbon chemistry (concentrations and δ 13 C data) of brine indicates variable injection of light hydrocarbons from organic source rocks and strong secondary (bacterial or thermogenic) degradation processes. A simple statistical cluster analysis approach was selected to look for similarities in brine chemistry and to classify the various brine pools, as the measured chemical brine compositions show remarkably strong concentration variations for some elements. The cluster analysis indicates two main classes of brine. Type I brine chemistry (Oceanographer and Kebrit Deeps) is controlled by evaporite dissolution and contributions from sediment alteration. The Type II brine (Suakin, Port Sudan, Erba, Albatross, Discovery, Atlantis II, Nereus, Shaban, and Conrad Deeps) is influenced by variable contributions from volcanic/ magmatic rock alteration. The chemical brine classification can be correlated with the sedimentary and tectonic setting of the related depressions. Type I brine-filled deeps are located slightly off-axis from the central Red Sea graben. A typical " collapse structure formation " which has been defined for the Kebrit Deep by evaluating seismic and geomorphological data probably corresponds to our Type I brine. Type II brine located in depressions in the northern Red Sea (i.e., Conrad and Shaban Deeps) could be correlated to " volcanic intrusion-/extrusion-related " deep formation. The chemical indications for hydrothermal influence on Conrad and Shaban Deep brine can be related to brines from the multi-deeps region in the central Red Sea, where volcanic/magmatic fluid/rock interaction is most obvious. The strongest hydrothermal influence is observed in Atlantis II brine (central multi-deeps region), which is also the hottest Red Sea brine body in 2011 (*68.2 °C)

Characteristics of the Mesophotic Megabenthic Assemblages of the Vercelli Seamount (North Tyrrhenian Sea)

The biodiversity of the megabenthic assemblages of the mesophotic zone of a Tyrrhenian seamount (Vercelli Seamount) is described using Remotely Operated Vehicle (ROV) video imaging from 100 m depth to the top of the mount around 61 m depth. This pinnacle hosts a rich coralligenous community characterized by three different assemblages: (i) the top shows a dense covering of the kelp Laminaria rodriguezii; (ii) the southern side biocoenosis is mainly dominated by the octocorals Paramuricea clavata and Eunicella cavolinii; while (iii) the northern side of the seamount assemblage is colonized by active filter-feeding organisms such as sponges (sometimes covering 100% of the surface) with numerous colonies of the ascidian Diazona violacea, and the polychaete Sabella pavonina. This study highlights, also for a Mediterranean seamount, the potential role of an isolated rocky peak penetrating the euphotic zone, to work as an aggregating structure, hosting abundant benthic communities dominated by suspension feeders, whose distribution may vary in accordance to the geomorphology of the area and the different local hydrodynamic conditions

Freshwater Seepage Into Sediments of the Shelf, Shelf Edge, and Continental Slope of the Canadian Beaufort Sea

Long‐term warming of the continental shelf of the Canadian Beaufort Sea caused by the transgression associated with the last deglaciation may be causing decomposition of relict offshore subsea permafrost and gas hydrates. To evaluate this possibility, pore waters from 118 sediment cores up to 7.3‐m long were taken on the shelf and slope and analyzed for chloride concentrations and δ180 and δD composition. We observed downcore decreases in pore waters Cl− concentration in sediments from all sites from the inner shelf (<20‐m water depth), from the shelf edge, from the outer slope (down to 1,000‐m water depths), and from localized shelf features such as midshelf pingo‐like features and inner shelf pockmarks. In contrast, pore water freshening is absent from all investigated cores of the Mackenzie Trough. Downcore pore waters Cl− concentration decreases indicate regional widespread freshwater seepage. Extrapolations to zero Cl− of pore water Cl− versus δ180 regression lines indicate that freshwaters in these environments carry different isotope signatures and thus are sourced from different reservoirs. These isotopic signatures indicate that freshening of shelf sediments pore waters is a result of downward infiltration of Mackenzie River water, freshening of shelf edge sediments is due to relict submarine permafrost degradation or gas hydrate decomposition under the shelf, and freshening of slope sediments is consistent with regional groundwater flow and submarine groundwater discharge as far as 150 km from shore. These results confirm ongoing decomposition of offshore permafrost and suggest extensive current groundwater discharge far from the coast

Science Priorities for Seamounts: Research Links to Conservation and Management

Seamounts shape the topography of all ocean basins and can be hotspots of biological activity in the deep sea. The Census of Marine Life on Seamounts (CenSeam) was a field program that examined seamounts as part of the global Census of Marine Life (CoML) initiative from 2005 to 2010. CenSeam progressed seamount science by collating historical data, collecting new data, undertaking regional and global analyses of seamount biodiversity, mapping species and habitat distributions, challenging established paradigms of seamount ecology, developing new hypotheses, and documenting the impacts of human activities on seamounts. However, because of the large number of seamounts globally, much about the structure, function and connectivity of seamount ecosystems remains unexplored and unknown. Continual, and potentially increasing, threats to seamount resources from fishing and seabed mining are creating a pressing demand for research to inform conservation and management strategies. To meet this need, intensive science effort in the following areas will be needed: 1) Improved physical and biological data; of particular importance is information on seamount location, physical characteristics (e.g. habitat heterogeneity and complexity), more complete and intensive biodiversity inventories, and increased understanding of seamount connectivity and faunal dispersal; 2) New human impact data; these shall encompass better studies on the effects of human activities on seamount ecosystems, as well as monitoring long-term changes in seamount assemblages following impacts (e.g. recovery); 3) Global data repositories; there is a pressing need for more comprehensive fisheries catch and effort data, especially on the high seas, and compilation or maintenance of geological and biodiversity databases that underpin regional and global analyses; 4) Application of support tools in a data-poor environment; conservation and management will have to increasingly rely on predictive modelling techniques, critical evaluation of environmental surrogates as faunal “proxies”, and ecological risk assessment

Anatomy of the La Jolla Submarine Canyon system; offshore southern California

An autonomous underwater vehicle (AUV) carrying a multibeam sonar and a chirp profiler was used to map sections of the seafloor within the La Jolla Canyon, offshore southern California, at sub-meter scales. Close-up observations and sampling were conducted during remotely operated vehicle (ROV) dives. Minisparker seismic-reflection profiles from a surface ship help to define the overall geometry of the La Jolla Canyon especially with respect to the pre-canyon host sediments.The floor of the axial channel is covered with unconsolidated sand similar to the sand on the shelf near the canyon head, lacks outcrops of the pre-canyon host strata, has an almost constant slope of 1.0° and is covered with trains of crescent shaped bedforms. The presence of modern plant material entombed within these sands confirms that the axial channel is presently active. The sand on the canyon floor liquefied during vibracore collection and flowed downslope, illustrating that the sediment filling the channel can easily fail even on this gentle slope.Data from the canyon walls help constrain the age of the canyon and extent of incision. Horizontal beds of moderately cohesive fine-grained sediments exposed on the steep canyon walls are consistently less than 1.232 million years old. The lateral continuity of seismic reflectors in minisparker profiles indicate that pre-canyon host strata extend uninterrupted from outside the canyon underneath some terraces within the canyon. Evidence of abandoned channels and point bar-like deposits are noticeably absent on the inside bend of channel meanders and in the subsurface of the terraces. While vibracores from the surface of terraces contain thin (&lt; 10 cm) turbidites, they are inferred to be part of a veneer of recent sediment covering pre-canyon host sediments that underpin the terraces. The combined use of state of the art seafloor mapping and exploration tools provides a uniquely detailed view of the morphology within an active submarine canyon

Cretaceous–Paleogene boundary exposed: Campeche Escarpment, Gulf of Mexico

We present the first multibeam bathymetric maps of the Campeche Escarpment, a Mesozoic carbonate platform in the Gulf of Mexico, which represents the closest Cretaceous–Paleogene (K-Pg) boundary outcrops to the Chicxulub impact structure. The impact of an extraterrestrial-body ~ 65 million years ago on top of this platform is implicated in the end of the Cretaceous mass extinction and caused the largest debris flow yet described on Earth, which is found across the floor of the Gulf of Mexico and the Caribbean Sea. The location of the K-Pg boundary has been identified in the escarpment face by combining the new multibeam data with existing information from boreholes. The boundary is represented by an abrupt change in gradient on the escarpment face. The morphology of the escarpment combined with seismic data reveals that a significant amount of material is missing from the face, which failed catastrophically due to seismic shaking produced by the impact. The escarpment face is inferred to be an important source for the extensive debris flows triggered by the impact, whose deposits are found throughout much of the Gulf of Mexico

Seafloor geomorphic manifestations of gas venting and shallow subbottom gas hydrate occurrences

High-resolution multibeam bathymetry data collected with an autonomous underwater vehicle (AUV) complemented by compressed high-intensity radar pulse (Chirp) profiles and remotely operated vehicle (ROV) observations and sediment sampling reveal a distinctive rough topography associated with seafloor gas venting and/or near-subsurface gas hydrate accumulations. The surveys provide 1 m bathymetric grids of deep-water gas venting sites along the best-known gas venting areas along the Pacific margin of North America, which is an unprecedented level of resolution. Patches of conspicuously rough seafloor that are tens of meters to hundreds of meters across and occur on larger seafloor topographic highs characterize seepage areas. Some patches are composed of multiple depressions that range from 1 to 100 m in diameter and are commonly up to 10 m deeper than the adjacent seafloor. Elevated mounds with relief of >10 m and fractured surfaces suggest that seafloor expansion also occurs. Ground truth observations show that these areas contain broken pavements of methane-derived authigenic carbonates with intervening topographic lows. Patterns seen in Chirp profiles, ROV observations, and core data suggest that the rough topography is produced by a combination of diagenetic alteration, focused erosion, and inflation of the seafloor. This characteristic texture allows previously unknown gas venting areas to be identified within these surveys. A conceptual model for the evolution of these features suggests that these morphologies develop slowly over protracted periods of slow seepage and shows the impact of gas venting and gas hydrate development on the seafloor morphology

Submarine Mass Transport Within Monterey Canyon: Benthic Disturbance Controls on the Distribution of Chemosynthetic Biological Communities

Documenting mass transport within Monterey Canyon and Fan has been a focus of remotely operated vehicle (ROV) observations, sampling, monitoring, and multibeam mapping studies. These efforts indicate that major mass transport events occur within upper Monterey Canyon (\u3c2 km water depths) with a sub-annual recurrence frequency. However, 14C-stratigraphies indicate that a sand carrying event has not penetrated through lower Monterey Canyon (\u3e2 km water depths) and onto Monterey Fan for ~100 years. Simultaneous efforts to document the distribution of benthic taxa observed in the video records from 668 ROV dives conducted by the Monterey Bay Aquarium Research Institute (MBARI) provide a uniquely detailed record of the occurrence of chemosynthetic biological communities (CBC). The combined results of these studies provide an understanding of the relationship between disturbance caused by episodic mass wasting events and the distribution of CBC. CBC are common within the canyon\u27s axis below ~2.5 km water depth, but have not been found within the canyon\u27s axis at depths shallower than 2 km. Moreover, CBC occur on the canyon walls at essentially any depth, primarily within young (~hundreds of years old) slump scars. The distribution of CBC provides evidence about the disturbance history of the seafloor. Major mass transport events will destroy communities that lie in their path. Erosion associated with major mass transport events can create environments to support CBC by exposing methane-bearing strata. This can happen as a result of slumping events on the sidewalls of the canyon or where major gravity flow events have excavated the base of canyon walls. Once fresh strata are exposed, geochemical conditions to support CBC will persist for a few centuries. Because CBC are composed of slow-growing and long-lived organisms, it will take decades for these communities to be established. Their existence indicates that environmental stability has occurred over a similar time scale

Genetic analysis of function and dysfunction in the central nervous system

The last decade has been witness to unprecedented advances in mammalian genetics. Techniques have been developed that allow the addition, deletion, or modification of any cloned gene. Recent developments also promise control over when and where mutations take place. These genetic tools have already been used successfully in the study of learning and memory. The results show that it is possible to derive mutants with informative molecular, cellular, neuroanatomical, and behavioral phenotypes. These findings have both complemented and expanded previous neuroanatomical and pharmacological studies, demonstrating that genetic techniques will be an important tool in developing explanations of learning and memory. Genetic studies of brain function must be developed from a solid behavioral foundation, since the design and interpretation of experiments is dependent on the clarity of the behavioral concepts under analysis. Beyond careful behavioral work, these studies must also include information about the neuroanatomy and physiology of the brain regions..