Under ice shelf photographs from Drescher Inlet (Riiser Larsen Ice Shelf) taken by seal mounted cameras during expedition DRE2003

While modern sampling techniques, such as autonomous underwater vehicles, are increasing our knowledge of the fauna beneath Antarctic sea ice of only a few meters in depth, greater sampling difficulties mean that little is known about the marine life underneath Antarctic ice shelves over 100 m thick. In this study, we present underwater images showing the underside of an Antarctic ice shelf covered by aggregated invertebrate communities, most likely cnidarians and isopods. These images, taken at an average depth of 145 m, were obtained with a digital still camera system attached to Weddell seals Leptonychotes weddellii foraging just beneath the ice shelf. Our observations indicate that, similar to the sea floor, ice shelves serve as an important habitat for a remarkable amount of marine invertebrate fauna in Antarctica.

(Supplementary Table 1) Proportions of methane (C1) to ethane (C2) and the stable isotope composition of methane (d13CCH4) of gas and oil collected by gas bubble sampler during cruise M 114 in the southern Gulf of Mexico

Hydrocarbon seepage is a widespread process at the continental margins of the Gulf of Mexico. We used a multidisciplinary approach, including multibeam mapping and visual seafloor observations with different underwater vehicles to study the extent and character of complex hydrocarbon seepage in the Bay of Campeche, southern Gulf of Mexico. Our observations showed that seafloor asphalt deposits previously only known from the Chapopote Knoll also occur at numerous other knolls and ridges in water depths from 1230 to 3150 m. In particular the deeper sites (Chapopopte and Mictlan knolls) were characterized by asphalt deposits accompanied by extrusion of liquid oil in form of whips or sheets, and in some places (Tsanyao Yang, Mictlan, and Chapopote knolls) by gas emission and the presence of gas hydrates in addition. Molecular and stable carbon isotopic compositions of gaseous hydrocarbons suggest their primarily thermogenic origin. Relatively fresh asphalt structures were settled by chemosynthetic communities including bacterial mats and vestimentiferan tube worms, whereas older flows appeared largely inert and devoid of corals and anemones at the deep sites. The gas hydrates at Tsanyao Yang and Mictlan Knolls were covered by a 5-to-10 cm-thick reaction zone composed of authigenic carbonates, detritus, and microbial mats, and were densely colonized by 1-2 m-long tube worms, bivalves, snails, and shrimps. This study increased knowledge on the occurrences and dimensions of asphalt fields and associated gas hydrates at the Campeche Knolls. The extent of all discovered seepage structure areas indicates that emission of complex hydrocarbons is a widespread, thus important feature of the southern Gulf of Mexico.

K-Ag age of volcanites from underwater rises of the Sea of Okhotsk and the Sea of Japan

New K-Ar datings of Meso-Cenozoic volcanites from the Sea of Japan and the Sea of Okhotsk were obtained. They enabled to reason age of different volcanic complexes. Basalts from volcanic edifices of the Sea of Japan Basin were determined as Middle Miocene - Pliocene (13.1-4.5 Ma) in age, which correlates well with geological evolution of the Sea of Japan. New datings for basalts from the continental slope of the South Primorye (11.1 Ma) confirm their age being similar to volcanites from Neogene basalt plateaus of the South Primorye; they are very similar not only in age but also in mineral and chemical compositions. Datings for rocks from the andesite series of the Northern Yamato Rise (24.7, 21.5 Ma) show that they are coeval with volcanites of the trachyandesite complex; this allows to combine them into one Oligocene - Early Miocene complex. In the Sea of Okhotsk datings of volcanite samples from three complexes were obtained: Cretaceous, Paleogene, and Pliocene-Pleistocene. Cretaceous magmatic rocks make part of basements of large rises in the Sea of Okhotsk, and Paleogene and Pliocene - Pleistocene complexes illustrate stages of Cenozoic tectono-magmatic activation of the region.