Kolgaosides A and B, two new triterpene glycosides from the Arctic deep water sea cucumber Kolga hyalina (Elasipodida: Elpidiidae).

Two novel triterpene holostane nonsulfated pentaosides, kolgaosides A (1) and B (2), and one known, holothurinoside B (3), were isolated from the Arctic sea cucumber Kolga hyalina, the second representative of the family Elpidiidae, order Elasipodida, from which triterpene glycosides have been obtained. The structures of 1 and 2 were elucidated using 1H and 13C NMR and 2D NMR procedures (HSQC, HMBC, COSY, ROESY, TOCSY) and HRESI mass-spectrometry. Kolgaosides A (1) and B (2) demonstrate low cytotoxic activity against the cells of the ascite form of mouse Ehrlich carcinoma and moderate hemolytic activity against mouse erythrocytes, despite the presence of hydroxy groups in the side chains of the aglycones. The glycosides of K. hyalina are similar to those of the Antarctic sea cucumber Rhipidothuria racowitzai Hèrouard, 1901 (=Achlionice violaescupidata) (Elasipodida: Elpidiidae); this may have chemotaxonomic significance.

An externally brooding acorn worm (Hemichordata, Enteropneusta, Torquaratoridae) from the Russian arctic.

A single specimen of a previously undescribed acorn worm in the family Torquaratoridae was trawled from a bottom depth of about 350 m in the Kara Sea (Russian Arctic). The new species is the shallowest of the exclusively deep-sea torquaratorids found to date, possibly an example of high-latitude emergence. On the basis of ribosomal DNA sequences and morphology, the worm is described here as the holotype of Coleodesmium karaensis n. gen., n. sp. It is most similar in overall body shape to the previously described enteropneust genus Allapasus, but is uniquely characterized by a tubular component of the proboscis skeleton ensheathing the collar nerve cord. Additionally, within the proboscis, the sparseness of the musculature of C. karaensis clearly distinguishes it from the much more muscular members of Allapasus. The holotype is a female bearing about a dozen embryos on the surface of her pharyngeal region, each recessed within a shallow depression in the dorsal epidermis. The embryos, ranging from late gastrula to an early stage of coelom formation, are a little more than 1 mm in diameter and surrounded by a thin membrane. Each embryo comprises an external ectoderm of monociliated cells (not arranged in obvious ciliated bands) and an internal endo-mesoderm; the blastopore is closed. In the most advanced embryos, the anterior coelom is starting to constrict off from the archenteron. Coleodesmium karaensis is the first enteropneust (and indeed the first hemichordate) found brooding embryos on the surface of the mother's body.

Export of algal biomass from the melting Arctic sea ice.

In the Arctic, under-ice primary production is limited to summer months and is restricted not only by ice thickness and snow cover but also by the stratification of the water column, which constrains nutrient supply for algal growth. Research Vessel Polarstern visited the ice-covered eastern-central basins between 82° to 89°N and 30° to 130°E in summer 2012, when Arctic sea ice declined to a record minimum. During this cruise, we observed a widespread deposition of ice algal biomass of on average 9 grams of carbon per square meter to the deep-sea floor of the central Arctic basins. Data from this cruise will contribute to assessing the effect of current climate change on Arctic productivity, biodiversity, and ecological function.

Does presence of a mid-ocean ridge enhance biomass and biodiversity?

In contrast to generally sparse biological communities in open-ocean settings, seamounts and ridges are perceived as areas of elevated productivity and biodiversity capable of supporting commercial fisheries. We investigated the origin of this apparent biological enhancement over a segment of the North Mid-Atlantic Ridge (MAR) using sonar, corers, trawls, traps, and a remotely operated vehicle to survey habitat, biomass, and biodiversity. Satellite remote sensing provided information on flow patterns, thermal fronts, and primary production, while sediment traps measured export flux during 2007-2010. The MAR, 3,704,404 km(2) in area, accounts for 44.7% lower bathyal habitat (800-3500 m depth) in the North Atlantic and is dominated by fine soft sediment substrate (95% of area) on a series of flat terraces with intervening slopes either side of the ridge axis contributing to habitat heterogeneity. The MAR fauna comprises mainly species known from continental margins with no evidence of greater biodiversity. Primary production and export flux over the MAR were not enhanced compared with a nearby reference station over the Porcupine Abyssal Plain. Biomasses of benthic macrofauna and megafauna were similar to global averages at the same depths totalling an estimated 258.9 kt C over the entire lower bathyal north MAR. A hypothetical flat plain at 3500 m depth in place of the MAR would contain 85.6 kt C, implying an increase of 173.3 kt C attributable to the presence of the Ridge. This is approximately equal to 167 kt C of estimated pelagic biomass displaced by the volume of the MAR. There is no enhancement of biological productivity over the MAR; oceanic bathypelagic species are replaced by benthic fauna otherwise unable to survive in the mid ocean. We propose that globally sea floor elevation has no effect on deep sea biomass; pelagic plus benthic biomass is constant within a given surface productivity regime.