Man's Impact on the Barents Sea

The Barents Sea ecosystem is a polar system with high biological production. Production takes place during a short season, mainly along the ice margin. As biological production is very limited in both space and time, the ecosystem is vulnerable to the influence of human activity. Fishing activity represents the most significant environmental load by man on the Barents Sea. In recent years offshore oil and gas exploration activity has increased, resulting in environmental problems as well as conflicts with fishing operations. Heavy metals and organic contaminants of man-made origin have been observed in both sediments and organisms at different trophic levels. Both long-range atmospheric transport and transport by ocean currents are important. Organic contaminants accumulate mainly in the body fat of the organisms; northern ecosystems are therefore especially vulnerable because fat has much greater ecological importance in such systems than in more southerly ecosystems. In recent years there has been public concern in both Norway and Russia over the possibility of radioactive pollution. Nuclear power plants, nuclear vessels and weapons are present in the area and produce radioactive wastes. Reports of wastes have influenced public opinion in many countries. The Barents Sea is strongly influenced by ocean climate variations. Global climate models forecast that the most elevated ocean temperatures due to possible greenhouse effects will probably occur in polar regions.Key words: Barents Sea, fishing, offshore oil activity, organic contaminants, radioactivityL'écosystème de la mer de Barents est un système polaire ayant une haute productivité biologique. La production a lieu au cours d'une brève saison, principalement le long de la marge glaciaire. Étant donné que la production biologique est très limitée à la fois dans le temps et dans l'espace, l'écosystème est très sensible à l'activité humaine. La pêche constitue le plus gros fardeau environnemental que fait peser l'être humain sur la mer de Barents. Au cours des dernières années, l'exploration pétrolière et gazière au large a augmenté, donnant lieu à des problèmes écologiques ainsi qu'à des conflits avec l'industrie de la pêche. On a trouvé des métaux lourds et des contaminants organiques anthropiques dans les sédiments comme dans les organismes, et ce, à différents niveaux trophiques. Le transport atmosphérique de longue portée et le transport par les courants océaniques sont importants. Les contaminants organiques s'accumulent surtout dans le tissu adipeux des organismes; les écosystèmes nordiques sont donc particulièrement vulnérables car le gras a beaucoup plus d'importance écologique dans ces systèmes que dans des écosystèmes localisés plus au sud. Durant les dernières années, en Norvège comme en Russie, le public s'est dit concerné par une éventuelle pollution radioactive. Centrales, vaisseaux et armes nucléaires sont présents dans la région et produisent des déchets radioactifs. Des rapports sur ces déchets ont influencé l'opinion publique dans de nombreux pays. La mer de Barents est fortement influencée par les variations du climat océanique. Des modèles climatiques planétaires prédisent que c'est probablement dans les régions polaires que se produiront les plus fortes hausses de températures océaniques dues à l'effet de serre éventuel.Mots clés: mer de Barents, pêche, activité pétrolière au large, contaminants organiques, radioactivit&eacute

Macroalgal morphogenesis induced by waterborne compounds and bacteria in coastal seawater

Axenic gametes of the marine green macroalga Ulva mutabilis Foyn (Ria Formosa, locus typicus) exhibit abnormal development into slow-growing callus-like colonies with aberrant cell walls. Under laboratory conditions, it was previously demonstrated that all defects in growth and thallus development can be completely abolished when axenic gametes are inoculated with a combination of two specific bacterial strains originally identified as Roseo-bacter sp. strain MS2 and Cytophaga sp. strain MS6. These bacteria release diffusible morphogenetic compounds (= morphogens), which act similar to cytokinin and auxin. To investigate the ecological relevance of the waterborne bacterial morphogens, seawater samples were collected in the Ria Formosa lagoon (Algarve, Southern Portugal) at 20 sampling sites and tidal pools to assess their morphogenetic effects on the axenic gametes of U. mutabilis. Specifically the survey revealed that sterile-filtered seawater samples can completely recover growth and morphogenesis of U. mutabilis under axenic conditions. Morphogenetic activities of free-living and epiphytic bacteria isolated from the locally very abundant Ulva species (i.e., U. rigida) were screened using a multiwell-based testing system. The most represented genera isolated from U. rigida were Alteromonas, Pseudoalteromonas and Sulfitobacter followed by Psychrobacter and Polaribacter. Several naturally occurring bacterial species could emulate MS2 activity (= induction of cell divisions) regardless of taxonomic affiliation, whereas the MS6 activity (= induction of cell differentiation and cell wall formation) was species-specific and is probably a feature of difficult-to-culture bacteria. Interestingly, isolated bacteroidetes such as Algoriphagus sp. and Polaribacter sp. could individually trigger complete Ulva morphogenesis and thus provide a novel mode of action for bacterial-induced algal development. This study also highlights that the accumulation of algal growth factors in a shallow water body separated from the open ocean by barrier islands might have strong implications to, for example, the wide usage of natural coastal seawater in algal (land based) aquacultures of Ulva

Cryptic Disc Structures Resembling Ediacaran Discoidal Fossils from the Lower Silurian Hellefjord Schist, Arctic Norway

The Hellefjord Schist, a volcaniclastic psammite-pelite formation in the Caledonides of Arctic Norway contains discoidal impressions and apparent tube casts that share morphological and taphonomic similarities to Neoproterozoic stem-holdfast forms. U-Pb zircon geochronology on the host metasediment indicates it was deposited between 437 ± 2 and 439 ± 3 Ma, but also indicates that an inferred basal conglomerate to this formation must be part of an older stratigraphic element, as it is cross-cut by a 546 ± 4 Ma pegmatite. These results confirm that the Hellefjord Schist is separated from underlying older Proterozoic rocks by a thrust. It has previously been argued that the Cambrian Substrate Revolution destroyed the ecological niches that the Neoproterozoic frond-holdfasts organisms occupied. However, the discovery of these fossils in Silurian rocks demonstrates that the environment and substrate must have been similar enough to Neoproterozoic settings that frond-holdfast bodyplans were still ecologically viable some hundred million years later