Gut filling, gut content and fatty acid composition of demersal fish species sampled during POLARSTERN cruise ANT-XXIV/2

The gut contents and fatty acid composition of 49 fish belonging to five Antarctic demersal families (Nototheniidae, Macrouridae, Channichtyidae, Bathydraconidae and Artedidraconidae) sampled at two stations at the Southern Ocean shelf and deep sea (600 and 2150 m) were analysed in order to identify their main food resource by linking trophic biomarkers with the dietary items found in the fish guts. Main food items of most fish analysed were amphipod crustaceans (e.g. in 63% of Trematomus bernachii guts) and polychaetes (e.g. in 80% of Bathydraco sp. guts), but other food items including fish, other crustaceans and gastropods were also ingested. The most prominent fatty acids found were 20:5(n-3), 16:0, 22:6(n-3) and 18:1(n-9). The results of gut content and fatty acid analyses indicate that all fish except the Channichthyidae share similar food resources irrespective of their depth distribution, i.e. benthic amphipods and polychaetes. A difference of the dietary spectrum can be observed with ontogenetic phases rather than between species, as high values of typical calanoid copepod marker fatty acids as 22:1(n-11) indicate that younger (smaller) specimens include more zooplankton in their diet.

Distribution of foraminiferal fauna from ODP Hole 122-762C (Table 1)

Planktonic foraminiferal diversity, equitability and biostratigraphic analysis of samples from Ocean Drilling Program (ODP) Leg 122, Hole 762C show that in general, cool water conditions prevailed during the latest Campanian-Maastrichtian in the eastern Indian Ocean. This is indicated by planktonic foraminiferal assemblages characterized by low species diversity and equitability with abundant rugoglobigerinids and heterohelicids. Archaeoglobigerinids, globigerinelloids, hedbergellids, and long-ranging double-keeled globotruncanids are also present in varying abundance but single-keeled forms occur rarely and sporadically. Identification of the stage and zonal boundaries for the studied geologic interval have been achieved through biostratigraphic analyses of closely spaced samples. Three planktonic foraminiferal biozones were identified, namely; in stratigraphic order, the Heterohelix rajagopalani, Contusotruncana contusa and Abathomphalus mayaroensis Zones. In Hole 762C, a Transitional Realm with Austral influences is defined for the latest Campanian to Maastrichtian, as shown by the high relative abundance of fauna characteristic of Transitional and Austral Realms. Austral endemic species such as Archaeoglobigerina australis Huber and Hedbergella sliteri Huber were found in the samples studied but Globigerinelloides impensus Sliter andA rchaeoglobigerina mateola Huber are conspicuously absent. From the latest Campanian to middle Maastrichtian, cooler parts of the Transitional Realm prevailed. A slight warming trend is assumed towards the end of the middle Maastrichtian because the faunas contain more species indicative of warm water conditions. The late Maastrichtian also appears to have been warmer than the latest Campanian-middle Maastrichtian. This conclusion is based on the high diversity and equitability values and recognition of some thermophilic taxa. A Tethyan influence is inferred for the latest Maastrichtian on the basis of an increase of planktonic foraminiferal species diversity and occurrences of several keeled taxa.

Physical oceanography, sea-bed photographs and videos of benthos from the Weddell Sea taken with remote operated vehicle CHEROKEE during POLARSTERN cruise ANT-XXIII/8

The marine ecosystem on the eastern shelf of the Antarctic Peninsula was surveyed 5 and 12 years after the climate-induced collapse of the Larsen A and B ice shelves. An impoverished benthic fauna was discovered, that included deep-sea species presumed to be remnants from ice-covered conditions. The current structure of various ecosystem components appears to result from extremely different response rates to the change from an oligotrophic sub-ice-shelf ecosystem to a productive shelf ecosystem. Meiobenthic communities remained impoverished only inside the embayments. On local scales, macro- and mega-epibenthic diversity was generally low, with pioneer species and typical Antarctic megabenthic shelf species interspersed. Antarctic Minke whales and seals utilised the Larsen A/B area to feed on presumably newly established krill and pelagic fish biomass. Ecosystem impacts also extended well beyond the zone of ice-shelf collapse, with areas of high benthic disturbance resulting from scour by icebergs discharged from the Larsen embayments.

Composition of sediments samples spanning the Cretaceous-Tertiary boundary at ODP Site 207-1259

Ocean Drilling Program (ODP) Leg 207, on the Demerara Rise in the western tropical North Atlantic, recovered multiple Cretaceous-Paleogene boundary sections containing an ejecta layer. Sedimentological, geochemical, and paleontological changes across the boundary closely match patterns expected for a mass extinction caused by a single impact. A normally graded, ~2-cm-thick bed of spherules that is interpreted as a primary air-fall deposit of impact ejecta occurs between sediments of the highest Cretaceous Plummerita hantkeninoides foraminiferal zone and the lowest Paleogene P0 foraminiferal zone. There are no other spherule layers in the section. In addition to extinction of Cretaceous taxa, foraminiferal abundance drops from abundant to rare across the boundary. Ir concentrations reach a maximum of ~1.5 ppb at the top of the spherule bed, and the Ir anomaly is associated with enrichment in other siderophile elements. We attribute the unusually well-preserved and relatively simple stratigraphy to the fact that Demerara Rise was close enough (~4500 km) to the Chicxulub impact site to receive ~2 cm of ejecta, yet was far enough away (and perhaps sheltered by the curve of northern South America) to have been relatively unaffected by impact-induced waves.