Mass estimates and morphometric meassurements of Discoaster species and Sphenolithus from Ceara Rise ODP Site 927

Mass estimates for Late Miocene and Pliocene (8.6-3.25 Ma) Discoaster species and Sphenolithus are determined using samples of the equatorial Atlantic (Ceara Rise: ODP Site 927). Based on morphometric measurements, 3D computer models were created for 11 Discoaster species and their volumes calculated. From these, shape factors (ks) were derived to allow calculation of mass for different-sized discoasters and Sphenolithus abies. The mass estimates were then used to calculate the contribution of nannofossils to the total nannofossil carbonate. The discoaster contribution ranges from 10% to 40%, with a decreasing trend through the investigated interval. However, our estimates of total nannofossil carbonate from size-corrected abundance data are consistently 30-50% lower than estimates from grain-size measurement; this suggests that data based on mass estimates need to be interpreted with caution.

At surface behaviour of adult male southern elephant seals from King George Island from expedition JUB2000

Adult male southern elephant seals instrumented in 2000 on King George Island (n = 13), travelled both to the north (doi:10.1594/PANGAEA.231580, doi:10.1594/PANGAEA.231585) and to the east (doi:10.1594/PANGAEA.231571, doi:10.1594/PANGAEA.231579, doi:10.1594/PANGAEA.261708, doi:10.1594/PANGAEA.261709, doi:10.1594/PANGAEA.261710, doi:10.1594/PANGAEA.261711) of the Antarctic Peninsula. Five males (doi:10.1594/PANGAEA.231571, doi:10.1594/PANGAEA.231579, doi:10.1594/PANGAEA.231580, doi:10.1594/PANGAEA.261710, doi:10.1594/PANGAEA.231585) remained within 500 km of the island and focusing movements in the Bransfield Strait and around the Antarctic Peninsula. Sea-surface temperatures encountered by these animals showed little variation and they seemed to move about irrespective of sea ice cover, but frequented areas of shallow bathymetry. Three males (doi:10.1594/PANGAEA.261708, doi:10.1594/PANGAEA.261709, doi:10.1594/PANGAEA.261711) moved as far as 75°S to the east of the peninsula, into the Weddell Sea, with maximum distances of more than 1500 km from King George Island. They travelled into the Weddell Sea along the western continental shelf break until they reached the region of the Filchner Trough outflow. Here the bathymetry consists of canyons and ridges which support the intensive mixing between the warm saline waters of the Weddell Gyre and the very cold outflow waters with Ice Shelf water ingredients at the Antarctic Slope Front. Another five data sets were shorter then 40 days, and excluded from analyses (doi:10.1594/PANGAEA.231568, doi:10.1594/PANGAEA.231576, doi:10.1594/PANGAEA.231572, doi:10.1594/PANGAEA.231577, doi:10.1594/PANGAEA.264710). A computer animation was developed to visualize the animal movements in relation to the extent and concentration of sea ice (doi:10.1594/PANGAEA.509404). The need for re-instrumentation of adult males from King George Island is highlighted to investigate whether males continue to travel to similar areas and to obtain higher resolution data.

At surface behaviour of juvenile and female southern elephant seals from King George Island from expeditions JUB1996 and JUB1997

Between December 1996 and February 1997, weaned pups and postmoult female southern elephant seals (Mirounga leonina) were fitted with satellite transmitters at King George Island (South Shetlands). Of the nine adult females tracked for more than two months, three stayed in a localized area between the South Shetlands and the South Orkneys. The other six females travelled southwest along the coast of the Antarctic Peninsula up to the Bellingshausen Sea. Two of them then moved far northeast and hauled out on South Georgia in October. One female was last located north of the South Shetlands in March 1998. In total, eight females were again sighted on King George Island and six of the transmitters removed. The tracks of the weaners contrasted with those of the adults. In January, five juveniles left King George Island for the Pacific sector ranging about four weeks in the open sea west of the De Gerlache Seamounts. Three of them returned to the tip of the Antarctic Peninsula in June, of which one was last located on the Patagonian Shelf in November 1997. A computer animation was developed to visualize the animal movements in relation to the extent and concentration of sea ice. The juveniles avoided sea ice while the adults did not. The latter displayed behavioural differences in using the pack ice habitat during winter. Some females adjusted their movement patterns to the pulsating sea ice fringe in far-distant foraging areas while others ranged in closed pack ice of up to 100 %. The feeding grounds of adult female elephant seals are more closely associated with the pack ice zone than previously assumed.

3D models created from ROV videos and their corresponding subtransect dimensions

Underwater video transects have become a common tool for quantitative analysis of the seafloor. However a major difficulty remains in the accurate determination of the area surveyed as underwater navigation can be unreliable and image scaling does not always compensate for distortions due to perspective and topography. Depending on the camera set-up and available instruments, different methods of surface measurement are applied, which make it difficult to compare data obtained by different vehicles. 3-D modelling of the seafloor based on 2-D video data and a reference scale can be used to compute subtransect dimensions. Focussing on the length of the subtransect, the data obtained from 3-D models created with the software PhotoModeler Scanner are compared with those determined from underwater acoustic positioning (ultra short baseline, USBL) and bottom tracking (Doppler velocity log, DVL). 3-D model building and scaling was successfully conducted on all three tested set-ups and the distortion of the reference scales due to substrate roughness was identified as the main source of imprecision. Acoustic positioning was generally inaccurate and bottom tracking unreliable on rough terrain. Subtransect lengths assessed with PhotoModeler were on average 20% longer than those derived from acoustic positioning due to the higher spatial resolution and the inclusion of slope. On a high relief wall bottom tracking and 3-D modelling yielded similar results. At present, 3-D modelling is the most powerful, albeit the most time-consuming, method for accurate determination of video subtransect dimensions.