ALBERT

Description: Acoustic basement lies at an average of between 6.0 and 6.5 sec two-way time below sea level in the southern Rockall Trough and northern Porcupine Abyssal Plain. The overlying sedimentary succession reaches maximum thicknesses of at least 4.0 sec, and can be divided by 3 regionally-developed seismic reflecting horizons, which are used as a framework to establish an acoustic stratigraphy for the area by selecting three “type” seismic sections. These reflectors are named, in ascending order, Shackleton, Charcot and Challenger. The area is crossed by E—W basement high structures, the Clare Lineament (which may be an easterly extension of the Charlie Gibbs Fracture Zone), that separates the Porcupine Abyssal Plain from the eastern part of southern Rockall Trough. Under the latter, the post-Shackleton acoustic sequence is thickened, as if dammed to the north of the Clare Lineament, whilst a further thickening, above reflector Charcot, occurs along a NE—SW line somewhat farther north into the southern Rockall Trough. This can also be related to shallow-lying acoustic basement features. Pre-Shackleton sediments overlie a very irregular basement topography. The acoustic characters of the various sediment packages are described and it is speculated that major changes in the sedimentary environments took place across reflectors Shackleton and Challenger, the latter probably establishing the modern bottom current circulation patterns. No ages can be unequivocally assigned to the main reflectors, but previously published data suggest a late Eocene—Oligocene age for Challenger. Possible lavas or sills are identified in the succession between reflectors Shackleton and Charcot.

Description: Published information appears to be lacking on the chemical composition and calorific content of Southern Ocean squid, which are important prey of sperm whales and many seabirds. Data for 17 species of squid (all but one from the Northern Hemisphere) are reviewed. lt is concluded that they have calorific contents distinctly lower than those of Antarctic fish and krill, mainly because of lower Iipid content. Because of the importance of such information to studies of energy transfer between trophic Ievels, it is recommended that data on the chemical composition and calorific content of Antarctic squid should be rapidly obtained.

Description: Cephalopod remains from 11 elephant seals (Mirounga leonina L.) collected at Signy Istand, South Orkney lslands, consist mainly of 68 upper beaks (mandibles) and 50 lower beaks. The lower beaks were sorted and measured. Eight species in six families are present. Gonarus antarcticus contributing 42%, an unidentified teuthoid (20% ), Moroteuthis knipovitchi ( 14%) and an octopod ( 10%) were the most numerous species. Estimates from beak lengths show that the octopus contributed 60% of the weight of cephalopod flesh represented by beaks in this collcction, while Gonatus antarcticus contributed 15% and Moroteuthis knipovitchi 10%. The species most frequently eaten are Gonatus antarcticus (44% of samples containing lower beaks) and the unidentified teuthoid (56% of samples).

Description: Stomach contents of eight Weddell seals killed on Deception lsland,South Shetland lslands, included unidentified fish, Euphausia superba, isopods,amphipods, pieces of blubber, bones, bits of algae, stones, parasitic worms and remains of cephalopods. The cephalopod remains included 349 lower beaks (mandibles), 383 upper beaks, eight 'crowns' of arms and nine buccal masses. The lower beaks, crowns and buccal masses were sorted into groups and identified as far as possible. Eight types of cephalopod of six families were identified. Three species each contributed almost a third of the total number of cephalopods in the diet; the squids Moroteuthis knipovitchi and ? Psychroteuthis glacialis contributed 31.3 and 28.7%, respectively, and an octopod, probably Pareledone, contributed 33.6%. Estimates from beak size show that Morotewhis knipovitchi contributed 48.5% and ? Pareledone 21.9% of the weight of flesh represented by beaks in the samples. While squids predominated in March and April, octopod dominated the cephalopod fraction in July. Octopods were also collected from the stomachs oft wo Weddell seals caught at Halley Bay.

Description: The habitals utilized by burrowing petrels at Bird lsland, South Gcorgia are described and the habitat modifications induced by the activities of fur seals and other seabirds summarised. The field methods for an investigation of the distribution and abundance of the nine species of burrow-dwelling petrels that breed on Bird lsland are described in detail. About 40% of the 200 hectares of ground suitable for burrow excavation was investigated using a system of grid squares each 3600 m² in area. ln each square, two randomly located circular quadrats of area 36 m² were studied. For each quadrat, aspect, slope, vegetation types and their cover, extent of fur seal influence and status of every burrow were recorded. Seven categories of both empty and occupied burrows were recognized and examination techniques (including use of tape-recorded calls to facilitate species identification) are described in detail. Over 5000 burrows were examined, with dove prion the most abundant species.

Description: Menaquinones (vitamin K2) were the only isoprenoid quinones found in the Actinomycetes tested. Thermomonospora strains belonging to the species T. alba, T. curvata and T. fusca contained very complex mixtures of menaquinones with nine, ten and eleven isoprene units. Hexa- and octahydrogenated menaquinones with ten isoprene units constituted the major components in T. alba, whereas, octahydrogenated menaquinones with ten isoprene units predominated in T. curvata and T. fusca. Substantial amounts of hitherto undescribed hexa-, octa-, and decahydrogenated menaquinones with eleven isoprene units were also present in the three species. The representative of the taxon Thermomonospora (Actinobifida) chromogena examined differed in possessing major amounts of tetrahydrogenated menaquinones with only nine isoprene units; a pattern also found in Saccharomonospora viridis, Actinomadura flexuosa and Micromonospora halophytica subsp. halophytica. The chemotaxonomic data and supporting results of numerical taxonomic studies suggest that Actinobifida chromogena may have been wrongly classified in the genus Thermomonospora.