ALBERT

Description: A study of the echo peak amplitudes from known nodule areas is initiated to observe the acoustic response for varying nodule abundances and number densities. A statistical study of the peak amplitudes from different nodule areas confirms that the coefficient of variation is the highest for medium nodule abundance and number density. Echo fluctuation study based on the Rician probability density function (PDF) establishes that the non‐nodule sediment bottom contributes to less scattering, i.e., it is a microtopographic type, whereas scattering is dominant in the nodule‐bearing areas. The spectral studies are conducted on depth data of different areas. This study ensures that the signal scattering in the nodule bottom area is due to the nodules lying on the seabed rather than the large / small‐scale topographic variations. The study based on Poisson PDF for nodule area confirms this fact again. Agreement between the nodule distribution and the Poisson distribution parameter is clearly seen. Such a relation is not observed in the case of Rician density functions.

Description: Plastic debris accumulates in the marine environment following its use in agricultural, industrial and social activities. Its ultimate fate is accomodation in sediments where it may persist for times up to centuries or longer. There appears to be an increasing flux of materials with time and an increased areal coverage of the benthos. Impacts upon bottom organisms can take many forms. Systematic monitoring tactics for the extent of seafloor coverage by plastics are yet to be incorporated into national programs.

Description: Newly hatched Baltic cod Gadus morhua larvae are typically found at depths 〉60 m. This is a region of low light and prey availability, hence generating the hypothesis that larvae have to migrate from hatching depth to the surface layer to avoid starvation and improve their nutritional condition. To test this hypothesis, Baltic cod larvae were sampled during the spawning seasons of 1994 and 1995 with depth-resolving multiple opening/closing nets. Each larva was aged by otolith readings and its RNA/DNA ratio was determined as a measure of nutritional condition. The RNA/DNA ratios of these larvae aged 2-25 days (median 10 days) ranged from 0.4 to 6.2, corresponding to levels exhibited by starving and fast-growing larvae in laboratory calibration studies (starvation, protein growth rate, Gpi= -12.2% day−1; fastgrowing larvae, Gpi=14.1%day−1) respectively. Seventy per cent of the field caught larvae had RNA/DNA ratios between the mean values found for starving and fed laboratory larvae. Only larvae aged 8-11 days had higher mean RNA/DNA ratios above 45 m than below (t-test, P〈0.05). However, the instantaneous protein growth rates were significantly higher for all larval age groups in the surface layers (t-test, P〈0.05). Starving larvae were found in all depths sampled (10-85 m), whereas growing larvae (positive Gpi) were restricted to samples taken shallower than 45 m. These superior growth rates above 45 m corroborate the hypothesis and imply that migration to the shallow water layers is a prerequisite for good nutritional condition, growth and survival of Baltic cod larvae. The frequent occurrence of cod larvae older than 8 days in the deep water in poor condition suggests that a proportion of the larvae will die from Starvation in the deep layers of the Baltic Sea.

Description: A description of egg masses from Gonatus frabricii (Lichtenstein) caught with pelagic trawl in the Norwegian Sea is given. The eggs were kept together in a single layer between two mucous membranes, and the pieces collected appeared to be fragments of more extensive structures torn apart by wear from the sampling gear. No embryos were observed in the eggs, and none of the eggs showed any staining for five enzyme systems analyzed by isoelectric focusing. Either the eggs were caught shortly after spawning and fertilization, or the lack of embryonic tissue reflects the fact that most of the eggs were caught in water colder than 0°C. The development rate at this temperature is expected to be very slow.

Description: The South Tasman Rise is a large submarine plateau of continental origin, located south of Tasmania. In the light of satellite‐derived gravity data and shipboard swath‐bathymetry and magnetic data collected in 1994 in the South Tasman Rise region, this paper re‐examines the sea‐floor spreading history of the surrounding ocean basins (northeastern Australian‐Antarctic Basin and southwestern Tasman Sea). This information is synthesised in seven plate tectonic reconstructions of the South Tasman Rise region from the mid‐Cretaceous (95 Ma) to the Early Oligocene (34 Ma). Our interpretation and model confirm that the South Tasman Rise is composed of two distinct terranes. A western domain, limited to the west by a transform margin along the Tasman Fracture Zone and to the east by a N170°E oriented boundary at 146.5°E, was initially attached to Antarctica. The western terrane rifted away from Antarctica in the Late Paleocene/Early Eocene and underwent severe wrench deformation as the Antarctic plate moved southward relative to the Australian plate. Shear motion continued to shape the Tasman Fracture Zone transform margin until the Early Miocene (chron 6B, 23 Ma) after which the Southeast Indian Ridge axis cleared from the western edge of the South Tasman Rise. An eastern domain limited to the east by a boundary at 146.5°E, rifted off from Tasmania and the East Tasman Plateau. After an initial phase of stretching between Tasmania, the East Tasman Plateau and the Lord Howe Rise that lasted until the mid‐Cretaceous, sea‐floor spreading in the Tasman Sea started in the Late Cretaceous (chron 34y) north of the East Tasman Plateau. Seismic, magnetic and gravity profiles between the eastern South Tasman Rise and the East Tasman Plateau suggest that sea‐floor spreading began between the two microcontinental blocks in the Late Cretaceous (ca chron 33y) and failed shortly after (chron 30y).

Description: The female of the harpacticoid Cholidya polypi Farran, 1914, is redescribed and the male is described for the first time. This copepod parasite of octopuses, reported previously only from Benthoctopus (= Polypus) ergasticus off Ireland, is here documented from the North Atlantic east of Florida on Tetracheledone spinicirrus and off North Carolina and New Jersey on Bathypolypus anticus, and from the northeastern Pacific west of Oregon and Washington on Graneledone pacifica and off central California on Graneledone spp.

Description: Statolith morphology of the giant squid Architeuthis sp. from southern African waters is illustrated. The most characteristic features are identified, particularly the wing shape and position, which are described for the first time.

Description: The morphology of a preserved octopod is significantly affected by the condition of the animal at the time of fixation, whether live or dead. When unknown, this condition can be assessed by examining the degree of contraction of the radula support muscle. Specimens fixed post‐mortem have a relaxed radula support muscle. This muscle is contracted in specimens plunged into preservatives alive. The degree of contraction of this radula support muscle facilitates identification of both fixation‐induced and fixation‐independent character states in octopod systematics.

Description: An uncritical compilation of New Zealand Mollusca by Spencer & Willan in 1996 cites 90 species of cephalopod as recorded from New Zealand waters (excluding the Kermadec Islands) to 31 December 1993. Seventeen of these 90 species are octopods and the status of five is in need of immediate revision. Pareledone sp. and Octopus sp. have since been transferred to the genera Graneledone and Benthoctopus, respectively, although both species await description. Haliphron atlanticus Steenstrup, 1860 (as Alloposus mollis Verrill, 1880), Ocythoe tuberculata Rafinesque, 1814, and Octopus dofleini (Wulker, 1910) are cited as occurring within New Zealand waters solely on the basis of identification of beaks or tissue remains from gut contents of longdistance foraging marine predators. The appropriateness of including these three species in the New Zealand fauna is evaluated in the light of thorough examination of extensive cephalopod collections from New Zealand waters.

Description: A total of 1,014 measures of sediment shear strengths were measured by means of miniature vane shear and fall cone tests on five gravity cores collected in Eckernfo‐erde Bay, Baltic Sea. Paired t test was used to compare the shear strengths measured by the two methods. It was found that fall cone strength calculated with Wood's K60value (0.29) overestimates the vane shear strength by 0.15 kPa (a = 0.001) and the sample mean of the fall cone strength is 4.1% higher than the mean of the vane shear strength. However, fall cone strength calculated with Hansbo's K60 value (0.24) underestimates the vane shear strength by 0.88 kPa (a = 0.001), and the sample mean of the fall cone strength is 13.8% less than the mean of the vane shear strength. Both calculated fall cone strengths are significantly different from the vane shear strength, with a p value of less than 0.001. Regression analysis of the Echernfoerde Bay data indicates that a new K60 value is 0.275 with a confidence interval (a = 0.01) from 0.2704 to 0.2786. Paired t test shows that there is no significant difference between miniature vane shear and fall cone tests for these samples if the fall cone strength is calculated with K60 = 0.275.