(Table 1) Comparison of dive duration and speed of Adélie penguins (Pygoscelis adeliae) equipped with internal and external devices

Bio-logging studies suffer from the lack of real controls. However, it is still possible to compare indirect parameters between control and equipped animals to assess the level of global disturbance due to instrumentation. In addition, it is also possible to compare the behaviour of free-ranging animals between individuals equipped with different techniques or instruments to determine the less deleterious approach. We instrumented Adelie Penguins (Pygoscelis adeliae) with internal or external time-depth recorders and monitored them in parallel with a control group during the first foraging trip following instrumentation. Foraging trip duration was significantly longer in the internally-equipped group. This difference was due to a larger number of dives, reflecting a lower foraging ability or a higher food demand, and longer periods of recovery at the surface. These longer recovery periods were likely to be due to a reduced efficiency to ventilate at the surface, probably because the implanted devices pressurised adjacent organs such as air sacs. Moreover, descent and ascent rates were slightly lower in externally-equipped penguins, presumably because external instrumentation increased the bird drag. Looking at our results, implantation appears more disadvantageous - at least for short-term deployment - than external equipment in Adelie Penguins, while this method has been described to induce no negative effects in long-term studies. This underlines the need to control for potential effects due to methodological aspects in any study using data loggers in free-ranging animals, to minimise disturbance and collect reliable data.

(Table 1) Characteristics of breeding male Adélie penguins (Pygoscelis adeliae) treated with varying degrees of corticosterone, Adélie land, Antarctica

Breeding individuals enter an emergency life-history stage when their body reserves reach a minimum threshold. Consequently, they redirect current activity toward survival, leading to egg abandonment in birds. Corticosterone (CORT) is known to promote this stage. How and to what extent CORT triggers egg abandonment when breeding is associated with prolonged fasting, however, requires further investigation. We manipulated free-living male Adelie penguins with CORT-pellets before their laying period. We then examined their behavioral response with respect to nest abandonment in parallel with their prolactin levels (regulating parental care), and the subsequent effects of treatment on breeding success in relieved birds. Exogenous CORT triggered nest abandonment in 60% of the treated penguins -14 days after treatment and induced a concomitant decline in prolactin levels. Interestingly, prolactin levels in treated penguins that did not abandon their nest were higher at the point of implantation and also after being relieved by females, when compared with abandoning penguins. Among successful birds, the treatment did not affect the number of chicks, nor the brood mass. Our results show the involvement of CORT in the decision-making process regarding egg abandonment in Adelie penguins when incubation is associated with a natural long fast. However, we suggest that CORT alone is not sufficient to trigger nest abandonment but that 1) prolactin levels need to reach a low threshold value, and 2) a rise in proteolysis (i.e. utilization of protein as main energy substrate) seems also to be required.

Geochemistry of Atlantis Massif crust

The Atlantis Massif (Mid-Atlantic Ridge, 30°N) is an oceanic core complex marked by distinct variations in crustal architecture, deformation and metamorphism over distances of at least 5 km. We report Sr and Nd isotope data and Rare Earth Element (REE) concentrations of gabbroic and ultramafic rocks drilled at the central dome (IODP Hole 1309D) and recovered by submersible from the southern ridge of the massif that underlie the peridotite-hosted Lost City Hydrothermal Field. Systematic variations between the two areas document variations in seawater penetration and degree of fluid-rock interaction during uplift and emplacement of the massif and hydrothermal activity associated with the formation of Lost City. Homogeneous Sr and Nd isotope compositions of the gabbroic rocks from the two areas (87Sr/86Sr: 0.70261-0.70429 and epsilon-Nd: +9.1 to +12.1) indicate an origin from a depleted mantle. At the central dome, serpentinized peridotites are rare and show elevated seawater-like Sr isotope compositions related to serpentinization at shallow crustal levels, whereas unaltered mantle isotopic compositions preserved in the gabbroic rocks attest to limited seawater interaction at depth. This portion of the massif remained relatively unaffected by Lost City hydrothermal activity. In contrast, pervasive alteration and seawater-like Sr and Nd isotope compositions of serpentinites at the southern wall (87Sr/86Sr: 0.70885-0.70918; epsilon-Nd: -4.7 to +11.3) indicate very high fluid-rock ratios (~20 and up to 10**6) and enhanced fluid fluxes during hydrothermal circulation. Our studies show that Nd isotopes are most sensitive to high fluid fluxes and are thus an important geochemical tracer for quantification of water-rock ratios in hydrothermal systems. Our results suggest that high fluxes and long-lived serpentinization processes may be critical to the formation of Lost City-type systems and that normal faulting and mass wasting in the south facilitate seawater penetration necessary to sustain hydrothermal activity.

(Table 3) Age determination of sediment cores from the SW Pacific Ocean

Eight- to ten-point depth profiles (from 1200 to 4800 m water depth) of oxygen and carbon isotopic values derived from benthic foraminifera, averaged over selected times in the past 160 ka, are presented. The data are from 10 sediment cores off eastern New Zealand, mainly North Chatham Rise. This lies under the Deep Western Boundary Current in the Southwest Pacific and is the main point of entry for several water masses into the Pacific Ocean. The benthic isotopic profiles are related to the structure of water masses at present and inferred for the past. These have retained a constant structure of Lower Circumpolar Deep Water-Upper Circumpolar Deep Water/North Pacific Deep Water-Antarctic Intermediate Water with no apparent changes in the depths of water mass boundaries between glacial and interglacial states. Sortable silt particle size data for four cores are also examined to show that the vigour of the inflow to the Pacific, while variable, appears to have remained fairly constant on average. Among the lowest Last Glacial Maximum values of benthic d13C in the world ocean (-1.03 per mil based on Cibicidoides wüllerstorfi) occurs here at ~2200 m. Comparable values occur in the Atlantic sector of the Southern Ocean, while those from the rest of the Pacific are distinctly higher, confirming that the Southern Ocean was the source for the unventilated/nutrient-enriched water seen here. Oxygen and carbon isotopic data are compatible with a glacial cold deep water mass of high salinity, but lower nutrient content (or better ventilated), below ~3500 m depth. This contrasts with the South Atlantic where unventilated/nutrient-enriched water extends all the way to the sea bed. Comparison with previous studies also suggests that the deeper reaches of the Antarctic Circumpolar Current below ~3500 m are not homogeneous all around the Southern Ocean, with the Kerguelen Plateau and/or the Macquarie-Balleny Ridges posing barriers to the eastward spread of the deepest low-d13C water out of the South Atlantic in glacials. These barriers, combined with inferred high density of bottom waters, restricted inter-basin exchange and allow three glacial domains dominated by bottom waters from Weddell Sea, Adelie Coast and Ross Sea to be defined. We suggest that the Ross Sea was the main source of the deep water entering the Pacific below ~3500 m.

Sulphur mineralogy and geochemistry of serpentinites and gabbros from the Atlantis Massif

In-situ uplifted portions of oceanic crust at the central dome of the Atlantis Massif (Mid-Atlantic Ridge, 30°N) were drilled during Expeditions 304 and 305 of the Integrated Ocean Drilling Program (IODP) and a 1.4 km section of predominantly gabbroic rocks with minor intercalated ultramafic rocks were recovered. Here we characterize variations in sulfur mineralogy and geochemistry of selected samples of serpentinized peridotites, olivine-rich troctolites and diverse gabbroic rocks recovered from Hole 1309D. These data are used to constrain alteration processes and redox conditions and are compared with the basement rocks of the southern wall of the Atlantis Massif, which hosts the Lost City Hydrothermal Field, 5 km to the south. The oceanic crust at the central dome is characterized by Ni-rich sulfides reflecting reducing conditions and limited seawater circulation. During uplift and exhumation, seawater interaction in gabbroic-dominated domains was limited, as indicated by homogeneous mantle-like sulfur contents and isotope compositions of gabbroic rocks and olivine-rich troctolites. Local variations from mantle compositions are related to magmatic variability or to interaction with seawater-derived fluids channeled along fault zones. The concomitant occurrence of mackinawite in olivine-rich troctolites and an anhydrite vein in a gabbro provide temperature constraints of 150-200 °C for late circulating fluids along local brittle faults below 700 m depth. In contrast, the ultramafic lithologies at the central dome represent domains with higher seawater fluxes and higher degrees of alteration and show distinct changes in sulfur geochemistry. The serpentinites in the upper part of the hole are characterized by high total sulfide contents, high d34Ssulfide values and low d34Ssulfate values, which reflect a multistage history primarily controlled by seawater-gabbro interaction and subsequent serpentinization. The basement rocks at the central dome record lower oxygen fugacities and more limited fluid fluxes compared with the serpentinites and gabbros of the Lost City hydrothermal system. Our studies are consistent with previous results and indicate that sulfur speciation and sulfur isotope compositions of altered oceanic mantle sequences commonly evolve over time. Heterogeneities in sulfur geochemistry reflect the fact that serpentinites are highly sensitive to local variations in fluid fluxes, temperature, oxygen and sulfur fugacities, and microbial activity.