Several long-term studies on Southern Ocean seabirds and seals have suggested a possible link between major declines in breeding performance and El Nin¬ o Southern Oscillation events. We report that the breeding performances and body condition of the blue petrel (Halobaena carulea) on the Kerguelen Islands is depressed by episodic, warm sea-surface temperatures (SSTs) in the winter before breeding. Lagged cross-correlations between SSTs in the Kerguelen sector and the Southern Oscillation Index indicate that warm SSTs were found south of the Kerguelen Islands within a year of, and between 4.2 and 5.4 years after an El Nin¬ o event took place. These results can be discussed with respect to the recently described Antarctic Circumpolar Wave that drives climatic anomalies eastward around the Southern Ocean.

Global warming is expected to increase the frequency and intensity of inter-annual variation in Sea-Surface Temperatures (SST) associated with a latitudinal shift of frontal structures in the Southern Ocean. However, the long-term consequences of these major climatic events on the biotic environment remain poorly understood. We studied the effect of SST anomalies in the southern Indian Ocean on the breeding success of eight seabird species, and found these temperature anomalies to have different effects depending on the foraging habitat of the species. The breeding success of four seabird species foraging mainly south of the Polar Front in Antarctic waters was significantly depressed by warm SST occurring mainly in winter and spring, prior to breeding. Conversely, warm SST anomalies were associated with a higher breeding success for species foraging mainly north of the Polar Front, while no significant effect was found for two species that forage on the Kerguelen plateau. These different responses to changes in the SST were also observed for two closely related species (sooty albatross Phoebetria fusca and light-mantled sooty albatross P. palpebrata) breeding at Kerguelen. These observations highlight the importance of multi-species long-term monitoring programs for understanding the ecological consequences of environmental variability. Our results suggest that the predicted southward shift of the Polar Front caused by oceanic warming could lead to an important decrease in the breeding performance of top predator seabirds depending on the location and changes of their foraging habitat in relation the Polar Front. P. Inchausti

ABSTRACT. Mle lnvestlgated the foraging behaviour of king pengulns In relation to sea-surface temperature distribution over 3 years near the Crozet Archipelago, South Indlan Ocean. Wlthln their range there are 2 hydrographlc frontaI systems, whose seasonal patterns of productivity are predictable. These are the Polar Front and the Sub-Antarctic Front. During the austral summer the foraging range of breeding king pengulns was restricted to the Polar Frontal Zone, limlted to the south by the Polar Front and to the north by the Sub-Antarctic Front. Most b~r d s travelled towards the colder water situated south of Crozet, w h~l e other birds moved east to warmer water Blrds travelling south spent more time than expected in the coldest waters generally associated with the Polar Front. Birds travelling east reached the southern limit of the Sub-Antarctic Front (sea-surface temperature between 8 and 10°C). Within the Polar Frontal Zone birds differed In their foraging behaviour, with incubating birds remaining at sea for longer times and covering longer distances. During the incubation period, king penguins travelling south tended to spend their time in areas with a sea-surface temperature between 4 and 5°C. which coincide with the location of the Polar Front. Though these birds remained a t sea longer, they did not go any further south than birds hilv~ng a n egg ready to hatch or than birds in the brooding period, which appeared to travel more directly towards the Polar Front. As the breeding season progressed, the Polar Front moved further south, out of the range of the king penguins espcc~ally those with a newly hatched c h~c k that were limited in the amount of time that they could spend at sea. King penguins breeding a t Crozet may choose between 2 strategies, in w h~c h some blrds forage towards the SubAntarctic Front but most travel south towards the Polar Front.

Changes in sea-surface temperature (SST) including the position of the sub-tropical convergence of the southern Indian Ocean were ascertained by using wandering albatrosses Dio~nedea exulans fitted with temperature recorders and by satellite tracking systcms. Fllght phases interspaced with frequent pauses on the sca means that albatrosses make useful tools for studying SST In the Southern Ocean, because in situ measurements (to validate satellite data) are rare because of the remoteness of the area. Comparison of satellite-derived data and measurements using albatrosses indicates a good relationship between the 2 sets of data It is suggested that albatrosses could b e useful for monitor~ng SST and validating satellite-derived data In remote areas of the Southern Ocean, particularly ~n winter when cloud cover precludes satellite measurements of SST

No abstract