Crozet Islands Research Articles

Dispersal and dispersion of southern elephant seals in the Kerguelen province, Southern Ocean

AbstractSouthern elephant sealsMirounga leoninawithin the Kerguelen province disperse between Marion Island (MI), Iles Crozet (IC) and Iles Kerguelen (IK) despite the high site fidelity characteristic of this species. From 1987–2002, 199 IC individuals, or 11.63% of the tagged population there, were resighted at MI. Resights of IC seals at MI peaked during the juvenile moult and seals aged 0–2 represent 66% of all resights made. Equal numbers of male and female seals (all age classes) were dispersing. Dispersing breeding females (n= 22, on 33 occasions) outnumbered dispersing breeding males (n= 6, on 16 occasions), after initially emigrating from IC to MI as juvenile seals (natal dispersal). Greater male-mediated gene flow was ultimately attained due to the polygynous mating system and some extremely successful males. Of 132 seals fitted with satellite-relay data loggers at MI, six hauled out at IC and three at IK. Two of the seals which migrated to IC were born at MI; all others were unmarked males likely to be native to IC or IK. Dispersal should ideally be considered when assessing vital rates for southern Indian Ocean elephant seal populations.

A carbon budget for a naturally iron fertilized bloom in the Southern Ocean

Subantarctic islands in the high-nutrient, low-chlorophyll (HNLC) Southern Ocean are natural sources of iron and stimulate blooms in their proximity, such as the one observed close to the Crozet Islands (52°E, 46°S). During 2004/2005, particulate organic carbon (POC) export was measured using the 234Th technique in the Crozet bloom and compared with an HNLC control region. Initial results showed that iron release had no effect on daily POC export rates, thus any iron-driven enhancement in POC export was due to a longer export phase in the bloom region when compared to the control region. The duration of the export event was empirically estimated by closing the silicon budget, thus allowing seasonal POC export to be calculated by applying the export duration to the daily rates of POC export. This yields a seasonal estimate of POC export that is 3.6 times larger (range 1.9–7.1) in the iron-fertilized region than in the HNLC control region. These estimates of POC export were then compared to independent estimates of organic matter storage in the upper ocean, which are significant in both the HNLC and control regions. Overall, integrated POC export was significantly (approximately 50%) lower than estimated seasonal new production, the fraction of production that is supported by inputs of new nutrients. Finally, the sequestration efficiency, the numerical relationship between the supply of the limiting nutrient, iron, and the key ecosystem function of POC export at 100 m, is estimated to be 16,790 mol:mol.

Iron and manganese diagenesis in deep sea volcanogenic sediments and the origins of pore water colloids

Volcanogenic sediments are typically rich in Fe and Mn-bearing minerals that undergo substantial alteration during early marine diagenesis, however their impact on the global biogeochemical cycling of Fe and Mn has not been widely addressed. This study compares the near surface (0–20 cm below sea floor [cmbsf]) aqueous (<0.02 μm) and aqueous + colloidal here in after ‘dissolved’ (<0.2 μm) pore water Fe and Mn distributions, and ancillary O 2(aq), NO 3 - and solid-phase reactive Fe distributions, between two volcanogenic sediment settings: [1] a deep sea tephra-rich deposit neighbouring the volcanically active island of Montserrat and [2] mixed biosiliceous–volcanogenic sediments from abyssal depths near the volcanically inactive Crozet Islands archipelago. Shallow penetration of O 2(aq) into Montserrat sediments was observed (<1 cmbsf), and inferred to partially reflect oxidation of fine grained Fe(II) minerals, whereas penetration of O 2(aq) into abyssal Crozet sediments was >5 cmbsf and largely controlled by the oxidation of organic matter. Dissolved Fe and Mn distributions in Montserrat pore waters were lowest in the surface oxic-layer (0.3 μM Fe; 32 μM Mn), with maxima (20 μM Fe; 200 μM Mn) in the upper 1–15 cmbsf. Unlike Montserrat, Fe and Mn in Crozet pore waters were ubiquitously partitioned between 0.2 μm and 0.02 μm filtrations, indicating that the pore water distributions of Fe and Mn in the (traditionally termed) ‘dissolved’ size fraction are dominated by colloids, with respective mean abundances of 80% and 61%. Plausible mechanisms for the origin and composition of pore water colloids are discussed, and include prolonged exposure of Crozet surface sediments to early diagenesis compared to Montserrat, favouring nano-particulate goethite formation, and the elevated dissolved Si concentrations, which are shown to encourage fine-grained smectite formation. In addition, organic matter may stabilise authigenic Fe and Mn in the Crozet pore waters. We conclude that volcanogenic sediment diagenesis leads to a flux of colloidal material to the overlying bottom water, which may impact significantly on deep ocean biogeochemistry. Diffusive flux estimates from Montserrat suggest that diagenesis within tephra deposits of active island volcanism may also be an important source of dissolved Mn to the bottom waters, and therefore a source for the widespread hydrogenous MnO x deposits found in the Caribbean region.

The Effects of Natural Iron Fertilisation on Deep-Sea Ecology: The Crozet Plateau, Southern Indian Ocean

The addition of iron to high-nutrient low-chlorophyll (HNLC) oceanic waters stimulates phytoplankton, leading to greater primary production. Large-scale artificial ocean iron fertilization (OIF) has been proposed as a means of mitigating anthropogenic atmospheric CO2, but its impacts on ocean ecosystems below the photic zone are unknown. Natural OIF, through the addition of iron leached from volcanic islands, has been shown to enhance primary productivity and carbon export and so can be used to study the effects of OIF on life in the ocean. We compared two closely-located deep-sea sites (∼400 km apart and both at ∼4200 m water depth) to the East (naturally iron fertilized; +Fe) and South (HNLC) of the Crozet Islands in the southern Indian Ocean. Our results suggest that long-term geo-engineering of surface oceanic waters via artificial OIF would lead to significant changes in deep-sea ecosystems. We found that the +Fe area had greater supplies of organic matter inputs to the seafloor, including polyunsaturated fatty acid and carotenoid nutrients. The +Fe site also had greater densities and biomasses of large deep-sea animals with lower levels of evenness in community structuring. The species composition was also very different, with the +Fe site showing similarities to eutrophic sites in other ocean basins. Moreover, major differences occurred in the taxa at the +Fe and HNLC sites revealing the crucial role that surface oceanic conditions play in changing and structuring deep-sea benthic communities.

Fluxes of particulate iron from the upper ocean around the Crozet Islands: A naturally iron-fertilized environment in the Southern Ocean

[1] Despite a large macronutrient reservoir, the Southern Ocean has low levels of chlorophyll, primarily due to low iron availability. Exceptions to this situation are island systems where natural terrestrial iron inputs allow the development of large blooms. Particulate organic carbon (POC) and particulate (labile and refractory) iron analyses were performed on large (>53 μm) particles collected at the base of the mixed layer within such a system (the Crozet Islands) and in adjacent high-nutrient, low-chlorophyll (HNLC) waters. Biogenic iron was obtained by removal of estimated lithogenic Fe from the total Fe present. We combine these data with 234Th measurements to determine downward particulate Fe fluxes. Fluxes of Fe ranged from 4 to 301 nmol m−2 d−1 (labile), not detectable to 50 μmol m−2 d−1 (biogenic), and from 3 to 145 μmol m−2 d−1 (total) and, on average, were approximately four times larger below the highly productive, naturally iron-fertilized region than below the adjacent HNLC area. Downward labile iron fluxes are close to the sum of dissolved terrestrial, atmospheric, and upwelled iron calculated from the Planquette et al. (2007), model. Refractory iron fluxes are ∼2 orders of magnitude larger, and these can only have come from particles advected from the plateau itself. The “biogenic Fe,” is a substantial fraction (0–76, mean 23%) of the total particulate Fe to the north of the islands. The origin of this Fe pool must be dominantly biological conversion from the lithogenic fraction, as other supply terms including aeolian, deep mixing, and lateral advection of dissolved Fe are inadequate to account for the magnitude of this Fe. Inclusion of the offshore biologically available fraction of the lithogenic iron flux is therefore required to calculate fully the yield of carbon exported per unit iron injected.

Notodiscus (Charopidae) on South Georgia: some implications of shell size, shell shape, and site isolation in a singular sub-Antarctic land snail

AbstractMultivariate analysis shows that shells of Notodiscus sp. (Charopidae: Pulmonata) reported from South Georgia are smaller and proportionately taller than, but otherwise similar to, populations of Notodiscus hookeri (Reeve) from Iles Crozet and Iles Kerguelen. The origin of this solitary, and spatially limited, South Georgia population is enigmatic. It is confined to a remarkably small coastal lowland site which was glaciated at Last Glacial Maximum, precluding a Tertiary relict origin, and on the leeward north-east coast, ruling out post-glacial ocean rafting. The site is close to the King Edward Point settlement, yet the absence of any logistics connections with the Iles Crozet or Iles Kerguelen mitigates against anthropogenic introduction. The close proximity of the population to nests of blue-eyed shag (Phalacrocorax atriceps), Dominican gull (Larus dominicanus) and light-mantled sooty albatross (Phoebetria palpebrata) could imply the snail was originally introduced to South Georgia via these ocean transiting seabirds.

Cocconeis crozetensis, a new monoraphid diatom from subantarctic freshwater and moss habitats

Ultrastructural observations of one previously misidentified freshwater species of a Cocconeis (Bacillariophyceae) from the Crozet Archipelago, Indian Sector of the Southern Ocean, are presented. Cocconeis crozetensis sp. nov. possesses small valves (apical axis: 10–13 μm; transapical axis: 6.7–8.4 μm). The main frustule features that distinguish the proposed new species are: (1) the sternum valve (SV) areolae with an external vola and the internal vela, (2) the submarginal area of the raphe-sternum valve, and (3) the morphology of valvocopula and fimbriae of the SV. Possible morphological relationships with several other small Cocconeis, such as C. neodiminuta, C. neothumensis, C. placentula var. pseudolineata and C. pseudothumensis, as well as its morphological similarities with placentuloid Cocconeis are discussed. Reliable identification of C. crozetensis sp. nov. under light microscopy can prove difficult for less-experienced diatomologists and ecologists, and the use of electron microscopy proves to be unavoidable for its correct identification.

Gastrointestinal helminths of King penguins (Aptenodytes patagonicus) at Crozet Archipelago

Communities of helminths are known to be related to feeding behaviors of hosts. While climate change and overfishing can impact food availability for Antarctic piscivorous predators, knowledge about infectious and parasitic diseases among Antarctic species is scarce or fragmentary. We studied the helminth community of King penguins (Aptenodytes patagonicus) from the Crozet Archipelago, the main breeding area of the species. Based on a sample of 41 individuals found freshly dead from predation or starvation, the gastrointestinal helminth community in King penguins was composed of 1 species of cestode (Tetrabothrius wrighti) and 2 species of nematodes (Tetrameres wetzeli and Contracaecumheardi). Cestodes formed the core of the helminth community (97.5% of worms collected) with a prevalence of infestation of 100% and a mean intensity of 178.6 worms per host. Sources of infestation and pathologies caused by these worms are also discussed.

Discovery of a mid-latitude sympatric area for two Southern Hemisphere blue whale subspecies

In the Southern Indian Ocean, 2 subspecies of blue whales Balaenoptera musculus spp. occur, the Antarctic B. m. intermedia and the pygmy blue whale B. m. brevicauda. Until the present study was conducted it was assumed that the distribution of these 2 subspecies was delimited by the Antarctic Convergence (52° to 56° S) during the austral summer. Here, we report results from the first year-long, continuous acoustic monitoring of blue whales in mid-latitude waters off the Crozet Islands (46° 25' S, 51° 40' E). Using acoustic data from an International Monitoring System hydroa- coustic station, we found that Antarctic and pygmy blue whales occur sympatrically in this area based on detection of their stereotyped calls. Antarctic blue whale calls were recorded year-round, indicat- ing continuous presence in the region, which contradicts the migration paradigm attributed to this subspecies. Three geographically distinct types of pygmy blue whale calls were recorded during the summer and autumn only. The Madagascan call type was the most frequently recorded, while Sri Lankan and Australian call types recorded in this area suggest basin-scale longitudinal and latitudi- nal movements. During spring and summer, blue whale calls were often associated with higher fre- quency sounds (D calls), which have been attributed to feeding activity. The summer co-occurrence of blue whale subspecies highlights the importance of this productive sub-Antarctic area as a blue whale hotspot and provides new insights into blue whale seasonal distribution and segregation.

Introduced black rats Rattus rattus on Ile de la Possession (Iles Crozet, Subantarctic): diet and trophic position in food webs

Rats introduced on islands can affect ecosystem structure and function by feeding on terrestrial plants and both marine and terrestrial animals. The diet and trophic position of Rattus rattus introduced on Ile de la Possession (Iles Crozet) was assessed from two sites, according to the presence or absence of a king penguin colony. We used three complementary assays: macroanalyses of the stomach, faecal microhistology, and stable isotope analyses of δ15N/δ13C in liver. Near the rookery, spermatophytes contributed on average 50% (confidential interval: 23–75) to the diet based on isotopes, mainly consisting in reproductive parts of Poa spp., Agrostis magellanica, and Cerastium fontanum identified in faeces. Terrestrial animal preys were represented by insects that contributed 25% (0–56) in isotopes, dominated in faeces by caterpillars of Pringleophaga spp. and adult weevils. Bird remains were found in faeces, forming 18% (6–30) of isotopes. Terrestrial earthworms contributed to 7% (0–21), with chaetae observed in faeces. On the other site, spermatophytes represented 62% (51–73) of assimilated food in rats’ livers, mainly formed by Poaceae and Acaena magellanica, insects by caterpillars [24% (10–39)], and terrestrial earthworms [13% (2–23)]. Our results suggest that rats, which were found at the top of terrestrial food chains, may have a direct role on a such simplified ecosystem, by preying on the most abundant and largest body-sized terrestrial invertebrates,—e.g. the keystone species Pringleophaga spp.—, and by feeding on both reproductive and vegetative parts of autochthonous and introduced plants. The discrepancies and usefulness of employing both isotopes and faecal analyses are discussed.

Hydrodynamics between Africa and Antarctica during Austral Summer 2008

Under the International Polar Year endorsed project (IPY#70), the southwest Indian Ocean sector of the Southern Ocean was surveyed during the austral summer of 2008 by deploying expendable CTD probes along the ship tracks : Cape Town–India Bay, Antarctica (Track-1) and Prydz Bay, Antarctica–Cape Town (Track-2). The meteorological data revealed that the unstable marine atmosphere boundary layer (MABL) facilitated a turbulent heat loss of 45 Wm − 2 on average, in conditions of variable wind intensity north of 43°S along Track-1; south of 63°S and north of 51°S the ocean was conducive to higher turbulent heat loss amounting to 95 Wm − 2 (on average) along Track-2. Surface imprints of hydrological fronts were determined by using surface gradient and subsurface temperature and salinity indicators. The core of Agulhas Current was identified between 36.5° and 37.5°S along Track-2, while the Agulhas Retroflection (AR) Front was located at 39.7°S south of Cape Town. The Subtropical (STF), Subantarctic (SAF) and Polar Fronts (PF) exhibited double frontal structures, whose meridional meandering is governed by bottom topography and modulated by planetary vorticity. A large southward deviation in the position of southern PF by 3.5° latitude on Track-1 was observed. Northern and southern SAF and southern STF meander by 2°–3.5° northward; their merger just north of Crozet Island facilitate an enhanced baroclinic transport of 12 Sv in the upper 1000 m. Three anticyclones that detach from the AR transport 17 Sv into the southeast Atlantic. The baroclinic transport contributed by AC and its retroflection across Track-2 amounted to 17.6 Sv. More than 50% of the ACC transport was confined to the 100–500 m depth layer. Water masses have been identified and their zonal extent quantified along the tracks. Strong convective cooling is responsible for the production of Subtropical Mode Water in the eastern Crozet Basin, which was detected near 43.5° and 41.5°S along Track-1 and -2, respectively. The Circumpolar Deep Water was encountered between 600 and 900 m at 51°S on Track-1 and spanned 54°–60°S on Track-2. We also offer an example of the modification of the MABL through strong air–sea interaction in the vicinity of South Africa by employing satellite-derived surface winds and heat fluxes.

Detection range modeling of blue whale calls in Southwestern Indian Ocean

In the Southwestern Indian Ocean, one year of continuous acoustic data from calibrated hydrophones maintained by the International Monitoring System provided data on blue whale calls from two subspecies Antarctic and pygmy blue whales. Using an automatic detection method with a fixed threshold, both call types were detected and received levels were measured for each detected call. By using a parabolic equation loss model configured with the precise characteristics of the biological source, hydroacoustic station, and environment in the study area, distances at which calls could be detected were estimated. These methods were used to define the maximum detection range around each array of hydrophones and the influence of the seasonal variation of the ambient noise and sound velocity on the detection ranges. Results showed that detection ranges were critically dependent on the choice of the biological source’s input parameters, including frequency bandwidth and source level. Over the course of the year, detection distances were different for both subspecies; the pygmy blue whale seemed to be consistently closer to the station than the Antarctic blue whale. The distribution of the estimated distances confirmed the presence of both subspecies of blue whales near the Crozet Islands showing the importance of this sub-Antarctic area for these endangered species, especially during the austral summer feeding season.

Estimating dispersal, recruitment and survival in a biennially breeding species, the Wandering Albatross

The study of dispersal or recruitment in long- lived birds using capture-recapture methods is challenging because temporary emigration is often a source of hetero- geneity in detection probabilities. To deal with this prob- lem, we introduced unobservable states in the multistate, spatial recruitment model of Lebreton et al. (Oikos 101:253-264, 2003) to study dispersal, recruitment and survival in the Wandering Albatross (Diomedea exulans), a species with a biennial reproduction (individuals skip breeding following a successful reproduction). We high- light some of the limitations and challenges encountered in using this approach. Our dataset came from a 36-year capture-recapture study conducted at three colonies of the Crozet archipelago. The model had five reproductive stages: pre-breeders, successful breeders, failed breeders, and birds in the year after a successful or a failed breeding attempt, which are unobservable. In adults, movements between colonies (i.e. breeding dispersal) were nested within reproductive stages. Several models with different constraints on survival equally fitted the data but had some rank deficiencies (i.e. non-identifiable parameters). Survival estimates were most biologically realistic (from 0.91 to 0.95) when survival was set equal between obser- vable/unobservable states but free to vary between suc- cessful/failed breeders and among colonies. Age-specific recruitment probabilities peaked at 9-10 years and appeared well estimated despite limitations in setting the age of constant recruitment probability. Modelling natal dispersal and recruitment required a simplification of the structure of the model due to computer limitations. When applying the complete and reduced versions of the model to the same dataset, we found that survival was well estimated in both cases. Some transition probability estimates were also similar, but transitions from unobservable to obser- vable states were poorly estimated in the simplified ver- sion. We conclude that the simplified version of the model should be limited to the estimation of natal dispersal and that the model with a full structure should be used to estimate breeding dispersal.

Small‐scale dispersal and survival in a long‐lived seabird, the wandering albatross

1. Dispersal is a fundamental but still poorly known process in population dynamics and several hypotheses have been proposed to explain its patterns. We studied natal and breeding dispersal and survival in a long-lived seabird, the wandering albatross (Diomedea exulans L.), and examined several hypotheses concerning dispersal patterns in birds. 2. We applied multi-state capture-recapture models to a 36-year data set (1969-2004) collected at three albatross colonies on Ile de Possession, Crozet Islands. Because the species has biennial reproduction, we introduced unobservable states in the model to account for the absence of individuals in those years. 3. Adults were highly faithful to their nesting colony but colony fidelity, as well as survival rate, differed slightly among colonies (fidelity ranged from 0.957 to 0.977). Breeding fidelity was highest in the colony where survival was lowest and individuals were not more likely to change colony following a failed breeding attempt than after a successful one. The colony that attracted most dispersers had the lowest density of nesting birds. 4. Philopatry (the probability that young return to breed at a birth site) was generally high but variable among colonies (ranging from 0.70 to 0.92), and survival of young differed little. Philopatry was highest in the largest colony, where the availability of potential mates was presumably greatest. However, among dispersing individuals, the colony that had the lowest density of nesting individuals, not the largest colony, attracted the most recruits. 5. Although size of the colony influenced the decision to stay or to leave in young, density was most influential in the selection of a new colony among both adult and young dispersers. Our results support the hypothesis that philopatry is the strategy favoured by most recruits and that conspecific attraction can explain variation in the level of philopatry among colonies but not settlement patterns among dispersing individuals.

Pachnobium dreuxi n. g., n. sp., ses occurrences modernes et fossiles sur l’archipel Crozet (Coléoptère Curculionidae Ectemnorrhininae)

Résumé Pachnobium dreuxi, nouvelle espèce et nouveau genre de Curculionidae Ectemnorrhininae des îles Crozet, dans l’Océan Indien sud, a été découvert sous forme fossile dans une séquence sédimentaire holocène. Deux spécimens modernes ont ensuite été trouvés parmi le matériel conservé au Muséum national d’Histoire naturelle de Paris. Il diffère très nettement de toutes les autres espèces connues de la sous-famille par son rostre profondément émarginé au sommet, sa tête massive, sa sclérotinisation réduite, ses tibias antérieurs droits et aplatis, etc. Sa biologie et son écologie sont presque entièrement inconnues, bien que certains aspects de sa morphologie comme sa faible sclérotinisation et ses yeux relativement petits soient en faveur d’une vie cachée, voire hypogée, par exemple dans la litière végétale ou dans les nids de pétrels. Les reconstructions paléoenvironnementales suggèrent qu’il fréquente des habitats à végétation dense. L’absence de captures modernes à l’île de la Possession pose la question de sa présence actuelle dans cette localité.

The Quest to Combat the Illegal Fishing of ‘White Gold’ in the Southern Ocean

The Patagonian toothfish in the waters surrounding the Kerguelen, Crozet, Heard and MacDonald Islands are under serious threat by the continued exploitation of illegal, unreported and unregulated (IUU) fishing vessels. Some IUU fishing activities involve highly elaborate transnational crime operations that use front companies, fraudulent documentation, and corrupt port officials to smuggle illegal toothfish into ports around the world. The vessels often use active intelligence methods to obtain information about a State’s enforcement efforts and exploit weaknesses in national and international fisheries law. To protect this rapidly declining resource, countries such as France and Australia that have Exclusive Economic Zones (EEZ) surrounding sub-Antarctic islands, have tightened controls over their domestic fisheries laws whilst simultaneously strengthened their operational enforcement capabilities. Both governments employ armed patrol vessels to provide surveillance and apprehend vessels operating illegally. In 2003 and 2007 Australia and France adopted a coordinated approach to surveillance and law enforcement operations by signing bilateral treaties. These agreements enable the exchange of information concerning the movements and related details of fishing vessels, cooperative surveillance activities and the establishment of a shared register of fishing vessels licensed to operate in French and Australian waters. Despite these measures, IUU fishing remains far from being eradicated. Both the domestic and bilateral treaty enforcement regime have been unable to fully address the transnational criminal nature of the problem. A multi-pronged approach needs to be adopted to control the international trade in toothfish and make the activity less attractive to those involved.

King-size fast food for Antarctic fur seals

The study of scats of adult male Antarctic fur seals Arctocephalus gazella (AFS) revealed occasional frequent capture of penguins. Although AFS adult males have been occasionally reported to kill king penguins Aptenodytes patagonicus at the shore, here we report the first observations of at-sea predation by AFS on adult king penguins in the Crozet archipelago, southern Indian Ocean. During our 20 days survey, we observed 17 penguins attacked and either severely injured or killed and consumed. Only AFS adult males were seen catching king penguins successfully. Some adult females and sub-adults also attempted to catch penguins, either at sea or in land, and so did subantarctic fur seals Arctocephalus tropicalis individuals. Our results confirm the ability of fur seals to catch and predate large seabirds, even at sea.

Bathymetry and frontal system interactions influence seasonal foraging movements of lactating subantarctic fur seals from Marion Island

Sixteen lactating subantarctic fur seals Arctocephalus tropicalis were satellite-tracked during the winter of 2006 (n = 6), summer of 2006/07 (n = 6) and autumn/winter (n = 4) of 2007, from Marion Island, Southern Ocean. Despite varied individual movement patterns, a favoured foraging area lay to the northeast of the island. In contrast to findings for populations at similar latitudes, seals from Marion Island did not undertake short overnight foraging trips, but trips consistently went beyond 300 km from the island. This aligns with the at-sea duration of lactating seals’ foraging trips from temperate Amsterdam Island, but differs from subantarctic Crozet and Macquarie islands. Time spent at sea, maximum distances travelled and movement variation of tracks from the island varied seasonally. Faecal analysis suggests the diet comprised primarily myctophid fish with limited seasonal variation. Well-defined areas of restricted movement coincided with significant bathymetric features to the west/northwest of the Crozet Plateau, with the Del Cano Rise clearly being important. Positive and negative sea-surface height anomalies (compared to the mean) appeared to be preferred by most seals across seasons. Higher summer sea-surface temperatures correlated with the movements of some seals. Higher chlorophyll a concentrations dictated transit and foraging areas during summer. Bathymetrically influenced oceanographic variables likely explain these preferred long-distance eastward movements. The Iles Crozet and Marion island subantarctic fur seals differ in their foraging ecology despite being neighbours. Conversely, the subantarctic fur seal populations from the distant Amsterdam and Marion islands appear to be similarly influenced by such environmental factors.

Whisker isotopic signature depicts migration patterns and multi-year intra- and inter-individual foraging strategies in fur seals

The movement and dietary history of individuals can be studied using stable isotope records in archival keratinous tissues. Here, we present a chronology of temporally fine-scale data on the trophic niche of otariid seals by measuring the isotopic signature of serially sampled whiskers. Whiskers of male Antarctic fur seals breeding at the Crozet Islands showed synchronous and regular oscillations in both their delta(13)C and delta(15)N values that are likely to represent their annual migrations over the long term (mean 4.8 years). At the population level, male Antarctic fur seals showed substantial variation in both delta(13)C and delta(15)N values, occupying nearly all the 'isotopic space' created by the diversity of potential oceanic habitats (from high Antarctica to the subtropics) and prey (from Antarctic krill to subantarctic and subtropical mesopelagic fishes). At the individual level, whisker isotopic signatures depict a large diversity of foraging strategies. Some seals remained in either subantarctic or Antarctic waters, while the migratory cycle of most animals encompassed a wide latitudinal gradient where they fed on different prey. The isotopic signature of whiskers, therefore, revealed new multi-year foraging strategies of male Antarctic fur seals and is a powerful tool for investigating the ecological niche during cryptic stages of mammals' life.

Diatom communities in soils influenced by the wandering albatross (Diomedea exulans)

Soil diatom communities within two breeding colonies of the wandering albatross (Diomedea exulans) on Ile de la Possession (Crozet Archipelago) were investigated. Samples were collected around occupied and abandoned nests and compared with control samples taken from soils lacking any animal influence. A total of 163 diatom taxa has been identified. Differences in the diatom flora were recorded between the two colonies, but the results show that it is almost impossible to identify a single diatom community typical for albatross-influenced areas. Diatom species composition varied markedly between control samples, occupied and abandoned nests. A turnover in the diatom community (shift from eutraphentic to oligotraphentic taxa) was observed when moving away from both occupied and abandoned nests, although no significant differences in diversity have been found. In summary, soil diatom species composition seems to indicate the impact of animal perturbations. However, it is too early to draw sound conclusions and further studies regarding the topic should be performed to confirm the results of the present study.