Crozet Islands Research Articles

Can animal culture drive evolution?

Once the purview of humans, culture has been observed in all sorts of animals. But are these behaviors merely ephemeral fads or can they shape the genes and traits of future generations? In Antarctic waters, a group of killer whales makes a wave big enough to knock a seal from its ice floe. Meanwhile, in the North Atlantic, another killer whale group blows bubbles and flashes white bellies to herd a school of herrings into a ball. And in the Crozet Archipelago in the Southern Ocean, still another group charges at seals on a beach, grasps the prey with their teeth, and then backs into the water (1). Some researchers see these as more than curious behaviors or YouTube photo ops: they see cultural mores—introduced into populations and passed to future generations—that can actually affect animals’ fitness. Killer whales are divided into groups known as ecotypes, with highly specialized diets and hunting traditions passed down over generations. Here, a mammal-eating ecotype in the North Pacific hunts seal. Photograph by David Ellifrit, courtesy of Center for Whale Research. Killer whales, also known as orcas ( Orcinus orca ), have a geographic range stretching from the Antarctic to the Arctic. As a species, their diet includes birds, fish, mammals, and reptiles. But as individuals, they typically fall into groups with highly specialized diets and hunting traditions passed down over generations. Increasingly, scientists refer to these learned feeding strategies as culture, roughly defined as information that affects behavior and is passed among individuals and across generations through social learning, such as teaching or imitation (2). Scientists once placed culture squarely in the human domain. But discoveries in recent decades suggest that a wide range of cultural practices—from foraging tactics and vocal displays to habitat use and play—may influence the lives of other animals as …

Towards a better understanding of Southern Ocean biogeography: new evidence from benthic hydroids

Benthic hydroids are an important component of the Antarctic benthic ecosystem. They have been studied since the first Antarctic expeditions, and in recent years, there has been an important increase in biodiversity studies. In order to analyse the relationship among different areas and validate/dismiss previous biogeographical hypotheses, we have compiled all valid records of the known benthic hydroid species from the Antarctic and Sub-Antarctic regions, and used two previous scheme divisions of the Southern Ocean. In both cases, a hierarchical cluster was performed with the SIMPROF test. Our results suggest the division of the Southern Ocean into three main regions: the first corresponds to the classical Patagonian region; the second consists of the Kerguelen Archipelago, Crozet Island, Prince Edward Islands and Bouvet; the third, here referred to as the Antarctic region, is formed by South Georgia, the Scotia Arc archipelagos and High Antarctica. The results obtained also support the classical division of High Antarctica into two subregions, corresponding to West and East Antarctica. Nevertheless, the limits between both regions are still unclear, mainly because of the scarcity of data from some areas and the complete absence of information from others.

Feeding ecology, isotopic niche, and ingestion of fishery-related items of the wandering albatross Diomedea exulans at Kerguelen and Crozet Islands

Feeding ecology and isotopic niche of the wandering albatross Diomedea exulans were investigated in the poorly studied population on the Kerguelen Islands and compared to that on the Crozet Islands. Fish (48% by mass) and cephalopods (46%) were similarly important in chick food at Kerguelen, while cephalopods (87%) dominated the diet at Crozet. Fish prey included mainly deep-sea species, with the Patagonian toothfish Dissostichus eleginoides being the main item. Cephalopod beaks were identified, most of which were from adult oceanic squids. Albatrosses preyed upon the same taxa at both localities, but in different proportions. Histioteuthis atlantica (30% by number), Galiteuthis glacialis (13%), and Kondakovia longimana (10%) were the main squid prey at Kerguelen, while K. longimana (35%) and H. eltaninae (23%) dominated at Crozet. Chick feather δ15N values were higher in wandering albatrosses than in other oceanic seabirds of the 2 communities, indicating that the wandering albatross is an apex consumer together with the sperm whale and sleeper shark that have similar δ15N values. Satellite-tracked wandering albatrosses foraged in local subantarctic waters and farther north, with some Crozet birds overlapping with those from the Kerguelen population in western Kerguelen waters. Anthropogenic items (e.g. plastic fragments, hooks) were found in half the food samples. All fishery-related items were from the local toothfish fishery. The high number of hooks from Crozet indicated the presence of a fairly large number of illegal longliners in the area during the Austral winter 1998. A review of the feeding habits of Diomedea spp. highlights the need for more dietary investigations to achieve effective conservation and management of this endangered group of charismatic seabirds.

Lagrangian analysis of multi-satellite data in support of open ocean Marine Protected Area design

Compared to ecosystem conservation in territorial seas, protecting the open ocean has peculiar geopolitical, economic and scientific challenges. One of the major obstacle is defining the boundary of an open ocean Marine Protected Area (MPA). In contrast to coastal ecosystems, which are mostly constrained by topographic structures fixed in time, the life of marine organisms in the open ocean is entrained by fluid dynamical structures like eddies and fronts, whose lifetime occurs on ecologically-relevant timescales. The position of these highly dynamical structures can vary interannually by hundreds of km, and so too will regions identified as ecologically relevant such as the foraging areas of marine predators. Thus, the expected foraging locations suggested from tracking data cannot be directly extrapolated beyond the year in which the data were collected. Here we explore the potential of Lagrangian methods applied to multisatellite data as a support tool for a MPA proposal by focusing on the Crozet archipelago oceanic area (Indian Sector of the Southern Ocean). By combining remote sensing with biologging information from a key marine top predator (Eudyptes chrysolophus, or Macaroni penguin) of the Southern Ocean foodweb, we identify a highly dynamic branch of the Subantarctic front as a foraging hotspot. By tracking this feature in historical satellite data (1993–2012) we are able to extrapolate the position of this foraging ground beyond the years in which tracking data are available and study its spatial variability.

Sectorial land snail damage to the lichen Argopsis friesiana could be explained by metabolite profiles

Notodiscus hookeri is the only native land snail of the sub-Antarctic present in Crozet Archipelago. Two shell ecophenotypes co-exist on Possession Island and feed exclusively on lichens [1] that are symbiotic organisms widely distributed in sub-Antarctic islands. To improve our understanding of lichen-snail trophic interactions, the endemic tripartite lichen Argopsis friesiana was selected. The snail belonging to the organic ecophenotype occurs sympatrically with A. friesiana. Profiling and quantification of the major secondary metabolites in the whole lichen were carried out by LC-DAD-MS. Two main compounds were identified, the depside atranorin (8.2 mg g-1 DM) and the depsidone argopsin. Besides, a screening of primary metabolites was carried out to determine which compounds could be useful for the snail energetic demands. Glutamate, glutamine, gamma-aminobutyric acid and alpha-alanine were the main amino acids found in the lichen in low concentrations (0.4 mg·g-1 DM). Carbohydrates, including arabitol (10.2 mg g-1), mannitol (4.0.10-4 mg g-1) and sucrose (3.0.10-4 mg g-1), were also identified. In cultivation, N. hookeri snails were fed with fructified thalli of A. friesiana. Snails (n = 20) ate the podetia cortex and phyllocladia but they clearly avoided apothecia, the reproductive organs. This sectorial damage of the lichen by the snail suggested a differential distribution of the metabolites. Therefore, a profiling of secondary compounds was performed by Direct Analysis in Real Time – Mass Spectroscopy (DART-MS) [2] on each morphological part of the lichen (phyllocladia, apothecia, podetia and cephalodia). The identification and distribution of secondary metabolites, fatty acids, amino acids and carbohydrates should help us to determine whether metabolites affect snail feeding choice and which of them could be involved.

Marked phylogeographic structure of Gentoo penguin reveals an ongoing diversification process along the Southern Ocean

Two main hypotheses have been debated about the biogeography of the Southern Ocean: (1) the Antarctic Polar Front (APF), acting as a barrier between Antarctic and sub-Antarctic provinces, and (2) the Antarctic Circumpolar Current (ACC), promoting gene flow among sub-Antarctic areas. The Gentoo penguin is distributed throughout these two provinces, separated by the APF. We analyzed mtDNA (HVR1) and 12 microsatellite loci of 264 Gentoo penguins, Pygoscelis papua, from 12 colonies spanning from the Western Antarctic Peninsula and the South Shetland Islands (WAP) to the sub-Antarctic Islands (SAI). While low genetic structure was detected among WAP colonies (mtDNA ФST=0.037–0.133; microsatellite FST=0.009–0.063), high differentiation was found between all SAI and WAP populations (mtDNA ФST=0.678–0.930; microsatellite FST=0.110–0.290). These results suggest that contemporary dispersal around the Southern Ocean is very limited or absent. As predicted, the APF appears to be a significant biogeographical boundary for Gentoo penguin populations; however, the ACC does not promote connectivity in this species. Our data suggest demographic expansion in the WAP during the last glacial maximum (LGM, about 20kya), but stability in SAI. Phylogenetic analyses showed a deep divergence between populations from the WAP and those from the SAI. Therefore, taxonomy should be further revised. The Crozet Islands resulted as a basal clade (3.57Mya), followed by the Kerguelen Islands (2.32Mya) as well as a more recent divergence between the Falkland/Malvinas Islands and the WAP (1.27Mya). Historical isolation, local adaptation, and past climate scenarios of those Evolutionarily Significant Units may have led to different potentials to respond to climate changes.

Dispersal in the sub-Antarctic: king penguins show remarkably little population genetic differentiation across their range.

BackgroundSeabirds are important components of marine ecosystems, both as predators and as indicators of ecological change, being conspicuous and sensitive to changes in prey abundance. To determine whether fluctuations in population sizes are localised or indicative of large-scale ecosystem change, we must first understand population structure and dispersal. King penguins are long-lived seabirds that occupy a niche across the sub-Antarctic zone close to the Polar Front. Colonies have very different histories of exploitation, population recovery, and expansion.ResultsWe investigated the genetic population structure and patterns of colonisation of king penguins across their current range using a dataset of 5154 unlinked, high-coverage single nucleotide polymorphisms generated via restriction site associated DNA sequencing (RADSeq). Despite breeding at a small number of discrete, geographically separate sites, we find only very slight genetic differentiation among colonies separated by thousands of kilometers of open-ocean, suggesting migration among islands and archipelagos may be common. Our results show that the South Georgia population is slightly differentiated from all other colonies and suggest that the recently founded Falkland Island colony is likely to have been established by migrants from the distant Crozet Islands rather than nearby colonies on South Georgia, possibly as a result of density-dependent processes.ConclusionsThe observed subtle differentiation among king penguin colonies must be considered in future conservation planning and monitoring of the species, and demographic models that attempt to forecast extinction risk in response to large-scale climate change must take into account migration. It is possible that migration could buffer king penguins against some of the impacts of climate change where colonies appear panmictic, although it is unlikely to protect them completely given the widespread physical changes projected for their Southern Ocean foraging grounds. Overall, large-scale population genetic studies of marine predators across the Southern Ocean are revealing more interconnection and migration than previously supposed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0784-z) contains supplementary material, which is available to authorized users.

Comparison analysis of global carbon monoxide concentration derived from SCIAMACHY, AIRS, and MOPITT

ABSTRACTObservations of carbon monoxide (CO) retrieved from Scanning Imaging Absorption SpectroMeter for Atmospheric Chartography (SCIAMACHY), Measurement of Pollution in the Troposphere (MOPITT), and Atmospheric Infrared Sounder (AIRS) are compared in this article. To better validate the retrieved data from SCIAMCHY, AIRS, and MOPITT, six surface stations at different locations and with various elevations were chosen. The results show these three instruments can all reflect CO spatial distribution well and show same temporal variations of CO concentration as well as six surface station measurements. MOPITT and AIRS have similar retrieval results with correlation coefficients being mostly over 0.70, except for a sixth field station on Crozet Island. The three satellites all have the ability to monitor CO concentration change on land, but SCIAMCHY results show a relatively larger bias than MOPITT and AIRS in low CO concentration areas because of systematic error.

Early diving behaviour in juvenile penguins: improvement or selection processes.

The early life stage of long-lived species is critical to the viability of population, but is poorly understood. Longitudinal studies are needed to test whether juveniles are less efficient foragers than adults as has been hypothesized. We measured changes in the diving behaviour of 17 one-year-old king penguins Aptenodytes patagonicus at Crozet Islands (subantartic archipelago) during their first months at sea, using miniaturized tags that transmitted diving activity in real time. We also equipped five non-breeder adults with the same tags for comparison. The data on foraging performance revealed two groups of juveniles. The first group made shallower and shorter dives that may be indicative of early mortality while the second group progressively increased their diving depths and durations, and survived the first months at sea. This surviving group of juveniles required the same recovery durations as adults, but typically performed shallower and shorter dives. There is thereby a relationship between improved diving behaviour and survival in young penguins. This long period of improving diving performance in the juvenile life stage is potentially a critical period for the survival of deep avian divers and may have implications for their ability to adapt to environmental change.

Magmatic Activity on a Motionless Plate: the Case of East Island, Crozet Archipelago (Indian Ocean)

Magmatic Activity on a Motionless Plate: the Case of East Island, Crozet Archipelago (Indian Ocean)

A tale of three islands: Downstream natural iron fertilization in the Southern Ocean

AbstractIron limitation of primary productivity prevails across much of the Southern Ocean but there are exceptions; in particular, the phytoplankton blooms associated with the Kerguelen Plateau, Crozet Islands, and South Georgia. These blooms occur annually, fertilized by iron and nutrient‐rich shelf waters that are transported downstream from the islands. Here we use a high‐resolution (1/12°) ocean general circulation model and Lagrangian particle tracking to investigate whether inter‐annual variability in the potential lateral advection of iron could explain the inter‐annual variability in the spatial extent of the blooms. Comparison with ocean color data, 1998–2007, suggests that iron fertilization via advection can explain the extent of each island's annual bloom, but only the inter‐annual variability of the Crozet bloom. The area that could potentially be fertilized by iron from Kerguelen was much larger than the bloom, suggesting that there is another primary limiting factor, potentially silicate, that controls the inter‐annual variability of bloom spatial extent. For South Georgia, there are differences in the year‐to‐year timing of advection and consequently fertilization, but no clear explanation of the inter‐annual variability observed in the bloom's spatial extent has been identified. The model results suggest that the Kerguelen and Crozet blooms are terminated by nutrient exhaustion, probably iron and or silicate, whereas the deepening of the mixed layer in winter terminates the South Georgia bloom. Therefore, iron fertilization via lateral advection alone can explain the annual variability of the Crozet bloom, but not fully that of the Kerguelen and South Georgia blooms.

Planktic foraminifer and coccolith contribution to carbonate export fluxes over the central Kerguelen Plateau

We report the contribution of planktic foraminifers and coccoliths to the particulate inorganic carbon (PIC) export fluxes collected over an annual cycle (October 2011/September 2012) on the central Kerguelen Plateau in the Antarctic Zone (AAZ) south of the Polar Front (PF). The seasonality of PIC flux was decoupled from surface chlorophyll a concentration and particulate organic carbon (POC) fluxes and was characterized by a late summer (February) maximum. This peak was concomitant with the highest satellite-derived sea surface PIC and corresponded to a Emiliania huxleyi coccoliths export event that accounted for 85% of the annual PIC export. The foraminifer contribution to the annual PIC flux was much lower (15%) and dominated by Turborotalita quinqueloba and Neogloboquadrina pachyderma. Foraminifer export fluxes were closely related to the surface chlorophyll a concentration, suggesting food availability as an important factor regulating the foraminifer's biomass. We compared size-normalized test weight (SNW) of the foraminifers with previously published SNW from the Crozet Islands using the same methodology and found no significant difference in SNW between sites for a given species. However, the SNW was significantly species-specific with a threefold increase from T. quinqueloba to Globigerina bulloides. The annual PIC:POC molar ratio of 0.07 was close to the mean ratio for the global ocean and lead to a low carbonate counter pump effect (~5%) compared to a previous study north of the PF (6–32%). We suggest that lowers counter pump effect south of the PF despite similar productivity levels is due to a dominance of coccoliths in the PIC fluxes and a difference in the foraminifers species assemblage with a predominance of polar species with lower SNW.

Multivariate analyses of Antarctic and sub-Antarctic seaweed distribution patterns: An evaluation of the role of the Antarctic Circumpolar Current

Biogeographic barriers and ecological corridors are fundamental in defining macroecological and evolutionary processes. Ocean circulation, considering present and past patterns of continental drift, can isolate or connect many groups of marine organisms, including seaweeds. These benthic organisms present spores and propagules as planktonic stages that drift with currents and or tides, and have been a sensible indicator of changes to biogeographical distribution patterns. Phycological studies have been exhaustive in the sub-Antarctic and Antarctic seaweed communities. However, the role of the Antarctic Circumpolar Current (ACC) in shaping marine phytogeographic diversity has been poorly investigated. The ACC connects the major world oceans and redistributes oceanic properties, such as heat, salt, and nutrients, consisting of three major circumpolar fronts (in order of north to southward): the Sub-Antarctic Front (SAF), the Antarctic Polar Front (PF), and the Southern Antarctic Circumpolar Front (SACF). This paper's aim is to understand the role of the ACC fronts as a constraint on seaweed distribution patterns in different taxonomic levels, in relation to the southern Sub-Tropical areas, as well as to compare sections connected with South America (1: north), influenced by the Ross Sea Gyre (2: Western Antarctica Peninsula) and by the Weddell Sea Gyre (3: Eastern Antarctica Peninsula). nMDS showed differences in the distributional patterns of species and genera in relation to the zones and sections. The predicted latitudinal gradient of species richness was observed, and by comparing biogeographic zones, two main clusters were observed: Sub-tropical and Sub-Antarctica; and Polar Front (Antarctic Peninsula) and SACF (areas surrounding continental Antarctica), suggesting, for this sort of macroscale analysis, that ACC still has a role of “watershed barrier”. However, a lower dissimilarity (higher similarity) was observed between the 2nd (Eastern Antarctica Peninsula – EAP – or under influence of the Weddell Sea Gyre, and some sub-Antarctic islands as South Orcadas, South Georgia and Crozet Archipelago) and the 1st sectors (Chilean and Argentinean Patagonia and surrounding islands, Falklands, South Shetlands and including Antarctic Peninsula). When considering recently reported changes in diversity patterns of these locations, this result could demonstrate the existence of a clear species distributional flux, despite evidence of the ACC being a limit to dispersal. Therefore, this contribution has used previously published data to provide a tool for monitoring future biogeographical changes to the flora and fauna of this region of the Antarctic and sub-Antarctic areas due to changes in biogeographical distribution, resulting either from natural dispersion due to global meteoceanographic changes, and or biological invasions related to anthropogenic activities. We could be witness to a period of changes in Antarctic diversity, suggesting that Antarctica may not be as isolated as was once thought.

Depredation of Patagonian toothfish (Dissostichus eleginoides) by two sympatrically occurring killer whale (Orcinus orca) ecotypes: Insights on the behavior of the rarely observed type D killer whales

AbstractSympatric forms of ecologically distinctive killer whales (Orcinus orca) have been documented worldwide. This study focused on a new case of such sympatric occurrence of the “Crozet” type and the recently described “type D” killer whales off the Crozet Islands. The two ecotypes are morphologically and genetically distinct, but they both depredate the same local longline fishery. We used observational, photo‐identification, and fishing data, collected between 2003 and 2015, to examine differences in their patterns of depredation. Of the 828 sets where ecotype could be confirmed, type D killer whales interacted with 82 (11%) of the sets, including 9 (1%) sets that were simultaneously depredated by both ecotypes. Associations between the two types were never observed. Type D killer whales typically occurred in larger groups and both ecotypes preferentially depredated Patagonian toothfish (Dissostichus eleginoides). GLMM modeling revealed that the probability of type D depredation significantly increased throughout the study period, especially in deep waters, and photo‐identification data suggested that a subset of all individuals were habituating to depredation. This study documents the partitioning of resources between two distinct ecotypes of killer whales and provides preliminary insight into the feeding ecology of the rare type D killer whale.

CCAMLR Conservation Measures: How the Chairman’s Statement Works

The ‘Final Act of the Conference on the Conservation of Antarctic Marine Living Resources’ included a statement made on 19 May 1980 by its Chairman. The ‘Chairman’s Statement’ addressed the CAMLR Convention’s application in waters adjacent to the Kerguelen and Crozet Islands over which France exercises jurisdiction by virtue of its sovereignty over the islands. The Statement included explicit reference to waters adjacent to other islands within the CCAMLR Area, where the existence of State sovereignty is recognised by all the Convention Contracting Parties. In 2007 the CCAMLR Performance Review noted the increasing frequency with which some Commission Members were invoking the Chairman’s Statement. In particular, the Review Panel expressed the view that a point has been reached where any Conservation Measure adopted by CCAMLR invariably attracts a formal reservation on the perception that a conservation measure affects the maritime jurisdictions of certain Members, particularly those exercising national sovereignty over sub-Antarctic islands in the CCAMLR Indian Ocean sector. This paper examines the background to, and practices associated with, applying CCAMLR Conservation Measure reservations under the Chairman’s Statement.

Hymenostylium recurvirostrum(Pottiaceae), a Moss Genus and Species Newly Discovered in the Southern Polar Regions

Abstract: Ochyra, R., Sollman, P. & Lebouvier, M. 2015. Hymenostylium recurvirostrum (Pottiaceae), a moss genus and species newly discovered in the southern polar regions. — Herzogia 28: 599 – 606. Hymenostylium recurvirostrum is recorded from Ile de la Possession in the Iles Crozet archipelago. This is the first record of the genus Hymenostylium from the Subantarctic. The local plants of the species are characterised and their ecology is discussed. Global distribution of H. recurvirostrum is reviewed and a map of its range in the Southern Hemisphere is presented. The current state of knowledge of the moss flora of Iles Crozet is briefly discussed.

High feather mercury concentrations in the wandering albatross are related to sex, breeding status and trophic ecology with no demographic consequences

Hg can affect physiology of seabirds and ultimately their demography, particularly if they are top consumers. In the present study, body feathers of >200 wandering albatrosses from Possession Island in the Crozet archipelago were used to explore the potential demographic effects of the long-term exposure to Hg on an apex predator. Variations of Hg with sex, age class, foraging habitat (inferred from δ13C values), and feeding habits (inferred from δ15N values) were examined as well as the influence of Hg on current breeding output, long-term fecundity and survival. Wandering albatrosses displayed among the highest Hg feather concentrations reported for seabirds, ranging from 5.9 to 95µgg−1, as a consequence of their high trophic position (δ15N values). These concentrations fall within the same range of those of other wandering albatross populations from subantarctic sites, suggesting that this species has similar exposure to Hg all around the Southern Ocean. In both immature and adult albatrosses, females had higher Hg concentrations than males (28 vs. 20µgg−1 dw on average, respectively), probably as a consequence of females foraging at lower latitudes than males (δ13C values). Hg concentrations were higher in immature than in adult birds, and they remained fairly constant across a wide range of ages in adults. Such high levels in immature individuals question (i) the frequency of moult in young birds, (ii) the efficiency of Hg detoxification processes in immatures compared to adults, and (iii) importantly the potential detrimental effects of Hg in early life. Despite very high Hg concentrations in their feathers, neither effects on adults' breeding probability, hatching failure and fledgling failure, nor on adults' survival rate were detected, suggesting that long-term bioaccumulated Hg was not under a chemical form leading to deleterious effects on reproductive parameters in adult individuals.

Glacial‐interglacial variability in diatom abundance and valve size: Implications for Southern Ocean paleoceanography

AbstractAntarctic sea ice extent along with Southern Ocean biological productivity varied considerably during glacial‐interglacial periods, and both are known to have played a considerable role in regulating atmospheric CO2 variations in the past. Here we present data on diatom absolute abundance (valves/g of sediment) and size over the past ~ 42 ka B.P. and how they link to glacial‐interglacial changes in Antarctic sea ice extent, Southern Ocean frontal systems, and aeolian dust flux. Our records of sea ice and permanent open ocean zone diatom abundances suggest a shift in the Antarctic winter sea ice limit and Polar Front respectively up to the modern‐day Polar Frontal Zone during marine isotopic stages (MIS) 2 and late MIS 3. In addition to glacial shifts in the Polar Front, diatom assemblages also recorded a plausible northward shifts in Polar Front during few intervals of MIS 1. Glacial periods north of the Polar Front in the Indian sector of the Southern Ocean were characterized by higher total diatom abundance, larger Fragilariopsis kerguelensis apical length, and Thalassiosira lentiginosa radius. This is probably a consequence of (1) a northward expansion of the opal belt, a region characterized by high production and export of biogenic silica; (2) an increase in terrigenous input, via erosion of Crozet Islands; and (3) the alleviation of iron deficit by high input of Fe‐bearing dust. The larger and highly silicified diatoms such as F. kerguelensis and T. lentiginosa may have mainly contributed in transporting biogenic silica and organic carbon to the seabed for the last 42 ka, in the northern Polar Frontal Zone of the Indian sector of the Southern Ocean.

Influence of oceanographic structures on foraging strategies: Macaroni penguins at Crozet Islands.

BackgroundIn the open ocean, eddies and associated structures (fronts, filaments) have strong influences on the foraging activities of top-predators through the enhancement and the distribution of marine productivity, zooplankton and fish communities. Investigating how central place foragers, such as penguins, find and use these physical structures is crucial to better understanding their at-sea distribution. In the present study, we compared the travel heading and speed of the world’s most abundant penguin, the Macaroni penguin (Eudyptes chrysolophus), with the distribution of surface physical structures (large-scale fronts, eddies and filaments).ResultsThe study was performed during December 2012 in the Crozet Archipelago (46.42° S; 51.86° E), South Indian Ocean. Six males at incubation stage were equipped with GPS loggers to get their trajectories. We used Eulerian and Lagrangian methods to locate large-scale fronts, mesoscale eddies (10–100 km) and part of the sub-mesoscale structures (<10 km, filaments) at the surface of the ocean. By comparing the positions of birds and these structures, we show that Macaroni penguins: i) target the sub Antarctic Front; ii) increase their foraging activity within a highly dynamic area, composed of eddy fields and filamentary structures; and iii) travel in the same direction as the predominant currents.ConclusionsWe show that penguins adjust their travel speed and movement during their whole trips in relation with the oceanographic structures visited. At a large scale, we hypothesize that Macaroni penguins target the sub Antarctic Front to find profitable patches of their main prey. At finer scale, Macaroni penguin may adopt a horizontal drifting behavior in strong currents, which could be a way to minimize costs of displacement.

Fallacia emmaesp. nov., (Bacillariophyta) a New Soil-Inhabiting Diatom Species from the Sub-Antarctic Region

Abstract During a survey of the diatom flora of some caves on Ile de la Possession, the main island of the Crozet archipelago, a small, unusual naviculoid taxon was observed, initially identified as Fallacia lenzii. The new taxon is described as Fallacia emmae but it shows features of two related genera: Fallacia and Germainiella. Thorough morphological research revealed details that, on the one hand, contradicted its placement in Fallacia, such as the relatively low number of poroids on the conopeum, the absence of external canal apertures beside the raphe slit (Fallacia-feature), and striae that are composed of one slit-like areola (Germainiella-feature). The morphology and taxonomy of the new taxon are discussed and questions are raised about the validity of genera recently split off from the genus Navicula on the basis of one, or occasionally two, morphological features.