De La Possession Research Articles

MEDUSA: Marine benthic Ecological Data from Underwater imagery Surveys of sub-Antarctic Crozet environments

Inscribed on the UNESCO World Heritage list, the sub-Antarctic Crozet archipelago is located in a region facing significant environmental changes impacting a poorly known marine biodiversity. Underwater imagery constitutes a valuable non-invasive approach for gathering ecological data and improving our knowledge of ecosystems’ vulnerability. We here compiled two datasets, encompassing 17 video-imagery surveys of Crozet nearshore environments conducted in 2021 and 2022 at two sites of Ile de la Possession: Baie du Marin and Crique du Sphinx. Faunal abundance and algal cover data related to each survey are also provided. A total of 755 images were analysed, comprising 52 faunal and 14 algal taxa identified in 2021, as well as 45 faunal and 14 algal taxa identified in 2022. Video-transects were performed in shallow waters by scuba divers using a GoPro®HERO7 multiple camera set-up, and in deeper waters using a remotely operated vehicle. These data provide a first baseline for biodiversity and ecosystem studies, and for monitoring the long-term dynamics of Crozet benthic habitats facing natural and anthropogenic disturbances.

Responses to novelty in wild insular birds: comparing breeding populations in ecologically contrasting habitats

Islands have always provided ideal natural laboratories for assessing ecological parameters influencing behaviour. One hypothesis that lends itself well to testing in island habitats suggests that animals frequenting highly variable environments should be motivated to approach and interact with (i.e. explore) novelty. Intra-species comparisons of populations living in ecologically different island habitats may, thus, help reveal the factors that modulate animals’ responses to novelty. In this study, we presented novel objects to two geographically isolated breeding populations of the black-faced sheathbill (Chionis minor), a sedentary land-based bird that frequents remote sub-Antarctic islands. In the first population (Chionis minor ssp. crozettensis), the “Crozet group” (Baie du Marin, Ile de la Possession, Crozet Islands), breeding pairs inhabit a variable habitat close to penguin (Aptenodytes patagonicus) colonies. In the second population (Chionis minor ssp. minor), the “Kerguelen group” (île Verte, Morbihan gulf, Kerguelen Islands) breeding pairs live in penguin-free territories. In this latter population, the environment is less variable due to the presence of a broad intertidal zone which ensures year-round food availability. At both Kerguelen and Crozet, at least one breeding partner in all pairs approached at least one of the novel objects, and we found no significant differences in the latency of approach between the two populations. However, sheathbills at Crozet touched objects significantly more than birds at Kerguelen, and were also faster to touch them. We discuss how environmental variability, along with other potential influencing factors, may favour exploration of novelty in this wild insular bird.

Taxonomic and functional diversity of subtidal benthic communities associated with hard substrates at Crozet archipelago (sub-Antarctic, Southern Ocean)

Sub-Antarctic coastal marine ecosystems harbor rich and diverse benthic communities. Despite their ecological uniqueness and vulnerability to global changes, studies on benthic communities remain limited. Using underwater video-imagery, we investigated the taxonomic and functional diversity of benthic communities associated with hard substrates at Baie du Marin (Ile de la Possession, Crozet archipelago). The Baie du Marin species richness and diversity were additively partitioned to evaluate spatial patterns of species through the following spatial scales: within images, among images within transects, and among transects. We analyzed imagery data from seven transects located at different sites inside Baie du Marin and covering contrasting natural rocky habitats and underwater artificial cable substrates. A total of 50 faunal (mainly represented by Echinodermata and Porifera phyla) and 14 algae (mainly represented by Rhodophyta phylum) taxa were identified. Rocky substrates were dominated by high densities of the polychaetes Parasabella sp. and Lanice marionensis, whereas submarine cables were dominated by high densities of the bivalve Kidderia sp. attached to macroalgae. Our results show contrasted distribution patterns in the faunal and algal assemblages within the Baie du Marin, with significant ecological differences between submarine cables and natural rocky substrates. Larger spatial scale (i.e., among transects) accounted for most of the bay richness and diversity, highlighting a high-level of habitat heterogeneity within the bay. Through a trait-based approach, our findings revealed that Crozet benthic communities are characterized by low functional richness, evenness, and redundancy, highlighting a potential vulnerability to current and future natural and anthropogenic changes. This study provides a novel bentho-ecological baseline for future assessments of natural and anthropogenic impacts on the marine environment of the Crozet archipelago; and for the conservation management of these remote habitats that make part of the French Southern Territories Marine Protected Area, recently inscribed on the UNESCO World Heritage list.

Towards a Wind Urbanism in Tropical Environments

One of the conditions for the proper functioning of passive comfort in humid tropical environments is access to natural ventilation in buildings. This notion of access to natural ventilation has taken on its full meaning during the current health crisis.
 Based on this observation established by a rich literature, we asked ourselves how to ensure the sustainability of the good functioning of natural ventilation in a humid tropical environment of a building in a built complex? This questioning led us to show the importance of the context through various dimensions: the chain of natural ventilation, the programmatic context, the climatic and geographical context, the regulatory context.
 Taking these parameters into account has allowed us, in the context of a case study, the eco-district Cœur de ville de La Possession, on the island of La Réunion, to develop a new conceptual approach associating urban planning and aeraulic engineering from the beginning of the design process for maximum efficiency.
 To this end, we initiated a new approach based on: co-design, the use of physical wind tunnel simulation at different scales, the integration of environmental, architectural and landscape recommendations at the scale of the district and of the buildings making up this district, in an enforceable urban planning regulation. This has enabled us, within the framework of this eco-district, to develop the concept of the right to natural ventilation, of the windy city and of the guarantee over time of the preservation of this potential.
 The transcription of this approach in other eco-neighbourhoods in a tropical environment seems to us to be a major challenge to be considered and which could even be extended to other climatic zones, in the context of current global warming.

An estimate of the South Georgia diving petrel Pelecanoides georgicus population at Ile de la Possession, Crozet archipelago

AbstractBurrow-nesting seabirds constitute an important part of seabird diversity, yet accurate estimates of their abundance are largely lacking, limiting our understanding of their population dynamics and conservation status. We conducted a survey to estimate the number of South Georgia diving petrel (Pelecanoides georgicus) burrows during the 2013–14 breeding season on Ile de la Possession, Crozet archipelago, southern Indian Ocean. We used distance sampling and acoustic playback in order to estimate burrow densities in a priori-selected favourable nesting areas. A total of 855 burrows were detected. The mean altitude of burrows was 601.8 ± 69.4 m. The mean burrow detection distance was 1.77 ± 1.63 m. The burrow density was estimated at 15.649 burrows ha-1 (95% confidence interval (CI): 10.245–23.903) and the slope-corrected total favourable area was 2365.53 ha, which yielded an estimate 37 018 burrows (95% CI: 24 235–56 544). The playback response rate was 15.8 ± 1.3%, and 40.8 ± 1.7% of burrows were occupied or showed signs of occupation. Occupancy rates were low compared to those measured by systematic burrow inspection in other studies. Assuming that laying occurred in 80–93% of the estimated number of burrows, as estimated by previous studies, gives an estimate of 29 614 (95% CI: 19 388–45 235) to 34 426 (95% CI: 22 538–52 585) breeding pairs.

Entosthodon productus (Bryophyta, Funariaceae), an addition to the moss flora of the subantarctic Îles Crozet

Bednarek-Ochyra, H. & Plasek, V. 2019. Entosthodon productus (Bryophyta, Funariaceae), an addition to the moss flora of the subantarctic Iles Crozet. - Herzogia 32: 326 -337.Entosthodon productus, an Australasian species, is recorded for the second time from the Subantarctic. In contrast to Marion Island in the Prince Edward Islands archipelago where the species is relatively frequent, only a single specimen of E. productus was found on Ile de la Possession in the conterminous Iles Crozet archipelago. The island's plants are characterised and illustrated and the geographical distribution of E. productus is reviewed. The present diversity of the moss flora of Iles Crozet is briefly summarised.

Melosira jeanbertrandiana, a new Melosira species (Bacillariophyceae) from the sub-Antarctic region

ABSTRACTDuring a survey of the soil diatom flora of the sub-Antarctic Ile de la Possession (Iles Crozet), located in the southern Indian Ocean, an unknown Melosira species was found that could not be identified using the currently available literature on the genus. The species is described as Melosira jeanbertrandiana sp. nov. based on detailed light and scanning electron microscopy observations. The new species is characterized by a relatively high mantle, the presence of several marginal rings of acute, never bifurcating spines and a series of eight rimoportulae near the central area with several others scattered over the rest of the valve face and mantle. The girdle comprising several large, ligulate open copulae and the position of the rimoportulae clearly place this new species within the genus Melosira C.Agardh. The species was observed in bare, moist soil in scratches in cliffs bordering the ocean where the influence of sea spray is obvious. The description of this new species further increases the number of species of the Melosirales compared to other centric freshwater diatoms which are infrequently found on the sub-Antarctic islands.

Two new centric diatoms (Bacillariophyta) from the sub-Antarctic region

During a survey of the limno-terrestrial diatom flora of the sub-Antarctic region, two unknown melosiroid diatom taxa were observed in several shaded, damp cave (moss and soil) samples from Heard Island and Ile de la Possession, the main island of the Crozet Archipelago. Comparison with already known species from the genus Melosira and the recently described genera Arcanodiscus, Angusticopula and Ferocia, resulted in the description of both new taxa based on detailed light and scanning electron microscopy. A first species was described as Ferocia subantarctica sp. nov. and can be distinguished based on its numerous, narrow girdle bands, relatively weakly domed valves, a limited number of well-developed spines and a rather large, hyaline central area. The second species, Arcanodiscus desmetianus Van de Vijver sp. nov., can be recognized based on its solitary frustules, a series of parallel ridges surrounding the mantle and a hyaline central area that is only less than 50% of the total valve diameter. Both taxa are morphologically and ecologically characterized and compared with all known melosiroid taxa worldwide.

First records of aphid-pathogenic Entomophthorales in the sub-Antarctic archipelagos of Crozet and Kerguelen

Since the 20th century, the sub-Antarctic islands have suffered an increasing number of biological invasions. Despite the large number of publications on this topic, there is a lack of knowledge on parasitism rates of invasive species and on the role of parasites and pathogens to regulate their populations. Six aphid species have been introduced in the archipelagos of Crozet (Ile de la Possession, 46° 25’ S–51° 51’ E) and Kerguelen (49° 21’ S–70° 13’ E). Five of these species were found infected by entomopathogenic fungi of the order Entomophthorales. All these fungal species are cosmopolitan. Conidiobolus obscurus and Entomophthora planchoniana were the most frequently observed on Ile de la Possession and in Archipel des Kerguelen, respectively. This is the first report of pathogenic fungi of aphids on the sub-Antarctic islands. We discuss these results in the light of our current knowledge of these insect pathogens. Their introduction by aphids surviving on plants during transportation is the most likely hypothesis to explain their presence on these remote islands. Keywords: Natural enemies; introduced species; biological invasion; colonization; Zygomycetes; parasitism. (Published: 8 July 2016) Citation: Polar Research 2016, 35 , 28765, http://dx.doi.org/10.3402/polar.v35.28765

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.

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.

Description of Pseudingolfiella possessionis n. sp. (Crustacea, Amphipoda) from sub-Antarctic Île de La Possession, Crozet archipelago: the second freshwater amphipod known from the Antarctic biome, a human introduction of Gondwanan ancestry?

A new species of freshwater amphipod, Pseudingolfiella possessionis n. sp. (Senticaudata, Pseudingolfiellidae), is described from the submerged moss vegetation of small brooklets at sub-Antarctic Île de La Possession, Crozet archipelago. It constitutes the second freshwater amphipod species known for the sub-Antarctic and Antarctic region, and the fourth member of the genus. The main characters distinguishing it from all congeners are: the spine on the posterior margin of the dactylus, incisor and lamina mobilis of mandible each with 5 teeth, the setation of the maxilliped, the vestigial second article of pleopod 3 in the female, the undulate and laterally notched posterolateral margin of the external ramus of uropods 1 and 2 in the male, the spinulate dorsomedian projection of the telson.

Failure to launch: evidence of protracted parental care in albatrosses

Most albatrosses have well defined breeding seasons (Tickell 2000). Fledging tends to be spread over a longer period than laying or hatching because the duration of the chick-rearing stage is more variable than that of incubation (Warham 1990). However there are few records of albatross chicks extending fledging periods by more than a month or two (but see Brown & Adams 1984). We were thus surprised to see a juvenile Sooty Albatross Phoebetria fusca on a nest near the meteorological station on Gough Island (40°20'S 9°55'W) during the 2014-15 breeding season, three months after Sooty Albatross chicks usually fledge from Gough Island (Ryan 2007; most chicks fledge in May-June, and in 2015 the last chick near the weather station departed between 17 and 25 July). The late-fledging juvenile was first observed on 17 September 2014 and remained on its nest until at least 14 October, but apparently fledged by 19 October (the nest was empty, and no carcass was found). It seemed to be in good health throughout this period, and on being approached, it clapped its bill in the manner typical of a large nestling. Characters that indicated it was a juvenile bird still in its first year were the virtual lack of a white eye-ring, no yellow sulcus stripe on the bill, and uniformly aged, fresh plumage still with pale fringes to the back coverts (Figure 1; Marchant & Higgins 1990). Assuming a mean hatching date in mid December (Ryan 2007), this gives a fledging period of around 300 days, much longer than the 164 ± 9 SD days recorded at Ile de la Possession, Crozet Islands (46°25'S 51°45'E: maximum 178 days; Tickell 2000).

Measuring disparities in sanitation access: does the measure matter?

Initiatives to monitor progress in health interventions like sanitation are increasingly focused on disparities in access. We explored three methodological challenges to monitoring changes in sanitation coverage across socio-economic and demographic determinants: (i) confounding by wealth indices including water and sanitation assets, (ii) use of individual urban and rural settings versus national wealth indices and (iii) child-level versus household-level analyses. Sanitation coverage by wealth for children and households across settings was estimated from recent Demographic and Health Surveys in six low-income countries. Household assignment to wealth quintiles was based on principal components analyses of assets. Concordance in household quintile assignment and estimated distribution of improved sanitation was assessed using two wealth indices differing by inclusion or exclusion of water and sanitation assets and independently derived for each setting. Improved sanitation was estimated using under five children and households. Wealth indices estimated with water, and sanitation assets are highly correlated with indices excluding them but can overstate disparities in sanitation access. Independently, derived setting wealth indices highly correlate with setting estimates of coverage using a single national index. Sanitation coverage and quintile disparities were consistently lower in household-level estimates. Standard asset indices provide a reasonably robust measure of disparities in improved sanitation, although overestimation is possible. Separate setting wealth quintiles reveal important disparities in urban areas, but analysis of setting quintiles using a national index is sufficient. Estimates and disparities in household-level coverage of improved sanitation can underestimate coverage for children under five.

On The Identity ofDitrichum validinervium(Bryophyta, Ditrichaceae)

Ditrichum validinervium Kaal., a species described from Île de la Possession and Île de l'Est in the Îles Crozet archipelago in Subantarctica, is assessed and some details of its gametophyte are illustrated. An examination of the type material of this species revealed that it is inseparable from D. conicum (Mont.) Mitt. and D. validinervium is the first heterotypic synonym of this name.Bryophyta / distribution / Ditrichum / Icirc;les Crozet / Kerguelen Province / Subantarctica / taxonomy

Ultrastructure of Diatomella balfouriana with a discussion of septum-like structures in diatom genera

The ultrastructure of Diatomella balfouriana Greville collected from Île de la Possession, a sub-Antarctic island in the Crozet Archipelago, was studied using high-resolution scanning and transmission electron microscopy. The alveolate striae of the genus are subdivided by small vimines, presenting a unique feature never observed before in other diatom genera. The most striking feature of the genus is the presence of the septum-like structures projecting from the girdle bands. The term scalariform valvocopula is introduced for these structures to discriminate them from the septa present in several araphid and (at least one) raphid genera. The taxonomic position of the genus within the family Pinnulariaceae D.G. Mann is discussed based on the study of the structure of the alveolate striae.

Is palynology a credible climate proxy in the Subantarctic?

Pollen and spore analysis is the most successfully used palaeobotanical discipline for reconstructing Holocene vegetation and climate history throughout the world. Subantarctic islands are very specific areas. They are located in the circum-Antarctic Southern Ocean in latitudes that are under strong influence of the southern westerly winds, and are characterised by a treeless, phanerogam-poor flora. Palynological research on many of these islands has resulted in diverging conclusions about how to infer climate history from pollen data. In this study we compare pollen data with macrofossil data on the one hand, and the palaeoenvironmental history based on a multiproxy record on the other hand, of two peat sequences from two different subantarctic islands, South Georgia and Île de la Possession (Îles Crozet). We conclude that palynology must be used with caution as a proxy for climate change on these islands, especially when no other proxy data are available. The upland–lowland principle, as it has been applied in pollen studies in the South Indian Ocean islands, results in erroneous conclusions about climate change on Île de la Possession. More palaeoclimatic multiproxy and pollen studies, in combination with pollen–vegetation relationship studies, can, however, contribute to a more reliable model of how to interpret pollen data in the Subantarctic. We want to stress that our conclusions are only based on Holocene records. Consequently, the question remains if palynology can be used as a palaeoclimatic proxy when climatic changes were more pronounced such as during the last glacial–interglacial transition.

Cavernosa kapitiana (Bacillariophyceae): biogeography and morphology of the different life cycle stages

The monospecific diatom genus Cavernosa is known from only two locations: Kapiti Island off the west coast of New Zealand and Ile de la Possession, Crozet Archipelago, in the southern Indian Ocean. Cavernosa kapitiana Stidolph is a chain-forming diatom with cylindrical frustules having an elongated valve mantle. We provide a description of the different life-cycle stages (normal frustules, globular initial cells, bell-shaped initial cells, first daughter cells of initial cells) of C. kapitiana based on examination of new material from Ile de la Possession and material from the type locality on Kapiti Island. The most remarkable morphological features include the complex valve face structure composed of pores, granules and ridges, the subdivision of the valve interior into marginal caverns, the complex structure of the mantle and girdle, and the presence and morphology of rimoportulae. The study concludes with an emended species description of C. kapitiana.

Subantarctic peatlands and their potential as palaeoenvironmental and palaeoclimatic archives

Subantarctic islands are located within the Antarctic Circumpolar Current and the southern westerly wind belt, the latter called Southern Westerlies, making them unique terrestrial archives to investigate past changes in oceanic and atmospheric circulation patterns in the southern mid-latitudes. The islands are characterised by a treeless, phanerogam-poor flora in which bryophytes are of major importance. Several peat-based Holocene palaeoenvironmental and palaeoclimatic studies have recently been published for South Georgia and Ile de la Possession (Iles Crozet). A range of techniques have been used in these studies, mainly plant macrofossil analysis, but also analyses of diatoms, pollen and non-pollen microfossils, geochemical and geomagnetic measurements. The records are chronologically constrained by radiocarbon dating. This paper brings together these data in order to give an overview of the Subantarctic peat-based palaeoclimatic records. A new plant macrofossil record for the island of South Georgia is added. Evidence for millennial scale Holocene climate variability was found for both islands of which the most striking one occurred in the late Holocene. However, within the uncertainty of the age/depth models, the timing for this climate shift to wetter and/or colder conditions on South Georgia and windier/wetter conditions on Ile de la Possession is different for both islands. Ile de la Possession (Iles Crozet) seems to follow the Northern Hemisphere climate evolution as the event was dated to ∼2800 cal BP, a well-known climate event present in many peat-based records in north-western Europe. In contrast, the South Georgian late Holocene climate records reveal a shift around ∼2200–2000 cal BP.

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.