Since the discovery of glacial features on sub-Antarctic Marion Island, the character and extent of a historic glacial period have remained an important research focus for earth science investigations. Previous glacial reconstructions were limited to mostly pre-GPS field observations and pre-digital mapping through a Geographic Information System. With the aid of GPS field mapping, high-resolution satellite imagery and a digital surface model with a 1 × 1 m cell resolution, this paper provides a comprehensive, geo-rectified spatial geodatabase and map of Marion Island's glacial geomorphology. The geodatabase includes an inventory of glacial erosional (e.g. striations) and depositional (e.g. moraines) features compiled from existing records as well as new features mapped from recent field observations. The final map and the geodatabase, which is downloadable as ESRI layerpackage files, will aid future field investigations and modelling applications to understand Marion Island's Quaternary landscape evolution and post-glacial ecological succession.

The cessation of seal harvesting has prompted a recovery of previously decimated fur seal (Arctocephalus gazella and A. tropicalis) populations across the Southern Ocean region.Although the associated increase in seal-related soil disturbance is known to impact indigenous vegetation, the effect of increasing fur seal numbers on exotic plant species is not yet clear. Here, we compare plant species composition and cover between 26 sites with 2 high fur seal impact paired with nearby control sites on sub-Antarctic Marion Island. Sealaffected sites had a significantly higher number and cover of exotic plants, specifically of the widespread sub-Antarctic invaders, Poa annua and Sagina procumbens, than control sites. Furthermore, some of the native species, most notably the disturbance-sensitive species, Blechnum penna-marina, were significantly less abundant in seal-affected sites compared to controls. We propose that this is a result of both physical trampling, which opens up niches for exotics by damaging natives, and nutrient enrichment of the soils, giving exotic species a competitive advantage over natives. While other studies have noticed associations between exotic plant species and indigenous animal disturbance, this is, to the best of our knowledge, the first study to empirically show that the successful recovery of fur seal populations can have undesirable side-effects such as the enhanced persistence of exotic plant species. We recommend that alien plant management plans specifically include areas of increased animal disturbance into their programmes.

No abstract

Marion Island is a peak of a shield volcano located in the southern Indian Ocean. Annexed by South Africa in 1948, the island has been strategically important for the collection of climatological data and marine and terrestrial research in a vast, oceanic region of the globe. This paper reviews the series of earth science programmes on Marion Island over the last 25 years, provides a synthesis of the research outcomes and demonstrates how field and laboratory methods have developed over time. Marion Island has, globally, one of the most active soil frost environments in a distinctive periglacial setting and understanding this contemporary periglacial environment has been a key objective of the research programmes., Geomorphological processes have important implications for local ecosystem functioning and define the regional and global significance for diurnal soil frost environments and climate change. The review presented here shows that keeping abreast with the advancements of appropriate methodologies and technologies and the continued employment of a mix of new 2 and established methods has driven the earth science research in this unique island environment. A series of short vignettes present the most recent advancements on old key questions and indicate that new techniques continuously challenges us to re-evaluate the most basic of assumptions that exist within our research.

Volcanological maps of the sub-Antarctic Prince Edward Islands were first published in 1968, with a revised surface geology map of Marion Island produced in 2006. These maps have been widely used in terrestrial studies on the Prince Edward Islands but they have limitations in spatial accuracy and detail. Using high-resolution satellite imagery and digital elevation data, more spatially accurate data for both Prince Edward and Marion Island’s surface geology are presented here. In particular, Marion Island’s volcanology on the western coast, including the 1980s lava flow, and the newly exposed Central Highland following the disappearance of extensive ice and snow cover is mapped with greater detail and verified through field observations. The spatial data are downloadable as ESRI layer packages, which can assist in future investigations of island biotic-abiotic processes and interactions and enable improvements in spatial modelling. In addition, this paper highlights geological features and specimens from the Prince Edward Islands as unique examples of geodiversity in a South African context. An overview of these features are provided in terms of their geoheritage value to enable a more comprehensive geoconservation strategy be incorporated into the Prince Edward Islands Management Plan.