Modern and fossil terrestrial and freshwater habitats on subantarctic Macquarie Island

Macquarie Island is a small subantarctic island situated 1130 km south-south east of Tasmania. It is isolated from any land mass and experiences harsh climatic conditions.

Ten palaeolake sites are known from Macquarie Island. Five were studied in detail to provide information on the Late Quaternary climates of the region, employing diatoms (Bacillariophyta) as the main interpretive tool. To this end, the diatom associations from several modem habitats were examined and catalogued. The five palaeolake sites were located in the north west of the island. They are Palaeolake Half Moon, Palaeolake Cascade, Palaeolake Eagle, Palaeolake Emerald and Palaeolake Cormorant. The modem habitats examined were creeks, mires, soil, feldmark, lichen and nutrient rich areas. A companion study of modem lakes is currently in progress. Eleven major diatom associations were identified from the terrestrial, mire and palaeolake samples.

One hundred and eighty one taxa of diatoms were identified from the modem and fossil samples. The majority of the species found were cosmopolitan, with approximately 10% found only in the subantarctic and/or the Antarctic.

The palaeolake sediments were dated at between 12 900 RC y BP and 3580 RC y BP. Three of the palaeolakes exhibited little change in diatom associations or in sediments over time. These have been interpreted as deep, oligotrophic lakes similar to some modem lakes on the island today. Two of the palaeolakes showed major changes in both sediments and diatom associations. These changes have been interpreted as reflecting a change in the climate of Macquarie Island, with a drier period between 5000 and 3500 y BP.