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The study of climate mechanisms in the Southern Hemisphere during the Holocene remains an area of active research that lacks the spatial and temporal connectivity characteristic of Northern Hemisphere research. The subtropical/temperate climate transition zone of eastern Australia provides a unique location to investigate long-term environmental changes during the Holocene. Lake Jennings on Fraser Island was used to investigate climate change in this transition zone using palaeolimnological techniques. The beginning of the Lake Jennings record (~6000 to 3500 cal. yBP), is characterised by fluctuations in geochemical signals, an abundance of sponge spicules, and a lack of diatom species. Results suggest gradually increasing precipitation and water depth, which affect nutrient cycling. However, the biological functioning of the lake is difficult to interpret due to the absence of diatoms, possibly a result of turbidity, dissolution and/or predation by freshwater sponges. During the late Holocene, ~3500 cal. yBP to present, precipitation and water depth of the lake decreases to present day levels. Within this section of the core nutrient cycling changes, as indicated by the geochemical results, and a series of more intense wet and dry events took place before stabilising at present day levels. Other palaeoecological studies within the Southern Hemisphere have noted changes in geochemical and biological attributes within similar latitudes, confirming the notion of climate forced environmental change in aquatic ecosystems. This continuous ~6000 year record from Lake Jennings shows distinct changes in aquatic communities, confirming a trend of drying in subtropical eastern Australia through the late Holocene. [ABSTRACT FROM AUTHOR]

Multiproxies of past environmental conditions, comprising 53 sediment samples analysed for their lithostratigraphic properties (mainly their charcoal, phytoliths and pollen contents) from an AMS 14C-dated sequence of sediments accumulating at Guangfulin, Yangtze delta, are presented. The oldest sediments recovered date to the Lateglacial when a mosaic of mixed (conifer-deciduous) temperate forest and wetland vegetation characterized the study area. The Lateglacial-Holocene transition and much of the early Holocene record to c. 7400 yr BP appears to be missing from the sequence. The earliest evidence possibly representing human activities in the study area (the remains of cereals and indicators of forest) date to c. 7000 yr BP. A large increase in macrocharcoal remains c. 4700 yr BP is a more certain indication of human activities close to the study site, and may indicate the first occupation of what is now the location of a major archaeological excavation at Guangfulin. Technological changes during the Eastern Zhou Dynasty (770-221 BC) may be responsible for an increased abundance of rice (Oryza sp.), and possibly also foxtail or Chinese millet (Setaria italica), detected in the Guangfulin record after c. 2400 yr BP. An abrupt sedimentary change at c. 4000 yr BP may represent a short-lived episode of catchment instability. Aside from this, the sediment record from Guangfulin contains no evidence of dramatic environmental changes that could have led to a major decline in agricultural productivity c. 4000 yr BP, as has been suggested for the lower Yangtze by some researchers, who associate this with the cultural transition from Liangzhu to Maqiao. The findings do, however, add weight to the argument that developments in rice-based agriculture on the Yangtze delta varied both spatially and temporally. [ABSTRACT FROM AUTHOR]

Climate change is impacting global surface water resources, increasing the need for a deeper understanding of the interaction between climate and biological diversity. This is particularly the case in the Southern Hemisphere sub-tropics, where little information exists on the aquatic biota response to climate variations. Palaeolimnological techniques, in particular the use of diatoms, are well established and can significantly contribute to the understanding of climatic variability and the impacts that change in climate have on aquatic ecosystems. A sediment core from Lake McKenzie, Fraser Island (Australia), was used to investigate interactions between climate influences and aquatic ecosystems. This study utilises a combination of proxies including biological (diatom), geochemical and chronological techniques to investigate long-term aquatic changes within the perched-dune lake. A combination of (210)Pb and AMS (14)C dates showed that the retrieved sediment represented a history of ca. 37,000 cal.yBP. The sedimentation rate in Lake McKenzie is very low, ranging on average from 0.11 mm to 0.26 mm per year. A sediment hiatus was observed between ca. 18,300 and 14,000 cal.yBP suggesting a period of dry conditions at the site. The diatom record shows little variability over the period of record, with benthic, freshwater acidic tolerant species dominating. Relative abundance of planktonic species and geochemical results indicates a period of increased water depth and lake productivity in the early Holocene and a gradual decrease in effective precipitation throughout the Holocene. Results from this study not only support earlier work conducted on Fraser Island using pollen reconstructions but also demonstrate that diatom community diversity has been relatively consistent throughout the Holocene and late Pleistocene with only minor cyclical fluctuation evident. This record is consistent with the few other aquatic palaeoecological records from the Southern Hemisphere sub-tropics., (© 2013.)