• Energy Research

To achieve robust simulations of past and future climate and their effect on aquatic biota, it is desirable to integrate results from palaeolimnology, contemporary monitoring and process modelling. Here we analyse over 15 years of water quality monitoring data from three lakes, Purrumbete, Colac and Bullen Merri from Western Victoria, Australia and their relationship to climate. In the context of a large number of limnological and palaeoenvironmental studies from the region, we seek to refine understanding of the primary forcing mechanisms that explain present, past and potentially future water quality variability in the lakes. Our analysis shows that there are strong relationships between climate and water quality in these lakes of varied size and salinity (average conductivity range 740–14,000 μS cm−1). The strongest climate–water quality relationship exists between air and water temperature, particular during the colder months. Strong relationships also exist with air temperature and other parameters, most notably nutrient concentrations. Effective precipitation also appears to exert a strong influence on water quality in these lakes. This influence is, by contrast with the influence of air temperature, less direct. Nevertheless, these lakes of varying salt concentration exhibit a coherent pattern of conductivity response to variation in effective precipitation, particularly during times of high moisture stress.

Abstract Climates of the last two millennia have been the focus of numerous studies due to the availability of high-resolution palaeoclimate records and the occurrence of divergent periods of climate, commonly referred to as the ‘Medieval Climatic Anomaly’ and ‘The Little Ice Age’. The majority of these studies are centred in the Northern Hemisphere and, in comparison, the Southern Hemisphere is relatively under-studied. In Australia, there are few high-resolution, palaeoclimate studies spanning a millennium or more and, consequently, knowledge of long-term natural climate variability is limited for much of the continent. South-eastern Australia, which recently experienced a severe, decade-long drought, is one such region. Results are presented of investigations from two crater lakes in the south-east of mainland Australia. Fluctuations in lake-water conductivity, a proxy for effective moisture, are reconstructed at sub-decadal resolution over the past 1500 years using a statistically robust, diatom-conductivity transfer function. These data are interpreted in conjunction with diatom autecology. The records display coherent patterns of change at centennial scale, signifying that both lakes responded to regional-scale climate forcing, though the nature of that response varied between sites due to differing lake morphometry. Both sites provide evidence for a multi-decadal drought, commencing ca 650 AD, and a period of variable climate between ca 850 and 1400 AD. From ca 1400–1880 AD, coincident with the timing of the ‘Little Ice Age’, climates of the region are characterised by high effective moisture and a marked reduction in inter-decadal variability. The records provide context for climates of the historical period and reveal the potential for more extreme droughts and more variable climate than that experienced since European settlement of the region ca 170 years ago.

The datasets comprise stable isotope, pollen abundance and lipid biomarker data that we analysed in sediments from the Fern Gully Lagoon wetland (Latitude 27.4174°S, Longitude 153.4600°E, elevation of 39 m above sea level), North Stradbroke Island (also known as Minjerribah), Australia. Two overlapping nine-metre cores were obtained in April 2015 using a modified Livingstone-Bolivia square-rod piston-corer. Cores were aligned using CPLSlot sequence plotting software. The sedimentary record spans the last ~210 kyrs. We analysed total organic carbon and total nitrogen contents of the sediments. We also determined the d13C and d15N composition of the organic matter present in the sediments. Errors of these parameters were also included. The analyses werer undertaken on a EuroVector EuroEA elemental analyser, in-line with a Nu Instruments Nu Horizon continuous flow isotope ratio mass spectrometer (EA-IRMS). Pollen abundance data were also included as relative percentages of rainforest vs herbs and grasses vs sclerophyll vegetation relative to the total terrestrial pollen found in each sample. Charcoal content was also included. Lipid biomarker data comprise key paramters such as the carbon preference index (CPI), average chain length of C27-C33 n-alkanes with (ACL), Paq index, concentration of C31 ab-hopane and as ratio with major plant sterols [C31hopane/(sitosterol+stanol+stigmasterol+stanol)] and GDGT-based temperature and pH indices and on their basis estimated temperature and pH values of the studied samples. The biomarker extracts and fractions were analysed by gas chromatography mass spectrometry (GC-MS). This study is an extension and evaluation of previous work reconstructing regional interglacial climate history at Fern Gully Lagoon (Kemp et al., 2020, 2021), seeking to understand the influence of temperature and wetland surface area on the palaeoclimate record. As previous climate inferences include a degree of uncertainty due to the possible human impact on terrestrial vegetation, we utilise a wide range of climate proxies preserved in this wetland to characterise sources of organic matter and determine vegetation water stress. In addition, we quantified mean annual air temperatures (MAAT), potentially allowing temperature-driven vegetation changes to be identified. To reconstruct changes in wetland surface area resulting from increased drying, we use a combination of simple basin morphology and the age-depth model to study the impact on evaporation-driven vegetation moisture stress on wetland size.

The datasets comprise stable isotope, pollen abundance and lipid biomarker data that we analysed in sediments from the Fern Gully Lagoon wetland (Latitude 27.4174°S, Longitude 153.4600°E, elevation of 39 m above sea level), North Stradbroke Island (also known as Minjerribah), Australia. Two overlapping nine-metre cores were obtained in April 2015 using a modified Livingstone-Bolivia square-rod piston-corer. Cores were aligned using CPLSlot sequence plotting software. The sedimentary record spans the last ~210 kyrs. We analysed total organic carbon and total nitrogen contents of the sediments. We also determined the d13C and d15N composition of the organic matter present in the sediments. Errors of these parameters were also included. The analyses werer undertaken on a EuroVector EuroEA elemental analyser, in-line with a Nu Instruments Nu Horizon continuous flow isotope ratio mass spectrometer (EA-IRMS). Pollen abundance data were also included as relative percentages of rainforest vs herbs and grasses vs sclerophyll vegetation relative to the total terrestrial pollen found in each sample. Charcoal content was also included. Lipid biomarker data comprise key paramters such as the carbon preference index (CPI), average chain length of C27-C33 n-alkanes with (ACL), Paq index, concentration of C31 ab-hopane and as ratio with major plant sterols [C31hopane/(sitosterol+stanol+stigmasterol+stanol)] and GDGT-based temperature and pH indices and on their basis estimated temperature and pH values of the studied samples. The biomarker extracts and fractions were analysed by gas chromatography mass spectrometry (GC-MS). This study is an extension and evaluation of previous work reconstructing regional interglacial climate history at Fern Gully Lagoon (Kemp et al., 2020, 2021), seeking to understand the influence of temperature and wetland surface area on the palaeoclimate record. As previous climate inferences include a degree of uncertainty due to the possible human impact on terrestrial vegetation, we utilise a wide range of climate proxies preserved in this wetland to characterise sources of organic matter and determine vegetation water stress. In addition, we quantified mean annual air temperatures (MAAT), potentially allowing temperature-driven vegetation changes to be identified. To reconstruct changes in wetland surface area resulting from increased drying, we use a combination of simple basin morphology and the age-depth model to study the impact on evaporation-driven vegetation moisture stress on wetland size.

Summary 1 The long-term impact of changes in land use, fire and climate on species diversity in Australia are only just beginning to be understood. We combined fine-resolution palaeoecological proxies for terrestrial and aquatic ecosystems to investigate the responses of a tropical rain forest catchment over the last 700 years. 2 Sediment cores were sampled at 1-cm intervals to a depth of 100 cm from Lake Euramoo on the Atherton Tableland of north-east Queensland, dated and analysed for pollen, charcoal, diatom, chironomid and inorganic content. 3 The pollen and charcoal record shows a rapid loss of forest diversity (particularly the long-lived taxa Agathis and Podocarpus) and increased burning coinciding with the arrival of European settlers. The aquatic environment is also subject to rapid changes at this time, with a possible increase in pH and subsequent shifts in local algal and insect communities. This event was outside the historic range of variability in both rain forest and aquatic communities. 4 The present mosaic of vegetation types is a complex function of environmental changes operating across a range of spatial and temporal scales: millennial climate change, short-term climatic variations associated with El Nino events and, most significantly, a shift from indigenous to ‘European’ land-use practices, including clearance and burning activities associated with the timber and farming industry between about ad 1880 and 1920. 5 The establishment of a World Heritage reserve around the lake catchment and the suppression of fire over the last 50 years have not yet restored the terrestrial or aquatic ecosystem to its pre-European state and are unlikely to, given the current predictions of future climate change. This supports the notion that ecological and climate thresholds are not necessarily the same, and that the effects of crossing them are not necessarily reversible. Retrospective studies of the historic range of variability within small catchments can provide an understanding of the limits of natural and human-induced variability that can inform management decisions and resource planning.

The management of the water resources of the Murray-Darling Basin (MDB) has long been contested, and the effects of the recent Millennium drought and subsequent flooding events have generated acute contests over the appropriate allocation of water supplies to agricultural, domestic and environmental uses. This water-availability crisis has driven demand for improved knowledge of climate change trends, cycles of variability, the range of historical climates experienced by natural systems and the ecological health of the system relative to a past benchmark. A considerable volume of research on the past climates of southeastern Australia has been produced over recent decades, but much of this work has focused on longer geological time-scales, and is of low temporal resolution. Less evidence has been generated of recent climate change at the level of resolution that accesses the cycles of change relevant to management. Intra-decadal and near-annual resolution (high-resolution) records do exist and provide evi...

The datasets comprise stable isotope, pollen abundance and lipid biomarker data that we analysed in sediments from the Fern Gully Lagoon wetland (Latitude 27.4174°S, Longitude 153.4600°E, elevation of 39 m above sea level), North Stradbroke Island (also known as Minjerribah), Australia. Two overlapping nine-metre cores were obtained in April 2015 using a modified Livingstone-Bolivia square-rod piston-corer. Cores were aligned using CPLSlot sequence plotting software. The sedimentary record spans the last ~210 kyrs. We analysed total organic carbon and total nitrogen contents of the sediments. We also determined the d13C and d15N composition of the organic matter present in the sediments. Errors of these parameters were also included. The analyses werer undertaken on a EuroVector EuroEA elemental analyser, in-line with a Nu Instruments Nu Horizon continuous flow isotope ratio mass spectrometer (EA-IRMS). Pollen abundance data were also included as relative percentages of rainforest vs herbs and grasses vs sclerophyll vegetation relative to the total terrestrial pollen found in each sample. Charcoal content was also included. Lipid biomarker data comprise key paramters such as the carbon preference index (CPI), average chain length of C27-C33 n-alkanes with (ACL), Paq index, concentration of C31 ab-hopane and as ratio with major plant sterols [C31hopane/(sitosterol+stanol+stigmasterol+stanol)] and GDGT-based temperature and pH indices and on their basis estimated temperature and pH values of the studied samples. The biomarker extracts and fractions were analysed by gas chromatography mass spectrometry (GC-MS). This study is an extension and evaluation of previous work reconstructing regional interglacial climate history at Fern Gully Lagoon (Kemp et al., 2020, 2021), seeking to understand the influence of temperature and wetland surface area on the palaeoclimate record. As previous climate inferences include a degree of uncertainty due to the possible human impact on terrestrial vegetation, we utilise a wide range of climate proxies preserved in this wetland to characterise sources of organic matter and determine vegetation water stress. In addition, we quantified mean annual air temperatures (MAAT), potentially allowing temperature-driven vegetation changes to be identified. To reconstruct changes in wetland surface area resulting from increased drying, we use a combination of simple basin morphology and the age-depth model to study the impact on evaporation-driven vegetation moisture stress on wetland size.

Abstract Sedimentological, limnological and palynological analyses of a sediment core from a lowland site in West-Java, Indonesia, provide a detailed palaeoenvironmental record for the Late Glacial and the Holocene. The record suggests open vegetation under inferred drier climatic conditions for the Late Glacial. However, there is no unequivocal evidence for cooler conditions at this time. The onset of the Holocene coincides with a change to more humid climatic conditions, with the development of a fern-rich closed forest vegetation type. Dramatic changes in diatom community composition provide a striking record of habitat change associated with lake shallowing, but this process appears to be a result of basin in-filling rather than variations in precipitation/evaporation balance associated with climatic fluctuations. Evidence for human impact on the vegetation development is restricted to the last few hundred years.