Most studies on the sedimentary diatom assemblages of Lake Baikal have either focused on the very... more Most studies on the sedimentary diatom assemblages of Lake Baikal have either focused on the very recent past or have been carried out at low sampling resolution on sequences that encompass several glacial/interglacial cycles. Here we present the progress made so far on the high-resolution diatoms analysis of the Holocene records found in three sites, one located in the North basin (Continent Ridge), and two located in the South basin (Posolsky Bank and Vydrino Shoulder). Samples are being analysed at a 5 mm resolution throughout the Holocene record for Vydrino Shoulder and every 1 cm for Posolsky Bank. At Continent Ridge, diatom analysis was carried out every 2 mm on the uppermost 20 cm of the core, while samples for the rest of the Holocene record were analysed every 1 cm only. We expect these to reflect a decadal to centennial resolution. From these three sequences, a very large number of diatom taxa (about 500) have been identified. In all three sequences, endemic planktonic dia...
The ratios of stable carbon and oxygen isotopes are useful palaeoclimatic indicators as they are ... more The ratios of stable carbon and oxygen isotopes are useful palaeoclimatic indicators as they are often governed by climatic factors. This study investigates carbon isotopes of organic matter and oxygen isotopes from biogenic silica of a Holocene profile from Vydrino Shoulder, Lake Baikal. The organic d13C and C/N values are predominantly in the range described for C3 algae. Shifts to higher C/N values can be interpreted as increased inwash from catchment terrestrial sources while lower values indicate increased aquatic productivity. Shifts in d13C can be interpreted in many ways: heavier d13C can be a greater influence of C4 shrubs ad grasses in the catchment indicating climatic cooling. However, heavier values can also result from increased aquatic productivity, decomposition of the organic matter and atmospheric CO2 changes. Values will be members between endmember sources of carbon and interpretation of the record will be aided by understanding of these carbon sources to the lake...
It is important to identify the teleconnections between high latitude forcing and tropical monsoo... more It is important to identify the teleconnections between high latitude forcing and tropical monsoonal circulation in order to understand climate change in East Africa during the Plio-Pleistocene. Here we present a record of aeolian dust transport to the Arabian Sea between approximately 2.9 and 2.3 million years ago (Ma), constructed from the high-resolution XRF scanning of sediment cores from ODP Sites 721 and 722. Variations in the delivery of aeolian dust to the Arabian Sea, reflected in normalised flux of titanium, show that monsoonal circulation prior to 2.6 Ma, and after 2.5 Ma, was highly variable and primarily driven by orbitally-forced changes in tropical summer insolation, strongly modulated by the 400,000 year cycle of orbital eccentricity. This is confirmed by the presence of lakes in the East African Rift Valley during key eccentricity maxima. The dust record is coupled with the analysis of a well-dated series of diatomite units from the Baringo-Bogoria Basin which docum...
Here we present the first dataset to couple oxygen and silicon isotopes determined on diatom sili... more Here we present the first dataset to couple oxygen and silicon isotopes determined on diatom silica from a lake sedimentary profile. Samples have been extracted from a sediment core spanning most of the Holocene ( ∼ 9500 years) collected in the south- ern basin of Lake Baikal, the oldest and deepest freshwater lake in the world. After a sequence of oxidative and acid leaching, sieving and gravity settling, the cleaned opaline samples comprising more than 90% diatoms have been analysed by fluorina- tion - IRMS for oxygen isotopes. An additional NaOH leaching step followed by co- precipitation was carried out prior to the Si isotopic analyses by MC-ICP-MS. Oxygen isotopic compositions of Lake Baikal diatoms have been found to be linked to prevail- ing climatic conditions and resulting balance between southern summer precipitation and northern snowmelt. Diatom silicon isotopic compositions in such a large lake as Baikal are expected to be mostly controlled by the diatoms Si relative ut...
Carbon isotope ratio (d 13 C org ) values of organic matter in lake sediments are commonly used t... more Carbon isotope ratio (d 13 C org ) values of organic matter in lake sediments are commonly used to reconstruct environmental change, but the factors which influence change are varied and complex. Here we report d 13 C values for sediments from Erlongwan maar lake in northeast China. In this record, changes in d 13 C cannot be explained by simple changes in aquatic productivity. Instead, values were likely influenced by differences in the ratio between planktonic and benthic algae, as indicated by the remains of diatoms. This is because the variation of d 13 C org in algae from different habitats is controlled by the thickness of the diffusive boundary layer, which is dependent on the turbulence of the water. Compared with benthic algae, which grow in relatively still water, pelagic algae are exposed to greater water movement. This is known to dramatically reduce the thickness of the boundary layer and was found to cause even more severe d 13 C depletion. In Erlongwan maar lake, low values were linked to the dominance of planktonic diatoms during the period commonly known as the Medieval Warm Period. Values gradually increased with the onset of the Little Ice Age, which we interpret as being driven by an increase in the proportion of benthic taxa, due to effect of the colder climate. The increase in planktonic diatoms at the end of the Little Ice Age, linked to higher temperature and a reduction in ice cover, resulted in a further decline in d 13 C org .
Humanity faces a major global challenge in achieving wellbeing for all, while simultaneously ensu... more Humanity faces a major global challenge in achieving wellbeing for all, while simultaneously ensuring that the biophysical processes and ecosystem services that underpin wellbeing are exploited within scientifically informed boundaries of sustainability. We propose a framework for defining the safe and just operating space for humanity that integrates social wellbeing into the original planetary boundaries concept (Rockströ m et al., 2009a,b) for application at regional scales. We argue that such a framework can: (1) increase the policy impact of the boundaries concept as most governance takes place at the regional rather than planetary scale; (2) contribute to the understanding and dissemination of complexity thinking throughout governance and policy-making; (3) act as a powerful metaphor and communication tool for regional equity and sustainability. We demonstrate the approach in two rural Chinese localities where we define the safe and just operating space that lies between an environmental ceiling and a social foundation from analysis of time series drawn from monitored and palaeoecological data, and from social survey statistics respectively. Agricultural intensification has led to poverty reduction, though not eradicated it, but at the expense of environmental degradation. Currently, the environmental ceiling is exceeded for degraded water quality at both localities even though the least well-met social standards are for available piped water and sanitation. The conjunction of these social needs and environmental constraints around the issue of water access and quality illustrates the broader value of the safe and just operating space approach for sustainable development.
Past environmental changes based on diatom relative abundances have been inferred from the maar L... more Past environmental changes based on diatom relative abundances have been inferred from the maar Lake Erlongwan in northeast China. The limnology of Lake Erlongwan is affected by the strongly seasonal regional climate. The composition of diatom assemblages, in turn, responds to changes in the seasonal duration of ice cover in winter, water-column turnover in spring and autumn, and thermal stratification in summer. Statistical analysis of the sedimentary diatom assemblages reveals three significant stratigraphic zones over the past 1000 yr. The highest abundance of the planktonic species Discostella species occurs between AD 1050 and 1400 and suggests an annual ice-free period of long duration and well-developed summer stratification of the water column. This planktonic diatom peak between ca. AD 1150 and 1200 suggests that this period was the warmest over the past 1000 yr. The interval between AD 1400 and 1800 is marked by a decline in planktonic diatoms and suggests shorter duration of the ice-free season, weaker water stratification and possibly generally cold conditions. After AD 1800 relative abundances of planktonic diatoms, including Puncticulata praetermissa and Asterionella formosa, increase again, which indicates lengthening of the duration of the annual ice-free period and a stronger overturn of the water column. All these data imply that the pattern of the seasons is different between the MWP and the 20th century.
A high-resolution (wevery 20 y) pollen and charcoal record from Erlongwan maar lake (EML) documen... more A high-resolution (wevery 20 y) pollen and charcoal record from Erlongwan maar lake (EML) documents the vegetation history and fire activity of the Long Gang region (northeast China) over the past millennium. The ageedepth model is based on 137 Cs, 210 Pb measurements, and one calibrated 14 C-AMS date at the base of the core. For much of the record, vegetation was dominated by a mixed coniferhardwood forest. Pollen and charcoal concentrations reveal considerable variability during the past 1000 years. Between 980 and 1500 AD both pollen and charcoal reached maximum concentrations (w1100 AD and 1300 AD respectively). The high pollen concentration was indicative of prevailing moist conditions during the period commonly referred to as the Medieval Climatic Anomaly (MCA). The high concentration of charcoal indicated high frequency and intensity of wildfire during the MCA, probably linked to high biomass productivity and less snow in winter. Between 1500 and 1850 AD both pollen and charcoal concentrations were low, indicative of colder winters with higher snowfall, relative drier summers and less intensive wildfire, coincidence with the cold period commonly known as the Little Ice Age (LIA). During 1900e1950 AD year, the highest relative abundance of Artemisia and the lowest abundance of Pinus together with high concentration of charcoal indicated strong human activity. The pollen data are in broad agreement with a previous study from an adjacent lake, indicating regional rather than localized human impact.
Reconstructing climatic variability over the past c. 2 ka years is recognised as a key PAGES time... more Reconstructing climatic variability over the past c. 2 ka years is recognised as a key PAGES timeframe (focus 2). However few high-resolution records exist from the climate sensitive region of N) China which receives the majority of its precipitation from the east Asian summer monsoon (EASM). Interactions between the EASM and the global climate system have great resonance. Such examples include how the EASM responded to changes in climate over the documented eg" Medieval Warm Period"(c. AD 900-1300)," ...
High-resolution TECHNICAP sediment traps have been deployed in Lake Baikal since 1996. Results of... more High-resolution TECHNICAP sediment traps have been deployed in Lake Baikal since 1996. Results of these experiments show distinct seasonal differences in particle flux, ranging from a few mg m-2d-1 to several g m-2d-1. Analyses of trap material show that removal of particles is very fast and efficient. Downward transport through the 1400 m deep water column reaches velocities of up
Spatial and temporal patterns of spheroidal carbonaceous particles (SCP) extracted from lake sedi... more Spatial and temporal patterns of spheroidal carbonaceous particles (SCP) extracted from lake sediments provide an unambiguous record of the distributions of fossil-fuel derived pollutants. When applied to sediment cores taken from Lake Baikal spatial patterns show good agreement with the distribution of industry, with the highest concentrations found in the southern basin nearest to Irkutsk. SCP were found to occur in all cores from all areas of the lake in contrast to metal results where anthropogenically enhanced deposition was only demonstrable in the southern basin. SCP distribution within the sediments of Lake Baikal is seen to be distinctly regional and therefore long distance transport is not thought to be an important pathway for these pollutants. Temporal patterns of SCP show trends that reflect the development of industry in the area since the 1940s. Settling rates in the 1600 m water column suggest that the SCP sediment record may be approximately an order of magnitude more sensitive to depositional changes than that of trace metals.
Freshwater aquaculture is an important source of protein worldwide. Over-exploitation of fisherie... more Freshwater aquaculture is an important source of protein worldwide. Over-exploitation of fisheries can, however, add severely to pressures on ecosystem functioning and services. In Southeast Asia, aquaculture in freshwater lakes contributes significantly to the economy and to reductions in poverty and nutritional insecurity. However, overstocking and excessive feeding of fish can lead to a degradation of affected water bodies, manifest as eutrophication, toxic algal blooms, losses of biodiversity and amenity, anoxia and, in extreme cases, collapse of fisheries. Projected increased warming and storminess associated with global climate change are likely to magnify existing problems. Matching levels of aquaculture production with ecological carrying capacity is therefore likely to become increasingly challenging, requiring levels of data and understanding that are rarely available, a problem that is impossible to rectify in the short term using standard limnological approaches. This paper reviews the development of freshwater aquaculture in the Philippines, associated environmental impacts, and relevant environmental regulations and regulatory bodies. The potential role of palaeolimnology, a science that is relatively under-utilised in the tropics generally and in tropical Asia in particular, in complementing extant datasets, including monitoring records, is highlighted through reference to a preliminary study at Lake Mohicap. Lake Mohicap currently supports aquaculture and is one of a cluster of seven volcanic crater lakes on Luzon, the largest of the archipelago of islands forming the Philippines.
We present a new palaeoenvironmental record of hydrological variability in Lake Baikal, based on ... more We present a new palaeoenvironmental record of hydrological variability in Lake Baikal, based on re-modelled d 18 O diatom values of diatom silica (d 18 O modelled ), where the residual contaminants are identified and compensated for using electron optical imaging and whole-sample geochemistry. d 18 O modelled interpretations are based on the balance between rivers with high d 18 O values and rivers with low d 18 O values. Isotopic variability is related to latitudinal differences in precipitation which feed these rivers. The d 18 O modelled record suggests that rather moist conditions prevailed in the Lake Baikal region during the latter stages of the Younger Dryas. Throughout the Holocene, episodes of low d 18 O modelled values are, in general, in good agreement with increases in percentage haematite-stained grains in North Atlantic sediments (indicative of ice-rafted debris events). Rivers with southerly catchments dominate fluvial input especially between c. 3.3 and 2 cal ka BP, concurrent with high precipitation in the Lake Baikal region.
Detrital grain contamination in a diatom sample can considerably influence the 18 O diatom signal... more Detrital grain contamination in a diatom sample can considerably influence the 18 O diatom signal. In order to obtain a meaningful signal, pure samples must be used. This can be achieved via a series of cleaning stages including organic and carbonate material removal, sieving, differential settling and heavy liquid separation. The method described here works best for sediments with >20% diatom content. Based on testing various clean-up methods, we propose a sequence of four clean-up stages to produce pure diatom samples from a range of lake sediments types starting with a few grams of sediment. The diatom content and the oxygen isotope composition of the samples at each stage were measured in order to assess the effect of differential amounts of contamination. Results show that a four stage clean-up is necessary to produce clean diatom samples and that contamination by silt and clay causes lower 18 O values.
Most studies on the sedimentary diatom assemblages of Lake Baikal have either focused on the very... more Most studies on the sedimentary diatom assemblages of Lake Baikal have either focused on the very recent past or have been carried out at low sampling resolution on sequences that encompass several glacial/interglacial cycles. Here we present the progress made so far on the high-resolution diatoms analysis of the Holocene records found in three sites, one located in the North basin (Continent Ridge), and two located in the South basin (Posolsky Bank and Vydrino Shoulder). Samples are being analysed at a 5 mm resolution throughout the Holocene record for Vydrino Shoulder and every 1 cm for Posolsky Bank. At Continent Ridge, diatom analysis was carried out every 2 mm on the uppermost 20 cm of the core, while samples for the rest of the Holocene record were analysed every 1 cm only. We expect these to reflect a decadal to centennial resolution. From these three sequences, a very large number of diatom taxa (about 500) have been identified. In all three sequences, endemic planktonic dia...
The ratios of stable carbon and oxygen isotopes are useful palaeoclimatic indicators as they are ... more The ratios of stable carbon and oxygen isotopes are useful palaeoclimatic indicators as they are often governed by climatic factors. This study investigates carbon isotopes of organic matter and oxygen isotopes from biogenic silica of a Holocene profile from Vydrino Shoulder, Lake Baikal. The organic d13C and C/N values are predominantly in the range described for C3 algae. Shifts to higher C/N values can be interpreted as increased inwash from catchment terrestrial sources while lower values indicate increased aquatic productivity. Shifts in d13C can be interpreted in many ways: heavier d13C can be a greater influence of C4 shrubs ad grasses in the catchment indicating climatic cooling. However, heavier values can also result from increased aquatic productivity, decomposition of the organic matter and atmospheric CO2 changes. Values will be members between endmember sources of carbon and interpretation of the record will be aided by understanding of these carbon sources to the lake...
It is important to identify the teleconnections between high latitude forcing and tropical monsoo... more It is important to identify the teleconnections between high latitude forcing and tropical monsoonal circulation in order to understand climate change in East Africa during the Plio-Pleistocene. Here we present a record of aeolian dust transport to the Arabian Sea between approximately 2.9 and 2.3 million years ago (Ma), constructed from the high-resolution XRF scanning of sediment cores from ODP Sites 721 and 722. Variations in the delivery of aeolian dust to the Arabian Sea, reflected in normalised flux of titanium, show that monsoonal circulation prior to 2.6 Ma, and after 2.5 Ma, was highly variable and primarily driven by orbitally-forced changes in tropical summer insolation, strongly modulated by the 400,000 year cycle of orbital eccentricity. This is confirmed by the presence of lakes in the East African Rift Valley during key eccentricity maxima. The dust record is coupled with the analysis of a well-dated series of diatomite units from the Baringo-Bogoria Basin which docum...
Here we present the first dataset to couple oxygen and silicon isotopes determined on diatom sili... more Here we present the first dataset to couple oxygen and silicon isotopes determined on diatom silica from a lake sedimentary profile. Samples have been extracted from a sediment core spanning most of the Holocene ( ∼ 9500 years) collected in the south- ern basin of Lake Baikal, the oldest and deepest freshwater lake in the world. After a sequence of oxidative and acid leaching, sieving and gravity settling, the cleaned opaline samples comprising more than 90% diatoms have been analysed by fluorina- tion - IRMS for oxygen isotopes. An additional NaOH leaching step followed by co- precipitation was carried out prior to the Si isotopic analyses by MC-ICP-MS. Oxygen isotopic compositions of Lake Baikal diatoms have been found to be linked to prevail- ing climatic conditions and resulting balance between southern summer precipitation and northern snowmelt. Diatom silicon isotopic compositions in such a large lake as Baikal are expected to be mostly controlled by the diatoms Si relative ut...
Carbon isotope ratio (d 13 C org ) values of organic matter in lake sediments are commonly used t... more Carbon isotope ratio (d 13 C org ) values of organic matter in lake sediments are commonly used to reconstruct environmental change, but the factors which influence change are varied and complex. Here we report d 13 C values for sediments from Erlongwan maar lake in northeast China. In this record, changes in d 13 C cannot be explained by simple changes in aquatic productivity. Instead, values were likely influenced by differences in the ratio between planktonic and benthic algae, as indicated by the remains of diatoms. This is because the variation of d 13 C org in algae from different habitats is controlled by the thickness of the diffusive boundary layer, which is dependent on the turbulence of the water. Compared with benthic algae, which grow in relatively still water, pelagic algae are exposed to greater water movement. This is known to dramatically reduce the thickness of the boundary layer and was found to cause even more severe d 13 C depletion. In Erlongwan maar lake, low values were linked to the dominance of planktonic diatoms during the period commonly known as the Medieval Warm Period. Values gradually increased with the onset of the Little Ice Age, which we interpret as being driven by an increase in the proportion of benthic taxa, due to effect of the colder climate. The increase in planktonic diatoms at the end of the Little Ice Age, linked to higher temperature and a reduction in ice cover, resulted in a further decline in d 13 C org .
Humanity faces a major global challenge in achieving wellbeing for all, while simultaneously ensu... more Humanity faces a major global challenge in achieving wellbeing for all, while simultaneously ensuring that the biophysical processes and ecosystem services that underpin wellbeing are exploited within scientifically informed boundaries of sustainability. We propose a framework for defining the safe and just operating space for humanity that integrates social wellbeing into the original planetary boundaries concept (Rockströ m et al., 2009a,b) for application at regional scales. We argue that such a framework can: (1) increase the policy impact of the boundaries concept as most governance takes place at the regional rather than planetary scale; (2) contribute to the understanding and dissemination of complexity thinking throughout governance and policy-making; (3) act as a powerful metaphor and communication tool for regional equity and sustainability. We demonstrate the approach in two rural Chinese localities where we define the safe and just operating space that lies between an environmental ceiling and a social foundation from analysis of time series drawn from monitored and palaeoecological data, and from social survey statistics respectively. Agricultural intensification has led to poverty reduction, though not eradicated it, but at the expense of environmental degradation. Currently, the environmental ceiling is exceeded for degraded water quality at both localities even though the least well-met social standards are for available piped water and sanitation. The conjunction of these social needs and environmental constraints around the issue of water access and quality illustrates the broader value of the safe and just operating space approach for sustainable development.
Past environmental changes based on diatom relative abundances have been inferred from the maar L... more Past environmental changes based on diatom relative abundances have been inferred from the maar Lake Erlongwan in northeast China. The limnology of Lake Erlongwan is affected by the strongly seasonal regional climate. The composition of diatom assemblages, in turn, responds to changes in the seasonal duration of ice cover in winter, water-column turnover in spring and autumn, and thermal stratification in summer. Statistical analysis of the sedimentary diatom assemblages reveals three significant stratigraphic zones over the past 1000 yr. The highest abundance of the planktonic species Discostella species occurs between AD 1050 and 1400 and suggests an annual ice-free period of long duration and well-developed summer stratification of the water column. This planktonic diatom peak between ca. AD 1150 and 1200 suggests that this period was the warmest over the past 1000 yr. The interval between AD 1400 and 1800 is marked by a decline in planktonic diatoms and suggests shorter duration of the ice-free season, weaker water stratification and possibly generally cold conditions. After AD 1800 relative abundances of planktonic diatoms, including Puncticulata praetermissa and Asterionella formosa, increase again, which indicates lengthening of the duration of the annual ice-free period and a stronger overturn of the water column. All these data imply that the pattern of the seasons is different between the MWP and the 20th century.
A high-resolution (wevery 20 y) pollen and charcoal record from Erlongwan maar lake (EML) documen... more A high-resolution (wevery 20 y) pollen and charcoal record from Erlongwan maar lake (EML) documents the vegetation history and fire activity of the Long Gang region (northeast China) over the past millennium. The ageedepth model is based on 137 Cs, 210 Pb measurements, and one calibrated 14 C-AMS date at the base of the core. For much of the record, vegetation was dominated by a mixed coniferhardwood forest. Pollen and charcoal concentrations reveal considerable variability during the past 1000 years. Between 980 and 1500 AD both pollen and charcoal reached maximum concentrations (w1100 AD and 1300 AD respectively). The high pollen concentration was indicative of prevailing moist conditions during the period commonly referred to as the Medieval Climatic Anomaly (MCA). The high concentration of charcoal indicated high frequency and intensity of wildfire during the MCA, probably linked to high biomass productivity and less snow in winter. Between 1500 and 1850 AD both pollen and charcoal concentrations were low, indicative of colder winters with higher snowfall, relative drier summers and less intensive wildfire, coincidence with the cold period commonly known as the Little Ice Age (LIA). During 1900e1950 AD year, the highest relative abundance of Artemisia and the lowest abundance of Pinus together with high concentration of charcoal indicated strong human activity. The pollen data are in broad agreement with a previous study from an adjacent lake, indicating regional rather than localized human impact.
Reconstructing climatic variability over the past c. 2 ka years is recognised as a key PAGES time... more Reconstructing climatic variability over the past c. 2 ka years is recognised as a key PAGES timeframe (focus 2). However few high-resolution records exist from the climate sensitive region of N) China which receives the majority of its precipitation from the east Asian summer monsoon (EASM). Interactions between the EASM and the global climate system have great resonance. Such examples include how the EASM responded to changes in climate over the documented eg" Medieval Warm Period"(c. AD 900-1300)," ...
High-resolution TECHNICAP sediment traps have been deployed in Lake Baikal since 1996. Results of... more High-resolution TECHNICAP sediment traps have been deployed in Lake Baikal since 1996. Results of these experiments show distinct seasonal differences in particle flux, ranging from a few mg m-2d-1 to several g m-2d-1. Analyses of trap material show that removal of particles is very fast and efficient. Downward transport through the 1400 m deep water column reaches velocities of up
Spatial and temporal patterns of spheroidal carbonaceous particles (SCP) extracted from lake sedi... more Spatial and temporal patterns of spheroidal carbonaceous particles (SCP) extracted from lake sediments provide an unambiguous record of the distributions of fossil-fuel derived pollutants. When applied to sediment cores taken from Lake Baikal spatial patterns show good agreement with the distribution of industry, with the highest concentrations found in the southern basin nearest to Irkutsk. SCP were found to occur in all cores from all areas of the lake in contrast to metal results where anthropogenically enhanced deposition was only demonstrable in the southern basin. SCP distribution within the sediments of Lake Baikal is seen to be distinctly regional and therefore long distance transport is not thought to be an important pathway for these pollutants. Temporal patterns of SCP show trends that reflect the development of industry in the area since the 1940s. Settling rates in the 1600 m water column suggest that the SCP sediment record may be approximately an order of magnitude more sensitive to depositional changes than that of trace metals.
Freshwater aquaculture is an important source of protein worldwide. Over-exploitation of fisherie... more Freshwater aquaculture is an important source of protein worldwide. Over-exploitation of fisheries can, however, add severely to pressures on ecosystem functioning and services. In Southeast Asia, aquaculture in freshwater lakes contributes significantly to the economy and to reductions in poverty and nutritional insecurity. However, overstocking and excessive feeding of fish can lead to a degradation of affected water bodies, manifest as eutrophication, toxic algal blooms, losses of biodiversity and amenity, anoxia and, in extreme cases, collapse of fisheries. Projected increased warming and storminess associated with global climate change are likely to magnify existing problems. Matching levels of aquaculture production with ecological carrying capacity is therefore likely to become increasingly challenging, requiring levels of data and understanding that are rarely available, a problem that is impossible to rectify in the short term using standard limnological approaches. This paper reviews the development of freshwater aquaculture in the Philippines, associated environmental impacts, and relevant environmental regulations and regulatory bodies. The potential role of palaeolimnology, a science that is relatively under-utilised in the tropics generally and in tropical Asia in particular, in complementing extant datasets, including monitoring records, is highlighted through reference to a preliminary study at Lake Mohicap. Lake Mohicap currently supports aquaculture and is one of a cluster of seven volcanic crater lakes on Luzon, the largest of the archipelago of islands forming the Philippines.
We present a new palaeoenvironmental record of hydrological variability in Lake Baikal, based on ... more We present a new palaeoenvironmental record of hydrological variability in Lake Baikal, based on re-modelled d 18 O diatom values of diatom silica (d 18 O modelled ), where the residual contaminants are identified and compensated for using electron optical imaging and whole-sample geochemistry. d 18 O modelled interpretations are based on the balance between rivers with high d 18 O values and rivers with low d 18 O values. Isotopic variability is related to latitudinal differences in precipitation which feed these rivers. The d 18 O modelled record suggests that rather moist conditions prevailed in the Lake Baikal region during the latter stages of the Younger Dryas. Throughout the Holocene, episodes of low d 18 O modelled values are, in general, in good agreement with increases in percentage haematite-stained grains in North Atlantic sediments (indicative of ice-rafted debris events). Rivers with southerly catchments dominate fluvial input especially between c. 3.3 and 2 cal ka BP, concurrent with high precipitation in the Lake Baikal region.
Detrital grain contamination in a diatom sample can considerably influence the 18 O diatom signal... more Detrital grain contamination in a diatom sample can considerably influence the 18 O diatom signal. In order to obtain a meaningful signal, pure samples must be used. This can be achieved via a series of cleaning stages including organic and carbonate material removal, sieving, differential settling and heavy liquid separation. The method described here works best for sediments with >20% diatom content. Based on testing various clean-up methods, we propose a sequence of four clean-up stages to produce pure diatom samples from a range of lake sediments types starting with a few grams of sediment. The diatom content and the oxygen isotope composition of the samples at each stage were measured in order to assess the effect of differential amounts of contamination. Results show that a four stage clean-up is necessary to produce clean diatom samples and that contamination by silt and clay causes lower 18 O values.
Diatoms in Lake Baikal exhibit significant spatial variation, related to prevailing climate, lake... more Diatoms in Lake Baikal exhibit significant spatial variation, related to prevailing climate, lake morphology and fluvial input into the lake. Here we have assessed the threats to endemic planktonic diatom species (through the development of empirical models), which form a major component of primary production within the lake. Multivariate techniques employed include redundancy analysis (RDA) and Huisman–Olff–Fresco (HOF) models. Our analyses suggest that eight environmental variables were significant in explaining diatom distribution across the lake, and in order of importance these are snow thickness on the ice, water depth, duration of days with white ice, suspended matter in the lake, days of total ice duration, temperature of the water surface in July, concentration of zooplankton and suspended organic matter. Impacts on dominant phytoplankton diatom species are highlighted using t-value biplots. Predictions of future climate change on Lake Baikal are likely to result in shorter periods of ice cover, decreased snow cover across the lake in spring, increased fluvial input into the lake, and an increase in the intensification of surface water stratification during summer months. All these factors are likely to impact negatively on the slow-growing, cold-water endemics such as Aulacoseira baicalensis and Cyclotella minuta, which currently dominate diatom assemblages. Instead, taxa that are only intermittently abundant, at present, in offshore areas (e.g. Stephanodiscus meyerii) are likely to become more frequent. However, given the climatic gradient across the lake, the timing and extent of changes in community structure are likely to vary. Moreover, palaeolimnological records show that Lake Baikal diatom assemblages have been dynamic throughout the Holocene, with both endemic and cosmopolitan species exhibiting periods of dominance. Effects of climate change on the entire lake ecosystem may yet be profound as the structure of the pelagic food web may change from one based on endemic diatom taxa to one dominated by nondiatom picoplankton, and as limnological functioning (e.g. stratification and mixing) affects deepwater oxygen availability, nutrient cycling and trophic linkages.
Humanity faces a major global challenge in achieving wellbeing for all, while simultaneously ensu... more Humanity faces a major global challenge in achieving wellbeing for all, while simultaneously ensuring that the biophysical processes and ecosystem services that underpin wellbeing are exploited within scientifically informed boundaries of sustainability. We propose a framework for defining the safe and just operating space for humanity that integrates social wellbeing into the original planetary boundaries concept (Rockstro¨m et al., 2009a,b) for application at regional scales. We argue that such a framework can: (1) increase the policy impact of the boundaries concept as most governance takes place at the regional rather than planetary scale; (2) contribute to the understanding and dissemination of complexity thinking throughout governance and policy-making; (3) act as a powerful metaphor and communication tool for regional equity and sustainability. We demonstrate the approach in two rural Chinese localities where we define the safe and just operating space that lies between an environmental ceiling and a social foundation from analysis of time series drawn from monitored and palaeoecological data, and from social survey statistics respectively. Agricultural intensification has led to poverty reduction, though not eradicated it, but at the expense of environmental degradation. Currently, the environmental ceiling is exceeded for degraded water quality at both localities even though the least well-met social standards are for available piped water and sanitation. The conjunction of these social needs and environmental constraints around the issue of water access and quality illustrates the broader value of the safe and just operating space approach for sustainable development.
The East Asian winter monsoon (EAWM) not only plays an important role within the Asian climate sy... more The East Asian winter monsoon (EAWM) not only plays an important role within the Asian climate system, but also carries cold air from the high northern latitudes across the Equator to the Southern Hemisphere, acting as a link between the polar and tropical climate systems. However, past changes of the EAWM have not been clearly established so far due to the lack of suitable proxy records. Here, we at first establish an index of the EAWM by comparing the results of a sediment trap experiment and 100-year sedimentary record from Huguang Maar Lake (HML) with modern records of the EAWM, Siberian High (SH) and Arctic Oscillation (AO). Secondly, we present a continuous record of the strength of the EAWM for the past 14,500 years based on sedimentary diatom assemblages in HML. The record is derived from fluctuations in the relative abundance of two planktonic diatom species. The link with the EAWM intensity is through high wind speeds inducing turbulent mixing, which stimulates the productivity of the meroplanktonic species Aulacoseira granulata. The diatom record of the past 14,500 years shows that the EAWM shifted from strong to weak from the early to late Holocene. This linked to both changes in winter temperature at high-latitudes and in El Niño conditions in the tropics. Our record shows that the EAWM and East Asian summer monsoon (EASM) as recorded in stalagmites, were in-phase instead of anti-correlated on orbital time scales during the Holocene. On a millennial time scales, the EAWM was anti-phase with the EASM during the Last Glacial–Holocene transition. However, during the early–middle Holocene the relationship between the EAWM and EASM shows spatial variations. In northern China, the records show significant anti-phase, but in southern China the anti-phase was not observed. During the late Holocene, we did not find any clear relationship between the EAWM and EASM. We also explored the link between the EAWM and the Australian summer monsoon (ASM). Anti-phase of the ASM with summer insolation in the Southern Hemisphere is an enigmatic exception that cannot be explained by the classic theory of insolation. During early Holocene the EAWM was in-phase with the Australian summer monsoon (ASM), which provides the first direct evidence to support the hypothesis that the intensity of the EAWM affected, at least in part, the strength of the ASM.► We present a sedimentary diatom record of the East Asian winter monsoon (EAWM). ► The EAWM shifted from strong to weak from the early to late Holocene. ► The winter and summer monsoons were not anti-correlated on orbital time scale. ► On a millennial time scale, their correlation shows spatial and temporal variability. ► Our record supports the idea of the EAWM affecting the Australian summer monsoon.
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biodiversity and amenity, anoxia and, in extreme cases, collapse of fisheries. Projected increased warming and storminess associated with global climate change are likely to magnify existing problems. Matching levels of aquaculture production with ecological carrying capacity is therefore likely to become increasingly challenging, requiring levels of data and understanding that are rarely available, a problem that is impossible to rectify in the short term using standard limnological approaches. This paper reviews the development of freshwater aquaculture in the Philippines, associated environmental impacts, and relevant environmental regulations and regulatory bodies. The potential role of palaeolimnology, a science that is relatively under-utilised in the tropics generally and in tropical Asia in particular, in complementing extant datasets, including monitoring records, is highlighted through reference to a preliminary study at Lake Mohicap. Lake Mohicap currently supports aquaculture and is one of a cluster of seven volcanic crater lakes on Luzon, the largest of the archipelago of islands forming the Philippines.
biodiversity and amenity, anoxia and, in extreme cases, collapse of fisheries. Projected increased warming and storminess associated with global climate change are likely to magnify existing problems. Matching levels of aquaculture production with ecological carrying capacity is therefore likely to become increasingly challenging, requiring levels of data and understanding that are rarely available, a problem that is impossible to rectify in the short term using standard limnological approaches. This paper reviews the development of freshwater aquaculture in the Philippines, associated environmental impacts, and relevant environmental regulations and regulatory bodies. The potential role of palaeolimnology, a science that is relatively under-utilised in the tropics generally and in tropical Asia in particular, in complementing extant datasets, including monitoring records, is highlighted through reference to a preliminary study at Lake Mohicap. Lake Mohicap currently supports aquaculture and is one of a cluster of seven volcanic crater lakes on Luzon, the largest of the archipelago of islands forming the Philippines.