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...
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
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.
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...
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
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.
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.