ALBERT

Description: The complexity of the Mekong River Basin (MRB) has been presented in three different sections focusing on various aspects on the MRB ecohydrological system. Section 1 starts with the physical processes of climate, hydrology, sediment, aquatic biodiversity, changes of land cover/land use, and water related hazards like floods and droughts. In section 2, the book focuses on the water resource management and development and collaboration in the upper MRB, with a special focus on hydro-power development. The last section is dedicated to the Vietnamese Mekong Delta (VMD) crossing typical environmental problems like water pollution, river morphological changes, land subsidence, salinity intrusion, coastal erosion, as well as livelihood and climate change adaptation, and agriculture transformation.

Description: The Mekong River drains a catchment of over 800,000 km2 and is the world's 12th longest river (4800 km), the 8th largest water discharge (470 × 106 m3/year), and the 10th largest sediment load (160 × 106 tons/year). The Mekong starts on the Qinghai–Tibet Plateau with a maximal elevation of 5220 m, flows through six countries (China with 16% of its basin, Myanmar with 5% of its basin, Laos with 35% of its basin, Thailand with 18% of its basin, Cambodia with 18% of its basin, and Vietnam with 11% its basin), and empties into the Vietnam East Sea (South China Sea). The Mekong River basin (MRB) has the world's most diverse river ecosystem. It is the world's largest inland fishery. Its biodiversity is fundamental to agricultural production and the food security of 90 million people in the Lower Mekong basin, including about 18 million people in the Vietnamese Mekong delta.

Description: The Mekong River Basin: Ecohydrological Complexity from Catchment to Coast, Volume Three presents real facts, data and predictions for quantifying human-induced changes throughout the Mekong watershed, including its estuaries and coasts, and proposes solutions to decrease or mitigate the negative effect and enable sustainable development. This is the first work to link socio–ecological interaction study over the whole Mekong River basin through the lens of ecohydrology. Each chapter is written by a leading expert, with coverage on climate change, groundwater, land use, flooding drought, biodiversity and anthropological issues. Human activities are enormous in the whole watershed and are still increasing throughout the catchment, with severe negative impacts on natural resources are emerging. Among these activities, hydropower dams, especially a series of 11 dams in China, are the most critical as they generate massive changes throughout the system, including in the delta and to the livelihoods of millions of people and they threaten sustainability.

Description: The Mekong Delta is affected by annual seasonal salinity intrusion in December–May. In this season, the discharge of the Mekong is low, and high tidal water levels cause a deep intrusion of saline water. Critical salt concentrations can be observed 50–80 km deep during high tides. These high salt concentrations cause severe problems in terms of fresh irrigation and drinking water. A quantitative knowledge of the current and likely future salinity intrusion is thus urgently required to develop adaptation plans and mitigation measures. This chapter quantifies the current salinity intrusion in the Mekong Delta, as well as a model-based estimation of the possible future salinity intrusion. The different factors affecting salinity intrusion—changing river discharge by climate change and dam development, changes in effective tidal water levels, changing ocean salinity—and their impacts are quantified by hydraulic modeling. Based on the modeling results, recommendations for future planning are derived.

Description: Biodiversity generally increases productivity in ecosystems; however, this is mediated by the specific functional traits that come with biodiversity loss or gain and how these traits interact with environmental conditions. Most biodiversity studies evaluate the effects of species richness alone, despite our increasing understanding that intraspecific diversity can have equally strong impacts. Here, we manipulate both species richness and intraspecific richness (i.e., number of distinct strains) in marine diatom communities to explicitly test the relative importance of species and strain richness for biomass and trait diversity in six distinct temperature/nutrient environments. We show that species and strain richness both have significant effects on biomass and growth rates, but more importantly, they interact with each other, indicating that cross-species diversity effects depend on within-species diversity and vice versa. This intertwined relationship thus calls for more integrative approaches quantifying the relative importance of distinct biodiversity components and environmental context on ecosystem functioning.

Description: Solar-driven seawater electrolysis for hydrogen fuel production holds an outstanding potential towards the development of a carbon-neutral and sustainable energy infrastructure, but the development of green, efficient and stable photoelectrocatalysts selectively promoting oxygen evolution remains a formidable challenge. Motivated by this issue, in this work we propose a tailored combination of two economically viable materials, α-Fe2O3 and graphitic carbon nitride (gCN), to fabricate promising anodes – eventually decorated with cobalt phosphate (CoPi) particles – for alkaline seawater photosplitting. The target systems were fabricated via an original multi-step route, involving the plasma-enhanced chemical vapor deposition of iron(III) oxide on conducting glasses, the introduction of gCN in very small amounts by a rapid and facile electrophoretic process, and final annealing in air. A comprehensive characterization revealed the successful fabrication of composites featuring a tailored surface defectivity, a controlled nano-organization, and a close Fe2O3/gCN interfacial contact. After decoration with CoPi, the best performances corresponded to a Tafel slope of ≈100 mV dec−1 and overpotential values enabling us to rule out the competitive hypochlorite formation. In addition, photocurrent densities at 1.23 V vs. RHE showed a nearly 7-fold increase upon Fe2O3 functionalization with both gCN and CoPi. These amenable results, directly dependent on the electronic interplay at Fe2O3/gCN heterojunctions and on CoPi beneficial effects, are accompanied by a remarkable long-term stability, and may open up attractive avenues for clean energy production using natural resources.

Description: Silicic caldera volcanoes present major volcanic and seismic hazards but also host dynamic hydrothermal and groundwater systems and a rich but largely unexplored subsurface biosphere. Many of these volcanoes are hosted in rift settings. The intricate connections and feedbacks among magmatism, rifting, hydrothermal processes, and the biosphere in these complex systems remain poorly understood, necessitating subsurface joint observations that are only enabled by scientific drilling. The CALDERA (Connections Among Life, geo-Dynamics and Eruptions in a Rifting Arc caldera) project workshop funded by the International Continental Scientific Drilling Program (ICDP) gathered multi-disciplinary international experts in January 2023 to advance planning of a scientific drilling project within one of these dynamic, rift-hosted calderas, the Okataina Volcanic Centre (OVC), Aotearoa New Zealand. The OVC's high eruption rate, frequent unrest events and earthquake swarms, location in a densely faulted rapidly extending rift, abundant groundwater–geothermal fluid circulations, and diverse surface hot spring microbiota make it an ideal location for exploring a connected geo-hydro-biosphere via scientific drilling and developing a test bed for novel volcano monitoring approaches. Drilling configurations with at least two boreholes (∼ 200 and ∼ 1000–1500 m deep) were favoured to achieve the multi-disciplinary objectives of the CALDERA project. Decadal monitoring including biosphere activity and composition has the potential to evaluate the response of the hydro-bio system to volcano-tectonic activity. In addition to the OVC caldera-scale datasets already available, site surveys will be conducted to select the best drilling locations. The CALDERA project at the OVC would provide, for the first time, an understanding of volcanic–tectonic–hydrological–biological connections in a caldera–rift system and a baseline for global comparisons with other volcanoes, rifts, and hydrothermal systems. CALDERA would serve as an unprecedented model system to understand how and how quickly the subsurface biosphere responds to geologic activities. Discoveries will improve assessment of volcanic and seismic hazards, guide the sustainable management and/or conservation of groundwater and geothermal resources and microbial ecosystems, and provide a forum for interweaving mātauranga Māori and Western knowledge systems.