ALBERT

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: We create a deep neural network based approach for the geospatial predicition of total organic carbon percentages in marine sediments. The code in the repository includes jupyter notebooks and python files to pre-process the data, train the models and post-process the outputs.

Beschreibung: Misapplication of Ulva epithets in GenBank has led to confusion in the scientific literature and community. To solve some of the problems, targeted DNA sequencing of plastid encoded rbc L gene amplicons or high-throughput sequencing was performed on all blade-forming Ulva type specimens from the northeast Pacific. Recently collected specimens from at or near type localities were also analyzed for some taxa. Based on these genetic analyses, we confirmed currently recognized species: U. californica , with U. angusta and U. scagelii as heterotypic synonyms, U. stenophylla , U. taeniata , and U. tanneri . Ulva dactylifera , currently considered a synonym of U. taeniata based on morpho-anatomy, is recognized as a distinct species, as is U. expansa whose type specimen was sequenced in 2018. All but two of the ITS, rbc L and tuf A sequences in GenBank that were labeled U. californica were correctly named, in contrast to U. taeniata , for which only one of 14 sequences was correctly labeled. These results show that DNA sequencing of Ulva type specimens is essential for the correct application of names.

Beschreibung: DNA sequences were obtained from 32 blade-forming Ulva specimens collected in 2018 and 2019 from four islands in the Galápagos Archipelago: Fernandina, Floreana, Isabela and San Cristóbal. The loci sequenced were nuclear encoded ITS and plastid encoded rbc L and tuf A, all recognized as barcode markers for green algae. Four species were found, Ulva adhaerens , U. lactuca , U. ohnoi and U. tanneri , all of which have had their type specimens sequenced, ensuring the correct application of these names. Only one of these, U. lactuca , was reported historically from the archipelago. Ulva adhaerens was the species most commonly collected and widely distributed, occurring on all four islands. Previously known only from Japan and Korea, this is the first report of U. adhaerens from the southeast Pacific Ocean. Ulva ohnoi was collected on three islands, Isabela, Floreana, and San Cristóbal, and U. lactuca only on the last two. Ulva tanneri is a diminutive, 1–2 cm tall, high intertidal species that is easily overlooked, but likely far more common than the one specimen that was collected. This study of blade-forming Ulva species confirms that a concerted effort, using DNA sequencing, is needed to document the seaweed flora of the Galápagos Archipelago.

Beschreibung: The 2007 flora “Green Seaweeds of Britain and Ireland” did not present the molecular data underpinning the Ulvaceae treatment, mostly ITS sequences. Subsequently, names have changed as type material of Ulva species is sequenced and intensive sampling with DNA barcoding adds new European species. To update the Ulvaceae, we systematically sampled from 2007 to 2021, identifying specimens using various molecular markers alongside DNA from type material of four species. We show here that Ulva gigantea , based on rbc L, tuf A and ITS sequences of its holotype, is assigned to Ulva compressa , as is the lectotype of Ulva curvata . Ulva gigantea sensu GenBank and Ulva pseudocurvata are conspecific. The correct name is U. pseudocurvata based on rbc L sequences of the lectotype. Two species of monostromatic Ulvaceae were included in the 2007 flora, but we show that both of them and all earlier British monostromatic collections represent Ulvaria splendens , a species originally described from Alaska. Analysis of two rbc L amplicons of the Ulva sordida lectotype shows that it is conspecific with Ulvaria splendens . Our first genuine collections of Ulvaria obscura from SW England and SW Wales correspond to topotype material from the Bay of Biscay, recent samples from Galicia and unpublished tuf A sequences from Britanny.

Beschreibung: Highlights • δ13C and δ18O profiles increase from exterior to interior until reaching a plateau. • Primary Layer δ13C reflects the δ13C of the Dissolved Inorganic Carbon. • In high pCO2 experiments, δ13C and δ18O closer to equilibrium fields. • Brachiopods grow according to an incremental growth model. Abstract Brachiopod shells are ubiquitous since the Early Cambrian up to now. As they secrete a shell made of low-magnesium calcite, more resistant to diagenesis than biocarbonates richer in Mg, their geochemical signatures are generally considered a powerful tool for paleo-environmental and paleo-climatic reconstructions. However, gaps in knowledge still remain on the underlying controls of the shell chemistry, in particular at a high spatial resolution. In this study, in situ oxygen and carbon isotope measurements by SIMS (Secondary Ion Mass Spectrometry) were performed in brachiopod shells of the cold-temperate water species Magellania venosa, constituted of a primary and a secondary layer. The individual specimens studied here grew under controlled conditions mimicking the natural environment and in experiments under low-pH (high pCO2) and high-temperature conditions. Transversal carbon and oxygen profiles showed a “brachiopod pattern” typical of extant two-layered brachiopods, with the primary layer depleted in 18O and 13C relative to equilibrium and the secondary layer showing a gradual increasing trend until reaching a near-equilibrium plateau. Overall, shells cultured at low pH were found to have δ18O and δ13C values closer to equilibrium when compared to shells from the control experiment. These near-equilibrium values may reflect a decrease in shell precipitation rate, leading to less kinetic effects, and/or a more rapid kinetics for the equilibration between DIC species and water. By close pairing of seawater δ18O and δ13C to that of shell microstructure, our study enables us to derive layer-specific C and O enrichment factors, which show the extent of pH and temperature effects superimposed on the seawater δ18O and DIC δ13C signal inherited. Finally, we show that during brachiopod shell growth, newly precipitated calcite is added to the calcite already existing, thus empirically validating the conceptual accretionary growth model proposed by Ackerly (1989).

Beschreibung: Species classified in the genus Ulva are important foundational marine primary producers distributed worldwide. These species are particularly abundant and diverse through the northwest Pacific (NWP) where they experience marked latitudinal gradients of environmental heterogeneity. It is unclear, however, to what extent such dynamic conditions can modulate phenotypic and genetic patterns in these organisms, potentially reflecting the influence of historical and contemporary biotic and abiotic factors. Here, we assessed inter- and intra-specific genetic patterns of Ulva species through the NWP using plastid rbc L and tuf A gene sequences. Although we initially targeted Ulva australis based on morphological identification, we recovered eight Ulva genetic entities masked by morphological similarities. Except for the Ulva linza–procera–prolifera and U. lactuca–reticulata complexes, six of these genetic entities were recovered as individual species (i.e., U. australis , U. ohnoi , U. californica , U. compressa , U. lacinulata , and U. arasakii ), and showed biogeographic patterns likely explained by clines in sea surface temperature and ocean current dispersal. At intra-specific level, all the genetic entities showed low genetic variation and divergence based on rbc L (0–0.3 %) and tuf A (0–0.9 %) data. Our results provide insights regarding intra- and inter-specific genetic patterns characterizing morphologically similar Ulva species through the NWP. However, further studies are needed to understand the mechanisms underpinning such patterns and the associated ecological and evolutionary implications.