Patrick Rioual | Chinese Academy of Sciences (original) (raw)

Papers by Patrick Rioual

Climate of The Past, Feb 28, 2022

Palaeogeography, Palaeoclimatology, Palaeoecology, Nov 1, 2016

Fundamental and Applied Limnology, Jul 7, 1998

Geophysical Research Letters, Jun 15, 2001

HAL (Le Centre pour la Communication Scientifique Directe), Apr 20, 2008

International audienc

PhytoKeys

Lake Qinghai is an ancient brackish water lake in which several endemic diatom species have been ... more Lake Qinghai is an ancient brackish water lake in which several endemic diatom species have been discovered. In this study, a species of Diatoma is observed under light and scanning electron microscopy and described as new, Diatoma sinensissp. nov. The living cells of D. sinensis always lie in girdle view due to the cell depth being much larger than valve width (3.3–8.8 vs. 2.0–3.0 μm). The valves of D. sinensis are characterized by their narrow, linear-lanceolate outline, with capitate to subcapitate apices, the presence of two rimoportulae, one at each apex, embedded in the last rib or located among striae and a 4:2 configuration of girdle bands in normal vegetative cells, with four bands assigned to the epivalve and two to the hypovalve. The new taxon is compared with similar species from the genera Diatoma and Distrionella.

Acta Geologica Sinica - English Edition, 2019

Frontiers in Earth Science

The unique geographical and climatic settings of the eastern Pamirs make this region sensitive to... more The unique geographical and climatic settings of the eastern Pamirs make this region sensitive to the Westerlies and global climate change. Holocene fluctuations in water-level of Lake Kalakuli, a proglacial lake located to the northwest of the Muztag Ata glacier, were reconstructed based on diatoms from a ∼15 m long sediment core spanning the last ∼9,900 years. To establish how diatom species distribute in relation to water depth in Lake Kalakuli, a dataset of 45 surface sediment samples was retrieved from different water depth. Statistical analyses such as cluster analysis (TWINSPAN) and redundancy analysis (RDA) were used to demonstrate that the water depth gradient is the main environmental gradient driving the distribution of these diatom assemblages. A diatom-water depth transfer function, was then developed using a weighted averaging partial least squares component 2 model (R2 = 0.89, RMSEP = 1.85 m) and applied to the Holocene diatom sequence from Lake Kalakuli. Due to the l...

$Research paper thumbnail of brGDGTs fractional abundance and brGDGTs-based summer-autumn temperature record for the period of ~60-8 ka in Sihailongwan maar lake, Northeast China$

This datasets consist of 1. the fractional abundances of brGDGTs from Sihailongwan maar lake surf... more This datasets consist of 1. the fractional abundances of brGDGTs from Sihailongwan maar lake surface sediments, suspended particulate matters, and soils from the catchment; 2. the brGDGTs sequence of Sihailongwan maar lake for the period of ~60-8 ka; 3. the brGDGTs-based summer-autumn (June-November) temperatures for the period of ~60-8 ka.

Phytotaxa, 2017

Populations of a fragilarioid diatom from inter-dune lakes of the Badain Jaran Desert (northern C... more Populations of a fragilarioid diatom from inter-dune lakes of the Badain Jaran Desert (northern China), originally identified and reported under the name Fragilaria sp. cf. famelica, were investigated in detail using light and scanning electron microscopy. The analyses indicate that most of the morphological features of this taxon are identical to Williamsella angusta Graeff, Kociolek & S.R. Rushforth, the type species of the genus Williamsella recently described from Blue Lake warm spring (Utah, USA). The criteria used to separate Williamsella from Fragilaria (i.e. the presence/absence of spines, the colonial formation, the preference for saline vs freshwater habitat, and the coverings of the areolae) are not supported and the genus is refuted. Instead the new combination Fragilaria crenophila comb. nov. is proposed for the Blue Lake species. The taxon from the Badain Jaran desert lakes represents a varietal population that is characterized by shorter valve length and lower stria d...

Cryptogamie, Algologie, 2017

Abstract During an investigation on the diatom communities of volcanic lakes of Northeastern Chin... more Abstract During an investigation on the diatom communities of volcanic lakes of Northeastern China a new species belonging to the “Cyclotella comta species complex” was observed. This taxon forms relatively large populations in the phytoplankton of Lake Tuofengling Tianchi, a 33m-deep, oligotrophic, crater lake located in Inner Mongolia. In this paper, the valve morphology and ultrastructure of this taxon is described using light and scanning electron microscopy and a new name, Lindavia khinganensis sp. nov., is proposed. A discriminant analysis based on morphological LM and SEM data confirmed that L. khinganensis is distinct from other Lindavia species with a similar morphology such as L. comta (Ehrenberg) Nakov et al., L. radiosa (Grunow) De Toni & Forti, L. balatonis (Pantocsek) Nakov et al., L. praetermissa (Lund) Nakov et al. and L. tenuistriata (Hustedt) Nakov et al. In addition, the seasonal and interannual distribution of L. khinganensis was investigated using sediment trap samples collected over a two-year period. Limnological data from Lake Tuofengling, including water chemistry and temperature recording from a thermistor chain provided complementary information about the ecology of this new species. This species was not found in any other lakes from Northeastern China that we investigated.

Diatom Research, 2017

A new araphid diatom, Diatoma kalakulensis sp. nov., was discovered in Lake Kalakul, located in t... more A new araphid diatom, Diatoma kalakulensis sp. nov., was discovered in Lake Kalakul, located in the Pamir Mountains in north-western China. The morphology and ultrastructure of this new species are described on the basis of observations made under light and electron microscopy. Compared to Diatoma tenuis, Diatoma kalakulensis is characterized by longer valves, higher stria density, wider apical ends and the position of its rimoportula.

Journal of Hydrology, 2017

Abstract A paucity of studies on the interaction between environment and ground water recharge se... more Abstract A paucity of studies on the interaction between environment and ground water recharge severely restricts the ability of people to assess future water resources under changing environment. In this study, an effort to explore the relationship between the arid environment and ground water recharge was carried out using multivariate statistical techniques in a sedimentary drainage basin (the Jungar) in northwestern China. Hierarchical cluster analysis (HCA) and principal components analysis (PCA) were performed based on hydrogeochemical data to assess the ground water recharge and its governing factors. Observation of the HCA and PCA analytical results revealed a division of seven clusters (C1 to C7) and three principal components (PC1 to PC3), which explained 59.6%, 16.6% and 10.9% of the variance, respectively, and thus, accounted for the majority of the total variance in the original dataset. Based on these Q-mode HCA clusters and R-mode PAC scores, dominant environmental processes influencing recharge regimes were identified, i.e., geogenic, geomorphoclimatic, and anthropogenic, which separated the recharge regimes into four zones (Zone I to Zone IV). Zones I and II (C4 + C1) were associated to “elevated hydroclimate degree” coupled to “low salinity”. Zone III (C2 + C3) was associated to “moderately elevated salinity” and evidently “elevated contamination” but coupled to “low hydroclimate degree”. Zone IV (C5 + C6 + C7) was associated mainly to “elevated salinity” coupled to “low or inverse hydroclimate degree”. It revealed that the geogenic processes are more significant (60%) than the geomorphoclimatic (17%) and anthropogenic (11%) processes. As a result, the overall recharge process is rather heterogeneous and is strongly environment dominated in the Jungar drainage system. Compared with other watersheds in arid environment, a distinctive feature of the Jungar waters is that they are affected by a combination of natural and non-natural events, rather than following a steady and continuous geological evolution. These will continue to influence the recharge regime of the Jungar for a long time due to its steady tectonics and arid climate. However, changing rainfall, but not snow, is becoming the key factor driving changes in ground water resources in this drainage system, as results of the decades of warming and humidification in northwestern China.

Journal of Paleolimnology, 2016

The last deglaciation is of great interest because Northern Hemisphere climate has gone through s... more The last deglaciation is of great interest because Northern Hemisphere climate has gone through several abrupt changes. We present an n-alkane and compound-specific carbon isotope record of the last deglaciation from the annually laminated sedimentary sequence of Lake Xiaolongwan, northeastern China. The n-alkane distribution suggests that the sparsely distributed vegetation prior to 14.7 ka BP, changed to wood plants and aquatic macrophytes in the early Bølling-Allerød, and was followed by a broadleaved deciduous forest after 11.4 ka BP. In this forest region, where the vegetation is dominated by C3 plants, the compound-specific δ13C value of the long-chain n-alkanes (nC27, nC29 and nC31) is interpreted as a proxy of effective precipitation, while temperature might play a minor secondary role. The positive δ13C27–31 values during the Bølling-Allerød suggest a dry-warm climatic condition, while the negative δ13C27–31 at 13.0–11.4 ka BP indicates a cold-wet climate during the Younger Dryas in this region. Two periods with lower δ13C27–31 occurred at 16.1–16.5 and 17.3–17.7 ka BP and could be associated with the Heinrich event-1a and the Heinrich event-1b, respectively. The synchroneity between the biomarker time series in Lake Xiaolongwan and the δ18O record from the Greenland ice core suggest the dominance of high latitude processes on regional monsoon evolution from the last glacial, the Bølling-Allerød, the Younger Dryas to early Holocene. Regionally, the Okhotsk High might have played an important role for abrupt changes during the glacial/interglacial transition.

Phytotaxa, 2014

A new medium-sized species of Hippodonta (Bacillariophyceae) is described from Lake Qinghai, Chin... more A new medium-sized species of Hippodonta (Bacillariophyceae) is described from Lake Qinghai, China. The morphology and ultrastructure of Hippodonta qinghainensis sp. nov. are described using light and scanning electron microscopy. This new species is compared with similar species of Hippodonta using conventional and geometric morphometric analyses. Hippodonta qinghainensis can be separated from the other species of Hippodonta by a unique combination of characters that include an elliptic-lanceolate to rhombic-lanceolate valve shape, non protracted apices, the absence of fascia, relatively coarse, uniseriate striae and the presence of two rows of lineolae around the valves apices.

Phytotaxa, 2016

The morphology and ultrastructure of Gyrosigma peisonis var. major var. nov., a new variety of Gy... more The morphology and ultrastructure of Gyrosigma peisonis var. major var. nov., a new variety of Gyrosigma peisonis found in Lake Qinghai (China), are described here on the basis of light and scanning electron microscopy. Most of the morphological features of this new variety are identical to those of the nominal variety Gyrosigma peisonis var. peisonis, but the variety major differs in its distinctly larger cell size and its higher value for the longitudinal/transverse stria density ratio, however. The seasonal variation of this taxon, which was investigated by a sediment-trap study is also discussed.

Palaeogeography, Palaeoclimatology, Palaeoecology, 2015

ABSTRACT