Effect of deposition and erosion within the main river channel and large lakes on sediment delivery to the estuary of the Yangtze River

We analysed the occurrence of ostracods in a small river, taking into account all the types of water bodies in the floodplain − these included helocrenes, oxbow lakes, and ponds, as well as the main river channel. The objective of the study was to investigate the variation in ostracod communities and identify those factors determining species distribution. The environmental factors considered were the type of water body, responsible for 17% of the variance, the physical and chemical water properties (29%), and the biotic and abiotic factors associated with the substrate type (23%). Among the factors associated with the substrate, sediment sorting, plant coverage and insolation were the most important. The ostracod fauna of the helocrenes differed from that of the other water bodies in the floodplain. In the water bodies of the Krąpiel valley and in the main river channel, 33 ostracod species were recorded, of which 26 were found in the main river channel. Refugia in the floodplain were the main source of the diversity and abundance of ostracods in the main river channel. The mean density in the main river channel was very low, at 330 indiv. m−2, while in the water bodies of the floodplain it was the greatest, reaching up to 5568 indiv. m−2.

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Provenance Shift during the Plio-Pleistocene in the Vertex of Yangtze Delta and Its Geomorphological Implications

Minerals ◽

10.3390/min10110996 ◽

2020 ◽

Vol 10 (11) ◽

pp. 996

Author(s):

Junjie Yu ◽

Wei Yue ◽

Ping Liu ◽

Bo Peng ◽

Jie Zhang ◽

...

Keyword(s):

Yangtze River ◽

River Channel ◽

Heavy Minerals ◽

Tectonic Subsidence ◽

Zircon Geochronology ◽

The Yangtze River ◽

Yangtze Delta ◽

The South ◽

Source To Sink ◽

Regional Tectonic

One of the key issues of the Source-to-Sink process is revealing the geomorphological evolutions of large rivers from the perspective of river sink areas. This study aims to reveal the provenance change near the vertex of the Yangtze delta during the late Cenozoic and provide insight into the Yangtze channelization into the sea due to regional tectonic subsidence. Heavy minerals and zircon geochronology in the Plio-Pleistocene sediments of the vertex of the modern Yangtze delta (core RGK15) reveal that a significant provenance shift occurred at ~2.6 Ma (the beginning of the Pleistocene). During the Pliocene, ultra-stable heavy minerals and pre-Mesozoic zircon grains predominated in the sediments, probably derived from contemporary outcrops of sedimentary rock that were widely distributed in the delta and its surrounding area. They are completely different from those in the Pliocene sediments of the south delta, indicating that decentralized, local, small watersheds dominated the Yangtze delta during the Pliocene. This resulted from the relatively elevated terrain of this region due to the adjacent ancient Zhejiang–Fujian Uplift (ZFU) at that time. However, diversified heavy minerals and zircon geochronology similar to those of the modern upper Yangtze fingerprints occur in the Pleistocene sediments of core RGK15, implying that a significant provenance shift to the Yangtze River occurred here at ~2.6 Ma. The provenance shift recorded by the cores in the south delta mainly occurred at ~1.2 Ma, indicating that the Yangtze River channel was dragged southward with the further subsidence of the ancient Zhejiang–Fujian Uplift. This study reveals the southward migration process of the Yangtze River channel with the regional tectonic subsidence from the perspective of provenance evolution, which contributes to an understanding of when the Yangtze River channelized into the sea.

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Coleoptera associated with macrophytes of the genus Salvinia in four oxbow lakes in two river basins in southeast Brazil

Brazilian Journal of Biology ◽

10.1590/1519-6984.06914 ◽

2015 ◽

Vol 75 (4 suppl 1) ◽

pp. 108-118 ◽

Cited By ~ 1

Author(s):

M. C. Paula-Bueno ◽

A. A. Fonseca-Gessner

Keyword(s):

River Basins ◽

River Channel ◽

The State ◽

The Other ◽

Oxbow Lakes ◽

Aquatic Fauna ◽

Southeast Brazil ◽

Main River ◽

Main River Channel ◽

The Difference

Abstract Macrophytes in oxbow lakes represent an important substrate for the Coleoptera. Two oxbow lakes the Rio Paranapanema were studied and the other two Rio Mogi-Guaçu, in the State de São Paulo, Brasil. In this study, there is greater similarity between the communities of Coleoptera of lakes greater connectivity with the main river channel or the difference in the species of Salvinia collected in the lakes studied interferes Coleoptera fauna that uses as substrate. A total of 9,222 specimens of Coleoptera were collected and identified in 10 families and 40 genera. The analysis MDS for abundance of Coleoptera showed the grouping of the oxbow lakes the Paranapanema River and a distancing the oxbow lakes the Mogi-Guaçu. The PERMANOVA test did not reveal any difference in the fauna between the wet and dry periods. It was concluded that the connectivity between river and lake is not decisive for the richness and abundance of aquatic fauna of Coleoptera. Therefore, the richness and abundance of aquatic Coleoptera associated vary with the species of Salvinia used as substrate.

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