[Structure Characteristics and Driving Variables of Epilithic Algae Community in Lhasa River Basin of Qinghai-Tibet Plateau].

In order to explore the characteristics and driving factors of the epilithic algae community in the middle and lower reaches of the Lhasa River, epilithic algae was collected and identified in September 2019, the species composition and spatial distribution were analyzed, and the key environmental factors affecting the epilithic algae community were identified through redundancy analysis. The results indicated that 31 genera of epilithic algae belonging to six phyla were identified, and the average cell density of the epilithic algae was 1.92×106 cells·m-2. The number of species and cell density of the diatom phylum were the largest at each sampling point. The species number and cell density of the epilithic algae were significantly different between the main stream and tributaries. The main stream and tributaries contained relatively small differences in the dominant algae genera, which were Gomphonema, Fragilaria, Cymbella, and Planktolyngbya in the main stream and Gomphonema, Fragilaria, Cymbella, and Oscillatoria in the tributaries. The redundancy analysis revealed that temperature, pH, and dissolved oxygen were the main driving factors affecting the community structure of the dominant genus in the main stream, while HCO3- and flow velocity controlled the community structure of the dominant genus in the tributaries. This study provides basic data and the theoretical basis for the conservation of aquatic ecosystems and water quality management in the middle and lower reaches of the Lhasa River.

[Influence Factors of Potential Nitrification Rates and Functional Genes Abundance in the Jinshui River and the Qihe River of the Hanjiang River Basin].

In the context of increasing nitrogen loading in river systems worldwide, it is critically important to understand nitrification to maintain river ecosystem health. This comparative study was conducted to explore the relationships among the intensity of human disturbance, environmental factors, potential nitrification rate, and functional gene abundance in the Jinshui River (slightly disturbed basin) and the Qihe River (intensely disturbed basin). The results showed that AOA-amoA gene abundance was higher than that of AOB-amoA. The potential nitrification rate in the Qihe River was higher than that in the Jinshui River. There was no significant difference in AOA-amoA gene abundance between the two rivers; however, the AOB-amoA gene abundance in the Qihe River was significantly higher than that in the Jinshui River in the low flow season. The abundance of nitrification functional genes was significantly correlated with water temperature, pH, NO3-, NH4+, and organic carbon. The potential nitrification rate was positively correlated with water temperature, pH, and NO3-, and negatively correlated with AOB-amoA gene abundance. These results showed that the intensely disturbed sites had higher potential nitrification rates and nitrification functional genes abundances, and potential nitrification rates and abundances of nitrification function genes were significantly related to physical and chemical water and sediment factors. This study will be important for nitrogen pollution control in the river systems.

Flexible endoscope visualization to assist in the removal of a string of 10 schwannomas at the cauda equina: technical case report.

Bead-like schwannomas at the cauda equina are rare but benign intraspinal tumors. They can involve multiple nerve roots and spread within the spinal canal, and open resection would cause significant trauma. The authors have successfully applied a novel minimally invasive technique for the total removal of such schwannomas. A 68-year-old woman presented with a 1-month history of left waist and leg pain. MRI demonstrated multiple intraspinal lesions located from L1 to S1. The diagnosis was bead-like schwannomas at the cauda equina. Two incisions were made at the T12 and L5 levels. A flexible endoscope was introduced into the spinal canal following hemisemilaminectomy under a microscope to identify the relationship between the tumors and the carrying nerves. After dissecting both cranial and caudal ends of the carrying nerve, the string of bead-like tumors was gently pulled out from the caudal end as a whole. The endoscope was reintroduced into the spinal canal to ensure complete tumor removal. The patient recovered quickly, and no tumor residual was found at postoperative MRI. Flexible endoscope-assisted visualization plus microscopic hemisemilaminectomy via 2 incisions is a feasible minimally invasive approach for selected patients with bead-like schwannomas at the cauda equina.