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Frustulia hengduanensis sp. nov. Fen Luo & Quanxi Wang (LM Figs 1–14, SEM Figs 15–24) Description:— LM: Valves elliptico-lanceolate or rhomboid with slightly undulate margins. Apices narrowly rounded and moderately protracted. Valve length 43–55 μm, breadth 11–14 μm (n=30). The longitudinal ribs slightly curved. On the valve face, the striation patterns are weakly discernible under LM. Striae absent within the central area, forming a dumbbell-shaped hyaline zone (Figs 1–14). SEM: External view, the striae parallel at the valve center and slightly convergent towards the apices, with 36–40 striae per 10 μm (Fig. 15). Striae wavy along the length of the valve (Figs 15–16). The valve ends circumradiated by one or two rows of areolae (Figs 18–19). Areolae rounded to elliptical at the valve center and more slit-like distally, with 33–36 areolae per 10 μm (Figs 17–18). Striae absent within the central area, forming a dumbbell-shaped hyaline zone (Figs 16–17). The raphe is filiform, and both the proximal and the terminal raphe ends are T-shaped (Figs 17–19). Internal view, areolae have circular to rectangular hymenes (Fig. 22). Both the longitudinal ribs and the raphe slightly curved (Fig. 20), while both proximal and terminal raphe ends are straight (Figs 21–24). At the apices, the longitudinal ribs and the helictoglossae fuse to form a small porte-crayon (Fig. 24). Type: — CHINA. Sichuan Province: Hengduan Mountains, Q.X. Wang, F. Luo and colleagues, August 2015 (holotype SHTU! SC201508131, Biology Department Diatom Herbarium, Shanghai Normal University, Shanghai, China = Fig. 2. Isotype YXNU! SC201508131, Biology Department Diatom Herbarium, Yuxi Normal University, Yuxi City, Yunnan Province, China). Etymology: —The species is named for its type locality in the Hengduan Mountains. Ecology: —All samples were collected from fen peat and a stream fen at elevations of 4160–4750 m asl in freshwater at 5.3–15.3 °C, with pH 6.9–8.1, salinity 0.01–0.08 ‰, and conductivity 20–91 μs∙ cm-1.. Distribution: —This species is known from five samples collected in the Haizi Mountain Reserve, Daocheng County, Sichuan Province, China (slide nos. SC201508127, SC201508128, SC201508131, SC201508132, and SC201508137) and from one sample collected in Zuogong County, Tibet (slide no. HDS201810304).

A total of four time surveys on water quality and its phytoplankton of Dianshan Lake in Shanghai, China were carried out in January, April, July and October 2019. Phytoplanktonic index of biotic integrity(P-IBI)was constructed to assess the water health condition of Dianshan Lake. The comprehensive nutritional status index(TSI)is used to determine the reference sites and the impaired sites, 19 biological indexes with widely application and high selection rates were used as candidate biological indexes, and the candidate indexes were tested for the distribution, discriminant analysis, correlation analysis. Finally,five parameters composing the P-IBI of Dianshan Lake were obtained:number of diatom species, phytoplankton richness index, percentage of Chlorophyta density,percentage of Cryptophyta density,and total phytoplankton biomass. P-IBI was used to evaluate the ecosystem health of the lake. On the whole, Dianshan Lake is in the state of sub-healthy. Among them, there are one, eight and three points in the healthy, sub-healthy and good state respectively. It is sub-healthy when in spring and winter, and good when in summer and autumn. P-IBI has a very significant positive correlation with water transparency(SD),and a very significant negative correlation with Chlorophyll a(Chl a)and total phosphorus(TP).

Lugu Lake is the third largest deep-water lake in China, the lake basin is complex in its shape, with many peninsulas, islets and bays. It has high habitat diversity and transparency which is up to 12.5 m. The water quality reaches Class I levels according to the Environmental Quality Standards for Surface Water(GB 3838-2002).A comprehensive survey of diatoms was made in Lugu Lake. A total of 111 taxa of diatoms were identified, including 103 species and 8 varieties, which belong to 2 classes, 6 orders, 10 families and 51 genera. And of these taxa 2 genera 2 species were newly recorded from China, namely Aneumastus minor and Placoneis humilis. For the two newly recorded species, the morphological characteristics, habitats and distributions were described in detail in this article.

Skeletonema is a globally distributed wide-temperature and wide-salt planktonic diatom genus.It is frequently found in coastal estuaries and marine environments.In recent years, it has also appeared in freshwater.The species of Skeletonema can be used as bait, biodiesel feedstock and cancer drug candidates, and it is also a type of algae that can cause red tides.This article reviewed the research progress of Skeletonema in systematic taxonomy, ecology, and physiology, their research prospections were given as well.

In this paper we inventory the continental diatom taxa described from inland waters in China, from the first species descriptions dating back to 1848 through 2019. China’s geography and hydrography are complex, including the world’s highest mountains, many large rivers, salty lakes, and large karst regions. From this area, a total of 1128 taxa have been described from China over this time period. We examine the number of taxa described in ca. 20-year intervals and note the periods of time of no to few descriptions, versus time intervals with many taxon descriptions. Early on, taxon descriptions of freshwater diatoms from China were done by mostly by Europeans working alone, and the time frame of 1948 to 1967 had few descriptions, as a devasting famine and the cultural revolution impacted scientific work and productivity. B.V. Skvortzov produced a large number of taxon descriptions, during his time in residence in Harbin, later while in Sao Paulo, Brazil, and even posthumously. More recently, a wide range of labs and collaborations across China, and with a diverse array of international partners, is ushering in a new, robust era of research on the biodiversity of continental diatoms. A few areas of research and work for the future are discussed.