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Abstract: Located in the Yunnan–Guizhou Plateau in southwest China, Fuxian Lake covers an area of 211km2, with maximum depth of 155m. It is known to have a unique fauna, including 14 described endemic species. In order to describe the zoobenthic community of the lake more completely, the present study was conducted from August 2002 to August 2003. Altogether 62 benthic taxa, including 22 oligochaetes, 21 molluscs and 18 insects were identified, of which the dominant taxa belonged to Potamothrix, Procladius and Paraprososthenia. The standing stocks of benthos were much higher in the littoral (824ind/m2 in density, 3.72g/m2 in biomass) than in the profundal region (23ind/m2 in density, 0.10g/m2 in biomass). Species richness was greatest in summer and standing stocks were larger in spring and summer than in other seasons. Analyses of functional feeding groups indicated that collector-gatherers and scrapers were predominant in entire lake. Stepwise multiple regression analysis demonstrated that the water depth is the most important factor affecting the distribution of macrozoobenthos. [Copyright &y& Elsevier]

Abstract: The farming of Chinese mitten crab, a quality aquatic product in China and neighbouring Asian countries, has been developing rapidly in China since last decade. It reached a total yield of 3.4×105 tonnes in 2002. Due to the successive over-stocking year after year, many lakes in the mid-lower Yangtze Basin, the main farming area, are under deterioration, leading to a reduction of crab yield and quality, and, subsequently, a loss of farming profits. Aiming at a normal development of crab culture and the sustainable use of lakes, an annual investigation dealing with lake environmental factors in relation to stocked crab populations was carried out at 20 farms in 4 lakes. The results show that the submersed macrophyte biomass (B Mac) is the key factor affecting annual crab yield (CY). Using the ratio of Secchi depth to mean depth (Z SD / Z M), an easily measured parameter closely correlated to B Mac, as driving variable, 10 regression models of maximal crab yields were generated (r 2 ranging 0.49–0.81). Based on the theory of MSY (Maximum Sustainable Yield), in combination with body-weight (BW) and recapture rate (RR) of adult crabs, a general optimal stocking model was eventually formulated. All models are simple and easy to operate. Comments on their applications and prospects are given in brief. [Copyright &y& Elsevier]

The management of water levels in wetlands is of great importance for the wetland ecosystem, including the conservation and revitalization of plants. However, the water level requirements (WLRs) of wetland plants have not been well investigated. In this study, Typha angustifolia was selected as an experimental plant species. Combining field investigation and simulation experiments, the relationship between the development status of this species and water level fluctuations (WLFs) in different life-history stages were analyzed. The results show that populations in the Yangtze floodplain, China, had two phenotypic forms 'tall' and 'short', and that these were distributed in lakes with intermittent or quasi-natural fluctuations and reservoir-like fluctuations, respectively. Lakes with high amplitude (>3.2 m) water fluctuations did not contain T. angustifolia. We investigated the distribution and growth of T. angustifolia in lakes of varying hydrology across the Yangtze floodplain, seeking to define its tolerance of water-level fluctuations and submergence at different stages in its life cycle. The upper tolerance limit of static submerged water depth was bounded by 1.5 times the height of plants in the seedling stage, and the upper tolerance limit of the submergence rate in the seedling stage was the average growth rate of seedling, 1.5 cm/d. The plant height had a positive linear correlation with amplitude and water depth from June to July. The autumn biomass was significantly negatively correlated with amplitude and water depth from January to May. This paper is perhaps the first case study on water level fluctuation requirements (WLFRs) of emergent macrophytes. It systematically assessed the WLFRs of T. angustifolia in each life-history stage, and established a comprehensive WLFR conceptual model. The results of this study could provide a quantitative operational basis for the protection and restoration of this species in Yangtze floodplain lakes. [ABSTRACT FROM AUTHOR]

Dolman (2014) argued that our recent finding (Wang et al., 2014) of no marked effect of submerged macrophytes on the chlorophyll a (Chl a) to total phosphorus ( TP) relationship in Yangtze subtropical lakes may not necessarily be valid due to the statistical procedure used to analyse the relationship between these two variables., We agree with Dolman (2014) that a likelihood ratio test could provide an alternative statistical approach to analyse the effect of macrophytes on Chl a versus TP. However, we do not consider it would be appropriate to use the test on only a limited sub-data set corresponding to where TP values overlap for the vegetated and non-vegetated states, as suggested by Dolman (2014)., Besides testing slopes of the log10(Chl a)-log10( TP) relationship, we compared log10(Chl a)/log10( TP) values between vegetated and non-vegetated lakes at a range of overlapping TP concentrations (Wang et al., 2014)., The conclusion drawn by Dolman (2014) from a highly cited work on subtropical lakes in Florida was shown to be invalid. Re-analysis of these lakes demonstrated similar results to those found in Yangtze subtropical lakes. We therefore consider that our original conclusions are valid and that submersed macrophytes in subtropical lakes do not necessarily exert the same strong effects on algal turbidity as in temperate lakes. [ABSTRACT FROM AUTHOR]

In aquatic ecosystems, light penetrating the sediment surface in shallow lakes may regulate the internal phosphorus (P) release through benthic primary production, which subsequently affects oxidation, pH levels, and alkaline phosphatase activity in the upper sediment. To study the effects of light exposure on the P dynamics at the sediment-water interface under eutrophic conditions, a two-month mesocosm experiment was conducted in twelve cement tanks (1000 L each). The tanks were equipped with Light-Emitting Diode (LED) lights, and surface sediments collected from eutrophic Lake Nanhu (China) were exposed to four different light intensities (0, 50, 100, 200 μmol m -2 s -1 ). The results revealed that: 1) Both the total phosphorus concentration and the phosphorus release flux from the sediment were lower in the light treatments (mean value, 0.59-0.71 mg L -1 and 0.00-0.01 mg m -2 d -1 , respectively) than in the control treatment (0.77 mg L -1 and 0.01 mg m -2 d -1 , respectively), indicating that light supplement could decrease the internal P release. 2) Benthic primary production promoted by light directly absorbed soluble reactive phosphorus and decreased the internal P release. The resulting improved production could also increase dissolved oxygen concentrations at the sediment-water interface, thus indirectly inhibiting internal P release. 3) The relative contributions of direct absorption and indirect inhibition on the internal P release ranged between 23% to 69% and 31% to 77% depending on the light intensity., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

The unprecedented global increase in the anthropogenic-derived nitrogen (N) input may have profound effects on phosphorus (P) dynamics and may potentially lead to enhanced eutrophication as demonstrated in short-term mesocosm experiments. However, the role of N-influenced P release is less well studied in large-scale ecosystems. To gain more insight into ecosystem effects, we conducted a five-year large-scale experiment in ten ponds (700-1000 m 2 each) with two types of sediments and five targeted total N concentrations (TN) by adding NH 4 Cl fertilizer (0.5, 1, 5, 10, and 25 mg N L -1 ). The results showed that: (ⅰ) The sediment P release increased significantly when TN exceeded 10-25 mg N L -1 . (ⅱ) The most pronounced sediment P release increase occurred in summer and from sediments rich in organic matter (OM Sed ). (ⅲ) TN, algal biomass, fish biomass, non-algal turbidity, sediment pH, and OM Sed were the dominant factors explaining the sediment P release, as suggested by piecewise structural equation modeling. We propose several mechanisms that may have stimulated P release, i.e. high ammonium input causes a stoichiometric N:P imbalance and induce alkaline phosphatase production and dissolved P uptake by phytoplankton, leading to enhanced inorganic P diffusion gradient between sediment and water; higher pelagic fish production induced by the higher phytoplankton production may have led increased sediment P resuspension through disturbance; low oxygen level in the upper sediment caused by nitrification and organic decomposition of the settled phytoplankton and, finally, long-term N application-induced sediment acidification as a net effect of ammonium hydrolysis, nitrification, denitrification; The mechanisms revealed by this study shed new light on the complex processes underlying the N-stimulated sediment P release, with implications also for the strategies used for restoring eutrophicated lakes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Phosphorus (P) release from sediment is a key process affecting the effectiveness of eutrophication mitigation. We hypothesized that high nitrate (NO 3 - ) input may have dual effect on sediment P release: reduce the sediment P release by improving the oxidation of sediment or promote P release by stimulating the growth of phytoplankton and increase the decomposition rates and oxygen consumption at the sediment water interface. To test the effect of different NO 3 - concentrations, we conducted a three-month experiment in 15 cement tanks (1 m 3 ), with five targeted concentrations of NO 3 - : control, 2 mg L -1 , 5 mg L -1 , 10 mg L -1 , and 15 mg L -1 . The results showed that: i) when NO 3 - was maintained at high levels: NO 3 - ≥5-7 mg L -1 (range of median values), there was no effect of NO 3 - on net P release from the sediment, likely because the positive effects of NO 3 - (increasing oxidation) was counteracted by a promotion of phytoplankton growth. ii) after NO 3 - addition was terminated NO 3 - dropped sharply to a low level (NO 3 - ≤0.4 mg L -1 ), followed by a minor P release in the low N treatments but a significant P release in the high N treatments, which likely reflect that the inhibition effect of NO 3 - on P release decreased, while the promotion effects at high NO 3 - concentrations continued. The results thus supported our hypotheses of a dual effect on sediment P release and suggest dose-dependent effect of NO 3 - loading on stimulating P release from the sediment, being clear at high NO 3 - exceeding 5-7 mg L -1 ., Competing Interests: Declaration of Competing Interest No conflict of interests needs to be declared for the manuscript entitled., (Copyright © 2021. Published by Elsevier Ltd.)

Potamothrix scleropenis sp. nov. (Tubificidae: Tubificinae) is described from the profundal zone (74 m) of Fuxian Lake, the deepest lake (up to 155 m) on the Yunnan-Guizhou Plateau in China. The new species is assigned to Potamothrix because of its short vasa deferentia and its tubular atria without ejaculatory ducts and prostate glands. It differs from congeners by its cuticularized penis sheaths; bifurcated, strongly curved spermathecal chaetae; bifurcated lower prongs of bifids; and feathered hairs. P. scleropenis appears closely related to P. cekanovskajae Finogenova, 1972 and P. tudoranceai Sporka, 1994, since all the three species have homogeneous atria without prostate glands.