Institute of Hydrobiology, Chinese Academy Of Sciences
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Comparison of Community and Function of Dissimilatory Nitrate Reduction to Ammonium (DNRA) Bacteria in Chinese Shallow Lakes with Different Eutrophication Degrees
No full textDissimilatory nitrate reduction to ammonium (DNRA) plays an important role in controlling nitrogen (N) loading in lake ecosystems. However, studies on the linkage between DNRA bacterial community structure and lake eutrophication remain unclear. We examined the community and abundance of DNRA bacteria at six basins of four shallow lakes with different degrees of eutrophication in China. Measurements of the different forms of N and phosphorus (P) in the water column and interstitial water as well as total organic carbon (TOC) and sulfide in the sediments in summer (July 2016) were performed. The nutritional status of Lake Chaohu was more serious than that of the lakes in Wuhan, including Lake Qingling, Lake Houguan, and Lake Zhiyin by comparing geochemical and physical parameters. We found a higher abundance of the nrfA gene, which is a function gene of DNRA bacteria in sediments with higher contents of TOC and sulfide. Moreover, nitrate was a significant factor influencing the DNRA bacterial community structure. A significant difference of the DNRA bacterial community structure between Lake Chaohu and the lakes in Wuhan was discovered. Furthermore, DNRA bacterial abundance and community positively correlated with NH4+ and Chl a concentrations in Lake Chaohu, in which a percent abundance of dominant populations varied along eutrophication gradients. Overall, the abundance and community structure of the DNRA bacteria might be important regulators of eutrophication and cyanobacteria bloom in Lake Chaohu
Interspecific competition between Cylindrospermopsis raciborskii and Microcystis aeruginosa on different phosphorus substrates
No full textPhosphorus (P) is responsible for algal growth and the structural changes in algal communities. Therefore, it is essential to know whether the different phosphorus availability to different algae can change the community structure. In this study, the interspecific competition was investigated at two bloom-forming cyanobacterium, Cylindrospermopsis raciborskii and Microcystis aeruginosa, when both were treated with five different phosphate compounds, including K2HPO4, beta-glycerol phosphate, (2-aminoethyl)-phosphinic acid, glyphosate, and P-free. The results of mono-culture experiments showed that the two species could utilize the dissolved organic phosphorus (DOP) and K2HPO4 (DIP) as the sole P resource. Moreover, the specific growth rates and the endogenous alkaline phosphatase activity in M. aeruginosa cells were much lower than those in C. raciborskii under DOP and DIP treatments. In the co-cultured experiments, however, a significant biomass increase in C. raciborskii was observed in all experimental P treatments, except for glyphosate, regardless of its initial cell density proportion. A 31.8-63.4% increase in cell number of C. raciborskii was found after incubated into K2HPO4, while the highest biomass of mixed samples, 17.72 x 10(6) cell mL(-1), was observed in the (2-aminoethyl)-phosphinic acid treatment (50C50M). Additionally, higher specific growth rate was also found in C. raciborskii when compared with M. aeruginosa under P-free; the increasing proportion of C. raciborskii were 29.1% (50C50M), 16.4% (75C25M), and 36.7% (25C75M), respectively. When the mixed samples were co-cultivated under glyphosate, C. raciborskii cells appeared to be depressed, whereas the cell density of M. aeruginosa increased rapidly. The findings indicated that an excellent P competition might give some advantages for C. raciborskii dominance in natural waters with DIP limitation or DOP abundance
Synergistic toxicity of microcystin-LR and Cu to zebrafish (Danio rerio)
No full textToxic cyanobacterial blooms often coincide with metal pollution in a freshwater environment because of surface run-off enriched with nutrients and metals. However, the joint toxic effects of cyanobacterial toxins and metals on aquatic animals remain unknown. In this study, single and joint toxic effects and mechanisms of microcystinLR (MCLR) and copper (Cu) were investigated in the early development of zebrafish (Danio rerio). The LC50(72)(-h) values were 2.79 mg/L for MCLR and 3.23 mg/L for Cu. The sublethal concentrations of MCLR (<= 600 mu g/L) did not affect the normal development of zebrafish but increased its hatchability. Strong synergistic toxic effects were observed after co-exposure to MCLR and Cu at environmental concentrations (<= 60 mu g/L). The synergistic toxic effects of these two compounds could be attributed to the increased bioaccumulation of MCLR and Cu, which was mediated by MCLR transporters (e.g., oatp1d1 and oatp2b1) and Cu transporters (e.g., ctr1 and atp7a), in zebrafish. Such bioaccumulation caused oxidative stress, as suggested by the disrupted gene expression of anti-oxidative enzymes (e.g., Cu/Zn-SOD, Mn-SOD, and CAT). Our results revealed for the first time the synergistic toxic effects and potential toxic mechanism of MCLR-Cu in aquatic animals. These synergistic effects should be considered when assessing the ecological risk of toxic cyanobacterial blooms. (C) 2019 Published by Elsevier B.V
Effects of warming, climate extremes and phosphorus enrichment on the growth, sexual reproduction and propagule carbon and nitrogen stoichiometry of Potamogeton crispus L
No full textContemporary evidence suggests that submerged macrophytes are experiencing a global decline due to the multiple compounding anthropogenic stressors impacting shallow lake ecosystems. Eutrophication and climate change are two main widespread, often co-occurring stressors, yet evidence concerning their interactive effects on aquatic plants remains partial and fragmented. Predicting the response of submerged aquatic vegetation to the combined effects of nutrient pollution and compound climate warming (mean + variability) is therefore crucial for the conservation and management of these valuable and vulnerable ecosystems. Here, we present the results of an outdoor mesocosm experiment examining the combined effects of nutrient enrichment (phosphorus addition) and warming (a 4 degrees C increase in mean temperature above present ambient conditions applied as either a constant increase or a variable increase ranging between 0 and 8 degrees C to mimic the effect of extreme events but keeping an equivalent total amount of warming) on Potamogeton crispus L. Warming accelerated the growth and senescence of P. crispus suggesting a more important role in maintaining the clear water state in winter-early spring but concomitant to possible earlier turbid states in summer. Warming also consistently advanced the flowering phenology but had no significant effect on flowering duration. There were no significant differences in the life cycle between the two warming treatments, while phosphorus addition also had little effect. However, under phosphorus enrichment, P. crispus increased sexual reproduction investment producing higher seed setting rate per infructescence. In contrast, warming, especially variable warming, may decrease sexual reproduction investment by reducing the number of infructescences. Seed and turion stoichiometry were altered by the combination of warming and phosphorus addition, but the changes were complex and difficult to interpret
Swimming features in captive odontocetes: Indicative of animals' emotional state?
No full textCaptive welfare studies in odontocete species have been mostly conducted on bottlenose dolphins (Tursiops truncatus) while the welfare of many other species' -including endangered species- remains poorly studied. More research is needed to find and validate potential indicators of welfare for each species and even for each group. Since captive odontocetes spend most of their time swimming, their swimming features are interesting to study in relation to their welfare state. We first analysed the circular swimming direction bias in three groups of captive odontocetes (Yangtze finless porpoises: Neophocaena asiaeorientalis asiaeorientalis; East-Asian finless porpoises: N. a. sunameri; and bottlenose dolphins, Tursiops truncatus). Second, we studied the effect of environmental and social factors (i.e., time of the day, delay to training, enrichment, potential perturbation, social grouping, public presence and housing pool) on circular swimming, fast swimming, group swimming, synchronous swimming and contact swimming in the three groups. Yangtze finless porpoises exhibited a clockwise swimming bias while East-Asian finless porpoises and bottlenose dolphins swam significantly more in the counter-clockwise direction. Each studied factor significantly impacted the animals' swimming behaviour slightly differently depending on the group. However, some patterns were common for the three groups: animals seemed to be more active in the morning than at noon and in the afternoon, and enrichment seemed to decrease circular swimming, fast swimming and social swimming (i.e., synchronous, contact and group swimming), while potential perturbations (e.g., pool cleaning, noise) seemed to increase it. In addition, behaviour differed for Yangtze finless porpoises and bottlenose dolphins right before the training or when other animals were being trained, suggesting an anticipation of this event or an excited/frustrated state in this context. Social separation also impacted these animals' swimming behaviour with less group swimming but more circular swimming, synchronous swimming and fast swimming when separated. The housing pool had an impact on bottlenose dolphins' behaviour with more circular swimming, more fast swimming and less group swimming when having access to a larger space. The effect of the presence of public was unclear and requires further investigation. From our results, we propose that circular swimming, synchronous swimming and contact swimming could be useful to monitor animals' emotional state, but that additional parameters should be added (e.g., swimming speed) since these behaviours can be expressed both in quiet and relaxed contexts and in stressful ones. In addition, fast swimming can be a useful indicator of stress for porpoises but might be more ambiguous for bottlenose dolphins that engage in intense social play bouts for instance. Finally, group swimming might be a good behaviour to monitor when wanting to investigate reactions to various conditions or events that can potentially be stressful. We suggest that further research should be conducted on other groups of odontocetes to validate our findings
Phylogenetic characterisation of seven Unicapsula spp. (Myxozoa: Myxosporea: Multivalvulida) from commercial fish in southern China and Japan
No full textThe myxozoan genus Unicapsula Davis, 1924 (Myxosporea: Multivalvulida: Trilosporidae) is characterized as having one functional polar capsule (PC) and two rudimentary PCs in a three-valved myxospore. The plasmodia of Unicapsula spp. grow either in the myofibres or in the gills, oesophageal walls and urinary organs of marine fish. Few studies have investigated the taxonomy of Unicapsula spp. including the type species Unicapsula muscularis. Accordingly, the taxonomy of the genus was explored in the present study by using 15 new isolates of seven Unicapsula spp. (U. muscularis, U. galeata, U. andersenae, U. pyramidata, U. pflugfelderi, and two new species) that had formed pseudocysts in the trunk myofibres of commercial fish collected in southern China and Japan from November 2015 to January 2019. Two new species Unicapsula trigona n. sp., and Unicapsula motomurai n. sp. exhibited unique myxospore morphologies (semi-triangular and spherical myxospores, respectively) and 18S and 28S rDNA sequences that were distinct from those of the other Unicapsula spp. Phylogenetic analysis of the 18S and 28S rDNA sequences confirmed the monophyletic status of Unicapsula
SIRT5 impairs aggregation and activation of the signaling adaptor MAVS through catalyzing lysine desuccinylation
No full textRLR-mediated type I IFN production plays a pivotal role in innate antiviral immune responses, where the signaling adaptor MAVS is a critical determinant. Here, we show that MAVS is a physiological substrate of SIRT5. Moreover, MAVS is succinylated upon viral challenge, and SIRT5 catalyzes desuccinylation of MAVS. Mass spectrometric analysis indicated that Lysine 7 of MAVS is succinylated. SIRT5-catalyzed desuccinylation of MAVS at Lysine 7 diminishes the formation of MAVS aggregation after viral infection, resulting in the inhibition of MAVS activation and leading to the impairment of type I IFN production and antiviral gene expression. However, the enzyme-deficient mutant of SIRT5 (SIRT5-H158Y) loses its suppressive role on MAVS activation. Furthermore, we show that Sirt5-deficient mice are resistant to viral infection. Our study reveals the critical role of SIRT5 in limiting RLR signaling through desuccinylating MAVS.</p
General trends in freshwater ecological restoration practice in China over the past two decades: the driving factors and the evaluation of restoration outcome
No full textBackground Although freshwater ecological restoration (FER) has undergone an immense development over the past two decades in China either in the number of projects or in the spatial scale of implementations, a dearth of clear and comprehensive trends in this field is still a particular concern. We conducted a literature survey through searching the database of Web of Science between 1997 and 2017 to investigate the driving force behind FER practice and to summarize the restoration outcomes. Results A total of 2047 publications were hit and 198 of them were finally retained after manual screening. The number of studies in this field has been steadily increasing in recent years and their provincial distribution is positively correlated with GDP growth and the investment to pollution control and environmental protection, suggesting that economic development is a key driving factor of FER practice. Among the remaining articles, nearly half (46.5%) focus on lake ecosystems, and 34.8% and 32.8% of the studies indicate that land reclamation and eutrophication are the predominant causes of freshwater ecosystem degradation. The overarching target of the restoration is biodiversity increase (31.4%), followed by water quality improvement (24.7%) and ecosystem services (23.9%). Revegetation is a dominant restoration approach (40.9%). Reference sites for assessment of restoration projects are normally control locations without intervention (60%), or the status of the targeted sites before the interventions. For the restoration outcome evaluation, 86% of the studies present positive outcomes in terms of water quality improvement, and 79% have improvement in biological features. The most frequently monitored organisms are macrophytes (31%), followed by benthos as indicators of ecological condition. Conclusions Economic growth, water pollution and investment into environmental protection are the main driving factors of FER practice in China. The effort of restoration and evaluation over the past two decades has not been limited to improving hydrological function and water quality, but also pay increasingly more attention to biological processes and ecological integrity, and further the ecosystem services in recent years. However, the lack of long-term monitoring and socioeconomic attributes considered in restoration success assessments are still particular issues that need to be addressed in the future FER researches and projects
An OLCI-based algorithm for semi-empirically partitioning absorption coefficient and estimating chlorophyll a concentration in various turbid case-2 waters (vol 239, 111648, 2020)
No full textInteractions between dicyandiamide and periphytic biofilms in paddy soils and subsequent effects on nitrogen cycling
No full textDicyandiamide (DCD) is commonly used as nitrification inhibitors which has the potential to reduce nitrogen loss from paddy soils. In paddy systems, periphytic biofilms are commonly presented at the soil/water interface and show significant effects on nutrient cycling. However, the interaction between DCD and periphytic biofilms in paddy and subsequent effects on nitrogen cycling is unclear. In this work, microcosm experiments were carried out to study the interaction between the periphytic biofilms and DCD and the potential influence on nitrogen cycling from in paddy. Results showed that DCD affected the development of periphytic biofilms, while the presence of periphytic biofilms accelerated DCD degradation. Results also showed DCD application reduced nitrification potential mainly by inhibiting ammonia-oxidizing bacteria (AOB). Higher DCD dosage increased NH3 volatilization loss. However, presence of periphytic biofilm reduced the NH3 volatilization loss but increased denitrification. Our work contributes to a better understanding on the nitrogen cycling processes in paddy, and provides useful information for the improvement of nitrogen utilization efficiency and the control of non-point source pollution. (C) 2020 Elsevier B.V. All rights reserved