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Research on climate change, water quality, and their relationship is critical for human survival and development. It can help better mitigate climate change and contribute to appropriate water quality management strategies under uncertain challenges in the future. In this study, bibliometric analysis was used to provide a comprehensive review of the research field of climate change and water quality from 1990 to 2022. The extraction of documents was carried out from the Web of Science Core Collection database. VOSviewer, Bibliometrix R-package, and CiteSpace were used for analysis and scientific mapping. The results show that China, the United States, and Canada are the main countries driving this field, and China and the United States closely cooperate. It was also found that the areas of water eutrophication and climate change research had a close relationship and were the current research hotspots. Finally, it is revealed that the areas of sustainable development of climate change and water quality management, model simulation and method improvement between climate change and water quality, groundwater quality risk assessment driven by climate change, the impact of water on climate change, and expanding the research scale of the relationship between climate change and water quality will be the future research trends in this field. [ABSTRACT FROM AUTHOR]

In Asia, especially in China, our knowledge of the distribution of testate amoebae is still limited. In this paper, the geographical distribution of testate amoebae in Tibetan Plateau and northwestern Yunnan Plateau, southwest China and their relationships with the climatic factors have been studied. We found testate amoebae shifted in the most dominant species and increased in species (or genus) richness from northwest to southeast. Further, the linear regression analyses revealed that both species richness and genus richness have higher positive correlations with the mean temperature of the warmest month and annual mean precipitation as contrasted with the mean altitude, which showed weak negative correlation. This indicates that the temperature and precipitation are more significant influences on the richness than the altitude. The cluster analysis based on the community structure, defined by Sørenson’s coefficient matrix, suggested four groups from the 10 physiographical regions. This geographical distribution pattern was also closely related with the climatic regionalization. The present climatic regionalization pattern of the study area originated from the uplift of Tibetan Plateau and mainly occurred in or after the late Pleistocene. Therefore, the geographical distribution of testate amoebae in our study area may have experienced complicated and drastic changes corresponding to the variation of the climate caused by the geological events. [ABSTRACT FROM AUTHOR]

The megalopteran genus Neoneuromus Weele is a small genus with 8 known species, which are mainly distributed in the Oriental Realm. In the present paper, the species of the genus from China are revised. Four species are described, keyed and illustrated. Among them 1 species is new to science. Geographic distributions are updated and discussed. [ABSTRACT FROM AUTHOR]

Undaria pinnatifida (Harv.) Sur. is one of the three main seaweed species under commercial cultivation in China. In the mid-1990s the annual production was about 20 000 tons dry. The supply of healthy sporelings is key to the success of commercial cultivation of Undaria. Previous studies demonstrated that instead of the zoospore collection method, sporelings can be cultured through the use of gametophyte clones. This paper reports the experimental results on mass culture of clones and sporeling raising in commercial scale. Light had an obvious effect on growth of gametophyte clones. Under an irradiance of 80 μmol m-2 s-1 and favorable temperature of 22–25 °C, mean daily growth rate may reach as high as 37%. Several celled gametophyte fragments were sprayed onto the palm rope frame. Gametogenesis occurred after 4–6 days. Juvenile sporeling growth experiments showed that nitrate and phosphate concentrations of 2.9 10-4 mol l-1 and 1.7 10-5 mol l-1 were sufficient to enable the sporelings to maintain a high daily growth rate. Sporelings can reach a length of 1 cm in a month. Since 1997, extension of the clone technique has been carried out in Shandong Province. Large-scale production of sporelings for commercial cultivation of 14 and 31 hectares in 1997 and 1998 had been conducted successfully. [ABSTRACT FROM AUTHOR]

In this paper, four new species of malacocarpic Sargassum are described: S. fuliginosoides Tseng et Lu sp. nov. is characterized by its discoid holdfast, the presence of the bulbs on the basal parts of the primary branches and very thick, lanceolate leaves. S. gemmiphorum Tseng et Lu sp. nov. is characterized by its conical holdfast, usually branched axis and very long, narrow, thin, denticulate leaves. S. shandongense Tseng, Zhang et Lu sp. nov. is characterized by its discoid holdfast, flattened primary branches, its leaves mostly entire or wavy at the margins and its racemose to paniculate receptacles. S. qingdaoense Tseng et Lu sp. nov. is characterized by the presence of the glandular dots on the ultimate branches and elongated lanceolate, acute, mostly wavy leaves. [ABSTRACT FROM AUTHOR]

The year 1998 was an unusual year for Guangdong Province and Hong Kong, both in southern China, as the frequency and intensity of harmful algal blooms (HAB) were much higher than usual. This paper describes the causative organisms found associated with these blooms and speculates on the possible causes of these blooms, including the effects of increased temperature, reduced salinity, eutrophication and meteorological and oceanographic events on the initiation and spread of these blooms. [ABSTRACT FROM AUTHOR]

Eutrophication has been considered to be undoubtedly one of the key factors stimulating phytoplankton growth, since it involves the enrichment of a water mass with both inorganic and organic nutrients supporting plant growth. Nutrient enrichment as a result of anthropogenic activity occurs in estuaries and coastal waters as well as in lakes and freshwater impoundments, and blooms of phytoplankton are one of the effects of such an accelerated process of nutrient enrichment. This paper presents the results of a two-year survey of the nutrients and phytoplankton at 3 stations in Junk Bay, Hong Kong, carried out from 1997 to 1998. The relationships between nitrogen, phosphorus, and their ratio, with phytoplankton abundance have been studied. The results show that the highest nitrogen concentration was in Station 2 which is close to a sewage input, whereas the highest phosphorus concentration was in Station 1 which is close to a landfill area. The mean N:P ratios at the three stations were between 8 and 14. The diatoms were the dominant group during most of the year but it seems that diatoms were more sensitive than dinoflagellates and other algal groups to the increase in nutrients. [ABSTRACT FROM AUTHOR]

The temporal and spatial distribution of total nitrogen and total phosphate in the sediments of a shallow eutrophic Chinese lake (Lake Chao), and their relationships with the physical and chemical features of sediments, and their effects on the lake water quality and trophic state, are presented in this paper. The following results were obtained: (1) higher concentration of Tot-N and Tot-P in the sediments occurred in the summer and the autumn seasons; (2) higher annual average Tot-N and Tot-P concentrations were observed in the sediments near the various river mouths and in the western part of the lake; (3) Tot-N and Tot-P concentration in the lake sediments generally increased with increase in lake sediment Eh, pH, and Al2O3, and declined with decrease in lake sediment size diameters and SiO2; and, (4) correlations were observed in both the temporal and spatial distributions between the trophic state, Tot-N and Tot-P concentration in the lake water, and the Tot-N and Tot-P concentration found in the lake sediments. [ABSTRACT FROM AUTHOR]

In temperate shallow lakes, submerged macrophytes facilitate zooplankton development by providing refuge against fish predation and, thereby, indirectly contribute to maintaining a clear-water state through enhanced zooplankton grazing. The role of macrophytes for zooplankton and their grazing potential is less clear for tropical lakes. We investigated crustacean zooplankton in a phytoplankton-dominated basin (algal basin) and two restored basins dominated by macrophytes (macrophyte basins) in the shallow Huizhou West Lake in tropical southern China. We found that copepods prevailed in all basins, but the dominant taxon differed, with omnivorous cyclopoids dominating in the algal basin and herbivorous calanoids in the macrophyte basins. Moreover, the biomass ratios of calanoid:copepod and zooplankton:phytoplankton were higher in the macrophyte basins than in the algal basin. Our results suggest that restoration measures involving macrophyte transplantation and fish removal lead to reduced fish predation on zooplankton, which help to maintain the clear-water state when macrophytes are established due to higher control on phytoplankton. However, unlike in temperate lakes, large-bodied Daphnia were generally absent and the zooplankton:phytoplankton ratio was overall low, indicating a weaker top-down control in tropical lakes, which is likely due to higher fish predation. [ABSTRACT FROM AUTHOR]

Using unregulated tributaries to compensate fish habitat loss in dammed mainstreams has recently been suggested as a promising strategy for river ecological restoration. One critical prerequisite is to find potential tributaries as alternative habitat, which depends on precise fish community surveys. In this study, both eDNA metabarcoding and electrofishing were used to characterise fish community compositions in the dammed lower Jinsha river and its tributaries (Heishui, Pudu, and Xiaojiang rivers) in China. The fish community composition detected by eDNA metabarcoding was consistent with that detected by the conventional method. Besides, metabarcoding has the advantage of detecting the presence of rare species with relatively low abundances. The non-metric multidimensional scaling showed that there was no significant difference in fish community composition between the mainstream and the Heishui river, while there was large difference in the fish community composition between the mainstream and other tributaries. The effectiveness of using the Heishui river as alternative fish habitat was verified by comparing the changes in fish communities before and after the impoundment of the mainstream. Taken together, this study indicates that eDNA metabarcoding is a viable method to identify the suitable tributaries which at least partly compensate for fish habitat loss in the dammed mainstream. [ABSTRACT FROM AUTHOR]

Identifying the spatial patterns of fish diversity is essential for the conservation and management of stream fishes. Many studies highlight the need to comprehensively consider diversity rather than a unique index to enact conservation strategies. However, understanding spatial patterns along environmental gradients and the correlation of multifaceted diversity in stream fish communities remains limited. Thus, we surveyed fishes along an upstream–downstream gradient in the Qiupu River, an important tributary of the Yangtze River, China. We aimed to explore the spatial variation and congruence of the multifaceted diversity of fish communities, as measured by taxonomic (TR), functional (FR), and phylogenetic (PR) richness, along the longitudinal gradient. Both TR and PR had a positive linear relationship with distance from the headwaters, although this trend was not significant for FR due to functional trait redundancy. There was high spatial congruence between TR and PR but relatively low-congruence between TR and FR. Spatial autocorrelation patterns were identified for TR and FR, but not for PR. Our results suggest that along the continuum, each diversity metric reflected different spatial patterns, and the results support the importance of using multiple facets of diversity in assessing community structure and developing conservation strategies. [ABSTRACT FROM AUTHOR]

In China, the invasive macroalga Chaetomorpha valida exerts significant negative effects on the composition of biotic communities and the balance of the ecological environment. C. valida can respond to changes in inorganic N/P ratios in the environment by regulating the activity of enzymes related to nitrogen (N) and phosphorus (P) metabolism and enhancing its N and P assimilative capacity, which may enable it to outcompete many native species. This study experimentally assessed the response of the activity of enzymes associated with N and P metabolism to different N/P ratios. Significantly higher activities of nitrate reductase, nitrite reductase, glutamate synthase and glutamine synthetase were obtained with the treatments with N/P ratios of 0/0, 2.5/1 and 5/1 (P < 0.01). All the P concentrations tested activated the alkaline phosphatase activities of C. valida, particularly in the absence of N and P (P < 0.01). C. valida does not experience severe effects of nutrient limitation leading to growth inhibition. This successful invasion of C. valida proves its strong adaptability to complex environments and indicates its competitive advantage over other native species in the same inorganic N and P environment. [ABSTRACT FROM AUTHOR]

The functional group (FG) system sensu Colin S. Reynolds of freshwater phytoplankton has been widely applied in many aspects of freshwater ecological assessments. However, there is no current consensus as to how and to why some functional coda shows multiple habitat templates in different water bodies. To test whether there are multiple habitat templates for some functional coda in the FG system, we used two mesotrophic deep reservoirs in China as examples, analysing phytoplankton taxonomic and environmental data collected in 4 seasons over two years. Results showed that a large proportion of the indicators had similar habitat templates within the FG system, whilst some species had multiple or different habitat templates according to their niche differentiation. The random forest (RF) model filtered a minimum set of environmental conditions and provided two potential habitat templates for Oocystis lacustris. One explanatory habitat template of clear water provided by the FG system was verified in the Nanwan Reservoir, and the other habitat template of high dissolved inorganic nitrogen (DIN) was found in the Nianyushan Reservoir. Further studies of the potential multiple habitat templates for some functional coda are recommended for its proper use. [ABSTRACT FROM AUTHOR]

To assess how the presence of an invasive plant and different-sized decomposers affect plant litter decomposition under different seasonal conditions, we allocated leaves of native Ficus virens Aiton into four different mesh sizes (0.025, 0.042, 0.5 and 5 mm) with and without invasive Alternanthera philoxeroides (Mart.) Griseb. We incubated them for 65 days in an eutrophic lake in summer and winter respectively. The average decomposition rate was significantly higher in summer than in winter, and was significantly higher in mixtures than in F. virens monocultures in both seasons. The presence of A. philoxeroides in the mixture significantly increased invertebrate density and microbial respiration rates in summer but not in winter. Furthermore, contribution of invertebrates to decomposition was higher in the early stage of decomposition and lower in the late stage in summer, yet that of microbes was relatively constant in winter. Contribution of microinvertebrates increased in summer but that of meio-, macroinvertebrates increased in winter. Our findings indicate that the presence of an invasive plant altered litter decomposition, which may depend on seasonal variations, invertebrate density and decomposition stages. [ABSTRACT FROM AUTHOR]

Functional traits of exotic species play an important role in their invasive process by enhancing their performance and promoting them as a potentially malignant invasive species. However, the interrelationship between functional traits and invasion capacity of exotic aquatic species is still not clear. Here, we selected two exotic aquatic species Egeria densa Planch. and Myriophyllum aquaticum (Vell.) Verdc. and two related native species Hydrilla verticillata (L. f.) Royle and Myriophyllum spicatum L. in China to reveal the potential invasiveness of exotic submerged macrophytes based on functional traits and their effects on sediment bacterial community. Our results showed that there was no significant competition between exotic species and related native species. Many functional traits of related native species H. verticillata performed significantly better than exotic species E. densa beside leaf area. Related native species M. spicatum also had obvious advantages in important functional traits such as relative growth rate and nutrient concentrations. The belowground part of two exotic species had significant effects on sediment bacterial community. Due to developed roots and their radial oxygen loss of exotic species E. densa and M. aquaticum, the diversity of sediment bacterial community positively correlated with exotic species ratio in treatment. Some dominant sediment bacteria, such as Streptomyces, might accelerate the invasion of exotic species through feedback effects. In general, compared with related native species, the competitive ability and functional traits of exotic plants did not show significant invasion ability. However, positive interaction with sediment bacteria and moderate interspecific relationships may promote the invasion of exotic submerged macrophyte species. Our results provide a theoretical basis for risk assessment and effective management of exotic aquatic plants. [ABSTRACT FROM AUTHOR]

Four new species, Eudesme huanghaiensis Ding et Lu, E. qingdaoensis Ding et Lu, E. shandongensis Ding et Lu and Sphaerotrichia huanghaiensis Ding et Lu, from the western Yellow Sea coast of China are described. Eudesme huanghaiensis is mainly characterized by its spherical or sub-spherical sub-cortical cells, its rhizoidal filaments developing from the basal cells of sub-cortex and its broad sub-cortical and medullary layers. E. qingdaoensis is mainly characterized by its long medullary cells, generally hollow center of the medulla, short sub-cortex with only 3–4 cylindrical cells and long, slender and clavate terminal cells of the rhizoidal filaments. E. shandongensis is mainly characterized by its hollow frond, thick cell walls of both medulla and inner sub-cortical layers and the spherical terminal cells of the rhizoid filaments. Sphaerotrichia huanghaiensis is mainly characterized by its cylindrical, sparsely branched frond with acute angle, and its thick 5–6 layered sub-cortex with long assimilating filaments of 6–10 cells. % [ABSTRACT FROM AUTHOR]

To investigate the effect of invasive Alternanthera philoxeroides mats on native leaf litter decomposition, we allocated two native leaf species of contrasting recalcitrance (Neosinocalamus affinis and Ficus virens) in litterbags with four different mesh sizes (0.025, 0.042, 0.5, and 5 mm) and the bags were either incubated under floating A. philoxeroides mats (Vegetated site) or under floating plastic foam boards without A. philoxeroides mats (Unvegetated site) for 65 days in Jianhu Lake, China, in July 2020. The average decomposition rates increased with pore size of litterbags. The interaction intensity of the site effect in leaf mass loss was negative in 0.025 mesh and positive in other meshes, while no significance existed between two native species in the same mesh sizes and sites. The contribution of microbes to decomposition was more than 50% in both sites. The contribution in the vegetation site was as follows: microbes > microinvertebrates > meioinvertebrates > macroinvertebrates, compared with microbes > macroinvertebrates > meioinvertebrates > microinvertebrates in the unvegetated site. The results suggest that A. philoxeroides mats can promote the decomposition of native leaf litter, and that the roles of micro-, meio-, and macroinvertebrates in decomposition are important but underestimated. [ABSTRACT FROM AUTHOR]

Bolboschoenus planiculmis is a key wetland plant in the semi-arid regions of Songnen Plain, China, providing food and habitat for the endangered Siberian crane. B. planiculmis wetlands are being degraded by water shortages caused by anthropogenic activities and climate changes. However, the vegetation dynamics under hydrological fluctuations have been rarely reported. We conducted a two-year field investigation in B. planiculmis wetlands to determine the vegetation response to water level changes, and a comparative control experiment to examine the restoration effect of supplemental water on degraded community. We found that the community biomass was positively related with water depth under natural conditions, whereas plant diversity and richness were negatively related. The population density, biomass, and root/shoot ratio of B. planiculmis exhibited quadratic relationships with water depth. The optimum ecological threshold of water depth determining B. planiculmis populations was 11.2–36.1 cm. The control experiment demonstrated that water depth at 0–10 cm during the early growing season and 10–25 cm at later growing stages can enhance the dominance of B. planiculmis and help it outcompete other macrophyte species. Understanding the water requirement cycles of B. planiculmis is valuable for guiding water management plans for the rehabilitation of degraded natural wetlands. [ABSTRACT FROM AUTHOR]

Climate change has the potential to greatly alter species distributions and threatens biodiversity in marine ecosystems. Mapping changes in species distribution patterns under climate change will help facilitate management strategies to maintain ecosystem structure and function. The lizardfish Harpadon nehereus is an aggressive predator that has experienced rapid population growth along the coast of China in recent decades, compressing the ecological niches of other marine species and disrupting food webs. If this species' range is shifting due to climate change, it could further impact the integrity of ecological communities. To map the distribution of H. nehereus, we developed an ensemble species distribution model and projected the present and future habitat suitability in Chinese coastal waters. Annual mean benthic water temperature was identified as the most important variable affecting the projected distribution of H. nehereus, followed by water depth and salinity. Currently suitable habitats are along the coast from Guangxi Province to the southern Jiangsu Province. As climate changes, the southern portion of its distribution is predicted to recede with habitat losses, and the overall suitable habitat will shift northward. To avoid the potential impacts of H. nehereus redistribution, precautionary management based on species distribution modeling would help to maintain healthy marine ecosystems in the newly invaded areas. [ABSTRACT FROM AUTHOR]

Phragmites australis is a cosmopolitan plant species with high intraspecific diversity and phenotypic plasticity. Due to its variability and large ecological niche breadth, subgroups of P. australis have become invasive in North America, and this invasion has been recognized late. While this cryptic invasion on the American continent has received much attention, little is known about the potential invasiveness of other subgroups, especially within Asian/Australian P. australis. We therefore compared the performance of three subgroups within the Asian/Australian group: a freshwater (CN) and an estuarine (YRD) subgroup collected in China and a genetically closely related subgroup collected from Australia (FEAU), grown in two common gardens in China. Our results showed that the FEAU subgroup had no strong invasive potential, as its total biomass, height, shoot number, specific leaf area, and stomatal conductance were lower than that of the two native subgroups. All three subgroups responded similarly with most traits to the different climates of the gardens, albeit with different response strength, expressed as phenotypic plasticity indices. The potential cryptic invasion risk of the FEAU subgroup in China seems to be low, since its functional traits showed low competitiveness and most traits with the lowest plasticity occurred in FEAU. However, caution is still advised, because other invasive mechanisms, such as enemy release or the performance under extreme environmental conditions were not tested in our study. [ABSTRACT FROM AUTHOR]

The article discusses eutrophication and algal blooms in lakes as worldwide environmental issues. Due to the strong lake-land, air-water and water-sediment interactions, the eutrophication process and forming mechanisms of algal blooms are particularly complicated in shallow lakes. China has thousands of lakes and nearly a third of them are shallow. Recently, many shallow lakes in China have displayed rapid eutrophication and suffered from algal blooms. These problems have resulted in a shortage of drinking water supply and degradation of lake ecosystems. Lake Taihu, located near Shanghai, is one of the largest and is suffering from economic development and population increases.

The estuarine tapertail anchovy might comprise a "paired species" of Coilia nasus (which has declined sharply) and Coilia brachygnathus (dominant in some lakes). It has previously been debated whether C. nasus and C. brachygnathus constitute two distinct species or anadromous and freshwater-resident ecotypes. Here, we studied the genetic structure of these species by analyzing the mitochondrial gene cytochrome b (Cyt b) and polymorphic microsatellite loci in 184 anchovies and discriminated their migratory life history using otolith microchemical analysis. Bayesian analysis and a discriminant principal components analysis showed two distinct genetic clusters that corresponded to C. nasus and C. brachygnathus, and we revealed the presence of hybridization between the two closely related sister species. C. nasus has higher genetic diversity within a population and lower genetic divergence between populations than C. brachygnathus. No significant genetic differentiation was detected between the migratory and freshwater-resident C. brachygnathus or between the migratory and freshwater-resident C. nasus. These phenomena suggest that C. brachygnathus and C. nasus are different species, and a strong but permeable reproductive barrier may exist. Both these species have migratory-resident ecological dimorphism, and C. brachygnathus is predominantly a resident species, whereas C. nasus is predominantly an anadromous species. [ABSTRACT FROM AUTHOR]

Dramatic environmental changes and species invasions are increasingly threatening the diverse fish fauna of the Yellow River, China. This study examines temporal changes in the alpha and beta components of fish taxonomic, functional and phylogenetic diversity in relation to anthropogenic environmental changes over the past 50 years. We hypothesized that temporal trends in multifaceted components of diversity would be highly congruent, but that the relative importance of anthropogenic disturbances would differ in shaping spatial patterns of fish diversity. We found that all three components of alpha diversity increased over time but at different rates (19.1%, 21.3% and 15.3% for taxonomic, functional and phylogenetic diversity, respectively). Fish faunas of the Yellow River have also become homogenized over time, but this was much greater for functional and phylogenetic components of beta diversity than for taxonomic diversity (change in beta diversity = − 0.11, − 0.24 and − 0.02, respectively). Temporal changes in alpha and beta diversity were strongly related to invasion of non-native fish species and changes in temperature, sediment load, reservoir capacity and aquaculture area. Our results underscore the ongoing need for threat mitigation (particularly relating to dams and aquaculture) to conserve the unique biodiversity of one of the world's largest rivers. [ABSTRACT FROM AUTHOR]

Pomacea canaliculata, a freshwater snail native to tropical and temperate South America, has become an important invader and agricultural pest throughout tropical and subtropical regions around the world. Colonization of various aquatic habitats by P. canaliculata in coastal regions of South China and its establishment potential in estuaries have raised great concern, yet little is known about the biological response of the snail and its tolerance under saline environments. We first examined the salinity tolerance of P. canaliculata using a total of 30 experimental juvenile snails exposed to eight salinity levels (from 0 to 14 psu in 2 psu steps). Daily survival of the snails was measured for each salinity treatment over 30 days. Based on salinity exposure test, influence of salinity on snail reproduction was investigated for a period of 30 days using 30 adult snails exposed to four salinity treatments (0, 2, 4 and 6 psu). Each salinity test replicated three times. Pomacea canaliculata could tolerate salinity levels ranging from 0 to 6 psu in which probability of survival was greater than 72% during a 30 days exposure. Lethal time leading to 50% mortality (LT50) of the snail declined from 71 days at 0 psu to 27 days at 6 psu. Pomacea canaliculata could ingest and reproduce normally at salinities ranging from 0 to 4 psu. Average mass daily gain, specific growth rate, and the hatching of egg clutches decreased significantly with elevated salinities. Results show a general threshold response of P. canaliculata to salinity. This freshwater snail falls into "2nd degree" euryhaline limnobionts tolerating salinities of 3–8‰. [ABSTRACT FROM AUTHOR]

Epilithic algal community structure and function are important indicators of stream ecosystem health and are sensitive to ambient environmental changes. In this study, we examined the impact of light and nutrients on epilithic algal community structure and function by an in situ nutrient addition and shaded canopy experiment in subtropical streams in China. Epilithic algae structure, dominated by diatoms, was significantly different with nutrient addition and light reduction. Nutrient addition increased the epilithic algae and diatom density, colonial life-forms, planktonic diatoms, and high-profile diatoms but decreased the low-profile diatoms. The shaded canopy increased the low-profile diatoms but decreased the adnate life-forms, planktonic diatoms, and high-profile diatoms. Epilithic metabolism, including gross primary production (GPP), net daily metabolism (NDM), and production/respiration (P/R) increased with nutrient addition, while respiration (R) only increased when the canopy was open with nutrient addition. Epilithic GPP had a significant positive correlation with diatom density (P < 0.01, R2 = 0.9425). Our results indicated that changes in epilithic algae structure due to changes in riparian canopy coverage and nutrients could affect epilithic algal community function. Quantifying the impacts of such drivers on community structure and function is vital to effective river management. [ABSTRACT FROM AUTHOR]

Extreme hydrological events can modify aquatic community structure resulting in significant changes in the ecosystem function. This study investigated the impacts of an extreme flood on the fish assemblage in the Gaobazhou reservoir, Yangtze River basin, which encountered devastating impacts of a severe flood in July 2016. The in situ effects of the severe flood on the fish assemblage were monitored by means of hydroacoustic surveys. Our study indicated that the flood had significant impacts on the fish assemblage in terms of fish density, biomass, structure, and distribution by modified hydrology. The fish density declined significantly (P < 0.05) from 3260 ind. ha−1 in the pre-flood period to 431 ind. ha−1 in the post-flood period, whilst the fish biomass increased from 237 to 526 kg ha−1 due to escapees from cage culture that resulted from the flooding, respectively. The ratio of fish density in reservoir bays to mainstream in the post-flood period is 16.5 as opposed to 2.4 in the pre-flood period. Hydrological changes and escapees from cage culture resulting from flood had significant impacts on the modification of the fish assemblage in the reservoir. [ABSTRACT FROM AUTHOR]

Fish-based index of biotic integrity (F-IBI) is widely used to assess river ecosystems. With survey data from the Yellow River fishery resources in the 1980s and 2008, fish composition and abundance, vertical distribution, trophic structure, reproductive guilds and tolerance in the river’s upstream, midstream, downstream, and estuary were examined, and F-IBI systems were established for each reach to assess river ecosystem health. Results showed that compared to the 1980s, the number of fish species in 2008 sharply declined in the midstream and downstream reaches, percentage of benthic fish species decreased in upstream and estuary, the number and percentage of omnivorous species decreased in all reaches, and percentage of tolerant fish species increased 15 times in upstream but decreased in midstream and downstream. The F-IBI scores in the four reaches in the 1980s were all higher than those in 2008 and decreased from upstream to estuary; the healthy conditions indicated by F-IBI scores in the 1980s were “good,” “fair,” “poor,” and “fair” from upstream to estuary and “degraded” to “poor” in all the reaches in 2008. This indicated that the river ecosystem has degraded from the 1980s to 2008. This was also shown by variations in water chemistry. [ABSTRACT FROM AUTHOR]

Spatial patterns and β-diversity of phytoplankton assemblages depend on the relative importance of species dispersal capacity and species-sorting. Variability in species composition, composed by differences in species richness (nestedness) and/or species replacement, may be caused by niche availability and environmental selection. A field survey was carried out in Tibetan plateau on 38 lakes. Tibetan plateau lakes, located at high elevation, are harsh ecosystems characterized by low temperatures, low available nutrients, high UV amount, and strong salinity gradients. Only well-adapted species can survive in these environments. We therefore hypothesized that environmental filtering was the main factor determining phytoplankton assemblage structure in these lakes, and that species nestedness largely contributed to β-diversity. Spatial analysis showed that both environmental variables and broad-scale spatial variables accounted for the variation of phytoplankton assemblages. In particular, phytoplankton was mainly shaped by spatially structured environmental heterogeneity, which resulted in low α-diversity and high β-diversity. In contrast to our assumption, species turnover contributed to the majority of β-diversity of the studied assemblages. Local environments selected species with the corresponding stress-tolerant traits. Within the narrow range of available niches, environmental filtering of phytoplankton traits induced species’ replacement along environmental gradients. [ABSTRACT FROM AUTHOR]

In this study, a large dataset for the three largest freshwater lakes (Poyang, Dongting, and Taihu) of the Yangtze River floodplain in China was analyzed to quantitatively compare the ecological structure and function of the Yangtze-connected (Poyang and Dongting) and Yangtze-isolated (Taihu) lakes on a broad scale. Discriminant analyses were performed to determine and correlate the composite gradient of physical-chemical variables that separated the six study regions, East Poyang Lake (LPY), Open LPY, North LPY, Dongting, Meiliang Bay, and Taihu center, with variables including suspended solids (SS), Secchi depth (SD), water temperature (WT), chemical oxygen demand (COD), flow velocity, and total nitrogen-to-total phosphorous (TN:TP) molar ratio. A regression analysis showed that the interactions between the SS and TP concentrations affected the phytoplankton biomass in the lentic (Meiliang Bay and East LPY) and partly lotic (Open LPY and Dongting) zones. The trophic level index (TLI)-phytoplankton, SS-phytoplankton, and TP-phytoplankton relationships revealed that hydrological (water velocity) and physical (underwater light penetration) conditions had the greatest effect on the algal biomass in the eutrophic Yangtze-connected lakes, whereas phytoplankton growth was mainly related to nutrients in the eutrophic Yangtze-isolated lake. [ABSTRACT FROM AUTHOR]

Emerging theory suggests that biotic communities in floodplain wetlands should change longitudinally along a river's length and be affected by lateral connectivity of floodplain habitats with main river channels. However, useful invertebrate indicators of floodplain condition remain poorly developed. Snails as a group possess several attributes that should make them useful as potential environmental indicators. In this study, we sampled snail assemblages in 12 floodplain wetlands along Wusuli River (headwater, mid, and downstream reaches) in Northeastern China's Sanjiang Plain. In addition, at 10 sites, comparisons between river-connected and levee-isolated wetlands were performed. Results demonstrated that snail assemblages were concurrently being impacted by river reach, and whether the wetlands were isolated from the river, or not. Using multivariate analyses, the studied wetlands were divided into three major groups based on snail assemblages: downstream, mid, and headwater reaches. Seven snail species were significant indicators of these wetland groups. Because snail assemblages vary strongly both longitudinally along and laterally across floodplain habitats of Northeastern China, management of floodplains should recognize that landscape position plays an important role in local habitat ecologies, and that efforts to limit hydrologic connectivity across floodplains will have important consequences for resident biota. [ABSTRACT FROM AUTHOR]

China's five largest freshwater lakes (Poyang, Dongting, Taihu, Hongze, and Chaohu) are all located in lowland regions and differ greatly in lake morphology, hydrology, and water chemistry. However, basic knowledge of diversity patterns and factors driving macroinvertebrate community structure is lacking. We analyzed the composition and diversity of benthic macroinvertebrates and evaluated the roles of environmental factors and dispersal processes in determining beta diversity at both the lake and regional scales. The two Yangtze-connected lakes (i.e., Lakes Poyang and Dongting) were highest in taxonomic diversity. Differences in taxonomic composition were evident among the five lakes, with the two Yangtze-connected lakes dominated by bivalves and/or gastropods, while Lake Taihu showed great changes in taxonomic composition among sites in accordance with its high habitat heterogeneity. Lake Hongze was dominated by polychaetes, crustaceans, and bivalves. The eutrophic-hypertrophic Lake Chaohu was exclusively dominated by chironomids and oligochaetes. At the lake scale, total γ-diversity was mainly attributed to β -diversity (among sites) ranging from 57.9 to 87.6%. The total γ-diversity at the regional scale was primarily related to higher β-diversity, with β and β (among lakes) accounting for 30.4 and 58.8% of total taxa richness, respectively. Environmental conditions appear to be important in structuring benthic macroinvertebrate communities at both the lake and regional scale. Dispersal does not appear to affect distribution of macroinvertebrates at the lake scale. [ABSTRACT FROM AUTHOR]

Landscape pattern plays an important role in structuring of larval fish assemblages in large river basins. The lower reach of the Yangtze River includes the river section from the mouth of Poyang Lake, the largest freshwater lake in China, downward to the estuary. We hypothesized that river-lake connectivity at the upstream portion and tidal intrusion at the downstream portion are significant drivers of larval fish assemblages. Larval fish were collected monthly from April 2012 through September 2013 in three locations at Anqing (AQ), Nanjing (NJ), and Jingjiang (JJ). Fifty-six taxa of larval fish were identified with 52 of them determined of species. Larval fish were highly abundant from April through August; the number of species and the abundance were much higher at AQ than at NJ and JJ; the bloom of larval fish at JJ tended to be later than at NJ and AQ. We suggest that the larger number of species and higher abundance of larval fish at AQ reflect the effects of the connectivity of Poyang Lake with the river upstream of AQ, and the delayed bloom of larval fish and the occurrence of estuarine species at JJ reflect the influences of tidal intrusion from the estuary. [ABSTRACT FROM AUTHOR]

Both Dabry's sturgeon ( Acipenser dabryanus) and Chinese sturgeon ( A. sinensis) are rare fish and listed as first class protected animals in China. Nowadays, an artificial release program has been established as a main way to maintain and restore their wild populations. Unintentional interspecific hybridization of these two sturgeons might occur because of their close relationship. To ensure the purity of germplasm, Dabry's sturgeon and Chinese sturgeon must be identified before releasing. Owing to their highly similar morphological characteristics, it is difficult to discriminate the two sturgeon species based on morphology in their larval and juvenile stages. Moreover, it is almost impossible to discriminate their hybrids based on morphology. Therefore, we established a new molecular approach to discriminate Dabry's sturgeon and Chinese sturgeon based on mitochondrial DNA barcode and six nuclear markers (three nuclear genes (TYR, GHR, and RAG2) and three SNP markers (SNP21564, SNP28822, and SNP12974) in this study. These two sturgeons were explicitly distinguished from other sturgeon species using the DNA barcode and three nuclear genes. Further, the two species were accurately discriminated using the three SNP markers. We concluded through blind laboratory trials involving 95 individuals that our method is 100% reliable in distinguishing between the two species. [ABSTRACT FROM AUTHOR]

Leucocytherella sinensis, a ubiquitous and the most abundant ostracod endemic to the Tibetan Plateau, can account for >98% of the ostracod association. These low-diversity associations are hard to interpret using community palaeoecology alone, but environmentally driven phenotypic variation may provide clues to palaeoenvironmental factors. L. sinensis displays several morphological forms, characterised by different tubercle formation on their valves. These morphological forms were described as diverse species. We present a taxonomical revision and a first description of the soft parts of L. sinensis. We also redescribe the genus and confirm its assignment to the subfamily Limnocytherinae Klie, 1938. Analysis of L. sinensis associations from surface sediments of 12 Tibetan lakes shows a connection between tubercle formation and specific conductivity (SC) of the ambient water with lower tubercle number at higher salinity. Tubercles are less common in low SC populations and highest within the beta-oligohaline range. However, high Ca concentrations suggest a combined effect of salinity and Ca ion concentration on tubercle formation. The phenomenon of tubercle formation can be used to trace salinity changes recorded by fossil L. sinensis valves from Tibetan Holocene lake sediments. [ABSTRACT FROM AUTHOR]

Vegetation communities in floodplain lakes are adapted to natural water regimes. Construction of sluices or dams between rivers and their floodplain lakes will inevitably lead to great changes in plant communities. In order to evaluate the effects of water level fluctuations (WLFs) on lakeshore vegetation in floodplain lakes of the Yangtze River, a field investigation was conducted in two river-disconnected lakes (Wuchang Lake and Shengjin Lake) and one river-connected lake (Shimen Lake). The results showed that plant species richness was highest in the disconnected Shengjin Lake with intermediate amplitude of WLFs, and lowest in the connected Shimen Lake. Species composition differed among the three lakes and the two disconnected lakes with more similar WLFs exhibiting the greatest similarity. Six plant communities were classified using TWINSPAN. Multivariate analyses showed that the amplitude of WLFs was the most important factor in determining the distribution of lakeshore plants, followed by relative elevation and duration of submergence. Our results provide an eco-hydrological basis for plant restoration in the Yangtze floodplain lakes. We suggest that fluctuating amplitude should be increased in lakes with small WLFs, and small habitats with various hydrological regimes should be created in lakes with large WLFs. [ABSTRACT FROM AUTHOR]

It is widely accepted that algal blooms are a result of eutrophication processes. Water temperature, total phosphorus and total nitrogen are the main environmental parameters impacting Chlorophyll- a (Chl a) in aquatic ecosystems. To elucidate the variability of these parameters in Lake Taihu, China, we analyzed their multi-temporal characteristics using wavelet power spectrum. We evaluated the non-stationary statistical association between algal biomass (as Chl a) and the selected environmental parameters using wavelet coherence and wavelet phase difference. Our results indicate that these variables presented periodic oscillations in frequency domain and localization along time axis. Significant 3-4 month and annual bands are identified in both algal and environmental parameters variations. Chl a responded quickly to variation in water temperature but showed a delayed response to variation in total nitrogen; it also showed a delayed response to variation in total phosphorus during 1995-1997, but responded more quickly in recent years. The intensity of oscillation power in frequency domain resulted in non-stationary statistical association, and the phase difference in time domain resulted in time-lag correlations between Chl a and the selected environmental indices. These results contribute to elucidate the nonlinear eutrophication dynamic process and provide information for algal bloom prediction and lake management. [ABSTRACT FROM AUTHOR]

Population age structure, preservation, and carapace abundance of the valve remains of Limnocythere inopinata in 88 surface-sediment samples from Lakes Daihai, Dali, and Hulun were examined to better understand taphonomy of limnic ostracods. The spatial changes in population structure of L. inopinata match the within-lake hydraulic gradients, with the older instars preferentially deposited in the littoral zone while the younger instars being more abundant in deeper waters. We propose that molt and mortem remains of ostracods, especially those of the small juveniles, experience downslope transport. The magnitude of transport in a lake is controlled by wind-driven hydrodynamics. There is no chemical dissolution of ostracod valves in these alkaline lakes, and degradation is mainly represented by physical breakage. The preservation of L. inopinata is related to sedimentation rate and hydraulic stability, and the spatial pattern of preservation varies between lakes. Spatial and seasonal changes in sedimentation rate and hydraulic condition, and the ostracod life cycle may have contributed to this complexity. Adult and A-7 carapaces are the most frequent among the instars. We suggest that the preferential preservation of juvenile carapaces is either related to high mortality rate or to the good preservation in deep waters. [ABSTRACT FROM AUTHOR]

Spartina alterniflora Losiel. is a highly invasive species found on the Chinese coast. To characterize the evolutionary mechanisms underlying the success of S. alterniflora in China, we examined the distribution and structure of genetic variation among three native populations at their source locations and five non-native populations in China, at both the chloroplast and nuclear microsatellite loci. Both cpDNA and microsatellite data revealed comparable genetic diversity and population differentiation between the native and introduced regions, which is consistent with the deliberate historical planting of heterogeneous founding groups in China. Bayesian clustering analysis showed that the best two clusters in the introduced region correspond to populations from the Atlantic coast and Gulf coast, respectively, instead of the three ecotypes proposed by a previous study. Investigating genetic composition of individuals suggested that most of the non-native plants might be of Atlantic origin, while some individuals in the Hong Kong population could be genetic admixtures of Atlantic and Gulf origin. This study indicated varied genetic components among populations in China, which imply different sources for the present Chinese populations. [ABSTRACT FROM AUTHOR]

Environmental controls on cladoceran community structure in lake ecosystems are complex and may involve many environmental parameters including trophic state and fish populations. In Lake Erhai, a plateau lake located in southwest China, it was hypothesized that a combination of lake eutrophication and planktivorous fish introduction would increase the abundance of cladoceran, while also decreasing cladoceran size. To test this hypothesis, we examined temporal changes in cladoceran microfossils in the sediments of Lake Erhai over the past century. The influence of changing macrophyte coverage within the littoral region of the lake was also considered. Results demonstrated that cladoceran abundance (measured as flux of cladoceran fossils in the sediments) increased markedly accompanying eutrophication of the lake. In addition, there was a shift in the dominant cladoceran species from those species that prefer oligotrophic conditions to those that prefer mesotrophic and eutrophic conditions. A reduction in the ephippium length of Daphnia spp. was observed and attributed to the introduction of the planktivorous fish Neosalanx taihuensis. Our findings indicated that eutrophication and fish introduction were the main controls affecting cladoceran community structure during the recent decades, and predation by planktivorous fish had an important impact on Daphnia body size. [ABSTRACT FROM AUTHOR]

Stocking of filter-feeding fish is a common tool used in Chinese reservoirs to increase fish production because of low natural recruitment. Whether such stocking has important negative effects on zooplankton with cascading effects on phytoplankton is debated. We compared the zooplankton communities in fourteen reservoirs with different nutrient concentrations and fish densities. Both chlorophyll a (Chla) and fish catch were positively related with total phosphorus (TP), whereas zooplankton biomass did not show a similar relationship with TP. Zooplankton seemed to be influenced by fish as high fish catches coincided with a low proportion of calanoids of the total copepod biomass, a high proportion of rotifers of the total zooplankton biomass, a low zooplankton:phytoplankton biomass ratio, and the absence of Daphnia irrespective of TP concentration. Both zooplankton biomass and most of the zooplankton:phytoplankton biomass ratios were among the lowest reported in the literature for the nutrient range studied. Furthermore, the Chla:TP ratio was higher than what is typically observed in temperate lakes. We conclude that top-down control of zooplankton is of key importance in reservoirs in South China where frequent stocking of filter-feeding fish seems to contribute to poor water quality in the form of higher algal biomass and reduced clarity. [ABSTRACT FROM AUTHOR]

Environmental flow releases provide the water regime required to maintain the aquatic ecosystem health, which are subject to intensive human disturbance. We used decades of data to determine whether the long-term use of flow releases had successfully restored China's Baiyangdian Lake ecosystem. We used fuzzy-logic inference and field data to compare the water level regime, water quality, and ecological variables before and after the releases. Critical components of the water level regime, including the annual mean, the 7-day low, and the 30-day low and high water levels, differed significantly before and after the releases. The releases slightly improved water quality compared with the pre-1997 level, except in 2003. The reed area and fish yield have been greatly increased by these flows since 1997, but changes in the reed yield and fish species were not significant. We discuss the advantages and drawbacks of the current environmental flow releases for Baiyangdian Lake, and propose that the release patterns have adversely affected the lake's natural level regime from an ecological perspective. Therefore, we suggest that accounting for recent research on environmental flows, including the implementation of adaptive management, will be required to implement more sustainable and ecologically effective releases of environmental flows. [ABSTRACT FROM AUTHOR]

Pachychilid snails are common and widespread in tropical Asian streams, and given their abundance, these heavy-shelled prosobranchs may serve as a 'trophic dead-end' preventing energy transfer to higher trophic levels. Sulcospira hainanensis (Bröt, 1872) is an abundant secondary consumer in Hong Kong streams, and tends to have higher standing biomass in less shaded sites. We predicted that S. hainanensis would be more productive in unshaded streams, where snails have a higher assimilation of more nutritious algal carbon. The production and population dynamics of S. hainanensis were studied along a gradient of shading in four Hong Kong streams. The increment-summation method was considered to most realistically represent snail production, which ranged from 1,612.8 to 6,123.9 mg ash-free dry mass m year; these estimates were among the upper range of values reported for stream prosobranchs. Production, turnover, and growth were higher in unshaded streams, where the combined effects of higher light input and nutrient concentrations likely enhanced the supply of algal food. Despite high standing biomass (26% of total benthic fauna), S. hainanensis had a relatively low (~16%) contribution to total production in one site, suggesting that it is not a major trophic dead-end in the food webs of tropical Hong Kong streams. [ABSTRACT FROM AUTHOR]

While the effects of lake restoration by fish manipulation are well-studied in the temperate zone, comparatively little information is available on this issue from tropical lakes. It may be expected that fish removal leads to faster recovery of the fish stock here than in temperate lakes due to more frequent and earlier reproduction, which may, in turn, delay positive effects of the restoration. We studied the community composition, feeding type and abundance of fish in three basins of a tropical shallow lake: one unrestored basin (UR) and two basins restored by fish manipulation and transplantation of submerged macrophytes. While omni-benthivorous fish dominated the biomass in the restored basins 3 and 5 years after restoration, planktivores were most abundant in the UR, although total fish biomass remained similar. One-way analyses of similarities based on fish species presence/absence, abundance and biomass data revealed significant differences in fish community composition among the restored basins and UR, and redundancy analyses further indicated that submerged macrophytes were a key driver behind this difference. Our results indicate that active implantation of submerged macrophytes to stabilise the fish community is a tool to consider when planning lake restoration by biomanipulation in the tropics. [ABSTRACT FROM AUTHOR]

In order to determine the effect of wind-induced waves (influenced by wind velocity and direction) on the dynamics of optical properties in shallow lakes, we determined the short-term variability of the inherent optical properties (IOPs) in Meiliang Bay, Lake Taihu, China, by examining high-frequency data collected between 8 and 21 September 2010 from meteorology and optical sensors. The absorption and beam attenuation coefficients under strong winds were significantly higher than those under weak and moderate winds ( t test, P < 0.001). Significant correlations were found between absorption, scattering, beam attenuation, and wind speed, showing that the hydrodynamic process was an important factor that influenced the instantaneous IOPs of the water. However, the different wind directions have a different effect degree on the IOPs. Western wind is the most important driven wind direction of this site. In addition, significant correlations were found between b(440), c(440), b(677), c(677), b(440), and turbidity under each wind direction ( P < 0.001). Exponential and hyperbolic exponent models of the absorption and beam attenuation coefficients were fitted, and linear models between a(677), c(677), and turbidity were developed. Thus, in shallow lakes such as Lake Taihu, using real-time high-frequency monitoring of the turbidity to deduce the water IOPs could be an efficient and practical approach. Our study will be helpful in monitoring the IOPs and in improving the accuracy of bio-optical models to estimate water quality parameters in Lake Taihu. [ABSTRACT FROM AUTHOR]

We present radiometric data from nine lakes across the Tibetan Plateau, and compare their reliability in relation to recent research. Unsupported Pb profiles show, except for one particular lake, non-exponential decline of Pb activity with sediment depth. Stratigraphic dates based on global atmospheric nuclear weapons maximum fallout of Cs (1963) support the use of the constant rate of Pb supply (CRS) model in four of the dated cores. The discrepancy in the others is likely due to recent increased input of catchment-derived Pb. Pb dates in this study suggest that post depositional diffusion of Cs activity has been significant. The practice of assigning early 1950s dates (start of global atmospheric thermonuclear testing) to lake sediment sequences on the Tibetan Plateau should be used with caution. Cs profiles from Tibetan lake sediment cores and their geographical distribution suggest that Cs derived from the 1986 Chernobyl accident or atmospheric testing in China was not sufficient to form a significant peak effective for dating. [ABSTRACT FROM AUTHOR]

The ecosystem of the highly eutrophic Lake Taihu (China) is seriously affected by recurrent cyanobacterial blooms, but little is known about the contribution made by cyanobacteria to the food web. In this study, we investigated the fate of detritus of the cyanobacterium Microcystis in the food web of Lake Taihu through a 19-day mesocosm experiment using stable-isotopic tracers of carbon (C) and nitrogen (N). C- and N-labeled Microcystis detritus was added to the mesocosm tanks and tracked through different elements of the food web. We found clear enrichment with both C and N in some zooplankton species, including Daphnia, Diaphanosoma, and Sinocalanus, which suggests that these zooplankters can utilize cyanobacterial detritus as a food source. Benthic animals, chironomid larvae and Limnodrilus, also showed pronounced increases in C and N, but the isotope increase was relatively smaller in the gastropods, Radix sp. and Bellamya sp., implying that they either exploited this food source differently or responded slower than the zooplankton, which apparently grew faster than the snails. Our study suggests that cyanobacterial detritus, originating almost wholly from the bloom-forming Microcystis, is an important food source for both planktonic and benthic food webs in eutrophic lakes such as Lake Taihu. [ABSTRACT FROM AUTHOR]

Lakes are important in the global and regional carbon cycle, and lake sediments potentially store substantial quantities of organic carbon. The middle and lower reaches of the Yangtze River basin (MLYB) are some of the largest agricultural areas in China with an extremely high density of lakes and rivers. The lakes in the region have undergone dramatic changes over the past several decades. In this study, six cores from five lakes (the macrophyte-dominated: Shijiuhu Lake and Honghu Lake; the algae-dominated: Chaohu Lake, Taihu Lake, and Nanyihu Lake) in the MLYB were collected from 2002 A.D. to 2008 A.D. Mass accumulation rates (MARs) of sediment derived from Pb and Cs along with total organic carbon content (TOC) were used to determine organic carbon accumulation rates (OC ARs) over the last 100 years. The TOC in the five lakes exhibited a significant increase since the mid or late 20th century, which was consistent with the increase in the lake water trophic status due to nutrient input. The average organic carbon accumulation rates for the Taihu Lake, Nanyihu Lake, Chaohu Lake, Shijiuhu Lake, and Honghu Lake were calculated to be 16.6, 28.9, 9.8, 25.4, and 113.2 g C m year, respectively, over the past 100 years. Based on the average OC AR of 32.1 g C m year from the five lakes, carbon burial in lake sediments may be as much as 6.8 × 10 g C in the MLYB over the past 100 years. [ABSTRACT FROM AUTHOR]

A full understanding of life history characteristics of invasive species is a fundamental prerequisite for the development of management strategies. Two introduced goby species ( Rhinogobius cliffordpopei and Rhinogobius giurinus) have established highly abundant populations in Lake Erhai (China). In the present study, we examined the reproductive biology of these two species with the aim of improving the efficiency of management strategy. The results indicated that R. cliffordpopei spawned from February to June, whereas R. giurinus spawned from April to August. Rhinogobius cliffordpopei showed higher gonado-somatic indices and had larger eggs than R. giurinus. The adult sex ratio of R. cliffordpopei was female skewed, but that of R. giurinus was equal. Rhinogobius cliffordpopei showed a male-skewed sexual size dimorphism, whereas the body size of R. giurinus varied only slightly between males and females. The different reproductive traits appear as a crucial biologic aspect for developing control programs. Specifically, control measures should be implemented and/or intensified from September to February for R. cliffordpopei and from January to April for R. giurinus. The body size of the smaller R. cliffordpopei females is the determinant for minimal mesh size of the nets used in physical removals of R. cliffordpopei. [ABSTRACT FROM AUTHOR]

Seasonal water-level changes in floodplain lakes can induce variations in primary and secondary production, thus affecting trophic interactions. In this study, we tested the latter by studying size- and temporal hydrology-related shifts in the diet of shortjaw tapertail anchovy Coilia brachygnathus (Actinopterygii, Engraulidae) from Lake Poyang. During the wet season, δC values ranged from −28.2‰ for small anchovies to −24.6‰ for larger individuals, but δN ranged from 18.9‰ for smaller fish to 12.4‰ for larger fish. Significant C-enrichment and N-depletion occurred with increasing size, revealing that different carbon sources were used as the fish grew. Given the high hydrologic fluctuation levels, significant differences in δC values were observed among larger anchovies between seasons, indicating a temporal dietary shift. Anchovies fed primarily on shrimp and fish during the low-water season despite the predominance of zooplankton during the two seasons studied, which indicated increased piscivorous reliance. C. brachygnathus exhibited higher δN values during the wet season because the food items were N-enriched. Human waste brought by floods could be another possible interpretation. Considering C. brachygnathus is an important link between plankton production and higher piscivorous trophic levels, changes in the species are expected to affect the functioning of lake food webs along the trophic pathway. [ABSTRACT FROM AUTHOR]

We studied the effects of flow reduction on epibenthic algal assemblages by comparing up- and down-stream reaches of ten Hong Kong streams subject to different degrees of water abstraction during 2007-2008. Downstream discharge declined by 71 and 54% during the wet and dry seasons, respectively. Algal responses varied seasonally and according to morphological guild and reflecting reductions in discharge and current velocity, or changes in total nitrogen and phosphate, or their combined effects. Significant inter-reach assemblage differences were observed during the both seasons, but wet-season assemblage structure was not directly influenced by any flow-related variable. During the dry season, scouring-tolerant prostrate/adnate diatoms (especially Achnanthes, Cocconeis) were relatively abundant upstream, whereas intolerant stalked ( Eunotia, Gomphonema) and mobile diatoms were more numerous downstream. Both low- and high-profile (erect diatoms, Chamaesiphon, Calothrix) guilds were sensitive to changes in nutrients. Low-flow conditions downstream, surprisingly, enhanced algal diversity, and richness. Based on the linear response of Cocconeis (mainly C. placentula) to discharge reduction, we recommend that >65% of dry-season discharge should be maintained in downstream reaches in order to sustain near-natural algal assemblages; 32% of discharge is required to avoid substantial alterations in assemblage structure. [ABSTRACT FROM AUTHOR]