Survival Of Aquatic Organisms Research Articles

Impacts of hydrodynamic disturbance on black blooms: An in-situ study in Lake Taihu

The occurrence of black blooms, a kind of black water phenomenon, mostly formed by the decomposition of cyanobacterial blooms poses a threat to both drinking water supplies and the survival of aquatic organisms. Meteorological and hydrological conditions play a crucial role in their formation, while the specific impact of hydrodynamic disturbances on the black blooms remains unclear. The aim of this study is to investigate in depth the impact of hydrodynamic disturbances on the formation and development of black blooms, as well as their effects on the microbiota in surface sediments during the process. During the occurrence of black blooms in Lake Taihu, in-situ water and surface sediment samples were collected. By combining studies of the changes in water quality and microbial communities, the potential driving mechanisms of hydrodynamic disturbances were analyzed. The results indicate that during the outbreak stage (MS), hydrodynamic disturbances drove the release of anaerobic byproducts in sediments (NH4+-N ≥ 0.5 mg/L, TN ≥ 2.03 mg/L, TP ≥ 0.15 mg/L), and varying levels of hydrodynamic disturbance led to significant differences in microbial communities (ANOSIM, R = 0.477, p < 0.05). This influenced the abundance of microorganisms with carbon and sulfur cycling functions in sediments, where stronger hydrodynamics promoted the coupling of carbon mineralization and fermentation processes, while weaker hydrodynamic disturbances facilitated the coupling of carbon mineralization and sulfate reduction processes. Additionally, hydrodynamic disturbances influenced the potential functions of sulfate-reducing bacteria (SRB) in sediments, altering the interactions between SRB and other microorganisms. This study, for the first time, investigated the impact of hydrodynamics on the formation of black blooms from the perspective of their interaction with microorganisms. These findings broaden our understanding of the significance of hydrodynamic disturbances during black bloom occurrences and contribute to our ability to predict the formation of black blooms through modeling.

Effect of light intensity on the survival of European spiny lobster (Palinurus elephas) larvae reared in aquaculture system

Light plays a crucial role in the growth, development, and survival of aquatic organisms. To evaluate the survival of European spiny lobster (Palinurus elephas) larvae in relation to different light intensities (26, 359, and 910 lux, equivalent to 0.35, 4.74, and 12.29 μmol·m−2·s−1, respectively), this study monitored the survival rates of reared spiny lobster from the early instar phyllosoma stages to their metamorphosis into the puerulus stage (111 days after hatching) at the three light intensities. The newly hatched larvae were cultured in 65-L Kreisel tanks with 200 individuals each (three replicates per treatment, i.e., light intensity). Phyllosoma stages I to III larvae showed no significant differences in survival rates under different light intensities. However, light intensity did have a significant impact on the survival rates of phyllosoma stages IV and V as well as the metamorphosis of phyllosoma VI into puerulus. The highest survival rates were observed under high and medium light intensity conditions. At the end of the experiment, the highest mean survival rate for stage VI, the metamorphosis into the puerulus stage, was 42.0 ± 2.52 % under high light intensity. These survival rates for reared pueruli were 84 times higher than those achieved in previous studies. The present study results show promise for the successful implementation of commercial scale rearing protocols for European spiny lobster and have implications for the design of crustacean larvae culture systems.

Impacts of environmental flow regulation on survival of aquatic organisms: a case study of Cyprinus Carpio in Baiyangdian, China.

Decreasing water volume and increasing pollutants in wetlands pose challenges to aquatic life. While environmental flow regulation is widely applied to enhance aquatic habitats, its effectiveness needs to be evaluated. In this study, a hydrodynamic-water quality model was used to simulate the fields of flow, temperature, and pollutants. The Ecological Niche Modeling at the MetaLand EcologyLab (ENMTML) was utilized to evaluate the area of suitable habitats for aquatic organisms under both environmental flow regulation and no environmental flow regulation conditions. The typical Baiyangdian Wetland in northern China was taken as the study area, and the important economic fish, Cyprinus carpio, served as the indicator of aquatic species. The effectiveness of environmental flow regulation was evaluated from December 1, 2017, to June 30, 2018. The results indicated that the variables of water depth, dissolved oxygen (DO), ammonia nitrogen (NH4+-N) and Chlorophyll a (Chla) were the major environmental factors determining the variability of the suitable habitat area for Cyprinus carpio. The environmental flow regulation capacity of the Baiyangdian Wetland was 2.6 [Formula: see text] 108m3, which produced a suitable habitat area of 135.538km2 at the end of the water supply period. Compared with the no environmental flow regulation condition, the highly and moderately suitable habitat areas for Cyprinus carpio were enlarged by 56.30km2 and 34.11km2, respectively. The outcome provides not only a basic reference for wetland management, but also a scientific perspective for understanding the impact of environmental flow regulation on aquatic organisms. The proposed method demonstrates the important potential of evaluating the effectiveness of environmental flow regulation on aquatic organisms in wetlands.

Fault diagnosis method of dissolved oxygen sensor electrolyte loss based on impedance measurement

Dissolved oxygen affects the growth and survival of aquatic organisms and considers as an important indicator of aquaculture water quality. Moreover, the electrochemical dissolved oxygen sensor may become faulty due to flow shock or damage by organisms which destroys the dissolved oxygen permeable membrane and results in loss of electrolytes. In this paper, a method was developed for detecting electrolyte loss faults in polarographic dissolved oxygen sensors by directly measuring impedance of sensing electrodes without additional sensing elements or modifying the sensor. First, the factors interfering electrolyte concentration-impedance relationship and the requirement for temperature compensation was determined. Secondly, a fault diagnosis of internal electrolyte loss was achieved by using the difference between the theoretically calculated value and the impedance measurement value in combination with the electrode reaction law. Finally, the impedance detection method was demonstrated using artificially simulated faults. The results showed that the developed method had accurate tracking of electrolyte consumption with a Pearson coefficient of 0.987. Three different levels of breakage failures were simulated and detected as 4.48 %, 21.07 % and 73.47 %, respectively. The mean absolute error of the normal state was about 1.67, which increased to 16.3 after a period of failure. The developed method meets the requirements of embedded development because it uses a simple fault detection device and easy data processing using a simple microprocessor. Furthermore, the diagnosis result has been demonstrated as an indicator of membrane health and breakage conditions of dissolved oxygen sensors.

Effects of stocking density on juvenile Amphioctopus fangsiao (Mollusca: Cephalopodasca: Cephalopoda): Survival, growth, behavior, stress tolerance and biochemical response

Stocking density determines the welfare, growth performance, and even survival of aquatic organisms in aquaculture. However, how stocking density affects cephalopods are still unclear. Here we selected Amphioctopus fangsiao, a promising cephalopod for mariculture, to examine the effect of stocking density on survival, growth, physiology and behavior. Juvenile A. fangsiao (≈ two months post-hatch, 2.41 g ± 0.03) were reared for 21 days under different stocking density groups: 30, 45, 60 and 75 individual/m2 (ind./m2) (G1, G2, G3 and G4, respectively). Subsequently, the growth performance, aggressive acts, survival rate, stress response, oxidative stress and glucolipid metabolism were analyzed. This study showed that the high stocking density had a negative impact on growth performance. A. fangsiao reared in G3 and G4 had a significantly lower final body weight, weight gain and specific growth rate than those reared in G1 and G2 (p < .05), and hepatosomatic index in different treatment groups have a similar trend of difference (p < .05). Increased stocking density also caused more fights of A. fangsiao, resulting in a high mortality rate for farmed individuals. The individual numbers of released ink after touch and the recovery time of the breathing rate after air emersion showed that the low stocking density lowered the basal stress level and reduced the recovery time after acute stress of juvenile A. fangsiao. In addition, this study demonstrated that high stocking density has caused oxidative stress and lipid disturbance of A. fangsiao. There were significant differences in reactive oxygen species (ROS), lipid peroxidation's level (MDA content), the activities of superoxide dismutase (SOD) and catalase (CAT), pyruvic acid level (Pyr), total cholesterol level (T-CHO) and triglyceride (TG) between the highest density group (G4) and the lowest density group (G1). Overall, high stocking density (G3 and G4) had a negative effect on reared A. fangsiao. However, there were no significant differences between G1 and G2. Therefore, to improve the welfare of reared A. fangsiao and maximize the economic benefits for producers, juveniles are recommended to rear at a medium density (about 45 ind./m2).

Fe-dependent cellular alterations of oxidative balance in aquatic organisms. Could be ferroptosis involved?

The purpose of this review is to briefly summarize the central role of iron (Fe) in terms of cellular alterations of the oxidative/protective balance with special emphasis on its possible involvement in ferroptosis-dependent disruption in aquatic organisms. In ferroptotic cells or tissues, the intracellular Fe level increases; meanwhile the treatment with Fe chelators limits ferroptosis. Eukaryotic algae can assimilate Fe from the environment through several mechanisms, and aquatic animals incorporate dissolved Fe and Fe bound to both inorganic particles and organic matter. The central role of lipid peroxidation mediating ferroptosis was demonstrated in some algae where both low and high Fe concentrations could induce oxidative stress and programmed cell death. Aquatic animals have high levels of polyunsaturated fatty acids and numerous studies have analyzed Fe effects on the lipidic fraction which could be related to ferroptosis. The ferroptosis reaction can be regulated through the antioxidant defense system, in combination with the protein degradation structure, metabolism, and gene transcription. Early depletion of non-enzymatic antioxidants like reduced glutathione (GSH) in animals, and the reduction of both GSH and ascorbate in photosynthetic organisms, are characteristic features of ferroptosis. Therefore, ferroptosis can be prevented if Fe chelators, certain antioxidants, and specifically regulating genes are activated. Thus, the global scenario for the Fe role as a toxic component in biological systems seems to be even more complicated than it was previously understood. Much more research on this subject is needed to improve the life span and survival of aquatic organisms after exposure to natural and anthropogenic adverse conditions.

Integrative proteomics and metabolomics reveal the stress response of semicarbazide in the sea cucumber Apostichopus japonicus

Semicarbazide (SMC), also known as carbamoyl hydrazide, is a key intermediate for the organic synthesis of drugs, pesticides, and a panoply of other applications. It is also regarded as a landmark metabolite of nitrofurazone, a banned veterinary drug. SMC produced in different ways will eventually enter the ocean and become an emerging marine pollutant, affecting the physiological metabolism, behavioral activities, and even survival of aquatic organisms. Sea cucumbers are sediment-feeding organisms, and their risk of exposure to pollutants has attracted increasing attention. In this study, an integrated proteomic and metabolomic approach was used to investigate the responses of Apostichopus japonicus treated with SMC (3.72 g/L) for 72 h. After SMC treatment, the proteins and metabolites of A. japonicus intestine changed significantly. The results showed that 342 differentially expressed proteins were identified, of which 174 were upregulated, 168 were downregulated, and 74 differentially expressed metabolites, of which 62 were upregulated and 12 were downregulated. These differential proteins and metabolites were primarily involved in energy metabolism, lipid metabolism, signal transduction, immune regulation, autophagy, and apoptosis. On the basis of a combination of proteomic and metabolomic data, a hypothetical network of proteins, metabolites, and pathways in sea cucumbers was also described; the resulting network indicated several significant biological activities in response to SMC. This work offers a thorough analysis of the intricate mechanisms by which sea cucumbers respond to SMC stress and indicates numerous possible indicators for further research on creatures exposed to SMC. Further, our results provide scientific guidance for pollution control of Apostichopus japonicus culture to ensure healthy breeding.

An enigma: A meta-analysis reveals the effect of ubiquitous microplastics on different taxa in aquatic systems

Microplastics are ubiquitous in aquatic ecosystems globally, with tropical freshwater systems underrepresented in the literature. The ubiquity of microplastics may affect the feeding, growth, reproduction, and survival of organisms in aquatic systems; however, the data on the potential effects of microplastics on aquatic organisms is tentative. In the current study, I conducted a meta-analysis using published data to examine the impacts of microplastic exposure on functional traits (i.e., feeding, growth, reproduction, survival) of fish and aquatic invertebrates. The data revealed that while there were within-taxa negative effects on traits such as reproduction and growth some effect sizes were low, suggesting that the exposure to microplastics may vary across taxa. Globally, negative effects on growth, reproduction, and even survival were evident in some taxa (e.g., bivalves, crustaceans). Considering feeding habits, negative effects of microplastic were more pronounced in bacterivores, omnivores, predators, and filter feeders compared to shredders. In tropical freshwater systems, microplastics had no significant effects on the feeding, growth, reproduction, and survival of aquatic organisms. It is worth noting that organisms that are passive feeders (e.g., bivalves) may be particularly susceptible to microplastic pollution, which in turn may have long-lasting effects on the stability of lacustrine and lotic food webs. Because microplastics may impart more chronic effects than acute effects, future works must include understudied regions of the world (e.g., freshwater systems) and must emphasize the subtle role that microplastics may play on the physiology and behavior of organisms in the long term.

An environmental flow method applied in small and medium-sized mountainous rivers

In small and medium-sized mountainous rivers, there are usually hydropower stations in upper reaches as well as widened and heightened river sections in downstream reaches that are close to settlements. The environmental flow (EF) ensures river connectivity and the survival of aquatic organisms. The Tennant and wetted perimeter methods were used to calculate the minimum EF, and the R2CROSS criteria were used to evaluate the rationality of hydraulic parameters. The result shows that downstream areas with large cross-sections may suffer from shallow water depths, insufficient wetted perimeters, and poor overall connectivity of the water bodies, even under the standard EF discharges. A novel method was proposed to ensure EF and sustain suitable hydraulic conditions. The minimum EF calculated by the Tennant method is adopted as the design flow, and a small trapezoidal trough channel is excavated on the wide riverbed of an artificial river section. The width and depth of the small channel are calculated with Manning's equation. As a study case, this method was applied in the Fenglingang River in Zhejiang Province of China. A trapezoidal groove with a depth of 0.74 m and a bottom width of 0.52 m was excavated in the center of Fenglingang River to sustain EF and maintain river connectivity. This small channel not only prevents the river from cutoff, but also enables the water depth and wetted perimeter to meet the demand of aquatic organisms.

Dissolved oxygen transfer along falling water jets with developing surface disturbance

The dissolved oxygen (DO) concentration is an important index of water quality. It has a significant impact on the biodegradation process in water and the survival of aquatic organisms. Low DO concentrations often exist and may result in a deterioration in water quality and an increase in wastewater treatment expenses. An analysis of the oxygen transfer efficiency as correlated with the flow characteristics of a falling jet could help to solve these problems. Experiments related to oxygen transfer along a falling water jet were conducted, and the effects of the flowrate (Q), falling height (H) and initial DO concentration (cu) were considered. The results demonstrated that a falling jet in air could be an effective way of improving the DO concentration. The results also indicated that the oxygen transfer efficiency is linearly dependent on cu and has a negative exponential relation with H. To deeply analyze the oxygen transfer process, the jet disturbance process was divided into 3 parts for the first time based on flow features: a smooth zone, turbulent zone and breakup zone. The results showed that the jet outlet velocity had a limited influence on the smooth zone height but assisted in jet breakup. Thereafter, a correlation modeling DO reaeration along the falling jet considering jet disturbance characteristics was obtained. This correlation was also applied to predict the aeration efficiency in experimental cases from the literature and showed good agreement with the reported results.

Effects of Photoperiod Regimes on Growth Performance of Heterobranchus bidorsalis (Geoffrey St. Hilaire, 1809) fingerlings under Laboratory Conditions

Environmental factors are known to influence growth and survival of aquatic organisms. Varying intensities of light can be of great advantage to catfishes

The Influence of Anisotropic Sediment Layer on Dissolved Oxygen Transfer in Turbulent Flows

AbstractThe concentration and distribution of dissolved oxygen (DO) are critical to the self‐purification capacity of water and the survival of aquatic organisms, and they are important factors considered in the ecological balance system of water resources. In this work, the high‐Schmidt number DO transfer phenomenon in open channel flows with anisotropic sediment beds is studied using large eddy simulation. The volume‐averaged Navier‐Stokes equations coupled with the Monod equation is used to describe the in‐sediment flow and the sediment oxygen demand of micro‐organisms, so as to examine the transport characteristics of DO inside and outside the sediment layer. The effects of various permeable conditions of sediments (characterized by the anisotropy index of permeability, i.e., λ) on the distribution of DO concentration and flux, penetration depth, and mass transfer processes is studied by means of the time‐averaged statistics variations in flow and scalar fields. A larger anisotropy index λ is found can enhance the transport of DO from the water flowing into the sediment layer, which is caused by turbulent diffusions and turbulence bursting events. It suggests that the λ‐dependent distributions of the DO fluctuations and fluxes are highly correlated with the coherent structures in the turbulence over the sediment‐water interface (SWI). A key relationship between the Sherwood number and the anisotropy index is found by means of the current simulations and also is verified by our theoretical analysis. The dependence of λ on DO penetration depth is consistent with the hypothesis that coherent turbulence in the water column drives mass transport across the SWI.

Interaction between watershed features and climate forcing affects habitat profitability for juvenile salmon

AbstractOpportunities for growth and survival of aquatic organisms are spatially and temporally variable as habitat conditions across watersheds respond to interacting climatic, geomorphic, and hydrologic conditions. As conservation efforts often focus on identifying and protecting critical habitats, it is important to understand how this spatial and temporal variation in habitat quality affects the production dynamics of populations. Here, we use microchemical records preserved in otoliths to reconstruct juvenile habitat‐use by sockeye salmon that survived to spawn in a single population on the Alaska Peninsula. Successful individuals demonstrated a diverse array of juvenile behavioral strategies both within and among years. Importantly, the dominant juvenile behavioral strategy used by successful individuals changed among years, suggesting shifts in the relative benefits of different rearing habitats. The growth benefits of remaining in a more productive rearing lake were greatest in warm years indicating environmental influence on relative habitat quality. However, we found no strong relationship between the amount of growth accumulated in the productive rearing lake and overall population productivity across years. These results highlight the dynamic nature of habitat conditions and the beneficial effect of maintaining connectivity between diverse habitats for population productivity. When short‐term studies are used to demonstrate the relative values of different habitats to species of conservation concern, there is a distinct risk of under‐valuing habitats that may be critically important under alternative environmental conditions. In particular, land‐use decisions that reduce the range of habitat options available to species may erode a population’s ability to withstand environmental change over the long term.

Hemocytes transcriptomes reveal metabolism changes and detoxification mechanisms in response to ammonia stress in Octopus minor.

Ammonia is one of the major aquatic environmental pollutants that can bring detrimental effects to the growth and survival of aquatic organisms. However, the molecular mechanisms of ammonia toxicity and ammonia excretion in marine invertebrates especially mollusks are still poorly understood. Cephalopods are exclusively ammonotelic with high protein metabolism and ammonia excretion rate, making this taxonomic group an ideal specimen to explore the ammonia detoxification mechanism. In this study, comparative transcriptomes were employed to investigate the transcriptional changes of O. minor in responses to acute ammonia exposure. A total of 63,237 unigenes with an average length of 811 bp were discovered and 25,708 unigenes were successfully annotated. The transcription of 1845 genes were significantly changed after ammonia stress, including 315 up-regulated genes and 1530 down-regulated genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis based on differentially expressed genes (DEGs) revealed that 44 GO terms and 55 KEGG pathways were over-represented. Notably, a large number of genes involved in immune defense, citric acid (TCA) cycle, oxidative phosphorylation and amino acid metabolisms were significantly down-regulated, indicating the decelerated energy production and amino acid rate in response to acute ammonia stress. These results provide new insights into the potential molecular mechanism of ammonia detoxification on transcriptomic level and will facilitate further mechanism studies on mollusks.

Effects of Sudden Drop in Salinity on Osmotic Pressure Regulation and Antioxidant Defense Mechanism of Scapharca subcrenata.

Salinity is an important ecological factor that impacts the growth and survival of aquatic organisms. The salinity of seawater in coastal and estuarine areas is often subject to dynamic changes because of seasonal rainfall and continental runoff. Thus, the current study investigated the effects of sudden changes in salinity on the survival rate and osmotic pressure regulation mechanisms of bottom-sowing seedlings of the economically important ark shell, Scapharca subcrenata. By simulating the sudden changes that occur in seawater salinity after rainstorms, the results showed that the osmotic pressure of the hemolymph and Na+, K+, Ca2+, and Cl– concentrations first decreased and then increased. When the salinity decreased from 30 to 14‰, hemoglobin, soluble total protein, taurine, and total free amino acid gradually increased; maximum levels of hemoglobin, soluble total protein, and taurine occurred once the salinity increased to 22‰ at 96 h. After 96 h, the total free amino acid content increased until 144 h. The reactive oxygen species (ROS) content and total antioxidant capacity (T-AOC) peaked at 96 h, whereas the expression levels of Mn-superoxide dismutase (MnSOD) and catalase (CAT) increased earlier, indicating that, with continuous ROS generation, antioxidant defense mechanisms were activated to avoid oxidative damage. Expression levels of cathepsin C (CTSC), cathepsin D (CTSD), heat shock protein 20 (HSP20), and heat shock protein 70 (HSP70) were significantly higher than in the control group at 48 h (salinity level 14‰); the expression levels of HSP20, heat shock protein 90 (HSP90), MnSOD, and glutathione peroxidase (GPx) remained high, indicating that they were still required for osmotic pressure regulation to maintain the dynamic balance between the generation and removal of ROS as the salinity level increased. These results not only add to our basic understanding of the aquatic ecology of S. subcrenata, but also provide a theoretical ground for improving the survival rate of bottom-sowing, propagation, and release of S. subcrenata seedlings.

Dynamics of heat transport across sediment deposited hyporheic zone inside reservoirs following hydropower production

Heat transport through hyporheic zones is critical for many temperature-sensitive biogeochemical processes and survival of aquatic organisms. Water storing and releasing in the reservoir are often made to modify hydropower production, which may cause hydrological variation and alter heat transport regime across the hyporheic zone inside the reservoir. In this study, we investigated heat transport across the hyporheic zone within a sediment deposited bar inside a hydropower reservoir on the mainstream of the upper Mekong River. Hydrothermal dynamics in the hyporheic zone following hydropower production were analyzed by monitoring changes of water level and temperature using automatic monitoring wells. Results showed that hydropower production induced water level fluctuations, enhanced hyporheic exchanges and thereby accelerated heat transport across the bar. The hyporheic zone was a heat source for the reservoir water regardless of the time of the year. In summer, heat transport from the bar hyporheic zone to the reservoir was strong (0.50 × 108–10.28 × 108 J m−1 d−1) and mainly occurred through near-surface sediment layer (0–0.5 m), which was attributed to active hyporheic exchanges and strong solar radiation. In winter, heat transport was weak (0.01 × 108–1.01 × 108 J m−1 d−1) and mainly occurred in sediment bottom layer (< 1.0 m) with limited energy inputs from microbial activities. This study adds to our understanding of hydrothermal dynamics in hyporheic zones under flow regulations by dams.

Assessment of Hydrological Changes and Their Influence on the Aquatic Ecology over the last 58 Years in Ganjiang Basin, China

Runoff is the key driving factor of the Ganjiang River ecosystem. Human activities such as reservoir construction have greatly changed the state of runoff. In order to analyze the influence of Ganjiang Reservoir on the hydrological regime, the following paper is based on the daily precipitation data of 53 rainfall stations in Ganjiang River Basin from 1959 to 2016, and the daily runoff data of three stations in Dongbei, Ji’an, and Waizhou from 1959 to 2016. The Mann–Kendall test (MK) was used to analyze the trend of precipitation and runoff in Ganjiang River Basin. The Sliding t-Test (ST) was used to determine the abrupt change time of runoff in flood season within typical cross-sections of upper, middle, and lower reaches of Ganjiang River Basin, Ji’an, and Waizhou. Indicators of hydrological change (IHA), range of variability approach (RVA), and other methods were used to analyze the changes of 32 hydrological indicators in Ganjiang River Basin. The results showed that (1) The annual and flood season precipitation in Ganjiang River Basin increased from 1992 to 2016, but it did not reach a significant level. The change of annual runoff at Dongbei and Waizhou Stations was the same as that of the annual precipitation in Ganjiang River Basin. The runoff of Dongbei Station in flood season decreased from 1986 to 2016, and the runoff of Waizhou Railway Station in flood season decreased from 2008 to 2016. It showed that precipitation had a great influence on annual runoff, and human activities made the annual runoff distribution process more uniform; (2) The abrupt changes of runoff in flood season at three hydrological stations in Ganjiang River Basin occurred in 1991, and reached a significant level of 0.01; (3) There were five hydrological indicators of Dongbei Station which had reached height change. The change degree of low (l) pulse duration was −92.24%, the change degree of high (h) pulse count was −86.8%, the change degree of flow rise rate was 87.06%, the change degree of fall rate was −92.24%, and the change degree of number of reversals was −100%. Four hydrological indicators of Ji’an Station had reached high change degree, the count and duration of high pulse changes were −73.33% and −73.65%, the change degree of fall rate was −79%, and the change degree of number of reversals was −100%. Waizhou Station did not reach the high change indicator. The hydrological regime of the upper and middle reaches of Ganjiang River has changed greatly, while the hydrological regime of the lower reaches has changed little. The hydrological regime in the upper and middle reaches of Ganjiang River Basin has been highly changed by human activities such as dam construction. The change of hydrological conditions in the upper and middle reaches of Ganjiang River Basin may reduce the area of aquatic organisms’ habitat, be harmful to the spawning, migration, and survival of aquatic organisms, reduce the interception of organic matter in floodplains, and increase the drought pressure of plants. The reservoir ecological operation of rivers with numerous reservoirs should be considered, joint reservoir dispatching schemes should be formulated for the study area so as to maximize the comprehensive benefits. This study provides a reference for water resources management and reservoir operation in Ganjiang River Basin. The next step is to use a habitat model to simulate the habitat of Ganjiang River Basin.

Effects of specific wavelength spectra on antioxidant stress and cell damage of the ornamental cleaner shrimp Lysmata amboinensis (De Man, 1888) (Decapoda, Caridea, Lysmatidae) exposed to changing saline environments

AbstractA variety of environmental factors have a major influence on the survival of aquatic organisms, particularly light and salinity, changes in which lead to a range of physiological changes. In the present study, we investigated the levels of stress caused by changes in salinity in the ornamental cleaner shrimp,Lysmata amboinensis, as well as the effect of specific light wavelengths following stress to changes in salinity. We measured the activity of superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation (LPO) in the tissues (gill, hepatopancreas, and muscle) for three days after irradiating shrimp with specific wavelengths of light [red (630 nm), green (520 nm), and blue (455 nm)] at two intensities (0.5 and 1.0 W/m2) following exposure to different saline environments [25 practical salinity units (psu), 30 psu, 35 psu (normal seawater), and 40 psu]. DNA damage was measured using comet assays. Although all of the experimental groups exhibited negative results to changes in salinity, the green and red light groups exhibited positive effects when compared to the other wavelengths and fluorescent light. The effect of wavelength was not influenced by the intensity. In conclusion, the light of green and red wavelengths effectively reduces antioxidant stress and cell damage in cleaner shrimp.

Hypoxic acclimation leads to metabolic compensation after reoxygenation in Atlantic salmon yolk-sac alevins

Hypoxia is common in aquatic environments and has substantial effects on development, metabolism and survival of aquatic organisms. To understand the physiological effects of hypoxia and its dependence on temperature, metabolic rate (ṀO2) and cardiorespiratory function were studied in response to acute hypoxia (21→5kPa) at different measurement temperatures (Ta; 4, 8 and 12°C) in Salmo salar alevins that were incubated under normoxic conditions (PO2=21kPa) or following hypoxic acclimation (PO2=10kPa) as well as two different temperatures (4°C or 8°C). Hypoxic acclimation lead to a developmental delay manifested through slower yolk absorption. The general response to acute hypoxia was metabolic depression (~60%). Hypoxia acclimated alevins had higher ṀO2s when measured in normoxia than alevins acclimated to normoxia. ṀO2s were elevated to the same degree (~30% per 4°C change) irrespective of Ta. Under severe, acute hypoxia (~5kPa) and irrespective of Ta or acclimation, ṀO2s were similar between most groups. This suggests that despite different acclimation regimes, O2 transport was limited to the same degree. While cardiorespiratory function (heart-, ventilation rate) was unchanged in response to acute hypoxia after normoxic acclimation, hypoxic acclimation led to cardiorespiratory changes predominantly in severe hypoxia, indicating earlier onset and plasticity of cardiorespiratory control mechanisms. Although ṀO2 in normoxia was higher after hypoxic acclimation, at the respective acclimation PO2, ṀO2 was similar in normoxia and hypoxia acclimated alevins. This is indicative of metabolic compensation to an intrinsic ṀO2 at the acclimation condition in hypoxia-acclimated alevins after re-exposure to normoxia.

Assessment of Allowable Thermal Load for a River Reservoir Subject to Multi-Source Thermal Discharge from Operating and Designed Beloyarsk NPP Units (South Ural, Russian Federation)

This study develops a quantitative approach to the establishment of a maximum allowable thermal discharge into a freshwater body (the Beloyarsk Reservoir) incorporated in the once-through cooling technology at the Beloyarsk nuclear power plant (NPP) (South Urals, Russian Federation). The study is based on a 3-D hydrodynamic model, embracing water circulation, heat transfer, and ice-cover formation in the Beloyarsk Reservoir. The model is driven by atmospheric forcing, river runoff, and the discharge/intake of NPP cooling water. It was used to simulate the horizontal and vertical distribution of water temperature under the effect of the operation of existing (number 3) and anticipated (numbers 4 and 5) nuclear power units. The model is validated by the comparison of the computation results with observed water temperature distribution and ice-cover configuration obtained with remote sensing techniques. The model was also used to predict the future evolution of water temperature after the launching of two new power units, which, having a common cooling system, may affect each other. It was shown that the first of the new units, no. 4, will not dramatically affect the existing thermal conditions in the reservoir, while launching one more unit, no. 5, will apparently result in overheating of the reservoir water in response to the greater volume of cooling-water discharge from the two power units. Because of a specific configuration of the recirculation flow, the reservoir may fail to cope with the dissipation of the generated heat, leading to a steady (uncontrolled) rise of water temperature in the inlet channel to one of the power units. This will reduce the potential of NPP, using the once-through cooling technology, and will most likely have an adverse effect on the survival of aquatic organisms in the Beloyarsk Reservoir. Therefore, some other environment-saving technologies must be developed for removing surplus heat from the unit no. 5 of the Beloyarsk NPP.