Aquatic Environmental Factors Research Articles

Assessing the mangrove community structure and aquatic environmental factors of the mangrove ecosystem in Jangkaran Village

Coastal areas have the potential for damage caused by abrasion, strong winds, and tsunamis. Seeing the high potential for damage that might occur, the appropriate approach is to conserve mangrove forests, one of which is found in Jangkaran Village, Temon District, Kulon Progo Regency. This study aims to identify mangrove community structure and aquatic environmental factors in Jangkaran Village. Mangrove community structure was analyzed using the importance value index and the Shannon-Wiener diversity index. Aquatic environmental factors were analyzed using temperature, pH, dissolved oxygen, and salinity parameters. Data collection was carried out in three locations in Jangkaran Village. Mangrove vegetation data were taken from each transect using the 10 m x 10 m quadrat transect method. Data on aquatic environmental factors were taken directly at the location using a refractometer, DO meter, and pH meter. The results of this study are species with the highest importance index value in location 1, namely Rhizophora apiculata (117.094%), location 2, Avicennia marina (207.203%), and location 3, Avicennia marina (97.0362%). Shannon Wiener diversity indexes in the three locations are 0.6943, 0.4056, and 0.6841. The results of measurements of aquatic environmental factors are temperature 25.7-30.3 °C; pH 7.2-7.7; salinity 25-34; and dissolved oxygen 6.5-6.7. Thus mangrove diversity in Jangkaran village is included in the low category and the aquatic environmental factors is favorable for mangrove growth so that the mangrove ecosystem can be further developed.

Metals and biogenic substances’ migration ability in the «bottom sediments – water» system under natural and experimental conditions


 
 
 The paper considers the results of long-term studies on some chemical elements’ migration (Al, Fe, Ti, Mn, Cu, Zn, Pb, N, P, Si) in the «bottom sediments – water» system of surface water bodies under the effect of different aquatic environment factors. The greatest effect is made by water bodies’ oxygen regime, pH, and presence of dissolved organic substances, in particular humic substances. The migration of manganese, iron, inorganic nitrogen and phosphorus from bottom sediments is controlled mostly by oxygen regime. Migration of these chemical elements significantly increases, when there is oxygen deficiency and anaerobic conditions are formed in the bottom water layer. It has been observed in both natural and experimental conditions. Man- ganese concentration increases in bottom water in 25–50 times, iron – in 1.3–13, inorganic nitrogen – in 5.3–19.3, and inorganic phosphorus – in 2.8–23 times. The dissolved oxygen concentration hardly has any effect on the migration of aluminium, titanium, copper, zinc, lead, and silicon from bottom sediments into the water. The chemical elements’ migration is significantly affected by a decrease in pH of water contacting with bottom sediments and the presence of humic substances in it. High humic substances concentrations promote a reduction in water pH and oxygen content, which is consumed for their oxidation. A case study of several water bodies illustrates the cumulative effect of water pH lowering, anaerobic conditions at the solid and liquid phases’ interface, as well as complexation with humic substances on chemical elements’ migration from bottom sediments. Experimental modeling has shown that the metal migration from bottom sediments occurs both due to their labile fractions and complex compounds with dissolved organic matter, especially with humic substances of low molecular weight (≤2.0 kDa). The share of the metal labile fraction gets higher, when water pH decreases. Under recent climate change, the probability of water’s secondary pollution with different chemicals increases significantly in summer. This is mainly caused by oxygen deficiency, water pH lowering, and reducing conditions at the «bottom sediments – water» interface with hydrogen sulphide being formed. This is especially true for highly eutrophic water bodies subject to human impact. The aquatic environment toxicity can get considerably higher due to the migration of chemicals with strong toxic properties from bottom sediments, as well as labile metal fractions, marked by higher bioavailability for hydrobionts.
 
 

Effects of land use and aquatic environmental factors on secondary productivity of macroinvertebrates:A case of Lake Lianhuan Group, northeast China

Effects of land use and aquatic environmental factors on secondary productivity of macroinvertebrates:A case of Lake Lianhuan Group, northeast China

Feeding characteristics and assessment of histopathological changes in the organs of the Sandpiper goby (Neogobius fluviatilis)

The paper presents data from ichthyological, trophological and histological studies of the Sandpiper goby (Neogobius fluviatilis) endemic to the Caspian Sea, which has an important role in trophic chains, as food object for sturgeon, semi-migratory fish species, marine migratory Clupeidae family and Caspian seal. Place of sampling for the study were stations in the Northeastern part of the Caspian Sea, which is inferior in trophic content to its other parts, which had confirmed by data from trophic studies. The basis of the studied fish nutrition was Polychaeta, Bivalvia, Crustacea and in some cases juvenile fish, which indicates their nutritional plasticity, and the fact that they are not competitors to each other in nutrition. Depending on results of fish’s visceral organs histological studies, structural changes were determined, which were more adaptive in nature and were a response to the impact of aquatic environment factors. In gills was found protozoan invasion causing hyperplasia of secondary lamellae epithelium and sloughing of respiratory epithelium. There were growths of the epithelial layer of villi in the intestine. In the liver and pancreas were detected fatty degeneration and necrotic changes. In all organs were found microcirculatory disorders, including the presence of erythrocytes with hyperchromic cytoplasm.

Monitoring of Aquatic Environmental Factors on the Growth of Whiteleg Shrimp (Litopenaues vannamei Boone, 1931)

The environment is an important aspect and can be an indicator of the success of whiteleg shrimp culture. Stable water quality is a condition when water quality meets the requirements of growing whiteleg shrimp. This study aims to determine the aquatic environmental factors on the growth of whiteleg shrimp. There were 3 ponds observed in this research with an area of 2.000 m2, 2.500 m2, and 350 m2 respectively. The result of the research shows that the water quality of whiteleg shrimp culture is still in the feasible category. Several parameters show fluctuated results beyond optimal values such as dissolved oxygen, salinity, total ammonia nitrogen, and total organic matter. The results of the correlation test showed that all the quality parameters of whiteleg shrimp culture had varying degrees of relationship. The highest correlation level was obtained in salinity, nitrate, nitrite, ammonia, temperature, and dissolved oxygen. Water quality in each pond has a very strong relationship to the growth of mean body weight (10.31 g, 10.92 g, and 11.39 g), average daily growth (0.4142 g, 0.4971 g, and 0.3557 g), and survival rate (92.4%, 92.4%, and 92.3%).

Spatial and Temporal Characteristics of Phytoplankton Communities in Drinking Water Source Reservoirs in Shenzhen, China

Phytoplankton diversity and community characteristics are closely associated with aquatic environmental factors. Understanding these dynamics can provide insights into the ecological health of water bodies. We investigate the spatial and temporal characteristics of phytoplankton communities in 27 drinking water source reservoirs in Shenzhen, China. As a method, we collected samples during the dry season in 2021 and the wet season in 2022, analyzed the alpha and beta diversities of phytoplankton communities, and correlated these with the environmental factors. The results reveal that Cyanobacteria dominate the phytoplankton communities in the Shenzhen reservoirs. Phytoplankton diversity is greater during the dry season. The algal composition varies spatially, and the phytoplankton diversity tends to decrease with increasing eutrophication. A co-occurrence network analysis indicates denser and stronger correlations among phytoplankton nodes during the wet season than dry season. Reservoirs with moderate eutrophication levels exhibit denser nodes and stronger correlations compared to those with low or high eutrophication levels. The chemical oxygen demand, water temperature, pH, and total nitrogen are identified as key influencers of the phytoplankton community structure. Our results contribute to the enhanced understanding of the spatial and temporal dynamics of phytoplankton communities in reservoirs in South China and provides insights into the management and conservation of these drinking water reservoirs.

Hard coral cover in the Halmahera waters: Spatial distribution and environmental factors

Differences in the geographical location and geomorphology of small islands contribute to variations in aquatic environmental factors, spatial distribution of corals, and percentage of hard coral cover. This study was conducted in the open waters of the Termadoreh Islands in the middle of the Maluku Sea, and the semi-enclosed waters of Buli Bay. This study aimed to examine the distribution of hard coral cover in the Halmahera coral ecoregion with respect to differences in geographic location, geomorphology and water quality. This study found that the spatial distribution of hard corals differed among sites. Spatially, the total area of shallow water habitat at the study site showed the largest area of coral habitat in Termadoreh, at 1313.99 ha. Hard coral cover and coral diversity differed between sites and depths. Higher hard coral cover was found on the coral islands of Teluk Buli and lower on the volcanic islands of the Termadoreh Archipelago. The highest percentage of hard coral cover per site was found on Maitara Island (site MaT05) at 71.60%, and the lowest percentage of cover was found on Tidore Island (site TiT08) at 14.9%. An optimal temperature, salinity, and brightness parameters support the high percentage of hard coral cover. The highest coral diversity value in the Termadoreh Islands correlated with water brightness. This study is important for recording the conditions of hard corals in the Halmahera reef ecoregion. The results of this study provide data on the benefits of a coral reef management plan for the Halmahera coral ecoregion. We also provide recommendations regarding the life forms of hard corals that are appropriate for making coral seeds to restore and rehabilitate coral reef ecosystems at the research sites.

Winter and Summer Variations in the Physiological Parameters of Two Scleractinian Corals in Sanya Bay

Coral reefs in Sanya Bay have been degrading in recent decades under climate change and human activities. To identify physiological changes of scleractinian corals and corresponding influencing factors, aquatic environmental factors and physiological parameters of Pocillopora damicornis, Porites pukoensis and their symbiotic zooxanthellae were examined in four Sanya Bay coral reef areas in December 2020 (winter) and July 2021 (summer). The density and chlorophyll a+c2 content of the symbiotic zooxanthellae were significantly high in winter and low in summer. Superoxide dismutase and caspase3 activities of corals and zooxanthellae were high in summer and low in winter, whereas catalase activity showed the opposite pattern. The variations were consistent for both coral symbionts. Water temperature and salinity were the main factors affecting the physiological variations of corals. Compared with winter, the high temperature/low salinity aquatic environment in summer reduced the density and chlorophyll a+c2 content of zooxanthellae, resulting in high superoxide dismutase and caspase3 activities in the corals and zooxanthellae. In addition, turbidity was an important factor affecting the physiological characteristics of coral–zooxanthellae symbionts among the four coral reef areas. Our results have important implications for understanding the changes in coral reef communities in Sanya Bay and coral reef protection.

Species specifics of morphology of the liver of the fishes of the Cyprinidae family

Providing mankind with high-quality products of aquaculture is possible only by introduction of modern industrial technologies to fish farming, growing fish based on modern scientific achievements. Assessment of the ecotoxic situation and identification of impacts of various unfavourable factors of aquatic environment on aquatic organisms should be made through morphological studies of the organs that are first to encounter the impact. The study revealed species specifics of the morphology of the liver of the fishes of the Cyprinidae family – Prussian carp (Carassius gibelio), Eurasian carp (Cyprinus carpio), and bighead carp (Hypophthalmichthys nobilis), which vary by extent of the motor activity in the aquatic environment, nutrition, etc. We determined that during phylogenetic development of fish that grow in the aquatic environment, there occurs a certain restructuring of the liver: the adaptation to various living conditions were accompanied by changes in a number of parameters of macro- and microscopic architectonics of the liver. Cyprinus carpio and Carassius gibelio (omnivores) have a two-lobe liver, while Hypophthalmichthys nobilis (a herbivore) has a three-lobe liver. For C. carpio and H. nobilis, a characteristic feature of the liver was presence of the hepatopancreatitis (the liver and the pancreas, associated into a single organ), and in C. gibelio, they are differentiated into individual organs. A peculiarity of the microscopic structure of the liver of the Cyprinidae family is poorly developed interlobular connective tissue, and parenchyma of the liver lobule has a tubular structure as polyhedral, curved thick-walled tubules, the walls of which are hepatocytes. The greatest amounts of cytoplasm and karyoplasms were seen in C. gibelio, equaling respectively 12.98 ± 1.42 and 0.40 ± 0.02 µm³. The lowest volume of the indicated parameters was in C. carpio, particularly 2.97 ± 0.22 and 0.21 ± 0.01 µm³, respectively. The lowest nuclear-cytoplasmic ratio was observed in hepatocytes of C. gibelio (0.0316 ± 0.0024). The conducted morphological studies at the levels of organs, tissues and cells can reveal how the fishes’ bodies adapt to particular living conditions and impacts of environmental factors.

Biochemical effects in deep-sea divers exposed to aquatic environmental factors

Relevance. Diving equipment and diving launch techniques witness continuous improvements, which allow individuals to more effectively perform various tasks underwater. A controlled electronic closed circuit rebreather has been used in amateur diving in our country for more than 20 years. It is therefore necessary to assess the biochemical effects in deep-sea divers wearing deep sea diving equipment to ensure its safety and functionality in professional diving and the activities of dedicated departmental structures.The objective is to assess the biochemical effects in deep-sea divers in controlled electronic closed circuit rebreather, with a similar level of intravascular decompression gas formation under the influence of aquatic environment factors.Methods. During the study, 9 blood biochemical parameters were evaluated using the Fujifilm DRI-CHEM NX500 apparatus in 6 divers before and after deep-sea descents. In total, 14 diving descents were performed in a controlled electronic closed circuit rebreather to depths from 60 to 100 m. Also, after each diving descent, the level of intravascular decompression gas formation was assessed using ultrasonic location with the constant-wave Doppler effect.Results and Discussion. As a result of these studies, a significant increase in the values of transaminases (ALT, AST) and urea was established, associated with increased partial pressure of oxygen in hyperbaric aquatic environment. The results of the analysis revealed that indicators of the CNS oxygen intoxication correlated with K+ ions concentration and glucose levels; a correlation between Na+ ions and Cl- ions concentration was established, as well as the inverse relationship between the concentration of urea and creatinine and the level of intravascular decompression gas formation. It is noteworthy that a correlation was found between the level of intravascular decompression gas formation and the CNS oxygen intoxication, whereby an increase in the CNS oxygen intoxication leads to increased levels of intravascular decompression gas formation.Conclusion. The studied blood biochemical parameters did not go beyond the reference values and had slight individual variations, which confirms the safety of the technology of descents in diving breathing apparatus with a controlled electronic closed circuit rebreather at depths of more than 60 m. The results of the correlation analysis revealed changes in carbohydrate and water-electrolyte metabolism in the body of divers after a deep-sea descent due to the action of an increased partial pressure of oxygen and intravascular decompression gas formation.

Химическая маркировка взрывчатых веществ для повышения безопасности взрывных работ

The article is devoted to the development of a marking composition for industrial explosives to improve the safety of blasting. Polymethylsiloxane liquids of PMS-10 and PMX-200 grades were chosen as a marker-identifier of industrial explosives, which can be identified even after the explosion by residual fragments of soil or other materials from the epicenter of the explosion. Polymethylsiloxane fluids are very heat-resistant, the combustion process takes place with great difficulty, they are little affected by the aquatic environment, most chemical and physical factors that destroy ordinary organic materials. The experiments were carried out to determine the physicochemical parameters of polymethylsiloxane liquids PMS-10 and PMX-200. Based on these results, the polymethylsiloxane liquid PMX-200 with linear chains was chosen as a marking additive in the composition of explosives. It is able to withstand a higher-temperature effect than the PMS-10 polymethylsigsane fluid, and will be less disintegrate, and interact with the products of the explosion. The SIM-K marker, made on the basis of polymethylsiloxane liquid PMX-200, was developed, which allows to visualize the explosive and determine the required identification information. At the technological plant of Orika-Kazakhstan JSC, without disturbing the technological process, a marking composition was introduced into the ANFO explosive by drop spraying. Field tests of the ANFO explosive with a marking composition based on PMX-200 polymethylsiloxane liquid were carried out. The technology was tested related to introduction of marking additives into the compositions of multicomponent explosives without violating the technological process of their manufacture.

Characterization of dynamic plastisphere and their underlying effects on the aging of biodegradable and traditional plastics in freshwater ecosystems

Recently, biodegradable plastics (BPs) are emerging as a sustainable alternative to traditional plastics. When released into an aquatic environment, the biodegradable performance of BPs is influenced by biochemical processes, especially the developed plastisphere. However, studies addressing the biodegrading capacity of BPs and traditional plastics within the plastisphere are still limited. Here, we investigated plastisphere community variations and their capacity to biodegrade polyethylene terephthalate (PET) and starch-based plastics (SBP) for four time periods (15, 30, 45, and 80 days) in three freshwaters. Unexpectedly, there is no significant difference in the microbial communities and network structure of the plastisphere between SBP and PET. Moreover, SBP tended to age rapidly at the early stage (0–15 days), while the aging degree of SBP and PET did not display an obvious difference at 80 days. Partial least squares path modeling suggested that plastic aging was mainly dominated by keystone taxa of network and aquatic environmental factors. These results suggest that the aging rate of commercial BPs may not be as fast as we imagine in freshwaters (SBP ≈ PET), and the environmental behaviors of BPs in the aquatic environment should be paid more attention to.

Effects of ammonia exposure on anxiety behavior, oxidative stress and inflammation in guppy (Poecilia reticulate)

Ammonia is one of the most important aquatic environmental factors, which is of great concern. In order to evaluate the effect of ammonia on guppy (Poecilia reticulate), fish were exposed to increased concentrations (0, 12.50, 25.00, 41.67, 62.50 mg/L) of ammonia for 48 h. After exposure, we measured the anxiety behavior, antioxidant enzymes and pro-inflammation genes (TNF-α, IL-1β and IL-6) of guppy. The results showed that ammonia stress induced fish anxiety, which was manifested by the increased latency to enter the upper half and decreased time spent in upper half compared with control fish. The guppy showed oxidative stress after 48 h of ammonia stress as evidenced by decreases in the activities of antioxidant enzymes and an increase in lipid hydroperoxide content. With prolonged ammonia stress, the expressions of HSP70, HSP90, TNF-α, IL-1β and IL-6 mRNA at first had an increasing trend, and then decreased, all of which were significantly higher than the control levels at 12 h and 24 h after ammonia stress (P < 0.05). Ammonia significantly upregulated these genes mRNA levels after 48 h exposure, suggesting that heat shock proteins and innate immune system may try to protect cells from oxidative stress induced by ammonia stress. Our study showed that higher ammonia exposure induced oxidative stress in exposed fish, since inhibition of antioxidant enzymes activity and increases in lipid peroxidation, and inflammation occurred. Furthermore, the results will be helpful to understand the mechanism of ammonia toxicity in guppys.

Sediment phosphorus immobilization with the addition of calcium/aluminum and lanthanum/calcium/aluminum composite materials under wide ranges of pH and redox conditions

Aquatic environment factors often influence and regulate the direction of phosphorus (P) flow at the sediment-water interface (SWI). High pH and low DO, common in eutrophic lakes, would induce large releases of P from sediment, and thus cause the negative effect on the efficiency of some P-passivators. Hence, the development of P passivators that could function over a wide range of pH condition and redox state in the overlaying water with reduced undesirable side effects is critical for the eutrophic lake remediation. In the present study, a calcium (Ca)/aluminum (Al) composite (CA) and a lanthanum (La)/Ca/Al composite (LCA) were prepared for P immobilization in lake sediments, using calcium and lanthanum coprecipitated with aluminum. CA and LCA were shown to have good P sorption performance at pH 4–11, particularly at pH 8–11. Furthermore, CA and LCA have an ability to correct the pH of water that deviates from neutral. The maximum P adsorption (Qmax) of sediment amended by 4 % CA and 4 % LCA increased by 83 % and 103 %, and their equilibrium P concentration (EPC0) decreased by 76 % and 88 %, respectively. Under various pH and DO conditions, the P concentration in overlying water was significantly decreased by CA and LCA amendment, and their addition could effectively counteract the P release from sediments induced by high pH and low DO. The mechanisms of P immobilization in amended sediments under various pH and DO levels are primarily the conversion of reactive P to stable P. The P immobilization performance of CA and LCA could cope with a wide range of pH and redox conditions in eutrophic lakes, and they would help to correct extreme pH values, thus they are expected to be a new generation of commercial P-passivators.

Transcriptomic Analysis of Large Yellow Croaker (Larimichthys crocea) during Early Development under Hypoxia and Acidification Stress.

Fishes live in aquatic environments and several aquatic environmental factors have undergone recent alterations. The molecular mechanisms underlying fish responses to hypoxia and acidification stress have become a serious concern in recent years. This study revealed that hypoxia and acidification stress suppressed the growth of body length and height of the large yellow croaker (Larimichthys crocea). Subsequent transcriptome analyses of L. crocea juveniles under hypoxia, acidification, and hypoxia-acidification stress led to the identification of 5897 differentially expressed genes (DEGs) in the five groups. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that several DEGs were enriched in the 'protein digestion and absorption' pathway. Enrichment analysis revealed that this pathway was closely related to hypoxia and acidification stress in the five groups, and we found that genes of the collagen family may play a key role in this pathway. The zf-C2H2 transcription factor may play an important role in the hypoxia and acidification stress response, and novel genes were additionally identified. The results provide new clues for further research on the molecular mechanisms underlying hypoxia-acidification tolerance in L. crocea and provides a basic understanding of the potential combined effects of reduced pH and dissolved oxygen on Sciaenidae fishes.

CURRENT STATE OF ZOOPLANKTON IN THE LOWER COURSE OF THE UKSUNJOKI RIVER (NORTHERN LADOGA REGION)

The zooplankton community of the lower course of a stream draining to the Lake Ladoga northern coast – the Uksujoki river was studied to estimate its current state as an essential structural and functional element of this lotic ecosystem, to assess the water quality based on zooplankton indicators and to determine what factors influence its development. Surveys in 2011–2016 showed the zooplankton community to include 53 taxa below the genus level, among them Rotifera – 16, Cladocera – 31, Copepoda – 6. During the surveys, 26 species and subspecies of zooplankton were recorded for the first time for this watercourse. Zooplankton quantities in the Uksunjoki were among the lowest among other 20 tributaries of Lake Ladoga during the spring, summer, and autumn seasons. The abundance varied from 10 to 2740 ind./m3, biomass from 0.0001 to 0.0330 g/m3. Quantitative indicators reached a maximum in September 2013. The highest season-averaged values of species richness, abundance, and biomass occurred in the summer period. In spring, Copepoda prevailed, represented by the nauplial and copepodite stages of Cyclopoida. In summer and autumn, cladoceran crustaceans from the family Chydoridae featured the largest numbers and biomass in the structure of the zooplankton community. Organisms that forage from the substrate surface (crawling-floating secondary filter feeders) predominated in the trophic structure of the zooplankton community. The development of species was stochastic. The most significant aquatic environment factors for the development of zooplankton in the Uksunjoki appear to be the water ionic composition and water discharge. As indicated by the zooplankton community, the water of the Uksunjoki River can be characterized as relatively clean and suitable for all types of water use.

Phytoplankton Biodiversity and Its Relationship with Aquatic Environmental Factors in Lake Sidi Mhamed Benali of the Wilaya of Sidi Bel Abbes (North-West of Algeria)

Phytoplankton Biodiversity and Its Relationship with Aquatic Environmental Factors in Lake Sidi Mhamed Benali of the Wilaya of Sidi Bel Abbes (North-West of Algeria)

Insights into heteroaggregation of polystyrene nanoplastics with hematite nanoparticles and configuration-dependent adsorption for PFOA and PFOS

While the homoaggregation of nanoplastics (NPs) has received a great deal of attention, their heteroaggregation with natural colloids is not well understood. In this study, the heteroaggregation behavior and mechanism of polystyrene nanoplastics (PSNPs) with hematite nanoparticles (HemNPs) were comprehensively investigated. The increase in the PS/HemNP mass concentration ratio led to a corresponding increase in the heteroaggregation rate, with the optimal heteroaggregation occurring at a PS/HemNP ratio of 0.0372. The primary heteroaggregation via electrostatic attraction and secondary heteroaggregation via interactions between the PS-HemNP agglomerates were the predominant heteroaggregation mechanisms. Specifically, the aquatic environmental factors had a great impact on the heteroaggregation processes, whereby the presence of Suwannee River humic acid (SRHA) (selected as a representative example of natural organic matter (NOM)) induced a remarkable heteroaggregation inhibition effect due to charge neutralization and steric repulsion. An increasing in pH weakened the electrostatic attraction between the particles, and resulted in a disaggregation of the PS-HemNP agglomerates. Furthermore, the heteroaggregation of the PSNPs with HemNPs formed large PS-HemNP agglomerates and shielded a number of available adsorption sites for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), resulting in the reduction of their adsorption removal by the agglomerates.

Metal-algae interaction contributes to the water environment heterogeneity in an urbanized river

The ecological environments of urban rivers are greatly affected by human activities, leading to serious water quality deterioration. We thus investigated urban aquatic environment and water pollution factors by collecting water samples over one year upstream, midstream and downstream of the Funan River in Chengdu, Sichuan, China. Measured water quality indicators included total N/P ratio, ammonia N, chemical oxygen demand, chlorophyll a, biochemical oxygen demand, transparency, turbidity, dissolved oxygen, conductivity, and pH, as well as the heavy metal concentrations and algal communities in the river sediments. Additionally, a water pollution index (WPI) and trophic level index (TLI) were calculated and a principal component analysis (PCA) was performed. The WPI analysis indicated serious pollution in this river during the sampling year. Moreover, moderate eutrophication with high pollution was found in summer (TLI = 64.7), while mild eutrophication occurred in the other seasons. The number of Cyanobacteria species sharply increased from 6 to 23 in summer, indicating a high risk of blooms. Furthermore, the PCA also revealed that two metals, chromium and cadmium, affected the water quality, which may be because of the interaction of nutrients and metals due to the land use types, industrial activities and hydrodynamic conditions. In general, we have systematically discussed the influences of various factors on the water environment and the mechanisms of their interactions in urbanized rivers, which is very important for the protection and restoration of river ecology as China and the world become more urbanized.

The ecological niche and terrestrial environment jointly influence the altitudinal pattern of aquatic biodiversity

The altitudinal distribution of biodiversity in alpine ecosystems has captured academic attention, especially in streams because of their sensitivity to climate change. In the past years, research mainly focused on understanding the role played by alpine streams' internal factors such as aquatic environmental variables, as well as physical and hydrological conditions, on the shaping of benthic macroinvertebrate communities. More recently, external factors such as terrestrial environments were included in analyses worldwide. In particular, the inherent properties constituting the ecological niche of specific species were considered as factors regulating dispersal and influencing community construction. The objective of this study was to reveal the distribution pattern and the driving factors regulating aquatic biodiversity in alpine streams. We hypothesized that the altitudinal distribution of aquatic macroinvertebrates could be explained by the interaction of the aquatic environment with both species' ecological niche and the terrestrial environment surrounding their habitat, and that rare species display a more pronounced pattern than widespread dominant species. To test these hypotheses, samples were collected from two alpine streams situated on opposite slopes of Biluo Snow Mountain in Yunnan Province, China. Results of statistical analyses showed poor explanatory power from aquatic environmental factors, while the differences in vegetation type and the ecological niche of the species played an important role in determining the distribution pattern of aquatic biodiversity. Furthermore, we found that the altitudinal distribution pattern of aquatic biodiversity exhibits a bimodal type, with rare species fitting the bimodal peaks. These findings call for a better inclusion and further investigation on the effects of the terrestrial environment on aquatic ecosystems.