Aquatic Ecology最新文献

Dams and barrages significantly impact the ecological functions of rivers by regulating water flow, causing fragmentation, and affecting water quality and biodiversity. To investigate the impact of dams and barrages on river ecosystems, this study used phytoplankton functional groups (FGs) as bioindicators of aquatic habitats in the subtropical Ganga River, India. We identified a total of 114 phytoplankton species, including 25 FGs. The summer season recorded the highest functional diversity (i.e., number of FGs), followed by the winter. The SIMPROF (Type 3) test classified phytoplankton FGs into six SIMPROF groups based on their frequency and location, using the coherent curve and dendrogram cluster analysis of FGs. Hierarchical cluster analysis using FGs suggested that dams and barrages influenced distribution and abundance. Kanpur was very polluted due to the highest levels of specific conductivity, phosphate, and total phosphorus. However, precipitation and surface runoff dilution significantly reduced pollution during the monsoon season. Redundancy analysis (RDA) strongly influenced six functional groups, namely D, A, P, C, MP, and X1, out of the 15 most prevalent functional groups. Consequently, the current study hypothesised that the series of dams and barrages would alter the hydrological features of successive reservoirs, affecting the regional and seasonal variations in functional diversity. To improve water quality and promote a wider range of FGs in the study region, ensuring minimal environmental flow is essential.

We assessed compositional and aggregate properties of fish assemblages inhabiting rocky intertidal pools of the coast of central Chile. Its association to sampling regions, localities, tidepool volume or dominant substrate was examined. A total of 1502 individual fish representing 20 species were collected in 49 single-time sampled tidepools from 3 localities at Valparaíso and 5 from the Biobío region. The dissimilarity in composition of the fish assemblages was larger between regions than among localities within regions. The most abundant taxa in Valparaíso were Helcogrammoides chilensis and Scartichthys viridis. In Biobío were Calliclinus geniguttatus, Gobiesox marmoratus, Myxodes viridis and Ophiogobius jenynsi. There were significant and positive but not strong correlations between the volume of tidepools with the total fish number and species richness. There were no significant correlations with dominance, diversity and total fish biomass. Consequently, density in biomass, density in number of fishes, and in number of species decreased similarly and steeply with tidepool volume in Valparaíso and Biobío regions, indicating a strong size effect of tidepool volume in both regions. These results indicate that community composition variability is independent of aggregate community and that a biogeographical compositional transition occurs in this area.

Alternanthera philoxeroides is an aquatic macrophyte native to South America that colonizes aquatic and humid habitats due to its high phenotypic plasticity. This study evaluated the growth of A. philoxeroides under two shading conditions and nutrient concentrations in its native range in South America. We collected specimens from the upper Paraná River floodplain (Brazil). The propagules (stem fragments) were planted and subjected to four treatments: (i) with nutrient addition and shading; (ii) without nutrient addition and without shading; (iii) with nutrient addition and without shading; (iv) without nutrient addition and with shading. After growing, we measured dry biomass, shoot and root length, and the number of branches. Biomass and relative growth rates were higher in the absence of shade and with the addition of nutrients. The shoots grew more with nutrient addition, while the roots grew more without shading. Branches developed only in the treatment with nutrients and no shading. However, nutrients alone were not sufficient to counteract the negative effect of shading on plant growth. These results indicate that A. philoxeroides thrives and has a greater potential to spread (through branch formation, which serves as an indicator of propagule pressure) in eutrophic and well-lit environments. In contrast, moderate shading significantly reduces plant growth and spread (via branching), even under eutrophic conditions.

Tropical riverine systems support diverse benthic macroinvertebrate communities that contribute to ecosystem functioning. However, these communities are increasingly vulnerable to anthropogenic disturbances, which can alter their taxonomic structure and functional trait composition. The Agusan River Basin (ARB) in Mindanao, Philippines—a socioeconomically important yet ecologically threatened system—has demonstrated signs of ecological degradation, primarily due to upstream deforestation, mining, and agricultural activities. This study examined the taxonomic and functional responses of benthic macroinvertebrate assemblages across seven rivers in the ARB under a gradient of agricultural land use to evaluate early signs of functional decline. Twelve environmental variables were measured, revealing significant differences in velocity, discharge, temperature, dissolved oxygen, pH, biological oxygen demand (BOD), chloride, phosphate, total suspended solids (TSS), and conductivity. Taxonomic analyses indicated a significant difference in species richness, while functional diversity analyses demonstrated considerable variation in functional richness. RLQ and fourth-corner analyses identified key trait–environment associations: large body size and cemented eggs were linked to cooler, faster-flowing sites with higher phosphate levels; flattened bodies and grazing behaviors were connected to warmer, slower waters; and streamlined bodies and small sizes were associated with high suspended solids. These findings suggest that anthropogenic pressures in the ARB are selecting for energy-conserving and stress-tolerant traits, potentially indicating early impairment of ecosystem functioning. The decline in functional richness and the dominance of conservative traits may reduce ecological resilience and alter population dynamics. Immediate conservation actions are essential to prevent further functional degradation and sustain biodiversity and ecosystem services in the ARB.

Riparian plant species produce leaf litter that decomposes in adjacent terrestrial and aquatic ecosystems. Despite their proximity, these ecosystems differ in decomposer communities, abiotic conditions, and nutrient availability, potentially influencing decomposition rates of common litter differently. We investigated leaf litter decomposition from eight riparian species in a tropical forest and adjacent reservoir, examining the individual and interactive effects of intrinsic (litter species identity and quality) and extrinsic (ecosystem type) factors. We hypothesized that: (i) decomposition would be faster and (ii) more variable in the aquatic ecosystem due to constant water immersion, enhanced microbial activity, and a greater heterogeneity; (iii) species identity effects would be mediated by ecosystem type; and (iv) distinct chemical litter traits would drive decomposition in each ecosystem. Results confirmed significantly higher and more variable decomposition rates in the aquatic ecosystem, likely due to greater leaching of soluble organic matter, continuous water availability, and metabolic characteristics of aquatic decomposers. Ecosystem type interacted with species identity among fast-decomposing species, altering decomposition rates and species rank order between ecosystems. As predicted, different litter chemical traits controlled decomposition in each ecosystem: increasing lignin-to-phosphorus (Lig:P) ratio reduced decomposition in the aquatic ecosystem, while increasing lignin-to-nitrogen (Lig:N) ratio constrained terrestrial decomposition. Lig:P also predicted the Relative Ecosystem Effect, which quantifies how slow litter decomposes in terrestrial relative to aquatic ecosystem. These findings highlight how nutrient imbalances shape decomposition dynamics across adjacent ecosystems and demonstrate that ecosystem type determines the biogeochemical mechanisms controlling decomposition at small spatial scales. Understanding these terrestrial-aquatic links is crucial for predicting carbon and nutrient fluxes in increasingly threatened riparian landscapes.

Macroalgae, as the dominant primary producers, play an important role in the south Caspian Sea in the rocky shore ecosystem food web. Recently, massive macroalgal blooms occur in this region every year. Studying water quality during the bloom is the first step to understanding the conditions that lead to extensive macroalgae growth in this area. Herein, spatio-seasonal distribution and biomass of the macroalgal community including three species Cladophora glomerata, Ulva intestinalis, and Osmundea caspica were investigated in 18 stations throughout the southern Caspian Sea shore line in relation to different environmental factors. In summer and autumn seasons 2021, C. glomerata was dominant species (90.3% and 70.1%, respectively), followed by U. intestinalis (9.7% and 26.5%, respectively). It was a strong variety of biomass along the coast (in 5–7 times) in a range of 30–470 gdw/m² in summer and nearly as twice as less in autumn, 15–250 gdw/m², that the same sites exhibit maximum of biomass in both seasons (Ramsar, Dastak, Sisangam, Amir Abad). During the bloom, the daily oxygen fluctuation was measured at Ramsar station, which showed a severe anoxia conditions. The anoxia in the coastal waters negatively affected shallow-water habitats and caused a sharp decline in macroinvertebrate density after C. glomerata decomposition. According to statistical analysis results, water temperature was the most effective factor (in comparison to pH and nutrients) influenced on distribution and biomass of macroalgal community with contribution of 42.01%.

Local and regional factors at different scales influence fish biodiversity in streams. Similarly, waterfalls can contribute to the distribution of species richness and composition of assemblages. The Upper Paraguay River basin is crucial for conserving various fish species, but few large-scale studies on fish assemblages can be found in the literature. To address this knowledge gap, we investigated the hydrological anomalies of waterfalls from two perspectives: their effects on the richness and composition of fish assemblages and their contribution to beta diversity in the Rio Negro basin, the largest tributary of the Paraguay River on its left side. We specifically considered the effects of regional (e.g., sub-basins and altitude) and local factors (e.g., mean flow, water conductivity, water pH, concentration of dissolved oxygen) on these metrics. To do this, we sampled fifty-seven stretches of streams in the headwaters of the Rio Negro basin from May to August 2020 (dry period), using a different sampling method with rectangular sieve, trawl net and electrofishing. The areas below the waterfalls exhibited greater fish richness explained by regional (e.g., altitude) and local (e.g., oxygen concentration and conductivity) factors. Species composition, however, did not differ relative to these factors. The greatest contributions to Local Contribution to Beta Diversity (LCBD) came from sites with the lowest altitude and lowest oxygen concentration. Our results demonstrate the effect of waterfalls on fish assemblages and help to estimate the large-scale effect of local and regional factors on fish species richness and composition in a relatively pristine ecosystem important to the conservation of Neotropical fish species.

This study, carried out seasonally between October-2019 and July-2020, aimed to determine the water quality using some water and epilithic diatom indices of the Köprüçay River. It is located in the south of Türkiye and used for tourism, irrigation and drinking water. Ammonium nitrogen (NH₄–N), nitrate nitrogen (NO₃–N), sulfate (SO₄⁻²), bicarbonate (HCO₃⁻), orthophosphate (PO₄–P), chloride (Cl⁻), biochemical oxygen demand (BOD₅), temperature (°C), dissolved oxygen, pH, and electrical conductivity were measured. Water quality was determined according to the Surface Water Quality Regulation (SWQR) and Water Quality Index (WQI). The water quality classes of the stream, based on epilithic diatom assemblages, were determined using the Generic Diatom Index (GDI), Saprobi Index (SI), Trophic Index (TI), Swiss Diatom Index (DI-CH), and Trophic Diatom Index (TDI). According to SWQR, the average values of the parameters at all sites were generally in the class I or II (high quality or lightly polluted water). WQI, was calculated based on seasonal and site and all results were determined as “excellent water”. 117 taxa belonging to 51 genera of epilithic diatoms were observed in the Köprüçay River. According to epilithic diatoms, generally all sites were in the range of very slightly polluted or partially polluted (I and II) water quality classes.

Periphyton plays a critical role in the progress of the regime shift between macrophytes and phytoplankton in shallow lakes, since its overgrowth could trigger metaphytic blooms and lead to the collapse of submerged macrophytes. Understanding the mechanisms of metaphytic blooms and the subsequent prediction are important for lake managers to prevent ecological disaster. In this study, a one-year field survey on periphyton was conducted in Lake Ulansuhai to explore the driving factors of metaphytic blooms. The result revealed that the filamentous chlorophyta Mougeotia was identified as the key genus involved in metaphytic blooms. Structural Equation Modeling showed that Mougeotia biomass was positively correlated with total nitrogen, temperature, and submerged vegetation density. While phytoplankton biomass was primarily positively correlated with total phosphorus and temperature. A logistic regression model indicated that when the biomass of Mougeotia reached 1.78 g m⁻² (95% CI 1.08–3.03 g m⁻²), the probability of metaphytic blooms exceeded 50%. These findings suggested that both nitrogen and phosphorus drive the regime shift, and a dual-nutrient-reduction strategy should be implemented during this hysteresis phase. Additionally, the biomass of submerged vegetation and water depth influence Mougeotia biomass. Therefore, controlling submerged vegetation and managing water levels are crucial in-lake strategies for mitigating metaphytic blooms.

To investigate effects of rice-fish co-culture (RF) models on sediment heavy metals, nutrients, and bacterial communities, a field experiment was conducted with four RF models (varying fish densities and rice varieties), rice monoculture (RM), traditional aquaculture pond (TAP), and lotus-fish co-culture (LFS). The results indicated that the study area had moderate heavy metal pollution risk (mainly Cd). Fish density in RF but not sedimental heavy metal contents significantly influenced sedimental heavy metals release. Low fish density significantly increased sedimental Cd release and facultatively anaerobic bacteria, while reducing As release. TAP exhibited significantly higher sedimental heavy metal contents (Cu, Zn, Cr, As), sedimental release of heavy metals (Cd, Pb, As) and nutrients (total nitrogen, total phosphorus, ammonia), pathogenic bacteria, and lower bacterial diversity than RF. Spearman’s correlation analysis revealed that sedimental iron-manganese oxide, pH, and organic matters were key factors affecting the sedimental release of heavy metals, particularly Cd and As. Mantel tests showed that sediment nitrogen, phosphorus, As, and Pb were critical factors shaping bacterial community structures. This study highlights RF can reduce heavy metal pollution risks and improve bacterial communities, making it a green and sustainable farming approach. Optimizing fish densities is crucial for its green development.