Aquatic Sciences最新文献

Amazonian floodplains exhibit complex hydrological patterns, with flood pulses causing large seasonal fluctuations in water level and hydrodynamics. Research on flooding dynamics in tropical floodplains has revealed a substantial impact on plankton community structure. Our field study focused on the Curuai floodplain, a tropical system within the Amazon Basin in northern Brazil. We conducted parallel transects sampling across seven lakes of the floodplain during both rising and falling water periods. The objective is to quantify carbon biomass partition among bacterioplankton, phytoplankton, and zooplankton and to understand how hydrological changes influence plankton communities and their interactions. Phytoplankton accounted for the largest fraction of the plankton carbon (> 70%), followed by zooplankton (≈16%), with bacteria contributing the least to the total carbon pool (< 10%). Hydrological variations significantly altered the structure and interactions of plankton communities. During the rising water period, increased water transparency led to higher amounts of bacteria, cryptophytes, and a greater contribution of cladocerans to the zooplankton carbon stock. The greater crustacean zooplankton biomass during the flood coincided with a lower phytoplankton biomass, including cyanobacteria. Bacterial production seemed to sustain a microbial loop that was relatively independent from the classical food web, and microorganisms were likely a carbon sink during the rising water. The falling water period was marked by a more productive environment, characterized by higher nutrient levels (total nitrogen: 240.0–700.0 µg L⁻¹), organic carbon (0.7–12.0 mg L⁻¹), and temperatures (29.9–34.9 °C), which influenced community structure and plankton interactions. Rotifers experienced a significant biomass increase, ranging from 103.4 µg C L⁻¹ during the rising water period to 290.0 µg C L⁻¹ during the falling water period, and the biomass ratio between rotifers and bacteria rose from 0.5 to 5.4, on average. Copepods also exerted a greater impact on bacterioplankton during this period. Cyanobacteria’s relative contribution doubled during the falling water period, constituting, on average, 42% of the phytoplankton carbon biomass and predominantly consisting of potentially toxic species. This likely disrupted the phytoplankton–zooplankton relationships, and the high primary productivity most likely flowed mainly through microbial pathways in the studied Amazonian floodplain system.

Multiple anthropogenic pressures often interact to significantly impact riverine biodiversity. However, the understanding of these pressures and their effects at the basin scale across different elevation gradients remains limited. Here, we assessed the impact of land use, river barriers, and their overall effect on the taxonomic and functional diversity of macroinvertebrates at three basins at different elevations. The results reveal that multiple pressures dominated the additive effect on the basin scale for macroinvertebrate diversity, and the nonadditive interaction of pressures shifted from antagonistic to synergistic effects from high to low elevation. These pressures shaped macroinvertebrate taxonomic and functional diversity patterns, with midelevation sites exhibiting higher taxonomic and functional diversity (i.e., Shannon–Wiener and functional richness) compared with both low and high elevations. However, the functional evenness showed no significant difference across basins. Specifically, functional redundancy was significantly higher in the high- and low-elevation basins compared with the mid-elevation basin. For functional traits, a significant shift of multiple voltinism, larger body sizes, asexual reproduction or ovoviviparity, nonstreamlined body shapes, and a reduction in external egg-laying (e.g., clutches and terrestrial) were observed along with the elevation gradient and anthropogenic pressures. The results reflected the directional selection process of macroinvertebrate trait composition under the combined influence of different anthropogenic pressures associated with elevation. These findings emphasize the significance of conducting thorough assessments of anthropogenic disturbance characteristics at the basin scale. Such assessments can enhance our understanding of the spatial dynamics of multiple pressures on biological communities, thereby facilitating the development of effective ecological management strategies in the future.

Long-term results allowed the impact of two invasive species, roach and the zebra mussel, on pelagic zooplankton species abundance in Lower Lough Erne, Northern Ireland, to be established. The main observed change was an average sixfold reduction in the annual mean densities of total larger Rotifera, Cyclops strenuus, Eudiaptomus gracilis, total larger nauplii and Diaphanosoma brachyurum over the period 1987–1994. The densities of these taxa remained low thereafter, and the densities of four other taxa (Daphnia, Bosmina longirostris, Bythotrephes longimanus and Mysis relicta) were low throughout the period 1987–2013. The main changes in the lake properties were related to fish, and predation by roach was shown to be the main cause of the decrease in zooplankton abundance, with the possibility that perch also contributed to this. Predation by larval, juvenile and larger roach and perch on zooplankton is supported by the collation of fish diet results from the literature. The lack of a measurable impact of the zebra mussel on zooplankton abundance due to the latter’s already low abundance is an example of an antagonistic effect of two invasive species.

The southwestern (SW) Atlantic is bordered by the coastlines of Brazil, Uruguay, and Argentina and is characterized by a great diversity of ecosystems, in which estuarine and marine molluscs are among the most representative invertebrates. The accelerating degradation of the environment due to human activity is resulting in the loss of species, leaving us insufficient time to comprehensively understand their morphology, ecological interactions, and the ecosystem services they provide. The aim of this manuscript is to review the conservation status of estuarine and marine molluscs in the SW Atlantic, identify the main threats and knowledge gaps, and indicate the challenges and prospects for their conservation. Physical degradation of environments, pollution, exotic species, and overexploitation of fishery resources are among the main non-climatic drivers threatening marine molluscs in the SW Atlantic. In addition, climate threats, such as rising temperatures and sea levels, and ocean acidification, create synergistic effects that are still not fully understood. Given this scenario, it is imperative to implement measures to mitigate this situation. These measures include strengthening management and governance to conserve habitats and control pollution and non-native species, with the aim of reducing ecosystem deterioration and establishing the foundations for monitoring environmental changes through long-term interdisciplinary projects. Additionally, there is a need to improve legislation aimed at regulating fishery practices. To achieve the effective conservation of estuarine and marine molluscs in the SW Atlantic, it is also essential to strengthen scientific dissemination projects and expand and support the training of researchers specialized in molluscs.

The trophic structure of the fish assemblage in the Volta Grande reach of the Xingu River, Brazil, was investigated 4 years after the Belo Monte Hydroelectric Power Plant, which has reduced flows in the reach, commenced operation. Fishes were surveyed during four phases of the annual hydrological cycle. We used stable isotope analysis of carbon and nitrogen to infer variation in fish trophic ecology and the contributions of basal producers to fish biomass. We observed that hydrological variation was associated with subtle changes in the isotopic composition of fishes and aquatic and terrestrial sources of basal production. The sizes of the isotopic spaces occupied by fish trophic guilds differed among hydrologic phases, as did the isotopic overlap among trophic guilds. Recent reductions in the magnitude and duration of the annual flood pulse and lateral habitat connectivity have apparently reduced the availability of certain food sources, including allochthonous resources that are seasonally available in floodplain habitats. Given that many fish species inhabit the middle Xingu River, recent changes to its flow regime and ecological dynamics will have long-term consequences for the conservation of its biodiversity, as well as fisheries production, which are important for local food security and livelihoods.

Since 1970, approximately 83% of global freshwater species have declined, particularly in neotropical regions, highlighting the urgent need for conservation efforts in these ecosystems. This study investigates the factors shaping the taxonomic and functional diversity of macroinvertebrate communities in the Middle Paraná River, Argentina, a minimally regulated area, offering a unique opportunity to examine biodiversity alongside river ecosystem interactions. Our study examines the complex ecosystem of the Middle Paraná River, characterized by hydromorphological interactions between main waters, secondary channels, and lakes across its extensive floodplains. We analyzed data from 166 sites, identifying 160 species of benthic invertebrates. Spatial and environmental variables were assessed to characterize ecological conditions (e.g., patch type, habitat connectivity and shape, hydrometric phase, depth, granulometry, and conductivity) and to disentangle their influence on biotic patterns through variation partitioning analysis. The species composition, taxonomic, and functional beta diversity of the communities were assessed. The taxonomic diversity of invertebrates was influenced by spatial and niche-based factors, depending on their dispersal mode. While the longitudinal dimension was important, smaller-scale variations, especially lateral ones, played a crucial role in community diversity, aligning with flood pulse and flow pulse theories. Functional diversity was influenced by mesohabitat and microhabitat scales rather than along the longitudinal dimension, suggesting that lateral variability might impact detritivore diversity. Food sources were not restrictive, allowing detritivores to thrive during normal hydrometric levels, with high beta diversity and functional redundancy. The heterogeneity of the river-floodplain system boosted species turnover and high coexistence, preventing species dominance and benefiting detritivores, resulting in high local diversity and significant functional redundancy. These findings suggest that a dispersal group-based approach improves the understanding of community patterns and can be useful for monitoring, conservation, and restoration strategies in riverine ecosystems.

Aquatic biodiversity is rapidly declining owing to global climate change, increasing anthropogenic activities, and species invasions. The Batanghari River, one of the Indonesia’s longest rivers, faces severe pressure from illegal gold mining, industrial pollution, and domestic waste. Despite evidence of biodiversity loss, a comprehensive assessment has yet to be undertaken. This study used eDNA metabarcoding, targeting the mitochondrial cytochrome c oxidase I (co1) gene fragment, to analyze the diversity of aquatic biota in Batanghari River. Environmental DNA (eDNA) metabarcoding, as used in this study, offers broader insights compared with traditional methods by enabling the detection of a wider range of species, including those that are rare, cryptic, or difficult to capture. A total of 22,180,436 reads were generated from five river watersheds. Approximately 80% of reads were classified to the species level (72.5–100% of identical matches), with the remainder identified as unidentified taxa. Significant differences in species richness and community composition were observed between upstream and downstream areas. Taxonomic richness was highest at Batanghari Hulu, the most upstream site, with 9161 amplicon sequence variants (ASVs), including 5773 Chordata, 1755 Arthropoda, and 433 Mollusca. In contrast, downstream locations such as Batanghari Hilir exhibited lower richness, with 3888 ASVs, including 2681 Chordata, 651 Arthropoda, and 224 Mollusca. These differences are likely influenced by increasing anthropogenic stressors downstream. Furthermore, beta diversity analysis showed significant variation in taxonomic composition among sampling locations (permutational multivariate analysis of variance, PERMANOVA, p < 0.05). Additionally, several extinct or endangered species were detected at multiple sites, as confirmed by our previous work. This study highlights the critical role of eDNA metabarcoding in assessing biodiversity, providing valuable insights for conservation and management efforts aimed at protecting the Batanghari River ecosystem.

It has been proposed that light-limited lakes are characterized by the constraint of the autotrophic pelagic flux (the green pathway) and by the dominance of the detritus-based heterotrophic flux (the brown pathway). However, studies explicitly testing this assumption are scarce in natural food webs. Here, we estimated energy flux in a dystrophic light-limited shallow lagoon to investigate the importance of green vs. brown energy pathways to fuel the freshwater fish food web. Over the course of 1 year, we estimated the energy flux intake for five fish trophic guilds (detritivores, top carnivores, meso-carnivores, herbivores, and omnivores) monthly. We found a high concentration of energy flux in the detritivore compartment, accounting for > 93% of the total energy flux through the food web. A single detritivore species (Cyphocharax voga) dominated the fish community in terms of biomass stock and number of individuals. There was a substantial increase in the detritivore energy flux during warm months. These results illustrate a remarkable dominance of brown pathways, which support the fish trophic energy flux in this kind of system. The flux magnitude was related to temperature, highlighting the synergy between warming and brown pathways.

Marine Protected Areas (MPAs) are central to Africa’s efforts to conserve marine biodiversity and support sustainable development. This study adopts a scoping review approach, systematically identifying, appraising, and synthesizing relevant literature to inform decision-making. While it focuses primarily on Eastern Africa, the review incorporates insights from other African regions to provide a broader, continent-wide perspective. Through an in-depth examination of scholarly research and practical case studies, the study highlights key findings, persistent challenges, and future directions for enhancing MPA effectiveness. Emphasis is placed on the importance of innovative financing, robust governance, and international collaboration in advancing MPA outcomes. The review also explores the integration of socioeconomic dimensions, indigenous knowledge, and climate change adaptation strategies into MPA planning and management. Region-specific issues—including governance limitations, funding gaps, and the impacts of climate change—are critically examined. The study advocates for continuous research and adaptive management that leverages emerging scientific insights to address evolving threats. The conclusion synthesizes core findings, discusses their policy and practical implications, and proposes pathways for future research and strategic development. Ultimately, this review provides a comprehensive and evidence-based overview of the current status and future potential of MPAs in Africa.

Freshwater ecosystems are highly dynamic environments where plankton communities are essential indicators of ecological health and function. This study investigated the seasonal and spatial dynamics of phytoplankton and zooplankton communities in Juam Lake, a significant reservoir in South Korea, across multiple sampling periods (spring and autumn 2021–2022). Physicochemical parameters, including water temperature, dissolved oxygen, and nutrient concentrations, exhibited distinct seasonal patterns, ranging from 13–15 °C in spring to 26–27 °C in autumn. Amplicon sequence variant (ASV) analysis revealed clear seasonal succession in dominant plankton groups. Phytoplankton communities shifted from Chlorophyta dominance in spring 2021 to Cryptophyceae prominence in spring 2022, while Bacillariophyceae and Chrysophyceae increased in autumn 2022. Zooplankton communities displayed alternating dominance patterns, with rotifers prevalent in spring seasons and Copepoda dominating autumn samples. Multivariate analysis demonstrated that water temperature (p < 0.0001) and dissolved oxygen (p = 0.001) strongly influenced community structure, while water depth was not a significant factor (p = 0.73). Alpha diversity indices revealed higher diversity metrics in middle and outflow sites, with benthic zones consistently exhibiting the highest Shannon diversity for both plankton groups. Correlation analysis identified key indicator taxa with distinct environmental preferences, such as Stephanodiscus showing strong negative relationships with water temperature (−0.66) and total organic carbon (−0.70), while Trichocerca displayed positive correlations with water temperature (0.55). The sampling investigation of the plankton community in Juam Lake using eDNA provides valuable insights into the complex spatiotemporal dynamics, and highlights that seasonality is more important than spatial factors (flow point and water depth) in structuring these aquatic communities in a controlled Juam Lake. In particular, the absence of spatial differences following water depth in shallow lakes may be reflected in establishing more efficient lake sampling plans in the future.