Aquatic Ecology最新文献

Neotropic cormorants are abundant piscivorous birds in southern Brazil and present challenges for fisheries and aquaculture as potential food competitors. To evaluate this interaction, we address the species trophic overlap with artisanal fisheries in a productive estuary in southern Brazil (48°45’27’’S, 28°30’23’’W) with abundance data, pellet samples, taxonomic composition and fishery production during July 2021 until May 2023. Bird abundance showed a seasonal pattern with peaks during autumn-winter and a population decrease during spring-summer, primarily due to the migration of reproductive individuals and the establishment of a colony from March to September. Pellet analysis identified 31 prey types within 17 taxonomical families, most of which were fish from the Ariidae (35.9%), Engraulidae (15.6%), Scianidae (12.8%), Mugilidae (10.3%), and Gerreidae (10.1%) families. We characterized the cormorant population as opportunistic, as temporal variation and Amundsen’s analysis indicated the consumption of available and diverse resources. Through otolith-total length allometric regressions we estimated a mean fish biomass per pellet of 382.7g and prey size ranging from 26.6mm to 326.9mm. When compared to artisanal fisheries, cormorants consumed 12% the amount of fish exploited by artisanal fisheries during the sampling period, although the Pianka’s index of 0.78 indicated a high overlapping food resource. Cormorant predation on juvenile fishes likely plays an important ecological role at Laguna Estuarine System by regulating abundant prey species through density-dependent mechanisms. This study provides new and updated information on cormorant population, diet and interactions with artisanal fisheries of southern Brazil.

Submerged macrophytes constitute an integral component of primary production in shallow lake ecosystems and play a crucial role in maintain ecosystem structure and function. Compared with extensively studied large plateau lakes, small shallow plateau lakes are more numerous and ecologically fragile, yet their submerged macrophyte communities and macrophyte–environmental factor interactions remain poorly understood. In this study, Jianhu Lake, a representative small shallow plateau lake in Yunnan Province, China, was systematically investigated through four seasonal surveys conducted at 30 sampling sites from July 2021 to May 2022 to elucidate the spatiotemporal distribution patterns of submerged macrophyte communities and their relationships with environmental factors. Four submerged macrophyte species—Ceratophyllum demersum, Hydrilla verticillata, Potamogeton malaianus, and Ottelia acuminata—were recorded in Jianhu Lake and were mainly distributed in nearshore areas. Temporally, submerged macrophyte biomass and diversity were significantly higher in summer and autumn than in spring and winter (p < 0.05). Canonical correspondence analysis and partial least squares structural equation modeling revealed that water depth, phosphorus concentration, and phytoplankton abundance were the key environmental drivers influencing submerged macrophyte biomass and diversity, thereby directly or indirectly shaping their spatiotemporal distribution. Overall, this study highlights water depth and phosphorus concentration as the primary drivers influencing the spatiotemporal dynamics of submerged macrophyte communities in small shallow plateau lakes, providing important scientific evidence for understanding and conserving these widespread yet vulnerable lacustrine ecosystems.

Phytoplankton biomarkers and functional group composition were characterized for the first time in the coral reef lagoons and adjacent open waters of the Lakshadweep Archipelago (LDA) during the winter monsoon of 2022, using a HPLC-CHEMTAX approach. The study area was characterized by warm (>29 °C), oligotrophic surface waters throughout sampling period. Although chlorophyll a concentrations were uniformly low (mean 0.06 ± 0.05 mg m⁻³) with minimal spatial variability, the distribution of diagnostic pigments and corresponding phytoplankton functional groups (PFGs) exhibited distinct lagoon-specific signatures. Among the detected biomarkers, zeaxanthin, DV chlorophyll a and peridinin, were most prominent, albeit in low concentrations, indicating the relative dominance of cyanobacteria (Synechococcus and Prochlorococcus) and dinoflagellates, respectively. CHEMTAX-derived outputs provided the major PFGs and their proportional chl a contributions. The occasional presence of fucoxanthin, particularly in the Kavaratti, Bangaram and Agatti lagoons, suggested a sporadic occurence of diatoms. In contrast, cyanobacterial populations dominated the open waters and the Perumal Par lagoon, supported by both Synechococcus and Prochlorococcus. Photopigment-based indices, particularly PPC_TP and PSC_TP ratios, indicated an overarching dominance of smaller phytoplankton (<2 µm) consistent with the oligotrophic nature of the lagoons. However, a marked increase in PSC_TP in the Kavaratti lagoon signaled a shift toward moderate productivity, likely associated with higher abundance of larger phytoplankton, predominantly autotrophic dinoflagellates and diatoms, and increased nutrient inputs, potentially reflecting rising anthropogenic pressures within in the lagoon.

Anammox bacteria play an important role in the nitrogen cycle within freshwater ecosystems. However, it is not yet known how their communities in floodplain lakes respond to hydrological regime changes. This research focused on the surface sediments of Poyang Lake, China’s largest floodplain lake. We employed high-throughput sequencing and quantitative polymerase chain reaction (qPCR) methods to analyze the variations in the alpha diversity, abundance, community structure, and co-occurrence network of anammox bacteria in different hydrological regimes (wet, normal, and dry phases). The results showed that there were no significant differences in the alpha diversity indices (except for the Chao richness estimator) among hydrological phases. The abundance and community structure of anammox bacteria varied significantly across hydrological regimes. In the dry phase, the average abundance of anammox bacteria decreased by 68.1% and 66.6% compared to the wet and normal phases, respectively. Among the 34 main operational taxonomic units (OTUs) of the anammox bacterial communities, 26 OTUs showed significant differences in the relative abundance between different hydrological regimes. Co-occurrence network analysis revealed that the internal connections among anammox bacterial species were the closest in the dry phase, followed by the wet phase, and the weakest in the normal phase. Total nitrogen, total phosphorus, and organic matter were the primary environmental factors influencing the abundance and community structure of anammox bacteria. This study enhances our understanding of the ecological impacts of the hydrological regime and the anammox process in floodplain lakes.

Biological indicators, such as phytoplankton, are crucial in monitoring changes in freshwater ecosystems as these are directly affected by nutrient concentration which helps to regulate their growth and development. Phytoplankton can serve as a biomonitoring tool because the phytoplanktonic species present in the diet can be used as bioindicator. This study aims to evaluate the use of phytoplankton and fish diet as bioindicators of river health in two important rivers, Narayani and East Rapti, of Nepal. The impact of water quality on phytoplankton, both in habitat and in the fish diet, was also assessed. Phytoplankton, fish gut and water samples were collected from 27 sites including the main river and its major tributaries. The correlational analysis and multiple linear regression determined the relationship between physico-chemical parameters and phytoplanktonic species in habitat. Twenty-one phytoplanktonic species were recorded from different habitats and 25 species from the fish diet. Spirogyra sp. was the dominant taxa in both habitat and the fish diet. Whereas Ulothrix sp. was the second most preferred food item for fish. Varied food items were recorded in Channa punctata, Pethia conchonius, Opsarius bendelisis and Acanthocobitis botia and limited food items were recorded in Chitala chitala, Garra annandalei, Puntius terio, Cabdio jaya, Tor mosal, Pseudambassis baculis, Botia lohachata, Botia histrionica, Salmostoma acinaces, Bangana dero, Botia geto, Aorichthys seenghala, and Anabas cobojius. Phytoplankton in habitat was positively related with temperature, EC, TDS, chloride, alkalinity, total hardness, calcium hardness, magnesium hardness, free CO_2, NO₃⁻, K⁺, Ca²⁺, Mg²⁺, and Na⁺ had negative relationship with DO, pH, PO₄³⁻, and NH₃. Sites with dense settlement and industrialized areas had more pollutant tolerant phytoplanktonic species both in habitat and fish diet which indicates an influence of pollution in aquatic biota. Temporal monitoring of aquatic biota is recommended to track changes in river health of both Narayani and East Rapti rivers.

Freshwater ecosystems on tropical islands host unique and functionally important fish communities increasingly threatened by habitat degradation, exotic species, and climate change. Monitoring these systems is challenging due to steep topography, difficult access, and the vulnerability of insular environments. Environmental DNA (eDNA) metabarcoding offers a standardized, non-invasive solution for biodiversity assessment. Here, we applied eDNA metabarcoding with high-throughput sequencing to characterize freshwater fish communities on two contrasting islands in the western Indian Ocean: Mayotte and La Réunion. Four watersheds per island were sampled during two transitional hydrological periods to evaluate inter- and intra-island variability and temporal stability. In total, 49 fish species were detected, spanning freshwater, diadromous, and marine-associated taxa, only eight species were shared between islands, revealing strong biogeographic differentiation. Mayotte was dominated by marine-associated taxa (50%), whereas La Réunion hosted more diadromous (44%) and exotic species (26%) and displayed greater functional richness (FRic = 7.2). Functional traits revealed contrasting ecological strategies: communities in La Réunion showed broad trophic diversity and high trait dispersion, while those in Mayotte were dominated by a few predator species, indicating reduced redundancy and resilience. Spatial structuring was significant in La Réunion, following an upstream–downstream gradient, but absent in Mayotte. No significant temporal variation was observed between sampling campaigns, underscoring the temporal robustness of eDNA detections. Overall, eDNA metabarcoding effectively captured both taxonomic and functional biodiversity patterns, demonstrating its value as a reliable and reproducible tool for standardized biomonitoring and conservation of tropical freshwater ecosystems.

Seagrasses provide habitat for feeding and spawning for many invertebrates, and act as a refuge from predators. This study documented the changes in invertebrate abundance in response to the trimming of seagrass blades to half height in Thalassia testudinum patches in Santa Rosa Sound, Pensacola Beach, Florida, USA. Short-seagrass plots had a reduced abundance when compared to untrimmed plots. Bittiolum varium (gastropod) and Hippolyte sp. (caridean shrimp) had the highest abundances, while Tozeuma carolinense (caridean shrimp) and polychaetes had the lowest abundances. In the laboratory, Hippolyte and Penaeus shrimps were placed in a mesocosm containing artificial seagrass to explore habitat choice based on seagrass length (long, short, or bare sand). Whether in mixed genera or solo groups, the overwhelming choice for both genera was long seagrass with no indication of agonistic interactions between the genera.

The Ross Sea is one of the most biologically productive regions in the Antarctic Ocean, characterized by predictable phytoplankton blooms. However, the northwestern Ross Sea remains a poorly studied area within this system, leaving significant gaps in understanding the environmental drivers regulating phytoplankton dynamics. The two dominant phytoplankton taxa in this region, diatoms and Phaeocystis antarctica, exhibit spatiotemporal variability in dominance, yet the factors influencing their distribution in this understudied area are not well constrained. This study investigated spatiotemporal distribution of diatoms and P. antarctica using high-performance liquid chromatography (HPLC) pigment analysis and identified key environmental factors influencing their composition in the northwestern Ross Sea during the summers of 2018 and 2019. In 2018, phytoplankton were predominantly composed of diatoms (66.6 ± 26.6%) and P. antarctica (30.2 ± 27.3%). Diatom dominance was negatively correlated with SiO₂ and dissolved inorganic nitrogen (DIN) concentrations, whereas P. antarctica dominated in areas with relatively deeper mixed layer depths (123.7 ± 41.5 m). In 2019, phytoplankton assemblage was more diverse, consisting of diatoms (48.0 ± 17.7%), P. antarctica (35.6 ± 18.2%), chlorophytes (7.7 ± 10.9%) formed the primary assemblages. Principal component analysis (PCA) suggested that P. antarctica played a significant role in nutrient depletion. Contrary to previous studies, P. antarctica was abundant even where the mixed layers were shallower than the euphotic depth, indicating a more complex relationship between phytoplankton composition and physical oceanographic conditions. Chlorophytes exhibited a distinct association with coastal melt water, contributing up to 45.9% of the phytoplankton in these areas. The strong correlation between chlorophytes and melting water suggests their introduction through sea ice melt, potentially influencing the phytoplankton structure under changing environmental conditions. These findings highlight the interactive effects of environmental variables on phytoplankton composition, emphasizing the importance for continued research on ice associated-shifts in species assemblages under ongoing environmental changes.

In sea urchins, lipofuscin-like pigments (LLPs) occasionally present in the gonads have been associated with the natural process of gametogenesis and environmental stress (such as marine pollution). For this reason, they have been used as biomarkers to assess animal health status. In this study, we analyzed 90 specimens of Echinometra lucunter sampled during summer 2023 on two beaches located on the tropical coast of Brazil (Paraíba state, 7°S). The gonads of all specimens were extracted for histological routine. Histological analyses revealed that 58.8% of the organisms contained LLPs in their gonadal tissue. Males and females presented similar mean prevalences of LLPs (73–76%) at Praia do Cabo Branco, and males had a much higher prevalence than females at Praia de Tambaba (68 and 33.4%, respectively). Despite having controversial causes, changes like this can be harmful to the reproduction of these organisms. Thus, this study presents a descriptive and initial characterization of these pigments in the gonadal tissue of males and females for populations in the Western Atlantic, in addition it is the first record of this alteration in Echinometra lucunter, reinforcing the importance of further monitoring and analysis of the populations.

Effective solid waste management (SWM) remains a major environmental and public-health challenge, particularly for freshwater shoreline communities. This study conducted a lake-proximal, mixed-methods assessment of households’ SWM practices along Lake Volta across 16 communities. A paper-based, interviewer-administered household survey was complemented by key-informant interviews and field observations. In total, 320 households and 36 informants participated. Awareness of improper waste management impacts was high (90.6%), yet only 40.0% of the respondents were familiar with waste segregation, and 26.2% were aware of e-waste. Household waste analysis revealed that 57.5% of the households primarily generated organic waste, while 40.0% were dominated by plastic waste. Only 1.5% of households predominantly produced wood or paper waste. Overall, waste disposal practices were poor, only 1.6% of households used dustbins, whereas 51.9% disposed of waste by dumping it near their homes. Although Dambai, one of the study sites, operated a composting facility that recycled household waste, most communities relied on open dumping, with burning at disposal site remaining common. Environmental Health Officers identified inadequate funding, outdated equipment and limited enforcement authority as major constraints. The findings provide actionable, location-specific insights: promoting decentralized treatment of organic waste in areas where it prevails, targeted plastic recovery and improved waste container access around markets, and strengthened school and community sensitization campaigns on waste management and waste segregation. Enhancing institutional coordination and optimizing resources could advance sustainable SWM and support the achievement of Sustainable Development Goals 3 and 6—on Good Health and Well-being and Clean Water and Sanitation—around Lake Volta.