Aquatic Ecology最新文献

Studies performed in Valle de Bravo (VB) reservoir in Mexico record the presence of cyanobacteria proliferation and microcystin LR (MC-LR), both from 1998 to 2022, related mainly to two environmental factors; first, nitrates (NO₃) and second, temperature. We statistically analyzed data from nine selected works in VB and found that these parameters do not converge seasonally during stratification and mixing. We propose that cyanobacteria, being photoautotrophic organisms, their proliferation and toxin-producing capacity are mainly determined by the amount of photosynthetically active radiation (PAR) rather than NO₃. We conducted experimental tests to evaluate the toxic wild cyanobacterium, Microcystis aeruginosa, producer of microcystin LR (MC-LR), exposed to 100 µmol photons m⁻² s⁻¹ of PAR and three fractions at different descending concentrations of NO₃. The results of the analyses on data from nine studies showed that cyanobacteria did not proliferate due to the seasonal availability of NO₃ but rather due to temperature. In vitro, we observed that increased PAR had an effect on the growth of M. aeruginosa. The presence of MC-LR was driven by the inverse relationship between PAR and NO₃. Therefore, we conclude that adding PAR monitoring to studies of tropical monomictic systems would contribute to expanding our understanding of NO₃ and temperature-related effects on the proliferation of cyanobacteria and their toxins.

The diet of the smooth-coated otter (Lutrogale perspicillata) was assessed in a representative agro-ecosystem complex called “Khazan Lands”, situated within the human-dominated estuarine landscape of the Zuari River of Goa, India. This was achieved by analyzing undigested prey remains from 815 fecal (spraint) samples. Overall, fish dominated otter diet (Percentage Biomass, BIO% = 59%; Relative Frequency of Occurrence, RFO% = 49%), followed by shrimp (BIO% = 37%; RFO% = 42%) and crabs (BIO% = 3%; RFO% = 8%). Other prey groups, including insects, molluscs, amphibians, birds, and mammals, were present in minor quantities (BIO% =  < 1%; RFO% = 2%). Shrimp consumption was dominant during the winter (BIO% = 80%; RFO% = 58%) and pre-monsoon seasons (BIO% = 56%; RFO% = 54%), whereas fish dominated during the monsoon (BIO% = 90%; RFO% = 63%) and post-monsoon seasons (BIO% = 79%; RFO% = 56%). 22 fish families were recorded in the diet of the species, with Cichlidae dominating throughout the year (seasonal RFO% = 32–45%). Otters largely consumed small and medium sized fish (< 200 mm) (seasonal RFO% = 81–87%), whereas larger fish (> 200 mm) were consumed less frequently (seasonal RFO% = 13–19%). The composition of economically significant prey (fish, shrimp, and crabs) was high (RFO% = 97%), whereas that of economically insignificant prey (molluscs, birds, amphibians, insects, and mammals) was low (RFO% = 3%). Furthermore, the occurrence of high-value fish families was marginally higher (seasonal RFO% = 50–62%) than low-value families (seasonal RFO% = 38–50%). Our observations suggest an opportunistic feeding habit by the species and a considerable overlap between resources exploited by fisherfolk and L. perspicillata. This study highlights the adaptability of this species, and the importance of Khazans for otter populations in the unprotected, human-dominated estuarine landscapes of Goa, India.

Aquatic macrophytes constitute a crucial foundation for sustaining the diversity of lake ecosystems. In particular, the carbon isotopes of their cellulose (δ¹³C_cell) represent an essential technical approach for investigating lake carbon cycles and variations in primary productivity. Undertaking research on the distribution characteristics of δ¹³C_cell in aquatic macrophytes and their environmental implications is of considerable significance for comprehending regional lake environmental changes and carbon cycling processes. In this study, Lake Shengjin, a national nature reserve wetland, was selected as the research area. Through integrated field surveys, isotopic analyses, and multivariate statistical modeling (one-way ANOVA, Pearson correlation analysis), this study systematically investigates the δ¹³C_cell distributions in modern aquatic macrophytes and elucidates their environmental drivers. These findings revealed that the δ¹³C_cell of emergent and floating-leaved plants exhibited enrichment with ¹²C, which is indicative of a C3 photosynthetic pathway. In contrast, the δ¹³C_cell of submerged plants displayed enrichment with ¹³C, suggesting the potential involvement of the carbon concentrating mechanisms in their photosynthetic processes. The results of the correlation study indicated that the pH of the water body was the mainly environmental factor influencing the changes in the δ¹³C_cell of aquatic macrophytes in the study area (p < 0.01). This finding was consistent with the results of previous research conducted in the eastern plain lake district and in other regions abroad. This study can offer insights into understanding the distribution characteristics of δ¹³C_cell in aquatic macrophytes of lakes in the middle and lower reaches of the Yangtze River and their environmental implications.

Thallium (Tl) contamination in freshwater ecosystems posed significant risks to microbial communities and ecosystem functions. This study investigated the effects of Tl pollution on microbial diversity and carbon, nitrogen and sulfur cycling, focusing on microbial responses to varying Tl concentrations. Microbial community composition was altered by Tl, with archaea exhibiting higher resistance than bacteria. Low Tl concentrations had more complex impacts on microbial functions, particularly affecting carbon fixation, denitrification, and sulfate reduction pathways. Our findings highlighted the role of specific microbial functional genes and metabolic pathways in mitigating metal toxicity, with sulfate-reducing bacteria (SRB) showing potential for Tl precipitation and environmental recovery. The study provided new insights into microbial resilience under Tl stress and offered perspectives for ecological restoration in Tl-impacted ecosystems.

Scleractinian corals host a diverse range of symbiotic organisms, including crabs of the family Trapeziidae, which play a key role in coral protection and maintenance. These crabs show a positive size-correlation with their host coral colonies, which may result either from host selection in migrating crabs (“migrants” hypothesis) or growth constraints imposed by long-term residency (“residents” hypothesis). In this study, we investigated the abundance, size, sex ratio, host use, and fecundity of Trapezia septata in 9 month-old nursery-reared coral colonies of Pocillopora verrucosa at the coast of Tre Island (Vietnam), and compared the results with earlier growth stages to assess which hypothesis better explains the observed crab-host size relationship. Prevalence of T. septata in corals was high (88.4%) and increased with colony size for adults, while remained low (16.2%) and size-independent for juveniles. Sex ratio varied with colony size, with males and females predominating respectively in smaller and larger colonies. Crab size correlated with colony size in specific groups, particularly for male–female pairs, while solitary crabs and those in larger groups showed weak or no correlations. Fecundity was higher in crabs whose size correlated with colony size. In conclusion, we have identified two groups for T. septata, “migrants”—small individuals—and “residents”—large mature individuals in pairs. Both groups differ in behavior, size, and functional characteristics, offering new insights into the population structure and host-use patterns. However, the role of these groups in shaping population spatial structure remains unclear due to the limited data on crab growth rates and lifespan and requires further investigations.

Benthic macroinvertebrate communities in riverine ecosystems are shaped by both local conditions and processes that occur at larger spatial scales. Most models of riverine community structure are grouped into either discrete or continuum conceptual models. However, there is much uncertainty in how these two classes of conceptual models apply to macroinvertebrate communities in the physicochemically consistent headwaters of spring-influenced rivers. We examined benthic macroinvertebrate community composition and biomass among local discrete geomorphic mesohabitats (riffles, runs, and pools) and along an upstream to downstream gradient in two spring-fed rivers in central Texas. We found that longitudinal distance from the spring source in the San Marcos River and mesohabitat conditions in the Comal River played a greater role in shaping taxonomic composition. Taxonomic richness did not vary with distance from springhead but was consistently lower in pool mesohabitats when compared to runs and riffles in both rivers. Compositional changes and patterns in beta diversity within mesohabitat types among study reaches indicated that replacement rather than richness differences was the main mechanism leading to patterns of beta diversity. We also found that a non-native snail (Tarebia) constituted the largest proportion of benthic macroinvertebrate density and biomass in several study reaches downstream from springheads in both rivers.

This study investigated the impacts of short-term (4 months) and long-term (8 months) drought on benthic macroinvertebrate (BMI) communities in wetland mesocosms, focusing on community composition, functional diversity, and resilience mechanisms. Using controlled experiments, we compared BMI communities in three treatments: control (C), short-term drought (S), and long-term drought (L). The results showed that drought duration significantly influenced on some community and functional diversity indices. While the C wetland maintained stable communities, S and L wetlands exhibited distinct recovery patterns post-drought. The S wetland demonstrated higher community similarity to pre-drought conditions compared to the L wetland, suggesting greater resilience to short-term disturbances. Functional diversity indices revealed complex responses, with drought altering feeding habits, living types, and voltinism traits. Long-term drought led to dominance by multivoltine species and reduced functional evenness. This study highlights the importance of drought duration in shaping BMI communities and emphasizes the need for long-term monitoring to understand wetland ecosystem recovery dynamics under climate change scenarios.

The introduction of aquatic exotic macrophytes has a major impact on the biodiversity and functioning of freshwater ecosystems by altering the structure of these habitats. Invertebrate assemblages present on sediment and plant leaves of native and exotic macrophyte beds of Ranunculus penicillatus, Potamogeton perfoliatus (natives) and Egeria densa (exotic), in the Minho River estuary (Portugal), were analysed during the spring and summer of 2023. The introduction of E. densa in the estuary of the Minho River has been shown to alter sediment characteristics by increasing the percentage of fine sediment and deposited organic matter. Assemblages observed on sediment associated with E. densa have lower diversity and are dominated by the oligochaete Bothrioneurum vejdovskyanum. This habitat is distinct from the sediments associated with native macrophytes R. penicillatus and P. perfoliatus, which are typically favoured by Corbicula fluminea and Cryptochironomus rostratus. On the other hand, E. densa leaves show higher invertebrate diversity and abundance than native macrophytes and higher affinities with exotic invertebrates such as Menetus dilatatus, Physella acuta and Girardia sinensis, while native flora attracted mainly native insects with aquatic life stages. The effects of compact E. densa beds on water flow also affects invertebrate assemblages presenting higher abundances of species with preference for stagnant water.

The Paraguaçu River, located in the Atlantic Forest ecoregion in Bahia, Brazil, features streams with distinct characteristics and highly endemic fish fauna, particularly in the Upper Paraguaçu region. This study examined variations in the taxonomic and functional diversity of fish communities across three stream types (Type 1—cultivated areas; Type 2—rupestrian fields; and Type 3—forested areas) and evaluated differences between the dry and rainy seasons. Fourteen first- and second-order streams, covering the three described types, were sampled by electrofishing during both seasons. The results revealed no significant seasonal changes in the fish community structure. The functional diversity varied among stream types, being lower in rupestrian fields and higher in forested areas. Functional diversity was also influenced by local variables, notably with gravel substrates exerting a negative effect. Functional metrics such as functional specialization and evenness were positively influenced by forested areas but negatively impacted by cultivated areas. These findings underscore the role of environmental factors in shaping stream fish functional diversity and highlight the need for tailored conservation strategies in this semiarid region.

Aquaculture is a rapidly growing industry that plays a crucial role in meeting the global demand for seafood. However, intensive aquacultural farming practices present significant challenges, including disease outbreaks, environmental pollution, and the development of antibiotic resistance. In recent years, the use of plant-derived bioactive compounds has emerged as a promising alternative approach to address these challenges. Plant bioactive compounds demonstrate diverse therapeutic and regulatory properties that make them particularly suitable for aquaculture applications. This review article aims to provide a comprehensive overview of the potential and application of plant bioactive compounds in aquaculture. It categorizes major classes of these compounds and evaluates their benefits in enhancing fish health, growth performance, and water quality. The review also discusses the challenges and limitations associated with the use of plant bioactive compounds in aquaculture while identifying critical knowledge gaps that require further investigation. By summarizing existing research and identifying future research directions, this article provides essential guidance for researchers, aquaculture professionals, and stakeholders pursuing the sustainable and innovative use of plant-based solutions in aquaculture farming practices.