Aquatic Ecology最新文献

Periphyton is an important basal food source for many aquatic consumers by directly or indirectly providing long-chain polyunsaturated fatty acids (LC-PUFA). Although periphyton LC-PUFA content is highly sensitive to aqueous nutrients, the majority of prior studies have been conducted in low-nutrient aquatic environments. Less is known about how periphyton LC-PUFA content may change in response to higher nutrient concentrations in rivers. We conducted a periphyton culturing experiment by manipulating a gradient of aqueous nutrient concentrations from 0.002 to 0.18 mg P/L to investigate how aqueous nutrients affected periphyton FA from oligotrophic to eutrophic waters. Our results showed a significant curvilinear relationship between aqueous water nutrients and periphyton FA. In oligotrophic conditions, periphyton LC-PUFA increased as aqueous nutrients increased, whereas in eutrophic waters, periphyton LC-PUFA decreased as aqueous nutrients increased. The change of taxonomic composition, especially the increase of diatom density, was a significant factor influencing periphyton LC-PUFA content. Additionally, periphyton biomass experienced a significant increase with elevated aqueous nutrients, which differed from periphyton LC-PUFA. Our study detected the response of periphyton FA to aqueous nutrients from oligotrophic to eutrophic conditions, and provided a reference for the protection of river ecosystems.

Gastropoda assemblages were investigated for four seasons in 2016–2017 (autumn, winter, spring, and summer) near Umm Al-Namil Island in Kuwait in rocky and sandy habitats to study the effect of season and habitat type on species richness, abundance, evenness, and diversity. A total of 28 gastropod species belonging to 14 families were identified (26 in sandy, 20 in rocky, 18 in common between both habitats). Clypeomorus bifasciata (31.07%) and Trochus erithreus (21.43%) were the most abundant species in the rocky habitat. Pirenella arabica (27.51%), C. bifasciata (26.15%) and Mitrella blanda (15.66%) dominated the sandy habitat. At the rocky habitat, total abundance ranged from 6.5 ± 4.71 to 40 ± 45.17 ind m⁻² in autumn and summer, respectively. As for the sandy habitat, total abundance varied from 53.0 ± 22.60 to 294.0 ± 316.67 ind m⁻² in summer and winter, respectively. The results of the rocky habitat showed that diversity and evenness were strongly affected by season more than habitat type. Species richness and abundance were strongly influenced by habitat type rather than the season. However, the sandy habitat had a higher value of abundance, diversity, species richness, and evenness throughout the sampling period than the rocky habitat. There was almost a distinction between the species resident in both habitats throughout the study. These findings could be attributed mainly to the feeding habits of these gastropods and their burrowing nature.

Rivers interlinking by transposition projects have multiplied in the world, altering the landscape and flow regime of continental water systems. Recently, an intermittent river in northeastern Brazil has been artificially connected to the São Francisco River basin in a water transfer project. Thus, this study aims to provide an inventory of the fish parasites from the Jaguaribe River basin in the scenarios of pre- and post-transposition, and to evaluate the short-term impacts on the parasite fauna. Of the analyzed fishes, belonging to 31 species, about 30% were parasitized. A total of 47 parasite taxa were recovered, including monogeneans (17), digeneans (9), nematodes (9), acanthocephalans (3) and crustaceans (6), and unidentified cysts of Acanthocephala, Cestoda and Digenea, representing the description of 30 new geographic records and 104 new parasite-host associations. By expanding the range of the geographic distribution of fish parasites and increasing the list of hosts, the study contributes to the knowledge of fish parasites biodiversity in the semi-arid region of Brazil and in the Caatinga domain. Considering all parasite species, significant differences were observed in total prevalence, total mean abundance, diversity index and host specificity index; the highest values of total prevalence and total mean abundance were observed in the post-transposition, while the diversity index and host specificity index was higher in the pre-transposition period. This is the first study evaluating fish parasites before and after a major water transfer event and the results will allow further evaluation of middle and long-term changes in the specific composition of fish and parasites from the receiver drainages.

The reproductive strategies of species play a fundamental role in formulating effective management plans and maintaining local community structure and ecological balance. This study investigated the reproductive characteristics of two sympatric species, Callinectes danae and Callinectes ornatus, in Atlantic waters. Monthly sampling was conducted from July/12 to June/14 in the coastal (sites: S1, S2, S3 and S4) and estuarine-lagoon (sites: S5, S6 and S7) areas of Cananéia-Iguape, Brazil. Significant differences in allometric coefficients were observed, particularly in the relationships chelipod length vs. carapace width (CW) for males and abdominal width vs. carapace width (CW) for females. Morphological sexual maturity was estimated at 58.8 mm CW for C. danae males, 54.5 mm CW for females, 45.0 mm CW for C. ornatus males, and 41.2 mm CW for females. Gonadal sexual maturity sizes were identified at 69.4 mm CW for C. danae males, 61.4 mm CW for females, and 58.4 mm CW for C. ornatus males, 46.9 mm CW for females. Both species spawn predominantly during the austral summer, with higher prevalence in site S5 for C. danae and S1 for C. ornatus. Recruitment occurred in austral spring and summer, with C. danae concentrated in estuarine-lagoon regions and C. ornatus along the coast. Reproductive patterns of C. danae were associated with temperature and salinity, while C. ornatus exhibited correlations with temperature and organic matter. This study highlights the influence of environmental factors on species' life cycles. Furthermore, it contributes to the evaluation of management and monitoring strategies, recognizing the economic and ecological significance of these species for sustaining these ecosystems.

Salinity is one of the main factors influencing the early life stages of fish along an estuary, which shows great temporal and spatial changes. Recently, remote sensing has been widely applied to map salinity changes and fuzzy logic is identified as a suitable and strong tool for modeling complex systems. Based on collections of fish larvae and juveniles and water parameters in May, September, November, and December during 2019 along the Ba Lat estuary of the Red River, northern Vietnam, the present study attempts to predict the mapping and monitoring of the salinity using multispectral satellite imagery from Landsat 8 OLI satellite. The study determined that the NFS machine learning model, when improved by PCA, achieved a higher performance in displaying different salinity levels. The present study also confirms that using high spatial resolution or hyperspectral images would have increased the accuracy of spatial variation in similar modeling and mapping. Fuzzy rule–based modelling suggests that the occurrence of fish larvae and juveniles depended on salinity levels, with an R² > 0.9, compared to the field surveys. This finding further confirms the accuracy data obtained by artificial neural network models.

Early stages of fish are easily sensitive to any alteration of environments, thus understanding their dispersions in a dynamic system like estuaries are important in protection and conservation of fish diversity and fishery resources. Especially, it is more significant for a mangrove-associated mudskipper, Periophthalmus modestus, which are distributed in mudflats along the Northwest Pacific, and now are listed as near threatened due to climate change and human activities. In the present study, a hybrid model, Extreme gradient boosting (XGBoost)-Artificial neural networks (ANN), was applied to forecast the distribution of P. modestus larvae and juveniles collected from a large estuary in northern Vietnam, which are driven by temperature and mangrove changes. Present results demonstrate the usefulness and applicability of ANN-XGBoost model in ecological studies, with an excellent estimation accuracy. Furthermore, employing Generative adversarial networks (GANs) model, this study exhibits a decrease in mangrove areas due to human activities between 2010 and 2023. This change with a rise in temperatre during this period would have impacted on P. modestus larvae and juveniles, which tend to be distributed in mangroves and avoid human-affected areas. Thus, it is concluded that changes in P. modestus’ environment like mangroves have a significant influence on their distribution and survival. Applying a novel model in ecological research, this work further indicates the importance of mangrove forests for aquatic organisms, especially mudskippers. This research will allow scientists and biological managers to make more precise forecasts regarding the spread of P. modestus, while also helping to the protection of this mudskipper and other species. Protecting and developing mangrove forests are the first and crucial action to supply a suitable habitat for any fish species. The models employed in this work will be helpful for other relevant studies when obtaining a highly accurate performance.

Single-use plastic litter is the main component of marine litter worldwide. In the present study, the impact of discarded single-use garbage bags is experimentally evaluated on density, diversity, community structure and vertical distribution of the upper intertidal free living nematode community. Our results showed that the presence of garbage bags on intertidal sediment sharply decreased total and vertical nematode densities and diversity indices as well as decreased sediment oxygen redox potential, and altered total and vertical nematode communities. However, covering sediment with garbage bags did not result in complete nematode mortality. At the end of the experiment, epigrowth feeders and facultative predator nematodes disappeared and the community was dominated by deposit feeder genera. Considering that single-use plastic litter is in intertidal ecosystems, any change in the density and biomass of benthic fauna could lead to a decrease in benthic secondary production and food shortage for their predators.

Impact of habitat characteristics and anthropogenic activities on the distribution of macroinvertebrate traits and ecological preferences was assessed in Osun State, Nigerian. Physicochemical parameters involving water depth (WD), channel width (CW), flow rate, discharge, water temperature (W.T), dissolved oxygen (DO), total dissolved solids (TDS), electrical conductivity (EC), pH, biological oxygen demand (BOD), turbidity, nitrate, phosphate and organic matter (OM), were appraised, alongside macroinvertebrates from 5 streams in different geographical locations. Sampling spanned from December 2019 to October 2021, covering early and late dry seasons, as well as early and late rainy seasons. Principal component analysis classified the sites into three impact categories: least impacted (LIS), moderately impacted (MIS), and highly impacted (HIS). Nine traits and ecological preferences displayed significant variations alongside nine physicochemical variables, such as phosphate, OM, WD, discharge, CW, TDS, EC, W.T, and nitrate, within the Fourth-corner figure. Furthermore, these traits and ecological preferences exhibited notable correlations with site impact categories, including–no turbidity preference, spherical body shape, climbers to LIS, preference for transparent water, crawlers, climbers, burrowers, small body size to MIS, and highly tolerant to ocxygen depletion to MIS.This study underscores the effectiveness of macroinvertebrate trait-based approach as a freshwater biomonitoring tool in Osun State, Nigeria, providing essential insights into how environmental factors influence macroinvertebrate traits in lotic systems in the region, with implications not only locally but also for broader eclogical studies.

River ecosystem services (RES) are vulnerable to landscape changes mainly by volcanic eruptions. Therefore, this study aims to assess RES in the volcanic area which was affected by the major and minor eruptions of Mount Merapi, Indonesia. The RES referred to the regulating and supporting services of the Krasak River in Jogjakarta. The research involved collecting water and biodiversity samples from two distinct Merapi’s hazard zones (KRB I and KRB II) along the river. Parameters related to regulating services, such as particulate, organic, and nutrient purification, biological control, as well as supporting services like primary productivity, were quantified. We conducted an analysis to understand how landscape conditions interacted with these parameters and employed the t-test to assess differences in RES between the two KRBs. Our findings revealed that the Krasak River exhibited a range of values, including 2.40–5.95 mg/l for Biological Oxygen Demand (BOD), 0.61–3.41 mg/l for nitrate, 0.02–0.11 mg/l for phosphate, 160–60,000 MPN/100 ml for coliform, and 156.3–937 µg/l for chlorophyll-A. These values demonstrated the river’s capacity to perform both regulation and support services. However, certain segments showed variations in ecosystem services, possibly due to the presence of autochthonous matter from aquatic organisms and decomposing organic matters. This showed that volcanic eruption and landscape are closely linked with the water quality and aquatic biodiversity, which affect the ecosystem services.

Seasonal variations of limnological parameters and phytoplankton dynamics in high-altitude oligotrophic lakes form a critical area of interest in assessing the implications and impact of climate change on fragile ecosystems and formulating effective conservation strategies. Thus, a study was conducted by sampling water from five High-Altitude Lakes (HALs) of Tawang district, Arunachal Pradesh between December 2019 and December 2021. The seasonal variations of seven physico-chemical parameters and phytoplankton's composition, distribution, and seasonal abundance were assessed. Further, the diversity, dominance, and evenness of phytoplankton were estimated and the relationship between limnological parameters and the phytoplankton species was established using Canonical Correspondence Analysis (CCA). The limnological parameters such as pH, dissolved oxygen, free carbon dioxide (FCO₂), alkalinity, hardness, conductivity, and total dissolved solids (TDS) show significant seasonal variations among the HALs. A total of 50 phytoplankton species belonging to 8 Class and 33 Family were recorded. The order of phytoplankton dominance was Bacillariophyceae > Cyanophyceae > Zygnematophyceae > Chlorophyceae > Chrysophyceae = Dinophyceae, Euglenophyceae = Klebsormidiophyceae. The most abundant species were Cymbella sp., Gomphonema sp., Fragilaria sp., Navicula sp., Nitzchia sp. (Bacillariophyceae), Volvox sp., Pediastrum sp., Microspora sp. (Chlorophyceae), Oscillatoria sp., Lyngbya sp., Calothrix sp., Chroococcus sp. (Cyanophyceae), Spirogyra sp., Mougeotia scalaris, Cosmarium sp., Closterium sp. (Zygnematophyceae). The abundance of phytoplankton species varied seasonally with most copious in winter. The distribution, abundance, and diversity of phytoplankton were largely influenced by pH, hardness, FCO₂, conductivity, and TDS levels. So, the findings of the study could be helpful in exploring the potentialities of introducing cold-water fisheries in HALs to ensure food security under climate change scenarios.