Aquatic Ecology最新文献

Freshwater invertebrates and zooplankton (FIZ) play a key role in freshwater ecosystems and in food webs, but there is little research on their life cycle, ecology, and conservation. Therefore, this study focused on FIZ’ annual dynamics (abundance, diversity, and gross energy) in 30 ponds located in two wetlands: the Marais breton and Marais poitevin (Atlantic coast, France, Europe). These ponds had a FIZ abundance of 50,412 ind/m³ per site [range of 28,864–80,690] in a year. The study defined four typologies of ponds according to the environmental variables and the presence of some key FIZ taxa. The first group had a long flooding time, high silt content, and aquatic vegetation cover. The associated taxa were Chironomidae, Gammaridae and Atyidae. The second group of ponds had moderate slopes, high sand content in the sediment and a rich abundance of microcrustacea. The third group contained shallow ponds with soft slopes and a high aquatic vegetation cover (100%), which result in high FIZ diversity. Finally, the fourth group contained ponds with steep slopes, high silt content in the sediment, and Oligochaeta as the major taxon in this environment. Defining pond typologies based on environmental factors and FIZ is essential to adapting FIZ management and conservation measures implemented on ponds. In a context of global change, a reduction or even disappearance of FIZ communities would have a catastrophic impact on all faunal taxa dependent on FIZ as a food resource.

Present study describes the reproductive cycle, sex ratio, stages of the gonadal development and gonadal index (GI) of Conus coronatus collected from Buleji and Manora, Karachi. A total of 641 (329 from Manora and 312 from Buleji) C. coronatus of different sizes had randomly collected from April 2015 to March 2016. The females showed predominance in the population at both sites. Five different stages of the reproductive cycles of male and female C. coronatus: resting, developing, ripe, partially spawned, and spawned out were found. Spawning was observed throughout the year. At resting phase all the stages of spermatogenesis and oogenesis were absent. At developing stage oogonia, oocytes, spermatogonia, and spermatocytes were abundantly present in their respective follicles. At ripe stage, in males follicle countless spermatids and spermatozoa were observed however, in female the vitellogenic oocytes were been packed in follicles. At partially spawned stage, male follicles were partially empty while in female follicles unspawned mature ova were seen. At spawned out stage, both male and female follicles were empty. Gonadal development in males was at its highest peak (4.37) in summer (September 2015) at Manora and (4.00) in summer and winter (May 2015 and February 2016) at Buleji. However, in females, the highest value (5.00) of GI was observed only in summer (July and October 2015) at Manora and (4.36) in September (2015) at Buleji.

Desmids are usually abundant in shallow peatland pools. In these localities, water temperature is closely linked to seasonal fluctuations in air temperature, so with increasing temperature extremes in temperate ecosystems, these microalgae are exposed to conditions of high-temperature stress. We investigated whether the shape, size, and growth rates of Micrasterias thomasiana, a frequently occurring species, are associated with varying temperatures in cultures and natural populations. The research was based on parallel analysis of clonal populations in temperature levels from 13 to 33 °C as well as cells from natural populations collected during the season. The effects of high temperature on morphological plasticity and fluctuating asymmetry in the shape of cellular parts were investigated by the landmark-based geometric morphometrics. The results showed that variation among individuals and fluctuating asymmetry between the lateral lobes of Micrasterias cells increased at 29 °C and in natural samples taken in July and October. In parallel, the size of semicells growing at temperatures above 25 °C decreased compared to those grown at lower temperatures. However, the temperature effects on shape and size were not directly related to the growth rates. The overall bilateral asymmetry between semicell halves did not change in relation to varying temperatures. In general, the results showed that morphological variation in natural populations of M. thomasiana reflected seasonal cycles and corresponded to plasticity associated with temperature changes in clonal cultures. It might therefore be possible to use these phenotypic markers as indicators of thermal stress in natural populations inhabiting shallow pools in peatlands.

The diversity of Ostracoda in Central Serbia is relatively unknown. With the aim of exploring this diversity, and increasing the overall knowledge on their ecology, this study was carried out over a mountainous area in Central Serbia and some parts of the Vojvodina province. In total, 46 samples were collected from 36 water bodies, with several different habitat types. Ostracods were present in 22 of those water bodies, at 27 sites. A total of 17 species were recorded, six of which are new additions to the fauna of Serbia. A multivariate analysis (Canonical Correspondence Analysis) of ostracod communities and their relationship with measured environmental factors is given, with four out of five measured environmental factors showing a significant relationship with the distribution of recorded species. These were water temperature, altitude, electrical conductivity and dissolved oxygen, while pH was not significant. A cluster analysis (UPGMA) of the samples in which ostracods occurred was also performed using Jaccard distances. It grouped samples into 7 clusters, primarily defined by presence/absence of certain species. In addition, the proportion of non-cosmopolitan ostracod species was calculated for each sample, as well as for geographically grouped samples, to investigate if the percentage of non-cosmopolitan species potentially correlates with the observable state of sampling sites, mainly in terms of anthropogenic pressure and/or habitat degradation.

Protecting the ecological environment of the Yellow River Basin (YRB) is the key to promoting high-quality development of the whole YRB. Based on the information on environmental governance and the ecological environment in the YRB from 2016 to 2020, we constructed the regional eco-environment index (ECI) of the YRB, measured the government’s environmental governance capacity, and used the entropy weight method and relevant spatial statistical tools to reveal the spatial distribution characteristics of the ECI in the YRB. In addition, we used the method of configuration qualitative comparative analysis to explore the adaptation path of environmental governance for improving the ECI. The study showed that the regional ECI of the YRB was obviously heterogeneous, showing a spatial pattern of “good in the upstream, middle in the downstream, and depressed in the midstream.” There are three appropriate paths for environmental governance to improve the ecological environment: the government efficiency-oriented, rule of law-oriented, and pressure-oriented paths, among which the government efficiency-oriented path is the most common path. The findings propose the governance path of the ecological environment in the YRB from the perspective of configuration, reveal the configuration relationship among the factors affecting the government’s environmental governance, broaden ideas for solving ecological environment improvement problems in the YRB, and enrich the research methods of the government’s environmental governance.

There is still a fundamental gap in our knowledge regarding the dormant egg bank in the littoral zone, as much of the existing information stems from studies conducted in the pelagic zone. We investigated cladoceran egg banks attached to macrophyte roots (Eichhornia azurea) and the soil surface collected from the littoral site of four Brazilian lakes. We test the hypothesis that sediment supports egg bank communities that are taxonomically distinct from those in macrophyte roots. We took replicate samples from paired examples of each egg bank and later incubated the diapausing eggs in a hatching experiment. Another aspect of our study involved classifying the egg bank community based on the traditional separation of cladocerans according to their microhabitat (pelagic vs. phytophilous). Results from the study indicated that the number of individuals and taxon richness was higher in the sediment egg banks than in those from the macrophyte roots in two of the lakes studied. The proportions of pelagic and phytophilous hatched varied between sediment and macrophyte roots egg banks within each lake studied. These findings partially supported our hypothesis that sediment contains taxonomically distinct egg bank communities compared to those in macrophyte roots. Our results suggest that the littoral zone, particularly the sediment habitat, may serve as a substrate for a persistent dormant egg bank of some pelagic cladocerans. Further comparative research among different macrophyte species and littoral sediments can help to gain more insights into cladoceran ecology and restoration programs for lakes experiencing environmental impacts.

Small hydroelectric power plants (SHPPs) are often promoted as clean and renewable energy sources. However, SHPPs are often characterized by hydropeaking, which is a practice involving the sudden release of water from turbines. Hydropeaking may have multiple detrimental effects on downstream ecosystems, among which is fish stranding. This phenomenon involves trapping fish in isolated pools or dry riverbeds, which detrimental effects on fish populations and assemblages are often poorly quantified. Here, we investigated the implications that hydropeaking may have on fish populations in small Brazilian rivers. Specifically, we recorded fish stranding events (including the number of individual fish stranded) while monitoring the practice of hydropeaking by SHPPs in two watersheds. By combining observational and modeling approaches, we examined the relationships between fish stranding events and the operation of six SHPPs along a 5 km downstream stretch. For this analysis, we focused primarily on fish families which were dominant in the rivers. Our results indicate an exponential increase in fish stranding due to hydropeaking, which significantly affects fish populations as we move away from the SHPPs axes and towards downstream sections. The principal affected fish families were Characidae (23.7% of stranding), Heptaperidae (23.2%), Loricariidae (19.8%), and Pimelodidae (11.1%). In the monitored watersheds, our models predicts that if even one fish stranding event occurs annually, it could results in the stranding of nearly 500,000 individuals. This, in turn, could have severe adverse effects on the ability of these fish families to replenish themselves. We thereby emphasize the importance of adaptive management for flow regulation and incorporating lateral fish passage structures into the riverbed. This approach is essential for achieving sustainable hydroelectric power generation in Brazil while safeguarding the ecological integrity of small rivers and their fish populations.

Bacterial communities play key roles in freshwater reservoirs, affecting their functioning and services. Understanding their occurrence in the reservoirs will help to predict how these ecosystems change in response to human activities and climate change. In this study, 16S rRNA gene sequencing was used to investigate the composition and structure of bacterioplankton in two drinking water tropical reservoirs with different trophic state in Puerto Rico: Cerrillos (mesotrophic) and Lucchetti (eutrophic). The dominant lineages were typical of freshwaters such as Actinobacteria (26.7%), Gammaproteobacteria (23.3%), Alphaproteobacteria (17.7%), Firmicutes (8.2%) and Cyanobacteria (5.9%). However, the bacterioplankton composition and diversity were variable throughout the water column in both reservoirs, indicating that environmental gradients such as temperature, dissolved oxygen, and nutrient create a variety of habitats that support different bacterial assemblages in these reservoirs. Frankiales and Micrococcales were dominant in the metalimnion, whereas Bacillales were common in the deep layers, mainly in the anoxic zone of Lucchetti. The trophic state of these reservoirs also affects the bacterioplankton structure. Picocyanobacteria were represented mainly by Cyanobium PCC-6307, with higher abundance in Cerrillos compared to Lucchetti, indicating its preference for less eutrophic reservoirs. The detection of potentially pathogenic species such as Acinetobacter lwoffii and A. Schindleri, and cyanobacteria ecotypes as possible indicators of eutrophication, indicate the importance of monitoring these aquatic ecosystems, to implement mitigation programs and conservation strategies in tropical reservoirs used as drinking water sources.