Hydrobiologia最新文献

Understanding and improving passage by diadromous species at tidal barriers is less well advanced than that for non-tidal anthropogenic river barriers. This study assessed factors affecting upstream passage of anadromous river lamprey (Lampetra fluviatilis) at a tidal weir with pool-and-weir (PAW) and bypass (BP) fishways. A Continuous Time Markov Model (CTMM) was used to analyse migration behaviours of 120 acoustic- and PIT-tagged lamprey across 2 years. The weir was a major barrier to upstream migration with a mean time of 31.0 days taken to pass the weir compared to 2.5 days for the unobstructed reach immediately downstream. River stage was the most important variable associated with weir passage, with a 5.68 (CI = 3.95, 8.17) increase in passage probability for every 1 m river stage increase. Passage was predominately over the weir directly rather than by the fishways. Monitoring the fishways using additional PIT-tagged lamprey (n = 2814) suggested poor entrance efficiency (BP₂₀₁₈, 28.6%; BP₂₀₁₉, 53.1%; PAW₂₀₁₈, 37.0%). Successful fishway passage was estimated as 5.4% (BP₂₀₁₉)–9.0% (PAW₂₀₁₈) of lamprey that entered. Effective fishway entrance for lamprey is probably facilitated by high fishway discharge, yet high-velocity areas may have made it difficult for river lamprey to successfully ascend the fishways.

Submerged macrophytes are crucial for the restoration of shallow eutrophic lake but they are diminished in coverage or lost with eutrophication. Their recovery after nutrient loading reduction depends on water and sediment nutrient levels. We studied the combined impacts of sediment fertility (low/high nitrogen and phosphorus content) and water nutrient concentrations (low/high nitrogen and phosphorus addition) on Vallisneria denseserrulata in a mesocosm experiment. We hypothesized that both the elevated external nutrient addition and high sediment nutrient contents would inhibit plant growth. We found that an increase in nutrient concentrations resulted in a significant increase in algal biomass. Furthermore, high external nutrient addition significantly reduced both the relative growth rate (RGR) and the density of V. denseserrulata growing in the nutrient-rich sediment, while in the nutrient-poor sediment treatment, RGR was not affected but the plant density decreased. Interestingly, low nutrient addition appeared to be more conducive to growth and reproduction of V. denseserrulata in the nutrient-rich sediment than in the nutrient-poor sediment. Our findings emphasize the importance of reducing external nutrient inputs is of key higher importance when restoring shallow eutrophic lakes, while the plants may benefit of the nutrient-rich sediment occurring in such lakes after eutrophication.

Karst freshwater ecosystems are considered biodiversity hotspots, highlighting their sensitivity and vulnerability to environmental change. However, our understanding of the distribution and ecology of macroinvertebrates in lotic karst habitats is still incomplete. Therefore, to fill the knowledge gaps, the current study was conducted in the Dinaric and Carpathian–Balkan Mountains in Serbia, Southeastern Europe. We studied aquatic macroinvertebrates and their relationship with environmental parameters at 25 sampling sites in three habitat types (springs, the upper reaches, and tufa barriers) in 12 rivers and streams in Serbia, seasonally, between 2019 and 2022. We recorded 85,072 individuals within 206 taxa. Most environmental variables were comparable among the three habitat types, which most probably resulted in comparable abundance and diversity of benthic macroinvertebrates. However, taxa richness was lower in springs compared to upper reaches and tufa barriers. Environmental parameters had a greater impact than spatial effects on shaping the macroinvertebrate community. Moreover, IndVal analysis revealed a list of 30 indicator taxa associated with specific habitat types. We emphasized that highly specialized species support vulnerable functions in high-diversity karst freshwater ecosystems. Therefore, this study establishes a scientific foundation for implementing effective management strategies for these unique aquatic ecosystems.

Urban and peri-urban lakes experience a wider array of environmental stressors, and often at a higher intensity, than their rural counterparts, including road salt runoff. A paleolimnological approach was used to determine pre-disturbance limnological conditions and to evaluate the impact of environmental stressors (nutrient inputs, climate change, and winter de-icing salt) on the long-term (~ 150 years) water quality of a small urban kettle lake in the Oak Ridges Moraine near Toronto, Ontario, Canada. Specifically, we examined Cladocera and diatom subfossils in ²¹⁰Pb-dated sediment cores from a lake with elevated measured chloride concentrations, Haynes Lake (Cl⁻ = 201 mg/l), and a nearby reference lake located in a conservation area (Swan Lake, Cl⁻ = 28 mg/l). In Haynes Lake, Cladocera compositional change is consistent with increasing Cl⁻ concentrations, showing a shift from a Bosmina spp.-dominated cladoceran assemblage to a Daphnia spp.-dominated assemblage. Concurrently, we recorded increases in the relative abundances of the diatom taxon Achnanthidium minutissimum and benthic fragilarioid taxa. These biological changes coincided closely with the onset of road salting in the region (ca. 1940s). The reference site (Swan Lake), located ~ 1 km from our salt-impacted site, displayed only minimal changes in both Cladocera and diatom assemblages, suggesting road development and salting within the Haynes Lake watershed had a larger impact than regional stressors (i.e., climate).

Along the U.S. east coast, the widespread non-native red alga Gracilaria vermiculophylla provides habitat for an array of macroinvertebrates, including the eastern mudsnail Ilyanassa obsoleta. Though I. obsoleta tolerates a wide temperature range, increases in summer water temperatures may enhance mortality; furthermore, the presence of non-native algae in rising seawater temperatures could exacerbate harmful conditions. We tested how the presence or absence of G. vermiculophylla influenced snail mortality across a range of summer temperatures over a 3-week period. We found that I. obsoleta survived the longest in the lowest temperature (27 °C), followed by the medium (32 °C), and lastly the highest (36 °C) where all snails died within 2 days. Mortality was also higher and faster for snails in the presence versus absence of G. vermiculophylla. We suspected dissolved oxygen became very low at the higher temperatures with G. vermiculophylla; thus we conducted a laboratory-based dissolved oxygen experiment. We found that G. vermiculophylla degraded and oxygen declined faster at the highest temperature treatment, thereby creating anoxic conditions. Altogether, our results demonstrate that G. vermiculophylla could enhance anoxic conditions at high summer temperatures, potentially leading to enhanced faunal mortality.

Recruitment of the catadromous and critically endangered European eel Anguilla anguilla in Europe has declined substantially since the 1980s, with considerable knowledge gaps remaining in many aspects of their life cycle. The aim was to assess eel migration phenology in three regulated rivers in England between 2009 and 2019 through analyses of eel numbers using passes at their tidal limits, with calculation of the annual timings of migration initiation (10% of all eels passed, T₁₀), peak (50%, T₅₀) and conclusion (90%, T₉₀). Across the three rivers, T₁₀ varied between Julian Day (‘Day’) 94 and 173. Years of earlier T₁₀ had significantly earlier T₅₀, where T₅₀ varied between Day 105 and 200. The considerable inter-annual variability in migration timings was associated with environmental variables; earlier T₁₀ and T₅₀ occurred in years of warmer river temperatures (RTs) and cooler sea surface temperatures (SST), and in years where RTs were higher than SSTs. No environmental variables were significant predictors of T₉₀. These results indicate that whilst there is annual variability in the timing of eel migration initiation and peak into freshwaters, this variability is predictable according to differences in environmental conditions. As many of these conditions associated with annual variability in temperature and precipitation then climate change has the potential to shift these migration timings.

Accurate species delimitation and phylogenetic reconstruction are vital to understand biodiversity assessments, conservation management, evolutionary patterns, evolutionary processes, and historical biogeography. The taxonomy and phylogeny of the genus Neolissochilus (Cyprinidae) have a confusing history. We investigated the taxonomy and phylogeny of this group and related lineages using complete mitochondrial genome sequence data from 53 Cyprinidae species and one outgroup species. These analyses show that the monophyly of Neolissochilus and Tor is not supported. N. benasi might represent a new genus, and T. qiaojiensis should be moved into Neolissochilus. We estimated divergence times, evaluated the monophyly of this group, their relationship to other cyprinids, as well as the time course and geography of speciation. The results indicated that the family Cyprinidae likely diverged from other taxa during the Eocene (ca. 54.78 Mya), and species of various genera began to undergo massive diversification events during the Cenozoic Tertiary. The differentiation and diffusion of the family Cyprinidae might be attributed to the Qinghai–Tibet Plateau uplift events, one of the geological events marking the Cenozoic Tertiary period, which cut off genetic exchange between populations through geographic isolation, thus facilitating genetic divergence between populations and eventually leading to the formation of new species. In addition, the results of this study still need further improvement. The limitations are mainly due to the small sample size and the use of only mitochondrial data; therefore, it still needs to be further verified by combining nuclear genome data.

We present a 57-year time series and relationship with environmental parameters of a zooplankton species Chydorus sphaericus, a common small-sized cladoceran species in eutrophic lakes, in a large, shallow and eutrophic Lake Võrtsjärv (Estonia). We show that over the course of more than five decades, the abundance, mean weight and the proportions of C. sphaericus among metazooplankton biomass in this lake have markedly changed. Planktivorous fish (bleak Alburnus alburnus in particular) and total phosphorus were the most influential variables explaining the interannual changes of C. sphaericus individual weight. Abundance and the C. sphaericus proportion among metazooplankton biomass were dependent of a complex set of antagonistic interactions between water temperature, cyanobacteria biomass and pH. Cyanobacterial biomass stood out as the most influential factor for C. sphaericus at the monthly scale. Chydorus sphaericus metrics were negatively correlated with cyanobacteria, positively when cyanobacteria biomass was paired with pH or water temperature, and negatively again when all three variables were present at the same time. Our results confirm that C. sphaericus occupies an important position in a eutrophic lake food web and has been able to thrive in the recent decades through adaptative interactions with its environment.

Invasive alien anurans are introduced worldwide in freshwater ecosystems where they can have a strong impact on native organisms such as amphibians. The risk for natives is dependent on the degree of niche overlap and co-occurrence in pond-breeding sites. In the present study, we focused on alien marsh frogs (Pelophylax ridibundus) that are invading nationwide areas in Western Europe and which prey on both caudates and anurans. We assessed aquatic habitat preferences, pond use and environmental niche overlap between invasive populations of marsh frogs and five species of native amphibian prey of the Larzac plateau (southern France). Due to their large environmental niche, marsh frogs have become the most ubiquitous amphibians in the area. Occupancy models revealed that they had aquatic habitat preferences (e.g., water depth and aquatic vegetation) similar to most species of native amphibians. This resulted in a large overlap between the environmental niche of the invader and its potential prey. The frequent coexistence in ponds therefore exposed native species to predation risk and other potential disturbances caused by marsh frogs. Altogether, these results highlight on the risks posed by such opportunist invaders for native amphibians that occur in their wide invasion range.

Bacterial community composition (BCC) can be modulated by different indirect and direct factors. The Strobel Lake Plateau (Patagonia, Argentina) holds natural fishless lakes. Fish introduction in some of these lakes has affected the structure of their zooplankton, phytoplankton and autotrophic picoplankton communities, whereas its effects on bacterioplankton are unknown. Hence, we analyzed BCC to assess the potential effect of fish introduction on this community in lakes of this region. We sampled fishless and fish-stocked lakes during three summer campaigns and analyzed the BCC. Our results revealed a contrasting arrangement in the main limnological variables and significant differences in the BCC between fishless and stocked lakes. In fish-stocked lakes, Alphaproteobacteria class had a higher proportion and SAR11_cladeIII was the most abundant amplicon sequence variant (ASV); these lakes also showed a marginally higher mean richness but less exclusive ASVs. Environmental and biotic factors contributed to explain BCC variations. The lower percentage of exclusive ASVs and the closer BCC ordination in a non-metric multidimensional scaling suggest a homogenizing effect in fish-stocked lakes. This study contributes to understand the consequences of fish introduction on the plankton communities in lakes of this invaluable region for biodiversity conservation.