Hydrobiologia最新文献

Neotropical streams stand as one of the most biodiverse aquatic ecosystems in the world. The extremely high biodiversity of these ecosystems was generated and modified by several geological events, major climatic changes, and complex ecological mechanisms. Here we synthesize ecological concepts that influence the organization of Neotropical stream biodiversity. We analyze the ecological processes from three perspectives: horizontal (i.e., competition between species), vertical (i.e., trophic organization), and regional perspectives (i.e., environmental selection, stochasticity and dispersal). Our review highlights that Neotropical streams are understudied compared to other regions considering the three ecological perspectives and the human impacts on these ecosystems. The lack of studies in the horizontal perspective is prominent compared to the other perspectives. Overall, our knowledge of the biodiversity and dynamics of Neotropical streams is concentrated on the regional perspective and especially on the anthropogenic impacts on aquatic biodiversity. We identify some gaps in knowledge and conclude that the ecology of Neotropical streams is rapidly changing in the face of the current environmental crisis generated by multiple disturbances. These results indicate an urgent need for integrated ecological studies of Neotropical streams, considering their high global proportion of biodiversity and the multiple services these ecosystems support.

Nutrient enrichment can impair the biotic integrity of steams and rivers. Nutrients derived from land use practices have been identified as sources of water quality impairment in several Central California Coast watersheds resulting in excess algal growth. We developed an algae-based multi-metric index to assess the biotic integrity of streams and rivers in this region because algae often respond directly to changes in nutrient levels. Additionally, we apply the algal index of biotic integrity to the development of an effects-based nitrogen reduction target. Eleven individual metrics based on diatom autecologies, community structure, ecological guilds, tolerance, and intolerance were incorporated into the index. All algal production metrics failed reproducibility criteria for inclusion in the index. The index of biotic integrity was highly correlated with human disturbance (r = − 0.6213) and was significantly different between classes of least-, intermediate-, and most-disturbed sites. Piecewise linear regression showed a steep negative relationship between nitrate–N and the index with a breakpoint of 0.505 mg/L nitrate–N, above which the negative trend became insignificant. This change in the relationship between nitrate and the index of biotic integrity suggests that this breakpoint can aid the development of a reasonable effects-based criterion for nitrate–N in this region.

Secondary consumers meet their nutritional needs via their prey and are limited by the dietary resources available for their prey. This is especially relevant in ecosystems which cannot be abandoned, such as in small water bodies. In this work, I studied how urodele larval growth, development and behavior are affected by the diet of their prey. I reared Salamandra salamandra larvae in captivity, feeding them mosquito larvae fed either a plant-based (vegetal treatment) diet, a meat-based (animal treatment) diet or a combined diet (mixed treatment). I measured body size of salamander larvae and metamorphs, locomotor performance, flight initiation distance, and feeding rates of larvae, and time and survival until metamorphosis. The vegetal treatment showed reduced body size, lower foraging rates, and lower survival. Locomotor performance, flight initiation distance, and time to metamorphosis were not affected by treatment. These results highlight how prey diet affects secondary consumers. Thus, the success of a given individual can depend on the productivity of its ecosystem or the income of exogen matter.

Mesocyclops ogunnus (Copepoda, Cyclopoida), originally from Africa and Asia, is now invasive species in Brazilian freshwaters, raising concerns due to its capacity to colonize eutrophic lentic ecosystems. Their high reproduction and dispersal rates, coupled with the production of resistance eggs, pose a significant threat to the habitats of native species by potentially leading to niche overlap and displacement. Here, we used a comprehensive dataset, including GBIF records and a systematic literature review, to assess current suitable areas for the species in Brazil through a species distribution model approach. Our final dataset encompasses 136 data points for the native range in Africa and Asia and 238 data points for the invaded area in Brazil. The SDM’s models showed new potentially suitable areas for M. ogunnus colonization across the Paraná River Basin, the main watercourses of the Amazon River Basin, and the San Francisco River. These findings underscore the importance of predictive modeling in identifying potential areas of occurrence for M. ogunnus, providing a foundation for management strategies to mitigate its spread and ecological impact.

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.

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.

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.

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).