Aquatic Ecology最新文献

Thermal stratification, which is a common feature of lentic freshwater systems, has extensive effects on ecological interactions and ecosystem function, including processes that may determine which systems can support fish populations and affect growth, phenology, and metabolism where populations exist. Because these habitats are important for Northern freshwater fishes, improvement of our ability to forecast thermal stratification and associated ecological processes, like dissolved oxygen dynamics, could increase the accuracy of occupancy and distribution modeling, inform conservation strategies, and predict contemporary evolutionary patterns. Although thermal regimes in temperate systems are well-characterized, the irregular thermal regimes that are often present in small Arctic and subarctic lakes and ponds are more poorly understood. In a unique cave pond system near Mývatn Iceland, where conditions shaped by thermal stratification may be acting as selective agents on divergence of Arctic charr populations, we found differences in thermal stratification regimes related to the orientation of cave openings and the highly irregular catchment topography. In particular, while greater exposure to warm air temperatures can facilitate summer stratification and results in more temporally and spatially variable temperatures, exposure to wind—which is modulated on a small scale by the terrain—can facilitate mixing. These patterns caused only the more sheltered of the two ponds remain continuously isothermic. We also found that growth rates and body condition in the ponds’ Arctic charr populations (Salvelinus alpinus) are consistent with constraints on growth and metabolism imposed by low temperature in the cooler, continuously isothermal pond, although we cannot rule out the effects of prey limitation.Kindly confirm the metadata are identified correctly.metadata is correct, but doi for supplementary materials is not active yet. (I assume this is normal)

The effects of invasive plants on arthropod communities are highly variable, shaped not only by the resources these species introduce but also by the baseline availability of those resources in the invaded environment. In nutrient-poor ecosystems such as subarctic Iceland, nitrogen-fixing invaders may enhance litter quality and boost primary productivity, potentially benefiting arthropod communities. However, the extent of these effects likely depends on the presence of external nutrient inputs, such as aquatic resource subsidies. Interactions between plant invasions and aquatic subsidies likely have significant ecosystem consequences, yet their combined effects on arthropod communities remain poorly understood. Here, we examined how an invasive nitrogen-fixing lupine, Lupinus nootkatensis, and aquatic resource subsidy from the deposition of midge carcasses affected arthropod communities in subarctic heathlands. In 2013, we set up 2 × 2-m plots in native (“Heath,” n = 12) and lupine-invaded (“Invaded,” n = 12) heath vegetation and manipulated aquatic subsidies (control, inorganic KNO₃, and midge carcasses) in experimental plots for 6 years (2013 – 2018). We sampled arthropods using pitfall traps and soil-core extractions via Berlese-Tullgren funnels. In both the Heath and Invaded plots, aquatic resource subsidies altered arthropod community composition, with the KNO₃ and midge-addition plots containing more beetles and control plots containing more harvestmen and velvet mites. Increasing beetle densities were positively correlated with grass cover, whereas harvestmen and velvet mites were correlated with native heath shrubs (e.g., Betula nana and Vaccinium uliginosum). Lupine invasion had minimal effects on arthropod composition, as only the beetles were found in higher abundances in the Invaded plots. No other arthropod taxon responded to lupine invasion. These findings suggest that aquatic resource subsidies can influence arthropod communities in nutrient-poor ecosystems, but lupine invasion may be less important in determining arthropod community structure in these subarctic ecosystems.

Mollusc species are ecologically and economically important, acting as fishery resources, ecosystem engineers, bioindicators, and invasive species. However, their study in Southern Patagonian rocky shores remains limited. This research aimed to study the mollusc assemblages and to explore the effect of environmental variables (salinity regime, wave exposure and seasonality) and substrate characteristics (inclination and elevation) on community descriptors. A seasonal sampling was conducted at two sites in Bahía San Julián: one exposed to wave action (SJO) and one sheltered (SJI). Additionally, a sheltered estuarine site was studied in Río Gallegos (RGE). The results showed that at lower horizontal substrates species richness was highest in exposed marine environments (SJO: 7–19 spp.), followed by sheltered marine (SJI: 5–13 spp.) and estuarine environments (RGE: 2–8 spp.). Total density peaked in exposed-marine environments at upper substrates (SJO: 23,000–38,000 ind/m²) and was lowest at lower substrates (ca. 2200–13,000 ind/m²), considering both orientations (horizontal and vertical). A distinct composition of mollusc assemblages were determined between sheltered-estuarine (RGE) and marine environments (SJI and SJO), and between substrate characteristics. The explained variation of mollusc abundance, was attributed mainly to salinity regime (32.8%), followed by substrate elevation (14.7%), wave exposure (10.1%) and substrate inclination (9.0%). Suspension feeders were the dominant group in all study sites. Our findings suggest that species richness, density, and diversity of mollusc assemblages are synergistically determined by environmental variables and substrate characteristics. The present study provides essential information for developing marine biodiversity conservation programs in Southern Patagonia.

Tropical lakes play a significant role in the global carbon cycle, although their contributions remain poorly characterized. This study presents a comprehensive six-year monthly monitoring of two tropical lakes, Lake Nova (LN) and Lake Juparanã (LJ), in southeastern Brazil, aimed at understanding the influence of thermal stratification and wind on carbon dynamics, metabolism, and CO₂ fluxes at the air–water interface. Thermal profiles and metabolic indicators (pO₂, pCO₂, respiration index (RI), dissolved organic carbon (DOC), and chlorophyll-α (Chl-α) were used to clarify when the lakes acted as CO₂ sources or as sinks. The results revealed a marked predominance of CO₂ fluxes in the atmosphere in both systems, with the highest emissions occurring during the mixing events. While LN exhibited stable stratification for most of the year, promoting CO₂ accumulation at depth and episodic releases during overturn, LJ underwent frequent mixing, resulting in more continuous but lower daily emissions than those of LN. The RI indicated that LN was net heterotrophic (RI < 1) during the stratified periods, whereas LJ remained autotrophic (RI > 1).  The Generalized Linear Models analysis highlighted the role of thermal dynamics and wind forcing in modulating CO₂ variability within the water column. These findings underscore the need to incorporate lake-specific physical processes into global carbon models, particularly in tropical systems.

Elevated water temperature, a primary driver of global climate change, may modify the performance aquatic plants in freshwater systems. Despite growing interest, the influence of warming on the growth and physiological responses of submerged macrophytes in the presence of plant–plant interactions are still not well elucidated. Thus, a two-week experimental study was conducted to assess the effects of elevated temperature on the interaction among Myriophyllum spicatum and Ceratophyllum demersum (collected in the Mediterranean region), growing individually and in coexistence. We hypothesised that (1) plant performance will be enhanced at higher temperature in a short-term exposure, and (2) species-specific responses to warming would occur, particularly under coexistence. To test these hypotheses, plant growth (apical elongation and lateral branch production) and pigment composition (chlorophylls and carotenoids) at 22 °C and 27 °C were examined in controlled laboratory experiments incorporating no-interaction, intraspecific, and interspecific interaction treatments. The studied variables indicated that increased temperature had only a minor effect on plant performance. Even though the temperature was elevated by 5 °C, it remained at a tolerable level for both species and represented only a mild warming for them. However, we observed some species-specific responses depending on the type of interaction. M. spicatum performed better at higher temperature, while C. demersum seemed resistant to change under two different temperatures at least in short-term exposure. Also, the plants were more sensitive to increased temperature under intraspecific interaction. The two-week microcosm experiment effectively captured short-term responses under controlled conditions, which is valuable for initial, exploratory investigation.

The rapid population growth of whooper swan Cygnus cygnus in Fennoscandia raises concerns about their ecological impact on freshwater wetlands. As large herbivores, swans can potentially alter wetland vegetation through intensive grazing, which in turn suggestively affects other trophic levels, including aquatic macroinvertebrates. However, studies examining both direct and indirect effects across trophic levels remain limited. To address this gap, we conducted a field experiment across ten boreal wetlands in Finland during the breeding season (April–August) of 2023, using fenced exclosures to prevent swan grazing, paired with open control plots. We expected that swan exclusion would result in higher vegetation aboveground biomass, cover, height, and species richness, which in turn would support greater abundance and taxon richness of aquatic macroinvertebrates. Our results indicate that swan exclusion led to increases of all vegetation variables, particularly aboveground vegetation biomass. Among vegetation types, the strongest grazing effects were observed for water horsetail Equisetum fluviatile and graminoid species. However, there was weak support for indirect effects on macroinvertebrate abundance and taxon richness. These results suggest that swan herbivory may shape wetland ecosystems primarily by altering vegetation. Further research is needed to particularly assess the long-term consequences of swan herbivory on wetland ecosystem functioning and community composition.

In nitrogen-limited lakes, cyanobacterial nitrogen (N) fixation rates can be high. However, the effect of cyanobacterial N fixation on ecosystem N availability depends, in part, on the retention of fixed N. Here, we explore patterns of benthic and pelagic N fixation and fixed N retention in Lake Mývatn, Iceland. Our N budget, updated from previous assessments, showed that the annual rate of lake-scale N fixation needed to account for the deficit between external N supply and N loss varies greatly from year to year, primarily due to variation in the magnitude of N loss via outflow and midge emergences that transport and deposit N on the shore. Extrapolations from recent direct measurements of pelagic and benthic N fixation under scenarios of different benthic and pelagic N-fixer abundances showed that the capacity for N fixation is much higher in the pelagic than the benthic zone. We then explored the degree to which N fixed in the pelagic zone is retained and recycled within the lake using a dynamic N budget that leverages data on patterns of N loss via the outlet river Laxá. This revealed that approximately two-thirds of organic N in the pelagic zone must be incorporated into the benthos to explain patterns of N loss via outflow from the river Laxá. Together, these results suggest N fixation in pelagic cyanobacterial blooms may supply most of the N for benthic primary production in Mývatn.

High-altitude forest lakes are crucial ecological and economic resources. This study examined the physicochemical characteristics of water and changes in aquatic macrophytes in Lake Nilnag, Kashmir, in response to dredging by the Department of Irrigation, Jammu and Kashmir, and anthropogenic pressures. Five sites were studied during 2019–2020 across three seasons (summer, autumn, and winter) in both the littoral and limnetic zones. Eleven macrophyte species were identified, comprising emergent (36%), rooted floating-leaved (36%), and submerged (27%) forms, with their distribution restricted to the littoral zones. Historical comparisons revealed the loss of five species and the gain of three emergents, indicating a shift toward emergent-dominated communities. Phytosociological analyses showed peak metrics in summer for rooted floating-leaved species (e.g. Potamogeton natans: IVI 47.66, density 3.55 plants/m²), with moderate diversity (Shannon H' overall 2.15; highest in autumn, at 2.18). Statistical analyses, including Pearson's correlations and PCA (explaining ~ 99% variance), revealed strong positive links between temperature and rooted floating-leaved species (r > 0.8, p < 0.01) and nutrients (especially phosphorus) with emergents (r up to 0.883, p < 0.01), driving eutrophication and accelerated succession. Nutrient concentrations averaged 201.5 ± 1.55 μg/L nitrate-N, 18.56 ± 0.76 μg/L ammoniacal-N, and 22.53 ± 3.24 μg/L. Dredging, agricultural runoff, and tourism-related eutrophication have significantly altered macrophyte composition and lake dynamics. Collaborative efforts among researchers, the Jammu and Kashmir Department of Irrigation, and non-governmental organizations are essential for the long-term conservation of this forest lake.

Viruses are increasingly recognized as key components of microbial food webs, influencing planktonic community structure and carbon cycling in marine ecosystems; however, their role in subtropical coastal systems of the Gulf of California remains poorly understood. In this study, we examined the seasonal dynamics of virioplankton and their potential influence on the size structure of bacterioplankton and phytoplankton in a meso-eutrophic coastal lagoon. Virioplankton abundances ranged from 2.0 to 16.3 × 10⁷ VLP ml⁻¹ (mean: 7.0 × 10⁷), while bacterioplankton abundances varied from 3.8 to 16.5 × 10⁶ cells ml⁻¹ (mean: 8.7 × 10⁶ cells ml⁻¹). Spatiotemporal patterns in virioplankton abundance and virus-to-host ratios showed pronounced increases during winter–spring, coinciding with elevated dissolved inorganic nitrogen concentrations and higher phytoplankton biomass associated with seasonal runoff and coastal upwelling. Under these conditions, increased virus-to-host ratios suggest enhanced viral–host interactions during periods of high microbial activity. A significant positive association between virioplankton and bacterioplankton abundances (p < 0.05) supports a close coupling between viruses and prokaryotic hosts. Partial redundancy analysis identified dissolved oxygen as the strongest environmental predictor of virus-to-host ratios. In contrast, negative associations with temperature and urea may indicate reduced viral replication efficiency or a greater prevalence of non-lytic infection strategies under warmer, nitrogen-limited conditions. These findings underscore the context-dependent nature of virus–host interactions and stress the need to quantify and integrate viral processes into conceptual and biogeochemical models of coastal ecosystems shaped by anthropogenic nutrient inputs.

Aldrovanda vesiculosa is a critically endangered aquatic plant in the Danube Delta, where it is vulnerable to water level fluctuations. The study was conducted in the Perișor fish farm (Tulcea County) between June and August 2024, within the polders of the fish farm. To identify habitat and phytocoenological preferences, relevés were carried out using a 1 m² plot size. A ProDSS multiparameter digital water quality meter was used to analyze the physicochemical properties of the water, and spectrometric methods were employed to analyze the physicochemical properties of the sediment. Bathymetric measurements were performed using the SonTek Acoustic Doppler Current Profiler (ADCP) RiverSurveyor M9 for the hydrological analysis. Aldrovanda vesiculosa was reported in four EUNIS habitat types. The most favourable habitat was C1.32 free-floating vegetation, where the highest densities and individual lengths were reported. In habitat Q53 (Tall sedge beds), the lowest values for density and length of individuals of A. vesiculosa were recorded. Cluster analysis revealed six associations, such as Typhetum angustifoliae, Spirodelo-Aldrovandetum, Caricetum ripariae, Schoenoplectetum lacustris, Nymphaeetum albae, and Phragmitetum australis. Length of individuals ranged from 4 to 21 cm, and number of individuals per m² ranged from 3 to 300 individuals per m². Physicochemical analysis of the water showed that A. vesiculosa occurred under moderate temperatures (22–27 °C) and alkaline pH values (7.8–11.6), with variable, sometimes elevated ammonium and nitrate concentrations and shallow waters (7–30 cm). Correlation analysis indicated that the length of A. vesiculosa individuals was more sensitive to environmental gradients than the number of individuals per m². Thus, the minimum and medium length of individuals showed significant negative relationships with water conductivity, while the medium length of individuals also decreased with increasing water depth and transparency. In contrast, the number of individuals per m² was weakly correlated with most environmental variables. In conclusion, the results underline the importance of habitat quality and hydrological stability for the conservation of A. vesiculosa in the Danube Delta, supporting the need for continuous monitoring and targeted conservation measures. Comparisons between the main Perișor Channel and the polders indicate that maintaining controlled connectivity and water-level management at the main-channel connections may be crucial for hydrological stability and habitat quality in A. vesiculosa sites.