Aquatic Sciences最新文献

Hydropower is a reliable source of renewable energy that can support the low-carbon energy transition, even though man-made reservoirs can be significant sources of greenhouse gas (GHG) emissions. A multitude of studies have been undertaken to examine the temporal and spatial patterns of GHG emissions from reservoirs, yet no thorough examination of the influence of reservoir hydrological conditions on these emissions has been made. In this study, GHG emissions from hydroelectric reservoirs with varying volumes of water, hydraulic retention times, and power densities were evaluated for a 100-year timescale. GHG emissions from hydropower generation over a 100-year period were significantly lower than those from thermal power generation. Notably, the post-impoundment emission rates averaged 4.27 g CO₂ equivalents (CO_2eq)/m² per day, with a net rate of 3.17 g CO_2eq/m² per day. The average post-impoundment emission per unit of electricity generated was 17.22 g CO_2eq/kWh, which was lower than the global average of 273 g CO_2eq/kWh. Moreover, the emission rates were negatively correlated with volume (post-impoundment, r = – 0.70, p < 0.001; net, r = – 0.33, p = 0.06) and hydraulic retention time (post-impoundment, r = – 0.97, p < 0.001; net, r = – 0.46, p < 0.01). The post-impoundment (r = – 0.81, p < 0.001) and net (r = – 0.62, p < 0.001) emissions per unit of electricity produced exhibited a negative correlation with power density. Reservoirs with higher power densities, shorter hydraulic retention times and smaller capacities were demonstrated to have considerable advantages and potential for the mitigation of GHG emissions due to the their lower emissions of GHG per unit of electricity generated.

Lake Cadagno is a meromictic alpine lake characterized by permanent stratification, which creates a permanent anoxic environment that supports the growth of anoxygenic phototrophic sulfur bacteria. The seasonality and interseasonality of these microorganisms were examined over a three-year period (2019–2021) through regular monitoring of the water column. A variety of physical–chemical parameters, including temperature, conductivity, light, oxygen and sulfide concentrations, and the community composition of anoxygenic phototrophic sulfur bacteria in the chemocline were recorded, to observe potential influence of external weather conditions. Our findings indicate that, despite the lake’s consistent physical and chemical stratification, the composition of the anoxygenic phototrophic sulfur bacteria community exhibited notable variations in response to external environmental factors, including changes in rainfall and light irradiance. Specifically, we observed different growth dynamics in the purple (PSB) and green (GSB) sulfur bacteria communities over the three years of monitoring. These variations underscore the complexity of biogeochemical cycles in meromictic lakes and the impact of external environmental factors on this ancestral microbial community dynamics. The results provide valuable insights into the stability of redox-stratified environments, offering a modern analog for ancient aquatic ecosystems. This research emphasizes the importance of long-term regular monitoring to capture interannual dynamics and assess the implications of climate change on such unique ecosystems.

Rice fields are one of the most important agricultural environments in Northern Italy. These agroecosystems are characterized by high variations in water temperature, shading by rice plants, and sporadic droughts that affect the life of aquatic organisms. In the present study, we carried out an analysis within the limits of two rice fields and their water supply canal in the Lomellina (Lombardy; NW Italy). The aims of this study were (1) to quantify the main benthic primary producers colonizing the two rice fields and their feeding canal, focusing on diatoms, green algae, and cyanobacteria; and (2) to shed light on the taxonomic and functional composition of diatom communities living in these three environments. The study was conducted during the spring and summer 2023, corresponding to the growth phases of rice plants and the peak of diatom primary productivity. A total of 54 samples were collected from these three environments, by using artificial substrates. Diatoms dominated the canal channeling water to the rice fields, while diatoms and cyanobacteria were co-present in the two rice fields. Among the diatoms, low-profile and motile guilds were dominant in the water canal while, to the contrary, we observed a higher percentage of motile tolerant species in the rice fields, such as Navicula veneta, Nitzschia amphibia and Planothidiun incuriatum, a recently described species. The analysis of the microalgae communities can be useful to define the proper management of wetland-like environments and the conservation of their biodiversity.

The global oceanic silica cycle is regulated by siliceous plankton such as diatoms, radiolarians, and silicoflagellates. Among these, diatoms play a major role in oceanic CO₂ sequestration as they are abundant in most oceanic regions. We studied the biogenic silica (BSi) and siliceous microfossil assemblages in the surface sediments of the eastern Arabian Sea. The BSi content ranged from 1.87 to 8.51% and the major contributors to it were diatoms, sponges (their spicules) and radiolarians, with minor contributions from silicoflagellates and siliceous dinoflagellates. The abundances of diatoms and sponge spicules showed a strong positive correlation with BSi and a negative correlation with sediment grain size. Our results indicated a high abundance of diatoms in the nutrient-rich coastal sediments, while the radiolarian contribution to BSi was high in offshore oligotrophic regions. Diatom abundance showed large spatial variation, and ranged from 0.69 × 10⁴ to 1.85 × 10⁶ valves/g. The diatom assemblages in the surface sediments differed significantly from those reported for the water column. The results of this study are considered to be of particular significance with respect to ongoing effects of climate change that already pose a threat to the Arabian Sea, such as silicate limitation and ocean acidification.

Macrophytes are potentially an important dissolved organic matter (DOM) source in lakes. To assess the effect of lily pads (Nymphaea odorata) on DOM, optical properties and dissolved organic carbon concentrations (DOC) were measured over a year in Lake Louise, Pacific Northwest, USA. Lily pads were widespread around the shoreline during summer, dying back in the fall. Some optical indices (slope ratio, index of recent autochthonous contribution, fluorescence index) indicated the lake was dominated by DOM from terrestrial sources for most of the year. Indicators of autochthonous production in a few winter samples were attributed to phytoplankton. DOC concentrations and precipitation were not correlated, but DOC was positively correlated with absorption coefficient at 350 nm (α₃₅₀). DOC and α₃₅₀ were highest in summer and decreased in the winter wet season, which would be consistent with an in situ lake source being diluted by rainfall as a possible explanation for this. Excitation-emission matrix fluorescence spectra of lake waters and lily pad leachates indicated humic and protein material components. The plant leachates had slope ratio, fluorescence index, and index of recent autochthonous contribution values consistent with terrestrially derived DOM and lake waters. Higher DOC and α₃₅₀ in the summer were associated with some lower optical indices (specific ultra-violet absorbance, spectral slope, humification index, fluorescence/absorbance ratio ratios), consistent with material derived from lily pads. Estimates indicated lily pads contributed as much to the lake DOM pool in the summer dry season as watershed terrestrial inputs in the winter wet season, suggesting that DOM production by lily pads may account for a significant portion of the carbon pool in smaller lakes.

Freshwater fish populations, especially migratory species and those with larger home ranges, are declining worldwide as a result of numerous direct and indirect anthropogenic factors. Freshwater protected areas (FPAs) are an emerging conservation tool that could help mitigate freshwater biodiversity losses by offering areas within freshwater ecosystems that provide full protection to species and the critical habitats they rely on. Using acoustic telemetry, we evaluated the use of a shallow, heavily vegetated FPA by northern pike (Esox lucius; N = 29) in a large temperate lake system in Ontario, Canada from 2019 to 2021. Receivers were deployed within the FPA, in the waters adjacent to but outside of the FPA (the “boundary area”), and throughout the open-area lake basins further from the FPA. Telemetry data revealed that 46% of fish captured and released in the FPA departed and did not return (N = 6), while the remaining 54% exhibited fidelity (N = 7). Notably, northern pike spent a significant portion of time in the boundary area, potentially because it contains deeper waters (maximum 12 m) that may offer thermal refuge or transitional space for movements to the lake’s deep main basin (max 95 m). Additionally, three northern pike that were captured and released in the lake’s main basin were detected inside the boundary area; however, their use of the FPA was minimal. Our findings underscore the importance of considering habitat requirements and movement ecology of species to inform effective FPA design and identify opportunities to enhance conservation benefits provided by these areas for mobile species.

Invasion of the golden mussel (Limnoperna fortunei) into Brazilian watersheds is still impacting energy production and aquaculture after 30 years of establishment. No control attempts have been effective and even monitoring is limited by costs and accessibility to the areas. In this context, we propose an approach that integrates traditional monitoring tools with an artificial intelligence (AI) program developed using convolutional neural networks (CNN), with the aim to identify and quantify golden mussels in two Brazilian watersheds, Paraná and São Francisco. In the latter, we conducted an additional 7-month temporal evaluation using recruitment plates. Neural networks can assist in species identification in complex environments, facilitating population monitoring and biodiversity assessment. In our study, the AI program had 85–98% accuracy compared to human measurements, demonstrating a high success rate for autonomous assessment. Independent of individual mussel size, the best feature for golden mussel detection was valve aperture. This study provides a valuable quantitative and methodological baseline regarding golden mussel infestation in Brazil, highlighting the efficiency and cost-effectiveness of the AI program for monitoring this invasive species. This technique is easily replicable and scalable, with a great potential to facilitate the work of researchers and environmental agencies worldwide as an additional tool to combat the spread of invasive species.

We evaluated the influence of hydrological phases and limnological variables on the taxonomic composition and functional diversity of fish associated with aquatic macrophytes in a floodplain lake of Amazon Basin, Brazil. Sampling was conducted using seine nets across the four phases of the local hydrological cycle (rising, high-water, receding, and low-water) during the year 2018 in Lake Maicá. The species were identified and classified into four functional groups on the basis of their ecological traits (migration, life history strategy, feeding habits, and swimming performance/microhabitat use). A total of 6075 individuals were captured, representing nine orders, 26 families, and 104 species. The fish assemblages underwent changes in both taxonomic and functional structure in response to the hydrological phases and limnological variables (pH, temperature, dissolved oxygen, and water transparency), with an increase in functional diversity during the receding water and low-water phase. During the low-water period, there was an increase in the abundance of fish with life history strategies at equilibrium, small periodic species as well as invertivores, piscivores, short-distance migrants, and residents. In contrast, the rising and high-water phases contributed to higher abundances of young fish (larvae and juveniles) and medium-distance migratory fish. The synergy among these factors acts as an environmental filter in the structure of the local ichthyofauna, allowing species with antagonistic ecological traits to coexist, maintain their populations, and reduce competition for space and food under varying environmental conditions during the four phases of the annual hydrological cycle. The information presented is essential for identifying priority areas for the conservation of fish assemblages, which represent the primary source of animal protein and income for the region, and for understanding the mechanisms responsible for changes in the taxonomic and functional structure of fish in Amazonian floodplain lakes.

The white-clawed crayfish (Austropotamobius pallipes complex) is a crucial species complex in European freshwater ecosystems, but its population has faced severe declines since the 1860s due to pollution, habitat loss and fragmentation. The introduction of invasive crayfish species that carry the crayfish plague (Aphanomyces astaci), a water mold, has exacerbated this decline. The Avigliana Lakes Nature Park in Piedmont, Italy, which encompasses the Great Lake, Small Lake and Mareschi wetland, has been designated a Natura 2000 site supporting A. pallipes, particularly in the tributaries of the Small Lake. The aim of this study was to assess both the presence and distribution of A. pallipes in the study area and the physicochemical and ecological characteristics of its habitats. We also evaluated the proximity of invasive crayfish Procambarus clarkii populations to A. pallipes to further current understanding of potential health impacts and support management efforts. Macroinvertebrate monitoring was used to gauge overall ecosystem health and habitat suitability for A. pallipes. The results showed that A. pallipes was present at only two out of the six monitored sites, with no visible signs of disease. Macroinvertebrate monitoring indicated good water quality, while significant differences in pH, conductivity, and nutrient levels were found. Canonical correspondence analysis highlighted key environmental factors for A. pallipes, including conductivity, total dissolved solids, and vegetation. The lack of evidence for crayfish plague within the P. clarkii population may enable more effective management strategies and reduce potential health risks to the A. pallipes population. This study emphasises the need for ongoing monitoring and targeted management to mitigate invasive species’ impacts and conserve native crayfish populations.