Aquatic Sciences最新文献

This study focuses on the population genetics and historical demography of the hawksbill sea turtle (Eretmochelys imbricata) in the Persian Gulf. We selected eight distinct locations along its nesting habitat, covering a 750-km stretch of coastline, and collected 127 maternal DNA samples in one season using non-invasive methods. The samples were analyzed using 15 microsatellite loci, revealing distinctive genetic structures on islands and beaches, even when between locations as little as 50 km apart. The highest genetic diversity was observed for Qeshm Island, while lower genetic diversity was observed for Shidvar and Kharkoo islands and for Nayband Bay, possibly due to limited nesting habitat availability and disturbances related to tourism. The fixation index (F_ST) and gene flow parameter (N_m) values also identified population differentiation, with moderate to high differentiation observed among most populations. We also used population structure analysis, migration analysis, and population history reconstruction to identify multiple genetic clusters, and obtained support for a scenario of simultaneous dispersal in the Persian Gulf when the region became fully inundated with water approximately 10,000 years ago. Although the first introduction of hawksbill sea turtles into the Persian Gulf occurred from the Oman Sea through the Strait of Hormuz, they were distributed in all current habitats within a short time. The study emphasizes the importance of each coastal and island region in the Persian Gulf as a distinct genetic reservoir for hawksbill turtles. It also underscores the significance of conservation efforts to protect the genetic diversity and resilience of these endangered marine turtles, especially on nearby islands.

Four serpentinization-driven hyperalkaline springs (HAS) in the Jurassic ophiolites of western Serbia, with pH values between 11.1 and 11.7, were selected to assess the lignocellulose- and plastic-degrading potential of cultivable bacteria found in both the groundwaters and sediments of the zone of emergence of the investigated occurrences. Also, the physico-chemical properties of the groundwaters and petrological and mineralogical composition of sediments were examined. The HAS investigated are cold (temperature: 14.7–19.4 °C) and low in minerals (total dissolved solids: 104.1–450.4 mg/L) and belong to the Ca²⁺–OH⁻ and Ca²⁺, Na⁺–OH⁻ genetic type. Ca²⁺ was the most abundant cation (39.7–132.7 mg/L), followed by Na⁺ (2.0–82.5 mg/L) in three and Mg (6.6 mg/L) in one HAS, respectively. OH⁻ was the most abundant anion (24.6–123.2 mg/L), followed by CO₃²⁻ (18.0–36.2 mg/L) and Cl⁻ (12.4–71.0 mg/L) in all tested groundwaters. Binocular examination revealed that gravelly spring sediments consist predominantly of peridotite, serpentinite, carbonate and quartzite clasts, while the powder X-ray diffraction experiments identified calcite and lizardite as the main mineral phases in the silt fraction. In total, 210 groundwater and sediment isolates were screened on lignocellulose and plastic substrates, and 33.8% of all screened HAS isolates (9.1% from groundwaters and 38.4% from sediments) degraded carboxymethyl cellulose. Selected bacterial isolates were identified by partial 16S ribosomal DNA sequencing to belong to the genera Bacillus, Peribacillus, Paenibacillus and Lysinibacillus; these could have potential applications in various commercial sectors requiring cellulose degradation. All identified isolates demonstrated growth on the plastic substrates Impranil® DLN-SD (SD) and Impranil® DL 2077 (DL), while three isolates, belonging to genera Bacillus, Peribacillus and Paenibacillus, respectively, demonstrated growth on all four tested plastic substrates (SD, DL, polycaprolactone diol and bis(2-hydroxyethyl) terephthalate). These isolates should be further explored as potential candidates for bioremediation treatments of plastic-polluted groundwaters and sediments.

Carbon pathways in freshwater ecosystems are particularly complex because of the multiple origins, forms, and transformations of carbon by aquatic organisms. In high-altitude lakes, located above the treeline, most of the carbon pool is of indigenous origin. However, little is known about the influence of lake and watershed characteristics on carbon transfer pathways and their variability over an annual cycle. We analyzed simultaneously carbon stable isotopic composition (δ¹³C) and C/N ratio of organic matter from pelagic (POM, zooplankton) and benthic components (benthic invertebrates, sediments) in eight high-altitude lakes and hypothesized that the origin of the carbon used and the composition of organic matter in the pelagic and benthic compartments vary according to the lake’s characteristics. The results showed that most of the organic matter composing the sediments is of autochthonous origin, regardless of the lake’s characteristics. We observed a common tendency of seasonal shift in the source of carbon used, from a C–CO₂ respired or a C–CH₄-derived in early summer to a C–CO₂ dissolved in late summer. However, the origin of the carbon used and the contribution of pelagic and benthic primary producers to the carbon transfers varied according to the lakes’ depth, lithology, and food web structure. These findings highlight that the complexity of high-altitude lakes and how the balance between benthic and pelagic food webs will be important in future ecological trajectory predictions.

The escalating pace of dam construction in Brazil poses a significant threat to migratory fish. This study uses data from previous research to predict the impacts of new dams on the life cycle of the migratory fish Prochilodus costatus. The species was studied for five reproductive seasons in a 500-km free-flowing stretch of the São Francisco River, where the construction of six hydroelectric dams is now planned. These studies investigated migratory periods, routes, critical habitats, and the genetic structure of the P. costatus population, assessing potential impacts of the planned dams and exploring various mitigation strategies. The assessment shows that maintaining this river stretch free of dams is crucial for the species’ survival. The comparison of this in-depth analysis with information generated by conventional environmental impact assessments (EIAs) conducted in Brazil revealed that conventional EIAs often fail to predict the actual impacts of dam construction as they rely on inadequate collection and analysis methods. Therefore, the proposed mitigating measures prove inefficient for migratory fish. Our comparison highlights the importance of obtaining essential information about the ecological requirements of migratory fish and integrating it with the characteristics of newly planned dams before determining their environmental feasibility. We thus propose an integrative approach to assess the impact of dams on Neotropical migratory fish (IANMF), aimed at providing researchers and environmental agencies with higher quality information on migratory fish ecology and the potential impacts of future dams on their life cycles.

Agricultural land use effects on aquatic and riparian communities are complex and multifaceted, resulting in habitat degradation and biodiversity loss in riparian and instream ecosystems. This study correlated predatory arthropod densities and species richness to abundance of potential prey (emerged aquatic insects and terrestrial dipterans) along an agricultural to forested land use gradient. Pearson’s correlation coefficient was used as an effect size to measure attraction to prey, and the ratio of predator to prey was calculated to indicate potential consumption capacity of prey. Results revealed that gradients in land use and microhabitat condition, distance from the stream and season were important explanatory factors. Positive correlations between predatory arthropods and aquatic insect abundance were more apparent than those with terrestrial dipteran abundance, suggesting an overall preference of aquatic prey. However, positive correlations between predatory arthropods and adult aquatic insect subsidies were strongest in microhabitats with characteristics associated with higher moisture (e.g., greater soil organic matter and shade), particularly with increasing agricultural land use. In September, there was an indication of reduced confinement to microhabitats, likely as an effect of elevated seasonal precipitation. Overall results of this study suggest that a limited tolerance to desiccation in predatory arthropods increases spatial confinement with agricultural land use and ultimately restricts access to adult aquatic insect subsidies. The findings of this study have implications for the pathways that adult aquatic insect subsidies use to enter into riparian food webs with consequences that could cascade across trophic levels and larger spatial scales.

Climate change is one of the main drivers of biodiversity decline. Rapidly changing climate in the form of warming, drying, and habitat isolation causes freshwater species to change their spatial extent, as most species have little capacity for in situ responses. However, the relative contribution of these three effects to freshwater species’ changing spatial distributions is actively debated. To shed light on this debate, we explored temperature, hydroperiod, and habitat connectivity effects on alpine pond species occupancy probabilities in the northern French Alps. We studied alpine ponds as ideal test systems because they face climate change effects more rapidly, and in more concentrated areas, than any other freshwater ecosystem. We used multispecies occupancy models with three biological groups (amphibians, macrophytes, and Odonata) to examine contrasting responses to climate change. Contrary to expectations, temperature was not the main driver of species occupancy probabilities. Instead, hydroperiod and connectivity were stronger predictors of species occupancy probabilities. Furthermore, temperature increases had the same effect on occupancy probabilities of non-alpine specialist and alpine specialist species. Nonetheless, temperature disproportionately affected a greater number of specialist species compared with non-alpine specialists. We conclude that climate change mitigation will primarily benefit a greater number of alpine specialist species than non-alpine specialists. Finally, we suggest that enhancing our understanding of freshwater hydroperiods will improve our predictions of climate change effects on freshwater species distributions.

New Jersey coastal areas are experiencing eutrophication due to human-induced nutrient overloading. Algal blooms occur frequently in New Jersey coastal waters, and excessive blooms shift water quality. However, phytoplankton–bacteria interactions mediated through dissolved organic matter (DOM) have not been extensively studied in New Jersey coastal waters, especially near overburdened communities. We targeted a traditionally underrepresented township area, Keyport Harbor, as a model site to investigate seasonal variabilities of phytoplankton biomass, DOM, and bacteria biomass. Chlorophyll-a concentrations were significantly higher in spring–summer (bloom) than in fall–winter (nonbloom). Nitrate + nitrite and ammonium were negatively correlated with chlorophyll-a, and the water was nitrogen-limited during bloom time while phosphorus-limited during nonbloom time, implying that regulating nitrogen loading was key to controlling algal blooms, especially during bloom seasons. Phytoplankton–bacteria interactions were assessed by monitoring dissolved organic carbon (DOC) and bacterial abundance between bloom and nonbloom time from field and incubation studies. A significantly higher DOC, but not dissolved organic nitrogen, occurred in the bloom than nonbloom period, suggesting that phytoplankton contributed to the production of more carbon-rich than nitrogen-rich compounds. DOC fueled threefold bacterial growth in the bloom period, exceeding the temperature effect and indicating strong phytoplankton–DOM–bacteria connections. Microbial remineralization incubations showed rapid phytoplankton–DOC drawdown, and more ambient DOC drawdown and bacterial growth in the bloom than nonbloom time, further supporting the important role of phytoplankton–DOC in shaping bacteria. With water quality monitoring via chemical and biological indicators, the study aimed to understand carbon cycling better, assess anthropogenic impacts on coastal environments, and help facilitate coastal management.

Barium (Ba) is a naturally occurring alkaline earth metal that is mined and used for industrial purposes. This earth metal can easily impact organisms commonly found in coastal zones, particularly marine bivalves, through aquatic discharges resulting from industrial activities. The aim of the present study was to assess the potential toxic effects of barium chloride (BaCl₂) on fatty acid profiling, redox status, and histopathological aspects of Ruditapes decussatus gills exposed to a range of concentrations (0, 20, 40, and 80 mg/L) for 5 days. Our results revealed that BaCl₂-treated clams had altered levels of saturated fatty acids, decreased content of monounsaturated fatty acids, and increased levels of polyunsaturated fatty acids. Alterations in arachidonic acid were also observed in the gills of treated specimens, accompanied by significant increases in its precursors: linoleic and α-linolenic acids. Our findings also showed changes in the levels of eicosapentaenoic and docosahexaenoic acids. These results indicated a bioaccumulation of Ba, as evidenced by a significant increase in Ba levels in BaCl₂-treated specimens. BaCl₂ exposure increased the levels of hydrogen peroxide, lipid hydroperoxide, malondialdehyde and protein carbonyl along with enzymatic (glutathione peroxidase and glutathione s-transferase) and non-enzymatic (reduced glutathione, non-protein thiols, metallothioneins, and vitamin c) antioxidants. Moreover, our data showed a decrease in ferric-reducing antioxidant power, superoxide dismutase, and catalase. The outcomes of the biochemical findings were confirmed by histopathological injuries. Our investigation underscores the significance of fatty acid composition as an early sensitive biomarker for elucidating the toxicity mechanisms of BaCl₂ in aquatic bivalves, and highlights the broader implications of BaCl₂ contamination in coastal ecosystems, emphasizing the need for monitoring and mitigation strategies. By demonstrating the link between oxidative stress and fatty acid profile disruptions, our findings provide valuable insights into the environmental impact of BaCl₂ and underscore the importance of continued research into its effects on marine life.

Biofilms are hotspots of metabolism in streams. A common natural and anthropogenic disturbance in lotic systems is the input of nutrient-rich sediments, which may affect the stream bottom and thereby biofilms. Here, we present an indoor experiment with artificial channels to test the effect of phosphorus (P) and abrasive sediment inputs on biofilm structure. The experiment had a factorial design with four treatments: (1) without any addition (treatment C); (2) addition of abrasive sediments (treatment G); (3) phosphorus addition (treatment P); and (4) addition of abrasive sediments and phosphorus (treatment GP). Our results showed that the addition of phosphorus alone (treatment P) increased biofilm biomass (increased both chlorophyll-a and carbon [C] content), while the addition of sediment had a strong negative effect on biofilm biomass and elemental ratios (C:nitrogen [N] and N:P), both when added alone (treatment P) and when added with P addition (GP). The P addition treatments (P alone and GP treatments) resulted in a decrease in alkaline phosphatase activity. At the end of the experiment, we observed a shift in the primary producers: while P treatments were dominated by Cyanobacteria, both the G and C treatments were dominated by diatoms. In particular, the G treatment, where the biofilm was composed of a thin layer of diatoms, exhibited the highest photosynthetic efficiency (highest electron transport rate and photosystem II efficiency). The final balance of the input of abrasive sediments with P enrichment resulted in a young-stage biofilm with a high proportion of extracellular polymeric substances. These results highlight the effects of combined stressors since abrasive sediments even at high P levels can severely affect both the structural and physiological parameters of biofilms.

Acoustic deterrence has been proven instrumental in preventing fish invasions and safeguarding against fish ingress into hydro-turbines, with the systems often employing broadband sounds, such as boat noises or predator vocalizations. However, within these broadband sounds, the specific frequencies that elicit negative phonotaxis (avoidance behavior) in fish remain to be identified. The present study investigated the avoidance behavior of grass carp shoal in sound playback experiments conducted using pure tones within the frequency range of 100–1500 Hz and two broadband sounds. The alligator roar sounds, a known deterrent, were used as broadband sound 1, which was also manipulated to remove high-sound-pressure-level components, creating a novel broadband sound 2. Grass carp exhibited significant overt avoidance behavior and increased swimming speed in response to the 100 Hz pure tone. Under the effect of this tone, the number of avoidance responses over a 10-min experimental duration (8.14 ± 1.44 min) was significantly higher than that recorded in the control group (H = 34.929, P < 0.05). These findings suggested that the low-frequency components in broadband sounds are essential to eliciting avoidance behaviors in fish. The present research offers novel insights into the strategic selection of sound frequencies in acoustic deterrence systems, facilitating the development of further precisely targeted and effective fish management strategies.