Aquatic Sciences最新文献

Understanding the age structure and growth patterns of freshwater bivalve species is crucial for their conservation, and these data are still lacking for many species and locations. The main objective of this study was to gain insight into the age structure and growth patterns of the endangered mussel Unio crassus at the unpolluted and polluted sites on the Mrežnica River (Croatia), as well as construct the first-ever chronology for this species. Bivalve sampling was carried out in July 2020. The age and growth dynamics were determined by analysing internal growth lines in acetate peel replicas of shell cross sections. The length range of shells from the unpolluted station was 4.5–5.6 cm, with an estimated age range of 10 to 29 years, whereas shell length at the polluted site was 5.2–6.1 cm, with an estimated age range of 10 to 22 years. Our results indicate that industrial pollution may influence life strategies in U. crassus populations, with mussels growing faster and living shorter at polluted site. Compared to other parts of Europe, the estimated ages obtained in our study were the most similar to those in central Europe. According to growth curves, mussels grow the fastest during their first 10 years, after which their growth significantly slows down. Growth chronologies were constructed by measuring growth increments in acetate peels of shell cross-section, and some correlations between shell growth and environmental parameters have been observed, indicating the potential for further sclerochronology research on this species.

Livestock grazing is a major economic activity worldwide. Cattle frequently graze and congregate in watercourses and riparian areas because of the availability of water, shade and the quality and variety of forage, thereby altering the ecological condition of stream ecosystems. We have explored the effects of cattle intrusion on the environmental conditions and fish assemblages of four neotropical prairie streams from Argentina’s Pampas region. At each stream, both ungrazed and grazed conditions were surveyed. Water quality, habitat structure, riparian vegetation and fish assemblages were sampled. Significant detrimental changes were observed in environmental conditions of grazed sites in contrast to ungrazed sites. Fish assemblage structure and function were also significantly influenced by the environmental conditions imposed by cattle intrusion. Our results reveal the magnitude and direction of environmental changes imposed by cattle intrusion in prairie streams and highlight several key aspects of fish assemblages and populations that change accordingly. Relevant aspects for conservation and management purposes of these fragile ecosystems, such as protection of riparian vegetation condition and the control of cattle access and social engagement, are discussed.

Streams and ponds provide several ecosystem services but are threatened by anthropic activities. Studies on species contribution and local uniqueness are ways of analyzing sites that need conservation or restoration due to anthropic activities. These metrics are especially important when evaluating Amazonian environments, which are complex and understudied. In this study, we investigated the relationships between the local contribution (LCBD) and the species contribution (SCBD) to beta diversity and community attributes for zooplankton in Amazonian streams and ponds, and those between the land use change and local environmental factors on the LCBD (total, replacement, and richness difference). Additionally, we investigated whether sites with ecological uniqueness should be considered for conservation or restoration. We sampled zooplankton, macrophytes, and physical–chemical variables in 42 streams and 26 ponds in 2022. We also determined land use and land cover through digital image processing and calculated the Catchment Disturbance Index (CDI). A total of 130 taxa, comprising 76 rotifers, 41 cladocerans, and 13 copepods, were recorded. The zooplankton SCBD was positively correlated with species occurrence and abundance of individuals, while the LCBD was negatively related to abundance and species richness. In streams, total-LCBD was positively related to CDI and negatively related to macrophyte cover; in ponds, no significant relationship was observed. Our results improve current understanding of the effects of land use changes on zooplankton beta diversity, showing that more altered sites have unique and poor species composition and need restoration. Our data also increase knowledge on zooplankton in Amazonian environments, especially in streams that are understudied.

The subterranean environments of the Caatinga drylands (Brazilian biome) host a diverse array of aquatic systems and diversity, comprising both lentic and lotic ecosystems. Species diversity in these environmnts has been overlooked and remains poorly understood, especially regarding zooplankton. We studied the species richness and composition of zooplankton living in groundwater of the Caatinga drylands and explored how they vary in relation to habitat type (lentic and lotic) by testing two hypotheses: (1) species richness, gamma diversity, and zooplankton density are higher in lentic environments and (2) zooplankton species composition differs between habitat types. We sampled 12 lentic and lotic groundwater environments quarterly for 2 years, and identified 100 species of zooplankton in groundwater environments, including testate amoebae (50 species), Rotifera (25 species), Copepoda (16 species), and Cladocera (9 species). Rotifer species richness and copepod density differed between lentic and lotic habitats, as did zooplankton composition. Additionally, each habitat was found to harbor distinct indicator species based on their ecology and morphological characteristics. These findings contribute to current understanding of groundwater biodiversity and ecology, providing support for freshwater and speleological management and conservation programs.

Glyphosate, a herbicide widely used in agriculture, has adverse effects on aquatic ecosystems. This study aimed to assess the repercussions of in-vitro exposure to varying concentrations of glyphosate (1500, 3000, and 6000 μg l⁻¹) on  sporulation of fungi that colonize Typha latifolia (L.) leaves. Although the results were not significant, our bioassay revealed a trend of a 50% increase in fungal sporulation at lower glyphosate concentrations compared to the control, with an effect size of approximately 100%. Thirteen aquatic fungi taxa were identified, belonging to the phylum Ascomycota. Amniculicola longissima (Anguillospora longissima) was dominant among fungi associated with decaying leaves, exhibiting a tendency of decreased sporulation rate at higher glyphosate concentrations. Conversely, Brachysporium sp. demonstrated significantly higher spore abundance at the lowest herbicide level. Some fungal taxa, such as Cordana sp., exhibited an inhibition of sporulation rates in the presence of glyphosate. On the other hand, Curvularia sp. and Sporidesmium sp. were only found in treatments with glyphosate concentrations > 3000 ppm. These findings underscore the potential adverse effects of glyphosate on sporulation of some aquatic fungi, pivotal microorganisms that are considered key in the decomposition of organic matter in aquatic ecosystems and consequently in water self-purification processes. Hence, it is plausible that this herbicide alters the dynamics of decomposition, modifying the recycling of organic matter and thereby influencing the trophic networks of aquatic ecosystems. These results represent a preliminary investigation that establishes a baseline to understand the effect of glyphosate on aquatic fungi, a topic that has been poorly studied.

Graphical abstract

Different catchment land uses affect stream communities through direct and indirect effects by changes in water flow, sediment input, channel physical structure, and productivity. Previous studies of land use effects show a wide variation in the size and direction of biodiversity responses with positive, negative, or even no effects of the loss of native vegetation in catchments. This variation can result from physiographic characteristics, such as the original type of native vegetation (grassland or forest), dominant land use (agricultural or urban), history of change in land use and land coverage (LULC), and climate, and/or from the specific design of each study, such as the range of the analyzed LULC gradient. We performed a meta-analysis of 62 studies using stream macroinvertebrates and fish to determine which of these factors influence the biodiversity responses to changes in LULC. Contrary to our expectation, most of the physiographic factors considered relevant in the literature did not influence the response of macroinvertebrates and fish to land use. We did find, however, that studies with greater ranges of changes in LULC show stronger and the most negative diversity responses for macroinvertebrates. This suggests that studies covering a small gradient in LULC may be unable to detect potentially minute negative impacts on macroinvertebrate diversity. Our results highlight that the response of stream fish and macroinvertebrate diversity to changes in the landscape is context dependent. We suggest that the local environment of study sites and other context-dependent factors should be further investigated to better understand environmental contingencies in stream biodiversity responses.

Lake Baikal, an ancient, massive lake in Siberia that holds 20% of the world’s fresh water reserves, is a unique center of speciation. Changes in the lake’s ecosystem in recent years require comprehensive monitoring activities to track the continuously evolving situation. Sponges are bioindicators of the state of aquatic ecosystems, and in Lake Baikal sponges are represented by both cosmopolitan and endemic species. However, the study of intra- and interspecific relationships between endemic sponges is complicated by the fact that standard molecular genetic markers are not suitable for these purposes. In this regard, the search for suitable high-resolution molecular genetic markers is especially relevant. Here we report on the development of a set of universal microsatellite markers that allows the interspecific relationships between Lake Baikal endemic sponges to be studied. We tested the effectiveness of this set of microsatellite markers on representatives of four endemic sponge species and achieved a reliable separation of representatives of all four genera of the endemic sponge family Lubomirskiidae. This is the first report of a set of highly variable molecular genetic markers that has been developed specifically for the study of interspecific relationships between Lake Baikal sponges. This set also has the potential to be a marker for species identification, which is important for monitoring activities in connection with events of mass death and diseases of sponges in Lake Baikal. The described approach can be used to study endemic sponges from other ancient lakes. It has great potential for use in the development of universal markers for identifying groups of closely related species.

The anadromous European smelt (Osmerus eperlanus) plays a key role in food webs of many riverine ecosystems in Europe. However, population sizes in several German rivers (e.g. Elbe or Weser rivers) have diminished drastically over the past decade. Turbidity has been considered one of the stressors affecting the successful recruitment of European smelt, as their early life stages may be particularly sensitive to changes in the abiotic environment. In this study, we investigated whether prey consumption and survival of European smelt larvae would be negatively affected by an acute exposure to elevated turbidity. We reared the larvae in the laboratory and exposed them in four separate trials (18 to 26 days post hatch, 9.5 ± 0.8 mm standard length, mean ± SD) to six turbidity levels (0–500 NTU, nephelometric turbidity units). We found that prey uptake increased at low turbidity levels and decreased at high turbidity levels, with an optimum between 100 and 200 NTU. Survival started to decrease at turbidity levels above 300 NTU. In addition, we conducted a systematic literature analysis in which we found that prey consumption of larval and juvenile fishes had been tested across a wide range of turbidity levels, mostly using pelagic (e.g. planktonic) prey items, with more studies focusing on perciform fishes and juvenile rather than larval life stages. Our empirical findings contribute to establishing thresholds for optimal larval European smelt performance under increased turbidity and provide valuable information for developing mechanistic models that assess potential consequences for European smelt recruitment dynamics.

We used an extensive multispecies dataset to examine how C and N stable isotope ratios (δ¹³C and δ¹⁵N) of aquatic consumers varied with body size in populations of northern lakes. Ontogenetic variation in tissue δ¹³C and δ¹⁵N was evident in a diversity of aquatic consumers. Relationships with body size tended to be stronger and more consistently positive for δ¹⁵N, and more variable in nature for δ¹³C. Among-population variation in ontogenetic slopes was greater for δ¹³C than for δ¹⁵N for most biota examined. Relationships between δ¹³C and δ¹⁵N and body size were still significant even after accounting for variation owing to tissue C:N and body condition. Ontogenetic variation was more strongly linked to age than body size in some fishes, particularly for δ¹⁵N, but age effects, inferred from growth rate, also accounted for variation in δ¹³C and δ¹⁵N beyond body size effects; δ¹³C tended to be positively related and δ¹⁵N tended to be negatively related to growth rate. There was only limited evidence of concordance in ontogenetic slopes between co-habiting pairs of species, suggesting that the factors driving ontogenetic variation in stable isotope ratios may be largely species- or population-specific. However, ontogenetic slopes of individual taxa were related to various lake habitat features representing climate, ecosystem size, and water clarity. The proportion of isotopic niche space attributable to ontogenetic variation can be substantial and this has implications for applying and interpreting isotopic niche metrics. Our study provides the broadest and most comprehensive analysis of ontogenetic variation in isotopic compositions of freshwater consumers to date and our results underscore the need to account for this variation in the analysis of freshwater food webs.

The present study provides complementary information on the harmful algal bloom (HAB) species present in Manori Creek coastal water and tidal channel. A total of 67 HAB species representing 35 genera and 7 taxonomic class groups were identified. Among them, 27 were potentially toxic, while 45 had the potential to form harmful algal blooms. Notable blooms included Chaetoceros socialis in April (8.9 × 10⁵ cells l⁻¹) and May (3.9 × 10⁵ cells l⁻¹), Nitzschia palea in May (4.37 × 10⁶ cells l⁻¹) and June (1.1 × 10⁵ cells l⁻¹), and Coscinodiscus radiatus in (2.7 × 10⁵ cells l⁻¹) in January. The marine ciliate Mesodinium rubrum exhibited bloom formation in May (1.33 × 10⁵ cells l⁻¹) at all stations in Manori Creek. Canonical correspondence analysis revealed that the proliferation of HAB species was facilitated by optimal temperature, salinity, and nutrient levels in creek water. Dinoflagellates responsible for paralytic shellfish poisoning (PSP) and diarrhetic shellfish poisoning (DSP) were rare and found in low abundance. Toxin assessment results, based on the mouse bioassay, revealed that Gafrarium divaricatum samples contained paralytic shellfish toxin (PSP toxin) levels < 0.875 mouse units (MU) per 100 g of clam tissue. The test mice exhibited normal fecal consistency, indicating the absence of high levels of diarrhetic shellfish toxin (DSP toxin). The present study recorded HAB species variability and potential toxin accumulation within G. divaricatum in Manori Creek. The data generated from the creek serve as a pivotal base for the advance monitoring initiatives focused on HAB species and their associated toxins within the creek ecosystem.