Aquatic Sciences最新文献

Floodplains are habitats with an outstanding biodiversity but have been strongly affected by anthropogenic activities such as channelization and bank enforcement. The remaining floodplains are impacted by climate change-driven alterations in the hydrological regime and by chemical stressors. However, the extent and interactive effects of these stressors are not well understood, especially in small-scale floodplains. In a mesocosm experiment, we therefore studied aquatic and riparian (floodplain) invertebrate communities in response to changes in the hydrological regime as predicted by climate change and the application of the biocide Bacillus thuringiensis israelensis (Bti). The mesocosm facility contained 12 separated floodplain mesocosms. The control hydrological regime consisted of a 40-cm water level and one monthly flood throughout the year, while the altered hydrological regime (scenario) had weekly floods during winter and a lower water level during summer. In addition, half of both the control and scenario floodplain mesocosms were treated with Bti at the maximum field rate applied for mosquito control. We found that the hydrological regime had contrasting effects for the aquatic and riparian communities. While the number of individuals of most aquatic invertebrates decreased in the scenario floodplain mesocosms, we found predominantly higher number of individuals of riparian arthropods. Furthermore, Bti had negative effects on some nontarget organisms, such as ground beetles and mayflies, and interacted with the hydrological regime in some cases. We conclude that the effects of both hydrological regime and Bti are taxa-dependent and that the hydrological regime revealed opposing effects between aquatic and riparian habitats.

Global blue carbon assessments are hindered by a lack of data from understudied seagrass regions, such as those of Western Africa. This study reports the first in situ records of organic carbon (OC) stocks and burial rates for seagrass beds at Arguin Island, Banc d'Arguin (Mauritania), Western Africa, measured in intertidal Zostera noltei and subtidal Cymodocea nodosa meadows. The major blue carbon sources in seagrass meadows since 1900 were assessed using sedimentary environmental DNA (eDNA) and chronostratigraphy. The OC stocks in the top 50 cm of the sediment cores were not significantly different between the beds of the two seagrass species and averaged 27.8 ± 7.14 Mg C ha⁻¹, which is 5 times higher than that in adjacent unvegetated sediments. The OC sequestration rate for the past 100 years was 10.3 ± 1.4 g C m⁻² year⁻¹ in C. nodosa sediments and 12.3 ± 5.9 g C m⁻² year⁻¹ in Z. noltei sediments. Sedimentary eDNA analysis revealed that the major OC source within the C. nodosa and Z. noltei sediments has been the seagrass species itself, with low contributions from allochthonous eDNA reads. Carbon sources in Z. noltei meadows were more diverse than those in C. nodosa meadows. In bare sediment, diatoms were the major carbon source. The present study demonstrates the potential of sedimentary eDNA to reveal the major sources of organic matter in blue carbon ecosystems, improving our understanding of the provenance of sedimentary OC and thus carbon cycling processes. Additionally, it provides new OC stock and sequestration rate measurements from a region of the world that remains underrepresented in global blue carbon assessments.

Mud crabs (Scylla serrata) play crucial roles in coastal ecosystems, and their intestinal microbiota might be greatly affected by the habitats. Illumina NovaSeq sequencing was used to identify the intestinal microbiota of wild S. serrata and the microbiomes in ambient water and sediment in the Koggala lagoon of Sri Lanka. The study found significant differences in the microbiota of mud crab intestines, lagoon water, and sediment. The microbial communities in lagoon sediment and water were richer and more diverse than those in the crab intestine, exclusively detecting 90.66% of microbes in the intestinal microbiota. The lagoon water and sediment showed distinct planktonic and sediment microbiota, with 96.08% and 90.13% differences, respectively, while only 2.8% of classified intestinal microbes, including Photobacterium, Carboxylicivirga, Acinetobacter, Clostridium sensu stricto 1, Desulfovibrio, Bacillus, and Bacteroides could be detected in the water and sediment. Even if its proportion is small, Photobacterium damselae subsp. damselae is a known pathogen, particularly in marine environments and aquaculture. However, the genomic analysis in this study revealed factors that do not contribute to pathogenicity, suggesting that P. damselae subsp. damselae is not pathogenic to S. serrata in Koggala Lagoon. Notably, Vibrio, Shewanella, Stenotrophomonas and Desulfovibrio exhibit a greater propensity to colonize the intestine of S. serrata. The planktonic and sediment microbiota might play an essential role in biogeochemical cycling, especially in nitrification, carbon, and sulfur cycling. Furthermore, harmful Cyanobium, has been detected in the intestine of S. serrata and lagoon water and sediment habitats, might have adverse effects on the ecosystem and human health. Based on the chloroplast 16S rRNA gene sequences, the terrestrial plant materials found in the intestine of S. serrata suggest less herbivorous feeding habits. Our results could provide implications for the effective management of the mud crab, S. serrata in its natural habitat.

Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) are key participants in the nitrogen cycle in freshwater ecosystems. However, the seasonal dynamics of AOA and AOB communities in floodplain lakes are unclear. Here, on the basis of the high-throughput sequencing and quantitative polymerase chain reaction (PCR) of the ammonia monooxygenase (amoA) gene, we investigated the diversity, abundance, and community structure of sediment AOA and AOB in wet, mid-dry, and dry seasons in Poyang Lake, the largest floodplain lake in China. The results revealed that the AOA and AOB communities were subject to substantial seasonal variations. Specifically, the three seasons shared only 14.4–28.3% and 17.4–25.2% of the total operational taxonomic units (OTUs) for each AOA and AOB community, respectively. Permutational multivariate analysis of variance (PERMANOVA) and principal component analysis (PCA) further indicated that the community structure of both AOA and AOB differed significantly among seasons. In addition, the season exerted a marked influence on the alpha diversity of AOA but not that of AOB. The season did not significantly impact the abundance of either AOA or AOB. Total nitrogen (TN) and total phosphorus (TP) were significantly related to the AOA community structure in the lake sediments, while organic matter (OM) was significantly associated with the AOB community composition. Our research demonstrates that there are seasonal variations in AOA and AOB communities in floodplain lake sediments, highlighting the impact of seasonal water level fluctuations on the nitrification process within such habitats.

Microplastic (MP) pollution is an escalating environmental concern with comprehensive implications for aquatic ecosystems and their inhabitants. Understanding the intricate relationship between MPs and macrobenthos is paramount for grasping the full extent of environmental degradation within aquatic ecosystems. As MP pollution proliferates, its repercussions for macrobenthic communities including poriferans, corals, aquatic arthropods (Daphnia, crabs, and shrimps), mollusks (unio and mussels), and echinoderms (starfish and sea cucumbers), has become increasingly evident. This review delves into the multifaceted impacts of MPs on macrobenthos, shedding light on the ecological disruption, behavioral alterations, and potential cascading effects throughout marine and freshwater environments. From tropical reefs to freshwater rivers, sponge tissues exhibit escalating levels of MP contamination over time, reflecting the extensive bio-accumulative potential of these organisms. By studying and exploring the effects of MPs on poriferans with a comprehensive examination of existing literature, it becomes evident that MP exposure induces adverse effects including impaired feeding, increased mucus production, altered gene expression, and coral bleaching. Nanosized polystyrene (PS)-MPs delayed the developmental time and downregulated Usp gene expression in Tigripous japonicus. In mollusks, studies revealed diminished filtration rates and altered energy reserves in bivalves exposed to MPs, accompanied by oxidative damage and compromised activity of digestive enzymes. MP exposure leads to various developmental defects such as larval morphological alteration and a size-dependent impact on the larval growth and development of echinoderms. The mechanisms underlying MP-induced toxicity across various phylum are discussed, highlighting the urgent need for further research to elucidate their cumulative impacts on organismal health and fitness.

The high Andean páramos (biomes above the treeline, ranging from 3000 to 5000 m a.s.l.) are ecosystems that have long been threatened by human activities, impacting their ability to store water. In Ecuador, the wetlands within these páramos have been drained for cattle ranching and agriculture. One notable example is the Pugllohuma wetland, an important water reservoir for the city of Quito, which is in a recovery process. The objective of this study was to assess the influence of different types of restoration processes on the diversity and community structure of aquatic invertebrates in the Pugllohuma wetland. To evaluate this influence, three sampling campaigns were conducted in five ponds subjected to active restoration and five ponds subjected to passive restoration. During each sampling event, physicochemical parameters were measured, samples of the invertebrate communities were collected and identified to the lowest possible taxonomic level, and alpha and beta diversity analyses were performed to detect community differences associated with the restoration methods. The results showed no significant differences in alpha diversity indices between the two restoration types. However, notable differences in aquatic community composition were observed, influenced by environmental variables such as temperature, pH, and pond connectivity. In ponds with passive restoration, species turnover had a stronger influence on beta diversity, whereas in ponds with active restoration, differences in species abundance were more significant. This study highlights the importance of evaluating aquatic community structures when assessing the effectiveness of restoration processes in wetlands of the Andean páramos, providing valuable insights for their management and conservation. Restoration efforts often result in heterogeneous landscapes, making it essential to understand how biodiversity responds to this spatial variability. These findings contribute to a broader understanding of restoration ecology in high-altitude wetlands.

Graphical abstract

Paleoenvironmental reconstruction was conducted on a short sediment core from a subalpine lake (Low Tatra Mountains, Slovakia) spanning the past ~ 300 years, and aimed to assess the impact of climatic oscillations and the well-documented human activities in the catchment. An analysis of subfossil chironomid remains was applied, supported by a land cover reconstruction using historical maps and orthoimagery. Two main phases of lake development were identified: the first, preceding major anthropogenic pressure and the second, which followed the opening of the first hotel in the lake vicinity in 1950, characterised by massive infrastructure and tourism expansion. The oldest assemblages date to the coldest period of the Little Ice Age (LIA) and were dominated by Derotanypus and Paratanytarsus austriacus-type, indicating very cold and oligotrophic conditions. Warming following the end of LIA caused a gradual shift in the taxonomic composition, with previously dominant taxa disappearing or decreasing in abundance. Dominance of Tanytarsus lugens-type, Zavrelimyia and Heterotrissocladius marcidus-type still reflects relatively cold temperatures and low productivity. Taxonomic composition remained mostly stable until the middle of the twentieth century, when construction work in the catchment caused deforestation, the number of year-round tourists increased, and the lake was dammed to improve conditions for boating and angling. The resulting increased nutrient loading, oxygen depletion and macrophyte development are evident from the rising abundances of taxa tolerant of high trophy. The increase of thermally plastic taxa in the twenty-first century reveals recent climate warming, which will likely only exacerbate the already considerable negative human influence, making lake recovery improbable.

Several population dynamics and reproductive traits of the non-native amphipod Monocorophium insidiosum (Crawford 1937) were studied during their reproductive season, considering their association with the invasive polychaete Ficopomatus enigmaticus (Fauvel, 1923) in the Mar Chiquita coastal lagoon (37° 40 S, 57° 23 W). Amphipods were sampled biweekly in F. enigmaticus reef-like structures (“reefs”) and in sediment from areas without reefs. In reefs, the vertical gradient was also considered. There were differences in M. insidiosum population parameters between habitats (reef and sediment) and among layers within the reef (surface, middle and bottom). Populations in reefs overall displayed higher abundance, continuous reproductive activity and recruitment, and a male-biased sex ratio. In contrast, sediment populations exhibited lower adult densities, sporadic reproduction and recruitment, and a predominantly female-biased sex ratio. Within reefs, the surface had the highest population densities, consistent reproductive activity and a male-biased sex ratio, whereas there was no defined pattern at the bottom aside from a higher proportion of juveniles. These results suggest that the degree of population expansion of M. insidiosum into the coastal lagoon is shaped by a strong association with F. enigmaticus reefs, where M. insidiosum responds to small-scale changes in the vertical habitat structure that enhance its population reproductive potential (i.e., recruitment). This work provides evidence of different non-native and invasive species strategies in which recruitment patterns inside F. enigmaticus reefs might be a mechanism for M. insidiosum population permanence.

Crustaceans play a vital role in maintaining ecosystem balance and supporting human nutrition, relying heavily on estuarine habitats during critical stages of their life cycles. However, research on crustacean assemblages in the Mekong estuaries remains limited, despite their significance to local fisheries and food security. This study aimed to investigate the diversity and distribution of decapod and stomatopod crustaceans, while also identifying key ecological factors influencing their patterns. From March and November 2022, crustacean specimens and water quality data were collected from four estuaries: Cua Dai, Ba Lai, Ham Luong, and Co Chien, within the Mekong estuarine system. A total of 13,134 specimens were recorded, representing 62 species (55 decapods and 7 stomatopods), with the families Penaeidae, Palaemonidae, and Alpheidae being the most dominant. The most abundant species included the palaemonids Macrobrachium equidens, M. mirabile, and Exopalaemon vietnamicus, along with the penaeids Parapenaeopsis hardwickii and Metapenaeus lysianassa. Analysis revealed significant spatiotemporal variations in species composition and abundance. Crustacean densities were notably higher during the dry season (163.21 ± 206.69 inds./1000 m²), at the Cua Dai estuary (163.50 ± 211.15 inds./1000 m²), and in the outer estuary area (155.96 ± 166.74 inds./1000 m²). Diversity indices including Shannon–Wiener, Margalef, and evenness, also varied significantly across seasons and locations. These patterns were likely influenced by environmental factors. In particular, crustacean abundances and diversities were positively correlated with dissolved oxygen and salinity, indicating these as key determinants of assemblage structure. Salinity alone was responsible for approximately one-third of the observed variation in the crustacean assemblages. The findings offer valuable insights for the management and conservation of crustacean assemblages, particularly in the context of environmental changes and increasing fishing pressures.

Periodic impoundment in reservoirs leads to vegetation decay and decomposition, which, in turn, affects nutrient release from sediment. The aim of this study is to investigate the nitrogen and phosphorus release characteristics of Cynodon dactylon (L.) Pers., a dominant plant species in the water-level fluctuation (WLF) zone of one of the world’s largest reservoirs, the Three Gorges Reservoir (TGR), China. A total of 288 live and dead plant samples were subjected to a 120 d submergence experiment at water depths of 0, 3, 6, 10, 20, and 30 m. The dry weights of the plants, as well as the total nitrogen (TN) and total phosphorous (TP) contents of the plant samples, were studied. The water environment and microbial structure and function were also analysed. The findings demonstrated that, in contrast to that of the dead vegetation, the dry weight of the live plants exhibited sustained growth throughout the early submergence period. However, the dead plants experienced continuous dry weight loss. The TN content in the live plants peaked at approximately 30 d (15 d at 30 m water depth) post-submergence, followed by a gradual decline, while significantly higher concentrations (P < 0.05) were maintained than the preflooding levels after 120 d of submergence. However, the dead plants presented a gradual decrease in TN, with significant differences among the various water levels after 120 d. The TP content in the live plants first decreased but then increased, whereas in the dead plants it continuously decreased. Significant differences in TN and TP release were observed between the live and dead plants (P < 0.05). Compared with that of the live plants, the decomposition of the dead plants resulted in significantly greater TN release (4.35 ± 0.59 g kg⁻¹). Similarly, the dead plants presented tenfold greater TP release (1.02 ± 0.030 g kg⁻¹) than the live plants (0.09 ± 0.063 g kg⁻¹). The microbial communities, dominated by Actinobacteria (25.3%) and Proteobacteria (24.1%), were found to significantly influence nutrient release. Water environmental factors such as water depth, light intensity, dissolved oxygen, and specific conductivity affected mainly the nitrogen and phosphorus contents of the live plants. This research provides valuable insights into nutrient dynamics in the WLF zone of the TGR and highlights the differential contributions of live and dead plants to nutrient cycling processes.