Search Results (15)

Ciprofloxacin (CIP), a widely used fluoroquinolone antibiotic, is frequently detected in aquatic environments, raising concerns over its ecological risks. In this study, the submerged macrophyte Hydrilla verticillata was employed to investigate its capacity for CIP removal and the associated ecotoxicological effects. A series of batch experiments were conducted to evaluate plant growth, photosynthetic efficiency, oxidative stress responses, CIP biodegradation pathways, and shifts in epiphytic microbial communities. Results showed that CIP significantly inhibited the growth of H. verticillata, with inhibition rates of plant length and fresh weight reaching 15.8% and 29.7%, respectively, at 5 mg/L. Photosynthetic parameters were severely suppressed. Fv/Fm represented the maximum quantum efficiency of PSII, significantly decreased by 94.3% at 10 mg/L, while chlorophyll a and b contents declined by up to 36.1% and 31.2%, respectively, compared to control. Antioxidant responses showed H. verticillata undergo peroxidation damage. Biodegradation analysis revealed that H. verticillata effectively removed CIP from water, with maximum removal rates of 37% at 1 mg/L and 31% at 5 mg/L under high biomass (4.2 g) conditions. CIP accumulation was higher in stems than in leaves, and three biodegradation intermediates (C306, C263, and C248) were identified, suggesting a degradation pathway involving piperazine ring cleavage, de-ethylation, and deamination. High-throughput sequencing further indicated that CIP exposure reduced bacterial diversity and richness on H. verticillata surfaces, while promoting antibiotic-resistant taxa such as Actinobacteria and Bacteroidota. These findings highlight the potential role of H. verticillata in antibiotic-contaminated water remediation. Full article

The study evaluated the vegetative growth and reproductive strategies of the macrophyte Pistia stratiotes under varying nutrient (carbon and nitrogen) and light (full sun and 70% shade) conditions, as well as its epiphytic association with heterocytous cyanobacteria. Plants were collected from a reservoir, transferred to a greenhouse, and subjected to six treatments, with sampling every 15 days. Clonal growth was higher in nitrogen-supplemented treatments, while flowering was more pronounced in carbon-supplemented treatments. Heterocyte production by epiphytic cyanobacteria on roots positively correlated with P. stratiotes total biomass, suggesting the macrophyte utilizes nitrogen fixed by periphytic cyanobacteria. The results highlight the importance of nitrogen and carbon for growth and reproduction, with distinct resource allocation for rosettes (nitrogen) and flowers (carbon). The P. stratiotes-cyanobacteria association may enhance macrophyte population expansion, underscoring the ecological role of these microorganisms. Full article

The phyllosphere microbiome of aquatic macrophytes constitutes an integral component of freshwater ecosystems, serving crucial functions in global biogeochemical cycling and anthropogenic pollutant remediation. In this study, we examined the assembly mechanisms of epiphytic bacterial communities across four phylogenetically diverse macrophyte species (Scirpus validus, Hippuris vulgaris, Nymphoides peltatum, and Myriophyllum spicatum) inhabiting Ningwu Mayinghai Lake (38.87° N, 112.20° E), a vulnerable subalpine freshwater system in Shanxi Province, China. Through 16S rRNA amplicon sequencing, we demonstrate marked phyllospheric microbiome divergence, as follows: Gammaproteobacteria dominated S. validus, H. vulgaris and N. peltatum, while Alphaproteobacteria dominated in M. spicatum. The nitrate, nitrite, and pH value of water bodies and the chlorophyll, leaf nitrogen, and carbon contents of plant leaves are the main driving forces affecting the changes in the β-diversity of epiphytic bacterial communities of four plant species. The partitioning of assembly processes revealed that deterministic dominance governed S. validus and M. spicatum, where niche-based selection contributed 67.5% and 100% to community assembly, respectively. Conversely, stochastic processes explained 100% of the variability in H. vulgaris and N. peltatum microbiomes, predominantly mediated by dispersal limitation and ecological drift. This investigation advances the understanding of microbial community structural dynamics and diversity stabilization strategies in aquatic macrophyte-associated microbiomes, while establishing conceptual frameworks between plant–microbe symbiosis and the ecological homeostasis mechanisms within vulnerable subalpine freshwater ecosystems. The empirical references derived from these findings offer novel perspectives for developing conservation strategies aimed at sustaining biodiversity equilibrium in high-altitude lake habitats, particularly in the climatically sensitive regions of north-central China. Full article

An earlier ecosystemic study on carbon balance calculations of a Posidonia oceanica system in the Bay of Calvi [Corsica, France], indicated that the bacterial carbon demand [BCD] between May and October [Temp > 18 °C] in the seagrass meadow could not be sustained by net leaf production of P. oceanica and its epiphytes [NPP]. Hence, the system was clearly heterotrophic as only one autotrophic region was recorded, namely the depth range from 0–10 m. Already published data on the production of algal macrophytes and Cymodocea nodosa meadows and their mapping in the Bay of Calvi allowed a re-evaluation of the carbon budgets for each specific depth range. It was shown that C. nodosa could contribute significantly to covering the bacterial carbon demand of the P. oceanica system and that a positive carbon balance could be obtained for the seagrass meadow due to this carbon input when the temperature was higher than 18 °C, even though the depth ranges between 21–30 m and 31–38 m were negative. The overall trend indicates that the system cannot rely on the phytoplanktonic production of the water column, as BCD is higher than phytoplanktonic carbon production. When integrating BCD and net primary production [NPP] of the water column in summer we noticed a lack of some 97.6 to 104.3 tons of carbon which is not covered by the seagrasses leaf production and the algal macrophytes. The obtained data indicate clearly that other carbon carbon-producing compartments like the microphytobenthos, the NPP of rhizome epiphytes, and the detrital carbon import into the Bay of Calvi need to be investigated. Full article

Shallow lakes according to the alternative states theory may present extremely different environmental conditions, clear water with abundant growth of macrophytes and turbid water with cyanobacterial blooms. The deterioration of water quality led to visible changes within submerged macrophytes and thus in available habitats for plant-associated biocenosis. Larvae of chironomids are the most numerous and widely distributed macroinvertebrates. Since benthic chironomids are used in the monitoring of environmental changes and in paleolimnological research, epiphytic chironomids are not well known in this regard. The larvae can be used as indicators of lake macrophyte status. The present study focuses on plant-associated chironomids of a group of ten shallow lakes of the Polesie region (eastern Poland). The lakes were classified with alternative states theory as macrophyte-dominated (MD), phytoplankton–macrophyte-dominated (PMD) and phytoplankton-dominated (PD). The domination structure of epiphytic chironomids showed significant changes between lake types, with the highest abundance of Paratanytarsus austriacus in MD lakes, Endochironomus albipennis in PMD lakes and Cricotopus sp. (gr. sylvestris) in PD lakes. The highest mean density was noted in PD lakes while the highest species diversity (values of Shannon–Wiener index) in PMD lakes. Moreover, environmental variables (macrophyte biomass, Secchi disc depth, chlorophyll-a and TP) differentiating lake types were used in RDA analysis to evaluate their effect on chironomid taxa distribution. Next, the variables with a significant effect on specific chironomid taxa were used in multivariate regression analysis. The results led to the creation of a model of distribution of chironomid taxa with regard to lake type. Full article

Submerged macrophytes in eutrophic aquatic environments adapt to changes in ammonia nitrogen (NH₄-N) levels by modifying their levels of free amino acids (FAAs) and soluble carbohydrates (SCs). As symbionts of submerged macrophytes, epiphytic bacteria have obvious host specificity. In the present study, the interspecific differences in the FAA and SC contents of Hydrilla verticillata (Linn. f.) Roylep, Vallisneria natans Hara and Chara braunii Gmelin and their leaf epiphytic bacterial communities were assessed in response to increased NH₄-N concentrations. The results revealed that the response of the three submerged macrophytes to NH₄-N stress involved the consumption of SCs and the production of FAAs. The NH₄-N concentration had a greater impact on the variation in the FAA content, whereas the variation in the SC content was primarily influenced by the species. At the phylum level, the relative abundance of Nitrospirota on the leaves exhibited specific differences, with the order H. verticillata > V. natans > C. braunii. The dominant genera of epiphytic bacteria with denitrification effects on V. natans, H. verticillata and C. braunii leaves were Halomonas, Acinetobacter and Bacillus, respectively. When faced with NH₄-N stress, the variation in epiphytic bacterial populations associated with ammonia oxidation and denitrification among submerged macrophytes could contribute to their divergent responses to heightened nitrogen levels. Full article

Brownification denotes increasing water color, partly caused by increasing dissolved organic matter of terrestrial origin in freshwater. Brownification has become a wide-spread environmental problem because water color alters the physicochemical environment and biological communities in aquatic ecosystems. However, our understanding of its ecological effects on aquatic macrophytes is limited. Here, an indoor mesocosm experiment with a common submerged macrophyte, Potamogeton crispus, along an increasing gradient of brownification was conducted over a period of 42 days. Results showed that P. crispus was able to overcome low degrees of brownification owing to the plasticity in morphological and physiological traits and P. crispus growth even benefitted from the concomitant nutrients along with brownification. However, the macrophyte growth was negatively affected by a 10-fold increase in water color beyond its current level. Additionally, collapse in antioxidant systems and potent photosynthesis inhibition implied that P. crispus could not adapt to the low-light stress generated under the high degree of brownification. Epiphytic bacteria are more sensitive to brownification than their hosts. Any degree of brownification initially caused a decrease in microbial diversity of epiphytic biofilm, whereafter the concomitant nutrients under brownification favored the growth of epiphytic microorganisms. The shading effect of a large number of epiphytic biofilms under brownification may further aggravate the low-light stress on macrophytes. Overall, the study provides new insights into the comprehensive effects and underlying mechanisms of brownification on macrophytes. Full article

Fish predation is restricted in areas with high aquatic macrophyte coverage; however, bluegill sunfish (Lepomis macrochirus), an exotic fish species, can consume prey even in such spaces. Here, we hypothesized that the cladoceran community structures in three wetlands (Upo, Jangcheok, and Beongae) with abundant macrophytes within the Nakdong River basin, South Korea, were influenced by high abundance and foraging activities of L. macrochirus. The study areas were dominated by L. macrochirus with body sizes < 10 cm, and their cladoceran consumption was higher than that of larger size classes. Most of the cladoceran species that were highly consumed by L. macrochirus were pelagic (i.e., Daphnia obtusa and Daphnia pulex); epiphytic species were consumed less (i.e., Chydorus shpaericus, Alona retangula, and Pleroxus laevis). We hypothesize that epiphytic cladoceran species are not easily explored by L. macrochirus. Selective consumption of pelagic species by L. macrochirus was reflected in the seasonal cladoceran distribution. Epiphytic species were the most abundant, whereas pelagic species abundance was relatively low. The low density of pelagic cladoceran species further increased the epiphytic species abundance. We conclude that the dominance of L. macrochirus introduced into Korean wetlands has been sufficient to change the cladoceran community structure; therefore, the abundance of epiphytes cladocerans in other countries or regions needs to be provided priority to the dominance and consumption pattern of L. macrochirus. Full article

This paper investigates the effects of water flow on the growth and physiological indicators of the submerged macrophyte, Vallisneria natans, and the bacteria and algae community composition on its epiphytic biofilm-covered leaves. The authors set up a simulated flowing water laboratory experiment testing high nitrogen (N) and phosphorus (P) concentrations. Total chlorophyll and dissolved oxygen (DO) was significantly enhanced, and turbidity was reduced, thereby accelerating the growth of V. natans. These experiments were compared to another set of observations on a static group. The accumulation of malonaldehyde (MDA) in the dynamic groups was significantly higher than that in the static group. As an antioxidant stress response, the total superoxide dismutase (T-SOD) was also induced in plants exposed to nutrient-rich flowing water. The results of 16S rRNA high-throughput sequencing analyses showed that the water flow increased the bacteria community diversity of biofilm-producing bacteria with N and P removing bacteria, carbon cycle bacteria, and plant growth-promoting rhizobacteria on the epiphytic biofilm. This research determined that water flow alleviates the adverse effects of eutrophication when V. natans grows in water containing high N and P concentrations. Water flow also inhibits the growth of cyanobacteria (also referred to as blue-green algae) in epiphytic biofilm. The ecological factor of water flow, such as water disturbance and aeration measures, could alleviate the adverse effect of eutrophic water by providing a new way to restore submerged macrophytes, such as V. natans, in eutrophic water. Full article

In this study, we provide insights into that characteristics of two sites representing different conditions of productivity and salinity impact on trophic network structures of macrophyte habitats and diet of benthic grazers at the active vegetation period in the Curonian Lagoon (southeastern Baltic Sea). Regarding the epiphytic growth, macrophytes were more overgrown in the relatively less productive (northern) site with a muddy bottom and more frequent marine water inflow than in the (southern) site with higher productivity and freshwater sandy habitat. Stable isotope analysis revealed that organisms’ samples from the northern site were more enriched with the heavier carbon isotopes, but depleted in the heavier nitrogen isotopes than those from the southern site. Gastropods and amphipods mainly consumed sedimentary organic matter in the southern site, while they grazed epiphytes together with sedimentary organic matter in the northern site. Although to a low extent, gastropods consumed more charophytes than pondweeds in the southern site. This study contributes to a better understanding of the functioning and structure of lagoonal systems, highlighting the importance, often overlooked, of the benthic compartment, which, however, may have a relevant influence on the productivity of the whole system. Full article

This study focused on the monitoring and assessment of aquatic ecosystem functioning based on the abiotic and biotic features of Lake Nasser in the post-flood and pre-flood periods as the last ones before water storing behind the Grand Ethiopian Renaissance Dam. The physicochemical parameters, distribution and structure of biotic communities, including bacteria, phytoplankton, zooplankton, macrophytes, epiphytes and fish were analyzed at 15 sites. The values of most parameters (primarily temperature, total suspended solids, pH, orthophosphates, carbonates, sulphates and some cations) were higher in the pre-flood period, whereas higher values of conductivity, total dissolved solids, total solids, nitrites, nitrates, chemical oxygen demand, bicarbonates and chlorophyll a were recorded in the post-flood period. Cyanobacteria-dominated phytoplankton and total coliform bacteria were more abundant in the pre-flood period, and especially at sites 10–15, whereas higher abundances of zooplankton were recorded in the post-flood period. All these changes in parameters were significantly differentiated, and only the concentrations of dissolved oxygen, biochemical oxygen demand, ammonium and silicates were at similar level in both periods. The study also indicated that environmental factors had affected the macrophyte distribution and the adaptation of the invasive species Myriophyllum spicatum to thrive under different environmental factors in the lake. Besides, macrophytes provided the habitat to other aquatic organisms, especially epiphytes, and also helped maintaining the good water quality, nutrient cycling and stabilizing rivers’ and lakes’ banks. Generally, these conditions were rather favorable for biological processes and fish production. Full article

The relationship between the ciguatoxin-producer benthic dinoflagellate Gambierdiscus and other epibenthic dinoflagellates in the Canary Islands was examined in macrophyte samples obtained from two locations of Fuerteventura Island in September 2016. The genera examined included Coolia, Gambierdiscus, Ostreopsis, Prorocentrum, Scrippsiella, Sinophysis, and Vulcanodinium. Distinct assemblages among these benthic dinoflagellates and preferential macroalgal communities were observed. Vulcanodinium showed the highest cell concentrations (81.6 × 10³ cells gr⁻¹ wet weight macrophyte), followed by Ostreopsis (25.2 × 10³ cells gr⁻¹ wet weight macrophyte). These two species were most represented at a station (Playitas) characterized by turfy Rhodophytes. In turn, Gambierdiscus (3.8 × 10³ cells gr⁻¹ wet weight macrophyte) and Sinophysis (2.6 × 10³ cells gr⁻¹ wet weight macrophyte) were mostly found in a second station (Cotillo) dominated by Rhodophytes and Phaeophytes. The influence of macrophyte’s thallus architecture on the abundance of dinoflagellates was observed. Filamentous morphotypes followed by macroalgae arranged in entangled clumps presented more richness of epiphytic dinoflagellates. Morphometric analysis was applied to Gambierdiscus specimens. By large, G. excentricus was the most abundant species and G. australes occupied the second place. The toxigenic potential of some of the genera/species distributed in the benthic habitats of the Canary coasts, together with the already known presence of ciguatera in the region, merits future studies on possible transmission of their toxins in the marine food chain. Full article

Species invasions are changing aquatic ecosystems worldwide. Submerged aquatic macrophytes control lake ecosystem processes through their direct and indirect interactions with other primary producers, but how these interactions may be altered by macrophyte species invasions in temperate lakes is poorly understood. We addressed whether invasive watermilfoil (IWM) altered standing crops and gross primary production (GPP) of other littoral primary producers (macrophytes, phytoplankton, attached algae, and periphyton) in littoral zones of six Michigan lakes through a paired-plot comparison study of sites with IWM (standardized abundance 7–56%) compared to those with little or no IWM (standardized abundance 0–2%). We found that primary producer standing crops and the GPP of epiphytes, phytoplankton, and benthic periphyton were variable among lakes and not significantly different between paired study plots. Macrophyte standing crops predicted rates of benthic periphyton GPP, and standing crops of all other primary producers across all study plots. Overall, our results suggest that the effects of IWM on other primary producers in littoral zones may be lake-specific, and are likely dependent on the density of IWM, or whether it is functionally similar to other native species that it replaces or co-exists with. Moreover, in lakes where IWM is established but does not dominate macrophyte assemblages, the effects on littoral zone productivity may be minimal. Instead, overall macrophyte biomass is the primary factor controlling the rates of production and biomass of the other littoral zone primary producers, as has long been understood and observed in lake ecosystems. Full article

The rhizosphere and the phyllosphere represent two different epiphytic compartments of host plant, which are closely related to plant growth, health, and productivity. However, the understanding of the diversity, composition, and assembly of the bacterial communities in different epiphytic microenvironments of large emerged macrophytes has remained elusive, especially the abundant and rare taxa across rhizosphere and phyllosphere communities. In this study, we collected samples of two different epiphytic compartments (rhizosphere and phyllosphere) of Phragmites australis. Both 16S rRNA gene-based high-throughput sequencing and null-model analysis were employed to determine the difference in the composition and assembly of above-mentioned epiphytic bacterial communities. Our results indicated that bacterial communities of rhizosphere exhibited higher diversity and richness than those of phyllosphere. Deterministic processes dominated the assembly of bacterial community in both compartments, and stochastic processes contributed a certain proportion (30.30%) in the assembly of phyllosphere bacterial community. We also found that rare taxa contributed more significantly to the alpha- and beta-diversity of bacterial community than those of abundant taxa. The obtained data are useful for better understanding the bacterial community of different epiphytic compartments of P. australis. Full article

Increasing N concentration and the high density of epiphytic algae are both key factors leading to the decline of submerged macrophytes in many eutrophic lakes. In order to investigate the impacts of increased nitrate-N concentration and the growth of epiphytic algae on the decline of submerged vegetation, we conducted a 2 × 4 factorial experiment with the submerged macrophyte Vallisneria natans (Lour.) Hara by measuring the biomass of plants and some physiological indexes in leaves of V. natans under four nitrate-N concentrations in the water column (0.5, 2.5, 5, and 10 mg/L) and two epiphytic groups (epiphytic algae group and no epiphytic algae group). The results suggested that epiphytic algae could impose adverse effects on the biomass accumulation of V. natans, while the increasing nitrate-N concentration (0.5–10 mg/L) could oppositely promote this process and counteract the adverse effect of epiphytic algae. When nitrate-N concentration was 5 mg/L, the total chlorophyll content in leaves of V. natans in the epiphytic algae group was prominently lower compared with the no epiphytic algae group, while MDA, free proline, and anti-oxidant enzyme (SOD, POD, CAT) activities were significantly higher. Overhigh nitrate-N concentration in the water column also directly imposed adverse effects on the physiology of V. natans. When nitrate-N concentration was over 5 mg/L, the total chlorophyll content and free proline decreased in the no epiphytic algae group, while soluble carbohydrates and soluble proteins decreased when nitrate-N was over 2.5 mg/L. Meanwhile, epiphytic algae and nitrate-N content imposed a synergetic effect on the anti-oxidant enzyme activities of V. natans. When nitrate-N concentration was over 5 mg/L, SOD, POD, and CAT activities kept constant or decreased, which indicated that the oxidation resistance of V. natans was inhibited by stress. Our results indicate that epiphytic algae and increasing nitrate-N concentration in the water column could severally or synergistically impose adverse effects on the physiology of submerged macrophytes and are both key factors leading to the decline of submerged macrophytes. Full article