Plastic debris of all sizes has been detected in marine, terrestrial and freshwater habitats. Effects of plastic debris on macrophytes have hardly been studied, despite their importance in aquatic ...ecosystems. We provide the first experimental study exploring nano- and microplastic effects on the growth of sediment-rooted macrophytes. Myriophyllum spicatum and Elodea sp. were exposed to sediments amended with six doses of polystyrene (PS) nanoplastic (50–190 nm, up to 3% sediment dry weight) and PS microplastic (20–500 μm, up to 10% dry weight) under laboratory conditions. Both macrophyte species were tested for changes in root and shoot dry weight (DW), relative growth rate (RGR), shoot to root ratio (S:R), main shoot length and side shoot length. Microplastics did not produce consistent dose-effect relationships on the endpoints tested, except that main shoot length was reduced for M. spicatum with increasing microplastic concentration. Nanoplastic significantly reduced S:R for both macrophytes as a result of increased root biomass compared to shoot biomass. Nanoplastic also caused a decrease in M. spicatum main shoot length; however, shoot biomass was not affected. Elodea sp. side shoot length, root and shoot biomass and RGR were positively correlated to the nanoplastic concentration. All effects occurred at higher than environmentally realistic concentrations, suggesting no immediate implications for ecological risks. Our study did not aim for the elucidation of the exact mechanistic processes that cause the effects, however, particle size seems to play an important factor.
Nano- and microplastics affect growth of sediment-rooted macrophytes.
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•We explored effects of nanoplastic and microplastic for sediment-rooted macrophytes.•Shoot length of M. spicatum was reduced with increasing microplastic concentration.•Nanoplastic reduced the shoot to root biomass ratio for both studied species.•All effects occurred at higher than environmentally realistic concentrations.•This suggests there are no immediate implications for ecological risks.
During the present study we measured plastic adjustments in morphological traits, clonal architecture and biomass partitioning for an aquatic clonal species (Myriophyllum spicatum) under two ...contrasting conditions in the field that is, standing vs. running waters. A significant difference in morphological traits, clonal architecture and biomass partitioning to different plant parts was observed between standing and running water populations. The species produces longer and narrower leaves in running water but smaller and broader ones in standing water populations. Spike and peduncle length, number of spikes and flowers per ramet were significantly higher in standing water populations. Moreover, a high seed set was observed in standing water populations while as running water populations did not produce any seeds. Total length of rhizome, branching of ramets, spacer length and average length of ramets per plant were highest in standing water populations. However, number of ramets per plant and number of branches per rhizome were highest in running water populations. The percentage dry mass allocation was highest to shoots followed by seeds and spikes and much less was allocated to under sediment parts in standing water populations, whereas, in running water populations allocation was highest to shoots followed by under sediment and spikes. The reduction in size, higher biomass allocations to belowground organs and a more compact growth form (reduced spacer lengths) in case of running water populations as compared to standing water populations contributed to reduce the damage risk in running water populations due to mechanical stress caused by the flow of running water.
Submersed macrophytes have important ecological functions in many streams, but fostering growth of beneficial native species while suppressing weedy invasives may be challenging. Two approaches ...commonly used in management of terrestrial plant communities may be useful in this context: (1) altering resource availability and (2) establishing desirable species before weeds can invade (priority effects). However, these approaches are rarely used in aquatic systems, despite widespread need for sustainable solutions to aquatic weed problems. In artificial stream channels in California, USA, I conducted experiments with asexual propagules of non-native invasive Myriophyllum spicatum (Eurasian watermilfoil) and native Elodea nuttallii (western waterweed) to address the questions: (1) How does light availability affect relative performance of the two species?; (2) Does planting the native earlier than the invasive decrease survival or growth rate of the invasive?; and (3) Do light level and priority effects interact? The relative performance between E. nuttallii and M. spicatum had an interesting and unexpected pattern: M. spicatum had higher growth rates than E. nuttallii in the zero and medium shade levels, but had similar performance in the low and high shade levels. This pattern is most likely the result of E. nutallii's sensitivity to both very low and very high light, and M. spicatum's sensitivity to very low light only. Native priority did not significantly affect growth rate or survival of M. spicatum, possibly because of unexpectedly poor growth of the E. nuttallii planted early. This study suggests that altering light levels could be effective in reducing growth of an invasive macrophyte, and for changing the competitive balance between a native and a non-native species in the establishment phase. Further investigations into the use of priority effects and resource alteration for submersed macrophyte management are warranted, given their mixed results in other (limited) studies.
Epiphytic bacteria on the surfaces of submerged macrophytes play important roles in the growth of the host plant, nutrient cycling, and the conversion of pollutants in aquatic systems. A knowledge of ...the epiphytic bacterial community structure could help us to understand these roles. In this study, the abundance, diversity, and functions of the epiphytic bacterial community of
Myriophyllum spicatum
collected from Baiyangdian Lake in June, August, and October 2019 were studied using quantitative PCR (qPCR), high-throughput sequencing, and the prediction of functions. An analysis using qPCR showed that the epiphytic bacteria were the most abundant in October and the least abundant in August. High-throughput sequencing revealed that Proteobacteria, Gammaproteobacteria, and
Aeromonas
were the dominant phylum, class, and genus in all the samples. The common analyses of operational taxonomic units (OTUs), NMDS, and LDA showed that the epiphytic bacterial communities were clustered together based on the seasons. The results of a canonical correlation analysis (CCA) showed that the key water quality index that affected the changes of epiphytic bacterial community of
M. spicatum
was the total phosphorus (TP). The changes in abundance of Gammaproteobacteria negatively correlated with the TP. Predictive results from FAPROTAX showed that the predominant biogeochemical cycle functions of the epiphytic bacterial community were chemoheterotrophy, nitrate reduction, and fermentation. These results suggest that the epiphytic bacterial community of
M. spicatum
from Baiyangdian Lake varies substantially with the seasons and environmental conditions.
In the present study, ground dry powder of Myriophyllum spicatum L. was utilized for adsorption of cobalt and cesium dissolved in water to imitate an aqueous solution contaminated with stable or ...radioactive elements. The dried biomass was characterized by FT-IR. The adsorption behavior was evaluated with varying various factors such as time effect, concentration of metal ion, temperature and pH-value to find out kinetic and equilibrium isotherms parameters. The experimental results indicated that about 85% of Co and more than 50% of Cs were efficiently removed from contaminated water by using the dried plant of M. spicatum L. as a function of metal concentration. Moreover, the equilibrium data were carried out by extrapolation of the “Langmuir” and “Freundlich” isotherms. Pseudo-first order, pseudo-second- order and intra-particular diffusion models were applied for the kinetic study. Based on the experimental and theoretical data obtained, it is suggested that dried biomass of M. spicatum L. could be used as an inexpensive and efficient natural adsorbent material of reasonable efficiency for the accumulation of cobalt and cesium metals from aqueous solutions.
Economic evaluations of invasive species are essential for providing comprehensive assessments of the benefits and costs of publicly-funded management activities, yet many previous investigations ...have focused narrowly on expenditures to control spread and infestation. We use hedonic modeling to evaluate the economic effects of Eurasian milfoil (Myriophyllum spicatum) invasions on lakefront property values of single-family homes in an urban-suburban landscape. Milfoil often forms dense canopies at the water surface, diminishing the value of ecosystem services (e.g., recreation, fishing) and necessitating expensive control and management efforts. We compare 1,258 lakeshore property sale transactions (1995-2006) in 17 lakes with milfoil and 24 un-invaded lakes in King County, Washington (USA). After accounting for structural (e.g., house size), locational (e.g., boat launch), and environmental characteristics (e.g., water clarity) of lakes, we found that milfoil has a significant negative effect on property sales price ($94,385 USD lower price), corresponding to a 19% decline in mean property values. The aggregate cost of milfoil invading one additional lake in the study area is, on average, $377,542 USD per year. Our study illustrates that invasive aquatic plants can significantly impact property values (and associated losses in property taxes that reduce local government revenue), justifying the need for management strategies that prevent and control invasions. We recommend coordinated efforts across Lake Management Districts to focus institutional support, funding, and outreach to prevent the introduction and spread of milfoil. This effort will limit opportunities for re-introduction from neighboring lakes and incentivize private landowners and natural resource agencies to commit time and funding to invasive species management.
Myriophyllum spicatum, Eurasian watermilfoil, is a submerged aquatic plant invasive to North America. Several characteristics found in M. spicatum provide reasoning behind its invasion success such ...as its ability to spread and grow rapidly as well as displace other surrounding native species. However, Eurasian watermilfoil’s effects on ecosystem functioning (such as dissolved oxygen) and how such functioning differ from effects of native vegetation have seldom been studied. Using data collected in field, we used statistical models including Gaussian multivariate linear effect models and structural equation modelling (SEM), to investigate the effect of vegetation type and cover on dissolved oxygen (DO) and temperature gradients. Here, we show that invasive Eurasian watermilfoil colonies, relative to native submerged vegetation, can have a direct effect on DO gradients. These changes in DO conditions were driven by both an increase in surface oxygen concentrations and a decrease in bottom layer oxygen concentration in dense M. spicatum vegetation. Furthermore, we find that the differences in DO gradients could be predicted from M. spicatum’s direct impact on oxygen concentration and not indirectly via its effects on water temperature. Our results demonstrate that dense colonies of M. spicatum can directly affect DO concentrations and may do so more than native macrophytes which could explain its rapid spread and potential impacts on ecosystem functioning.
•Linear models test variation in DO and temperatures among vegetation.•SEM is used to assess direct and indirect effect sizes of M. spicatum on DO.•M. spicatum exhibited sharper declines in DO with depth than native vegetation.•M. spicatum increase surface-level DO, and decreased bottom-layer DO.•Vegetation type (native and M. spicatum) did not impact water temperatures.
The ‘home-field advantage’ (HFA) hypothesis states that litter decomposes faster in its ‘home’ habitat, i.e., in the same habitat as the plant species from which it was derived than it does ‘away’ ...from its home, i.e., in the habitat of a different plant species. However, studies pertaining to HFA in aquatic ecosystems are relatively few. One area not well-studied is whether the presence of living plants has an effect on the HFA of aquatic macrophyte decomposition in a eutrophic lake. Here, we conducted reciprocal litter transplanting experiments, coupled with removal of living plants, between a dominant submerged macrophyte (Myriophyllum spicatum) and a floating-leaved macrophyte (Trapa natans) in a eutrophic urban lake in China, for 50 days. Test plots were created at sites by removing the dominant macrophytes from their ‘home’ habitats to test the effect of living plants on decomposition rates and HFA effect. The water chemistry of the two sites was not significantly different. The initial litter qualities were significantly higher in M. spicatum than in T. natans. The decomposition rates of T. natans were significantly greater in both the control and test plots in its ‘home’ habitat, indicating a positive HFA effect, while the decomposition rates of M. spicatum were significantly greater in the ‘away’ habitat compared to its ‘home’ habitat in all treatments, indicating a home-field disadvantage effect. The removal of living plants had a noticeable effect on the abundance of associated-macroinvertebrates, but had an inconsistent effect on decomposition rates providing conflicting evidence for HFA. In total, 10 macroinvertebrate taxa from four functional feeding groups (FFGs) were collected during the experiment. Compared to macroinvertebrate communities, microbial activities showed less correlation with decomposition rates. Our results provide evidence to suggest that decomposition-based HFA is dependent upon litter quality, habitat, and their interactions in a eutrophic urban lake.
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•We investigated home-field advantage (HFA) effects on aquatic macrophyte decomposition in a eutrophic urban lake.•T. natans showed a positive HFA effect but M. spicatum showed a negative one.•HFA was strongly mediated by litter quality, habitat, and their interactions.•The presence of living plants had inconsistent effects on decomposition rate and occurrence of HFA.
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