The use of constructed wetland (CW) is a natural way of treating wastewater sustainably and economically. However, the implementation of these systems in freezing conditions is still a matter of research and development. The treatment capacity of CWs relies largely on the biological and biochemical processes which further depends on physical conditions such as temperature, solar radiations, etc. Application of wetland systems for treating wastewater faces many challenges in regions with cold climates, resolving which this review has been made. This paper presents a thorough understanding of the components of CWs and their role in contaminant removal. A comprehensive review of the different types of CWs has been done describing the treatment efficiency achieved by its implementation in the cold climate. Furthermore, various technologies which can be clubbed with CWs have also been listed along with the treatment efficiencies obtained. Literature survey indicates that the extent of removing organics (COD and BOD5) and total phosphorous (TP) are not likely to be affected, but total nitrogen (TN) removal appears to slow down at low temperatures. Despite several advantages of CW technology, further research is required to select suitable macrophytes and optimum design parameters to compensate for frigid conditions.

The paper reports the results of research on the Bratsk water body (Russia), the hugest man-made reservoir in the world, using aquatic plants as bioindicators. This aquatic environment requires constant monitoring due to metal emissions by metallurgical, machine-building, and other industries. To that end, the accumulation capacities of Myriophyllum spicatum L., Elodea canadensis Michx., Potamogeton pectinatus L. and Cladophora glomerata L. were compared. The Ti, Cr, Mn, Fe, Ni, Cu, Zn, and, Pb contents in the plants were quantified with X-ray fluorescence. The calculated bioaccumulation indexes provided similar indicator characteristics of these species. The clustering analysis specified the spatial metal pollution in the reservoir. The aquatic plants sampled near industrial enterprises demonstrated the high concentrations: Ti (573-887), Cr (14-22), Mn (609-1080), Fe (9231-12724), Ni (8-11), Cu (51-103), Zn (35-45) and Pb (10-40) µg/g. The average concentrations in the samples collected away from emission sources were significantly lower: Ti (443-598), Cr (7-10), Mn (439-591), Fe (4575-6573), Ni (6-7), Cu (36-58), Zn (27-33) and Pb (6-9). While, they were several-fold higher than threshold values reported for the Lake Baikal plants: Ti – 6; Cr – 2-2.6; Ni – 1.9; Fe – 3-6.7; Mn – 1.5-2.6; Cu – 4; Zn – 1.2-2, and Pb – 7.3. In addition to industrial impacts, the sedimentation processes, coastal erosion, wood rotting and ore occurrences caused increasing in metal contents. Assessment of pollution through the pollution load index and the integration Nemerov index provided the classification of the environment of the Bratsk water reservoir as polluted one.

Poster session | International audience

The negative influence of agrochemicals (pesticides: insecticide, fungicide, and herbicide) on biodiversity is a major ecological concern. In recent decades, many insect species are reported to have rapidly declined worldwide, and pesticides, including neonicotinoids and fipronil, are suspected to be partially responsible. In Japan, application of systemic insecticides to nursery boxes in rice paddies is considered to have caused rapid declines in Sympetrum (Odonata: Libellulidae) and other dragonfly and damselfly populations since the 1990s. In addition to the direct lethal effects of pesticides, agrochemicals indirectly affect Odonata populations through reductions in macrophytes, which provide a habitat, and prey organisms. Due to technical restrictions, most previous studies first selected target chemicals and then analyzed their influence on focal organisms at various levels, from the laboratory to the field. However, in natural and agricultural environments, various chemicals co-occur and can act synergistically. Under such circumstances, targeted analyses might lead to spurious correlations between a target chemical and the abundance of organisms. To address such problems, in this study we adopted a novel technique, “Comprehensive Target Analysis with an Automated Identification and Quantification System (CTA-AIQS)” to detect wide range of agrochemicals in water environment. The relationships between a wide range of pesticides and lentic Odonata communities were surveyed in agricultural and non-agricultural areas in Saga Plain, Kyushu, Japan. We detected significant negative relationships between several insecticides, i.e., acephate, clothianidin, dinotefuran, flubendiamide, pymetrozine, and thiametoxam (marginal for benthic odonates) and the abundance of lentic Epiprocta and benthic Odonates. In contrast, the herbicides we detected were not significantly related to the abundance of aquatic macrophytes, suggesting a lower impact of herbicides on aquatic vegetation at the field level. These results highlight the need for further assessments of the influence of non-neonicotinoid insecticides on aquatic organisms.

Eutrophication transforms clear water into turbid water in shallow lakes. Current restoration techniques focus on re-establishing the clear-water state rather than on its maintenance. We investigated the response of submerged macrophytes to temporary grass carp (Ctenopharyngodon idella) and scraping snail (Bellamya aeruginosa) introductions. We also explored the impacts of herbivores on underwater light conditions to identify their long- and short-term potential to halt regime shift from clear to turbid after clear-water state reestablishment. Herbivores reduced both the biomass of submerged macrophytes and accumulated nutrients in the tissue of submerged macrophytes. This potentially avoided the pulse of endogenous nutrient release which would have exceeded the threshold required for the regime shift from clear to turbid. However, herbivores had a non-significant impact on submerged macrophyte-reduced light attenuation coefficient, which has a positive linear relationship with water chlorophyll a. Further, grass carp and snails enhanced the inhibition ratio of submerged macrophytes to phytoplankton by 3.96 and 2.13 times, respectively. Our study provides novel findings on the potential of herbivore introduction as an indirect biomanipulation tool for halting the regime shift of shallow lakes from clear to turbid after the restoration of submerged macrophytes.

Plastic pollution is a new, pressing, environmental topic. Microplastics are considered contaminants of emerging concern and, consequently, microplastic research has grown exponentially in the last decade. Here, current knowledge regarding the impacts of micro- and nanoplastics on terrestrial plants and aquatic macrophytes is discussed, with a special focus on adsorption, uptake and toxicological effects. Our review reveals that a range of plants and macrophytes can adsorb or internalise plastic particles. Both processes depend on particle characteristics such as size and charge, as well as plant features including a sticky or hydrophobic surface layer. This finding is of concern given that plants and aquatic macrophytes are at the bottom of food webs and are a crucial component of the human diet. Therefore, there is a critical need for improved understanding of adsorption, uptake and impacts of micro- and nanoplastics, and the consequences thereof for trophic transfer, food safety and security. Also, a range of stress responses have been observed for many plant and macrophyte species after both short and long-term exposures to plastic particles. Given that some plastic particles can affect plant productivity, we surmise that plastic particles may potentially impact ecosystem productivity and function. Here we present a synthesis and a critical evaluation of the state of knowledge of micro- and nanoplastics and plants and macrophytes, identifying key questions for future research.

Mecoprop-P (MCPP-P) is an auxin herbicide which has been used against dicotyledonous weed plants since the 1980s. While fate and monitoring data of MCPP-P in the aquatic environment revealing concentrations up to 103 μg/L in freshwaters are well documented, only very few toxicity data and no studies with dicotyledonous macrophytes have been published in open literature so far. To fill up this essential data gap, a microcosm study was conducted in order to test the sensitivity of nine dicotyledonous and one Ceratophyllales macrophyte species. The plant species were exposed to seven MCPP-P concentrations ranging from 8 to 512 μg/L for 21/22 days in one microcosm per concentration, and two further microcosms served as controls. Plant preparation was adapted to each species and endpoints were measured to calculate growth rates. Data were generated to obtain effect concentrations (ECX) which then were used to construct species sensitivity distribution curves (SSD). Eight species proved to be sensitive to MCPP-P in the tested concentration range with EC₅₀ values ranging from 46.9 μg/L for Ranunculus aquatilis to 656.4 μg/L MCPP-P for Ludwigia repens. Taking the EC₅₀ values of this study and published data for autotrophic organisms into account, a hazard concentration (HC₅) of 2.7 μg/L was derived from the SSD curve, while an SSD curve without dicotyledonous macrophytes resulted in an about 100 times higher HC₅ (360.8 μg/L MCCP-P). This confirms that a re-evaluation for old auxin herbicides by including dicotyledonous test species into the environmental risk assessment may be indicated. Furthermore, the use of MCPP-P in bitumen felts as protection against rooting by plants is not in the focus of any risk regulation so far. This application, however, can lead to high run-off concentrations that can enter surface waters easily, exceeding the new regulatory acceptable concentration values.

Because of environmental and societal concerns, new strategies are being developed to mitigate the effects of road salt. These include new deicers that are alternatives to or mixtures with the most common road salt, sodium chloride (NaCl), improved techniques and equipment, and biotic mitigation methods. Using outdoor mesocosms, we investigated the impacts of NaCl and two common alternatives, magnesium chloride (MgCl₂) and calcium chloride (CaCl₂) on freshwater communities. We also investigated the mitigation ability of a common macrophyte, Elodea. We hypothesized that road salt exposure reduces filamentous algae, zooplankton, and macrocrustaceans, but results in increases in phytoplankton and gastropods. We also hypothesized that MgCl₂ is the most toxic salt to communities, followed by CaCl₂, and then NaCl. Lastly, we hypothesized that macrophytes mitigate some of the effects of road salt, specifically the effects on primary producers. We found that all three salts reduced filamentous algal biomass and amphipod abundance, but only MgCl₂ reduced Elodea biomass. MgCl₂ had the largest and longest lasting effects on zooplankton, specifically cladocerans and copepods, which resulted in a significant increase in phytoplankton and rotifers. CaCl₂ increased ostracods and decreased snail abundance, but NaCl increased snail abundance. Lastly, while we did not find many interactions between road salt and macrophyte treatments, macrophytes did counteract many of the salt effects on producers, leading to decreased phytoplankton, increased filamentous algae, and altered abiotic responses. Thus, at similar chloride concentrations, NaCl alternatives, specifically MgCl₂, are not safer for aquatic ecosystems and more research is needed to find safer road management strategies to protect freshwater ecosystems.

Macrophytes play an important role in aquatic ecosystems, and thus are often used in ecological risk assessments of potentially deleterious anthropogenic substances. Risk assessments for macrophyte populations or communities are commonly based on inferences drawn from standardized toxicity tests conducted on floating non-rooted Lemna species, or submerged-rooted Myriophyllum species. These tests follow strict guidelines to produce reliable and robust results with legal credibility for environmental regulations. However, results and inferences from these tests may not be transferrable to emergent macrophytes due to their different morphology and physiology. Emergent macrophytes of the genus Typha L. are increasingly used for assessing phytotoxic effects of environmental stressors, although standardized testing protocols have not yet been developed for this genus. In this review we present a synthesis of previous toxicity studies with Typha, based on which we evaluate the potential to develop standard toxicity tests for Typha spp. with seven selection criteria: ecological relevance to the ecosystem; suitability for different exposure pathways; availability of plant material; ease of cultivation; uniform growth; appropriate and easily measurable toxicity endpoints; and sensitivity toward contaminants. Typha meets criteria 1–3 fully, criteria 4 and 5 partly based on current limited data, and we identify knowledge gaps that limit evaluation of the remaining two criteria. We provide suggestions for addressing these gaps, and we summarize the experimental design of ecotoxicology studies that have used Typha. We conclude that Typha spp. can serve as future standard test species for ecological risk assessments of contaminants to emergent macrophytes.

Bacteria involved with ecosystem N cycling in the rhizosphere of submerged macrophytes are abundant and diverse. Any declines of submerged macrophytes can have a great influence on the abundance and diversity of denitrifying bacteria and anammox bacteria. Natural decline, tardy decline, and sudden decline methods were applied to cultivated Potamogeton crispus. The abundance of anammox bacteria and nirS denitrifying bacteria in rhizosphere sediment were detected using real-time fluorescent quantitative PCR of 16S rRNA, and phylogenetic trees were constructed to analyze the diversities of these two microbes. The results indicated that the concentration of NH₄⁺ in pore water gradually increased with increasing distances from the roots, whereas, the concentration of NO₃⁻ showed a reverse trend. The abundance of anammox bacteria and nirS denitrifying bacteria in sediment of declined P. crispus populations decreased significantly over time. The abundance of these two microbes in the sudden decline group were significantly higher (P > 0.05) than the other decline treatment groups. Furthermore, the abundances of these two microbes were positively correlated, with RDA analyses finding the mole ratio of NH₄⁺/NO₃⁻ being the most important positive factor affecting microbe abundance. Phylogenetic analysis indicated that the anammox bacteria Brocadia fuigida and Scalindua wagneri, and nirS denitrifying bacteria Herbaspirillum and Pseudomonas, were the dominant species in declined P. crispus sediment. We suggest the sudden decline of submerged macrophytes would increase the abundance of anammox bacteria and denitrifying bacteria in a relatively short time.