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This paper reviews the current state-of-the-art, limitations, critical issues, and new directions in freshwater plant ecotoxicology. We selected peer-reviewed studies using relevant databases and for each (1) publication year, (2) test plant species, (3) reference plant group (microalgae, macroalgae, bryophytes, pteridophytes, flowering plants), (4) toxicant tested (heavy metal, pharmaceutical product, hydrocarbon, pesticide, surfactant, plastic), (5) experiment site (laboratory, field), and (6) toxicant exposure duration. Although aquatic plant organisms play a key role in the functioning of freshwater ecosystems, mainly linked to their primary productivity, their use as biological models in ecotoxicological tests was limited if compared to animals. Also, toxicant effects on freshwater plants were scarcely investigated and limited to studies on microalgae (80%), or only to a certain number of recurrent species ( Pseudokirchneriella subcapitata , Chlorella vulgaris , Lemna minor , Myriophyllum spicatum ). The most widely tested toxicants on plants were heavy metals (74%), followed by pharmaceutical products and hydrocarbons (7%), while the most commonly utilized endpoints in tests were plant growth inhibition, variations in dry or fresh weight, morpho-structural alterations, chlorosis, and/or necrosis. The main critical issues emerged from plant-based ecotoxicological tests were the narrow range of species and endpoints considered, the lack of environmental relevance, the excessively short exposure times, and the culture media potentially reacting with toxicants. Proposals to overcome these issues are discussed.

Although freshwater invasions have not been targeted for maintenance management or eradication as often as terrestrial invasions have, attempts to do so are frequent. Failures as well as successes abound, but several methods have been improved and new approaches are on the horizon. Many freshwater fish and plant invaders have been eliminated, especially by chemical and physical methods for fishes and herbicides for plants. Efforts to maintain invasive freshwater fishes at low levels have sometimes succeeded, although continuing the effort has proven challenging. By contrast, successful maintenance management of invasive freshwater plants is uncommon, although populations of several species have been managed by biological control. Invasive crayfish populations have rarely been controlled for long. Marine invasions have proven far less tractable than those in fresh water, with a few striking eradications of species detected before they had spread widely, and no marine invasions have been substantially managed for long at low levels. The rapid development of technologies based on genetics has engendered excitement about possibly eradicating or controlling terrestrial invaders, and such technologies may also prove useful for certain aquatic invaders. Methods of particular interest, alone or in various combinations, are gene-silencing, RNA-guided gene drives, and the use of transgenes.

• Cable bacteria are sulfide-oxidising, filamentous bacteria that reduce toxic sulfide levels, suppress methane emissions and drive nutrient and carbon cycling in sediments. Recently, cable bacteria have been found associated with roots of aquatic plants and rice (Oryza sativa). However, the extent to which cable bacteria are associated with aquatic plants in nature remains unexplored. • Using newly generated and public 16S rRNA gene sequence datasets combined with fluorescence in situ hybridisation, we investigated the distribution of cable bacteria around the roots of aquatic plants, encompassing seagrass (including seagrass seedlings), rice, freshwater and saltmarsh plants. • Diverse cable bacteria were found associated with roots of 16 out of 28 plant species and at 36 out of 55 investigated sites, across four continents. Plant-associated cable bacteria were confirmed across a variety of ecosystems, including marine coastal environments, estuaries, freshwater streams, isolated pristine lakes and intensive agricultural systems. This pattern indicates that this plant–microbe relationship is globally widespread and neither obligate nor species specific. • The occurrence of cable bacteria in plant rhizospheres may be of general importance to vegetation vitality, primary productivity, coastal restoration practices and greenhouse gas balance of rice fields and wetlands.

There has been substantial recent progress in determining the distributions and identity of vulnerable species, and in understanding how (and where) human activity is leading to extinctions. Pimm et al. review the current state of knowledge and ask what the future rates of species extinction will be, how well protected areas will slow extinction rates, and how the remaining gaps in knowledge might be filled. Science , this issue p. 10.1126/science.1246752 Recent studies clarify where the most vulnerable species live, where and how humanity changes the planet, and how this drives extinctions. We assess key statistics about species, their distribution, and their status. Most are undescribed. Those we know best have large geographical ranges and are often common within them. Most known species have small ranges. The numbers of small-ranged species are increasing quickly, even in well-known taxa. They are geographically concentrated and are disproportionately likely to be threatened or already extinct. Current rates of extinction are about 1000 times the likely background rate of extinction. Future rates depend on many factors and are poised to increase. Although there has been rapid progress in developing protected areas, such efforts are not ecologically representative, nor do they optimally protect biodiversity.

The global and seemingly unstoppable spread of invasive alien plants emerges as one of the main topics of current science. This is due to the multiple repercussions of invasive plants on biodiversity and ecosystem functioning, plus huge consequences on human existence. In freshwaters, lots of invaders are extremely competitive by virtue of their idiosyncratic reproductive and adaptive strategies. As “inland islands”, freshwaters seem particularly prone to changes when invaded, such as reorganisation of food webs and biotic interactions. Together, these events are self-reinforcing, implying hardly reversible hysteric phenomena. The intention of this paper is to point out: invasion pathways, driving factors, invasion mechanisms, and noticeable effects mediated by plant invaders in freshwaters through an extensive knowledge review. The growing evidence suggests the dawn of a new epochal phase: a globally alien-dominated “bio-historical horizon”, tentatively called “Exocene”, where invaders play predominant roles that drive freshwaters functioning and successional unexpected stages. In the context of invasion science, Exocene reinforces the need for an ecosystem-based perspective to properly understand the implications of plant invaders in freshwaters. Seven challenging issues emerge to be addressed to better outline the global paths of biodiversity and functioning between biomes when faced with biological invasion.

Unlike in land plants, photosynthesis in many aquatic plants relies on bicarbonate in addition to carbon dioxide (CO₂) to compensate for the low diffusivity and potential depletion of CO₂ in water. Concentrations of bicarbonate and CO₂ vary greatly with catchment geology. In this study, we investigate whether there is a link between these concentrations and the frequency of freshwater plants possessing the bicarbonate use trait. We show, globally, that the frequency of plant species with this trait increases with bicarbonate concentration. Regionally, however, the frequency of bicarbonate use is reduced at sites where the CO₂ concentration is substantially above the air equilibrium, consistent with this trait being an adaptation to carbon limitation. Future anthropogenic changes of bicarbonate and CO₂ concentrations may alter the species compositions of freshwater plant communities.

Human fascioliasis infection sources are analysed for the first time in front of the new worldwide scenario of this disease. These infection sources include foods, water and combinations of both. Ingestion of freshwater wild plants is the main source, with watercress and secondarily other vegetables involved. The problem of vegetables sold in uncontrolled urban markets is discussed. Distinction between infection sources by freshwater cultivated plants, terrestrial wild plants, and terrestrial cultivated plants is made. The risks by traditional local dishes made from sylvatic plants and raw liver ingestion are considered. Drinking of contaminated water, beverages and juices, ingestion of dishes and soups and washing of vegetables, fruits, tubercles and kitchen utensils with contaminated water are increasingly involved. Three methods to assess infection sources are noted: detection of metacercariae attached to plants or floating in freshwater, anamnesis in individual patients, and questionnaire surveys in endemic areas. The infectivity of metacercariae is reviewed both under field conditions and experimentally under the effects of physicochemical agents. Individual and general preventive measures appear to be more complicated than those considered in the past. The high diversity of infection sources and their heterogeneity in different countries underlie the large epidemiological heterogeneity of human fascioliasis throughout.

We investigated the effect of nano‐ and microplastics on the freshwater duckweed species Spirodela polyrhiza, a vascular plant. S. polyrhiza was exposed for 120 h to concentrations ranging from 102 to 106 particles·mL−1. We assessed effects on growth and chlorophyll production, and explored adsorption and absorption by way of confocal microscopy. For both nano‐ and microsized particles, no concentration‐dependent effects on growth were found (expressed as fresh weight, frond, and root sizes). In addition, chlorophyll concentrations were not significantly affected. Confocal microscopy indicated that nanosized plastic particles adsorbed externally to the duckweed, especially to the roots. Internalized plastic particles could not be detected. Nevertheless, given their important role in ecosystems as a food source for a range of organisms, the adsorption of plastic particles to S. polyrhiza roots as detected in this study can result in the transfer of plastic particles to diverse herbivorous species within the ecosystem.

Aim Decreasing in the diversity and distribution of native submerged plants have been widely observed in recent decades. Global underwater darkening, which is mainly caused by radiation dimming and a decrease in transparency due to, e.g. eutrophication, has emerged as a general trend that strongly hampers the growth of submerged plants in lakes by decreasing the light available for photosynthesis. However, few studies have attempted to compare the responses of native and invasive submerged plants to underwater darkening. In this study, we aimed to compare the effects of light attenuation on the growth and photosynthesis traits of native and invasive submerged plants. Location East China. Method Through field investigations and a mesocosm experiment, the responses of functional traits of two representative native [water thyme (Hydrilla verticillata), Eurasian watermilfoil (Myriophyllum spicatum)] and one invasive [Carolina fanwort (Cabomba caroliniana)] plant species to various environmental factors, notably to underwater light attenuation, were studied. Results Underwater photosynthetically active radiation (PAR) exerted a substantial effect on the relative coverage and abundance of the three studied submerged plants in their natural freshwater habitats. Invasive C. caroliniana showed relatively superior growth (total biomass and relative growth rate) and photosynthesis traits (maximum quantum yield of photosystem II Fv/Fm, chlorophyll a content, chlorophyll b content and the ratio of Chl a and b contents) compared to the two native plants under low underwater PAR conditions. In contrast, under high underwater PAR conditions, C. caroliniana showed the opposite response. Main Conclusions Light attenuation inhibits the growth of native submerged plants but facilitates the growth of invasive plant species. Restoration of freshwater lakes by reducing deterioration from underwater darkening (for instance, by reducing of external nutrients loading) may therefore constrain the growth and spread of the invasive C. caroliniana.

Human-mediated transport beyond biogeographic barriers has led to the introduction and establishment of alien species in new regions worldwide. However, we lack a global picture of established alien species richness for multiple taxonomic groups. Here, we assess global patterns and potential drivers of established alien species richness across eight taxonomic groups (amphibians, ants, birds, freshwater fishes, mammals, vascular plants, reptiles and spiders) for 186 islands and 423 mainland regions. Hotspots of established alien species richness are predominantly island and coastal mainland regions. Regions with greater gross domestic product per capita, human population density, and area have higher established alien richness, with strongest effects emerging for islands. Ants and reptiles, birds and mammals, and vascular plants and spiders form pairs of taxonomic groups with the highest spatial congruence in established alien richness, but drivers explaining richness differ between the taxa in each pair. Across all taxonomic groups, our results highlight the need to prioritize prevention of further alien species introductions to island and coastal mainland regions globally. Analysis of eight taxonomic groups across 186 islands and 423 mainland regions reveals that those with the greatest gross domestic product per capita, human population density and area have the highest established alien species richness, with the strongest effects on islands.