Non-native Aquatic Plants Research Articles

Alien aquatic plants in Poland: Temporal and spatial distribution patterns and the effects of climate change

Distribution of alien aquatic plants in European freshwater ecosystems is still not fully recognized. Little is also known about the impact of climatic factors on the expansion of particular neophyte species in freshwater ecosystems. In this article, we present the first comprehensive assessment of the occurrence of non-native aquatic vascular plants in Poland (CE Europe), with a particular focus on: (1) inventory of the species, (2) temporal and spatial changes in their distribution, and (3) the climate impact on species occurrence and diversity. For this purpose, we collected both published and unpublished data on alien macrophytes occurrence in Poland covering past 70 years. In order to investigate the mechanism of alien aquatic plant expansion, climate data from 24 meteorological stations were analyzed. Redundancy analysis (RDA) was used to analyze the relationship between species composition and microclimate variables. In addition, Generalized Additive Model (GAM) was used to examine the response curves of neophyte species to temperature parameters.In total, we found records of 15 neophytes of alien aquatic plant taxa in Poland, including 14 species and collective taxon of Nymphaea cultivars. The most frequent was Elodea canadensis (over 25,000 records). Excluding this species, we counted more than 300 records of the occurrence of alien aquatic plants, of which three (E. nuttallii, Azolla filiculoides and Lemna turionifera) were the most abundant. Ten species occurred only in isolated sites. In addition, analyses showed a substantial increase in the number of the aquatic neophyte sites in the last 20 years that could be linked with the raised average monthly and yearly air temperatures in Poland.Our results showed a strong relationship between raised average temperatures in Poland and the spread of some species, e.g. Azolla filiculoides, while other species such as Elodea nuttallii and Lemna turionifera expanded irrespectively of this factor. The occurrence of some species (e.g. Vallisneria spiralis, Hygrophila polysperma) was exclusively associated to high thermally altered or thermally contaminated waters, and thus was limited to only a small part of the country. Our results confirm the major role of elevated temperatures (mean annual temperatures and minimum monthly temperatures) and thermally polluted freshwater ecosystems in the distribution of alien aquatic plants.

Checklist of Non-Native Aquatic Plants in Up, Middle and Downstream of Brantas River, East Java, Indonesia

Checklist of Non-Native Aquatic Plants in Up, Middle and Downstream of Brantas River, East Java, Indonesia

Scanning the Horizon for Potential Nonnative Aquatic Plant and Algae Arrivals to the Pacific Northwest

Scanning the Horizon for Potential Nonnative Aquatic Plant and Algae Arrivals to the Pacific Northwest

Identifying and Managing Areas under Threat in the Iberian Peninsula: An Invasion Risk Atlas for Non-Native Aquatic Plant Species as a Potential Tool.

Predicting the likelihood that non-native species will be introduced into new areas remains one of conservation's greatest challenges and, consequently, it is necessary to adopt adequate management measures to mitigate the effects of future biological invasions. At present, not much information is available on the areas in which non-native aquatic plant species could establish themselves in the Iberian Peninsula. Species distribution models were used to predict the potential invasion risk of (1) non-native aquatic plant species already established in the peninsula (32 species) and (2) those with the potential to invade the peninsula (40 species). The results revealed that the Iberian Peninsula contains a number of areas capable of hosting non-native aquatic plant species. Areas under anthropogenic pressure are at the greatest risk of invasion, and the variable most related to invasion risk is temperature. The results of this work were used to create the Invasion Risk Atlas for Alien Aquatic Plants in the Iberian Peninsula, a novel online resource that provides information about the potential distribution of non-native aquatic plant species. The atlas and this article are intended to serve as reference tools for the development of public policies, management regimes, and control strategies aimed at the prevention, mitigation, and eradication of non-native aquatic plant species.

Ecological and Economic Impacts of Alien Invasive Yellow Flag (Iris pseudacorus L.) in China

Non-native aquatic plants can alter the physiochemical condition of habitats and can have negative ecological and economic impacts. Thus, understanding the characteristics of non-native aquatic plant species is important as a foundation for the conservation of biodiversity and environmental management. The yellow flag (Iris pseudacorus) is an emergent aquatic plant native to Africa, northwest Asia, and Europe that has been introduced through the aquarium trade to all continents except Antarctica. This species has recently been brought into China and it has established large and widespread naturalized populations causing serious ecological and environmental problems. Unfortunately, information about the yellow flag in China is very scarce. We summarize the introduction pathways, current distribution, and ecological impacts of the yellow flag through field surveys and a review of the literature. We hope that this study can provide useful information for researchers and wetland managers involved with non-native emergent plants in China and other regions.

Climate change may exacerbate the risk of invasiveness of non-native aquatic plants: the case of the Pannonian and Mediterranean regions of Croatia

Non-native aquatic plants are amongst the major threats to freshwater biodiversity and climate change is expected to facilitate their further spread and invasiveness. To date, in Croatia, no complete list of non-native extant and horizon aquatic plants has been compiled nor has a risk screening been performed. To address this knowledge gap, 10 extant and 14 horizon aquatic plant species were screened for their risk of invasiveness in the Pannonian and Mediterranean regions of Croatia under current and predicted (future) climate conditions. Overall, 90% and 60% of the extant species were classified as high risk for the Pannonian and Mediterranean regions, respectively, under both climate scenarios. Of the horizon species, 42% were classified as high risk under current conditions and, under climate change, this proportion increased to 78%. The ‘top invasive’ species (i.e. scored as very high risk) under both climate conditions and for both regions were extant Elodea nuttallii and horizon Lemna aequinoctialis. The horizon Hygrophila polysperma was very high risk for the Mediterranean Region under current climate conditions and for both regions under projected climate conditions. Azolla filiculoides, Elodea canadensis, Egeria densa and Utricularia gibba were also classified as high risk under current climate conditions and, after accounting for climate change, they became of very high risk in both regions. Further, Gymnocoronis spilanthoides and Lemna minuta were found to pose a very high risk under climate change only for the Pannonian Region. It is anticipated that the outcomes of this study will contribute to knowledge of the invasiveness of aquatic plants in different climatic regions and enable prioritisation measures for their control/eradication.

Improving chemical control of nonnative aquatic plants in run-of-the-river reservoirs

AbstractCurrent dam discharge patterns in Noxon Rapids Reservoir reduce concentration and exposure times (CET) of herbicides used for aquatic plant management. Herbicide applications during periods of low dam discharge may increase herbicide CETs and improve efficacy. Applications of rhodamine WT dye were monitored under peak (736 to 765 m3 s−1) and minimum (1.4 to 2.8 m3 s−1) dam discharge patterns to quantify water-exchange processes. Whole-plot dye half-life under minimal discharge was 33 h, a 15-fold increase compared with the dye treatment during peak discharge. Triclopyr concentrations measured during minimum discharge within the treated plot ranged from 214 ± 25 to 1,243 ± 36 µg L−1 from 0 to 48 h after treatment (HAT), respectively. Endothall concentrations measured during minimum discharge in the same plot ranged from 164 ± 78 to 2,195 ± 1,043 µg L−1 from 0 to 48 HAT, respectively. Eurasian watermilfoil (Myriophyllum spicatum L.) occurrence in the treatment plot was 66%, 8%, and 14% during pretreatment, 5 wk after treatment (WAT), and 52 WAT, respectively. Myriophyllum spicatum occurrence in the nontreated plot was 68%, 71%, and 83% during pretreatment, 5 WAT, and 52 WAT, respectively. Curlyleaf pondweed (Potamogeton crispus L.) occurrence in the treatment plot was 29%, 0%, and 97% during pretreatment, 5 WAT, and 52 WAT, respectively. Potamogeton crispus increased from 24% to 83% at 0 WAT to 52 WAT, respectively, in the nontreated plot. Native species richness declined from 3.3 species per point to 2.1 in the treatment plot in the year of treatment but returned to pretreatment numbers by 52 WAT. Native species richness did not change during the study in the nontreated reference plot. Herbicide applications during periods of low flow can increase CETs and improve control, whereas applications during times of high-water flow would shorten CETs and could result in reduced treatment efficacy.

Importation of Dragonfly Nymphs (Odonata: Anisoptera) to Control Mosquito Larvae (Diptera: Culicidae) in Southern Maine

A long-standing program in Maine promotes stocking of dragonfly (Odonata) nymphs for biological control of nuisance and vector mosquitoes. Currently the only sources of dragonflies for stocking are out-of-state biological supply companies. In 2 dragonfly shipments from suppliers in Massachusetts and North Carolina, we determined that 6.8% and 38.5% of species, respectively, were not native to Maine. In an experiment of stocking efficacy, we introduced 4, 2, or 0 dragonfly nymphs into artificial pools in a forest habitat and found no differences in mosquito larvae counts among treatments. While the motivation for using dragonflies as biological control agents is commendable, the practice may be ineffective, and risks accidental introductions of non-native aquatic plants and animals in water used for shipping.

Multiscale collection and analysis of submerged aquatic vegetation spectral profiles for Eurasian watermilfoil detection

The ability to differentiate a non-native aquatic plant, Myriophyllum spicatum (Eurasian watermilfoil or EWM), from other submerged aquatic vegetation (SAV) using spectral data collected at multiple scales was investigated as a precursor to mapping of EWM. Spectral data were collected using spectroradiometers for SAV taken out of the water, from the side of a boat directly over areas of SAV and from a lightweight portable radiometer system flown from an unmanned aerial system (UAS). EWM was spectrally different from other SAV when using 651 spectral bands collected in ultraviolet to near-infrared range of 350 to 1000 nm but does not provide a practical system for EWM mapping because this exceeds the capabilities of available airborne hyperspectral imaging systems. Using only six spectral bands corresponding to an available multispectral camera or eight wetlands-centric bands did not reliably differentiate EWM from other SAV and assemblages. However, a modified version of the normalized difference vegetation index (mNDVI), using a ratio of red-edge to red light, was significantly different among dominant vegetation groups. Also, averaging the full range of spectral to 65 10-nm wide bands, similar to available hyperspectral imaging systems, provided the ability to identify EWM separately from other SAV. The UAS-collected spectral data had the lowest remote sensing reflectance versus the out-of-water and boatside data, emphasizing the need to collect optimized data. The spectral data collected for this study support that with relatively clear and calm water, hyperspectral data, and mNDVI, it is likely that UAS-based imaging can help with mapping and monitoring of EWM.

New county records in Texas (U.S.A.) for the invasive aquatic plant Hygrophila polysperma (Acanthaceae)

This report documents three new county records for the non-native aquatic plant Hygrophila polysperma in Texas. A brief background history of the species occurrence in Texas is also provided.

Predicting the risk of aquatic plant invasions in Europe: How climatic factors and anthropogenic activity influence potential species distributions

Predicting where species invasions will occur is one of the greatest challenges in conservation. Freshwater ecosystems are very vulnerable to the introduction of non-native species for two reasons: (1) there are many routes of introduction by which non-natives can arrive in freshwater systems; and, (2) freshwater systems are heavily impacted by a wide variety of human activities. Non-native aquatic plants can have harmful effects if they change habitat conditions, alter ecosystem functioning, and/or become key primary producers in invaded ecosystems. In this study, we focused on the potential distribution of non-native aquatic plants in Europe. The main objectives were to (1) identify environmentally suitable areas into which focal species could potentially spread; (2) generate a combined risk map for all the focal species and for the ten most harmful species in Europe; and (3) identify the main physicochemical characteristics of the areas at greatest risk. The results revealed that the potential distributions of non-native species were best predicted by climatic factors, notably by temperature-related variables. Anthropogenic activity was also a major contributor to the distribution patterns of all the non-native species examined. Areas experiencing high levels of eutrophication, a phenomenon that is strongly associated with anthropogenic activity, were among those at greatest risk of invasions. The approach presented here was intended to be broadly applicable. For example, it could be used to look at other taxonomic groups, regions, and/or systems. The overarching aim is to provide an effective basis for developing and implementing management and control strategies that can mitigate the effects of current invasions and prevent future ones.

Assessing threats of non-native species to native freshwater biodiversity: Conservation priorities for the United States

Non-native species pose one of the greatest threats to native biodiversity, and can have severe negative impacts in freshwater ecosystems. Identifying regions of spatial overlap between high freshwater biodiversity and high invasion pressure may thus better inform the prioritization of freshwater conservation efforts. We employ geospatial analysis of species distribution data to investigate the potential threat of non-native species to aquatic animal taxa across the continental United States. We mapped non-native aquatic plant and animal species richness and cumulative invasion pressure to estimate overall negative impact associated with species introductions. These distributions were compared to distributions of native aquatic animal taxa derived from the International Union for the Conservation of Nature (IUCN) database. To identify hotspots of native biodiversity we mapped total species richness, number of threatened and endangered species, and a community index of species rarity calculated at the watershed scale. An overall priority index allowed identification of watersheds experiencing high pressure from non-native species and also exhibiting high native biodiversity conservation value. While priority regions are roughly consistent with previously reported prioritization maps for the US, we also recognize novel priority areas characterized by moderate-to-high native diversity but extremely high invasion pressure. We further compared priority areas with existing conservation protections as well as projected future threats associated with land use change. Our findings suggest that many regions of elevated freshwater biodiversity value are compromised by high invasion pressure, and are poorly safeguarded by existing conservation mechanisms and are likely to experience significant additional stresses in the future.

Water brownification may not promote invasions of submerged non-native macrophytes

Some environmental factors, such as brownification and eutrophication, may influence the successful invasions of non-native submerged macrophytes. However, few studies have focused on how interactions between these factors influence the performance of exotic submerged plants. Here, we conducted an experiment in 60 indoor containers (170 l) over 68 days using the native species Hydrilla verticillata (L. f.) Royle and the non-native species Elodea nuttallii (Planch.) St. John to test the effects of brownification, eutrophication and their interactions on the growth and competition of native and non-native aquatic plants. Our results showed that the biomass of both H. verticillata and E. nuttallii increased in the brown water treatment and that eutrophication and water brownification did not lead to a shift from a native species-dominated system to a non-native-dominated system. However, brown water treatment decreased the relative competitive ability of E. nuttallii, and this decrease was exacerbated when brown water and nutrient treatments were combined. Our results indicated that some environmental factors, such as water brownification, eutrophication and their interactions, may not benefit the competition of some non-native submerged macrophytes. Further studies with more species are needed to corroborate these conclusions.

A preliminary assessment of the role of aquarium plant trade in the spread of non-native aquatic plants in South Africa: A DNA barcoding approach

A preliminary assessment of the role of aquarium plant trade in the spread of non-native aquatic plants in South Africa: A DNA barcoding approach

Impact of native and non-native aquatic plants on methane emission and phytoplankton growth

Freshwater plants affect the ecosystem functioning of shallow aquatic ecosystems. However, because native plants are threatened by environmental change such as eutrophication, global warming and biological invasions, continued ecosystem functioning may be at risk. In this study, we explored how the growth of native and non-native plant species in eutrophic, warm conditions impacts two plant ecosystem functions: regulation of phytoplankton growth and methane emission. We expected that plants would inhibit phytoplankton growth, while for methane emission both inhibition and stimulation are possible. We conducted an outdoor experiment using monocultures of four native and four non-native freshwater plant species planted at three different densities, as well as a no-plant control. Monocultures of each species were planted in 65 L mesocosms and after three weeks of acclimatisation each mesocosm was inoculated with phytoplankton. Subsequently, we added nutrients twice a week for eight weeks, before harvesting the plant biomass. During these eight weeks, we measured chlorophyll-a concentration thirteen times and the diffusive methane emissions once after four weeks. The mesocosms amplified the temperature of a warm summer so that plants were exposed to higher-than-average temperatures. We found that five plant species lost biomass, two species increased their biomass only at the highest initial plant density (native Myriophyllum spicatum and non-native Lagarosiphon major) and a single species increased its biomass at all densities (on average 14 times its initial mass; amphibious non-native Myriophyllum aquaticum). Overall, the mean biomass change of non-natives was positive, whereas that of natives was negative. This difference in biomass change between native and non-native plants did not relate to overall differences in phytoplankton mass or diffusive methane emissions. In mesocosms where submerged plant species gained biomass, chlorophyll-a concentration was lower than in the noplant control and mesocosms with biomass loss. Diffusive methane emissions were highest in mesocosms where plants lost considerable biomass, likely because it increased substrate availability for methanogenesis. However, mesocosms where plant biomass increased had emissions similar to the no-plant control, hence we found no inhibitory effects of plant presence on diffusive methane emission. We conclude that plant growth in eutrophic, warm conditions varies strongly with plant identity. Our results furthermore suggest that plant identity determines whether the replacement of native by non-native freshwater plants will alter ecosystem functions such as regulation of phytoplankton growth and methane emission.

Native and non-native aquatic plants of South America: comparing and integrating GBIF records with literature data

The Global Biodiversity Information Facility (GBIF) is at the moment one of the largest and most widely used biodiversity databases. Nevertheless, there are still some limitations, e.g. in terms of plant species status (native vs. non-native) and geographic resolution of records. At the same time, it is well known that alien plant invasions in inland freshwaters can alter community structure, ecosystem functions and services with significant negative impacts on biodiversity and human activities. We assessed if the GBIF database has a geospatial homogeneous information for native and non-native aquatic plant species for South America and whether or not literature resources not yet digitalized (floras, checklists and other papers) could provide additional information. We selected a set of 40 native and 40 non-native aquatic species. These 80 species included a sub-set of 40 alien species previously evaluated with the USAqWRA scheme (US Aquatic Weed Risk Assessment). Species with non-reliable identification, duplicates of the same collection, records poorly georeferenced were removed from the dataset. New records were manually compiled through classical literature research. All the georeferenced records (GBIF + literature) were used for the mapping and the comparative analysis. As a result, we can conclude that the two datasets provide quite significantly different information and the combination of the two offers new information that would not exist in a single data source. Nevertheless, a careful quality evaluation of the primary information, both in the case of literature and GBIF should be conducted, before the data is used for further analyses.

Invasion Risk in a Warmer World: Modeling Range Expansion and Habitat Preferences of Three Nonnative Aquatic Invasive Plants

AbstractBiological invasions and climate change pose two of the most important challenges facing global biodiversity. Of particular importance are aquatic invasive plants, which have caused extensive economic and environmental impacts by drastically altering native biodiversity and ecosystem services of freshwater wetlands. Here, we used the maximum entropy model, Maxent, to model the potential range expansion of three nonnative aquatic invasive plants: alligatorweed, limnophila, and giant salvinia, throughout the continental United States under current, 2030 to 2059 (2040), and 2070 to 2099 (2080) climate scenarios. Maxent is a popular method to model predicted current and future species distributions based on biogeography and climate. Alligatorweed, limnophila, and giant salvinia are noxious invaders of freshwater habitats in the southeastern United States and cause economic and ecological loss. In addition, we analyzed each species' habitat preference based on wetland type, occurrence in man-made habitats, and distance to the nearest stream to better understand what future habitats are at risk and how these species spread. Our results show that in 2040 and 2080 climate scenarios, all three species have the potential to increase their range throughout the northeastern United States and as far as New York and Massachusetts. The spatial distribution of alligatorweed was primarily determined by precipitation of the warmest quarter (15.8%), limnophila was primarily determined by precipitation of the warmest quarter (52.2%) and mean temperature of the coldest quarter (21.8%), and giant salvinia was primarily determined by the mean temperature of the coldest quarter (24.3%). All three species were found significantly more frequently in lakes and ponds than in other freshwater habits. Giant salvinia was found significantly more often in man-made wetland habitats. In order to reduce the detrimental impacts of these species, land managers in the northeastern United States should concentrate early detection and rapid response management in lakes, ponds and man-made wetland habitats.

Managing the introduction and spread of non-native aquatic plants in the Laurentian Great Lakes: a regional risk assessment approach

Risk assessment tools for non-native species can avert ecological and economic harm when they inform regulatory or voluntary management actions that seek to reduce the probability of introducing high-risk species. The Laurentian Great Lakes region contains many aquatic invasive plants, non-native species whose introduction causes economic or environmental harm or harm to human health. Additionally, new species continue to arrive, including through trade (e.g., aquarium, water garden). Currently, each Great Lakes jurisdiction manages a separate risk assessment program, leading to a regional situation with diverse assessment methods and large discrepancies in assessed and regulated species. Because the Great Lakes ecosystem crosses state and national borders, each jurisdiction will be best protected when all jurisdictions prevent the import of potentially harmful species. We have modified an existing risk assessment tool for use across the Great Lakes Basin to assess the invasion risks posed by aquatic plants. The tool comprises 38 questions, with points associated with each response that are summed to give a total score. We assessed all known established aquatic plant species in the Great Lakes (n=40) and found this score to be positively correlated with invasiveness, allowing thresholds to be identified that distinguish between invasive and non-invasive species with 84% to 90% accuracy. Assessing species proposed for introduction with this tool, and using these thresholds to determine acceptable risk, could reduce the number of future invasions. If widely adopted, this risk assessment tool would enable a common suite of species to be regulated and thus a more effective approach to reducing the risk of future invasions. Regional risk assessment approaches should reduce the threat of invasive species where environmental and climate conditions are relatively consistent across jurisdictional boundaries.

Evaluating stakeholder awareness and involvement in risk prevention of aquatic invasive plant species by a national code of conduct

In 2010, Dutch stakeholders signed a code of conduct to prevent the introduction and spread of aquatic invasive plant species. This voluntary agreement between the government and horticulture sector (i.e. plant nurseries and retailers) has the objective to ban the sale of invasive species and to increase public awareness and stakeholder involvement in measures to prevent new introductions of potential invaders. Public outreach campaigns included flyers and posters displayed in stores and labelling of non-native plant species with warning logos and messages on harmful effects and appropriate disposal. We evaluated several measures issued in the Dutch code of conduct by performing ex ante a n d ex posterior surveys and interviews with relevant stakeholder groups. Compliance of retailers and producers concerning species on sale and proper labelling was monitored annually by the Netherlands Food and Consumer Product Safety Authority. Interviews with aquarists and water gardeners provided the first quantitative evidence in the Netherlands that 2–3% of these hobbyists deliberately introduced non-native aquatic plants in surface water. A survey of retail professionals identified limited availability of information and lack of salesman’s knowledge on the species lists issued in the code of conduct as major impediments for their engagement. Furthermore, low frequency of meetings and lack of guidance were major obstacles identified by the partners assembled in the code of conduct. Overall, compliance to species bans showed promising results, however, problems were identified with correct labelling of species. We conclude by listing opportunities to improve voluntary regulations for preventing non-native species introductions.

Long-term macrophyte mapping documents a continuously shift from native to non-native aquatic plant dominance in the thermally abnormal River Erft (North Rhine-Westphalia, Germany)

Abstract Macrophyte mappings of a 37 km stretch of the thermally abnormal Erft River in 2003, 2005, 2007, 2011 and 2013 documented the presence of nine alien (Azolla filiculoides, Egeria densa, Eichhornia crassipes, Hydrocotyle ranunculoides, Hygrophila polysperma, Lemna minuta, Myriophyllum aquaticum, Pistia stratiotes and Vallisneria spiralis) in addition to 15 native species. During the study period, the number of native plant species decreased significantly in the river sections, while the number of alien species remained constant. The relative plant mass (RPM) of native species decreased from 67 to 33%, while that of the alien species increased. Only two of the nine reported alien species (V. spiralis and P. stratiotes) increased their abundances within the study period and became the most dominant species in the Erft River, while the other introduced species did not show mass development. The highest decline in RPM have been found for native Sparganium emersum and alien E. densa. Summarizing, the evergreen alien V. spiralis and recently P. stratiotes were the most successful invader within this thermally abnormal river since 2003, most likely profiting from the high winter temperatures >10 °C and displacing native vegetation, particularly formerly widespread native S. emersum.