DOI: 10.3391/ai.2026.21.2.187217

Authors: Mateusz Draga, Maciej Gąbka

Abstract: Light and temperature are critical factors for the growth of all plants, including invasive macrophytes. The high invasiveness of these species is often linked to their ability to outcompete native plants through greater shade tolerance and rapid growth at elevated temperatures. In our experimental study, we tested two hypotheses: (1) the high competitiveness of invasive alien macrophytes stems from their exceptional shade tolerance, and (2) although thermophilic invasive aquatic plants thrive in warm water, they retain the capacity to survive in colder conditions. To test these hypotheses, three invasive aquatic plant species: Elodea nuttallii, Cabomba caroliniana, and Vallisneria spiralis - were cultivated in two separate experiments: one testing low light conditions under constant temperature, and the other testing low temperature conditions under constant light. Each cultivation lasted seven weeks. Following this period, key morphological traits, including shoot length, number of offshoots, dry mass, and chlorophyll a content, were measured for each species. Our results show that all tested species were able to temporarily survive at 7 °C, although their growth was generally inhibited. E. nuttallii was the exception, exhibiting growth even at this low temperature. Moreover, V. spiralis and C. caroliniana demonstrated broad tolerance to varying light levels, while E. nuttallii thrived under low light conditions but exhibited reduced growth at higher intensities. Additionally, low temperature and light levels inhibited daughter ramet production in V. spiralis, while extremely low light induced partial necrosis in the lower parts of E. nuttallii shoots, possibly as a strategy to escape unfavorable light conditions. Overall, our research underscores the critical role of temperature in the development of invasive aquatic plants and confirms their high shade tolerance, a key factor in their competitiveness.

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DOI: 10.3391/ai.2026.21.1.181482

Authors: Mingkai Leng, Xiaodong Wu, Zhenzhen Feng, Xuguang Ge, Haoran Liu, Xing Wang, Haoyue Li, Wenhui Li

Abstract: The aquatic plant Myriophyllum aquaticum, native to South America, has been introduced to China as an aquarium ornamental plant species over the past 20 years and has now established itself as an invasive species in multiple regions of southern China. In the present study, we conducted a controlled pot experiment with Myriophyllum aquaticum planted at seven different water depths (0, 25, 50, 75, 100, 125, and 150 cm) to investigate its growth patterns and adaptive mechanisms in various aquatic environments. As expected, underwater light decreased exponentially with increasing water depth. Spectral analysis indicated significant attenuation across all wavelength bands, with the blue light band being reduced to a greater extent than the red light band, consequently leading to a gradual elevation in the red-to-blue ratio (Red/Blue) with depth, which has a significant effect on the survival rate of M. aquaticum. With an increase in water depth, the survival rate of M. aquaticum showed a decreasing trend; the plants did not survive at a depth of 150 cm. The effect of water depth on the growth and reproduction of M. aquaticum is evident. The growth indices, namely plant height, the number of stem nodes, internodes, the number of branches, the number of tillers, root length, wet weight, and the RGR were all shown to decrease with increasing water depth. Growth conditions gradually diminished with the increase in depth: the Chl-a content of the M. aquaticum leaves gradually decreased, and when the water depth was ≥ 50 cm, the chlorophyll synthesizing ability of the leaves gradually decreased. Increased water depth – and the corresponding stress of low light – resulted in an increase in the malondialdehyde content of the leaves. The results of this experiment demonstrate that M. aquaticum is more likely to become established in shallow-water areas (depth up to 25 cm).

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DOI: 10.3391/ai.2025.20.3.160924

Authors: Xiaolong Huang, Heyun Wang, Songyang Li, Leyang Xu, Zhaoshi Wu, Hu He, Kuanyi Li

Abstract: As global warming continues, increasing minimum winter temperatures may no longer limit the northward expansion of invasive species, particularly those from tropical zones. A mesocosm experiment with a chronosequence approach (space-for-time trade-off) was used to examine the effects of water level variation on the traits of the invasive aquatic plant water hyacinth [Pontederia crassipes (formerly Eichhornia crassipes)] collected from freezing, chilling and warm overwintering locations in China. We hypothesized that the phenotypic plasticity of the plant, particularly its ability to adjust its root morphology and topology in response to vernal water level rise, enhances its capacity to invade freshwater ecosystems. The results revealed significant plasticity in the response of the plants to water level, with plant traits such as total biomass, diaspore number, leaf area, specific leaf area, root length, and photosynthetic efficiency significantly increasing under a 10-cm water level, which can be regarded as a moderate overwintering water level. However, the plants from the warm location did not perform better than did those from the freezing or chilling locations, possibly because the harsh winter conditions reduced plant biomass but did not negatively affect the plants at the gene level. These findings highlight phenotypic plasticity in rooting behavior, which enables plant survival and growth during overwintering in the littoral zone, allowing P. crassipes to withstand low temperatures and to rapidly proliferate during the vernal water rise period. This study highlights the importance of early detection and management strategies to control the spread of P. crassipes, particularly given the trends in global climate change, which may facilitate its northward expansion. The use of P. crassipes as a model plant is recommended for studying the responses of invasive aquatic plants to global change in freshwater ecosystems.

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DOI: 10.3391/ai.2025.20.2.153557

Authors: Wen Xiong, Wei Zhang, Zhen Deng, Peter A. Bowler, Kang Chen, Baoqiang Wang

Abstract: The Yellow River is the second largest river in China and it supports a rich biodiversity and numerous endemic fish species (Atrilinea macrolepis, Brachymystax lenok tsinlingensis, and Hucho taimen). It is one of China’s most important freshwater aquaculture and mariculture regions, and many non-native species have been introduced into the region. This study provided the Yellow River Basin’s first and current list of non-native aquatic species including a total of 112 species comprised of 59 fishes, 27 aquatic plants, 21 Mollusca, three reptiles, one crustacean and one amphibian. The primary introduction pathway is aquaculture (69 species), followed by the aquarium and ornamental trade (30 species), forage (four species), unintentional introductions (four species), ecological restoration (two species), religious releases (two species), and one species for biocontrol. Asia is the primary geographic origin of non-native species (39 species), followed by North America (33 species), South America (16 species), Europe (10 species), Africa (nine species) and Oceania (five species). Many non-native species have become important species in local aquaculture, the aquarium and ornamental trade or for other human uses. Many non-native species have caused significant negative economic, ecological and societal impacts. More research, field investigations and new guiding policies should be applied for the effective control and management of non-native species in the Yellow River Basin.

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DOI: 10.3391/ai.2025.20.2.147751

Authors: Luciana Vieira Granthom-Costa, Luciana V. Resende de Messano, Luciana Altvater, Paula Spotorno, Ricardo Coutinho

Abstract: Marine bioinvasions are human-mediated events that have modified landscapes and altered the composition and structure of native communities. Arraial do Cabo is an Extractive Marine Protected Area located on the Southeastern Brazilian Coast with unique environmental features due to the influence of a coastal upwelling phenomenon. The presence of a small port complex probably facilitated the introduction of non-native species (NNS). This study compiled a list of NNS from Arraial do Cabo based on published and unpublished studies. Our findings compiled 45 non-native benthic species belonging to eight taxonomic groups: Rhodophyta (3); Porifera: Calcarea (3); Anthozoa (4); Serpulidae (2); Mollusca: Bivalvia (5) and Gastropoda (2); Cirripedia (4); Bryozoa (6) and Ascidiacea (16). Three of which occurred exclusively in Arraial do Cabo – Didemnum sp. carpet, Thylaeodus sp., and Tubastraea sp. – and 13 were re-examined and are now categorized as NNS. Since the distribution is based on environmental conditions of water, forty-four NNS were found in warmer waters and only one was exclusively recorded in sites exposed to the cold waters – the red algae Pyropia suborbiculata. Based on those results, we updated the list of NNS on the Brazilian coast from 77 to 99 benthic sessile NNS. Our results also provide a tool for a connected environmental network for private and public sectors in order to mitigate impacts in a high-value conservation area that can be considered a relevant NNS hotspot of the southeastern Brazilian coast.

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DOI: 10.3391/ai.2025.20.1.134814

Authors: Timothy S. Lee, Amy E. Fowler, Stacy A. Krueger-Hadfield, Chloe Gabriel, April M. H. Blakeslee

Abstract: Non-native foundation species may alter physical environments and provide habitat, thereby impacting recipient communities. Along the US east coast, we assessed biogeographic patterns of free-living and parasitic community diversity associated with the non-native red alga Gracilaria vermiculophylla, which is characterized by fixed (with holdfast) or free-floating thalli depending on the availability of hard substratum. In summer 2019, we surveyed 17 sites across 3 biogeographic regions. We used a random quadrat design to collect G. vermiculophylla and associated mobile macroinvertebrates per site, and we took abiotic measurements. We also haphazardly collected 100 Ilyanassa obsoleta snails per site to assess trematode diversity. In the lab, macroinvertebrates were removed from thalli and identified to lowest taxonomic level, and snails were dissected to determine trematode prevalence and diversity. Biotic and abiotic variables were analyzed for the best sets of predictors for species richness, abundance, and diversity of macroinvertebrates and trematodes across bioregions. Gracilaria vermiculophylla biomass was used as an offset in free-living analyses. Across all our US east coast sites, we detected 10,113 free-living (mobile) macroinvertebrates across 39 taxa. Three Gammaridean amphipods (Gammarus mucronatus, Ampithoe longimana, and Gammarus lawrencianus) comprised >50% of all detected organisms. We found biogeographic region to be a key predictor of macroinvertebrate abundance and richness. Trematode prevalence and richness were best explained by G. vermiculophylla biomass, while biogeographic region best explained diversity. As a widespread invader, our study provides evidence for associations that have formed as this foundation species has become established outside its native range. Over time, the presence and spread of G. vermiculophylla could continue to impact macroinvertebrate structure and diversity, and future work should directly compare macroinvertebrate communities with G. vermiculophylla to other foundation species along coastlines it is now common.

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DOI: 10.3391/ai.2025.20.1.154604

Authors: Amy E. Fowler, Alejandro Bortolus, João Canning-Clode, Tamara B. Robinson, Thomas W. Therriault

Abstract: The Eleventh International Conference on Marine Bioinvasions (ICMB-XI), held May 15–19, 2023, in Baltimore, Maryland, USA, convened 213 attendees from 24 countries to discuss the challenges and advancements in managing marine non-indigenous species (NIS). The conference emphasized the urgent need for international collaboration to address the increasing threats posed by marine bioinvasions, which transcend geopolitical boundaries. Participants explored six key themes through 119 oral presentations, 37 posters, and six keynote speakers, providing a platform for researchers, policymakers, and industry professionals to exchange knowledge and strategies. Notably, ICMB-XI implemented the first Code of Conduct for the Society for the Study of Marine Bioinvasions, promoting inclusivity and ethical scientific discourse. Here, we review articles published in Aquatic Invasions and Management of Biological Invasions based on research presented at ICMB-XI. Studies highlighted novel findings on species settlement dynamics, NIS ecological impacts, and advancements in detection methods such as environmental DNA monitoring. Research also examined the role of climate change in facilitating NIS, the influence of biofouling on NIS establishment, and the expansion of NIS into new ecological niches. Beyond scientific discussions, ICMB-XI celebrated the intersection of art and science through a collaboration with artist April Flanders, whose work communicated the impacts of marine invasions to broader audiences. The conference also provided travel awards and student achievement prizes to support early-career scientists. As ICMB-XI concluded, participants reinforced the need for sustained, large-scale efforts to mitigate marine bioinvasions through enhanced research, policy integration, and cross-sector collaboration. The next ICMB, scheduled for 2025 in Madeira, Portugal, aims to continue advancing the field and fostering international partnerships in marine bioinvasion management.

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DOI: 10.3391/ai.2024.19.3.135377

Authors: James T. Fumo, Brian S. Powell, Randall K. Kosaki, Alison R. Sherwood

Abstract: The cryptogenic nuisance alga Chondria tumulosa was first observed in 2016 at Manawai (Pearl and Hermes Atoll) in the Papahānaumokuākea Marine National Monument. It has since spread across the atoll, growing in thick mats and smothering benthic habitat. In September 2021 the species was observed at Kuaihelani (Midway Atoll), ~130 km to the northwest. Due to its growth habit and recent spread, considerable concern has been raised and management of the species may be warranted. We used publicly available oceanographic data and the Connectivity Modeling System software to assess how the potential for successful dispersal of C. tumulosa is affected by particle properties and oceanographic conditions. We found the likelihood of successful transit to be linked to particle density, oceanographic conditions at the time of release, and release location. Further modeling explicitly targeted the capacity of both reproductive tetraspores as well as drifting fragments to disperse. Model results indicated tetraspores of C. tumulosa are unlikely to survive the transit from Manawai to Kuaihelani, as none arrived at Kuaihelani above the depth limit of the species and those arriving below successfully settled at a rate of only 0.02%. In contrast, fragments modeled as rafting on marine flotsam such as macroalgae and marine debris settled at a rate of 3.85%. Rafting fragments also settled ~600 km further to the southeast (towards the Main Hawaiian Islands) than tetraspores. This study identified oceanographic conditions and particle properties likely to aid dispersal of C. tumulosa to Kuaihelani and suggests that fragments rafting on marine flotsam may accelerate its spread.

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DOI: 10.3391/ai.2024.19.2.124920

Authors: Nuoxi Wang, Chuyu Luo, Xiaodong Wu, Liang Chen, Xuguang Ge, Cheng Huang, Xiaowen Lin, Shunmei Zhu

Abstract: This study sought to investigate the invasive mechanism of Myriophyllum aquaticum by subjecting it to simulation experiments in varying water temperatures ranging from 0 °C to 30 °C. The results showed that water temperature considerably affected both the growth and reproduction of M. aquaticum. The optimal temperature range for the growth of M. aquaticum was 25‒30 °C. Although the growth of M. aquaticum was inhibited at temperatures between 0‒5 °C, this did not result in mortality. The stem nodes, branches, and diameter reached maximum values over a temperature range of 20‒25 °C. High-temperature stress at 30 °C led to a gradual decrease or disappearance of branches. Compared to the 0 °C, 5 °C, and 30 °C treatment groups, a temperature of 20 °C led to biomass accumulation and significantly higher values. M. aquaticum’s physiological activities were affected by temperature. Except for 10 °C and 15 °C, the catalase activity varied among different water temperatures. M. aquaticum catalase activity was maximal at 5 °C and minimal at 25 °C. Conversely, the synthesis of photosynthetic pigments was highest at 10 °C and 15 °C. The plant’s optimal temperature for growth was between 20 °C and 25 °C. When the temperature was <10 °C, M. aquaticum adapted to the water temperature’s potential damage. This plant has a notable ability to tolerate various temperatures.

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DOI: 10.3391/ai.2024.19.2.117212

Authors: Emanuele Pelella, Flaminia Mariani, Beatrice Questino, Simona Ceschin

Abstract: Freshwater ecosystems are among the most susceptible to biological invasions. The South American Ludwigia hexapetala is an aquatic plant that is becoming an increasing threat in many European waterbodies, recently including Italy. This study aimed to define the main parameters influencing the early colonization stage of L. hexapetala by overlapping the percentage cover of this species with environmental parameter data collected at 24 aquatic sites from six waterbodies in north-central Italy. At each site, chemical and physical characteristics of the water (temperature, pH, dissolved oxygen, conductivity, nitrates, phosphates, ammonia, depth, transparency), grain size of the substrate and level of anthropogenic disturbance were evaluated. The results showed that although L. hexapetala prefers shallow, warm, alkaline, moderately rich in ions and nutrients (especially phosphates) and oxygen-poor waters, it can grow in a wide range of environmental conditions. Moreover, as a typical invasive alien species, it spreads opportunistically in disturbed, unstable sites. Thus, L. hexapetala can invade freshwater habitats with different environmental conditions and subjected to anthropogenic disturbance. However, the results suggest that water depth may be a limiting factor in the early colonization stage of this species, which does not seem to be able to colonise waters deeper than 1 m in investigated sites, while it has been observed in significantly deeper waters in other European countries with a longer invasion history. Detecting the environmental parameters that most influence the growth of L. hexapetala becomes crucial both to identify the sites most at-risk of invasion in which to initiate timely monitoring actions for the species, and to be able to develop better management and control actions for this alien species in sites that have already been invaded.

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DOI: 10.3391/ai.2024.19.1.117155

Authors: Uhram Song, Seok Hyeon Oh, Byoung Woo Kim, Seonah Jeong, Hojun Rim

Abstract: Freshwater ecosystems are vulnerable to the invasion of exotic aquatic plant species because of the great likelihood of the introduction of exotic species, and the lack of barriers that block introduced species. Water hyacinth, Pontederia crassipes Mart., is one of the world’s most invasive alien plant species damaging freshwater ecosystems worldwide. Here, we monitored the water hyacinth population on Jeju island, Korea, to assess current invasion risks. Furthermore, we investigated how water hyacinth affects water pH because pH is an important determinant of the distribution of other aquatic plants, and thus a good indicator of aquatic ecosystem health. Water containing water hyacinth had a pH of 5.3, while that with water hyacinth and soil had a pH of 4.8 72 hours after the start of the experiment. Water hyacinth extracts contained shikimic acid, stearic acid, and palmitic acid, which are possible compounds that caused a decline in water pH. Water hyacinth also inhibited the growth of the aquatic plant species, Spirodela polyrhiza and Lemna perpusilla. These results imply that invasion of water hyacinth adversely impacts the abiotic and biotic characteristics of aquatic ecosystems. Moreover, monitoring the water hyacinth population suggests that this invasive aquatic plant overwinters on Jeju island. Therefore, regular monitoring and subsequent control of water hyacinth population can prevent its expansion in the aquatic habitats of Jeju island and the southern region of the Korean peninsula.

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DOI: 10.3391/ai.2023.18.3.104556

Authors: Sungtae Kim, Cheol Yu, Jennifer Ruesink, Jae-Sang Hong

Abstract: Smooth cordgrass (Spartina alterniflora Loisel.), an aggressive non-native species worldwide, colonized tidal flats on the west coast of Korea in two regions differing in tidal amplitude between 1990–2004. By the time of our study in 2015, expansion had occurred both clonally and through formation of new patches, providing an opportunity to determine intertidal range, which is a key component of understanding the threat posed by S. alterniflora through competition with native halophytes or transformation of unstructured mudflat. At Ganghwa (5.69 m tidal range), S. alterniflora ranged from 3.52 to 1.34 m above Mean Sea Level (MSL). At Jindo (2.02 m tidal range), S. alterniflora ranged from 1.57 to -0.18 m relative to MSL. Thus, a wider absolute intertidal range was occupied by S. alterniflora at the megatidal vs mesotidal region, but the lower limit of S. alterniflora did not extend below MSL under megatidal conditions, a pattern that now appears to emerge consistently in both the native and introduced range. In both study regions, S. alterniflora occurred at the same elevations as other salt marsh plants, occupying an upper zone with Phragmites australis (non-native) and middle zone with several native species including Suaeda japonica. S. alterniflora occurred below native marsh vegetation at all sites, which would result in transformation of the extensive mudflats along the Korean coast.

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DOI: 10.3391/ai.2023.18.1.103610

Authors: Wen Xiong, Dong Xie, Qiang Wang, Hui Wang, Zhigang Wu, Heying Sun, Tao Li, Peter A. Bowler

Abstract: Poyang Lake is the largest freshwater lake in China and sustains a high level of biodiversity in the mid-reach area of the Yangtze River watershed. Poyang Lake is also one of the most important aquaculture regions in China, and a great number of non-native species have been introduced into it. We present a current and well-documented list of the non-native species of plants, molluscs, crustaceans, fishes, reptiles, and amphibians currently found in Lake. We found that there are 103 non-native species (83 vascular plants, 12 fishes, three crustacea, two molluscs, two reptiles and one amphibian) that have invaded Poyang Lake Basin, of which 96 non-native species were introduced after 2000. The invasion rate of non-native species reached 4.36 species year-1, which is the highest invasion rate recorded in freshwater ecosystems. The primary pathways of introduction are through the ornamental trade and unintentional escapes (30 species each, respectively), followed by food (19), aquaculture (15), forage grass (four), medicinal and oil (two, respectively), and biocontrol (one). The origins of non-native species are North America (29.12%), Asia (25.24%), South America (20.38%), Africa (18.44%), Europe (5.82%) and Oceania (0.97%). Many non-native species provide significant support for the rapid development of the local economy (such as aquaculture). However, many non-native species pose a great threat to local biodiversity and societal development. More studies that include monitoring and the development of strategies for managing and eliminating non-native species in Poyang Lake are needed.

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