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.2026.21.2.188183

Authors: Marta Ronowicz, Bernabé Moreno, Zuzanna Szewel, Julia Więcławska, Olga Brocławik, Maciej Karol Mańko

Abstract: Calyptospadix cerulea Clarke, 1882 is a colonial athecate hydrozoan known for forming dense biofouling communities, having broad environmental tolerance and global yet taxonomically obscured distribution. Here, we confirm for the first time its presence in the Polish part of the Baltic Sea (Gulf of Gdańsk), marking a significant range expansion into the Baltic Proper. We support our morphology-based identification, with the first molecular data for C. cerulea, allowing its phylogenetic placement within a clade alongside Bimeria vestita Wright, 1859 and Cordylophora caspia (Pallas, 1771), therefore suggesting reassignment to the family Cordylophoridae. We also reviewed historical occurrence data of C. cerulea, spanning nearly 150 years of research, to provide up-to-date description of its distribution range. In addition, our in situ observations suggest that C. cerulea plays an important role in providing secondary substrate for number of species in benthic environments of the southern Baltic Sea. As C. cerulea is likely well-suited to the Baltic’s variable brackish conditions, its presence raises concerns about potential ecological impacts on native fouling communities and industrial infrastructure. Given its ecological plasticity and expanding range, we emphasize the need for continued monitoring and further research into its population dynamics, ecological interactions, and potential impacts.

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DOI: 10.3391/ai.2023.18.2.105240

Authors: Jakub Fedorčák, Peter Križek, Ján Koščo

Abstract: Within the genus Carassius Jarocki, 1822 , the crucian carp (C. carassius L., 1758) occurs naturally in the northern part of Middle Danube Basin (Austria, Morava, Slovakia). This species has the least concern status in this region, but observations in the last decades suggest that it is very close to extinction here. The distribution of crucian carp is limited to a small number of vanishing lentic habitats (oxbow lakes, marshlands). These biotopes are in the last stage of succession due to the drying up of the landscape and a reduction in the creation of new natural alluvial habitats. The non-native cyprinid, C. gibelio (Bloch, 1782), known as gibel carp and Prussian carp, has gradually become eudominant in a wide spectrum of habitats/biotopes since the 1960s Several biological adaptations of non-native species are generally considered the strong basis for the mass spreading in the invaded area. The other side of the expansion of non-native C. gibelio is affected by anthropic activities associated with fish farming, translocation and stocking the fish in open water ecosystems. In this study, we analysed historical scientific data on the distribution of Carassius spp. published from the 19th century to the present from the mentioned areas. The results suggest that the number of records of invasive C. gibelio has gradually increase in rivers, regulated channels and creeks, which could be considered as natural pathways of spreading. However, the presence of invasive C. gibelio in artificial biotopes (fishponds, reservoirs) is continuous from the 1960s. In the area mentioned, the artificial biotopes are managed by national fisheries associations and relate to the historical way of farming in Central and Eastern European countries. To show the current state of the fishing grounds of the Slovak Angling Association, we a created the distribution map based on the Carassius spp. catches recorded in last two decades.

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