In the wake of biological globalization, translocated species of high bio-engineering capacity increasingly change bottom topography of sedimentary coasts. A Vaucheria-taxon (Xanthophyceae) of unknown origin is spreading at the transition between intertidal and subtidal zones, while resident Vaucheria-species are confined to the upper shore in the Wadden Sea (European Atlantic). Near the island of Sylt, dense turfs of green filaments rapidly expanded over an area of 180 ha within 3 years. The unicellular filaments reach about 5 cm out of and 5 cm into the sediment. Felted rhizoids provide firm anchorage. Dry phytomass (up to 208 g m^-2) was similar to that of intertidal seagrass beds. Residual filaments overwinter in the sediment and give rise to renewed growth in late spring. In addition, oospores germinate. Fine particles are trapped by the turf during summer, generating laminated cohesive mud. Muddy hummocks arise up to 20 cm above ambient sand flats, alternating with troughs but gradually merge into coherent and pertinacious plateaus of mud. This shift in bottom topography and sediment composition may potentially change the mud balance of tidal basins, and the capacity of tidal flats in catching up with accelerating sea-level rise.

A survey of the exchange of freshwater gastropods mollusks between Europe and North America is provided. Several dozen species of snails migrated, during the last two centuries, in either direction across North Atlantic and this process is ongoing. The intensity of the faunal exchange is unequal since much more snail species have dispersed from North America to Europe than in the opposite direction. Two cases of “failed” invasions of North American lymnaeid snails to Europe are discussed. A species of pulmonate snails, Ampullaceana balthica (Linnaeus, 1758), is reported here as new for the malacofauna of Canada (and for the whole North America). This snail of European origin was found in June 2019 in a small lake in the vicinities of Rimouski Town (Québec, Canada). The taxonomic identification of the mollusks was confirmed by molecular analysis, with the studied specimens having two unique COI haplotypes, hitherto not found in Europe.

The Asian clam, Corbicula fluminea, is a broadly distributed and abundant invasive species, yet many aspects of its biology are not well understood. Based on previous research by other investigators, we hypothesized that abundance, population growth rate, and individual growth rate of C. fluminea would increase with temperature, chlorophyll-a, and dissolved oxygen. We sampled C. fluminea at two sites in the lower Columbia River (CR), USA. Modal progression analyses indicated a life span of 2–3 years. A generalized linear mixed model (GLMM) predicting the abundance of C. fluminea indicated a significant negative association with chlorophyll-a concentration, whereas a GLMM predicting the population growth rate of C. fluminea indicated a significant positive association with dissolved oxygen. The GLMM predicting the individual growth rate of C. fluminea indicated the individual growth rate was not significantly related to any individual environmental variable. Overall, these results emphasize that the biology of C. fluminea in the CR is similar in many regards to other populations studied in temperate regions globally, but that important spatial differences can occur between sites separated by 60 km within the same river system.

The non-indigenous tanaidacean crustacean Sinelobus vanhaareni Bamber, 2014 was first found in northern Europe in 2006 and has since spread to the northern Baltic Sea. Here, we surveyed the distribution of the species in different habitats in southwestern Finland, focusing on vegetated macroalgal and seagrass habitats (i.e., Fucus vesiculosus beds and Zostera marina meadows). We also evaluated its potential impacts by synthesizing current knowledge on the traits and ecology of the species, and identified knowledge gaps. We found that S. vanhaareni is now present throughout most of the southwestern Finnish coast, in a number of vegetated and non-vegetated substrates down to 25 m depth. Furthermore, the presence of egg-brooding females in most areas also confirms that the population is self-sustaining. The species is especially abundant in shallow macroalgal belts and eelgrass meadows, which are critical habitats for biodiversity, ecosystem functioning, and ecosystem service provisioning, highlighting the need to understand the effects of S. vanhaareni in these important ecosystems. Its presence on boat hulls and in marinas and harbours suggests that recreational boating may be a major spread vector, while drifting macroalgal fragments may also contribute to regional spread. At this stage of invasion, we found high overlap in epifaunal community composition in sites where S. vanhaareni was present and sites where it was absent. Based on the functional traits of S. vanhaareni and closely related species, we infer that it is likely part of the detritus-based pathway in benthic food webs. However, additional sampling and experiments are necessary to determine the true extent of its distribution and to quantify trophic links (through stable isotope analysis, gut content analysis, and experimental trials) to fully understand its effects on communities and trophic networks in the northern Baltic Sea.

Ancient Lake Poso in Central Sulawesi, Indonesia, is among the deepest lakes in Asia, and hosts a largely endemic fauna of fishes, crustaceans, and molluscs. Introduction of non-native fish species started at least a century ago to foster local fish production. Recent fieldwork suggests that introduction of non-native fishes is ongoing, including species that originate from the ornamental pet trade. These include the hybridogenic ornamental “flowerhorn” cichlid, a fish that spread rapidly in Sulawesi’s Malili Lakes, and the “golden cichlid”, Melanochromis auratus from African Lake Malawi. This popular aquarium species colonized Lake Poso even more rapidly than the flowerhorn, and is omnipresent at benthic habitats across most of the lake. Here, we list records of 17 non-native fish species from Lake Poso, present the first assessment of golden cichlid stomach contents outside of their native habitat, report the occurrences of non-native crustaceans, molluscs and plants, and discuss potential impacts on the native fauna and ecosystem. Most of the non-native species have established substantial populations, and it appears very plausible that the non-native fauna affects endemics. This is supported by the finding that golden cichlid stomachs contained a broad spectrum of items, including fish, their scales, fins, eggs and larvae, and various invertebrates. We conclude that non-native species introduction poses a substantial and increasing threat to the Lake Poso fauna, a major hotspot of aquatic biodiversity in the Wallacea region.

Plasticity in growth and life-history traits is an important attribute of non-native (NN) fishes, facilitating their adaptation to novel environments. Few studies have investigated geographical variations in multiple biological traits and the factors affecting the variations. In this study, variations in multiple biological traits of NN sailfin catfishes Pterygoplichthys spp. were investigated in the main river basins of the Guangdong and Hainan provinces of South China. The impacts of environmental factors on the biological traits were analysed using general linear modeling and an information-theoretic approach. Among-basin differences in population growth was observed, with richness of competitor fishes negatively affecting growth, maturity and reproductive traits – this suggests biotic resistance was mediated by competition with native fishes. These traits were positively affected by total phosphorus concentration, which is indicative of bottom-up effects, mediated by inorganic nutrients, potentially playing an important role in the invasion success of NN fish. In population level, a bet-hedging strategy was observed in sailfin catfishes under unfavourable environment conditions (e.g. Nangdujiang), whereas a “master-of-some” strategy was found under favourable conditions (e.g. Pearl River Delta and Western Basin). The results suggested that plasticity in multiple biological traits of sailfin catfishes is an important strategy to overcome changing environmental conditions in different rivers, and habitat-specific variations across river basins would reflect trade-offs amongst traits at the population level. Therefore, habitat-specific management measures, adapted to the invaded ecosystem’s features and the life-history strategy of the NN species, could provide an effective means to control invasive species.

Piaractus brachypomus is highly valued as an aquaculture and ornamental fish species. However, it is frequently considered as a non-native or invasive species. In Polish waters P. brachypomus is an incidental non-native species, most likely released by aquarists, and it is unable to overwinter or reproduce. Outside its native distributional range, this species has been recorded nearly world-wide. In regions where exist it is often confused with other species such as Piaractus mesopotamicus and Piaractus orinoquensis, possibly with Colossoma macropomum and their hybrids, and Pygocentrus nattereri. In this study, we provide a detailed taxonomic description and the most useful discriminative features for the species, of five specimens of P. brachypomus caught in water bodies in northwestern Poland (in 2002–2010), and a sample of 11 specimens obtained from laboratory culture (2012–2019) that originated from South America. The examinations included describing metric and meristic characters, the neurocranium structure, the dentition formula, parasite fauna, and species identification based on a mitochondrial COI sequence. The phylogenetic tree inferred using maximum likelihood showed that pirapitinga samples were nested within the Amazon Basin clade of P. brachypomus. This is the first molecular study in Europe and first detailed morphometric study (including the neurocranium) of this species from a non-native area of its distribution. Characters such as dentition can be used to discriminate among the genera Colossoma, Piaractus and Pygocentrus, while meristic characters such as lateral line scale counts, numbers of scale rows above and below the lateral line, pectoral and pelvic fin rays counts, and ventral-keel spine counts can be used to discriminate among species within the genus Piaractus. Nevertheless, morphometric characters do not seem to be an appropriate tool to distinguish closely related species in the genus Piaractus.