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• Quagga mussels may affect biotic and abiotic characteristics of invaded reservoirs. • Quagga mussel establishment led to reduced cyanobacteria and diatom abundance. • Aphanizomenon sp. abundance decreased in quagga mussel invaded reservoirs. • Soluble reactive phosphorus concentrations increased in invaded reservoirs. • Changes in nutrients and phytoplankton communities may affect reservoir management. Invasive quagga mussels (Dreissena rostriformis bugensis) are an emerging threat to the functioning and management of freshwater ecosystems. Quagga mussels were first recorded in the UK in 2014 and have subsequently established at high densities in a number of major reservoirs. Through implementing a Progressive-Change BACIPS (Before-After-Control-Impact Paired Series) analysis, we found that the following trends were observed following quagga mussel establishment: reduced diatom and cyanobacteria abundances; increased soluble reactive phosphorus and reactive silica concentrations; and reduced abundances of Aphanizomenon sp., a potentially toxic cyanobacterium. We also found reservoirs with established quagga mussel populations experienced slightly increased overall chlorophyll a concentration but no changes in turbidity or Microcystis sp. abundance, which are often considered common indicators of dreissenid invasion. Our results show that Progressive-Change BACIPS analysis is a powerful tool which can be used to interrogate industry standard long-term datasets of water quality metrics in order to identify and quantify the impacts of invasive species when the approximate timeframe of species arrival is known. We also demonstrate that quagga mussels may have had significant effects on reservoir ecosystems which, primarily through their impacts on phytoplankton communities, may have implications for reservoir management. [Display omitted] [ABSTRACT FROM AUTHOR]

The invasion of zebra mussels, Dreissena polymorpha , into Western Europe and North America has driven widespread ecological change. Attachment of zebra mussels to the shell of native unionoid mussels has resulted in reductions in unionoid abundance and, in extreme cases, their localised extirpations. While the impacts of zebra mussels on infested unionoids are well documented, the possible benefits of the association to the zebra mussel have been little considered. We collected zebra mussels attached to unionoids and to inanimate structures. Zebra mussels attached to unionoids had significantly larger shells, higher standardized body mass and glycogen content than those attached to inanimate substrates, suggesting that D. polymorpha benefits from settling upon unionoids. The body condition of individual zebra mussels was negatively correlated with the number of zebra mussels attached to the unionoid, indicating intraspecific competition. Therefore, zebra mussels seem positively affected through attachment to unionoid mussels, but that these benefits decrease at higher densities of fouling. This association may offer advantages to the spread of zebra mussels within unionoid-rich systems, especially at sites with soft substrates and at the early stages of the invasion process where intraspecific competition is likely to be lower and benefits to the zebra mussels are higher. [ABSTRACT FROM AUTHOR]

Invasive non-native species (INNS) with marine or brackish origins have become increasingly common occupying freshwater habitats. The transition of INNS from marine or brackish water into physiologically stressful freshwater environments may be facilitated by compensatory growth and elevated feeding rates. In this study, we investigate the capacity of the Gulf wedge clam (Rangia cuneata), a brackish NNS that is spreading quickly across European waterways, to survive in freshwater conditions and consider its resultant impacts as an ecosystem engineer. To investigate the performance of R. cuneata under freshwater conditions, we compared the population structure, the physiological condition, and the growth of R. cuneata collected from its distributional limits in Great Britain. Feeding rate of R. cuneata was quantified by conducting a reciprocal transfer experiment with a two-way factorial design on individuals obtained from the freshwater and saline extremes. R. cuneata density was almost 10-fold higher at its most saline distributional limit (213 individual m−2, 3.1‰) compared to its most freshwater limit (22 individuals m−2, 1.2‰). The impaired physiological condition (18.7% lower relative soft tissue mass and 26.4% lower shell mass) and the lack of juvenile individuals also suggests that the R. cuneata inhabiting the freshwater extreme may not be able to maintain a persistent population over the long term. Although R. cuneata at its freshwater extreme were under stress, the per capita impacts caused by these individuals were not weakened at the suboptimal conditions, evidenced by their elevated growth and over four times as high relative clearance rate (0.28 L−1 g−1 h−1) compared to those from the saline limit (0.06 L−1 g−1 h−1). This study demonstrates that under suboptimal conditions, the physiological responses of INNS may result in elevated per capita effects which may lead to unexpected or under-estimated impacts on recipient ecosystems. Unlabelled Image • Invasive alien brackish Rangia cuneata can survive in freshwater conditions. • Clams in the freshwater site are under physiological stress. • Elevated growth and feeding rates were found in clams from the freshwater site. • The per capita impact from R. cuneata was >4× higher in suboptimal conditions. [ABSTRACT FROM AUTHOR]

We identified emerging scientific, technological, and sociopolitical issues likely to affect how biological invasions are studied and managed over the next two decades. Issues were ranked according to their probability of emergence, pervasiveness, potential impact, and novelty. Top-ranked issues include the application of genomic modification tools to control invasions, effects of Arctic globalization on invasion risk in the Northern Hemisphere, commercial use of microbes to facilitate crop production, the emergence of invasive microbial pathogens, and the fate of intercontinental trade agreements. These diverse issues suggest an expanding interdisciplinary role for invasion science in biosecurity and ecosystem management, burgeoning applications of biotechnology in alien species detection and control, and new frontiers in the microbial ecology of invasions. [ABSTRACT FROM AUTHOR]