Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Cuthbert, R. N., Pattison, Z., Taylor, N. G., Verbrugge, L., Diagne, C., Ahmed, D. A., Leroy, B., Angulo, E., Briski, E., Capinha, C., Catford, J. A., Dalu, T., Essl, F., Gozlan, R. E., Haubrock, P. J., Kourantidou, M., Kramer, A. M., Renault, D., Wasserman, R. J., & Courchamp, F. Global economic costs of aquatic invasive alien species. Science of the Total Environment, 775, (2021): 145238, https://doi.org/10.1016/j.scitotenv.2021.145238.

Description: Much research effort has been invested in understanding ecological impacts of invasive alien species (IAS) across ecosystems and taxonomic groups, but empirical studies about economic effects lack synthesis. Using a comprehensive global database, we determine patterns and trends in economic costs of aquatic IAS by examining: (i) the distribution of these costs across taxa, geographic regions and cost types; (ii) the temporal dynamics of global costs; and (iii) knowledge gaps, especially compared to terrestrial IAS. Based on the costs recorded from the existing literature, the global cost of aquatic IAS conservatively summed to US$345 billion, with the majority attributed to invertebrates (62%), followed by vertebrates (28%), then plants (6%). The largest costs were reported in North America (48%) and Asia (13%), and were principally a result of resource damages (74%); only 6% of recorded costs were from management. The magnitude and number of reported costs were highest in the United States of America and for semi-aquatic taxa. Many countries and known aquatic alien species had no reported costs, especially in Africa and Asia. Accordingly, a network analysis revealed limited connectivity among countries, indicating disparate cost reporting. Aquatic IAS costs have increased in recent decades by several orders of magnitude, reaching at least US$23 billion in 2020. Costs are likely considerably underrepresented compared to terrestrial IAS; only 5% of reported costs were from aquatic species, despite 26% of known invaders being aquatic. Additionally, only 1% of aquatic invasion costs were from marine species. Costs of aquatic IAS are thus substantial, but likely underreported. Costs have increased over time and are expected to continue rising with future invasions. We urge increased and improved cost reporting by managers, practitioners and researchers to reduce knowledge gaps. Few costs are proactive investments; increased management spending is urgently needed to prevent and limit current and future aquatic IAS damages.

Description: The authors acknowledge the French National Research Agency (ANR-14-CE02-0021) and the BNP-Paribas Foundation Climate Initiative for funding the InvaCost project that allowed the construction of the InvaCost database. The present work was conducted following a workshop funded by the AXA Research Fund Chair of Invasion Biology and is part of the AlienScenarios project funded by BiodivERsA and Belmont-Forum call 2018 on biodiversity scenarios. RNC is funded through a Humboldt Research Fellowship from the Alexander von Humboldt Foundation. DAA is funded by the Kuwait Foundation for the Advancement of Sciences (KFAS) (PR1914SM-01) and the Gulf University for Science and Technology (GUST) internal seed fund (187092). CD was funded by the BiodivERsA-Belmont Forum Project AlienScenarios (BMBF/PT DLR 01LC1807C). EA was funded by the AXA Research Fund Chair of Invasion Biology of University Paris Saclay. CC was supported by Portuguese National Funds through Fundação para a Ciência e a Tecnologia (CEECIND/02037/2017; UIDB/00295/2020 and UIDP/00295/2020). TD acknowledges funding from National Research Foundation (NRF_ZA) (Grant Number: 117700). FE appreciates funding by the Austrian Science Foundation (FWF project no I 4011-B32). AMK was supported by the NSF Macrosystems Biology program under grant 1834548. DR thanks InEE-CNRS who supports the French national network Biological Invasions (Groupement de Recherche InvaBio, 2014–2022).

Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Cuthbert, R. N., Diagne, C., Hudgins, E. J., Turbelin, A., Ahmed, D. A., Albert, C., Bodey, T. W., Briski, E., Essl, F., Haubrock, P. J., Gozlan, R. E., Kirichenko, N., Kourantidou, M., Kramer, A. M., & Courchamp, F. Biological invasion costs reveal insufficient proactive management worldwide. Science of the Total Environment, 819, (2022): 153404, https://doi.org/10.1016/j.scitotenv.2022.153404.

Description: The global increase in biological invasions is placing growing pressure on the management of ecological and economic systems. However, the effectiveness of current management expenditure is difficult to assess due to a lack of standardised measurement across spatial, taxonomic and temporal scales. Furthermore, there is no quantification of the spending difference between pre-invasion (e.g. prevention) and post-invasion (e.g. control) stages, although preventative measures are considered to be the most cost-effective. Here, we use a comprehensive database of invasive alien species economic costs (InvaCost) to synthesise and model the global management costs of biological invasions, in order to provide a better understanding of the stage at which these expenditures occur. Since 1960, reported management expenditures have totalled at least US$95.3 billion (in 2017 values), considering only highly reliable and actually observed costs — 12-times less than damage costs from invasions ($1130.6 billion). Pre-invasion management spending ($2.8 billion) was over 25-times lower than post-invasion expenditure ($72.7 billion). Management costs were heavily geographically skewed towards North America (54%) and Oceania (30%). The largest shares of expenditures were directed towards invasive alien invertebrates in terrestrial environments. Spending on invasive alien species management has grown by two orders of magnitude since 1960, reaching an estimated $4.2 billion per year globally (in 2017 values) in the 2010s, but remains 1–2 orders of magnitude lower than damages. National management spending increased with incurred damage costs, with management actions delayed on average by 11 years globally following damage reporting. These management delays on the global level have caused an additional invasion cost of approximately $1.2 trillion, compared to scenarios with immediate management. Our results indicate insufficient management — particularly pre-invasion — and urge better investment to prevent future invasions and to control established alien species. Recommendations to improve reported management cost comprehensiveness, resolution and terminology are also made.

Description: The authors thank the French National Research Agency (ANR-14-CE02-0021) and the BNP-Paribas Foundation Climate Initiative for funding the InvaCost project and the work on InvaCost database development. The present work was conducted in the frame of InvaCost workshop carried in November 2019 (Paris, France) and funded by the AXA Research Fund Chair of Invasion Biology and is part of the AlienScenario project funded by BiodivERsA and Belmont-Forum call 2018 on biodiversity scenarios. RNC was funded through a Leverhulme Early Career Fellowship (ECF-2021-001) from the Leverhulme Trust and a Humboldt Postdoctoral Fellowship from the Alexander von Humboldt Foundation. DAA is funded by the Kuwait Foundation for the Advancement of Sciences (KFAS) (PR1914SM-01) and the Gulf University for Science and Technology (GUST) internal seed funds (187092 & 234597). CA was funded by the French National Centre for Scientific Research (CNRS). TWB acknowledges funding from the European Union's Horizon 2020 research and innovation programme Marie Skłodowska-Curie fellowship (Grant No. 747120). FE was funded through the 2017–2018 Belmont Forum and BiodivERsA joint call for research proposals, under the BiodivScen ERA-Net COFUND programme, and with the funding organisation Austrian Science Foundation FWF (grant I 4011-B32). NK is funded by the basic project of Sukachev Institute of Forest SB RAS, Russia (Project No. 0287-2021-0011; data mining) and the Russian Science Foundation (project No. 21-16-00050; data analysis).

Description: Highlights: • A High Resolution-LOPC and a FlowCAM were evaluated for ballast water monitoring. • Both instruments underestimated density compared to microscopy. • Size measurements can be affected by organism orientation and complex morphology. • Both tools might be particularly useful when working with a known community. Abstract: Many commercial ships will soon begin to use treatment systems to manage their ballast water and reduce the global transfer of harmful aquatic organisms and pathogens in accordance with upcoming International Maritime Organization regulations. As a result, rapid and accurate automated methods will be needed to monitoring compliance of ships' ballast water. We examined two automated particle counters for monitoring organisms ≥ 50 μm in minimum dimension: a High Resolution Laser Optical Plankton Counter (HR-LOPC), and a Flow Cytometer with digital imaging Microscope (FlowCAM), in comparison to traditional (manual) microscopy considering plankton concentration, size frequency distributions and particle size measurements. The automated tools tended to underestimate particle concentration compared to standard microscopy, but gave similar results in terms of relative abundance of individual taxa. For most taxa, particle size measurements generated by FlowCAM ABD (Area Based Diameter) were more similar to microscope measurements than were those by FlowCAM ESD (Equivalent Spherical Diameter), though there was a mismatch in size estimates for some organisms between the FlowCAM ABD and microscope due to orientation and complex morphology. When a single problematic taxon is very abundant, the resulting size frequency distribution curves can become skewed, as was observed with Asterionella in this study. In particular, special consideration is needed when utilizing automated tools to analyse samples containing colonial species. Re-analysis of the size frequency distributions with the removal of Asterionella from FlowCAM and microscope data resulted in more similar curves across methods with FlowCAM ABD having the best fit compared to the microscope, although microscope concentration estimates were still significantly higher than estimates from the other methods. The results of our study indicate that both automated tools can generate frequency distributions of particles that might be particularly useful if correction factors can be developed for known differences in well-studied aquatic ecosystems.

Description: The goal of this study was to test whether it is possible to produce early hatching cysts of Artemia franciscana from San Francisco Bay (SFB) by truncation selection. The starting material was an SFB cyst sample, harvested in nature. After selection of early hatching nauplii had taken place, these selected individuals were cultured to maturity, and the hatching rate of their offspring (F1) was compared with that of the parental generation and with the non-selected control F1. The possible differences in hatching rate were used to estimate heritability. Two different selection experiments were run, accompanied with a number of additional tests studying the influence of the hatching set-up, the hatching temperature and diapause termination using hydrogen peroxide, on the hatching rate. Also the influence of different culture salinities on hatching rate and on possible success of selection was studied. The results revealed an influence of all those abiotic factors on the hatching rate, but also a marked interference of the hatching percentage with the hatching rate. Choosing the individuals based on their own phenotypic values (hatching within a certain time span of hatching incubation) and using those to produce the next generation, revealed a positive response. The selection in different salinities showed a different response. Depending on the strength of the selection pressure, the samples were advanced in time, starting with the highest selection pressure, and ending with the control and the parental sample. In spite of the strong interference of environmental factors, our results suggest that selection of early hatching cysts is possible.

Description: The spread and impact of alien species among freshwater ecosystems has increased with global trade and human movement; therefore, quantifying the role of anthropogenic and ecological factors that increase the risk of invasion is an important conservation goal. Two factors considered as null models when assessing the potential for invasion are colonization pressure (i.e., the number of species introduced) and propagule pressure [i.e., the number (propagule size), and frequency (propagule number), of individuals of each species introduced]. We translate the terminology of species abundance distributions to the invasion terminology of propagule size and colonization size (PS and CS, respectively). We conduct hypothesis testing to determine the underlying statistical species abundance distribution for zooplankton assemblages transported between freshwater ecosystems; and, on the basis of a lognormal distribution, construct four hypothetical assemblages spanning assemblage structure, rank-abundance gradient (e.g., even vs uneven), total abundance (of all species combined), and relative contribution of PS vs CS. For a given CS, many combinations of PS and total abundance can occur when transported assemblages conform to a lognormal species abundance distribution; therefore, for a given transportation event, many combinations of CS and PS are possible with potentially different ecological outcomes. An assemblage exhibiting high PS but low CS (species poor, but highly abundant) may overcome demographic barriers to establishment, but with lower certainty of amenable environmental conditions in the recipient region; whereas, the opposite extreme, high CS and low PS (species rich, but low abundance per species) may provide multiple opportunities for one of n arriving species to circumvent environmental barriers, albeit with lower potential to overcome demographic constraints. Species abundance distributions and the corresponding influence of CS and PS are some of many influential factors (e.g., demographic and genetic stochasticity, environmental variability, composition of recipient ecosystems) that will help refine an understanding of establishment risk following the human-mediated movement of species.

Description: Highlights: • Feeding overlap was highly expressed between native and non-native oyster. • Differences were recorded in zooplankton but not in phytoplankton consumption. • O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. • O. edulis had broader isotopic niche than C. gigas. Abstract: In order to detect the possible regulatory effect of non-native C. gigas on the native O. edulis, under aquaculture conditions, feeding interactions between them were investigated in a highly productive environment of Lim Bay (Adriatic Sea). The present study uses a multi-methodological approach, including stomach content, DNA barcoding and stable isotope analysis to elucidate the feeding ecology of two oyster species. The research confirmed a high overlap throughout the year in the feeding traits among native and non-native oyster species. Competition for food was not the only relationship that exists between the investigated species as the presence of O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. Findings are not in favour of introducing C. gigas to commercial aquaculture in any new areas in the Adriatic Sea and support the need to improve the existing O. edulis aquaculture and conserve its wild stocks.

Description: The Pacific oyster Magallana gigas, globally one of the most translocated marine species, has never been commercially farmed in any part of the Croatian eastern Adriatic Sea, where the native flat oyster Ostrea edulis is the only cultured oyster species. The Pacific oyster has, however, established populations on the west coast of the Istria peninsula, in the northeast Adriatic Sea. Current distribution, abundance and size structure of the flat and Pacific oysters were studied there along spatial and depth gradients in natural and artificial habitats to assess their potential for coexistence. This is the first quantitative assessment of native and non-native oyster populations on a Mediterranean-wide scale providing a baseline for determining future changes in their distribution. Both species were omnipresent, with the Pacific oyster displaying a more pronounced variability in abundance and size in relation to survey regions and depths. The population density of flat oysters was low, generally less than 1 individual/m(2), with no difference among regions. The density of the Pacific oyster was significantly higher, being on average 5 individuals/m(2). Dense, reef-forming aggregations of Pacific oysters were contained in Lim Bay, a nationally-important shellfish aquaculture area, where its mean density was 107 individuals/m(2). Along the open coastline its densities were considerably lower and followed a latitudinal gradient. The observed abundance and size distribution patterns of the Pacific oyster suggest that Lim Bay was the introduction point, with feral settlement likely originating from short-lived experimental aquaculture trials and subsequently dispersing by prevailing local currents. The flat oysters were larger in size and settled at different depths compared to the Pacific oysters. The vertical range of Pacific oysters was mostly contained in the tidal zone, while flat oysters were present in the subtidal exclusively. Such spatial partitioning likely resulted from introduced oysters occupying a vacant ecological niche and not due to interspecific competitive exclusion. Habitat type had a strong effect on proliferation of Pacific oysters. Artificial hard substrata harboured more abundant and larger Pacific oysters than the natural rocky shore habitat. The possibility of multiple local introduction pathways in ports and marinas is also discussed. Currently, there seems to be no spatial competition between the two oyster species, but as it is hard to predict future possible impacts of non-native species, we strongly suggest regular monitoring of the Pacific oyster, prioritising sensitive and protected areas as well as areas at the edge of its distribution.

Description: Ballast water has been identified as a leading vector for introduction of non‐indigenous species. Recently, the International Maritime Organization implemented management standards—D‐2—where all large, commercial ships trading internationally are required to adopt an approved treatment system using technologies such as ultraviolet radiation or chlorination. However, current management regulations are based only on the total abundance of viable taxa transported (i.e. total propagule pressure), largely ignoring species richness (i.e. colonization pressure). To determine the efficacy of chlorine treatment in reducing invasion risks and changes in transported biological communities inside ballast tanks, we used DNA metabarcoding‐based approaches to estimate colonization pressure (here, the number of species/operational taxonomic units [OTUs] introduced) and relative propagule pressure (relative abundance of each species/OTU) of zooplankton communities in control and chlorine treated tanks during four transatlantic voyages. Our study demonstrated that transport itself did not significantly reduce colonization pressure of zooplankton species, nor did chlorine treatment. Chlorine treatment altered community structure by reducing relative propagule pressure of some taxa such as Mollusca and Rotifera, while increasing relative propagule pressure of some Oligohymenophorea and Copepoda species. Synthesis and applications. Chlorine treatment may not reduce invasion risks as much as previously thought. Reduction in total propagule pressure does not mean reduction in abundance of all species equally. While some taxa might experience drastically reduced abundance, others might not change at all or increase due to hatching from dormant stages initiated by chlorine exposure. Therefore, management strategies should consider changes in total propagule pressure and colonization pressure when forecasting risk of new invasions. We therefore recommend adopting new approaches, such as DNA metabarcoding‐based methods, to assess the whole biodiversity discharged from ballast water. As species responses to chlorine treatment are variable and affected by concentration, we also recommend a combination of different technologies to reduce introduction risks of aquatic organisms.

Description: Coastal ecosystems globally are exposed to the most pervasive anthropogenic activities, caused by a suite of human infrastructure and enterprises such as shipping ports, aquaculture facilities, fishing, and tourism. These anthropogenic activities may lead to changes in ecosystem biodiversity, followed by loss of ecosystem functioning and services. Shipping industry and aquaculture have also been recognized as the main vectors for introduction of marine non-indigenous species (NIS) worldwide. In this study, we used DNA metabarcoding-based methods to investigate plankton biodiversity under varying anthropogenic pressures (shipping and bivalve aquaculture) along the eastern Adriatic coast (the northernmost part of the Mediterranean Sea). Our comparative assessment revealed similar community structures among investigated coastal locations (Northern, Central and Southern Adriatic). When the whole plankton communities were considered, they did not differ significantly between port and aquaculture sites. However, the proportion of the unique zOTUs in the port samples was remarkably higher than that in aquaculture sites (40.5% vs 8.2%), indicating that port areas may receive higher abundance and species richness of NIS than aquaculture sites. Further important difference between the two types of anthropogenically impacted habitats was a high abundance of three notorious invaders – M. leidyi, M. gigas, and H. elegans in late summer at the aquaculture site in Northern Adriatic. Therefore, the plankton community of the area is under pressure not only from aquaculture activities, but also establishment of NIS. Port areas are probably under greater introduction pressure from NIS, but aquaculture sites may experience greater community changes due to their establishment

Description: Highlights: • Aquatic invasions have cost the global economy US$345 billion. • Most costs are caused by invertebrates, in North America and damages to resources. • Costs have increased exponentially over time, to at least US$23 billion in 2020. • Aquatic invasion costs are underrepresented compared to terrestrial invasion costs. • Taxonomic, geographic and temporal gaps make these costs severely underestimated. Abstract: Much research effort has been invested in understanding ecological impacts of invasive alien species (IAS) across ecosystems and taxonomic groups, but empirical studies about economic effects lack synthesis. Using a comprehensive global database, we determine patterns and trends in economic costs of aquatic IAS by examining: (i) the distribution of these costs across taxa, geographic regions and cost types; (ii) the temporal dynamics of global costs; and (iii) knowledge gaps, especially compared to terrestrial IAS. Based on the costs recorded from the existing literature, the global cost of aquatic IAS conservatively summed to US$345 billion, with the majority attributed to invertebrates (62%), followed by vertebrates (28%), then plants (6%). The largest costs were reported in North America (48%) and Asia (13%), and were principally a result of resource damages (74%); only 6% of recorded costs were from management. The magnitude and number of reported costs were highest in the United States of America and for semi-aquatic taxa. Many countries and known aquatic alien species had no reported costs, especially in Africa and Asia. Accordingly, a network analysis revealed limited connectivity among countries, indicating disparate cost reporting. Aquatic IAS costs have increased in recent decades by several orders of magnitude, reaching at least US$23 billion in 2020. Costs are likely considerably underrepresented compared to terrestrial IAS; only 5% of reported costs were from aquatic species, despite 26% of known invaders being aquatic. Additionally, only 1% of aquatic invasion costs were from marine species. Costs of aquatic IAS are thus substantial, but likely underreported. Costs have increased over time and are expected to continue rising with future invasions. We urge increased and improved cost reporting by managers, practitioners and researchers to reduce knowledge gaps. Few costs are proactive investments; increased management spending is urgently needed to prevent and limit current and future aquatic IAS damages.