Impacts of the invasive alga Sargassum muticum on ecosystem functioning and food web structure

Chemical Survey and Antifungal Efficacy of Sargassum muticum's Alkaloids and Phenolic-Rich Fraction Against Airborne Toxigenic and Nosocomial Opportunistic Molds Isolates

The Atlantic coastline of El-Jadida, Morocco, is renowned for its plentiful algae, especially brown seaweed, which is rich in active compounds known for their antifungal properties. This valuable resource offers an exciting opportunity to tackle the numerous challenges posed by invasive fungal infections, allergies, mycotoxin-related food poisoning, and drug-resistant strains. Underscoring the urgent need to explore alternative, sustainable, and environmentally friendly antifungal agents derived from algae. This study aimed to evaluate the antifungal activity of total alkaloids and phenolic-rich fractions derived from seven species of Pheophyceae: Sargassum muticum, Sargassum vulgare, Bifurcaria bifurcata, Cystoseira tamariscifolia, Cystoseira humilis, Laminaria ochroleuca, and Fucus spiralis against four fungi: airborne toxigenic isolates of Aspergillus westerdijkiae and Chaetomium globosum as well as nosocomial opportunistic isolates of Aspergillus nidulans and Scopulariopsis brevicaulis. The study also aimed to identify the most effective alga and its specific active compounds through LC-MS and GC-MS analysis. The invasive Sargassum muticum was chosen as the most potent alga in inhibiting the growth of mycelium. For the first time, the alkaloids palmatine and jatrorrhizine, along with caulerpin, have been identified. The chloroform fraction revealed the prevalence of phenolic compounds including, phenolic acids, flavonoids, and phlorotannins. The lowest minimum inhibitory concentrations (MICs), with a maximum fungal load of 108 colony-forming unit (CFU), recorded ranged from 3.12 to 6.25 μg/mL by the phenolic-rich fraction against airborne toxigenic isolates, and from 100 to 200 μg/mL against nosocomial opportunistic isolates by the total alkaloids. In comparison, the positive control, ketoconazole, showed higher MICs and resistance against A. nidulans. The valorization of Sargassum muticum is proposed as a green strategy to preserve the ecological balance, combat antifungal resistance, and address public health challenges.

Loss, resilience and recovery of kelp forests in a region of rapid ocean warming

BACKGROUND AND AIMS

Changes in kelp abundances on regional scales have been highly variable over the past half-century owing to strong effects of local and regional drivers. Here, we assess patterns and dominant environmental variables causing spatial and interspecific variability in kelp persistence and resilience to change in Nova Scotia over the past 40 years.

METHODS

We conducted a survey of macrophyte abundance at 251 sites spanning the Atlantic coast of Nova Scotia from 2019 to 2022. We use this dataset to describe spatial variability in kelp species abundances, compare species occurrences to surveys conducted in 1982 and assess changes in kelp abundance over the past 22 years. We then relate spatial and temporal patterns in abundance and resilience to environmental metrics.

KEY RESULTS

Our results show losses of sea urchins and the cold-tolerant kelp species Alaria esculenta, Saccorhiza dermatodea and Agarum clathratum in Nova Scotia since 1982 in favour of the more warm-tolerant kelps Saccharina latissima and Laminaria digitata. Kelp abundances have increased slightly since 2000, and Saccharina latissima and L. digitata are widely abundant in the region today. The highest kelp cover occurs on wave-exposed shores and at sites where temperatures have remained below thresholds for growth (21 °C) and mortality (23 °C). Moreover, kelp has recovered from turf dominance following losses at some sites during a warm period from 2010 to 2012.

CONCLUSIONS

Our results indicate that dramatic changes in kelp community composition and a loss of sea urchin herbivory as a dominant driver of change in the system have occurred in Nova Scotia over the past 40 years. However, a broad-scale shift to turf-dominance has not occurred, as predicted, and our results suggest that resilience and persistence are still a feature of kelp forests in the region despite rapid warming over the past several decades.

Impacts of seasonal temperatures, ocean warming and marine heatwaves on the nutritional quality of eastern school prawns (Metapenaeus macleayi)

Ocean warming and marine heatwaves significantly alter environmental conditions in marine and estuarine environments. Despite their potential global importance for nutrient security and human health, it is not well understood how thermal impacts could alter the nutritional quality of harvested marine resources. We tested whether short-term experimental exposure to seasonal temperatures, projected ocean-warming temperatures, and marine heatwaves affected the nutritional quality of the eastern school prawn (Metapenaeus macleayi). In addition, we tested whether nutritional quality was affected by the duration of exposure to warm temperatures. We show the nutritional quality of M. macleayi is likely to be resilient to short- (28 d), but not longer-term (56 d) exposure to warming temperatures. The proximate, fatty acid and metabolite compositions of M. macleayi were unchanged after 28 d exposure to simulated ocean warming and marine heatwaves. The ocean-warming scenario did, however, show potential for elevated sulphur, iron and silver levels after 28 d. Decreasing saturation of fatty acids in M. macleayi after 28 d exposure to cooler temperatures indicates homeoviscous adaptation to seasonal changes. We found that 11 % of measured response variables were significantly different between 28 and 56 d when exposed to the same treatment, indicating the duration of exposure time and time of sampling are critical when measuring this species' nutritional response. Further, we found that future acute warming events could reduce harvestable biomass, despite survivors retaining their nutritional quality. Developing a combined knowledge of the variability in seafood nutrient content with shifts in the availability of harvested seafood is crucial for understanding seafood-derived nutrient security in a changing climate.

Implications of taxonomic misidentification for future invasion predictions: Evidence from one of the most harmful invasive marine algae

Invasive species have been a focus of concern in recent decades, becoming more problematic due to the cumulative impacts of climate change. Understanding the interactions among stress factors is essential to anticipate ecosystems' responses. Hereby, robust modeling frameworks must be able to identify the environmental drivers of invasion and forecast the current and future of their potential distribution. These studies are essential for the management of invasions and to be prepared for the future we are facing. Here we demonstrate that taxonomic misidentifications may lead to absolutely erroneous predictions, by using as an example one of the worst invasive species in the Mediterranean Sea (Lophocladia lallemandii), which has been misidentified for three decades and now is correctly identified. Consequently, and bearing in mind overall trends in species misidentification due to the loss of taxonomic expertise and the presence of cryptic species, among others, attempts to understand and predict species involved in invasion processes must always first consider taxonomic studies.

Long-term changes in benthic communities following the invasion by an alien octocoral in the Southwest Atlantic, Brazil

Invasive alien species are considered one of the main threats to marine biodiversity. We used a BACI design to investigate the changes in rocky reef benthic communities related to the invasion of the octocoral Latissimia ningalooensis in the Southwest Atlantic. Drastic changes in benthic community structure were restricted to the invaded site and associated with the growth of L. ningalooensis on turf algae. Conversely, the zoanthid Palythoa caribaeorum remained stable coverage along the 9-year study period, indicating a greater biotic resistance against the octocoral. Latissimia ningalooensis spread from large and well-established patches to new areas of the reef, increasing turf-octocoral interactions. This study warns of the great invasive potential of the octocoral, due to its high abundance, competitive and expansion ability. The decline in abundance of turf-forming algae following the emergence of L. ningalooensis threatens the structure and functioning of macroalgal-dominated rocky reefs.

Herbivory and functional traits suggest that enemy release is not an important mechanism driving invasion success of brown seaweeds

Invasive species are a global threat to biodiversity and there is a pressing need to better understand why some species become invasive outside of their native range, and others do not. One explanation for invasive species success is their release from concurrent natural enemies upon introduction to the non-native range. The so-called enemy release hypothesis (ERH) has conflicting support, depending upon the ecosystem and species investigated. To date, most studies testing the generality of the ERH have focused on terrestrial ecosystems. Here, we tested whether enemy release might contribute to the success of the invasive non-native brown seaweeds Undaria pinnatifida and Sargassum muticum in the United Kingdom. We conducted choice and no choice experiments to determine herbivore preference on these invaders relative to six functionally-similar native species. We also measured and compared species traits associated with defence against herbivory (carbon to nitrogen ratio, polyphenolic concentration, tensile strength, and compensatory growth). There were no differences in the biomass consumed between invasive and native species for either choice or no choice tests. The carbon to nitrogen ratio (a measure of nutritional quality) was significantly lower for S. muticum compared to the three native fucoid species, but measures of the other three defence traits were similar or even greater for invasive species compared with native species. Taken together, it is unlikely that the ERH applies to invasive seaweeds in the northeast Atlantic, suggesting that other factors may contribute to the success of invasive species in this system.

Submerged aquatic vegetation: Overview of monitoring techniques used for the identification and determination of spatial distribution in European coastal waters

Coastal waters are highly productive and diverse ecosystems, often dominated by marine submerged aquatic vegetation (SAV) and strongly affected by a range of human pressures. Due to their important ecosystem functions, for decades, both researchers and managers have investigated changes in SAV abundance and growth dynamics to understand linkages to human perturbations. In European coastal waters, monitoring of marine SAV communities traditionally combines diver observations and/or video recordings to determine, for example, spatial coverage and species composition. While these techniques provide very useful data, they are rather time consuming, labor-intensive, and limited in their spatial coverage. In this study, we compare traditional and emerging remote sensing technologies used to monitor marine SAV, which include satellite and occupied aircraft operations, aerial drones, and acoustics. We introduce these techniques and identify their main strengths and limitations. Finally, we provide recommendations for researchers and managers to choose the appropriate techniques for future surveys and monitoring programs. Integr Environ Assess Manag 2022;18:892-908. © 2021 SETAC.

Dramatic changes in the structure of shallow-water marine benthic communities following the invasion by Rugulopteryx okamurae (Dictyotales, Ochrophyta) in Azores (NE Atlantic)

Biological invasions are considered one of the most important drivers of biodiversity loss. Here we use a before-after-control-impact (BACI) design to investigate the impact of Rugulopteryx okamurae on the structure of shallow-water marine benthic communities in São Miguel island, Azores. After its first appearance in 2019, R. okamurae has rapidly invaded much of the southern coast of the island, where it became the dominant algae. This was followed by significant changes in the structure of shallow-water marine benthic communities, with substantial losses of natural variability and species richness. Compared to before, there has been dramatic reductions in the abundances of articulated coralline algae, corticated algae and corticated foliose algae in invaded locations. These results highlight its highly invasive character, not seen with other, more well-known, invasive species. It remains to be investigated if its impacts persist throughout time and to quantify the functional consequences of such dramatic changes.

The Fucales Index: A new tool for monitoring subtidal rocky habitats, and its application to an Atlantic bay subjected to nuclear power plant's effluents

Ecological indices are useful tools for environmental managers to monitor and detect changes caused by natural or anthropogenic disturbances. Despite the fact that descriptors of Fucales species are often included in indices for evaluating changes in coastal marine habitats, there is no index based solely on Fucales abundance. This study proposes the Fucales Index (FI), based on four classes of abundance of a selected Fucales species. The ability of FI to detect changes in the abundance of Sargassum sp. was tested in a Brazilian bay that is subjected to the effluent plume from a nuclear power plant. FI was significantly different when comparing areas inside and outside of the plume area, and it increased with increasing distance from the source of the disturbance. These findings suggest that FI is a suitable tool for assessing the effect of an effluent plume and potentially of other disturbances on rocky shores hosting Fucales.

Physiological Responses of Sargassum muticum, a Potential Golden Tide Species, to Different Levels of Light and Nitrogen

Sargassum golden tides have bloomed frequently in many sea areas throughout the world, and negatively impacted on the local marine ecology. Sargassum muticum commonly inhabits rocky shores. It is now distributed worldwide due to its invasiveness, and recently drifting individuals have been observed on the coasts of Canary Islands. However, as a potential golden tide alga, physiological, and ecological studies of this species have not been frequently explored. To investigate the responses of S. muticum to light and nitrogen, two key environmental factors in golden tide formation, we established three light levels (LL, low light, 10 μmol photons m–2 s–1; ML, medium light, 60 μmol photons m–2 s–1, and HL, high light, 300 μmol photons m–2 s–1) and two nitrogen levels (LN, low nitrogen, 25.0 μM of natural seawater; HN, high nitrogen, 125.0 μM), and cultivated the thalli under different conditions for 12 days before measuring the physiological properties of alga. The results showed that higher light and/or nitrogen levels enhanced the relative algal growth rate. The maximum net photosynthesis rate of alga increased with the light, while it remained unaffected by the nitrogen. The HN treatment had no effect on the apparent photosynthetic efficiency of algae in the LL culture, while increased it in the ML and HL cultures. The irradiance saturation point of photosynthesis was approximately 300 μmol photons m–2 s–1 with no significant difference among the six treatments, except for a slight increase under HLHN in contrast to the LLHN and MLLN treatments. HL treatment decreased the maximum quantum yield of photosynthesis (Fv/Fm) in both nitrogen levels. In the HN culture, ML and HL led to lower values of photoinhibition, indicating higher survivability in the alga. The HN culture led to higher nitrogen uptake but had no effects on Fv/Fm and the contents of pigments and soluble protein, regardless of culture light level. Based on these results, we speculate that drifting individuals of S. muticum would be possible to form a golden tide owing to its rapid growth rate at light level of 300 μmol photons m–2 s–1, when they encountered the sustained lower light level on the sea surface (≤300 μmol photons m–2 s–1). A high nitrogen supply caused by eutrophication of seawater might facilitate this process. Our results provide an important reference for the prediction of golden tides formed by S. muticum.

Vulnerability of Temperate Mesophotic Ecosystems (TMEs) to environmental impacts: Rapid ecosystem changes at Lough Hyne Marine Nature Reserve, Ireland

Temperate Mesophotic Ecosystems (TMEs) are stable habitats, usually dominated by slow-growing, long-lived sessile invertebrates and sciaphilous algae. Organisms inhabiting TMEs can form complex three-dimensional structures and support many commercially important species. However, TMEs have been poorly studied, with little known about their vulnerability to environmental impacts. Lough Hyne Marine Nature Reserve (Ireland) supports TMEs in shallower waters (12-40 m) compared with other locations (30-150+ m) as a result of the unusual hydrodynamic conditions. Here, we report changes that have occurred on the sponge-dominated cliffs at Lough Hyne between 1990 and 2019, providing insights into TME long-term stability and vulnerability to environmental impacts. Our main finding was a marked decline in most three-dimensional sponges at the internal sites of the lough. This was likely the result of one or more mass mortality events that occurred between 2010 and 2015. We also found an increase in ascidians, which might have been more tolerant and benefited from the space freed by the sponge mortality. Finally, in the most recent surveys, we found a high abundance of sponge recruits, indicating that a natural recovery may be underway. The possible factors involved in these community changes include eutrophication, increased temperature, and a toxic event due to an anomaly in the oxycline breakdown. However, the absence of comprehensive monitoring of biotic and abiotic variables makes it impossible to identify the cause with certainty. Our Lough Hyne example shows the potential vulnerability of TMEs to short-term disturbance events, highlighting the importance of monitoring these habitats globally to ensure they are appropriately conserved.

Thermal Tolerance May Slow, But Not Prevent, the Spread of Sargassum horneri (Phaeophyceae) along the California, USA and Baja California, MEX Coastline

Biological invasions have become increasingly prevalent in marine ecosystems, modifying biodiversity and altering the way ecosystems function. Understanding how variation in environmental factors influences the success of non-native species, especially their early life stages, can be a crucial step in identifying habitats that are under threat of invasion, and in predicting how rapidly and far these species may spread once they arrive in novel habitats. The invasive marine macroalga Sargassum horneri was first observed in Long Beach Harbor, CA, USA in 2003, and has since spread throughout the Southern California Bight and along the Baja California Peninsula, MEX where it now forms dense stands on subtidal rocky reefs and displaces native habitat-forming macroalgae. We examined how variation in temperature, nutrients, and irradiance affect survival, growth, and development in S. horneri early life stages over a three-week period. Our experimental treatments consisted of orthogonally crossed temperatures (10, 15, 20, and 25°C), nutrient concentrations (ambient and nutrient-enriched seawater), and irradiances (50 and 500 µmol photons · m-2 · s-1 ). Overall, temperature exerted the greatest influence on S. horneri's germling and juvenile life stages, with moderate temperatures facilitating their greatest survival, growth, and development. In contrast, fewer germlings developed fully under the lowest or highest temperatures, and juvenile survival and growth were reduced, especially when combined with low irradiances. Together, our data suggest that ocean temperatures of or below 10˚C and of or above 25°C may slow, but likely not stop, S. horneri's northward and southward expansion along the California and Baja California coasts.

Seaweeds as Valuable Sources of Essential Fatty Acids for Human Nutrition

The overexploitation of terrestrial habitats, combined with the ever-growing demand for food, has led to the search for alternative food sources. The importance of seaweeds as food sources has been growing, and their potential as sources of fatty acids (FA) make seaweeds an interesting feedstock for the food and nutraceutical industries. The aim of this study is to assess the potential of five red seaweeds (Asparagospis armata, Calliblepharis jubata, Chondracanthus teedei var. lusitanicus, Gracilaria gracilis, and Grateloupia turuturu) and three brown seaweeds (Colpomenia peregrina, Sargassum muticum and Undaria pinnatifida), harvested in central Portugal, as effective sources of essential FA for food or as dietary supplements. FA were extracted from the biomass, transmethylated to methyl esters, and analyzed through gas chromatography-mass spectrometry. G. gracilis presented the highest content of saturated fatty acids (SFA) (41.49 mg·g-1), whereas C. jubata exhibited the highest content of highly unsaturated fatty acids (HUFA) (28.56 mg·g-1); the three G. turuturu life cycle stages presented prominent SFA and HUFA contents. Omega-6/omega-3 ratios were assessed and, in combination with PUFA+HUFA/SFA ratios, it is suggested that C. jubata and U. pinnatifida may be the algae with highest nutraceutical potential, promoting health benefits and contributing to a balanced dietary intake of fatty acids.

Spotting intruders: Species distribution models for managing invasive intertidal macroalgae

Invasive macroalgae represent one of the major threats to marine biodiversity, ecosystem functioning and structure, as well as being important drivers of ecosystem services depletion. Many such species have become well established along the west coast of the Iberian Peninsula. However, the lack of information about the distribution of the invaders and the factors determining their occurrence make bioinvasions a difficult issue to manage. Such information is key to enabling the design and implementation of effective management plans. The present study aimed to map the current probability of presence of six invasive macroalgae: Grateloupia turuturu, Asparagopsis armata, Colpomenia peregrina, Sargassum muticum, Undaria pinnatifida, and Codium fragile ssp. fragile. For this purpose, an extensive field survey was carried out along the coast of the north-western Iberian Peninsula. Species distribution models (SDMs) were then used to map the presence probability of these invasive species throughout the study region on the basis of environmental and anthropogenic predictor variables. The southern Galician rias were identified as the main hotspots of macroalgal invasion, with a high probability of occurrence for most of the species considered. Conversely, the probability of presence on the Portuguese coast was generally low. Physico-chemical variables were the most important factors for predicting the distribution of invasive macroalgae contributing between 57.27 and 85.24% to the ensemble models. However, anthropogenic factors (including size of vessels, number of shipping lines, distance from ports, population density, etc.) considerably improved the estimates of the probability of occurrence for most of the target species. This study is one of the few to include anthropogenic factors in SDMs for invasive macroalgae. The findings suggest that management actions aimed at controlling these species should strengthen control and surveillance at ports, particularly in southern Galician rias. Early detection should be of main concern for risk assessment plans on the Portuguese coast.

Summer and Winter Marine Heatwaves Favor an Invasive Over Native Seaweeds

Marine heatwaves (MHWs) are emerging as forceful agents of ecosystem change and are increasing in frequency, duration, and intensity with climate change. During MHWs, physiological thresholds of native species may be exceeded while the performance of invasive species with warm affinities may be enhanced. As a consequence, MHWs could significantly alter an ecosystem's invasive dynamics, but such interactions are poorly understood. Following a 10-d acclimation period, we investigated the physiological resistance and resilience of an intertidal rock pool assemblage invaded by the seaweed Sargassum muticum to realistic 14-d marine heatwave scenarios (+1.5°C, +2.0°C, +3.5°C) followed by a 14-d recovery period. We conducted mesocosm experiments in both summer and winter to investigate temporal variability of MHWs. MHW treatments had clear negative impacts on native seaweeds (Fucus serratus and Chondrus crispus) while enhancing the performance of S. muticum. This pattern was consistent across season indicating that acclimation to cooler ambient temperatures results in winter MHWs having significant impacts on native species. As climate warming advances, this may ultimately lead to changes in competitive interactions and potentially exclusion of native species, while invasive species may proliferate and become more conspicuous within temperate rocky shore environments.

Low Diversity of Intertidal Canopy-Forming Macroalgae at Urbanized Areas along the North Portuguese Coast

Canopy-forming macroalgae are the main component in some of the most diverse and productive coastal habitats around the world. However, canopy-forming macroalgae are very sensitive to anthropogenic disturbances. In coastal urban areas, intertidal organisms are exposed to the interactive effect of several anthropogenic disturbances that can modify the community’s structure and diversity. Along the North-East Atlantic shores, many studies explored the effect of anthropogenic disturbances on canopy-forming macroalgae, but mainly focused on kelps and fucoids. However, along the intertidal rocky shores of the Atlantic coast of the Iberian Peninsula, the most abundant and frequent canopy-forming macroalgae belong to the family Sargassaceae. To explore the effect of urbanization on these intertidal canopy-forming species the diversity and assemblage structure of canopy species were compared between four urban and four non-urban shores in the north of Portugal. Intertidal canopy assemblages on urban shores were dominated by the non-indigenous Sargassum muticum that was the only canopy-forming species on three of the four studied urban shores. Canopy assemblages on all non-urban shores were more diverse. Moreover, stands of canopy-forming species on urban shores were always monospecific, while at non-urban shores multi-specific stands were common. Therefore, results suggest that urbanization reduces canopy´s biodiversity.

Vitamin K as a Diet Supplement with Impact in Human Health: Current Evidence in Age-Related Diseases

Vitamin K health benefits have been recently widely shown to extend beyond blood homeostasis and implicated in chronic low-grade inflammatory diseases such as cardiovascular disease, osteoarthritis, dementia, cognitive impairment, mobility disability, and frailty. Novel and more efficient nutritional and therapeutic options are urgently needed to lower the burden and the associated health care costs of these age-related diseases. Naturally occurring vitamin K comprise the phylloquinone (vitamin K1), and a series of menaquinones broadly designated as vitamin K2 that differ in source, absorption rates, tissue distribution, bioavailability, and target activity. Although vitamin K1 and K2 sources are mainly dietary, consumer preference for diet supplements is growing, especially when derived from marine resources. The aim of this review is to update the reader regarding the specific contribution and effect of each K1 and K2 vitamers in human health, identify potential methods for its sustainable and cost-efficient production, and novel natural sources of vitamin K and formulations to improve absorption and bioavailability. This new information will contribute to foster the use of vitamin K as a health-promoting supplement, which meets the increasing consumer demand. Simultaneously, relevant information on the clinical context and direct health consequences of vitamin K deficiency focusing in aging and age-related diseases will be discussed.

Removal of an established invader can change gross primary production of native macroalgae and alter carbon flow in intertidal rock pools

The impact of invasive species on recipient communities can vary with environmental context and across levels of biological complexity. We investigated how an established invasive seaweed species affected the biomass, eco-physiology, carbon and nitrogen storage capacity of native seaweeds at sites with a different environmental setting due to a persistent upwelling in northern Spain. We removed the invasive Japanese wireweed Sargassum muticum from intertidal rock pools once every month during a one-year period and used an in-situ stable isotope pulse-chase labeling to estimate gross primary production (GPP), nitrogen uptake rate, 13C-carbon and 15N-nitrogen storage capacities. Following the addition of 13C-enriched bicarbonate and 15N-enriched nitrate to the seawater in the rock pools during the period of the low tide, we sampled macroalgal thalli at incoming tide to determine label uptake rate. After four days, we sampled macroalgal assemblages to determine both label storage capacity and biomass. After one year of removal there was no change in the macroalgal assemblage. However, both the GPP and 13C-carbon storage capacity were higher in the turf-forming Corallina spp. and, sometimes, in the canopy-forming Bifurcaria bifurcata. Nitrogen uptake rate followed similar, but more variable results. Although S. muticum inhibited carbon storage capacity of native species, the assemblage-level 13C-carbon storage was similar in the S. muticum-removed and control rock pools because the presence of the invasive species compensated for the functional loss of native species, particularly at sites where it was most abundant. No obvious effects were observed in relation to the environmental setting. Overall, the effect of the invasive S. muticum on carbon flow appeared to be mediated both by the effects on resource-use efficiency of native species and by its own biomass. Integrating physiological and assemblage-level responses can provide a broad understanding of how invasive species affect recipient communities and ecosystem functioning.

Climate change opens new frontiers for marine species in the Arctic: Current trends and future invasion risks

Climate change and increased anthropogenic activities are expected to elevate the potential of introducing nonindigenous species (NIS) into the Arctic. Yet, the knowledge base needed to identify gaps and priorities for NIS research and management is limited. Here, we reviewed primary introduction events to each ecoregion of the marine Arctic realm to identify temporal and spatial patterns, likely source regions of NIS, and the putative introduction pathways. We included 54 introduction events representing 34 unique NIS. The rate of NIS discovery ranged from zero to four species per year between 1960 and 2015. The Iceland Shelf had the greatest number of introduction events (n = 14), followed by the Barents Sea (n = 11), and the Norwegian Sea (n = 11). Sixteen of the 54 introduction records had no known origins. The majority of those with known source regions were attributed to the Northeast Atlantic and the Northwest Pacific, 19 and 14 records, respectively. Some introduction events were attributed to multiple possible pathways. For these introductions, vessels transferred the greatest number of aquatic NIS (39%) to the Arctic, followed by natural spread (30%) and aquaculture activities (25%). Similar trends were found for introductions attributed to a single pathway. The phyla Arthropoda and Ochrophyta had the highest number of recorded introduction events, with 19 and 12 records, respectively. Recommendations including vector management, horizon scanning, early detection, rapid response, and a pan-Arctic biodiversity inventory are considered in this paper. Our study provides a comprehensive record of primary introductions of NIS for marine environments in the circumpolar Arctic and identifies knowledge gaps and opportunities for NIS research and management. Ecosystems worldwide will face dramatic changes in the coming decades due to global change. Our findings contribute to the knowledge base needed to address two aspects of global change-invasive species and climate change.

Integrating comparative functional response experiments into global change research

There is a growing appreciation for the importance of non-consumptive effects in predator-prey interaction research, which can often outweigh the importance of direct feeding. Barrios-O'Neill et al. (2014) report a novel method to characterize such effects by comparing the functional response of native and introduced intermediate consumers in the presence and absence of a higher predator. The invader exhibited stronger direct feeding and was also more resistant to intimidation by the higher predator. This experimental framework may be incorporated into mainstream global change research, for example, to quantify the importance of non-consumptive effects for the success or failure of biological invasions.