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The e-newsletter Marine Science Review compiles citations and abstracts of significant marine-related research, selected from more than 710 science journals. Each of its 12 subject areas, which include the range of important issues involving the intersection of human activity with coastal and marine environments, is distributed monthly. You can subscribe to each subject area individually or to all.

Introduced Species

• Reviews
• Invasion Science
• Invasiveness
• Occurrence and Establishment
• Vectors and Pathways
• Environmental Disturbance and Invasions
• Impacts
• Prevention and Control
• Eradication

Reviews

• Pyšek, P. and Richardson, D.M.  Invasive species, environmental change and management, and health.  Annual Review of Environment and Resources 35: 25-55, 2010.
  Read Abstract >>

  Invasive species are a major element of global change and are contributing to biodiversity loss, ecosystem degradation, and impairment of ecosystem services worldwide. Research is shedding new light on the ecological and economic consequences of invasions. New approaches are emerging for describing and evaluating impacts of invasive species, and for translating these impacts into monetary terms. The harmful effects of invasions are now widely recognized, and multiscale programs are in place in many parts of the world to reduce current and future impacts. There has been an upsurge in scientific research aimed at guiding management interventions. Among the activities that are receiving the most attention and that have the most promise for reducing problems are risk assessment, pathway and vector management, early detection, rapid response, and new approaches to mitigation and restoration. Screening protocols to reduce new introductions are becoming more accurate and have been shown cost-effective.

Invasion Science

• Haydar, D. and Wolff, W.J.  Predicting invasion patterns in coastal ecosystems: relationship between vector strength and vector tempo.  Marine Ecology Progress Series 431: 1-10, 2011.
  Open Access >>  
  Read Abstract >>

  Oyster transports are among the leading anthropogenic vectors of coastwise introduction of non-indigenous species. Using the oyster industry of the Netherlands as a model system, we investigated the relationship between vector strength (number of invasions) and vector tempo (magnitude and frequency of transport) in analyzing and predicting invasion patterns. We reviewed literature on oyster-associated species introductions, analyzed the scale of commercial oyster imports, and collected and identified epiflora from Pacific oyster shells. A total of 35 protist, algal, and invertebrate species have been introduced to the Netherlands with oysters, and we found 41 species of macroalgae on transported oysters. However, the number of introductions and quantity of oysters imported are not necessarily positively correlated, particularly in the past 20 yr, when oyster imports decreased but the rate of introductions increased. The discrepancy between vector tempo and strength can be explained by unreported imports and vector characteristics: a single oyster may harbor a large number of species which are introduced with their substrate, thus facilitating establishment. Further, the recently developed extensive Pacific oyster reefs in Dutch waters provide a suitable substrate, enabling establishment even after low propagule pressure introduction events. Assumptions that are made about crucial parameters need to be reconsidered: reported propagule pressure is not the same as actual propagule pressure; per-episode diversity of potential inoculants is not at a fixed level without episodic unpredictable spikes, and the recipient environment is not static. With increasing interest in predicting invasion patterns, caution must be taken in assuming that reduced propagule pressure will lead to reduced invasions.

• Thomsen, M.S., Olden, J.D., Wernberg, T., Griffin, J.N., and Silliman, B.R.  A broad framework to organize and compare ecological invasion impacts.  Environmental Research 111(7): 899-908, 2011.  
  Read Abstract >>

  Invasive species have transformed local, regional and global biotas; however, few generalities about the mechanisms driving impacts of invaders have emerged. To explain variation in impacts among studies, we propose a broad framework that separates drivers of impacts into universal and unique attributes of the invasive species and the invaded habitat. Universal attributes are relevant to all invasions whereas unique attributes are distinct to a specific invasion. For example, impacts associated with the abundance of any invader or the properties of a specific invader (e.g., a rare toxin) represent a universal and unique impact attribute. Through meta-analyses of aquatic field experiments, we demonstrate the utility of our framework, documenting that both the abundance and the taxonomic identity of the invader significantly influence invasion outcomes for marine and freshwater plant and animal invaders. Our review also highlights that many more experiments are needed to test for universal attributes, such as priority effects, age and size, and how the attributes of the invaded habitat further modify invasion impacts. We hope that our framework will stimulate experimental invasion ecology and begin to reconcile the idiosyncrasies that currently impede the development of a unified framework for invasion impacts.

• Blackburn, T.M., Pysek, P., Bacher, S., Carlton, J.T., Duncan, R.P., Jarosík, V., Wilson, J.R.U., and Richardson, D.M.  A proposed unified framework for biological invasions.  Trends in Ecology and Evolution 26(7): 333-339, 2011.  
  Read Abstract >>

  There has been a dramatic growth in research on biological invasions over the past 20 years, but a mature understanding of the field has been hampered because invasion biologists concerned with different taxa and different environments have largely adopted different model frameworks for the invasion process, resulting in a confusing range of concepts, terms and definitions. In this review, we propose a unified framework for biological invasions that reconciles and integrates the key features of the most commonly used invasion frameworks into a single conceptual model that can be applied to all human-mediated invasions. The unified framework combines previous stage-based and barrier models, and provides a terminology and categorisation for populations at different points in the invasion process.

Invasiveness

• Lenz, M., da Gama, B.A.P., Gerner, N.V., Gobin, J., Gröner, F., Harry, Anil, Jenkins, S.R., Kraufvelin, P., Mummelthei, C., Sareyka, J., Xavier, E.A., and Wahl, M.  Non-native marine invertebrates are more tolerant towards environmental stress than taxonomically related native species: Results from a globally replicated study.  Environmental Research 111(7): 943-952, 2011. 
  Read Abstract >>

  To predict the risk associated with future introductions, ecologists seek to identify traits that determine the invasiveness of species. Among numerous designated characteristics, tolerance towards environmental stress is one of the most favored. However, there is little empirical support for the assumption that non-native species generally cope better with temporarily unfavorable conditions than native species. To test this concept, we ran five pairwise comparisons between native and non-native marine invertebrates at temperate, subtropical, and tropical sites. We included (natives named first) six bivalves: Brachidontes exustus and Perna viridis, P. perna and Isognomon bicolor, Saccostrea glomerata and Crassostrea gigas, two ascidians: Diplosoma listerianum and Didemnum vexillum as well as two crustaceans: Gammarus zaddachi and G. tigrinus. We simulated acute fluctuations in salinity, oxygen concentration, and temperature, while we measured respiration and survival rates. Under stressful conditions, non-native species consistently showed less pronounced deviations from their normal respiratory performance than their native counterparts. We suggest that this indicates that they have a wider tolerance range. Furthermore, they also revealed higher survival rates under stress. Thus, stress tolerance seems to be a property of successful invaders and could therefore be a useful criterion for screening profiles and risk assessment protocols.

• Lockwood, B.L. and Somero, G.N.  Invasive and native blue mussels (genus Mytilus) on the California coast: The role of physiology in a biological invasion.  Journal of Experimental Marine Biology and Ecology 400(1-2): 167-174, 2011. 
  Read Abstract >>

  The Mediterranean blue mussel, Mytilus galloprovincialis, is an invasive species that has displaced a congener, Mytilus trossulus, from its native range in central and southern California, USA. The dynamic relationship between interspecies competition and species-specific tolerances to abiotic factors, such as temperature and salinity, appears to have facilitated the success but has also imposed limits on the spread of this biological invasion. Here, we review the literature and present new data that document physiological differences between M. galloprovincialis and M. trossulus. In all comparisons, M. galloprovincialis is more warm-adapted than M. trossulus. Higher activities of enzymes involved in ATP generation show that the native M. trossulus is better adapted to colder conditions than M. galloprovincialis. Higher metabolic capacity (temperature compensation) in the native species may, however, lead to higher metabolic costs at sites where the two species co-occur. In addition, M. trossulus has a lower thermal tolerance of cardiac function and substrate binding by enzymes than M. galloprovincialis. The higher thermal tolerance of the invasive species is likely due in part to its enhanced ability to induce changes in the expression of particular genes and proteins in response to acute heat stress. Taken together, these data predict that M. galloprovincialis will continue to be the dominant blue mussel species along the warmer range of the California Current. Because the northern biogeographic limit of M. galloprovincialis is not stable, but rather shifts to lower or higher latitudes in concert with oceanographic variability, it is important to further characterize the physiological constraints of M. galloprovincialis, related to its sensitivity to cold temperatures and low salinities.

Occurrence and Establishment

• Mantelatto, M.C., Creed, J.C., Mourao, G.G., Migotto, A.E., and Lindner, A.  Range expansion of the invasive corals Tubastraea coccinea and Tubastraea tagusensis in the Southwest Atlantic.  Coral Reefs 30(2): 397, 2011. 
  
• Goldstien, S.J., Dupont, L., Viard, F., Hallas, P.J., Nishikawa, T., Schiel, D.R., Gemmell, N.J., and Bishop, J.D.D.  Global phylogeography of the widely introduced North West Pacific ascidian Styela clava.  PLoS ONE 6(2): art. e16755, 2011.
  Open Access >>  
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  The solitary ascidian Styela clava Herdman, 1882 is considered to be native to Japan, Korea, northern China and the Russian Federation in the NW Pacific, but it has spread globally over the last 80 years and is now established as an introduced species on the east and west coasts of North America, Europe, Australia and New Zealand. In eastern Canada it reaches sufficient density to be a serious pest to aquaculture concerns. We sequenced a fragment of the cytochrome oxidase subunit I mitochondrial gene (COI) from a total of 554 individuals to examine the genetic relationships of 20 S. clava populations sampled throughout the introduced and native ranges, in order to investigate invasive population characteristics. The data presented here show a moderate level of genetic diversity throughout the northern hemisphere. The southern hemisphere (particularly New Zealand) displays a greater amount of haplotype and nucleotide diversity in comparison. This species, like many other invasive species, shows a range of genetic diversities among introduced populations independent of the age of incursion. The successful establishment of this species appears to be associated with multiple incursions in many locations, while other locations appear to have experienced rapid expansion from a potentially small population with reduced genetic diversity. These contrasting patterns create difficulties when attempting to manage and mitigate a species that continues to spread among ports and marinas around the world.

• Occhipinti-Ambrogi, A. et al.  Alien species along the Italian coasts: an overview.  Biological Invasions 13(1): 215-237, 2011.
  Open Access >>  
  Read Abstract >>

  We present a contribution to the knowledge of marine and brackish water alien species (infraspecific taxa included) recorded along the Italian coasts. The Italian Peninsula, with over 7,000 km of coastline, is located in the center of the Mediterranean Sea, splitting the Western and the Eastern basins. Data were collected from published material, mostly authored by the experts of different marine taxa participating in the ''Allochthonous Species Group'' of the Italian Society of Marine Biology (SIBM). The data have been reviewed according to the taxonomic expertise of the authors and are organized in a referenced database containing information on each species about: distribution along Italian coasts, the native range, most probable vectors of introduction, population status and impact. The total number of marine alien species recorded along Italian coasts during the selected time period 1945-2009 is relatively high: 165 species, in many cases native from tropical regions of the world. Most of them were introduced in the 1980s and 1990s, whereas in the last few years the number of new records has decreased. The highest number of alien species has been observed in the northern Adriatic Sea, particularly in the Lagoon of Venice, which is the main hotspot of introduction. Of the total number of species, 46% was unable to establish resident populations in the Italian seas; 15% (24 species) rapidly increased their populations and extended their geographical range, consequently they may be considered invasive species.

• Albayrak, S.  Alien marine bivalve species reported from Turkish seas.  Cahiers de biologie marine 52(1): 107-118, 2011. 
  Read Abstract >>

  Literature review revealed a total of 31 valid alien bivalve species reported from the seas surrounding Turkey. In this study, these species were documented and their distributions in Turkish coasts were explained. Introducing pathways and rates of alien bivalves were discussed.

• Mead, A., Carlton, J.T., Griffiths, C.L., and Rius, M.  Revealing the scale of marine bioinvasions in developing regions: a South African re-assessment.  Biological Invasions 13(9): 1991-2008, 2011. 
  Read Abstract >>

  As recently as 2009 the number of introductions recorded for South Africa comprised 22 marine and estuarine species. This review aims to reassess the diversity and scale of introduced marine and estuarine species in the region. Accurate taxonomic and systematic work, broad review of historical records and new sampling surveys across selected marine habitats conducted by a team of local and international experts has effectively revealed the presence of previously misidentified, overlooked, or new introductions. A total of 86 introduced and 39 cryptogenic species are recognized, increasing known numbers four and twofold respectively within 1 year, although the current assessment is far from fully comprehensive. Additional species were revealed within the historic literature (76%), from surveys conducted post-2005 (11%) and following taxonomic resolution (13%). Temporal analyses confirmed discovery rates were increasing over time. Ship fouling and ballast water were the dominant vector pathways, accounting for 48 and 38% respectively. Spatial analyses revealed patterns of bioinvasion to be significantly higher on the west coast compared to the other coastal regions. Overall, 53% of introductions were concentrated within harbour areas with only 4 open-coast invaders detected at present. Introduced species found in the cool and warm-temperate provinces of the west and south coast mainly originated from the northern hemisphere (65%). In contrast, introductions located in the sub-tropical and tropical provinces of the east coast mainly originated from the southern hemisphere (18%), with the remaining 17% of introduced species being of unknown origin. The research approach described has proven pivotal, contributing massively toward revealing the true scale and patterns of bioinvasion for a developing region within a relatively short period of time.

• Mead, A., Carlton, J.T., Griffiths, C.L., and Rius, M.  Introduced and cryptogenic marine and estuarine species of South Africa.  Journal of Natural History 45(39-40): 2463-2524, 2011. 
  Read Abstract >>

  The introduction history, systematics, transport vectors and distribution patterns of 85 introduced and 39 cryptogenic marine or estuarine animals and plants of South Africa are presented. This represents an addition of 93 species compared with previous lists. Taxa covered include protists, dinoflagellates, sponges, cnidarians, annelids, crustaceans, pycnogonids, insects, molluscs, brachiopods, bryozoans, echinoderms, ascidians, fish, algae and higher plants. For each species a justification motivating its inclusion as an introduction into South African shores or its cryptogenic status, is provided. Challenges associated with this type of inventory work are explored and major patterns of bioinvasion within the region are summarized briefly.

• Knapp, I.S., Godwin, L.S., Smith, J.E., Williams, C.J., and Bell, J.J.  Records of non-indigenous marine species at Palmyra Atoll in the US Line Islands.  Marine Biodiversity Records 4: art. e30, 2011.  
  Read Abstract >>

  Globally, introductions of non-indigenous species have caused dramatic economic and ecological damage. Most research on marine invasions has occurred in locations easily accessible by researchers, but much less is known about introductions to remote islands. In the central Pacific, Palmyra Atoll represents one of the last remaining quasi-pristine reef systems left in the world. In the 1940s the Atoll underwent extensive military modifications, potentially making it susceptible to invasive species. Here we describe the presence of five non-indigenous invertebrate and algal introductions at Palmyra, including two sponges, Haliclona (Sigmadocia) caerulea and Gelliodes fibrosa; one bryozoan; Zoobotryon verticillatum; one hydroid, Pennaria disticha and one macroalga, Acanthophora spicifera. The Hawaiian Archipelago is the most likely source of the introductions via shipping or yachting activity to the Atoll. Currently, the impacts of these introductions remain unknown although future monitoring will assess the influence of these non-indigenous species on this remote reef system.

• Damgaard, C., Nygaard, B., Ejrnæs, R., and Kollmann, J.  State-space modeling indicates rapid invasion of an alien shrub in coastal dunes.  Journal of Coastal Research 27(3): 595-599, 2011.
  Open Access >>  
  Read Abstract >>

  Invasion by alien plants has negative effects on coastal dunes. Monitoring local spread of invasive species depends on long-term data with sufficient spatial resolution. Bayesian state-space models are a new method for monitoring invasive plants based on unbalanced permanent-plot data. The method allows separation of process and sampling variance, thus enabling ecological predictions with a known degree of uncertainty. The method is applied for the invasive shrub Rosa rugosa (Japanese rose) in Danish fixed dunes. The probability of observing R. rugosa increased significantly from 0.18 to 0.28 during the period 2004-2007. The species was found in all Danish coastal regions, albeit slightly less common in northern Denmark. We discuss the advantages and limitations of using Bayesian state-space models for monitoring and predicting plant invasions using presence-absence data.

• Elsner, N.O., Jacobsen, S., Thieltges, D.W., and Reise, K.  Alien parasitic copepods in mussels and oysters of the Wadden Sea.  Helgoland Marine Research 65(3): 299-307, 2011. 
  Read Abstract >>

  Molluscan intestinal parasites of the genus Mytilicola, specifically M. intestinalis, were initially introduced into bivalves in the North Sea in the 1930s. It was presumably introduced from the Mediterranean with ship-fouling mussels, then attained epidemic proportions in Mytilus edulis in the 1950s and is now widely established in the North Sea region. Mytilicola orientalis was co-introduced with Pacific oysters to France in the 1970s and in the southern North Sea in the early 1990s. Its main host Crassostrea gigas has massively invaded the Wadden Sea with a concomitant decline in mussels. To explore whether introduced mytilicolid parasites could play a role in the shifting dominance from native mussels to invasive oysters, we analysed 390 mussels and 174 oysters collected around the island of Sylt in the northern Wadden Sea. We show that M. intestinalis has a prevalence >90% and a mean intensity of 4 adult copepods in individual mussels with >50mm shell length at all sheltered sites. By contrast, none were found in the oysters. However, at one site, we found M. orientalis in C. gigas with a prevalence of 10% and an intensity of 2 per host individual (August 2008). This constitutes the most northern record in Europe for this Pacific parasite until now. Alignments of partial sequences of the mitochondrial cytochrome oxidase I (COI) gene and the nuclear internal transcribed spacers (ITS) and 18S rDNA sequences each show a distinct difference between the two species, which confirms our morphological identification. We suggest that the high parasite load in mussels compared to oysters may benefit the continued expansion of C. gigas in the Wadden Sea.

Vectors and Pathways

• Walters, L., Odom, R., and Zaleski, S.  The aquarium hobby industry and invasive species: has anything changed?  Frontiers in Ecology and the Environment 9(4): 206-207, 2011. 
• Zvyagintsev, A.Y. and Selifonova, J.P.  Hydrobiological studies of the ballast waters of cargo ships in Russian sea ports.  Oceanology 50(6): 924-932, 2010. 
  Read Abstract >>

  The results of the first studies on the ballast waters of commercial vessels in Novorossiysk and Vladivostok ports are presented. Data on the composition of the flora and fauna, their abundance, viability, and the origin of the species were obtained. In the zooplankton from the ballast waters sampled in the Novorossiysk port, 31 species of holoplankton and 15 species of meroplankton were found. The total number of zooplankton varied from 1.3 to 60 thousand ind./m³. The Mediterranean basin, providing 62% of the ballast waters, represents a vector of the greatest risk. In the port of Vladivostok, in the ballast waters of the vessels of the Russian-Japanese and Russian-Chinese lines, 45 species of microalgae, 24 species of zooplankton, 22 species of meroplankton, and 10 groups of meiofauna were revealed. In addition, 24 species of microscopic filamentous fungi were identified and 28 morphologically distinguishable strains of bacteria were isolated (in total not less than 153 species). The basic ''groups of risk'' for bioinvasions in the basins of the Black Sea and the seas of the Far East were revealed. The need for control of ships' ballast waters in Russia, which is presently lacking relevant national methodical guidelines and legislation, is substantiated.

• Ghabooli, S., Shiganova, T.A., Zhan, A.B., Cristescu, M.E., Eghtesadi-Araghi, P., and MacIsaac, H.J.  Multiple introductions and invasion pathways for the invasive ctenophore Mnemiopsis leidyi in Eurasia.  Biological Invasions 13(3): 679-690, 2011. 
  Read Abstract >>

  The introduction and spread of non-indigenous species (NIS) in marine ecosystems accelerated during the twentieth century owing to human activities, notably international shipping. Genetic analysis has proven useful in understanding the invasion history and dynamics of colonizing NIS and identifying their source population(s). Here we investigated sequence variation in the nuclear ribosomal Internal Transcribed Spacer region of the ctenophore Mnemiopsis leidyi, a species considered one of the most invasive globally. We surveyed four populations from the native distribution range along the Atlantic coasts of the United States and South America, as well as six populations in the introduced range from the Black, Azov, Caspian and Baltic seas. Allelic and nucleotide diversity of introduced populations were comparable to those of native populations from which they were likely drawn. Introduced populations typically exhibited lower genetic differentiation (F_ST = -0.014 - 0.421) than native populations (F_ST = 0.324 - 0.688). Population genetic analyses supported the invasion of Eurasia from at least two different pathways, the first from the Gulf of Mexico (e.g., Tampa Bay) to the Black Sea and thence to the Caspian Sea, the second from the northern part of the native distribution range (e.g., Narragansett Bay) to the Baltic Sea. The relatively high genetic diversity observed in introduced populations is consistent with large inocula and/or multiple invasions, both of which are possible given ballast water transport and the extensive native distribution of the ctenophore in the Atlantic Ocean.

• Sylvester, F., Kalaci, O., Leung, B., Lacoursière-Roussel, A., Murray, C.C., Choi, F.M., Bravo, M.A., Therriault, T.W., and MacIsaac, H.J.  Hull fouling as an invasion vector: can simple models explain a complex problem?  Journal of Applied Ecology 48(2): 415-423, 2011. 
  Read Abstract >>

  1. The most effective way to manage nonindigenous species and their impacts is to prevent their introduction via vector regulation. While ships' ballast water is very well studied and this vector is actively managed, hull fouling has received far less attention and regulations are only now being considered despite its importance for introductions to coastal, marine systems. 2. We conducted comprehensive in situ sampling and video recording of hulls of 40 transoceanic vessels to assess propagule and colonization pressure in Vancouver and Halifax, dominant coastal ports in Canada. Concomitant sampling was conducted of harbour fouling communities to compare hull and port communities as part of a vector risk assessment. 3. Although this vector has been operational for a long time, hull and harbour communities were highly divergent, with mean Sørensen's similarity values of 0·03 in Halifax and 0·01 in Vancouver, suggesting invasion risk is high. Propagule pressure (up to 600 000 ind. ship^-1) and colonization pressure (up to 156 species ship^-1) were high and varied significantly between ports, with Vancouver receiving much higher abundances and diversity of potential invaders. The higher risk of fouling introductions in Vancouver is consistent with historical patterns of successful hull fouling invasions. 4. The extent of hull fouling was modelled using ship history predictors. Propagule pressure increased with time spent in previous ports-of-call and time since last application of antifouling paint, whereas colonization pressure increased with time since last painting and with the number of regions visited by the ship. Both propagule and colonization pressure were negatively related to the time spent at sea and the latitude of ports visited. 5. Synthesis and applications. A major challenge for applied invasion ecology is the effective management of introduction vectors. We found that hull fouling has a strong potential for introduction of many species to coastal marine habitats and that management should be considered. Simple variables related to the vessels' hull husbandry, voyage, and sailing patterns may be used to predict and manage hull fouling intensity. The results presented here should interest policy makers and environmental managers who seek to reduce invasion risk, and ship owners seeking to optimize fuel efficiency.

• Butrón, A., Orive, E., and Madariaga, I.  Potential risk of harmful algae transport by ballast waters: The case of Bilbao Harbour.  Marine Pollution Bulletin 62(4): 747-757, 2011. 
  Read Abstract >>

  Ballast water exchange was measured for the first time in Bilbao Harbour, one of the most active of northern Spain. Between 1997 and 2006, 41,900,980.34 ballast water tn were loaded and 13,272,709 tn were discharged. Bilbao Harbour appears to be mainly a source of ballast water, 90% of which would be discharged in European harbours. We estimated that vessels carrying liquid and solid bulk have higher probabilities of exporting ballast water, whereas those with liquid bulk and containers are more likely to introduce it. From 30 potentially harmful phytoplankton species identified to date near harbour facilities, there would be a high risk of exporting at least Alexandrium minutum, Dinophysis sp., Heterosigma akashiwo, Karlodinium sp., Ostreopsis cf. siamensis, Pfiesteria-like and Prorocentrum minimum. Invasion risk by ballast water was tested by analyzing the response of six strains of H. akashiwo from different geographic areas to varying salinity. Results show that successful growth of foreign strains would be possible.

• Farrapeira, C.M.R., Tenorio, D.D., and do Amaral, F.D.  Vessel biofouling as an inadvertent vector of benthic invertebrates occurring in Brazil.  Marine Pollution Bulletin 62(4): 832-839, 2011. 
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  This article reviews the literature involving benthic invertebrates that are cited in association with hull fouling, reporting the species that occur on the Brazilian coast and evaluating the importance of this vector for the introduction of nonindigenous and cryptogenic invertebrates in Brazil. It discusses some of the strategies that were used by the species that allowed for their overseas transport and made it easier to cross natural barriers that otherwise would have been obstacles to their dispersion. The compiled data list 343 species (65% nonindigenous and 35% cryptogenic), mainly from the northwestern Atlantic Ocean. The traveling fauna, composed mostly of cosmopolitan species (70.3%), is primarily euryhaline and marine stenohaline, with sessile and sedentary habits. After delineating the shipborne species' ecological profiles and traveling strategies and evaluating their overlapping vectors, we concluded that hull vessels were the main vector of introduction to the Brazilian coast for 89.8% of the compiled species.

• Ruiz, G.M., Fofonoff, P.W., Steves, B., Foss, S.F., and Shiba, S.N.  Marine invasion history and vector analysis of California: a hotspot for western North America.  Diversity and Distributions 17(2): 362-373, 2011. 
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  Aim  We examine the regional dominance of California as a beachhead for marine biological invasions in western North America and assess the relative contribution of different transfer mechanisms to invasions over time.  Location  Western North America (California to Alaska, excluding Mexico).  Methods  We undertook extensive analysis of literature and collections records to characterize the invasion history of non-native species (invertebrates, microalgae and microorganisms) with established populations in coastal marine (tidal) waters of western North America through 2006. Using these data, we estimated (1) the proportion of first regional records of non-native species that occurred in California and (2) the relative contribution of transfer mechanisms to California invasions (or vector strength) over time.  Results  Excluding vascular plants and vertebrates, we identified 290 non-native marine species with established populations in western North America, and 79% had first regional records from California. Many (40 - 64%) of the non-native species in adjacent states and provinces were first reported in California, suggesting northward spread. California also drives the increasing regional rate of detected invasions. Of 257 non-native species established in California, 59% had first regional records in San Francisco Bay; 57% are known from multiple estuaries, suggesting secondary spread; and a majority were attributed to vessels (ballast water or hull fouling) or oysters, in some combination, but their relative contributions are not clear. For California, more than one vector was possible for 56% of species, and the potential contribution of ballast water, hull fouling and live trade increased over time, unlike other vectors.  Main conclusions  California, especially San Francisco Bay, plays a pivotal role for marine invasion dynamics for western North America, providing an entry point from which many species spread. This pattern is associated historically with high propagule supply and salinity. Any effective strategies to minimize new invasions throughout this region must (1) focus attention on California and (2) address current uncertainty and future shifts in vector strength.

Environmental Disturbance and Invasions

• Winder, M., Jassby, A.D., and Mac Nally, R.  Synergies between climate anomalies and hydrological modifications facilitate estuarine biotic invasions.  Ecology Letters 14(8): 749-757, 2011.
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  Environmental perturbation, climate change and international commerce are important drivers for biological invasions. Climate anomalies can further increase levels of habitat disturbance and act synergistically to elevate invasion risk. Herein, we use a historical data set from the upper San Francisco Estuary to provide the first empirical evidence for facilitation of invasions by climate extremes. Invasive zooplankton species did not become established in this estuary until the 1970s when increasing propagule pressure from Asia coincided with extended drought periods. Hydrological management exacerbated the effects of post-1960 droughts and reduced freshwater inflow even further, increasing drought severity and allowing unusually extreme salinity intrusions. Native zooplankton experienced unprecedented conditions of high salinity and intensified benthic grazing, and life history attributes of invasive zooplankton were advantageous enough during droughts to outcompete native species and colonise the system. Extreme climatic events can therefore act synergistically with environmental perturbation to facilitate the establishment of invasive species.

• Crooks, J.A., Chang, A.L., and Ruiz, G.M.  Aquatic pollution increases the relative success of invasive species.  Biological Invasions 13(1): 165-176, 2011.
  Open Access >>
  Read Abstract >>

  Although individual ecosystems vary greatly in the degree to which they have been invaded by exotic species, it has remained difficult to isolate mechanisms influencing invader success. One largely anecdotal observation is that polluted or degraded areas will accumulate more invaders than less-impacted sites. However, the role of abiotic factors alone in influencing invisibility has been difficult to isolate, often because the supply of potential invaders is confounded with conditions thought to increase vulnerability to invasion. Here, we conducted a field experiment to test how the assemblages of exotic versus native marine invertebrates changed during community assembly under different exposure levels of a common pollutant, copper. The experiment was conducted by deploying fouling panels in a Randomized Block Design in San Francisco Bay. Panels were periodically removed, placed into buckets with differing copper concentrations, and returned to the field after 3 days. This design allowed propagule availability to the plates to be statistically independent of short-term copper exposure. The results demonstrate that copper caused significant differences in community structure. Average native species richness was significantly affected by copper exposure, but average exotic richness was not. The total native species pool within treatments exhibited a greater than 40% decline within increasing copper, while the exotic species pool did not change significantly. These results confirm that anthropogenic alteration of abiotic factors influences invader success, indicating that management strategies to reduce invader impacts should include both efforts to improve environmental conditions as well as reduce invader supply.

• Gennaro, P. and Piazzi, L.  Synergism between two anthropic impacts: Caulerpa racemosa var. cylindracea invasion and seawater nutrient enrichment.  Marine Ecology Progress Series 427: 59-70, 2011.
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  Although eutrophication and biological invasions are recognized as important elements of global change, few studies have assessed how their synergism can affect structural and functional traits of marine ecosystems. The present study aimed to evaluate the effect of seawater nutrient enrichment on the spread of the introduced Chlorophyta Caulerpa racemosa var. cylindracea and the interactive effects of nutritional enrichment and C. racemosa invasion on the native macroalgal assemblages of a subtidal rocky bottom. To achieve these objectives, a manipulative field experiment was carried out at 24 m depth in the northwestern Mediterranean Sea by adding C. racemosa and supplying the water column with nutrients. The following treatments were applied: non-manipulated assemblages, nutrient enrichment, addition of C. racemosa, and both nutrient enrichment and addition of C. racemosa. Results showed that C. racemosa spread was enhanced by nutrient enrichment. Moreover, a significant interaction between nutritional increase and C. racemosa invasion was detected: the effects of C. racemosa invasion on native macroalgal assemblages were amplified by nutrient enrichment. Results suggested that synergism between effects of different anthropogenic impacts can have severe consequences on the integrity of marine ecosystems.

• Lapointe, B.E. and Bedford, B.J.  Stormwater nutrient inputs favor growth of non-native macroalgae (Rhodophyta) on O'ahu, Hawaiian Islands.  Harmful Algae 10(3): 310-318, 2011.
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  In Hawaii, blooms of native and non-native macroalgae (limu) have become increasingly problematic in recent decades. Although the role of human vectors in introducing non-native macroalgae is well documented, the ecological role of nutrient pollution in facilitating blooms of these species is not. This study assessed the effects of stormwater discharges on the diversity, abundance, and nutrient content (C, N, P and δ¹⁵N) of native and non-native limu at three sites in the intertidal zone at Ewa Beach, O'ahu. The results showed that native limu species diversity and abundance decreased with proximity to a stormwater outfall (ASWO), whereas non-native species abundance increased. Limu tissue δ¹⁵N values at all three sites were within the range reported for sewage N. δ¹⁵N, %N, and N:P ratios all increased with proximity to the ASWO, supporting the hypothesis that stormwater was a primary source of N enrichment in the study area. In contrast to N, limu %P showed little change among the sites, suggesting that the generally high N:P ratios, indicative of P-limitation, resulted from high N:P ratios from the upland watershed. Abundance and tissue %N of the non-native rhodophyte Acanthophora spicifera increased with proximity to the ASWO and were strongly correlated (r² = 0.94) compared to native rhodophytes, indicating that stormwater N enrichment provided this invader a competitive advantage (lower C:N ratio) over native limu. These results indicate that the spread of non-native macroalgae in oligotrophic coral reef regions can be facilitated by anthropogenic nutrients in stormwater runoff, thereby threatening native species and ecosystem services.

Impacts

• Sala, E., Kizilkaya, Z., Yildirim, D., and Ballesteros, E.  Alien marine fishes deplete algal biomass in the Eastern Mediterranean.  PLoS ONE 6(2): art. e17356, 2011.
  Open Access >>  
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  One of the most degraded states of the Mediterranean rocky infralittoral ecosystem is a barren composed solely of bare rock and patches of crustose coralline algae. Barrens are typically created by the grazing action of large sea urchin populations. In 2008 we observed extensive areas almost devoid of erect algae, where sea urchins were rare, on the Mediterranean coast of Turkey. To determine the origin of those urchin-less 'barrens', we conducted a fish exclusion experiment. We found that, in the absence of fish grazing, a well-developed algal assemblage grew within three months. Underwater fish censuses and observations suggest that two alien herbivorous fish from the Red Sea (Siganus luridus and S. rivulatus) are responsible for the creation and maintenance of these benthic communities with extremely low biomass. The shift from well-developed native algal assemblages to 'barrens' implies a dramatic decline in biogenic habitat complexity, biodiversity and biomass. A targeted Siganus fishery could help restore the macroalgal beds of the rocky infralittoral on the Turkish coast.

• Irigoyen, A.J., Eyras, C., and Parma, A.M.  Alien algae Undaria pinnatifida causes habitat loss for rocky reef fishes in north Patagonia.  Biological Invasions 13(1): 17-24, 2011.
  Open Access >>  
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  Since the introduction of Undaria into Nuevo Gulf, Argentina, around 1992, this alien seaweed has now colonized different sites over 700 km of coast, forming dense seasonal forests in waters from 0 to 15 meters in depth. In the spring it is common for plants of Undaria to break away from the substrate and be transported by sea currents. As Undaria gets stuck onto reefs it has the potential to reduce habitat quality for reef fish by physically obstructing refuges. This study aims to assess the impact of Undaria on the abundance of four species of rocky-reef fishes by an observational experiment. Fish abundance on reefs with and without Undaria was estimated by underwater visual census methods. Sites were classified according to their topographical relief, as this was expected to influence the effect of Undaria on the abundance of reef fishes. Fish abundance decreased markedly in low-relief reefs that had been covered by Undaria. In contrast, the drifting Undaria had no effect on the abundance of any of the fish species considered in high-relief reefs, where it tends to cover only the lowest-lying areas, leaving much of the refuges for fish unaffected. In conclusion, the presence of Undaria off the coast of Argentina results in transitory habitat loss for reef fishes inhabiting low-relief reefs during late spring and early summer. Although we do not know how much of a threat this habitat loss represents for the conservation of reef fish populations of northern Patagonia, the documented local impact of Undaria within the gulfs is strong and may affect a number of recreational and commercial activities which are centered on the reefs and their fish assemblages.

• Bonnaud, E., Medina, F.M., Vidal, E., Nogales, M., Tershy, B., Zavaleta, E., Donlan, C.J., Keitt, B., LeCorre, M., and Horwath, S.V.  The diet of feral cats on islands: a review and a call for more studies.  Biological Invasions 13(3): 581-603, 2011.  
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  Cats are among the most successful and damaging invaders on islands and a significant driver of extinction and endangerment. Better understanding of their ecology can improve effective management actions such as eradication. We reviewed 72 studies of insular feral cat diet from 40 islands worldwide. Cats fed on a wide range of species from large birds and medium sized mammals to small insects with at least 248 species consumed (27 mammals, 113 birds, 34 reptiles, 3 amphibians, 2 fish and 69 invertebrates). Three mammals, 29 birds and 3 reptiles recorded in the diet of cats are listed as threatened by the IUCN. However, a few species of introduced mammals were the most frequent prey, and on almost all islands mammals and birds contributed most of the daily food intake. Latitude was positively correlated with the predation of rabbits and negatively with the predation of reptiles and invertebrates. Distance from landmass was positively correlated with predation on birds and negatively correlated with the predation of reptiles. The broad range of taxa consumed by feral cats on islands suggests that they have the potential to impact almost any native species, even the smallest ones under several grams, that lack behavioral, morphological or life history adaptations to mammalian predators. Insular feral cat's reliance on introduced mammals, which evolved with cat predation, suggests that on many islands, populations of native species have already been reduced.

• Simberloff, D.  How common are invasion-induced ecosystem impacts?  Biological Invasions 13(5): 1255-1268, 2011.  
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  It would be an exaggeration to argue that most invasions produce ecosystem impacts, and the term should be reserved for cases in which many species in an ecosystem are affected. However, certain facts suggest that true ecosystem impacts are more common than is normally assumed. First, the term ''ecosystem impact'' has often been reserved for cases in which the nutrient regime or nutrient cycling is affected, whereas physical structural and other changes in ecosystems ought to be included. Second, as with all ecology, very few systems and species have been studied relative to all those that exist, so it is likely that many ecosystem impacts remain to be detected. Third, there are many types of impacts, many are idiosyncratic, many are subtle, and many are indirect, so it is likely that many impacts have simply not been recognized even in studied systems. Finally, the frequency of the lag phenomenon in invasions implies that at least some existing non-native species that are currently having little or no impact will eventually have much greater ones. These facts suggest that, even if it would be an overstatement to say that most invasions cause ecosystem impacts, it would not be more of an overstatement than the common assertion that very few introduced species have any significant impact.

• Tomas, F., Box, A., and Terrados, J.  Effects of invasive seaweeds on feeding preference and performance of a keystone Mediterranean herbivore.  Biological Invasions 13(7): 1559-1570, 2011.  
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  The consequences of invasive species on ecosystem processes and ecological interactions remain poorly understood. Predator-prey interactions are fundamental in shaping species evolution and community structure and can be strongly modified by species introductions. To fully understand the ecological effects of invasive species on trophic linkages it is important to characterize novel interactions between native predators and exotic prey and to identify the impacts of invasive species on the performance of native predators. Although seaweed invasions are a growing global concern, our understanding of invasive algae-herbivore interactions is still very limited. We used a series of feeding experiments between a native herbivore and four invasive algae in the Mediterranean Sea to examine the potential of native sea urchins to consume invasive seaweeds and the impacts of invasive seaweed on herbivore performance. We found that three of the four invasive species examined are avoided by native herbivores, and that feeding behaviour in sea urchins is not driven by plant nutritional quality. On the other hand, Caulerpa racemosa is readily consumed by sea urchins, but may escape enemy control by reducing their performance. Recognizing the negative impacts of C. racemosa on herbivore performance has highlighted an enemy escape mechanism that contributes to explaining how this widespread invasive alga, which is preferred and consumed by herbivores, is not eradicated by grazing in the field. Furthermore, given the ecological and economic importance of sea urchins, negative impacts of invasive seaweeds on their performance could have dramatic effects on ecosystem function and services, and should be accounted for in sea urchin population management strategies.

• Zaiko, A., Lehtiniemi, M., Naršcius, A., and Olenin, S.  Assessment of bioinvasion impacts on a regional scale: a comparative approach.  Biological Invasions 13(8): 1739-1765, 2011.
  Open Access >>  
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  This paper presents an overall bioinvasion impact assessment on the scale of a large marine region - the Baltic Sea, as defined by the Helsinki Commission. The methodology is based on a classification of the abundance and distribution range of alien species and the magnitude of their impacts on native communities, habitats and ecosystem functioning aggregated in a "Biopollution Level" index (BPL) which ranges from 'no impact' (BPL=0) to 'massive impact' (BPL=4). The assessment performed for nine Baltic sub-regions revealed that documented ecological impact is only known for 43 alien species out of 119 registered in the Sea. The highest biopollution (BPL=3, strong impact) occurs in coastal lagoons, inlets and gulfs, and the moderate biopollution (BPL=2) - in the open sea areas. The methodology was also used to classify species into alien (BPL=0) versus 'impacting' species (BPL>0), which can be divided into 'potentially invasive' (BPL=1) and 'invasive' (BPL>1) ones. No clear correlation between the number of established alien and impacting species was found in the sub-regions of the Baltic Sea. The methodology, although requiring a substantial research effort, proved to be useful for interregional comparisons and evaluating the bioinvasion effects of individual alien species.

• Lesser, M.P. and Slattery, M.  Phase shift to algal dominated communities at mesophotic depths associated with lionfish (Pterois volitans) invasion on a Bahamian coral reef.  Biological Invasions 13(8): 1855-1868, 2011.  
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  Mesophotic coral reefs (30-150m) have been assumed to be physically and biologically connected to their shallow-water counterparts, and thus may serve as refugia for important taxonomic groups such as corals, sponges, and fish. The recent invasion of the Indo-Pacific lionfish ( Pterois volitans) onto shallow reefs of the Caribbean and Bahamas has had significant, negative, effects on shallow coral reef fish populations. In the Bahamas, lionfish have extended their habitat range into mesophotic depths down to 91 m where they have reduced the diversity of several important fish guilds, including herbivores. A phase shift to an algal dominated (>50% benthic cover) community occurred simultaneously with the loss of herbivores to a depth of 61 m and caused a significant decline in corals and sponges at mesophotic depths. The effects of this invasive lionfish on mesophotic coral reefs and the subsequent changes in benthic community structure could not be explained by coral bleaching, overfishing, hurricanes, or disease independently or in combination. The significant ecological effects of the lionfish invasion into mesophotic depths of coral reefs casts doubt on whether these communities have the resilience to recover themselves or contribute to the recovery of their shallow water counterparts as refugia for key coral reef taxa.

• Darling, E.S., Green, S.J., O'Leary, J.K., and Côté, I.M.  Indo-Pacific lionfish are larger and more abundant on invaded reefs: a comparison of Kenyan and Bahamian lionfish populations.  Biological Invasions 13(9): 2045-2051, 2011.  
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  The invasion by Indo-Pacific lionfish (Pterois volitans and P. miles) of the western Atlantic, Caribbean and Gulf of Mexico is emerging as a major threat to coral reef communities across the region. Comparing native and introduced populations of invasive species can reveal shifts in ecology and behaviour that can accompany successful invasions. Using standardized field surveys replicated at multiple sites in Kenya and the Bahamas, we present the first direct comparisons of lionfish density, body size, biomass and behaviour between native and invaded coral reefs. We found that lionfish occur at higher densities with larger body sizes and total biomass on invaded Bahamian coral reefs than the ecologically equivalent species (P. miles) does on native Kenyan reefs. However, the combined average density of the five lionfish species (Pterois miles, P. antennata, P. radiata, Dendrochirus brachypterus and D. zebra) on Kenyan reefs was similar to the density of invasive lionfish in the Bahamas. Understanding the ecological processes that drive these differences can help inform the management and control of invasive lionfish.

• Žuljevic, A., Thibaut, T., Despalatovic, M., Cottalorda, J.-M., Nikolic, V., Cvitkovic, I., and Antolic, B.  Invasive alga Caulerpa racemosa var. cylindracea makes a strong impact on the Mediterranean sponge Sarcotragus spinosulus.  Biological Invasions 13(10): 2303-2308, 2011.  
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  Here we present the first observation of the impact of the invasive Caulerpa racemosa var. cylindracea on native photophilic sponge species in the Adriatic Sea, with special focus on Sarcotragus spinosulus. Caulerpa racemosa var. cylindracea is able to completely overgrow the sponge, developing an exceptionally thick canopy with a maximum measured density of 1,887 m of stolons m^-2 and 40,561 fronds m^-2. Necrosis of the sponge surface was significantly correlated with the algal dry biomass, frond number and stolon length. Dense algal canopy, penetration of the algal stolon and rhizoids into the sponge oscula and covering of the ostiae probably diminishes the seawater circulation through the sponge and consequently results in its smothering and even death. We suggest that chemotropism is the reason why C. racemosa penetrates the sponge oscula and establishes such dense canopy on the sponge.

• Falk-Petersen, J., Renaud, P., and Anisimova, N.  Establishment and ecosystem effects of the alien invasive red king crab (Paralithodes camtschaticus) in the Barents Sea – a review.  ICES Journal of Marine Science 68(3): 479-488, 2011.  
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  Since its introduction to the Barents Sea from the North Pacific in the 1960s, the red king crab (Paralithodes camtschaticus) has become invasive. The crab represents an important source of income, but also a potential threat to the highly productive fisheries in the region through its ecosystem impacts. A literature review was conducted, identifying factors contributing to the success of the crab as well as its interactions with native biota. Characteristics of the Barents Sea and the crab itself that may explain its success include suitable habitat for settlement and growth of the larvae; the wide range of habitats occupied throughout its life history, high mobility, generalist prey choice, low fishing pressure during establishment, and the lack of parasites. Being a large, bottom-feeding omnivore of great mobility, the king crab can significantly impact the ecosystem. Reduced benthic diversity and biomass have been registered in invaded areas. Important prey items include large epibenthic organisms whose structures also represent important habitat. Impacts on commercial and non-commercial fish species, through egg predation or indirect interactions, are difficult to detect and predict.

• Oug, E., Cochrane, S.K.J., Sundet, J.H., Norling, K., and Nilsson, H.C.  Effects of the invasive red king crab (Paralithodes camtschaticus) on soft-bottom fauna in Varangerfjorden, northern Norway.  Marine Biodiversity 41(3): 467-479, 2011.  
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  The red king crab (Paralithodes camtschaticus) was introduced from the northern Pacific to the Russian Murman coast during the 1960s and 1970s. Over the subsequent decades, the crab has become established in northern Norwegian waters, where it continues spreading westward. The crab is an active predator on benthic fauna, especially feeding in deep soft-bottom environments. The present studies, carried out in the Varanger area close to the Russian border in 2007-2009, indicate that soft-bottom epifauna and infauna have become markedly reduced in crab-invaded areas. For infauna, quantitative data from 1994 were used as a basis to compare faunal composition before and after the crab became abundant in the area. It appeared that echinoderms, non-moving burrowing and tube-dwelling polychaetes, and most bivalves were reduced, whereas some small-sized polychaetes and small bivalves had increased. In situ sediment profile imagery (SPI) was used to examine sediment structure and biogenic activity. At several locations, the sediment habitat quality was degraded due to hypoxic conditions and low biological activity below surface layers. It is suggested that the crab has removed organisms performing important functions such as bio-irrigation and sediment reworking. Hence, it appears that the crab may reduce the functional diversity of the resident species assemblages, which may have overall implications for ecosystem function, production and responses to other environmental stressors.

• Grosholz, E., Lovell, S., Besedin, E., and Katz, M.  Modeling the impacts of the European green crab on commercial shellfisheries.  Ecological Applications 21(3): 915-924, 2011.  
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  Coastal resource managers are often tasked with managing coastal ecosystems that are stressed by overexploitation, climate change, contaminants, and habitat loss, as well as biological invasions. Therefore, managers increasingly need better economic data to help them prioritize their management strategies and distribute their increasingly limited resources to those strategies. Despite frequent pronouncements about the substantial ecological and economic impacts of invasive species, there have been few if any rigorous analyses of the economic impacts of invasive species in coastal systems. Here we present a bioeconomic analysis of the impacts of the European green crab, Carcinus maenas, on commercial shellfisheries along the West Coast of the United States. Green crabs are among the most comprehensively studied and widely distributed invasive species in coastal systems, with established populations on every continent except Antarctica. Their impacts on commercial bivalve fisheries have been alleged or substantiated to varying degrees, but no formal analysis of the economic impacts of the green crab has been conducted. We assess economic impacts using a combination of ecological and economic models. The ecological models incorporate green crab dispersal and description of estuarine habitat and the relationship between green crab abundance and predation on prey populations. The economic analysis focuses on the green crab impacts on commercial shellfisheries, including both historical and present impacts of green crabs on several important shellfisheries, including soft-shell clams, blue mussels, scallops, hard-shell clams, and Manila clams. We conclude that the past and present economic impacts on the West Coast shellfisheries are minor, although losses could increase significantly if densities increase or with northward range expansion into Alaska.

• de Rivera, C.E., Grosholz, E.D., and Ruiz, G.M.  Multiple and long-term effects of an introduced predatory crab.  Marine Ecology Progress Series 429: 145-155, 2011.  
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  Despite the importance of invasions, few studies have explored their long-term consequences in marine systems or examined multiple types of population-level effects. Initial effects, however, may not persist over longer time frames; effects have been shown to wane in freshwater systems. We combined 14 yr of field surveys (1993 to 2006) with manipulative experiments to examine the potential for multiple effects of a nonindigenous crab  Carcinus maenas on the native shore crab Hemigrapsus oregonensis over time in central California. H. oregonensis abundance was negatively correlated with C. maenas abundance. However, H. oregonensis abundance rebounded to pre-invasion levels once C. maenas numbers declined. Other measured changes include a marked decrease in H. oregonensis body size and an increase in the proportion of H. oregonensis in the high intertidal zone since the arrival of C. maenas. These changes in body size and tidal distribution persisted nearly a decade beyond the peak abundance of C. maenas and after H. oregonensis numbers rebounded. Observed changes in the distribution of the H. oregonensis population correspond to shifts in C. maenas abundance, and experiments support a causal relationship. Stepwise regression suggests a complex and possibly nonlinear relationship between predictor variables and H. oregonensis size and distribution. Overall, our data indicate strong persistent effects on multiple attributes, with a lag in recovery with declining invader abundance, underscoring the potential for long-term effects that are decoupled from year-to-year invasion dynamics.

• Muñoz, R.C., Currin, C.A., and Whitfield, P.E.  Diet of invasive lionfish on hard bottom reefs of the Southeast USA: insights from stomach contents and stable isotopes.  Marine Ecology Progress Series 432: 181-193, 2011.  
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  The Indo-Pacific lionfish (Pterois volitans and P. miles complex) has become widely established along the United States Southeast coast and continues to colonize the Caribbean, yet its biology and ecology is only beginning to be understood. We used stomach contents and stable isotope analyses to determine the diet of lionfish in the warm-temperate hard bottom reef community in the Southeast US Atlantic Ocean. During June to August 2004 and 2006, we collected lionfish with SCUBA from 18 different locations in Onslow Bay, North Carolina, at depths of 30 to 45 m. In 2006, we also conducted visual surveys of small benthic fishes to estimate the abundances of potential prey. Analyses of stomach contents (n = 183) and stable isotopes (n = 115) suggest a generalist carnivorous diet, and prey categories were predominately fish (~99% of total volume) from 16 families. Major differences in the importance of prey occurred between years. Serranidae and Scaridae dominated the diet in 2004, while Haemulidae and Carangidae were important in 2006. Analyses of visual prey surveys did not reveal specialization on particular prey taxa but instead suggest that prey are consumed in relation to their local abundance. Given current theory pertaining to invasive species impacts, the expanding lionfish distribution, and observations that lionfish appear capable of settling to many different habitat types, the overall pattern of generalist piscivory emerging from these data indicates the potential for significant impacts to the invaded community.

• Medina, F.M., Bonnaud, E., Vidal, E., Tershy, B.R., Zavaleta, E.S., Donlan, J.C., Keitt, B.S., Le Corre, M., Horwath, S.V., and Nogales, M.  A global review of the impacts of invasive cats on island endangered vertebrates.  Global Change Biology 17(11): 3503-3510, 2011.  
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  Cats are generalist predators that have been widely introduced to the world's ~179 000 islands. Once introduced to islands, cats prey on a variety of native species many of which lack evolved defenses against mammalian predators and can suffer severe population declines and even extinction. As islands house a disproportionate share of terrestrial biodiversity, the impacts of invasive cats on islands may have significant biodiversity impacts. Much of this threatened biodiversity can be protected by eradicating cats from islands. Information on the relative impacts of cats on different native species in different types of island ecosystems can increase the efficiency of this conservation tool. We reviewed feral cat impacts on native island vertebrates. Impacts of feral cats on vertebrates have been reported from at least 120 different islands on at least 175 vertebrates (25 reptiles, 123 birds, and 27 mammals), many of which are listed by the International Union for the Conservation of Nature. A meta-analysis suggests that cat impacts were greatest on endemic species, particularly mammals and greater when non-native prey species were also introduced. Feral cats on islands are responsible for at least 14% global bird, mammal, and reptile extinctions and are the principal threat to almost 8% of critically endangered birds, mammals, and reptiles.

Prevention and Control

• Tobin, P.C., Berec, L., and Liebhold, A.M.  Exploiting Allee effects for managing biological invasions.  Ecology Letters 14(6): 615-624, 2011. 
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  Biological invasions are a global and increasing threat to the function and diversity of ecosystems. Allee effects (positive density dependence) have been shown to play an important role in the establishment and spread of non-native species. Although Allee effects can be considered a bane in conservation efforts, they can be a benefit in attempts to manage non-native species. Many biological invaders are subject to some form of an Allee effect, whether due to a need to locate mates, cooperatively feed or reproduce or avoid becoming a meal, yet attempts to highlight the specific exploitation of Allee effects in biological invasions are surprisingly unprecedented. In this review, we highlight current strategies that effectively exploit an Allee effect, and propose novel means by which Allee effects can be manipulated to the detriment of biological invaders. We also illustrate how the concept of Allee effects can be integral in risk assessments and in the prioritization of resources allocated to manage non-native species, as some species beset by strong Allee effects could be less successful as invaders. We describe how tactics that strengthen an existing Allee effect or create new ones could be used to manage biological invasions more effectively.

• Barbour, A.B., Allen, M.S., Frazer, T.K., and Sherman, K.D.  Evaluating the potential efficacy of invasive lionfish (Pterois volitans) removals.  PLoS ONE 6(5): art. e19666, 2011.
  Open Access >>  
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  The lionfish, Pterois volitans (Linnaeus) and Pterois miles (Bennett), invasion of the Western Atlantic Ocean, Caribbean Sea and Gulf of Mexico has the potential to alter aquatic communities and represents a legitimate ecological concern. Several local removal programs have been initiated to control this invasion, but it is not known whether removal efforts can substantially reduce lionfish numbers to ameliorate these concerns. We used an age-structured population model to evaluate the potential efficacy of lionfish removal programs and identified critical data gaps for future studies. We used high and low estimates for uncertain parameters including: length at 50% vulnerability to harvest (Lvul), instantaneous natural mortality (M), and the Goodyear compensation ratio (CR). The model predicted an annual exploitation rate between 35 and 65% would be required to cause recruitment overfishing on lionfish populations for our baseline parameter estimates for M and CR (0.5 and 15). Lionfish quickly recovered from high removal rates, reaching 90% of unfished biomass six years after a 50-year simulated removal program. Quantifying lionfish natural mortality and the size-selective vulnerability to harvest are the most important knowledge gaps for future research. We suggest complete eradication of lionfish through fishing is unlikely, and substantial reduction of adult abundance will require a long-term commitment and may be feasible only in small, localized areas where annual exploitation can be intense over multiple consecutive years.

• Mumby, P.J., Harborne, A.R., and Brumbaugh, D.R.  Grouper as a natural biocontrol of invasive lionfish.  PLoS ONE 6(6): art. e21510, 2011.
  Open Access >>  
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  Lionfish (Pterois volitans/miles) have invaded the majority of the Caribbean region within five years. As voracious predators of native fishes with a broad habitat distribution, lionfish are poised to cause an unprecedented disruption to coral reef diversity and function. Controls of lionfish densities within its native range are poorly understood, but they have been recorded in the stomachs of large-bodied Caribbean groupers. Whether grouper predation of lionfish is sufficient to act as a biocontrol of the invasive species is unknown, but pest biocontrol by predatory fishes has been reported in other ecosystems. Groupers were surveyed along a chain of Bahamian reefs, including one of the region's most successful marine reserves which supports the top one percentile of Caribbean grouper biomass. Lionfish biomass exhibited a 7-fold and non-linear reduction in relation to the biomass of grouper. While Caribbean grouper appear to be a biocontrol of invasive lionfish, the overexploitation of their populations by fishers, means that their median biomass on Caribbean reefs is an order of magnitude less than in our study. Thus, chronic overfishing will probably prevent natural biocontrol of lionfishes in the Caribbean.

• Bonnaud, E., Zarzoso-Lacoste, D., Bourgeois, K., Ruffino, L., LeGrand, J., and Vidal, E.  Top-predator control on islands boosts endemic prey but not mesopredator.  Animal Conservation 13(6): 556-567, 2010.  
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  Introduced predators on islands are responsible for numerous native species extirpations and extinctions. Predation by cats is particularly detrimental to seabirds and cat control or eradication is generally the best option to reduce their negative impacts on native fauna. However, potential cascading effects, such as mesopredator release effect, need to be monitored after cat removal. In Port-Cros Island, a cat control campaign was undertaken to eliminate the strong and recurrent threat from feral cat predation to the small yelkouan shearwater Puffinus yelkouan population, without harming a neutered domestic cat population. To evaluate the conservation value of this campaign for an island endemic and endangered species, the diet and impact of the remaining domestic cats were studied through scat analysis and trap success. Moreover, to evaluate the recovery of the seabird population and detect any potential mesopredator release effect, shearwater and rat populations were monitored before, alongside and after the cat control. Only live traps were used, and most cats were trapped in the first year of cat eradication. The last incidence of cat predation on the yelkouan shearwater occurred the following year. The recovery of the shearwater population, occurring the first year of cat control, was mainly attributable to the settlement of new breeders in the colony. Rat population dynamics fluctuated widely but, even though the interactions between rats and shearwaters at breeding cavities increased, no evidence of rat predation on shearwaters was recorded. Thus, cat control on Port-Cros Island was a success for native species conservation, proving that such management strategy can induce an increase in the population of the endemic species, here the yelkouan shearwater, without any evidence of a mesopredator release effect.

• Hopkins, G.A., Forrest, B.M., Piola, R.F., and Gardner, J.P.A.  Factors affecting survivorship of defouled communities and the effect of fragmentation on establishment success.  Journal of Experimental Marine Biology and Ecology 396(2): 233-243, 2011.  
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  The environmental risks associated with the defouling of artificial structures (e.g., vessels, oil rigs, marina pontoons, aquaculture structures) in the marine environment are gaining international attention. This paper presents a series of laboratory- and field-based experiments that collectively aimed to elucidate biotic and abiotic factors that influence re-establishment success of biofouling organisms and fragmented colonial organisms defouled to the seabed. Reattachment success of colonial organisms experimentally fragmented was found to be species specific and dependent on fragment size. In both laboratory and field trials, some colonial ascidians had consistently greater reattachment success for larger size classes of fragments, while other encrusting and erect taxa showed poor reattachment capabilities. This study also revealed that sedimentation and turbidity are likely to have a strong influence on the survivorship of defouled material. Furthermore, for both high and low sedimentary environments, survivorship was found to be greater where predators were excluded. Despite risks posed by non-indigenous species (NIS), it is proposed that in-water defouling may be an appropriate management response in situations where a ''do nothing'' approach is potentially more detrimental. Moreover, results from this study suggest that environmental risks associated with defouling may be mitigated through appropriate defouling strategies (e.g., defouling location, frequency and method). In order to increase our predictive abilities for NIS establishment success resulting from in-water defouling, future studies should aim to further elucidate the relative importance of factors affecting survivorship of defouled material at locations where defouling is routinely undertaken.

• Miller, A.W., Frazier, M., Smith, G.E., Perry, E.S., Ruiz, G.M., and Tamburri, M.N.  Enumerating sparse organisms in ships' ballast water: Why counting to 10 is not so easy.  Environmental Science and Technology 45(8): 3539-3546, 2011.  
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  To reduce ballast water-borne aquatic invasions worldwide, the International Maritime Organization and United States Coast Guard have each proposed discharge standards specifying maximum concentrations of living biota that may be released in ships' ballast water (BW), but these regulations still lack guidance for standardized type approval and compliance testing of treatment systems. Verifying whether BW meets a discharge standard poses significant challenges. Properly treated BW will contain extremely sparse numbers of live organisms, and robust estimates of rare events require extensive sampling efforts. A balance of analytical rigor and practicality is essential to determine the volume of BIN that can be reasonably sampled and processed, yet yield accurate live counts. We applied statistical modeling to a range of sample volumes, plankton concentrations, and regulatory scenarios (i.e., levels of type I and type II errors), and calculated the statistical power of each combination to detect noncompliant discharge concentrations. The model expressly addresses the roles of sampling error, BW volume, and burden of proof on the detection of noncompliant discharges in order to establish a rigorous lower limit of sampling volume. The potential effects of recovery errors (i.e., incomplete recovery and detection of live biota) in relation to sample volume are also discussed.

• Wheeler, G.S., Taylor, G.S., Gaskin, J.F., and Purcell, M.F.  Ecology and management of sheoak (Casuarina spp.), an invader of coastal Florida, U.S.A.  Journal of Coastal Research 27(3): 485-492, 2011.  
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  The Casuarina spp. are invasive plants in Florida that threaten biological diversity and beach integrity of coastal habitats. The trees include three species and their hybrids that aggressively invade riverine and coastal areas. Of the three species, C. equisetifolia and C. glauca are highly salt tolerant and widespread in coastal areas. The third species, C. cunninghamiana, invades riverine habitats. These species pose dangers to both the environment and public safety. The environmental damage includes interfering with nesting by endangered sea turtles, American crocodiles, and the rare swallow-tailed kite. Additionally, allelochemical leachates reduce germination and establishment of native vegetation. Casuarina-infested beaches are more prone to sand loss and erosion. Moreover, with shallow roots and tall canopies, they are among the first trees to fall in high winds and as such restrict evacuation efforts during hurricanes. Control of these species is mostly with herbicides, requiring repeated applications and monitoring. One of the most cost-effective means of controlling these invasive species would be with classical biological control. Australian surveys for potential biological control agents began in 2004, resulting in the discovery of several promising candidates. These include seed-feeding torymid wasps, defoliating caterpillars and weevils, leaf tip gall-formers from cecidomyiid midges, and sap-feeding psyllids. Continued work is needed to determine the suitability of these species for biological control. Despite conflicts of interest expressed by some homeowners and the agricultural industry who value the trees for shade and windbreaks, there are good prospects for safe and effective biological control of these invasive species.

• Leichsenring, J. and Lawrence, J.  Effect of mid-oceanic ballast water exchange on virus-like particle abundance during two trans-Pacific voyages.  Marine Pollution Bulletin 62(5): 1103-1108, 2011.  
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  Ballast water is a potential source of invasive species, including viruses that target a variety of hosts. We sampled ballast during two trans-Pacific voyages and analyzed the efficacy of mid-oceanic exchange in reducing virus-like particle (VLP) abundance. Exchange did not significantly reduce virus abundance during the first voyage (P = 0.874), whereas it reduced viral abundance 3.9-fold from 1.8 x 10⁷ to 0.47 x 10⁷ VLP mL^-1 during the second voyage (P < 0.0001). Despite the impact of exchange during the second voyage, virus abundances were not significantly different between exchanged and unexchanged tanks upon arrival in Canada (P = 0.363) and Canadian port water samples (P = 0.502). Regressions between environmental parameters and VLP abundance uncovered negative correlations between salinity and viral abundance during one, and dissolved oxygen and viral abundance during the second voyage. In summary, ballast tanks are highly variable with respect to total virus abundance, and the efficacy of exchange requires investigation into the dynamics of specific viruses.

Eradication

• Plentovich, S., Eijzenga, J., Eijzenga, H., and Smith, D.  Indirect effects of ant eradication efforts on offshore islets in the Hawaiian Archipelago.  Biological Invasions 13(3): 545-557, 2011. 
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  Invasive species eradication and control are considered vital components of the conservation, restoration, and management of many native ecosystems. Invasive ants, which are notoriously difficult to eradicate, can cause catastrophic changes in ecosystems and are aggressive colonists. Here we report the eradication and control of two widely distributed invasive ants and subsequent unanticipated effects on arthropod and avian communities. We used a paired experimental design that included 1 year of baseline data collection, to test the effects of the formicide hydramethylnon on abundances of two ant species on two pairs of offshore islets. Pheidole megacephala was eradicated from the treated islet in pair 1 and was not detected during 2003-2008. On pair 2 Solenopsis geminata numbers declined, but the species remained present. Target ant densities remained high on untreated islets. Application of hydramethylnon reduced numbers of alien cockroaches (Order: Blattaria), but we did not detect effects on other non-target arthropods. The eradication of P. megacephala was followed by dynamic compositional changes in the ant community, including the apparent colonization by three species (S. geminata, Tetramorium bicarinatum and Anoplolepis gracilipes) previously undetected on the islet. One of these, A. gracilipes, underwent a rapid range expansion during 2006-2008 which corresponded with reduced seabird nesting success. We conclude that hydramethylnon can be used effectively to eradicate P. megacephala. However, ant eradications can have detrimental effects on ecosystems and the potential for subsequent colonization of sites by other ant species that may be more harmful and more difficult to eradicate needs to be considered.

• Hopkins, G.A., Forrest, B.M., Jiang, W.M., and Gardner, J.P.A.  Successful eradication of a non-indigenous marine bivalve from a subtidal soft-sediment environment.  Journal of Applied Ecology 48(2): 424-431, 2011.  
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  1. Biofouling, the accumulation of biological growth on submerged surfaces such vessel hulls and artificial structures, is an important transport pathway that can facilitate the establishment of marine non-indigenous species in new locations. Despite efforts to develop effective tools to eradicate newly established populations before they become widespread and beyond control, eradication successes are scarce in the marine environment. This paper describes a dredge-based eradication of the brown mussel Perna perna from a deep (c. 44 m) soft-sediment habitat in central New Zealand, following the discovery of this species amongst biofouling organisms physically removed (i.e. defouled) from a drilling rig. 2. We evaluated the efficacy of dredging in removing P. perna and other target species, and determined whether a density-based eradication success criterion had been achieved. The catchability coefficient (q) of the defouled material was estimated using catch data, and the dredge efficiency (E) was determined. Initial and remaining mussel densities were then calculated using estimates of E. The reliability of these estimates was tested by simulations. 3. A total of 227 dredge tows covering c. 94% of a 12·6 ha target area were undertaken, and an estimated 35 tonnes of material defouled from the rig was dredged from the seabed and disposed of in a landfill. 4. Estimates of q and E were 0·0054 and 0·30 (respectively) and mussel densities at the completion of the eradication programme were estimated to be c. 0·5 m^-2, well below the success criterion of 10 m^-2. From our simulations, it was estimated that 71 dredge tows would be required to remove 50% of the initial population, whilst 232 dredge tows would be needed to achieve a 90% reduction in population size. 5. Synthesis and applications. The eradication of non-indigenous bivalves from a relatively deep (>40 m) soft-sediment environment is unprecedented and highlights that, with appropriate tools and other resources, eradication is feasible even in challenging circumstances. Where complete elimination of a pest is not feasible, alternative density-based success criteria can be developed that, if achieved, can effectively mitigate risks. This study highlights the need for further development of both vector treatment options and pest eradication tools, and improved policy surrounding in-water defouling in the coastal environment.

• Oppel, S., Beaven, B.M., Bolton, M., Vickery, J., and Bodey, T.W.  Eradication of invasive mammals on islands inhabited by humans and domestic animals.  Conservation Biology 25(2): 232-240, 2011.  
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  Non-native invasive mammal species have caused major ecological change on many islands. To conserve native species diversity, invasive mammals have been eradicated from several islands not inhabited by humans. We reviewed the challenges associated with campaigns to eradicate invasive mammals from islands inhabited by humans and domestic animals. On these islands, detailed analyses of the social, cultural, and economic costs and benefits of eradication are required to increase the probability of local communities supporting the eradication campaign. The ecological benefits of eradication (e.g., improvement of endemic species' probability of survival) are difficult to trade-off against social and economic costs due to the lack of a common currency. Local communities may oppose an eradication campaign because of perceived health hazards, inconvenience, financial burdens, religious beliefs, or other cultural reasons. Besides these social challenges, the presence of humans and domestic animals also complicates eradication and biosecurity procedures (measures taken to reduce the probability of unwanted organisms colonizing an island to near zero). For example, houses, garbage-disposal areas, and livestock-feeding areas can provide refuges for certain mammals and therefore can decrease the probability of a successful eradication. Transport of humans and goods to an island increases the probability of inadvertent reintroduction of invasive mammals, and the establishment of permanent quarantine measures is required to minimize the probability of unwanted recolonization after eradication. We recommend a close collaboration between island communities, managers, and social scientists from the inception of an eradication campaign to increase the probability of achieving and maintaining an island permanently free of invasive mammals.

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