Non-indigenous Species Richness Research Articles

The influence of recreational boat traffic in the introduction of non-indigenous fouling species in three Ligurian marinas (Mediterranean Sea, Italy)

The role of navigation in transporting and introducing non-indigenous species (NIS) in ports is globally acknowledged, and maritime traffic is correlated with increasing NIS introductions. On the other hand, different types of vessels can occur in a port (e.g., for commercial or recreational purposes) and the success of a NIS in a new area also depends on several chemical-physical and biotic conditions of the arrival port.In this context, a study was conducted in 2020 in three marinas at Sanremo (Ligurian Sea, Italy) with the aim to assess if boat traffic influences the presence of NIS in marine fouling communities.Samples were collected from docks and pontoons with a hand-held rigid net in the marinas of Sanremo (Porto Sole, characterized by international recreational boat traffic; and Porto Vecchio, hosting only local fishing boats), as well as in Ospedaletti, a nearly finished, abandoned and unused marina. Overall, 47 species (including 9 NIS), 45 (8 NIS) and 86 (2 NIS) were collected in Porto Sole, Porto Vecchio and Ospedaletti, respectively. Number and proportion of NIS were significantly lower in the unused marina of Ospedaletti in comparison with the other two ones, which in turn exhibited similar sessile assemblages and comparable NIS richness. The peculiarity of Ospedaletti fouling community, despite the geographical proximity and similar habitat conditions of the other marinas, highlights the role of boating traffic in facilitating NIS settlement, while the sole presence of artificial substrates is not sufficient to promote NIS introduction. This site could provide opportunities for experimenting novel NIS management measures.

Recent invasion of Ponto-Caspian amphipods in the Masurian Lakeland associated with human leisure activities

Non-indigenous species (NIS) contribute to the decrease of native species’ diversity on a local and global scale. One of Europe’s most significant donors of freshwater invasions is the Ponto-Caspian Region. Following the construction of artificial canals connecting isolated waterbodies and the resulting heavy boat traffic, the Ponto-Caspian Amphipoda started to spread in Europe. Four amphipod species: Dikerogammarus haemobaphes, Dikerogammarus villosus, Pontogammarus robustoides and Chaetogammarus ischnus have invaded the Masurian Lakeland (North-eastern Poland). Based on literature and our data, we studied their distribution in 22 lakes in the region during the years 2001–2016. We analysed their distribution against several water quality parameters and levels of anthropogenic pressure. Our results also present the first records of two new invaders, D. villosus and C. ischnus, in the studied area. We show that the relative abundance and frequency of these two species rapidly increase and, simultaneously, the populations of the earlier invaders, i.e. D. haemobaphes and P. robustoides, decrease. The native species – Gammarus lacustris – seems to be negatively affected by NIS richness, as well as by the proximity of towns. The spread of NIS in the lakes appears to be facilitated by boating and the lower complexity of the shoreline. Our study shows how anthropogenic pressure, especially tourism, can facilitate bioinvasion, jeopardising native biodiversity unless appropriate regulations are implemented.

Estuarine versus coastal marinas: Influence of the habitat on the settlement of non-indigenous peracarids on the polychaete Sabella spallanzanii (Gmelin, 1791)

Recreational marinas are key points for the introduction and secondary spread of non-indigenous species (NIS). However, little is known about the influence of the habitat surrounding the marina on NIS communities. To explore this issue, we compared peracarid assemblages associated to the widespread ecosystem engineer Sabella spallanzanii in lower estuarine marinas (with oceanic salinity) and coastal marinas of the south of the Iberian Peninsula. Sabella spallanzanii hosted a total of 23 species, 7 of them NIS. While NIS richness was similar between marinas located in estuaries and coastal habitats, NIS abundance was significantly higher in estuarine marinas. The NIS community structure was influenced by both the marina itself and the surrounding habitat. These results suggest that lower estuarine conditions promote NIS abundance in marinas, increasing potential invasion risks. This supports prioritization of estuarine marinas in NIS monitoring programs and the suitability of S. spallanzanii as a bioinvasion monitoring tool.

Multi-indicator ‘state space’ approach to assessing changes in shallow urban reef ecosystem health

Tracking changes in ecosystem health is an important objective for environmental managers, but is often limited by an understanding of what constitutes a “healthy” system and how to aggregate a range of health indicators into a single meaningful metric. We used a multi-indicator ‘state space’ approach to quantify changes over 13 years in reef ecosystem health in an urban area that has undergone intense housing development. Based on nine health indicators (macroalgal canopy length and biomass, macroalgal canopy and habitat functional diversity, mobile and predatory invertebrate density and size, total species and non-indigenous species richness), we found that the overall health of the reef community declined at five of the ten study sites. This decline was associated with a large collapse in the gastropod community, a shortening of macroalgal canopies and an increase in the number of non-indigenous species. While the cause of this decline and mechanisms responsible are not fully understood, the decline correlated with an increase in sediment cover on the reefs and warming ocean temperatures over the monitoring period. The proposed approach provides an objective and multifaceted quantitative assessment of ecosystem health that can be easily interpreted and communicated. These methods could be adapted to other ecosystem types to inform management decisions regarding future monitoring, conservation and restoration priorities to achieve greater ecosystem health.

Facilitation of non-indigenous ascidian by marine eco-engineering interventions at an urban site

Marine artificial structures often support lower native species diversity and more non-indigenous species (NIS), but adding complex habitat and using bioreceptive materials have the potential to mitigate these impacts. Here, the interacting effects of structural complexity (flat, complex with pits) and concrete mixture (standard, or with oyster shell or vermiculite aggregate) on recruitment were assessed at two intertidal levels at an urban site. Complex tiles had less green algal cover, oyster shell mixtures had less brown (Ralfsia sp.) algal cover. At a low tidal elevation, the non-indigenous ascidian Styela plicata dominated complex tiles. Additionally, mixtures with oyster shell supported higher total cover of sessile species, and a higher cover of S. plicata. There were no effects of complexity or mixture on biofilm communities and native and NIS richness. Overall, these results suggest that habitat complexity and some bioreceptive materials may facilitate colonisation by a dominant invertebrate invader on artificial structures.

Rapid recovery of native habitat-builders following physical disturbance on pier pilings offsets colonization of cryptogenic and non-indigenous species in a Chilean port

Examining the effects of disturbances within marine urban communities can shed light on their assembly rules and invasion processes. The effects of physical disturbance, through the removal of dominant native habitat-builders, were investigated in the recolonization of disturbed patches and colonization of plates on pier pilings, in a Chilean port. On pilings, disturbance substantially affected community structure after 3 months, although it slowly converged across treatments after 10 months. On plates, cryptogenic and non-indigenous species richness increased with removal severity, which was not observed in natives. Opportunistic taxa took advantage of colonizing at an early successional stage, illustrating a competition-colonization trade-off, although indirect effects might be at play (e.g. trophic competition or selective predation). Recovery of the habitat-builders then occurred at the expense of cryptogenic and non-indigenous taxa. Whether natives could continue winning against increasing propagule and colonization pressures in marine urban habitats deserves further attention. The interactions between disturbance and biological invasions herein experimentally shown in situ contribute to our understanding of multiple changes imposed by marine urbanization in a growing propagule transport network.

Alien species spreading via biofouling on recreational vessels in the Mediterranean Sea

AbstractDespite the Mediterranean being both a hotspot for recreational boating and for non‐indigenous species (NIS), no data currently exists on the recreational boating sector's contribution to the spread of NIS in this Sea.To improve the basis for management decisions, a wide‐scale sampling study on the biofouling communities of recreational vessels and marinas was undertaken. Specifically, we surveyed over 600 boat owners and sampled the same boat hulls for NIS in 25 marinas across the Mediterranean, from France to Cyprus, to determine which factors (i.e. boat characteristics, travel behaviour, home marina) are associated with higher NIS richness on boat hulls.Among the surveyed boats, we found recreational vessels to travel considerably, averaging 67 travel days and 7.5 visited marinas per annum. This results in a high potential for spreading NIS, especially as 71% of sampled vessels host at least one (and up to 11) NIS. Boats with high NIS richness strongly correlate with home marinas with high NIS richness. Over half of the vessels were carriers of NIS which were not yet present in the marinas they were visiting. The presence of biofouling in niche areas of the hull (i.e. in the cavities and metallic parts) emerges as the best predictor for NIS richness on boats, along with longer times since their last cleaning and antifouling applications. Interestingly, colonization of NIS occurred rapidly, even on boats that had recently had their hulls cleaned professionally.Synthesis and applications. We demonstrate that recreational boating has a very high capacity for the spread of non‐indigenous species (NIS) in the Mediterranean, due to both high NIS richness on boats and extensive travel. To counteract the spread of NIS, routine monitoring for new NIS needs to be established for both marinas and vessels, along with frequent pontoon cleaning. Additionally, policy should require preliminary screenings for incoming vessels from new countries, especially those emanating from high‐risk marinas. The niche areas of the boat hulls should be checked first for biofouling, which was the best predictor for NIS richness since they often go overlooked with in‐water cleanings are rarely have antifouling applied to them.

Invasions in Marine Communities: Contrasting Species Richness and Community Composition Across Habitats and Salinity

While many studies of non-native species have examined either soft-bottom or hard-bottom marine communities, including artificial structures at docks and marinas, formal comparisons across these habitat types are rare. The number of non-indigenous species (NIS) may differ among habitats, due to differences in species delivery (trade history) and susceptibility to invasions. In this study, we quantitatively compared NIS to native species richness and distribution and examined community similarity across hard-bottom and soft-sediment habitats in San Francisco Bay, California (USA). Benthic invertebrates were sampled using settlement panels (hard-bottom habitats) and sediment grabs (soft-bottom habitats) in 13 paired sites, including eight in higher salinity areas and five in lower salinity areas during 2 years. Mean NIS richness was greatest in hard-bottom habitat at high salinity, being significantly higher than each (a) native species at high salinity and (b) NIS richness at low salinity. In contrast, mean NIS richness in soft-bottom communities was not significantly different from native species richness in either high- or low-salinity waters, nor was there a difference in NIS richness between salinities. For hard-bottom communities, NIS represented an average of 79% of total species richness per sample at high salinity and 78% at low salinity, whereas the comparable values for soft bottom were 46 and 60%, respectively. On average, NIS occurred at a significantly higher frequency (percent of samples) than native species for hard-bottom habitats at both salinities, but this was not the case for soft-bottom habitats. Finally, NIS contributed significantly to the existing community structure (dissimilarity) across habitat types and salinities. Our results show that NIS richness and occurrence frequency is highest in hard-bottom and high-salinity habitat for this Bay but also that NIS contribute strongly to species richness and community structure across each habitat evaluated.

Influence of seawater temperature and shipping on the spread and establishment of marine fouling species

This study assessed the influence of summer seawater temperature and shipping on the introduction, establishment, and spread of nonindigenous fouling species on both local and regional scales in coastal regions of the USA. Using photographic surveys of 80 marinas on the east and west coasts of the USA, we defined thermal niches and ranges of summer sea surface temperature (SSST) for 27 abundant fouling species. We calculated percent cover of all abundant tunicates and bryozoans across sites and correlated species richness with water temperature and cargo shipping volume in each region. We quantified the relative importance of cargo shipping, seawater temperature, and distance between sites using Jaccard similarity between paired sites. Native species richness was positively correlated with SSST, while nonindigenous species (NIS) richness displayed a parabolic relationship with a peak at 20 °C. Temperature and cargo shipping traffic explained 53 % of variability in NIS richness, and only temperature was correlated with similarity between sites. We also found no link between similarity and distance between sites, and site–site comparisons showed no effect of NIS on native species richness on the scale of this study. It appears that cargo shipping may play a regional role in introduction of new species, but on local scales NIS distributions are more haphazard, possibly driven by local recreational boat traffic and associated larval dispersal or by other vectors affecting the local spread of these species. Our study demonstrates the importance of seawater temperature in allowing spread of NIS and influencing similarity between sites and regions.

Invasion history and vector dynamics in coastal marine ecosystems: A North American perspective

The known extent of biological invasions exhibits strong variation with respect to space, time, taxonomic group, and vector. Using a synthesis of nonindigenous species (NIS) occurrences in North America, we characterized the invasion history for coastal marine ecosystems by invertebrates and algae through 2010, to evaluate variation and existing patterns at a continental scale. This study updates a previous analysis of invasions for the same taxonomic groups in North America, providing a first assessment of changes in the last 11 year period (2000–2010). Overall, we documented 450 marine and estuarine NIS that are considered to have established populations in tidal waters of North America, representing a 51% increase in NIS richness compared to the earlier analysis. Of the 152 species added, 71 species (47%) have first documented records since the year 1999, and 81 species (53%) were additions attributed to earlier time periods due to recent reports and further analysis. Across all time periods, taxonomic groups with the largest contribution were Crustaceans (112 species) and Molluscs (80 species), together providing 43% of the total species richness for North America. Species richness was unevenly distributed among coasts, with most documented on the Pacific Coast (310 species) and fewer on the Atlantic Coast (189 species) and Gulf Coast (88 species). Commercial ships have contributed between (a) 44–78% of the initial (primary) invasions of all nonindigenous species to North America and (b) 52–82% of NIS in the last 30-year time interval, being driven by transfers associated with ballast water and hull biofouling. Importantly, invasion dynamics are a shifting landscape, where the past may not predict the future, especially with emerging trade patterns and global to local environmental changes. Thus, effective management to reduce future invasions requires a dynamic and multi-vector approach, instead of single vector strategies based on past history alone.

Spatial distribution of marine invasive species: environmental, demographic and vector drivers

AbstractAimThe introduction of potentially invasive species remains a global threat to biodiversity and ecosystem services. The spatial distribution of introduced species can provide insight into present and historical vectors of invasion. Here, we aim to investigate the influence of environmental, demographic and vector variables on the spatial distribution of non‐indigenous species (NIS) in coastal marine ecosystems.LocationCoastal British Columbia, Canada.MethodsWe used subtidal settlement plates to sample NIS richness at 81 sites. Spatial patterns for seventeen environmental, population, and vector variables were created using a Geographic Information System (GIS). We used multiple regression with model selection and spatial autocorrelation to define a statistical model that best explained the spatial distribution of NIS.ResultsFour variables, salinity, human population density, port arrivals and marina propulsiveness (probability of boater travel from home marina), best explained the observed spatial distribution of subtidal NIS. Aquaculture, an original global introduction pathway, did not significantly explain the contemporary distribution of NIS. Results suggest that recreational boating is the most probable pathway of fouling NIS spread in this region, driving their current distribution. Spatial autocorrelation was significant for environmental, demographic, and aquaculture variables. However, marina propulsiveness and attractiveness were not autocorrelated, suggesting that boater behaviour varies on a finer scale.Main conclusionsA simple model using a combination of vector, demographic, and environmental characteristics can explain 43.6% of the variation in the spatial distribution of NIS. Our study provides further evidence that recreational boating is a significant pathway for the contemporary spread of NIS in marine environments. With projected increases in human population, we expect a continued rise in introduction rates and spread in this region and elsewhere in the world.

International arrivals: widespread bioinvasions in European Seas

The European Union lacks a comprehensive framework to address the threats posed by the introduction and spread of marine non-indigenous species (NIS). Current efforts are fragmented and suffer substantial gaps in coverage. In this paper we identify and discuss issues relating to the assessment of spatial and temporal patterns of introductions in European Seas (ES), based on a scientifically validated information system of aquatic non-indigenous and cryptogenic species, AquaNIS. While recognizing the limitations of the existing data, we extract information that can be used to assess the relative risk of introductions for different taxonomic groups, geographic regions and likely vectors. The dataset comprises 879 multicellular NIS. We applied a country-based approach to assess patterns of NIS richness in ES, and identify the principal introduction routes and vectors, the most widespread NIS and their spatial and temporal spread patterns. Between 1970 and 2013, the number of recorded NIS has grown by 86, 173 and 204% in the Baltic, Western European margin and the Mediterranean, respectively; 52 of the 879 NIS were recorded in 10 or more countries, and 25 NIS first recorded in European seas since 1990 have since been reported in five or more countries. Our results highlight the ever-rising role of shipping (commercial and recreational) as a vector for the widespread and recently spread NIS. The Suez Canal, a corridor unique to the Mediterranean, is responsible for the increased introduction of new thermophilic NIS into this warming sea. The 2020 goal of the EU Biodiversity Strategy concerning marine Invasive Alien Species may not be fully attainable. The setting of a new target date should be accompanied by scientifically robust, sensible and pragmatic plans to minimize introductions of marine NIS and to study those present.

Recreational boats as potential vectors of marine organisms at an invasion hotspot

With more than 200 aquatic nonindigenous species (NIS), San Francisco Bay (California, USA) is among the world's most invaded harbors. Hard-substratum benthic (biofouling) organisms, which dominate NIS richness, have arrived primarily as a result of shipping and aquaculture activity over past centuries. To date there has been no assessment of the leisure craft vector in the Bay. We aimed to characterize (1) biofouling on boats' submerged surfaces and (2) boater behavior likely to affect the risk of NIS transfers. We used an underwater pole-cam, specimen collections, and a boater questionnaire to quantify the extent and composition of biofouling on recreational boats and to eval- uate boater behavior at a subset of the Bay's marinas. Several NIS, already established within the Bay, were recorded from vessel hulls, including the bryozoans Bugula neritina, Membranipora chesa- peakensis and Watersipora sp., the ascidians Botrylloides violaceus, Styela clava and Ciona intesti- nalis, the polychaete Ficopomatus enigmaticus, and the sponge Clathria prolifera. Only 16% of ques- tionnaire respondents had traveled to sites outside the Bay in the previous 12 mo. Frequency of hull painting and cleaning varied substantially, but we did not find strong patterns of biofouling extent associated with hull husbandry or boat usage. The potential for within-Bay and coastwise regional spread of NIS is high, and recreational boats probably interact in close proximity to other vectors (e.g. commercial ships), causing a ratchet effect of vector events; however, there remains a gap in under- standing the levels and condition of biofouling on transient boats. Transient vessels from San Fran- cisco Bay and other West Coast sites should be the focus of future studies to evaluate the extent to which organisms are being transferred among bays and how vector management could be applied to prevent NIS transfers and impacts.

Non-indigenous marine macroalgae in native communities: a case study in the British Isles

It has traditionally been considered that areas with high natural species richness are likely to be more resistant to non-indigenous species than those with lower numbers of species. However, this theory has been the subject of a debate over the last decade, since some studies have shown the opposite trend. In the present study, a macroalgal survey was carried out at 24 localities in Northern Ireland and southern England, using a quadrat approach in the lower littoral. The two opposing hypotheses were tested (negative versus positive relationship between native and non-indigenous species richness) in this marine environment. The effect of the presence of ‘impacts’, potential sources of disturbance and species introduction (e.g. marina, harbour or aquaculture), was also tested. A positive relationship was found between the number of non-indigenous species and the native species richness at the three different scales tested (quadrats, sites and localities). At no scale did a richer native assemblage appear to restrict the establishment of introduced species. The analyses revealed greater species richness and different community composition, as well as more non-indigenous species, in southern England relative to Northern Ireland. The presence of the considered impacts had an effect on the community composition and species richness in southern England but not in Northern Ireland. Such impacts had no effect on the non-indigenous species richness in either area.

Patterns of nonindigenous herpetofaunal richness and biotic homogenization among Florida counties

Recent studies of geographic patterns of nonindigenous species richness suggest that a few key biogeographic and anthropogenic factors explain much of the variation in the richness of established species. It remains unknown, however, if the factors identified in these studies are taxon- and scale-specific or if general rules apply broadly across taxa and spatial scales. To address this issue, I used multiple regression analysis to identify factors that contribute significantly to variation in nonindigenous herpetofaunal richness at a relatively small spatial scale, the county level, in Florida, USA. Additionally, I used the Jaccard similarity index to determine if nonindigenous species affect the biotic similarity of the herpetofaunas of Floridian counties. In the regression analysis, county latitude strongly and negatively affected nonindigenous herpetofaunal richness, explaining approximately two-thirds of the variation in this variable. To a smaller degree, human population and university presence both related positively with nonindigenous herpetofaunal richness. Several other variables, including county land area, were not significantly related to nonindigenous herpetofaunal richness. The consistent importance of human population to nonindigenous species richness in this and past studies suggests that the influence of anthropogenic factors may be universal and are as or more important than the natural biogeographic factors that generally relate with native species richness. No evidence of overall homogenization was found based on Jaccard index values. However, a significant relationship between homogenization scores and distance between counties suggests that the effect of nonindigenous herpetofaunal richness on the similarity of county biotas is scale-dependent, such that adjacent counties tend to experience homogenization, while distant counties tend to experience differentiation as a result of the presence of nonindigenous herpetofauna. The results of this and similar studies may be useful in predicting the introduction and spread of nonindigenous species and in evaluating the effects of such introductions on native biodiversity.

Are invasive species most successful in habitats of low native species richness across European brackish water seas?

European brackish water seas (Baltic Sea, Black Sea and Sea of Azov, Caspian Sea) are subject to intense invasion of non-indigenous species (NIS). In these seas, salinity is the most important range limiting factor and native species seem to reach a minimum species richness at intermediate salinities. This trend, revealed by Remane in 1934 and later on confirmed by many other scientists, was compared to the salinity range of already established NIS in the European brackish water seas. It turned out that most NIS are well adapted to the salinities holding lowest native species richness, already in their native area, and that NIS richness maximum in brackish water seas occurs in the salinity intervals of native species richness minimum. A predictable pattern in the salinity range of NIS can be used as a tool in initial risk assessment of future invasions in brackish water seas, especially when mapping highly potential donor and recipient areas. A product of empty niches, suitable environmental conditions, and availability of proper vectors might be the most effective predictor for the invasibility of brackish water areas.