Risk assessment for exemptions from ballast water management--the Baltic Sea case study

A temporal assessment of risk of non-indigenous species introduction by ballast water to Canadian coastal waters based on environmental similarity

The environmental similarity scores between source and recipient locations are essential in ballast water risk assessment (BWRA) models used to estimate the potential for non-indigenous species (NIS) introduction, survival, and establishment, and to guide management strategies aiming to minimize biodiversity loss and economic impacts. Previous BWRA models incorporate annual-scale environmental data, which may overlook seasonal variability. In this study, temporal variation in sea surface temperature and salinity data were examined at global ports, and the influence of this variation on environmental distance calculations (and corresponding risk of NIS) was examined for ballast water discharges in Canada by comparing outputs from monthly and annual scale assessments in a BWRA model. Except for some outliers in the Pacific region, the environmental distances based on monthly scale data generally become smaller in all regions, demonstrating that the model using annual decadal average environmental data to inform environmental matching can underestimate risk of NIS survival and establishment in comparison to monthly data. The results of this study suggest future evaluations incorporating the date of ballast water uptake and discharge can provide a more sensitive assessment of risk reflecting seasonal variability compared to an annual average risk model.

Influence of coating type, colour, and deployment timing on biofouling by native and non-native species in a marine renewable energy context

Biofouling on marine renewable energy devices presents engineering challenges for this developing sector, and has implications for the spread of marine non-native species (NNS) in coastal waters. This is particularly true at sites with abundant energy resource, little existing infrastructure, and few established NNS. Device coatings, such as antifouling paints, could reduce the risk of NNS spread. Settlement on coatings of various types and colours, representing those likely to be used on renewable energy devices, was assessed in the Orkney Islands, northern Scotland. Assemblage composition, but not overall biofouling cover, varied initially among different coloured surfaces, although differences decreased over time. Different coating types (an anticorrosive paint, a biocidal paint and a fouling-release coating) differed in biofouling abundance and composition for the full duration of the experiment. NNS were mostly, but not completely, absent from antifouling surfaces. These results can help informing antifouling strategies for the marine renewable energy industry.

Invasiveness risks of naked goby, Gobiosoma bosc, to North Sea transitional waters

In recent decades, gobies have dispersed or introduced from the Ponto-Caspian region of eastern Europe in a westerly direction to North American and western European waters. By contrast, the naked goby, Gobiosoma bosc, is the only known gobiid species to have been introduced in an easterly direction from North American to western Europe. The potential invasiveness of G. bosc was assessed using the Aquatic Species Invasiveness Screening Kit (AS-ISK) for rivers and transitional waters for the western and eastern sides of the North Sea. Using globally-derived thresholds, G. bosc was assessed as low-medium invasiveness risk for both sides of the North Sea under current climate conditions. Under future climate conditions, potential invasiveness will increase for both risk assessment areas. Environmental suitability assessment indicated an increase in environmental suitability for G. bosc on the eastern coastline of the North Sea under climate change scenarios and suitability remained unchanged on the western coastline, reflecting the authors' expectations of invasiveness risk.

Ballast Water Management Strategy to Reduce the Impact of Introductions by Utilizing an Empirical Risk Model

The introduction of non-indigenous aquatic species (NIASs) was identified as one of the major threats to aquatic ecosystems. Shipping is one of the potential invasive pathways for the introduction of marine NIASs, mainly via ballast water, sediments, and ship fouling. In addition, The International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BWM Convention) aims to mitigate the introduction risk of harmful aquatic organisms and pathogens (HAOPs) via ships’ ballast water and sediment. Some of these species can be very harmful and cause loss of biodiversity, adverse environmental consequences, and economic and social impacts. In this study, an empirical model based on the environmental similarity and the vessel characteristics was used to assess the risk associated with the ballast water, for the incoming vessels to the port of Kaohsiung and port of Riga. The priority for port state control (PSC) inspection was established and recommended for better ballast water management.

Determining the bilge water waste risk and management in the Gulf of Antalya by the Monte Carlo method

Bilge water waste poses an environmental risk for humans and marine creatures by causing cancer and developmental disorders due to the toxic substances. This study aims to create a calculation method to calculate the amount of bilge that a ship can produce. The number of ships and the amount of bilge water that they have given the port waste reception facilities in the past years were collected to prevent marine pollution caused by ships in the Gulf of Antalya. The amount of possible future bilge water discharge in the gulf was estimated by using the collected data by linear regression method. The risk distribution of the amount of bilge water that a ship can produce was determined with the data obtained by the Monte Carlo method for the first time in this study. As a result, although the number of ships in the gulf will decrease in number, it is predicted that the amount of bilge water discharge and the needs of a waste receptions facility will increase in the coming years. It is found that the amount of bilge water that a ship can generate will vary in 0.78-3.16 m³, and this data can apply to every ship type. Since the calculation method used in this study can be used for each region with all ship types in calculating the amount of bilge waste a ship can produce, it ensures that the inspections made are more effective. Thus, the management of wastes originating from ships can be effectively and adequately implemented by those who carry out wastes, and marine pollution from ships can be prevented.Implications: Bilge water waste poses an environmental risk for humans and marine creatures by causing cancer and developmental disorders due to the toxic substances. So, It's crucial to manage bilge water waste properly. This study creates a calculation method to calculate the bilge water waste that a ship can produce for applying bilge water waste management. When the studies on the amount of bilge water being discharged into the sea, it is seen that the amount of bilge water that a ship can generate is identified for ships with certain characteristics. However, since the amount of bilge a ship can produce depends on many factors such as engine power, cruise time, and ship's age, these data are insufficient and not usable because it is difficult to predict the type and number of ships in the coming years. This calculation model is simulated most realistically with the calculation to make with the linear regression and Monte Carlo method used for the first time in this study.

A global-scale screening of non-native aquatic organisms to identify potentially invasive species under current and future climate conditions

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium- and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a 'very high risk' of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate 'rapid' management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement.

Exceptions and exemptions under the ballast water management convention - Sustainable alternatives for ballast water management?

The International Convention for the Control and Management of Ships' Ballast Water and Sediments (BWM Convention) aims to mitigate the introduction risk of harmful aquatic organisms and pathogens (HAOP) via ships' ballast water and sediments. The BWM Convention has set regulations for ships to utilise exceptions and exemptions from ballast water management under specific circumstances. This study evaluated local and regional case studies to provide clarity for situations, where ships could be excepted or exempted from ballast water management without risking recipient locations to new introductions of HAOP. Ships may be excepted from ballast water management if all ballasting operations are conducted in the same location (Regulation A-3.5 of the BWM Convention). The same location case study determined whether the entire Vuosaari harbour (Helsinki, Finland) should be considered as the same location based on salinity and composition of HAOP between the two harbour terminals. The Vuosaari harbour case study revealed mismatching occurrences of HAOP between the harbour terminals, supporting the recommendation that exceptions based on the same location concept should be limited to the smallest feasible areas within a harbour. The other case studies evaluated whether ballast water exemptions could be granted for ships using two existing risk assessment (RA) methods (Joint Harmonised Procedure [JHP] and Same Risk Area [SRA]), consistent with Regulation A-4 of the BWM Convention. The JHP method compares salinity and presence of target species (TS) between donor and recipient ports to indicate the introduction risk (high or low) attributed to transferring unmanaged ballast water. The SRA method uses a biophysical model to determine whether HAOP could naturally disperse between ports, regardless of their transportation in ballast water. The results of the JHP case study for the Baltic Sea and North-East Atlantic Ocean determined that over 97% of shipping routes within these regions resulted in a high-risk indication. The one route assessed in the Gulf of Maine, North America also resulted in a high-risk outcome. The SRA assessment resulted in an overall weak connectivity between all ports assessed within the Gulf of the St. Lawrence, indicating that a SRA-based exemption would not be appropriate for the entire study area. In summary, exceptions and exemptions should not be considered as common alternatives for ballast water management. The availability of recent and detailed species occurrence data was considered the most important factor to conduct a successful and reliable RA. SRA models should include biological factors that influence larval dispersal and recruitment potential (e.g., pelagic larval duration, settlement period) to provide a more realistic estimation of natural dispersal.

Oceanographic characteristics of the Adriatic Sea - Support to secondary HAOP spread through natural dispersal

Vessels, specifically ballast water and hull fouling, are a major vector for the introduction of non-indigenous species (NIS) in European seas. The Mediterranean is one of the world's marine regions where their invasion is heaviest. The shallow Adriatic basin is a highly sensitive area that is already experiencing its consequences. The secondary spread of NIS over a wider area through natural dispersion is a complex process that depends on a wide range of oceanographic factors. This work analysed the dataset of the BALMAS project, in whose framework twelve ports in the Adriatic Sea were subjected to a Port Baseline Survey (PBS), to estimate the natural spread of NIS organisms from their port of arrival to the wider Adriatic basin. Its findings indicate that the prevailing water circulation patterns facilitate the natural dispersal of harmful aquatic organisms and pathogens (HAOP).

Introductions and transfers of species by ballast water in the Adriatic Sea

Following the Editorial addressing the BALMAS project, we open the ballast water management special issue for the Adriatic Sea by providing background information on non-indigenous species and the mechanisms (vectors) of transport. Problems allocating introduction mechanisms for various species with certainty are described; in general, key introduction mechanisms are shipping, with ballast water and biofouling as dominant vectors, and aquaculture activities. The dominant mechanisms for introduction may differ through time, between regions and across species. We highlight ballast water as the focus of an international convention to prevent future introductions, reviewing management options and suggesting future research needs. This assessment is not restricted in application to the Adriatic Sea, but is applicable to other coastal waters. Results of such future work may contribute to the experience building phase planned by the International Maritime Organization for a harmonised implementation of the Ballast Water Management Convention.

Vulnerability to bioinvasions: Current status, risk assessment and management of ballast water through a regional approach - the Adriatic Sea

The United Nations recognised the transfer of invasive species across natural barriers as one of the greatest pressures to the world's oceans and seas. The BWM Convention sets the global standards on ballast water management (BWM) requirements, while recognising that regional and local specifics have to be considered for its effective implementation. In the Adriatic Sea cross-border activities were conducted to provide for essential information/data and tools to support a regionally coordinated implementation of the BWM Convention. This special issue contains 18 publications that include results and recommendations from studying the ballast water and management issues through sampling of ballast water on vessels, risk assessment for exemptions and BWM, biological and chemical port baseline surveys and monitoring conducted in ports along the Adriatic Sea coast, oceanographic conditions, ballast water sediment issues and their management in ports, and the implementation options of the BWM Convention through the Adriatic States' environmental law and institutions cooperation. Essential data and tools to support a regional approach in the implementation of the BWM Convention were provided, and are therefore available to the administrations of the Adriatic countries to enable protection of the Adriatic Sea environment, human health property and resources from negative impacts of ballast water being discharged in the area. Data, approaches and tools provided here may be helpful in any other region to support an effective BWM Convention implementation.

Strategy of port baseline surveys (PBS) in the Adriatic Sea

Port baseline surveys (PBS) provide species inventories in and around ports, with a focus on non-indigenous species that may have been introduced by vessels, primarily via ballast water. PBS are an essential tool to support effective management strategies for non-indigenous as well as native harmful aquatic organisms and pathogens (HAOP). This paper describes the methodology of PBS that were conducted in 12 Adriatic ports. The PBS employed existing protocols that were adapted to meet the characteristics of the Adriatic sites. Their results are reported in several papers included in this special issue, each of which is devoted to a specific community. An overview of existing surveys protocols - which provide valuable support to decision-making and to design effective monitoring of non-indigenous species - is also supplied.

Phytoplankton diversity in Adriatic ports: Lessons from the port baseline survey for the management of harmful algal species

An inventory of phytoplankton diversity in 12 Adriatic ports was performed with the port baseline survey. Particular emphasis was put on the detection of harmful aquatic organisms and pathogens (HAOP) because of their negative impact on ecosystem, human health, and the economy. Phytoplanktonic HAOP are identified as species, either native or non-indigenous (NIS), which can trigger harmful algal blooms (HAB). A list of 691 taxa was prepared, and among them 52 were classified as HAB and five as NIS. Records of toxigenic NIS (Pseudo-nitzschia multistriata, Ostreopsis species including O. cf. ovata) indicate that the intrusion of non-native invasive phytoplankton species has already occurred in some Adriatic ports. The seasonal occurrence and abundance of HAOP offers a solid baseline for a monitoring design in ports in order to prevent ballast water uptake and possible expansion of HAOP outside their native region.

Risk assessment for ballast water management - Learning from the Adriatic Sea case study

The ballast water management convention incorporates principles of risk assessment. A new ballast water management risk assessment model was developed to support the implementation of most efficient management measures, which we also present as a flowchart decision support system model. The risk assessment model was tested using data from port baseline surveys where available, and real shipping and ballast water discharges data. The here presented ballast water management risk assessment and possible management options are applicable elsewhere to support and improve complex decision making in the implementation of management requirements according to the ballast water management convention. If needed, the model may easy be adapted to address local specifics in any other region or area.

Ballast water sediment management in ports

In order to estimate the possible effects of existing ballast tank sediment management routine in ports the respective legal framework from different states was examined and the operational modes of selected Adriatic shipyards was analysed. The goal was to determine if the States' administration and ports' management are aware of risks which sediments pose to human health and environment due to possible presence of harmful aquatic organisms and pathogens (HAOP) or high concentrations of heavy metals. The analysis revealed that sediments from ballast tanks after being collected, are subject to the same handling procedure as any other waste material generated during ships' repair and maintenance. In addition, measures preventing sediment drainage into the sea or procedures for analyzing the presence of heavy metals or toxics have not been identified. The paper proposes the procedures ensuring the more advanced level of protection from HAOP and potentially toxic substances from ballast sediment.

Dinoflagellate resting cysts from surface sediments of the Adriatic Ports: Distribution and potential spreading patterns

The ability of microalgae to preserve viable in coastal sediments as resting forms provides a reservoir of biodiversity and a useful tool to determine species spreadings. This study represents the first port baseline survey on dinoflagellate cysts, investigated in nine Adriatic ports during a cross border project. 40 dinoflagellate taxa were detected. The assemblages resulted in all ports dominated by Lingulodinium polyedra and Alexandrium minutum/affine/tamutum group. General separation to the western and eastern side of the Adriatic regarding cysts assemblage composition, partially abundance, was observed. Six taxa were detected as non-indigenous species for the Adriatic. Two taxa are included in the list of harmful aquatic organisms, indicating the potential threat of ballast waters in the Adriatic. Potential spreading of taxa by general circulation and ballast waters, intra- and extra-Adriatic was investigated. The entering in to force of the ballast waters management regulations should enhance prospects to minimize future harmful impacts.

Potential transfer of aquatic organisms via ballast water with a particular focus on harmful and non-indigenous species: A survey from Adriatic ports

Ballast water discharges may cause negative impacts to aquatic ecosystems, human health and economic activities by the introduction of potentially harmful species. Fifty untreated ballast water tanks, ten in each port, were sampled in four Adriatic Italian ports and one Slovenian port. Salinity, temperature and fluorescence were measured on board. Faecal indicator bacteria (FIB), phyto- and zooplankton were qualitatively and quantitatively determined to identify the species assemblage arriving in ballast water. FIB exceeded the convention standard limits in 12% of the sampled tanks. Vibrio cholerae was not detected. The number of viable organisms in the size groups (minimum dimension) <50 and ≥10 μm and ≥50 μm resulted above the abundances required from the Ballast Water Management Convention in 55 and 86% of the samples, respectively. This is not surprising as unmanaged ballast waters were sampled. Some potentially toxic and non-indigenous species were observed in both phyto- and zooplankton assemblages.

The implementation of the ballast water management convention in the Adriatic Sea through States' cooperation: The contribution of environmental law and institutions

The Adriatic Sea, a semi-enclosed and vulnerable environment, deserves special attention regarding the risk of introducing Harmful Aquatic Organisms and Pathogens via ships' ballast water as new species findings occur at an alarming rate. This species introduction vector was addressed with the 2004 International Convention for the Control and Management of Ships' Ballast Water and Sediments, which entered into force in 2017. The efficient implementation of this convention calls for Adriatic States' cooperation on environmental specifics that have not been dealt with neither by national nor by international measures yet. Based on legal and institutional data gathered, and considering the regional maritime traffic and environmental specifics, this paper reveals that the integration of current environmental law commitments as well as a better dialogue between public institutions from shipping and environmental sectors may foster the implementation of ballast water management obligations through appropriate Adriatic States' cooperation.

Contrasting seasonal and spatial distribution of native and invasive Codium seaweed revealed by targeting species-specific eDNA

AIM

Codium fragile, an invasive seaweed, has spread widely during the last century, impacting on local seaweed communities through competition and disturbance. Early detection of C. fragile can help on its control and management. Environmental DNA (eDNA) has proved successful for early detection of aquatic invasive species but its potential use for seaweed remains understudied. We used a species-specific eDNA qPCR approach to investigate the spatial distribution, abundance, and coexistence of the invasive C. fragile and three native Codium species (Codium vermilara, Codium tomentosum, and Codium decorticatum) in the Cantabrian Sea.

LOCATION

Bay of Biscay, Northern Atlantic Coast of the Iberian Peninsula; two ports, a beach and a rocky cliff.

METHODS

We designed species-specific primers in barcoding regions targeting short fragments of the rbcL gene for the invasive Codium species, and the elongation factor Tu (tufA) gene for the native species, to assess their spatial and seasonal distributions using quantitative real-time PCR in samples collected during summer, autumn, and winter.

RESULTS

We found seasonal differences in the presence of the invasive Codium fragile and two of the native Codium species, but did not detect C. decorticatum at any point. Species distribution patterns produced with qPCR targeting species-specific eDNA coincided with the known distribution based on previous conventional sampling, with a seasonal alternance of C. fragile and C. vermilara, and a marked dominance of invasive C. fragile in ports, which are known hotspots for invasive species.

MAIN CONCLUSIONS

Our results demonstrate the utility of using eDNA for early detection and monitoring of invasive seaweed. Native and invasive Codium spp. displayed significant seasonal and spatial differentiation that needs to be taken into account in risk management. Regular monitoring of ports and adjacent areas using eDNA should help to assess the potential expansion of invasive Codium and the need for management interventions to avoid the displacement of native seaweed.

A comparison of impact and risk assessment methods based on the IMO Guidelines and EU invasive alien species risk assessment frameworks

A comparative analysis of two risk assessment (RA) frameworks developed to support the implementation of the international Ballast Water Management Convention (BWMC) and European Regulation on Invasive Alien Species (IAS) was performed. This analysis revealed both differences and similarities between the IMO Risk Assessment Guidelines (IMO, 2007) and EU Regulation supplement on RA of IAS (EU, 2018) in RA approaches, key principles, RA components and categories of IAS impacts recommended for assessment. The results of this analysis were used to produce a common procedure for the evaluation of the bioinvasion risk and impact assessment methods intended to support international, regional and/or national policy on IAS. The procedure includes a scoring scheme to assess compliance with the key principles, RA components and categories of bioinvasion impacts taken into account by the methods. In these methods the categories of impacts on human health and economy are underrepresented comparing with impacts on environment.

Monitoring of sessile and mobile epifauna - Considerations for non-indigenous species

The present study aimed to develop monitoring methods for shallow water sessile and mobile epifauna with the main focus on enhancing the chance of early detection for new non-indigenous species (NIS) invasions. The field sampling was conducted between June and September in 2012, in the Archipelago Sea (Finland). The tested monitoring methods included baited traps that capture organisms and habitat collectors that provide habitat and refuges for organisms, as well as fouling plates. Catch efficiency of a trap/collector was defined as the number of NIS and all species caught, including their abundances. The American collector with oyster shells (habitat collector) caught the highest number of NIS, and their use is recommended in all places, where oyster shells are easily accessible. Sampling of all habitats of interest between 1 and 2 m depth is recommended with at least three habitat collectors per site.

Managing the risk of non-indigenous marine species transfer in Singapore using a study of vessel movement

Shipping is recognized as a major vector for the global transfer of non-indigenous marine species (NIMS). As a major transshipment port, Singapore can minimize the risk of NIMS transfer by implementing pragmatic management strategies, such as using vessel movement information to assess the risk of NIMS transfer. Findings from vessel movement information in a major port terminal in Singapore showed that vessel residence time is short, with >92% of vessels spending seven days or less. There was little variation in vessel residence time to vessel arrival numbers, while the top three last ports of call were found to be from regional ports. Using two key features obtained from vessel movement records, 1) vessel residence time and 2) biogeographic origin of the vessels' last port of call, a simple risk assessment matrix was constructed and applied to assess the level of risk of NIMS transfer by transiting vessels.

Identifying the physical features of marina infrastructure associated with the presence of non-native species in the UK

Marine invasive non-native species (NNS) are one of the greatest threats to global marine biodiversity, causing significant economic and social impacts. Marinas are increasingly recognised as key reservoirs for invasive NNS. They provide submersed artificial habitat that unintentionally supports the establishment of NNS introduced from visiting recreational vessels. While ballast water and shipping vectors have been well documented, the role of recreational vessels in spreading NNS has been relatively poorly studied. Identification of the main physical features found within marinas, which relate to the presence of NNS, is important to inform the development of effective biosecurity measures and prevent further spread. Towards this aim, physical features that could influence the presence of NNS were assessed for marinas throughout the UK in July 2013. Thirty-three marine and brackish NNS have been recorded in UK marinas, and of the 88 marinas studied in detail, 83 contained between 1 and 13 NNS. Significant differences in freshwater input, marina entrance width and seawall length were associated with the presence of NNS. Additionally, questionnaires were distributed to marina managers and recreational vessel owners to understand current biosecurity practices and attitudes to recreational vessel biosecurity. The main barriers to biosecurity compliance were cited as cost and time. Further work identifying easily distinguished features of marinas could be used as a proxy to assess risk of invasion.

Assessing exemptions under the ballast water management convention: preclude the Trojan horse

The International Maritime Organization (IMO) Ballast Water Management Convention (BWMC) is a powerful instrument aimed at reducing spread of harmful aquatic organisms and pathogens (HAOPs). As BWMC is expected to enter into force soon, shipping companies will start seeking exemptions for ballast water management in accordance with BWMC Regulation A-4. However, without scientifically robust risk assessment (RA) and consistent rules, the exemptions may introduce a new form of risk within a convention generally designed to reduce risks. This paper describes an adaptive system for granting exemptions, consisting of six major components: target species selection procedure, port-to-port RA, monitoring, information support, administrative decision and review process. The system is based on key principles defined in the IMO guidelines for RA and is designed to continuously accumulate evolving experience on granting exemptions. The ultimate goal is to contribute to the control of the spread of HAOPs, without placing an unnecessary burden on the shipping industry.

Combining Ballast Water Exchange and Treatment To Maximize Prevention of Species Introductions to Freshwater Ecosystems

The most effective way to manage species transfers is to prevent their introduction via vector regulation. Soon, international ships will be required to meet numeric ballast discharge standards using ballast water treatment (BWT) systems, and ballast water exchange (BWE), currently required by several countries, will be phased out. However, there are concerns that BWT systems may not function reliably in fresh and/or turbid water. A land-based evaluation of simulated "BWE plus BWT" versus "BWT alone" demonstrated potential benefits of combining BWE with BWT for protection of freshwater ecosystems. We conducted ship-based testing to compare the efficacy of "BWE plus BWT" versus "BWT alone" on voyages starting with freshwater ballast. We tested the hypotheses that there is an additional effect of "BWE plus BWT" compared to "BWT alone" on the reduction of plankton, and that taxa remaining after "BWE plus BWT" will be marine (low risk for establishment at freshwater recipient ports). Our study found that BWE has significant additional effect on the reduction of plankton, and this effect increases with initial abundance. As per expectations, "BWT alone" tanks contained higher risk freshwater or euryhaline taxa at discharge, while "BWE plus BWT" tanks contained mostly lower risk marine taxa unlikely to survive in recipient freshwater ecosystems.

Evaluating the potential of ecological niche modelling as a component in marine non-indigenous species risk assessments

Marine biological invasions have increased with the development of global trading, causing the homogenization of communities and the decline of biodiversity. A main vector is ballast water exchange from shipping. This study evaluates the use of ecological niche modelling (ENM) to predict the spread of 18 non-indigenous species (NIS) along shipping routes and their potential habitat suitability (hot/cold spots) in the Baltic Sea and Northeast Atlantic. Results show that, contrary to current risk assessment methods, temperature and sea ice concentration determine habitat suitability for 61% of species, rather than salinity (11%). We show high habitat suitability for NIS in the Skagerrak and Kattegat, a transitional area for NIS entering or leaving the Baltic Sea. As many cases of NIS introduction in the marine environment are associated with shipping pathways, we explore how ENM can be used to provide valuable information on the potential spread of NIS for ballast water risk assessment.