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Ships' ballast water and sediments are vectors that contribute to the unintentional spread of aquatic non-native species globally. Ballast water management, as well as commissioning testing of ballast water management systems and compliance monitoring under the regulations of the International Maritime Organization (IMO) aimat minimizing the unwanted spread of organisms. This study compiles data for treated ballast water samples collected and analyzed from 228 ships during 2017-2023. The samples were collected from the ballast discharge line or directly from the ballast tank for enumeration of living organism concentrations in the categories of =50µm and <50 to =10µm -sized organisms, as well as indicator microbes in comparison to the ballast water performance standard of the IMO (Regulation D-2). In addition, several ship-specific factors were examined to infer potential factors affecting compliance rates. Nearly all ships were compliant with the ballast water performance standard for indicatormicrobes and <50 to =10µm -sized organisms, whereas almost half of all samples exceeded the limit of ten viable organisms m-3 for the =50µm -sized organisms. Compliance testing results did not differ significantly between sampling years, indicating that compliance rate did not change through time. The rate of compliance was higher for commissioning testing than compliance testing. Clear ship-or system-specific factors that lead to compliance or non-compliance were not detected, even though type of ballast watermanagement system, filter mesh size associated with the systemand source of ballast water affected compliance significantly either for the samples taken from the discharge line, or ballast tank. As compliance did not improve significantly over time, compliance testing of ships' ballast water should be undertaken to ensure that the systems remain operational after commissioning and ships meet requirements of the D-2 standard. Furthermore, the study outcomes promote further research on the efficiency of filter mesh sizes and different filtration units associated with ballast water management systems, to improve mechanical removal of larger organisms. Finally, as several ships exceeded the compliance limit by hundreds or thousands of living organisms, technological advancements and operational measures may be needed to improve the overall reliability of ballast water management. [ABSTRACT FROM AUTHOR]

A number of ballast water compliance monitoring devices (CMDs) have been made commercially available to verify the efficacy of ballast water management systems by quantifying the living organisms for both plankton size classes (≥50 μm and ≥10–<50 μm). This study aimed to examine whether new CMDs can provide a reliable indication of compliance regarding Regulation D-2 and to evaluate their performance for indicative analysis of organisms by assessing their accuracy (comparison to microscopy) and precision (comparison within measurement). Challenge fresh water samples were collected in four locations of Lake Ontario, Canada, whereas marine challenge water samples were collected around the Bay of Fundy, New Brunswick, Canada. Ballast water samples were collected from ships visiting several ports across Canada. Overall, accuracy was higher (>80%) in estimating organisms from prepared-challenge water (Ballast Eye and BallastWISE) than from ballast water samples (>70%) (B-QUA only). The sensitivity ranged from 50 to 100% for the ≥50 μm organism size class, whereas for the ≥10–<50 μm organism size class, it was higher for freshwater samples (>75%) than for marine samples (>50%). The performance of CMDs should be assessed under real-world conditions for a better understanding and to improve their use. [ABSTRACT FROM AUTHOR]

A recent model demonstrated that the adenosine triphosphate (ATP) content of spherical aquatic organisms with a 10 to 50 μm diameter is between 0.16 and 19.9 pg cell−1. Here, the model is validated by comparing microscopy-based counts with ATP concentrations from a commercial ATP kit. The measured ATP content of both freshwater and marine organisms 10 to 50 μm size range falls in the 0.16 to 19.9 pg cell−1 model range. On average, freshwater organisms contain 0.33 pg ATP cell−1, have a spherical equivalent diameter (SED) of 13 μm, while marine organisms have 0.89 pg ATP cell−1 and a SED of 18 μm. In addition, their 13 to 18 μm size is within the 10 to 50 μm ballast water size range and in agreement with the 15 μm mean SED of a coastal plankton size-distribution model. This study concludes that the ATP-model is reliable, emphasizing the need for caution when converting three-dimensional biomass proxies into linear cell concentrations. • A recent model demonstrated that the ATP content of spherical aquatic organisms with a 10 to 50 μm diameter is between 0.16 to 19.9 pg cell-1. The model was validated by comparing microscopy-based counts with ATP concentrations from a commercial ATP kit. • On average, freshwater organisms contain 0.33 pg ATP cell-1, have a spherical equivalent diameter (SED) of 13 μm, while marine organisms have 0.89 pg ATP cell-1 and a sed of 18 μm. • The ATP content of both marine and freshwater organisms falls in the 0.16 to 19.9 pg cell-1 model range. Their 13 to 18 μm SED is within the 10 to 50 μm ballast water size range and in agreement with the average of 15 μm SED of a coastal plankton size-distribution model. • This study concludes that the ATP-model is reliable, emphasizing the need for caution when converting three-dimensional biomass proxies into linear cell concentrations. [ABSTRACT FROM AUTHOR]

Chlorine efficacy as a biocide for ballast water treatment was investigated under cold- and warm-water temperatures across winter and summer seasons. Freshwater phytoplankton samples were collected and acclimated under in situ environmental conditions ranging from 2 to 22 °C. Samples were exposed to seven chlorine treatments (from 0.02 to 5.0 ppm), in addition to a control (0.0 ppm). Free-chlorine concentrations, phytoplankton abundance, and photosynthetic efficiency were measured up to 48 h following treatment. After 4 h of treatment at concentrations less than 0.22 ppm, phytoplankton densities were reduced by more than 50%, without cell resurgence. Similar reduction was recorded immediately after exposure when chlorine concentrations were higher than 3.0 ppm. After 8 h, free chlorine neared 0.0 ppm for initial chlorine concentrations below 1.2 ppm, irrespective of temperature regime. Winter phytoplankton exhibited slightly lower mortality to chlorine exposure regardless of the temperature, although they also exhibited lower photosynthetic efficiency. Despite a general absence of significant effect of temperature on the chlorine decay, our results suggest that higher doses of chlorine or longer exposure times may be required during winter to achieve full treatment effect. Tests at large scales are needed to further confirm these findings. [ABSTRACT FROM AUTHOR]

1. Species invasions depend on the abundance and rate at which organisms are introduced to new localities, known as propagule pressure. Due to the challenges of measuring propagule pressure, proxy variables are often used; however, untested proxy variables may obscure the role of propagule pressure vs. ecological factors that facilitate invasion, leading to uncertainty about the invasion process and confoundingmanagement response. 2. To generate absolute estimates of propagule pressure and facilitate meaningful comparison among pathways of species introduction, we extend proxy variables by combining ecological and global trade data with hierarchical statistical models. We derive absolute propagule pressure with probability distribution functions (propagule size: the probability of introducing n propagules per event; and overall propagule pressure: the probability of introducing n propagules per year) and, based on these projections, evaluate the performance of ballast water volume (m3) as a common proxy variable. 3. Hindcast accuracy of ballast water volume was low but strongly scale-dependent, exhibiting poor accuracy (R2 = 0058) at small scales and onlymarginal accuracy at large scales (overallR2 = 0169).As a result, conclusions about propagule pressure are likely to be biased based on the ballast volume proxy, as may be conclusions about species invasion when ballast water volume has been used. Irrespective of geographic pathway, estimated propagule sizes demonstrated extreme leptokurtosis and long right tails, withmaximum values between 131-fold and 2966-fold greater than median values. These characteristics signify a subset of introduction events involving extreme propagule abundance that may provide opportunity to overcome Allee thresholds or marginal environmental conditions. 4. Developing meaningful propagule supply functions is critical to resolve the role of propagule pressure within the invasion process and test hypotheses about species colonization at landscape scales. By joining absolute propagule pressure with existing theory about species extinction, the expected ecological outcome of environmental policy tomanage propagule pressure can be estimated within a statistical framework. [ABSTRACT FROM AUTHOR]

To minimize the global transfer of harmful aquatic organisms and pathogens, the International Maritime Organization (IMO) has introduced the standard in Regulation D-2 to limit the number of viable organisms in ballast water discharged by ships. To meet the standard, many ships are installing ballast water management systems. Concurrently, regulators are looking for indicative analysis devices able to assess compliance with Regulation D-2, producing rapid, accurate and reliable results while being easy to operate. The purpose of this research is to compare four indicative analysis devices against detailed microscopy for measuring the size class of organisms ≥10 to <50 μm in minimum dimension (e.g., phytoplankton, including autotrophs, heterotrophs or mixotrophs), using field and laboratory tests. Comparisons were conducted on (treated) ballast water discharge samples collected across Canada during three consecutive years (2017–2019). During seven tests in 2019, paired ballast water uptake samples were also obtained, facilitating measurements before and after treatment was applied. Indicative analysis devices also were challenged with natural environmental samples containing different organism abundance levels, ranging from low (nominally <10 cells mL−1) to high (nominally >150 cells mL−1) during laboratory tests. While the indicative analysis devices examined during this research produced numeric estimates having weak correlations with the standard reference method, categorical outcomes (above/below the D-2 standard) had high agreement (89% or better) when assessing ballast water samples, but lower agreement (67% or poorer) during laboratory tests. There was a relatively high rate of false negative results measured by all devices during laboratory tests. Results provided by indicative analysis devices had higher uncertainty when organism abundances in ballast samples are below and close to the D-2 standards. • Indicative devices had weak correlation with microscopy based on numeric estimates. • Categorical outcomes had high agreement for ballast water samples. • Uncertainty was higher for abundances below and close to the D-2 standard. [ABSTRACT FROM AUTHOR]

Ballast water is a leading pathway for the global introduction of aquatic nonindigenous species. Most international ships are expected to install ballast water management systems (BWMS) by 2024 to treat ballast water before release. This study examines if ballast water discharges managed by BWMS are meeting standards for organisms ≥50 μm in minimum dimension (i.e., <10 organisms per m3; typically zooplankton). Representative samples of ballast water were collected from 29 ships (using 14 different BWMS) arriving to Canada during 2017–2018. Fourteen samples (48 %) had zooplankton concentrations clearly exceeding the standard (ranging from 18 to 3822 organisms per m3). Nonetheless, compared to earlier management strategies, BWMS appear to reduce the frequency of high-risk introduction events. BWMS filter mesh size was an important predictor of zooplankton concentration following treatment. Greater rates of compliance may be achieved as ship crews gain experience with operation and maintenance of BWMS. • Ballast water is a main pathway for introduction of aquatic nonindigenous species. • Ships are using new ballast water management systems (BWMS) to treat ballast water. • Nearly 50 % of ballast water samples exceed treatment standards after using BWMS. • However, the frequency of high-risk introductions has been dramatically reduced. [ABSTRACT FROM AUTHOR]

ABSTRACT The abundances and diversity of dinoflagellate cysts (including non-indigenous or harmful species) in ballast sediments were examined for the east and west coasts and the Great Lakes, to assess the potential invasion risk for these organisms and to determine similarity across regions., In total, 147 ships were sampled, distributed among three categories: (1) transoceanic, with mandatory ballast water exchange (BWE); (2) coastal with BWE; and (3) coastal without BWE. Factors that could account for variability in results were examined including ship routes, BWE, ballast water age and sediment volume in ballast tanks., The pattern of potential invasion risk differs according to the region examined. The east coast had greater concentrations of viable cysts per tank, particularly for coastal ships (with a maximum close to 2 × 106 cysts per tank in coastal exchanged ships compared with 1 × 105 for the west coast). When considering viable cysts g-1 dry sediment, maximum concentrations were found in unexchanged coastal ships from the east coast (28 cysts g-1 compared with 5 for the west coast), but these ships contained less sediment, decreasing the overall abundance of cysts per tank. These results are in the lower range of values reported for Scotland or Australia, which reached a maximum of 2.3 × 104 cysts cm−3 of sediment., Ballast water exchange had a different influence according to the region: on the east coast, the invasion risk was reduced by BWE while it had no significant effect in the other two regions. Ballast water age and sediment volume were also different among regions, but they were not clearly related with cyst concentrations in ballast tanks., Future management of ballast sediment should take into consideration these regional differences in order to reduce the introduction of dinoflagellate NIS that threaten the conservation of coastal habitats through reduction of native diversity., Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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With the entry into force of the International Maritime Organization's International Ballast Water Management Convention in September 2017, ships have begun to install and operate onboard ballast water management systems (BWMS) to reduce the number of live organisms in ballast water. Scientific methods were developed to assess the effectiveness of BWMS at reducing the number of live organisms in ballast water. However, detecting low organism concentrations in treated ballast water is challenging when considering the small sample volume (6 mL) analyzed for organisms in the 10–50 μm size class. The volume analyzed can be increased by concentrating the sample prior to analysis, but it is important to assess the effects of the sample concentration method due to potential cell loss experienced during the concentration step. Therefore, laboratory experiments were conducted to assess the effects of a gravity filtration method to concentrate samples to a factor of 40:1. Experiments were conducted for both low and high organism abundances. For unpreserved samples at low organism abundances (∼10 cells mL−1), concentrated samples had on average 31% fewer live cells mL−1 than unconcentrated samples for four out of five experiments. At high organism abundances (≥ 120 cells mL−1), unpreserved concentrated samples had on average 55% fewer live cells than unconcentrated samples. Alternatively, with preserved samples at low organism abundances, concentrated samples had on average 4.5× more cells than unconcentrated samples. At high organism abundances, concentrated samples had on average 6.4× more cells than unconcentrated samples. Differences were also observed between preserved and unpreserved samples. These findings can help to improve ballast water monitoring procedures and BWMS assessments, addressing a critical challenge to maritime environmental protection. • Concentration by gravity filtration led to cell loss in live phytoplankton samples. • Alternate concentration methods should be explored to mitigate cell loss. • Concentrating had different effects on live and preserved samples. • Concentrating samples is important to improve precision at low abundances. • Counting six subsamples improved precision in low abundance samples. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]