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5Â OtherÂ ApproachesÂ toÂ SettingÂ aÂ BallastÂ WaterÂ Â Â DischargeÂ StandardÂ The EPA and USCG seek a scientifically based process for determining a ballast water discharge standard that will protect against the establishment of new nonindigenous aquatic species in the nationâs waterbodies and protect and preserve resident species and other beneficial uses in these systems. In the ab- sence of data and models necessary to support a science-based quantitative ap- proach (see Chapter 4), expert opinion has been a common alternative to model- ing to advance discharge standards. Expert opinion can be defined as a process by which a person, or team of individuals, with a high degree of knowledge pertaining to a particular topic draws upon that knowledge to propose an estimate. In the area of standards for living organisms in ballast water discharge, expert opinion processes have taken a number of forms and, as observed by Lee et al. (2010), produced a wide range of outcomes. This chapter discusses strengths and weaknesses of the expert- opinion approach and reviews three expert opinion-based standards for living organisms in ballast discharge: the (1) IMO standard setting approach, (2) Cali- forniaâs Zero Detectable Living Organism standard setting approach, and (3) Natural Invasion Rates as a basis for a standard. The Natural Invasion Rate me- thod put forward by Cohen (2005, 2010) starts with a desired invasion rate based on expert opinion, and then combines it with a quantitative riskârelease relation- ship (much like those discussed in Chapter 4), to derive allowable discharge levels. This chapter considers only the expert opinion-based portion of the me- thod. EXPERT OPINION AS AN APPROACH TO DECISION-MAKING Expert opinion has been applied in the field of biological invasions in a number of ways. First, expert opinion has been used to identify nonindigenous species that may pose problems if introduced to a new country (see IUCN, 2000; European Environment Agency, 2010; and Kolar and Lodge, 2002). The Cana- dian government developed a risk assessment for silver and bighead carp species Â 114Â
OtherÂ ApproachesÂ toÂ SettingÂ aÂ BallastÂ WaterÂ DischargeÂ StandardÂ Â 115Â Â based upon expert opinion, which resulted in a regulation banning live sales by fish retailers (Mandrak and Cudmore, 2004). Expert opinion also has been used to screen for invasive, weedy plants and insect pests, among others (see Tucker and Richardson, 1995; Daehler et al., 2004; Paini et al., 2010). An inherent advantage of the expert opinion approach is that it can produce estimates in the absence of robust data sets. Some models based on expert opi- nion can be cross-checked using other methodologies, allowing researchers and managers to consider the biological realism of their predictions (Phelong et al., 1999; Paini et al., 2010). Nonetheless, there often remains considerable uncer- tainty in the output from expert opinion, especially when there are critical gaps in understanding underlying mechanisms. Expert opinion can be greatly affected by problem framing, context depen- dence, and motivational bias by participants (Burgman, 2005). Thus, a key problem is that very different outcomes may result from different parties consi- dering the same problem. It is also difficult to test the output for validity since critical considerations are often implicit in the process. Consensus-based expert opinion by cross-disciplinary teams may help eliminate blind spots in the analy- sis in terms of types of expertise, but these exercises often must limit the number of experts per discipline to one individual. As a result, inherent biases within an expert become a greater concern. Maguire (2004) concluded that risk assessment based upon expert opinion is often conflated with risk management, and that assessments of risk based on individual judgment often incorporate personal outcome preferences. A further problem is the influence of incomplete information on decision making. For example, highly invasive species including the emerald ash borer (Agrilus pla- nipennis) and quagga mussel (Dreissena rostriformis bugensis) had little or no invasion history prior to colonizing North America, and expert opinion based on invasion history likely would have concluded that these species pose little risk. While risk assessments based upon performance (effect) in native regions may be informative and are commonly conducted, the colonization process can result in evolutionary (genetic) changes, where native and introduced populations dif- fer substantially. Moreover, invasions by definition place species in novel envi- ronments, with a different assemblage of organisms. Thus, native populations may be poor predictors of population dynamics, interactions, and effects in an invaded area. Data on the concentration of living organisms in ballast water and on the probability of invasions occurring in U.S. waterbodies as a result of ballast water are extremely limited. Thus, despite its drawbacks, expert opinion has unders- tandably played a major role in ballast discharge standard-setting to date, and it will likely be involved as part of the risk management decision-making process into the future.
116Â PropaguleÂ PressureÂ andÂ InvasionÂ RiskÂ inÂ BallastÂ WaterÂ Â IMO STANDARD SETTING APPROACH The best-known example of an expert opinion-based standard setting process for ballast water is the agreement reached at the 2004 Diplomatic Confe- rence of the International Maritime Organization (IMO), which included 74 IMO member countries, the European Community, and 18 non-governmental organizations (Gollasch, 2005). This agreement was formalized as the IMO International Convention for the Control and Management of Shipsâ Ballast Water and Sediments and was signed by 67 IMO member countries. As of May 2011, the Convention has been ratified by 28 countries collectively accounting for over 28 percent of global merchant shipping (IMO, 2011). The IMO Con- vention will come into force one year after not less than 30 States representing 35 percent of the worldâs merchant tonnage have ratified without reservation. In this rendition, the expert-opinion process involved at least two sets of ex- perts (there was some overlap) and two sets of rules. Specifically, the IMO Ma- rine Environment Protection Committee (MEPC) requested the assistance of a Study Group (on Ballast Water and Other Ship Vectors) of the International Convention for the Exploration of the Sea (ICES), and also a group from the shipping industry to propose a starting point for IMO negotiations to achieve discharge standards. The ICES Study Group, predominantly aquatic invasion biologists, reviewed available data sets to date related to concentrations of or- ganisms in untreated ballast, characterizing the range and distribution across many vessels for different types of organisms. This expert group recommended that to âsignificantly reduce the risk of invasions associated with ballast water beyond the present situation, permissible discharge concentrations identified by any treatment/management standards should fall greatly below the median val- ues observed presently for untreated/unmanaged ballast water.â This would have the effect of reducing high concentration discharges, and the group consi- dered empirical and theoretical evidence indicating that invasion likelihood in- creases with increasing concentration (International Council for the Exploration of the Sea, 2003). Recognizing that biological invasions via ballast water occur across a broad span of phyla and size classes, and that organisms comprising these groups dif- fer tremendously in abundance in both nature and ballast water, the ICES study group recommended that the IMO performance standard classify biota contained in ballast water into categories based on size or taxonomic group. This group made recommendations of discharge standards for two of these sizes classes: greater than 50 ïm (zooplankton) and between ten and 50 ïm (phytoplankton) to achieve concentrations three orders of magnitude below observed median values in untreated ballast (the recommended standards correspond to 0.4 zoop- lankton per m3 and 13.3 phytoplankton per liter). Because the recommended approach considers total abundance of organisms in a particular size class (i.e., a guild) in a shipâs discharge, the risk associated with release of any one species would be expected to be lower since ballast water communities usually comprise numerous species.
OtherÂ ApproachesÂ toÂ SettingÂ aÂ BallastÂ WaterÂ DischargeÂ StandardÂ Â 117Â Â The first stage of the process for crafting the IMO standard represented the consensus expert opinion of the ICES Study Group experts involved. The out- put of this analysis was then transmitted to the relevant IMO committees and working groups to be considered along with operational concerns cited by indus- try. The standard that emerged from this two stage process places numerical limits on abundances in treated ballast effluent of less than ten viable organisms per m3 greater than or equal to 50 Î¼m in minimum dimension (zooplankton and zoobenthos) and less than ten viable organisms per ml less than 50 Î¼m but greater than or equal to 10 Î¼m in minimum dimension (including phytoplankton and protists). The IMO also incorporated into the standard toxigenic Vibrio cho- lerae (serotypes O1 and O139), the etiologic agents of pandemic cholera, and two routinely used fecal-indicator bacteria, E. coli and intestinal Enterococci. These latter two are frequently used to assess the safety of recreational surface waters, e.g., swimming beaches. Some are concerned that the allowable levels of live organisms in the standard generally are too high to be protective. In par- ticular, the USCG during negotiations for the IMO agreement indicated that standards needed to be considerably more stringent (i.e., 100 times) to be protec- tive, approaching more closely recommendations from the ICES Study Group. Regardless, it appears that the IMO D-2 standard represents a significant reduc- tion in concentrations beyond ballast water exchange, especially for the largest size range (International Council for the Exploration of the Sea 2003; Minton et al., 2005). ZERO-DETECTABLE DISCHARGE STANDARD The State of Californiaâs existing and anticipated standard for larger plank- tonic organisms in discharged ballast water is âzero detectableâ living or cultur- able organisms. Like the IMO standard setting process, the process associated with the genesis of this standard also involved the opinions of technical experts (biologists) as well as industry and other groups (California State Lands Com- mission, 2010). The expert group recognized that (a) the probability of invasion declined with concentration and (b) there was great uncertainty surrounding the riskârelease relationship. This group took a precautionary approach, while ac- knowledging that enforcement against a standard of zero living organisms has practical constraints. Unlike the IMO D-2 standard, the zero detectable dis- charge standard applies to all size classes and taxa (if the word âlivingâ may be considered applicable to viruses) and is to be put in force by January 2020 (Faulkner, 2010). [The interim standard is zero detectable living organisms for taxa >50ïm, 0.01 organisms per ml for sizes between 10 and 50 ïm, and no more than 103 bacteria and no more than 104 viruses per 100 ml of ballast water discharge. Interim standards are to be in place between 2009 and 2016 (Faulk- ner, 2010).] This approach to a standard is appealing in its straightforwardness, but as Lee et al. (2010) argue, its rationale is predicated on an actual zero discharge,
118Â PropaguleÂ PressureÂ andÂ InvasionÂ RiskÂ inÂ BallastÂ WaterÂ Â while its practical application can differ substantially from zero detectable dis- charge. The zero-detectable concept is constrained heavily by the sampling re- gime employed and associated sensitivity, which will depend on the analystsâ technical capabilities and financial resources. Recent advances in molecular ecology, such as use of speciesâ environmental DNA (e.g., Mahon et al., 2011; Jerde et al., 2011), are expanding our capability to detect rare organisms in wa- ter, although none can yet unequivocally decipher whether all organisms de- tected are living or dead. Because of the practical constraints in detecting living organisms when they are rare, the zero-detectable standard may be operationally no more stringent than other standards. The lower the density of living organisms achieved in the effluent, the more difficult the task of detecting organisms and determining whether the water is compliant with the zero-detectable standard. Lee et al. (2010) nicely summarized this by estimating the uncertainty inherent in sam- pling different volumes of water (their Table 18). For example, even should a 10 m3 sample (a huge sample) of ballast water contain no organisms, the actual concentration of organisms in the tank could be as high as 0.3 per m3. Arguably, there could be fine tuning of the Lee et al. (2010) analysis should the distribu- tion of organisms be found to be other than Poisson, but any such change would only alter the levels of uncertainly associated with a particular sampling regime. More recently, Miller et al. (2011) also considered organisms with a Poisson distribution in ballast water effluent. They demonstrated that the density of or- ganisms and volume sampled had strong effects on decisions to reject whether ballast water is compliant with a selected standard, while the permissible type I error rate (i.e., false positives or rejection of compliant ballast) had slightly less influence as modeled. Thus, while a laudable ideal, the zero-detectable standard is functionally de- fined by the ability to characterize concentrations of organisms at low densities. If organisms are detected, it is clear a shipâs ballast effluent is in violation. However, critically, the absence of live organisms in a sample or set of samples does not provide sufficient information to accurately assess densities, and there is always a non-zero probability that organisms are present below some thre- shold (defined by the specific sampling effort imposed). Thus, while Califor- niaâs standards clearly represent a reduction in concentrations below those ob- served in ballast water exchange, the exact discharge standard is largely unde- fined and contingent on sampling protocols, representing an operational defini- tion that is driven by sampling statistics. NATURAL INVASION RATES The Natural Invasion Rate (NIR) approach to standard setting incorporates both a risk assessment and a risk management component. The risk assessment component assumes that an empirical, linear relationship can be determined be- tween the rate of organism release in ballast water and the resulting rate of new
OtherÂ ApproachesÂ toÂ SettingÂ aÂ BallastÂ WaterÂ DischargeÂ StandardÂ Â 119Â Â species invasions (see Chapter 4). The risk management component proposes an acceptable target invasion rate based on expert opinion from which the corres- ponding target discharge rate is determined. In this case, expert opinion has concluded that the natural (i.e., non-anthropogenic, background) invasion rate should be the target ballast-mediated invasion rate. This discussion focuses on this latter component of the approach (i.e., the risk management step). Cohen (2005) identified some difficulties inherent in estimating natural in- vasion rates and provided coarse estimates based on expert opinion that span three orders of magnitude. Providing any validation or better assessment is problematic because there is insufficient information to determine a natural in- vasion rate. The scale of available paleontological data is inconsistent with that needed for application of a NIR standard. For example, natural port-to-port in- vasion rate data are required, whereas available data refer to large-scale disper- sal events (e.g., trans-Pacific regional migrations; see Vermeij, 1991) and, thus, are not an appropriate comparator. It is expected that natural estuary-to-estuary trans-Pacific migrations would be much lower than the measured regional mi- grations. While some natural invasion rate data are available, in terms of Pleis- tocene migrations and faunal shifts along the California coast, including ancient embayments (Roy et al., 1995), they do not include trans-Pacific species move- ments. In addition, even if data were available for one estuary, differences like- ly exist among different recipient ecosystems and would need to be taken into account. These problems with estimating the natural invasion rate interfere with the potential to obtain a meaningful organism discharge standard that would be equivalent in its effect for all locations, or that would indeed be a desirable tar- get. There is an assumption within the NIR approach that an acceptable inva- sion rate is less than the natural invasion rate. Such assumptions make it clear that NIR is based on expert opinion as much as the IMO standards and the zero- detectable standard of CA. CONCLUSIONS The data available from which to derive scientifically based standards for living organisms in ballast discharge have been incomplete and insufficient. This situation results partly from the degree of variability possible across ballast discharges, the difficulty in garnering representative samples of live organisms in ballast discharge and the lack of a systematic approach for doing so, and the lack of baseline measures to detect the presence of newly established popula- tions of nonindigenous organisms in U.S. waters. A discharge standard based on expert opinion has provided a starting point for the regulatory process and can facilitate progression to a scientific model. For example, as ships attempt to meet the IMO D-2 standard, much of the variation in potential densities of live organisms in ballast discharge will be modulated. Advancing scientific under- standing of the probability of invasion associated with such discharges, and the
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