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3545 dx.doi.org/10.1021/es102790d |Environ. Sci. Technol. 2011, 45, 3539–3546
Environmental Science & Technology ARTICLE
the ecological and economic outcomes of these regulations.
Consequently, it is imperative that the statistical aspects of the
sampling protocols be defined. For example, it will be necessary to
identify the thresholds used to classify ballast discharge as
compliant or noncompliant based on the chosen R value and
enforcement approach. Thus, if all the organisms in 1 m3 of BW
are counted, and a “presumed innocent” approach is used with R
= 0.05, then a ship would be classified as compliant if e15
organisms were counted. However, if a “presumed guilty”
approach is used with the same parameters, then a ship would
be classified as compliant if e4 organisms were counted. Cur-
rently our understanding of how large an inoculation must be to
achieve a successful invasion remains coarse.12 A firmer compre-
hension of dose response relationships and invasion success
could inform us about which regulatory approach is most appro-
priate, as well as whether it is crucial to differentiate concentra-
tions that are very close to, but still exceed proposed discharge
concentrations. Unfortunately, such biological information is
difficult to collect and strong generalities remain elusive. Given
the profound influence that these variables can have on regulatory
outcome, the consequences of regulatory decisions must be
described clearly.
In the end, it is necessary for regulators to determine the level
of environmental protection that is acceptable in accordance with
scientific evidence and societal needs and desires. In the case of
BW-borne biota, the scientific component of decision-making
includes a specific set of target discharge standards as well as
guidance about the required stringency of tests and/or monitor-
ing procedures to provide sufficient confidence that discharge
standards are achieved. Scientific analyses can inform policy
makers about the levels of uncertainty associated with testing
and monitoring protocols, but regulators must determine how
much uncertainty is acceptable.
’ ASSOCIATED CONTENT
bS Supporting Information. Discussion of potential
sources of error, both sampling and recovery errors, in BW
discharge analysis; table containing descriptions of error types,
the expected effects on sample volume, and possible remedies;
simple sensitivity analysis describing the effects of under-count-
ing on statistical power according to sample volume and R;
example calculations of both discrete and cumulative Poisson
probabilities. This information is available free of charge via the
Internet at http://pubs.acs.org/.
’ AUTHOR INFORMATION
Corresponding Author
*Phone 443-482-2439; e-mail: millerw@si.edu.
’ ACKNOWLEDGMENT
Support was provided in part by the Maryland Port Admin-
istration (508923) and U.S. Maritime Administration
(DTMA1H0003) to the Maritime Environmental Resource
Center; USCG/National Ballast Information Clearinghouse for
A.W.M. (HSCG23-06-C-MMS065); as well as by a U.S. EPA
postdoctoral fellowships to M.F. (AMI/GEOSS EP08D00051
and NHEERL). We thank the International Council for the
Exploration of the Sea (ICES), Intergovernmental Oceano-
graphic Commission (IOC) and International Maritime
Organization (IMO) Working Group on Ballast and Other Ship
Vectors, as well as G. F. Riedel, H. Lee II, D. A. Reusser, R. A.
Everett, M. S. Minton, and K. J. Klug for their comments and
suggestions on our analyses. This document has been reviewed in
accordance with U.S. Environmental Protection Agency policy
and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or re-
commendation for use.
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