7 Conclusions
The MST field is still evolving rapidly and the associated evaluation tools described
in Sects. 3, 4, and 6 are in various stages of development, and it is unknown at
present what direction future methodological approaches might take. The SIPP
study was a success as it identified a select group of DNA-based markers (Sect. 3)
that are suitable for deployment, especially in California coastal waters. How well
these same markers might perform in other regions is not clear, so the SIPP study
makers (as well as any new ones that are developed) should be used with caution
until sensitivity and specificity have been evaluated outside of California. Also,
interpretation of results and subsequent management decisions are very difficult
without knowing how various DNA-based markers age and degrade over time in
different environmental matrices. Such SIPP-level aging studies are badly needed
as the results could have a major impact on just how useful DNA-based markers
really are. Many researchers are now investigating community analysis (Sect. 4) as
the next big improvement in MST approaches, but community analysis is very new
and it may or may not turn out to have much application in source tracking. Lastly,
before other new approaches like NSE and QMRA can be implemented with
confidence (Sect. 6), there are additional research questions that need to be
addressed including (a) the overall accuracy of present techniques for determining
whether the fecal signature at a given site is human or non-human in origin, (b) the
relative health risks associated with human and non-human fecal sources, and
(c) the level of scientific uncertainty in using this information in a management
context [105]. Such new approaches will likely be controversial wherever they are
considered for implementation. However, such consideration is only possible when
the science is able to fully support their feasibility in problematic recreational
waters [106]. The best overall approach at present is to follow the tiered system
(Sect. 5) that places MST within the proper context of a larger suite of methods that
are all useful in their appropriate context for accurately identifying the sources of
fecal pollution in water [6].
References
1. Dick LK, Bernhard AE, Brodeur TJ, Domingo JWS, Simpson JM, Walters SP, Field KG
(2005) Host distributions of uncultivated fecal Bacteroidales bacteria reveal genetic markers
for fecal source identification. Appl Environ Microbiol 71:3184–3191
2. Santo Domingo JW, Bambic DG, Edge TA, Wuertz SD (2007) Quo vadis source tracking?
Towards a strategic framework for environmental monitoring of fecal pollution. Water Res
41(16):3539–3552
3. Litton RM, Ahn JH, Sercu B, Holden PA, Sedlak DL, Grant SB (2010) Evaluation of
chemical, molecular, and traditional markers of fecal contamination in an effluent dominated
urban stream. Environ Sci Technol 44(19):7369–7375
4. Hagedorn C, Blanch A, Harwood J (2011) Microbial source tracking: methods, applications,
and case studies. Springer, New York, p 642
282
B. Badgley and C. Hagedorn
The MST field is still evolving rapidly and the associated evaluation tools described
in Sects. 3, 4, and 6 are in various stages of development, and it is unknown at
present what direction future methodological approaches might take. The SIPP
study was a success as it identified a select group of DNA-based markers (Sect. 3)
that are suitable for deployment, especially in California coastal waters. How well
these same markers might perform in other regions is not clear, so the SIPP study
makers (as well as any new ones that are developed) should be used with caution
until sensitivity and specificity have been evaluated outside of California. Also,
interpretation of results and subsequent management decisions are very difficult
without knowing how various DNA-based markers age and degrade over time in
different environmental matrices. Such SIPP-level aging studies are badly needed
as the results could have a major impact on just how useful DNA-based markers
really are. Many researchers are now investigating community analysis (Sect. 4) as
the next big improvement in MST approaches, but community analysis is very new
and it may or may not turn out to have much application in source tracking. Lastly,
before other new approaches like NSE and QMRA can be implemented with
confidence (Sect. 6), there are additional research questions that need to be
addressed including (a) the overall accuracy of present techniques for determining
whether the fecal signature at a given site is human or non-human in origin, (b) the
relative health risks associated with human and non-human fecal sources, and
(c) the level of scientific uncertainty in using this information in a management
context [105]. Such new approaches will likely be controversial wherever they are
considered for implementation. However, such consideration is only possible when
the science is able to fully support their feasibility in problematic recreational
waters [106]. The best overall approach at present is to follow the tiered system
(Sect. 5) that places MST within the proper context of a larger suite of methods that
are all useful in their appropriate context for accurately identifying the sources of
fecal pollution in water [6].
References
1. Dick LK, Bernhard AE, Brodeur TJ, Domingo JWS, Simpson JM, Walters SP, Field KG
(2005) Host distributions of uncultivated fecal Bacteroidales bacteria reveal genetic markers
for fecal source identification. Appl Environ Microbiol 71:3184–3191
2. Santo Domingo JW, Bambic DG, Edge TA, Wuertz SD (2007) Quo vadis source tracking?
Towards a strategic framework for environmental monitoring of fecal pollution. Water Res
41(16):3539–3552
3. Litton RM, Ahn JH, Sercu B, Holden PA, Sedlak DL, Grant SB (2010) Evaluation of
chemical, molecular, and traditional markers of fecal contamination in an effluent dominated
urban stream. Environ Sci Technol 44(19):7369–7375
4. Hagedorn C, Blanch A, Harwood J (2011) Microbial source tracking: methods, applications,
and case studies. Springer, New York, p 642
282
B. Badgley and C. Hagedorn