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Page Title: CONCLUSIONS AND RECOMMENDATIONS
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ERDC TN-DOER-E19
March 2005
introduced sediments on the benthic community. It also may serve to complicate the
establishment of cause-and-effect relationships. A model that provides a means to quantify the
extent and timing of mixing along the sediment-water interface should be considered an element
essential to any effort to quantitatively define the biological impacts of dredge-induced
sedimentation.
Another type of available model is the dynamic energy budget (DEB) individual-based model
(Noonburg et al. 1998, Nisbet et al. 2000) to predict effects of stress on organism growth and
survival.  These models need detailed lab data for input (growth, respiration, survival) in
response to sediment exposure. They are very useful for specific predictions of impacts and how
to link these individual effects to population responses.  However, these require detailed
laboratory results on response of specific organisms to bedded sediments.
CONCLUSIONS AND RECOMMENDATIONS:  Of the biological resources of concern
listed earlier (SAV, commercial shellfish beds, fish, and spawning areas), the first two are very
amenable to conventional monitoring techniques to assess physiological responses of the
organisms because they are stationary. For monitoring the response of fish to sedimentation
events in the field, the available techniques would vary with the location and scale of the
sedimentation event. Once that is known, monitoring the behavioral responses of fish would be
most instructive. Current tagging technologies provide a number of possibilities for both juvenile
and adult fishes in order to measure behavioral responses.
Monitoring the effects/responses to spawning areas would be much more complicated;
possibilities exist for monitoring both gamete/larvae reactions as well as adult spawning behavior
through the use of quantitative motion analysis (Dutta et al. 1989, Gerlich et al. 2003). While this
offers the potential for addressing the effects of suspended sediment particles on swimming
speeds, velocity, and orientation of either adults or gametes, it is more amenable to laboratory
studies rather than field monitoring efforts. Some new emerging technologies using motion
analysis are being developed in the medical diagnostic field (wearable accelerometric
dataloggers) for assessing movement disorders (Sabelman et al. in preparation). While these new
technologies hold potential for studying adult fish movements, it will be some time before they
will be affordable or could be adapted for aquatic organisms in either laboratory or field studies.
Because knowing the "scale at which the problem exists" is a first-order question, priorities for
the short term would be to invest in appropriate instrumentation to determine both ambient and
dredging-induced sedimentation rates. Field trials at a number of different field sites with
different types of dredging operations (e.g., clamshell, cutterhead, and trailer suction dredge)
should be performed to determine the area of seafloor affected by sediment accumulation, the
vertical height of these accumulated layers, and the timescale over which these accumulations
develop. Once definite data are acquired regarding the scale of sedimentation, biological impacts
could be more effectively assessed.
ACKNOWLEDGEMENTS: This review was sponsored by the U. S. Army Engineer Research
and Development Center, Vicksburg, MS, under the Dredging Operations and Environmental
Research (DOER) Program. The authors wish to express their thanks to the participants in the
survey of expert opinion: Drs. K. Able (Rutgers University), B. Berstein, and W. F. Bohlen
9

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