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Experimental/Manipulative Studies (cont.)
September 2001
nor were they intended as field validation efforts. However, the approaches used in these studies
are instructive and as such are included in this review. For example, studies by Tagatz and Ivey
(1981) and Tagatz et al. (1987) evaluated the effects of pesticide-spiked sediments on benthic
recruitment. Although these studies were not implicitly designed as field validation studies, they
did use an experimental/manipulative approach to compare laboratory and field colonization rates.
These studies examined the effects of the synthetic pyrethroid pesticide fenvalerate on benthic
recruitment. In their 1981 study Tagatz and Ivey placed aquaria in the environment to allow
"natural" colonization to occur while a second set of aquaria were allowed to colonize under an
unfiltered flowing seawater system in the laboratory. The laboratory-developed communities were
then dosed continuously via a flow-through aqueous exposure system for 8 weeks at concentrations
of 0.01, 0.1, and 1.0 g fenvalerate/L. For the field portion of the study, aquaria were retrieved
from the field after about 8 weeks and then dosed in the lab for 1 week at concentrations of 0.1, 1.0,
and 10.0 g fenvalerate/L. Results indicated that benthic community structure was significantly
altered in both laboratory- and field-derived communities at concentrations of 0.1 and 1.0 g
fenvalerate/L. In a 1987 study, Tagatz et al. modified their earlier approach by evaluating
recruitment in aquaria containing fenvalerate-spiked sediments. Sediments were spiked at concen-
trations of 0.1, 1.0, and 10 g/g. Six groups of four aquaria each were placed in the field. Each
group consisted of an unspiked control, 0.1, 1.0, and 10 g/g spiked sediment. Sediment cores were
obtained at 0, 7, 21, 35, 49, and 56 days for subsequent chemical analysis. After 8 weeks all aquaria
were removed from the sediments and returned to the laboratory for benthic community analysis.
Results indicated that the 10-g/g treatment showed significant changes in benthic community
A similar study by Kalke, Duke, and Flint (1982) studied the impact of weathered oil on benthic
communities colonized in the laboratory and in situ. Aquaria with clean bedded sediment were
established under both laboratory and field conditions and allowed to be colonized by planktonic
larvae for a period of 8 weeks. Weathered oil was distributed to both laboratory and field replicate
compartments; after 4 additional weeks, the experiments were terminated. Results indicated that no
significant effects from the oil treatment were observed for the laboratory-colonized communities,
whereas total density of macrobenthos, species composition, and numbers of species were signifi-
cantly reduced in the field-colonized systems. The authors suggested that the differences observed
between laboratory and in situ exposures were due to differences in mechanisms of colonization.
In the laboratory studies, colonizing organisms were supplied to the aquaria via a water pump
whereas in the in situ studies colonizing organisms settled naturally or moved into the compartments
from the surrounding environment. As a consequence, in the in situ studies, densities of colonizing
organisms were much higher than in the laboratory studies. Low oxidation-reduction potential
measurements in both field and lab samples suggested that the oil had reduced the depth of the
oxygenated layer by approximately half, which would adversely affect subsurface benthic produc-
tion and alter other processes such as nutrient regeneration. This reduction in the oxygenated layer
manifested effects in the higher density in situ studies but not in the lower density laboratory
colonization experiments.
The Field Verification Program (FVP) initiated by USACE and USEPA in the 1980's represents
the largest and most relevant (in terms of dredged material testing) field validation effort conducted
to date. The FVP followed an earlier and much larger research program conducted by USACE in

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