Figure 8. Biota to sediment accumulation factors (BSAFs) for PAHs in laboratory-exposed L. variegatus compared with BSAFs for field-collected oligochaetes

ERDC TN-DOER-C23

September 2001

In the FVP, sediment was placed in the

field in a way that reflected how the

material would be handled in a

dredged material assessment. It is un-

likely in the current regulatory climate

that a similar study could be conducted

today (i.e., contaminated material

placed in the environment in an un-

confined manner without subsequent

capping). Consequently, future ex-

perimental/manipulative studies will

most likely rely on the use of sediment

placed in small, recoverable contain-

ers in the field. The use of containers

can lead to effects that may not neces-

sarily reflect effects in unenclosed

systems. It is possible that using con-

Figure 8. Biota to sediment accumulation factors (BSAFs)

tainers to evaluate contaminated sedi-

for PAHs in laboratory-exposed L. variegatus

ment effects on benthic recolonization

compared with BSAFs for field-collected

may lead to effects on recruitment that

oligochaetes (adapted from Brunson et al. 1998)

do not necessarily reflect recruitment

patterns of the surrounding community. Dudzik et al. (1979) reported heightened biological and

chemical activity along the edges and bottoms of experimental microcosms. Stephenson et al. (1984)

showed differences in the distribution of planktonic organisms related to the size of enclosure.

Flemmer et al. (1993) demonstrated effects of container size on benthic recolonization in laboratory

microcosms. These "edge effects" where spurious recruitment patterns are observed at the edge of

the container and issues associated with scaling (i.e., container size) must be considered and

accounted for in these types of studies.

Choosing between an experimental/manipulative and a correlative/observational approach or

development of new approaches for future validation efforts must be driven by the questions being

asked. For example, if one is interested in evaluating the predictive ability of a test for the assessment

of in-place contaminants, a correlative approach might be more appropriate as this more closely

approximates the type of assessment one is trying to represent. However, if one is trying to validate

a test for assessing potential effects associated with a disposal activity where material is physically

displaced to a new location (e.g., dredging and disposal), then an experimental approach might more

closely approximate the scenario one is trying to evaluate.

In both correlative/observational and experimental/manipulative approaches it is important to

measure a variety of biological (abundance, diversity, size/age class) and physicochemical parame-

ters (sediment chemistry, grain size, total organic carbon, redox, etc.) to capture important changes

in biological response and potential factors affecting exposure. Consideration must be given to

understanding the dynamics of the community (e.g., patterns of recruitment) in the area where the

study will be conducted. This will help to ensure that the field assessment is conducted in a way

that captures changes in the benthic community and enhances the ability of the study to discriminate

meaningful differences in community level responses. Because changes in benthic community