1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 3: ANALYSIS
The chronic toxicity of contaminants from Bolsa Chica sediments was also evaluated by
ToxScan, Inc., using clam worms, Nereis viriens. Five replicates of each test and control
sediments were randomly assigned to an array of 31-liter, flow-through glass aquaria. After
settling of the sediments, the tanks were attached to the flow-through aerated laboratory
seawater system. The flow was maintained at a rate to allow a 90 percent tank-volume
change every 4 hours, and the interstitial pore water salinity was monitored until it was
compatible with the test organism tolerance.
The test was initiated when 15 worms were added to each test aquarium. Test exposures
were carried out over a 28-day period. Each tank was monitored daily for temperature,
dissolved oxygen, salinity, pH, and any unusual behavior among the test organisms. After
exposure, the contents of each tank were gently rinsed through a screen and the surviving
worms were retrieved and counted.
The results of the sediment toxicity tests using N. viriens did not show any significant
differences in survival from the control sediments (Table 3-14). Chemical concentrations
associated with the NOECs are presented in Appendix G. Further analyses of these bioassay
data are provided in Section 3.2.1.2.
Pore Water
Pore water was extracted from composited sediment samples by centrifugation at 4° C for
30 minutes to generate 4.2 liters of sample. This amount was required to conduct the proposed
chemical and biological analyses. The 4.2-liter amount was attained for all but two samples for
which pore water bioassays were not conducted. Definitive toxicity tests were conducted on
the pore water samples with the bivalve mussel (Mytilus edulis). Mussels were induced to
spawn by thermal stimulation, and the eggs and sperm were collected in separate beakers of
filtered seawater. Fertilization was accomplished by the addition of an appropriate amount
of sperm suspension. After confirming a minimum of 90 percent fertilization, the tests were
initiated when an aliquot of fertilized eggs was pipetted into each test tube that comprised the
four replicates for each sample exposure. Temperature, dissolved oxygen, pH, and salinity
were monitored in “surrogate” containers for each test (concentrations and controls) at the
beginning and end of the test and daily during the 48-hour test exposure period. The mean
number of embryos added to each container was evaluated by counting embryos immediately
after inoculation in separate “surrogate” test tubes.
At the end of the 48-hour exposure period, the contents of each test tube were preserved with
formalin in preparation for microscopic evaluation. After gently mixing the test tube contents,
a 1-mL sample was collected using a pipette and the sample was placed onto a counting slide.
The total number of normal and abnormal larvae was determined based on the presence or
absence of internal tissue inside a complete larval shell. Assuming that abnormal larvae
would not survive, those individuals were counted as mortalities. Percentage survival and
normal development were calculated. Both of these values were corrected for mortality and
normal development associated with the control exposures. Percentage sample associated
with development and survival NOEC, LOEC, EC 50 , and LC 50 were also calculated.
The results of the 45 pore water toxicity tests are summarized in Table 3-14. The maximum
test concentration of these samples ranged from 0.78 percent of sample to 100 percent. NOECs
for larval development and survival ranged from 0.098 percent of sample to 100 percent of
sample. LOECs for larval development and survival ranged from 0.2 percent of sample to
ERA REPORT 3-28 SAC/143368(003.DOC)
7/31/02