1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 3: ANALYSIS
conductivity within normal range for Ceriodaphnia. The remaining three had conductivity
readings that indicated total dissolved solids would be out of the acceptable range for the
Ceriodaphnia and so these samples were tested using the marine mysid (Mysidopsis bahia) as
described in the next subsection.
The chronic toxicity of the waters was tested using a series of five dilutions ranging from
6.25 to 100 percent site sample. The tests were conducted using 10 test organisms per test
concentration, with only one test organism in each of 10 polystyrene cups for a given test
concentration. The animals were monitored daily for 6 days for survival and reproductive
success. The results of the toxicity tests (Table 3-14) were statistically evaluated against the
control samples. The NOEC for survival and reproduction was 50 percent for both samples,
and the LOEC for survival and reproduction was 100 percent for both samples. The full
bioassay report is presented in Appendix F and chemical concentrations associated with the
NOEC and LOEC values are presented in Appendix G.
Mysidopsis bahia
Toxicity tests with Mysidopsis were conducted following U.S. EPA (1994f) guidelines for
short-term toxicity tests for marine organisms. The tests were conducted by ToxScan, Inc., in
Watsonville, California. As noted above, three of the stormwater monitoring samples had
conductivity readings that indicated that total dissolved solids would be out of the
acceptable range for the Ceriodaphnia, so these samples were tested using the marine mysid
(Mysidopsis bahia).
The sample salinity was adjusted to 25 ppt using Forty Fathoms® Brand Bioassay Grade sea
salt and E-Pure water. The chronic toxicity of the waters was then tested using a series of
5 dilutions ranging from 6.25 to 100 percent site sample. The tests were conducted using
8 replicates for each test concentration with 5 test organisms per replicate. The animals were
monitored daily for 7 days for survival. At the conclusion of the test, each surviving mysid
was microscopically examined to determine its gender, each female was scored for presence
of eggs in the oviduct or brood pouch, and, finally, the dry weight of the surviving mysids in
each replicate was determined. The results of the toxicity tests (Table 3-14) were statistically
evaluated against the control samples. The NOEC for survival, weight, and fecundity was
100 percent in all samples. The LOEC for survival, weight, and fecundity was >100 percent in
all samples. The full bioassay report is presented in Appendix F, and chemical concentrations
associated with the NOEC and LOEC values are presented in Appendix G.
3.2.1.2 Bioaccumulation Tests
The potential for bioaccumulation of contaminants from Bolsa Chica sediments was
evaluated by ToxScan, Inc., using the clam worm, Nereis viriens; these worms were also
monitored to evaluate survival, as described above. The bioaccumulation tests were
conducted using sediment samples collected from a subset of the sample locations; the tests
evaluated the uptake of contaminants by the worms. The complete report for the
bioaccumulation tests is included in Appendix F.
Although most of the test containers received 15 worms in each test aquarium, 5 percent of
the test containers received 25 worms to provide sufficient tissue for quality assurance
(matrix spike/matrix spike duplicate) during tissue chemical analysis. After the 28-day
exposure period, the contents of each tank were gently rinsed through a screen, and the
ERA REPORT 3-30 SAC/143368(003.DOC)
7/31/02