appendix b final 2008 biological surveys of los angeles and long ...

5.0 Benthic and Epibenthic Invertebrates
dominance of several species. Ciratulid polychaetes (Monticellina, Tharyx) have been
numerical dominants since the 1950s. The pollution-tolerant polychaete Capitella capitatacomplex
ranked as one of the top five dominants in the 1970s and 1983. However, it was not a
numerical dominant in 1986-1987, 1994, 1996, 2000, or 2008. A decrease in the occurrence of
this species complex indicates a trend of benthic habitat improvement over time. Also
suggestive of habitat quality improvement was the similarity in species assemblages between
inner and outer harbor basins, slips, and channels with the present study.
Similar to the 2000 study, the present study showed a substantial increase in abundance from
the winter to the summer survey. During 2000, the number of species also showed a similar
seasonal difference; however, the numbers of species were similar among winter and summer
surveys in 2008. MEC (2002) speculated that the seasonal difference in species number in
2000 may have been related to large-scale oceanographic conditions because the study
following a strong El Niño-La Niña period. The similarity in species composition throughout the
year during the 2008 study was similar to other historical studies.
5.3.6 Box Core and Van Veen Comparison
Both box core and Van Veen samplers have been used to survey the benthic infauna
community in the harbors. Historical and current baseline studies in the harbors have generally
used a box corer. The same box core sampler and methodology was used for the present study
as with the 2000 study. Both the box core and Van Veen sampler collect samples with a
surface area of 0.1 m 2 . However, historical studies using a box corer have subdivided the
sample into 0.06 m 2 and 0.04 m 2 fractions with analysis of the infauna from the larger fraction
(MEC 1988, 1997, 1999; SAIC 1996, MEC 2002). This was done to provide a comparable
sample to early historical studies that used 0.06 to 0.0625 m 2 coring devices (e.g., HEP 1976,
1980). In contrast, the Van Veen sampler has been adopted for use with sanitation district
outfall monitoring, including the Terminal Island Water Reclamation Plant monitoring program in
Los Angeles Harbor, and has been used in recent regional Bight monitoring programs.
A special study was conducted to evaluate whether assessment of the benthic infauna
community is substantially influenced by choice of these two types of sampling gear and
analysis of samples that differ between 0.06 m 2 and 0.1 m 2 in surface area. During the summer
survey, ten benthic stations were sampled with a Van Veen grab sampler in addition to the box
core sampler. Count data were standardized to 0.1 m 2 for the comparison.
No statistical differences in abundance or number of species were detected among gear types
with t-tests (p>0.2) or Kruskal-Wallis one-way analysis of variance on ranks (P>0.9). A total of
2,677 invertebrates were collected by Van Veen and 2,160 were collected by box core (Table
5.3-7). The overall mean abundance across stations also was similar with box core (216) and
Van Veen (267) samplers. A similar result was seen for number of species: 378 species were
collected by Van Veen and 355 species were collected by box core and overall means across
stations were 37.8 and 32.4, respectively (Table 5.3-8). Although results were more variable at
some stations when taxonomic categories were compared, there was no consistent trend of
higher or lower values associated with either gear type. This suggests that variability among
samples related more to small-scale differences in organism abundance (e.g., patchiness) at a
station level rather than to a broader trend related to gear type. Results of the special study
indicate that historical and more recent assessments of the infauna community in the harbors
using coring devices with surface areas ranging from 0.06 to 0.1 m 2 should be comparable.
2008 Biological Surveys of Los Angeles and Long Beach Harbors 5–7
April 2010