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

6.0 Riprap Biota
2.5 cm-wide chisel. Scrapings were placed in approximately 0.333 mm mesh labeled bags
(panty hose), transferred to jars labeled with station identification numbers, and fixed in 10%
buffered formalin. Relatively large organisms observed by the diving biologists in the vicinity of
the quadrats were also noted.
In the laboratory, scraped quadrat samples were sorted into major taxonomic groups, including
molluscs, polychaetes, crustaceans, echinoderms, minor invertebrate phyla (others), and algae.
Organisms were identified to the lowest practicable taxon (usually species) and counted. Algae
and colonial animals were classified as present, common, or abundant based on the presence
of one, two to five, or more than five colonies or holdfasts per sample, respectively. Wet weight
biomass was measured for each of the six taxonomic groups.
6.2.2 Data Analyses
Count and biomass data for the scraped samples were entered into a database from the
taxonomic laboratory sheets and reviewed for completeness. Data for these samples are
presented as abundance and biomass per 0.01 m 2 (7.5 cm by 15 cm area). The number of
unique species was calculated for each station. Statistical analyses (Analysis of Variance, t-
test) were performed to test for differences between box core and Van Veen samplers.
Diversity was calculated with three different indices, which are derived measures based upon
the number of species (species richness) and their abundances (equitability). The Shannon-
Wiener diversity index tends to emphasize the equitability of the species distribution in a
community. The Margalex Index incorporates the number of species and total number of
individuals. The Dominance Index computes the number of species that account for 75% of the
total abundance.
6.3 COMMUNITY SUMMARY MEASURES
6.3.1 Abundance
A total of 16,528 invertebrates per 0.01 m 2 was
collected from riprap scrapings during the
winter and summer surveys combined (Table
6.3-1). Mean total abundances (mean of the
eight stations) were highest in the lower
intertidal (233 per 0.01 m 2 ), lowest in the upper
intertidal (140 per 0.01 m 2 ), and intermediate in
the subtidal zone (183 per 0.01 m 2 ) (Table
6.3-1).
Mean abundances ranged highest on the
Middle Breakwater (Station LARR1) (185 to 670
per 0.01 m 2 ) in the outer harbor. Otherwise
mean abundances were similar among inner
and outer harbor stations. Mean abundances
at other outer harbor stations ranged from 14 to
276 per 0.01 m 2 across tide zones. Mean
abundances at inner harbor stations ranged
from 55 to 254 per 0.01 m 2 across tide zones.
Differences in mean abundances generally were similar among stations that varied in substrate
type with few exceptions. For example, mean abundances across tide zones were similar at
Station LARR3 located on a pier piling (150 to 254 per 0.01 m 2 ), Station LBRR2 located on
2008 Biological Surveys of Los Angeles and Long Beach Harbors 6–3
April 2010