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

5.0 Benthic and Epibenthic Invertebrates
5.2.3 Data Analysis
Infauna data were entered into a database from the taxonomic laboratory sheets.
Macroinvertebrate data were coded from the field data sheets and entered into a separate
database. Data were subjected to quality assurance review.
Infaunal data from box core and Van Veen samples were standardized to number per 0.1 m 2 for
comparison with each other and historical data. Abundance and biomass of the trawl collected
invertebrates is presented as catch per unit effort (CPUE), which represents the number of
individuals captured standardized to the amount of the effort (total time or area sampled)
exerted. Averages were calculated for each station across surveys and for the total mean for all
stations and surveys combined.
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.
Cluster analysis was performed for the infauna data for both the winter and summer surveys.
This analysis was used to identify groups of stations that were biologically similar. Species
composition and relative abundance of the species defined the groups. Rare species (i.e.,
occurring at fewer than three stations) were excluded from the analysis. Figures of station and
species dendrograms were prepared from the cluster analysis.
5.3 INFAUNA
This section presents discussions of community summary measures (Section 5.3.1), a detailed
description and evaluation of species composition (Section 5.3.2) and dominant species
(Section 5.3.3), summary of spatial and temporal patterns (Section 5.3.4), and a comparison of
the 2008 Biological Survey results with historical studies (Section 5.3.5). The box core and Van
Veen comparison is discussed in Section 5.3.6. Raw summary data and a complete listing of
abundance by species and stations and of biomass data are provided in Appendix E.
5.3.1 Community Summary Measures
5.3.1.1 Abundance
A total of 10,772 infaunal invertebrates weighing 704 grams and comprising 258 species was
collected across the 29 stations (Table 5.3-1). Total infaunal abundance was nearly double
during the summer (7,017) compared to winter (3,755) surveys.
Mean abundances ranged from 80 to 488 individuals/0.1 m 2 (Table 5.3-1). Abundance varied
with depth and location in the harbors. Abundances were similar between the inner harbor
stations (80-488 individuals/0.1 m 2 ) and outer harbor stations (93-413 individuals/0.1 m 2 ), but
were markedly higher in shallow water (126-488 individuals/0.1 m 2 ) than in deep water (80-289
individuals/0.1 m 2 ).
In the outer harbor, mean abundance in shallow water was nearly two times higher (mean of
249 individuals/0.1 m 2 ) compared to deep water (mean of 142 individuals/0.1 m 2 , Table 5.3-1).
In the inner harbor, mean abundance at the shallow water station (488 individuals/0.1 m 2 ) was
approximately 3 times greater than at deepwater stations (173 individuals/0.1 m 2 ).
The highest mean abundances (mean > 400 individuals/0.1 m 2 ) were found at the Pier 300
Shallow Water Habitat and Consolidated Slip of inner Los Angeles Harbor (Stations LA7 and
2008 Biological Surveys of Los Angeles and Long Beach Harbors 5–3
April 2010