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

5.0 Benthic and Epibenthic Invertebrates
5.0 BENTHIC AND EPIBENTHIC INVERTEBRATES
5.1 INTRODUCTION
Invertebrate organisms (e.g., worms, shrimps,
crabs, clams, snails, starfish) live within, on, or
associated with the sediment that comprises
the benthos. Small invertebrates that burrow
within, or anchor to the bottom, and feed in the
sediments or at the sediment-water interface
are termed infauna. Larger invertebrates that
reside at or above the sediment surface are
termed epibenthic macroinvertebrates.
Invertebrates are important community
members because:
• Their burrowing and feeding activities
alter the physical and chemical nature
of the sediments and create habitat heterogeneity, which can lead to greater biodiversity
and a more productive community.
• Many of them live in direct contact with the sediments and therefore can be good
indicators of sediment and habitat quality.
• They tend to be an intermediate trophic link between primary producers (e.g., plankton,
algae) and higher trophic levels (e.g., fish, birds, mammals) by converting detritus and
organic material from the sediments and sediment-water interface into animal biomass.
• Some are commercially important for food and bait (e.g., lobster, crabs, mussels, clams,
ghost shrimp, and worms).
Because of their fundamental importance to the marine ecosystem, benthic invertebrates have
been sampled as part of nearly every survey of the Los Angeles-Long Beach harbors and
nearby waters that has been conducted for the past 35 years. As part of the present study,
infaunal and epibenthic macroinvertebrates were sampled from a range of habitats in Long
Beach and Los Angeles Harbors. Infaunal invertebrates were collected by boxcore, and
epibenthic macroinvertebrates by otter trawl, as described below. A special study also was
conducted to evaluate the comparability of invertebrate data collected by box core with data
collected by a different sampler, the Van Veen grab, which has been used in other studies in the
harbors and in regional Bight programs.
Methods used to survey infaunal invertebrates and epibenthic macroinvertebrates are described
in Section 5.2. Survey results for infauna are presented in Section 5.3, and results for
epibenthic macroinvertebrates are presented in Section 5.4. Species considered to be nonindigenous
to the harbors are discussed in Section 5.5. A summary of spatial and temporal
patterns observed in 2008 and how they compare to historical studies within the harbors is
provided in Section 5.6.
5.2 METHODOLOGY
Benthic invertebrates were collected twice during the 2008 baseline study, in January (winter)
and July (summer). Infauna were collected at a total of 29 stations, 15 in Los Angeles Harbor
and 14 in Long Beach Harbor (Figure 5.2-1), using a 0.1m 2 -surface-area box core sampler.
2008 Biological Surveys of Los Angeles and Long Beach Harbors 5–1
April 2010