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

6.0 Riprap Biota
Polychaetes were the second most abundant
taxonomic group with a mean abundance of 33
individuals/0.01 m 2 across tide zones. Mean
polychaete abundance was substantially greater in
lower intertidal and subtidal zones (38 to 45/0.01 m 2 )
than in the upper intertidal (15/0.01 m 2 ).
Echinoderms, molluscs, and other phyla similarly
accounted for a mean abundance of 12 to 14
individuals/0.01 m 2 across tide zones. Similar to
crustaceans, molluscs had a similar mean abundance
across depth zones with 14/0.01 m 2 in the upper
intertidal, 12/0.01 m 2 in the lower intertidal, and
17/0.01 m 2 in the subtidal. Minor phyla generally
were more abundant at lower intertidal (24/0.01 m 2 )
and subtidal depths (10/0.01 m 2 ) than in the upper intertidal (3/0.01 m 2 ). Echinoderms were
absent from the upper intertidal, but had a similar mean abundance in the lower intertidal and
subtidal (21/0.01 m 2 ).
Crustaceans and polychaetes were the most diverse taxonomic groups with mean numbers of
species ranging from 2 to 24 and 0 to 25 across stations, respectively, and overall total means
of 10 to 11 across tide zones (Table 6.3-3). All taxonomic groups generally had fewer species
collected in the upper intertidal compared to lower intertidal and subtidal zones at most stations.
Molluscs were moderately diverse with mean numbers of species ranging from 2 to 10 across
stations and an overall mean of 6 across tide zones. Echinoderms and minor phyla were less
diverse. Mean numbers of species ranged from 0 to 3 for echinoderms and 0 to 6 for minor
phyla across stations; overall total means across tide zones were 1 and 2 for these two
taxonomic groups, respectively.
Molluscs dominated the mean biomass values across depth zones (Table 6.3-4). However,
crustacean biomass values were similarly high or greater at most stations in the upper intertidal
due to the relatively high occurrence of barnacles and weight associated with their calcite shells.
Echinoderms and minor phyla biomass contributions were more localized according to station.
Generally, numbers of species, abundance, and biomass of taxonomic groups were similar
among inner and outer harbor stations with few exceptions. Mean numbers of species and
abundance, particularly crustaceans, ranged higher at outer harbor Stations LARR1 and
LBRR1. A greater number of polychaete species was collected at Station LBRR3, although only
in the subtidal zone. Molluscs contributed to relatively greater biomass values at inner harbor
Stations LARR3 and LBRR2.
6.4.2 Diver Observations
Dominant epifaunal invertebrates included barnacles (e.g., Balanus spp. and Chthalamus
fissus), and mussels (Mytilus galloprovincialis). Other commonly observed crustacean species
included California spiny lobster (Panulirus interruptus), crabs (Mimulus foliatus, Pugettia spp.),
and hermit crabs (Pagurus spp.). Molluscs also included chitons (e.g., Mopalia muscosa),
chestnut cowrie (Cypraea spadicea), gem murex (Maxwellia gemma), Norris's top shell (Norrisia
norrisi), rock scallops (Crassedoma giganteum), scaled wormsnail (Serpulorbis squamigerus),
sea slugs (e.g., Hermissenda crassicornis, Navanax inermis, Peltodoris nobilis), turbon snails
(Tegula spp.), and wavy turbon topsnail (Megastrea undosa).
Relatively common echinoderms included red and purple sea urchins (Strongylocentrotus
franciscanus, P. purpuratus), seastars (Asterina miniata, Pisaster gigartina, P. ochraceous), and
2008 Biological Surveys of Los Angeles and Long Beach Harbors 6–5
April 2010