2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
July 2008, roughly two years after the basin was opened to the ocean, and occurred in the FTB, west
MTB, and MPM.
Other non-native invertebrates documented included the invasive oriental shrimp (Palaemon
macrodactylus). This species is considered established in California, and Ricketts et al. (1968)
proposed that this species was responsible for the disappearance of native species of shrimp Crangon
spp. in some cases. It is generally thought to be introduced by ballast water releases, from which it
spreads to surrounding estuaries planktonically. The Mediterranean mussel (Mytilus galloprovincialis)
was first observed in the FTB during the first survey in October 2007, and was also found during every
quarter in 2008. This non-native species is well established throughout California.
The Japanese mussel (M. senhousia) is another non-native presumed to eventually arrive at Bolsa
Chica. This species settles from the plankton onto soft substrate and can form dense mats of entangled
fibrous threads. This mat and the thousands of mussels that can colonize per square meter can inhibit
the feeding of native filter feeders and the spread of eelgrass. Although there is no evidence of dense
mats having formed at this time at Bolsa Chica, their capture in the fishing nets in October 2007 and
April and July 2008 indicates their presence in the FTB and Muted Pocket Marsh. Cordgrass and
eelgrass transplanted from Upper Newport Bay and the Port of Los Angeles in August 2007 was
observed to have M. senhousia in its roots prior to planting in Bolsa Chica. This species may have
already arrived in the FTB through the settlement of planktonic larvae prior to the transplant of the
cordgrass and eelgrass. There is no effective means to control this species, however it has been
documented that dense, healthy eelgrass beds can inhibit the growth of M. senhousia (Allen and
Williams, 2003).
The non-native bryozoan Zoobotryon verticillatum was observed in July and October 2008 in the
Muted Pocket Marsh and at Station 2, respectively. This species is also well established in southern
California bays and estuaries. It can seasonally grow to great expanses that can reduce the density and
vigor of eelgrass beds, and smother native flora and fauna.
Japanese wireweed (Sargassum muticum) is a seaweed native
to Japan that is widespread in Southern California bays,
commonly found on rock, riprap, or other hard substrate.
This brown alga has been documented to compete with and
displace native species of seaweed and eelgrass by reducing
light through shading. At Bolsa Chica in 2008, the seaweed
has not yet colonized the riprap, rather was observed loose in
the FTB. The holdfasts of the seaweed were secured to highly
motile scallops (A. ventricosus), which were serving as minireefs
for the S. muticum to settle onto and be transported by.
It is likely that hard substrate within the basin will become
Sargassum muticum attached to a scallop.
colonized with S. muticum following future reproductive
events by the population on the scallops. There are no feasible means to control or prevent
colonization by S. muticum, nor is its potential biological impact clearly understood in southern
California. Future field work will also look for Sargassum filicinum, a related species recently
discovered in some southern California bays and estuaries, and at Catalina Island.
Merkel & Associates, Inc. 97