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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
anticipated that this basin and the central and east MTBs will have shifts in marsh distribution in the
coming years as all basins are opened to the FTB. The lowest lying areas will be converted to open
water and mudflat, while marsh will be able to expand into areas previously dominated by non-native
weeds once they are eliminated by the salt water influence. The MTBs were designed to support 51.1
ha (126.3 acres) of salt marsh habitat. In 2008 the three basins had a total of 49.8 ha (122.9 acres) of
coastal salt marsh and disturbed coastal salt marsh.
An unanticipated benefit of the restoration work in the
MTBs was the placement of the sidecast excavated
material from tidal channel creation (described above as
disturbed coastal salt marsh). These mounds have been
smoothed by weather and standing water in most areas
and are gradually becoming vegetated at their base with
pickleweed. The elevated mounds serve as a refuge from
tidal inundation and are heavily used at high tide or
during periods of heavy rainfall accumulation by loafing
shorebirds. They are also used by Belding’s Savannah
sparrow’s as elevated perch points, and as they become
vegetated will likely provide additional nesting habitat at
Hundreds of shorebirds loafing on sediment mounds
in flooded marsh in the central MTB.
elevations safe from tidal inundation. Their vegetation by salt marsh will also help to offset losses of
pickleweed at lower elevations due to the introduction of tidal influence. Because these mounds are
comprised only of the sidecast material from channel excavations, they do not have a consequential
effect on the hydrology of the MTBs, but add a valuable habitat element.
Salt marsh distribution is also expected to change on Rabbit Island as low-lying marsh continues to
convert to mudflat. The FTB was designed to eventually support 7.7ha (19.1 acres) of pickleweed. In
2008, approximately 4.9 ha (12.4 acres) of coastal salt marsh were present in the basin, including
Rabbit Island. Salt marsh will be gained at the higher elevations as non-native vegetation continues to
convert to mid and high marsh. Pickleweed on the cordgrass bench in the FTB may continue to fill in
along the base of the riprap in the coming years as well.
The transplant of cordgrass in the FTB was intended to accelerate the development of low salt marsh
habitat, with the goal of providing suitable habitat for light-footed clapper rails (Rallus longirostris
levipes). In 2008, one year post-transplant, the majority of the transplant sites had persisted. By
December 2007, four months post-transplant, most of the planted shoots had senesced and fallen over,
so all shoots mapped and measured in 2008 were new growth. Although only 196 m 2 of cordgrass
were mapped in 2008 (in comparison to the 3,000 m 2 area that was planted), the cordgrass had
expanded within each transplant to become denser, and was healthy, flowering, and dispersing seed.
The slow establishment is typical of cordgrass transplants, but may have been exacerbated by the
prolonged inundation periods that resulted from tidal muting as the flood shoal in the FTB inlet
increased in size, restricting low tide drainage (see Appendix 2-A). Dredging scheduled for January
2009 will improve tidal range and reduce inundation periods at the elevations where the cordgrass was
planted. It is likely that cordgrass at slightly higher elevations on the cordgrass bench will be more
successful. Based on the establishment and expansion rates seen in a similar transplant conducted at
Batiquitos Lagoon, it is expected that the cordgrass will begin to form continuous patches suitable as
habitat within four to five years of transplant (M&A 2009).
Merkel & Associates, Inc. 32