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

8.0 Eelgrass
surveys. No eelgrass beds were identified within the Port of Long Beach. One area just outside
the Port’s boundary line northeast of Island Grissom was identified as supporting a sizeable
eelgrass bed.
Additional sparse eelgrass beds have been reported within Cabrillo Marina and intermittently in
small narrow linear bands along riprap where suitable depth and conditions exist (Merkel &
Assoc. 2009, pers. comm.). Eelgrass is often displaced by natural and anthropogenic events
(e.g., storms and boat anchoring, respectively) eventually resettling in new areas that may
provide suitable conditions for growth within limited time periods. However, the development
and persistence of such outlying patches is ultimately tied to the stability of the substrate and
sufficient, consistent clarity of the overlying water column.
8.3.3 Eelgrass Characteristics
Leaf blade morphology characteristics and widths were documented for several locations during
the fall surveys to determine whether more than one species of eelgrass was present within the
surveyed beds. Leaf blades collected from the Cabrillo North eelgrass bed (n = 15) were
measured for width. All measured blades were described as flat in cross section consistent with
Zostera marina (as described in Coyer et al. 2007) and overall eelgrass blades had a low
epiphytic load consisting of primarily diatom film and crustose coralline algae.
Recent publications (Coyer et al. 2007, Engle and Miller 2003) confirmed that up to three
species of eelgrass (Zostera spp.) may inhabit various areas of southern California, although
their optimal growth requirements and transport mechanisms are not completely understood.
During the fall diver verification surveys, eelgrass widths and morphology were recorded and
described by a visiting researcher (Dan Martin, University of South Alabama) and he identified
two distinct blade cross sections. Collections were taken from Cabrillo North, Seaplane Lagoon,
and the Mitigation Site. Cabrillo North samples averaged 4.1 mm (n=15) in width and all
displayed a flat blade. In contrast, approximately 30% of all collected samples (n = 25) from the
Seaplane Lagoon and the Mitigation Site had a W-shaped cross section and several displayed a
prominent mid rib. The differences in eelgrass blade morphology suggest that more than one
species of Zostera spp. may exist in the Ports and/or that some degree of hybridization may
have taken place within eelgrass areas surveyed. More in-depth morphological investigations
would be required to fully describe the variations among individual plants and eelgrass beds, but
current findings indicate that eelgrass recruitment or transplantation events may have multiple
sources.
8.3.4 Comparison of 2000 and 2008 Surveys
In general, 2008 delineated eelgrass beds were similar in area and location to those surveyed
during the 2000 baseline survey (Figure 8.3.6). Turion densities from diver transects indicated
that Cabrillo North and South supported the greatest densities and least variable eelgrass areas
while the Pier 300/Seaplane Lagoon Area was variable and patchy in nature (Table 8.3-5, 8.3-6,
and 8.3-7). The greatest turion densities within quadrats from the 2008 surveys were
comparable to densities from the 2000 baseline study using slightly different quadrat placement
methods (Table 8.3-9).
In the previous baseline study (MEC 2002) turion density was estimated by selectively counting
turions within the densest stands of eelgrass for each identified eelgrass community. While
those reported densities provided valuable information on the densest areas of eelgrass within
specific beds they were not representative of the entire area or the majority of the surveyed
eelgrass communities. In contrast, the eelgrass communities were elevated as follows. Density
counts were organized by selecting the most prominent eelgrass beds observed from side-scan
8–10 2008 Biological Surveys of Los Angeles and Long Beach Harbors
April 2010