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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
nearest 0.0001 gram using an analytical balance. All samples were returned to the alcohol solution and
archived for future reference.
Because the benthic monitoring program was intended to broadly characterize the communities of
infaunal organisms within the FTB of Bolsa Chica, species level classification was not deemed
necessary. Rather, data were assembled into logical, higher-order taxonomic groups.
Epifauna
The epibenthic invertebrate sampling program made use of both a
focused quadrat investigation and a more expansive field effort
undertaken as a part of the fish community surveys. For the quadrat
survey, a 1-m 2 quadrat was tossed randomly at each of the sampling
points, and at the two tidal elevations (+1 foot and -2 feet NAVD),
utilized for the infauna coring (Figure 1-11). All epifaunal organisms
present on the surface of the substrate within the quadrat boundary
were identified and counted. Macroalgae present in the quadrat were
also recorded.
Epibenthic quadrat sampling.
Additionally, during the completion of fish studies described above the incidental by-catch of
epibenthic invertebrates was collected, identified, and counted to further enhance the detection of
epibenthic organisms and characterize their distribution, composition, and rough abundance within the
FTB. Because of the incidental nature of these collections, density information was not generated
from the count data.
Only representatives of those organisms that could not be positively identified in the field were
collected for subsequent laboratory taxonomy and voucher collections. These individuals were
preserved in a 10% formalin:seawater mixture and transported to the laboratory for identification.
After approximately one week, organisms were transferred into 70% isopropyl alcohol and identified.
Results
Infauna
In January 2008, nine phyla were collected in the infauna cores, with most taxa represented at both
elevations. Table 1-13 presents the mean density of infauna for the three replicates at each station and
elevation. Polychaetes were the dominant taxa, accounting for 61% of the total abundance. Tanaids
and bivalves were the second and third most abundant (21% and 4% of the total, respectively). Total
density was higher at the –2-foot elevation than at the +1-foot elevation, driven primarily by greater
numbers of polychaetes, amphipods, and tanaids at the lower elevation. Table 1-14 presents the mean
biomass (g/m 2 ) of infauna for the three replicates at each station and elevation in January. Infaunal
biomass in January was dominated by bivalves, gastropods, and polychaetes at all stations.
Merkel & Associates, Inc. 57