Most of the plants were taken from areas that 

 were disturbed by construction projects at 

 San Diego Bay, then moved to the PERL 

 nursery, planted in trenches that were kept 

 saline and wet, and allowed to expand until 

 new marsh habitats were constructed as 

 mitigation for the earlier damages at San 

 Diego Bay. In spring 1991, a 7-ha (17-ac) 

 excavated marsh at San Diego Bay was 

 transplanted entirely from plants propagated 

 at the original PERL site in a project 

 supervised by the California Department of 

 Transportation. Lower-, middle-, and 

 upper-elevation marsh species were all 

 included in the habitat-creation project. The 

 nursery has been phased out, but the 

 information gained on how to culture native 

 dune and wetland species now guides 

 restoration programs throughout the region. 



6.2.3 Wastewater Wetland Mesocosms 



maximum removal of both nutrients and heavy 

 metals. These findings have broad 

 implications for wastewater management 

 throughout the region. 



Since wastewaters in southern California 

 derive primarily from imported water, their 

 discharge to coastal water bodies artificially 

 adds nutrients (and possibly contaminants), 

 lowers their salinity and alters habitat value 

 for marine and salt marsh species (cf. 

 Chapter 5). Construction of wastewater 

 wetlands upstream of the estuary would 

 improve the quality of the discharge. Use of a 

 twice-daily pulsed-discharge regime would 

 not only improve the water treatment 

 capability of the wetland, it would also reduce 

 the problem of salinity dilution downstream. 

 By timing the discharge to coincide with the 

 twice-daily ebb tides, inflowing fresh water 

 would move quickly through the ocean inlet 

 and damage less of the channel and marsh 

 habitat. 



Complementary funding from the 

 California Sea Grant College and NOAA's 

 Sanctuaries and Reserves Division made 

 possible an innovative wastewater wetland 

 study, which required replicate mesocosms 

 planted with the native bulrush (Scirpus 

 californicus). Twenty mesocosms, each 2.1 

 m 2 , were installed at the new PERL site in 

 December 1989 by Chris Nordby. Each was 

 plumbed with a freshwater inflow from a 

 common tank for mixing simulated sewage, 

 connected to an outflow with a solenoid valve 

 to control the discharge regime, and hooked to 

 a sewer line. Research was conducted by two 

 graduate students (Busnardo 1992 and 

 Sinicrope 1992) and supervised by R. 

 Gersberg, R. Langis and J. Zedler. 



These mesocosms were used to answer two 

 questions about wetlands as wastewater 

 treatment facilities-could manipulating the 

 water levels of a wetland improve nutrient 

 (nitrogen and/or phosphorus) removal 

 efficiency, and would heavy metal removal 

 differ if water levels rose and fell, rather 

 than remaining constant, as in most 

 wastewater wetlands? The results (Busnardo 

 1992; Sinicrope 1992) indicate that a 

 twice-daily discharge regime provides 



6.2.4 Tidal Mesocosms 



The newest mesocosm facilities are being 

 constructed for studies of hydrologic effects on 

 pickleweed (Salicornia virginica) marshes. 

 This plant is the most widespread species of 

 southern California's salt marshes. It 

 occupies sites that are fully tidal, as well as 

 habitat remnants that have not been tidal for 

 many decades. To understand how tidal 

 flushing and freshwater inflows affect this 

 species--and our ability to restore 

 pickleweed habitats at Tijuana Estuary and 

 other coastal wetlands--a manipulative 

 experiment has been planned by J. Zedler, S. 

 Williams and J. Boland. Both the degree of 

 tidal flushing and the presence of freshwater 

 inflows will be controlled and the response of 

 the pickleweed canopy and epibenthic algal 

 mats determined. 



Construction of 24 tidal mesocosms began 

 in 1990, under the supervision of Bruce 

 Nyden, with volunteer Mac McEachern 

 operating the back hoe. All 24 were provided 

 with freshwater irrigation lines to stimulate 

 growth of pickleweed seeds and transplants. 

 Tide gates will control the degree of tidal 



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