California Bulrush Improves Wetland Water Quality

As the social demand for a cleaner and better environment grows, more ecological engineering that incorporates phytoremediating plants will be integrated in the architecture and design of better quality human settlements and other social and sport facilities. Blended into the designed landscape, these plants will add aesthetic values of the design while providing a natural way to remove various pollutants and waste.

California bulrush (Schoenoplectus californicus), also known as giant bulrush, can facilitate removal of some toxic metals from both municipal and industrial pollutants. In wetland construction and reconversion of degraded marshes, this plant helps improve water quality.

California bulrush is a perennial graminoid plant commonly found in marshes, swamps, seeps, lake, washes, floodplains, along lake and stream margins and in wet meadows. It spreads primarily by vegetative propagation, producing new stems from an extensive system of underground rhizomes and, to a limited extent, through seed dispersal. It can grow in relatively deep water of 36 inches or more to produce extensive colonies. When established in conjunction with shorelines, California bulrush provides an effective buffer that dissipates wave energy, reduces shoreline scouring, and traps suspended sediments and other solids. Dense stands of California bulrush are efficient users of available nutrients, producing significant amounts of organic matter. The cumulative effects of organic matter production, sediment trapping and erosion control not only provide shoreline protection, but also accelerate sediment accumulation and near-shore building.

In addition, this plant has been known to provide a favorable habitat for wildlife, including some endangered species.

Removing pollutants from water

In recent years, ecological engineering has been increasingly used to address a broad range of issues, including to better design and architecture of human settlements, to treat pollutants and hazardous waste, to conduct ecological restoration and remediation, and to protect fundamental food production. Constructed wetlands, common around golf courses, are a part of ecological engineering to address a variety of purposes, from restoring degrading wetlands to serving specific functions: buffering valuable aquatic systems from point and non-point sources of pollutants, and as a treatment area to remove toxic metals from wastewater, storm water runoff and chemical runoff. California bulrush, together with other plants such as cattail (Typa angustifolia), has the ability to phytoremediate contaminants from the water and soil (Hawkins et al., 1997; Murray-Gulde et al., 2005).

These plants can take up the hazardous level contaminants, including mercury (Hg), selenium (Se), lead (Pb), zinc (Zn), methyl (Me) and arsenic (As), from the water and soil and translocate them into various organs, such as roots, shoots and leaves. Colonies of California bulrush provide strong interwoven root masses that stabilize sediment surface and soil matrix and prevent erosion and re-suspension of the precipitated contaminants. Vigorous biomass of California bulrush can provide significant binding sites for these harmful elements, allowing these metals to be sequestered in wetland sediments in non-bioavailable forms.

When California bulrush was used in a wastewater treatment, bio-concentration factors (ratio between concentration of metal in the plant and in the water) of 1,911 for Hg, 9,593 for Se and 4,927 for As have been reported (Sundberg-Jones and Hassan, 2007). The ability to tolerate toxic metals varies among plants. In cases where natural vegetation cannot grow due to high levels of metal toxicity, California bulrush can be used as a cover plant to mitigate the problem until favorable conditions are achieved to allow re-establishment of natural vegetation.

Use for erosion control

California bulrush can be used for erosion control along golf course pond and stream shorelines, canal banks, levees and other areas of soil-water interface. Its colonies tend to grow parallel to and continuous along shorelines, or in unobstructed habitats in solid, somewhat circular, stands that may exceed an acre or more. Its stems effectively trap sediment and serve as a buffer to dissipate wave energy, thus enhancing the establishment of other vegetation along the shorelines.

When used as open-water barriers, California bulrush significantly dissipate wave energy, reduces suspended sediments, improves water quality and promotes diverse communities of submerged underwater aquatics. In highly impacted areas, such as Louisiana coastal wetlands where an unprecedented magnitude of coastal marsh loss occurs, better adapted and superior cultivars of California bulrush are needed. It can provide both short- and long-term vegetation.

When properly established and in the appropriate habitat, California bulrush will persist and potentially remain effective indefinitely. California bulrush has a relatively low tolerance to salinity and therefore is generally restricted to fresh and intermediate marsh habitats. Greater salt tolerance in California bulrush will increase its role in reducing coastal erosion control and restoring salt marshes.

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