title: Enterococcus growth on eelgrass (Zostera marina); implications for water quality.
abstract: Enterococci are fecal indicator bacteria used to monitor fecal pollution of recreational waters. When enterococci levels exceed health standards, fecal pollution is assumed as the cause. Enterococci growing on plants limit their usefulness as fecal indicator bacteria. Here we examined enterococcal growth on eelgrass in Mission Bay, CA where enterococci levels have exceeded water quality thresholds. A total of 69 eelgrass samples were collected from six sites, shaken to remove enterococci attached to plant surfaces and the eluant filtered onto culture media. Isolates were then identified to species using biochemical methods, and DNA typing by pulsed-field gel electrophoresis was done to assess clonality of strains. Enterococci concentrations among eelgrass ranged from 8 to 14 000 CFU g(-1) dry weight. The most predominant enterococcal species found were Enterococcus casseliflavus and E. hirae followed by E. faecalis. Cluster analysis indicated a high level of clonality among isolates across all species, with clonal isolates consistently associated with individual eelgrass samples. Finding high densities of E. casseliflavus, E. hirae and E. faecalis on eelgrass that included clonal strains indicates the capability of enterococcal growth on eelgrass. Amplification of enterococci on eelgrass presents challenges for regulatory agencies that interpret elevated levels of these bacteria as an indication of fecal pollution.
authors.affiliation: Environmental Health Sciences Department, University of California Los Angeles, Los Angeles, CA 90095, USA dferguson@netchino.com.
authors.forename: Donna M
authors.initials: DM
authors.lastname: Ferguson
authors.affiliation: Southern California Coastal Water Research Project, Suite 110, 3535 Harbor Blvd., Costa Mesa, CA 92626, USA.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Weisberg
authors.affiliation: Department of Crop and Soil Environmental Sciences, Virginia Tech, RB 1880, Suite 1129, Blacksburg, VA 24061, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Hagedorn
authors.affiliation: Department of Biology, California State University Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840, USA.
authors.forename: Kristine
authors.initials: K
authors.lastname: De Leon
authors.affiliation: Orange County Public Health Laboratory, 1729 W. 17th St., Santa Ana, CA 92706, USA.
authors.forename: Vida
authors.initials: V
authors.lastname: Mofidi
authors.affiliation: Orange County Public Health Laboratory, 1729 W. 17th St., Santa Ana, CA 92706, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Wolfe
authors.affiliation: Department of Biology, California State University Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840, USA.
authors.forename: May
authors.initials: M
authors.lastname: Zimmerman
authors.affiliation: Department of Civil and Environmental Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Jay
mesh_terms: D002140:California; D016521:Electrophoresis, Gel, Pulsed-Field; D016983:Enterococcus / Q000145:classification* / Q000235:genetics / Q000254:growth & development*; D005243:Feces / Q000382:microbiology; D000068316:Parks, Recreational; D014871:Water Microbiology; D014876:Water Pollution / Q000032:analysis*; D060753:Water Quality; D035962:Zosteraceae / Q000382:microbiology*
keywords: enterococci; environment; fecal indicator bacteria; growth