title: Beach nourishment impacts on bacteriological water quality and phytoplankton bloom dynamics.
abstract: A beach nourishment with approximately 1/3 fine-grained sediment (fines; particle diameter <63 μm) by mass was performed at Southern California's Border Fields State Park (BFSP). The nourishment was found to briefly (<1 day) increase concentrations of surf-zone fecal indicator bacteria (FIB) above single-sample public health standards [104 most probable number (MPN)·(100 mL)(-1)] but had no effect on phytoplankton. Contamination was constrained to the nourishment site: waters 300 m north or south of the nourishment were always below single-sample and geometric mean [≤ 35 MPN · (100 mL)(-1)] standards. Nourishment fines were identified as a source of the fecal indicator Enterococcus ; correlations between fines and enterococci were significant (p < 0.01), and generalized linear model analysis identified fines as the single best predictor of enterococci. Microcosm experiments and field sampling suggest that the short surf-zone residence times observed for enterococci (e-folding time 4 h) resulted from both rapid, postplacement FIB inactivation and mixing/transport by waves and alongshore currents. Nourishment fines were phosphate-rich/nitrogen-poor and were not correlated with surf-zone phytoplankton concentrations, which may have been nitrogen-limited.
authors.affiliation: Scripps Institution of Oceanography, La Jolla, California 92093, United States. mrippy@ucsd.edu
authors.forename: M A
authors.initials: MA
authors.lastname: Rippy
authors.forename: P J S
authors.initials: PJ
authors.lastname: Franks
authors.forename: F
authors.initials: F
authors.lastname: Feddersen
authors.forename: R T
authors.initials: RT
authors.lastname: Guza
authors.forename: J A
authors.initials: JA
authors.lastname: Warrick
mesh_terms: D001493:Bathing Beaches; D002140:California; D016983:Enterococcus / Q000302:isolation & purification; D010839:Phytoplankton / Q000302:isolation & purification*; D014871:Water Microbiology; D060753:Water Quality