Salmonellae and shiga-toxin containing E. coli in coastal streams
along the California Coast: Effect of land use. Funded by the USDA. (PI
is Boehm).
Coastal streams that run through agricultural watersheds are suspected to
be major non-point sources of fecal bacteria and zoonotic pathogens
including Salmonella and E. coli O157:H7 to coastal waters. However,
very little work has been done to determine the relationship between
land use and concentrations of these organisms in streams of
California. This project will augment our knowledge of how land use
impacts concentrations of pathogens and fecal pollution in coastal
streams. In particular, our work will elucidate how watershed, physical,
and biological factors control the presence and fate of fecal indicator
bacteria, host-specific fecal markers from Bacteroidales, salmonellae,
E. coli O157:H7 and the shiga-toxin gene (a virulence factor of E. coli
O157:H7 in coastal streams of central California. Field studies are
carried out in coastal streams draining watersheds along the central
California coast with diverse land use characteristics to pin-point how
agricultural land use correlates to the prevalence of these organisms
and their subsequent flux to the coastal ocean. Microcosm studies will
explore how water chemistry and grazers impact the persistence of
different salmonellae serotypes in stream water.
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Sunlight Inactivation of Pathogens along the Urban Coastline: Science to
Improve Policy. Funded by the UPS Foundation.
(PI is Boehm, co-PIs are Kris McNeill, Univ. Minn., and
Kara Nelson, UC Berkeley).
This is a small seed project that aims to test the hypothesis that pathogens and pathogen indicator concentrations are reduced during sunlit
hours and that the mechanism of reduction is injury by ROS, so ROS and associated
measurements will co-vary with concentrations of microbial targets. We
conducted our field project the week of Aug 18 2008 in Avalon, Catalina
Island and are in the process of analyzing samples and modeling the
system.
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Submarine groundwater discharge of nitrogen to urban coastal waters:
Science aimed to improve coastal ecosystem protection. (PI is Boehm, co-PI
is Chris Francis.)
This is a small seed grant to examine how submarine groundwater discharge
influences nitrogen in coastal waters and how nitrogen is transformed in
the subsurface of the beach by denitrifiers, ammonia-oxidizing bacteria,
and ammonia-oxidizing archaea.
Recently, researchers have determined that submarine groundwater discharge
(SGD) may be just as important in transporting nutrients and potentially
other pollutants from the land to the sea as surficial runoff. SGD is
the discharge of saline and fresh groundwater through the land-sea
interface into the coastal ocean. SGD is forced by waves, tides, as well
as seasonal pressure gradients induced by infiltration of precipitation.
In urban southern California, for example, the concentrations of
nitrate and ammonium (collectively referred to as dissolved inorganic
nitrogen, or DIN) in groundwater at the shoreline can be 1000 times higher
than those at nearby watershed outlets. This work is determining
and comparing the flux of nitrogen from watershed outlets and SGD at
Huntington Beach, CA, the quintessential urban beach. We also also looking
at microbially-mediated transformation processes of N in the beach itself.
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Human Contributions to Microbial
Pollution in Hanalei Bay, Kauai. Funded by the National Science
Foundation. (PI is Boehm.)
This work examines the relationships between environmental variables
and the presence of microbial pollutants and human pathogens within
waters at the land-sea interface in a tropical marine environment. The
research will be conducted on the north shore of Kauai adjacent to the
Hanalei River, an American Heritage Designated River. The proposed work
represents a collaboration between the PI and the NSF/NIEHS Pacific
Research Center for Marine Biomedicine (PRCMB) located at University of
Hawaii directed by Dr. Edward Laws. We are undertaking a tiered
approach to microbial source tracking in Hanalei Bay using novel tools
developed as part of the proposed work and at PRCMB. In the first tier, we
characterize near shore water quality in Hanalei Bay and identify
potential sources near the bay using microbial indicators. The first tier
will yield insight into the physical and biological controls on the
abundance and distribution of microbial pollution in Hanalei Bay and will
identify regional scale predictors of unsafe conditions. In the second
tier, we will use source tracking tools as well as assays for human
pathogens to determine if microbial pollutants are from a human source or
represent a human health risk.
The ecology of Vibrio cholerae in San Francisco Bay and the
Pacific Ocean off Central California. Funded in part by NOAA Oceans and Human
Health Initiative. (PI is Boehm).
Studies of Vibrio cholerae diversity have primarily focused on pathogenic
isolates of the O1 and
O139 serotypes. However, autochthonous environmental isolates of this
species routinely display
more extensive genetic diversity than the primarily clonal pathogenic
strains. This bias toward
strains under selection for causing disease has limited our understanding
of diversity and
structure of V. cholerae populations in aquatic habitats. The work
uses
several tools to analyze genomic diversity and gene content distribution
in a novel collection of
V. cholerae isolates from central California coastal waters. By combining
comparative genome
hybridization with DNA microarrays, ERIC-PCR genomic fingerprinting,
multilocus sequence
analysis, and quantitative PCR the work addresses fundamental questions of
importance to
microbial ecologists. These include how does gene content distribution
impact V. cholerae
ecology, how is the coastal V. cholerae population structured, at what
phylogenetic level is
recombination important, and how does diversity vary with time, space, and
niche. Correlations
with environmental variables provide indications of how generation of
diversity and selection for
niche adaptation is influenced by changes in the environment. Ultimately,
decoding these basic
principles may help us toward understanding basic ecological principles of
free-living aquatic
bacteria. While the underlying issues are of particular interest to
microbial ecologists, the
anticipated results will also provide information that can influence
decisions about human
activities near our coastal waters. Runoff can dramatically affect coastal
microbial populations
by altering natural selection toward quickly adapting strains of
bacteria. Diversity in V. cholerae
populations in coastal environments may serve as indicators of shifts in
natural selection and
reveal insights into how pathogenic clones evolve. Using diversity as an
indicator may also
provide a link between anthropogenic impacts and ecosystem health.
Temperature as a controlling variable of microbial pollution and
associated rates of human illness in coastal waters. Funded by NOAA
Oceans and Human Health Initiativa. (PI is Boehm. Co-PIs include Oliver Fringer, Kevin
Arrigo and Gary Schoolnik.)
Understanding submarine groundwater discharge and its influence on coastal
water quality along the California Coast. Funded by NOAA's California Sea
Grant. (PI is Boehm. Co-PI is Adina Paytan. Collaborator is Doug
Mackay.)
The specific aims of this work are to investigate the factors that
modulate submarine groundwater discharge (SGD) and the flux of associated
constituents to coastal waters, and the impact of SGD on coastal water
quality.
We are carrying out directed field, laboratory, and modeling research to
address the four following hypotheses: (H1) SGD, its quality, and the
percentage that is fresh versus saline, is modulated by season, tides, and
wave conditions, (H2) the chemical (nutrient, carbon, trace metal) and
biological (human health indicators) composition of SGD is affected by
land use and geology, (H3) human health indicators and nutrients can be
freely transported through the beach aquifer and are not removed via
interactions with the sediments, and (H4) SGD impacts the water quality of
the nearshore environment at a level comparable to surficial runoff.
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Water, health, and the environment: Childhood survival in Dar es Salaam,
Tanzania. Funded by Woods Institute of the Environment.
(PI is Jenna Davis. Co-PIs are Boehm and Gary Schoolnik.)
During the summer of 2008, field research was carried out with over 300
households in urban and peri-urban Dar es Salaam, Tanzania. We are testing
the hypothesis that providing personalized information to households on
the water quality (as measured by E. coli and enterococci) of water
stored in the home and the cleanliness of their hands (as measured
by E. coli and enterococci collected off hands) will result in
measurable changes in attitudes about water, behavior with respect to
water, illness rates, and even their water quality and hand
cleanliness. The project is being carried out by a dedicated team of
Stanford graduate students including Amy Pickering (IPER), Helena Horak (Medicine),
and Rachelle Strickfaden (CEE), undergraduates including Kristen Rogers,
Jessie Liu,
and Annalise Blum (CEE), and over 20 Tanzanian students (medical, PhD, and
other).
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Beach contributions of pathogens and pathogen indicators to coastal
waters. Funded by NSF's CAREER program.
This research examines beach sand as a non-point, diffuse
source of fecal indicator bacteria (FIB) to coastal waters. FIB have been cultured from the sands of
beaches on all US coastlines raising the possibility that a portion of the
nation's beach advisories are caused by FIB from beach sand. The proposed
work investigates (1) the environmental and human factors that
influence the presence and density of FIB in beach sands, (2) the
association of human pathogens with FIB in beach sands, (3) the potential
for FIB and pathogens to persist for extended periods of time in beach
sand, (4) the mechanisms whereby FIB are transported from the sand to
the coastal ocean, and (5) strategies for reducing densities of FIB and
pathogens in beach sand. Modern tools from microbiology, coastal
oceanography, and groundwater hydrology are utilized in both field and
lab-based inquires in the proposed research.
While the focus of the work is a specific non-point source of
FIB, a goal is to develop a framework for studying non-point FIB sources,
in general. This framework stresses characterization of FIB and pathogen
presence and survivability, transport mechanisms, and remediation
strategies. Another major goal is to develop science to inform best
management practices and policies at the local, national, and
international levels for protecting human health along the
world's coastlines.
Viral transfer between skin and surfaces and quantitative microbial risk
assessment. Funded by an EPA STAR Fellowship to Timothy Julian, PhD
student.
This project examines the transfer efficiency of various viral surrogates
(MS2, phi-X174, fr)
and human viruses (rotavirus and enterovirus) between hands and surfaces. Inputs from these
experiments are used in a model of microbial risk assessment to determine
risks of enteric disease.
Persistence of nucleic-acids in natural waters. Project carried
out by Dr. Sarah Walters.
Through the use of microcosms, we are studying the persistence of
pathogens, pathogen indicators and their nucleic-acids persist in
environmental waters.
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Ecology and diversity of Enterococcus: Applications to their use
as fecal indicators. Project carried out by Blythe Layton.
We are using, microcosms, speciation as well as multi-loci sequencing to study the
ecology and diversity of enterococci from diverse environments (water,
sediments, lacustrine and marine systems).
Groundwater discharge of wastewater contaminants across the land-sea
interface:
Law, policy, and science research aimed to improve coastal
management. Funded by Woods Institute of the Environment. (PI is Boehm,
CO-PIs are Scott Fendorf, Rosemary Knight, and Deborah
Sivas.)
Many coastal communities use on site systems (septic systems) for
treatment of their wastewater. Effluent from septic systems is discharged
to the coastal aquifer where it can raise nutrient and pathogen levels in
the groundwater. Discharge of septic-impacted groundwater to the coastal
ocean is a threat to both human and ecosystem health. The overarching goal
of the proposed work is to generate law, policy, and scientific findings
on submarine groundwater discharge and the fate and transport of
wastewater-derived contaminants in coastal aquifers that will inform
coastal management decisions.
Multi-scale modeling of health behavior choices: Water, sanitation, and
child survival in Africa. Funded by NSF. (PI is Jenna Davis. CO-PIs are
Boehm, Schoolnik, and King.)
This research tests the hypothesis that appropriate
communication of these microbiological test data regarding water quality
and hand cleanliness, along with provision of educational information
regarding links between water, sanitation, hygiene and health, will (1)
increase awareness of health risks from water- and sanitation-related
illness, (2) motivate risk-reducing behaviors among sample households, and
(3) reduce the incidence of water- and sanitation-related disease. Work is
taking place in Dar es Salaam, Tanzania.