Research

Decadal and Shorter Period                     primarily due to changes in the state and local regulations
                                  governing surf monitoring and reporting (2). In this study,
Variability of Surf Zone Water                   we utilize a 43-yr-long time series of monitoring data and
                                  several short-term high-frequency sampling studies to
Quality at Huntington Beach,                    characterize the decadal and shorter period variability of
                                  surf water quality at Huntington Beach. These data shed
California                             light on how (i) physical and biological phenomena modulate
                                  the impact of coastal pollution on surf water quality, (ii) water
                                  quality at this site has evolved over time and in response to
A . B . B O E H M , †,‡ S . B . G R A N T , * ,†
                                  infrastructure improvements, and (iii) monitoring and
J. H. KIM,† S. L. MOWBRAY,§
                                  reporting of coastal water quality and identification of specific
C. D. MCGEE,§ C. D. CLARK,|
                                  sources of coastal pollution can be improved.
D. M. FOLEY,| AND D. E. WELLMAN|
Henry Samueli School of Engineering, Department of
                                  Methods
Chemical Engineering and Materials Science,
University of California, Irvine, California 92697,         Historical Data: Regulatory Bacteriological Monitoring.
Orange County Sanitation District, 10844 Ellis Avenue,       Marine bathing water regulations in California, and through-
Fountain Valley, California 92728-8127, and             out most of the world, are based on the concentration of
Division of Natural Sciences, Chapman University,          coliform and/or enterococci bacteria in the surf zone where
One University Drive, Orange, California 92866           bather contact is most likely to occur. Since June 1958, the
                                  Orange County Sanitation District (OCSD) and the Orange
                                  County Health Care Agency have measured total coliform
                                  (TC) concentrations at a minimum of six surf zone stations
The concentration of fecal indicator bacteria in the surf      in Huntington Beach (Figure 1). The sampling and laboratory
zone at Huntington Beach, CA, varies over time scales that     methodologies employed in this monitoring effort have
span at least 7 orders of magnitude, from minutes to        remained static, but the number of sites sampled and the
decades. Sources of this variability include historical       sampling frequency at each site have changed over time.
changes in the treatment and disposal of wastewater and       Prior to 1998, surf zone water was assayed for TC only. Briefly,
                                  100 mL of ocean water is collected from an incoming wave
dry weather runoff, El Nino events, seasonal variations
               ˜
                                  at ankle depth in a sterile container, put on ice, and returned
in rainfall, spring-neap tidal cycles, sunlight-induced mortality
                                  to the laboratory within 6 h where 1.0 mL, 0.1, and 0.01 mL
of bacteria, and nearshore mixing. On average, total
                                  are analyzed according to standard method (SM) 9221B.
coliform concentrations have decreased over the past 43
                                  Beginning in July 1998, the analyses were expanded to include
years, although point sources of shoreline contamination
                                  assays for fecal coliform (FC) and enterococci (ENT). Analyses
(storm drains, river outlets, and submarine outfalls) continue   for FC are conducted on 1.0 mL, 0.1 mL, and 0.01 mL of surf
to cause transiently poor water quality. These transient      zone water using SM 9221E; 10-50 mL of sample is assayed
point sources typically persist for 5-8 yr and are modulated    for ENT using EPA Method 1600. From 1958 to 1970, water
by the phase of the moon, reflecting the influence of        samples were collected daily from five locations within the
tides on the sourcing and transport of pollutants in the      beach boundaries: stations 0, 3N, 6N, 9N, 12N, and 15N
                                  (Figure 1). In 1970, stations 21N and 27N were incorporated
coastal ocean. Indicator bacteria are very sensitive to sunlight;
                                  into the monitoring program, and the sampling frequency
therefore, the time of day when samples are collected
                                  was decreased to 3-5 times per week. During 1981 and 1982,
can influence the outcome of water quality testing. These
                                  samples were collected only once per week.
results demonstrate that coastal water quality is forced
                                    Historical Data: Rainfall. Local rainfall data is archived
by a complex combination of local and external processes
                                  on the Orange County Public Facilities and Resource
and raise questions about the efficacy of existing marine
                                  Department Web site (3). We utilized data recorded at the
bathing water monitoring and reporting programs.          Huntington Beach fire station from 1958 through 1999.
                                  Because the fire station rainfall gauge was not maintained
                                  after 1999, we utilized data recorded at nearby Costa Mesa
Introduction                            Water District for 2000 and 2001. Dates and strengths of El
                                  Nino events were retrieved from the National Atmospheric
                                    ˜
Huntington Beach made national news in the summer of
                                  and Oceanic Organization Web site (4).
1999 when a large section of beach, at one point encom-
                                    Historical Data: Analysis. All of the TC and rainfall data
passing 20 km, was closed to the public. Over 1 million people
                                  collected in a given year were divided into a winter period
visit this stretch of beach in a typical summer; therefore, the
                                  (January-February-March, JFM) and a summer period
closures impacted the local economy and contributed to
                                  (June-July-August, JJA). We then calculated the geometric
public concern that surf water quality in California is getting
                                  means and 95% confidence intervals for TC during JFM and
progressively worse (1). Nationally, the number of beach
                                  JJA using data collected at all sites in the study area. The total
advisories and closures nearly doubled from 1999 to 2000,
                                  amount of rainfall recorded during JJA and JFM of each year
                                  was also computed.
 * Corresponding author e-mail: sbgrant@uci.edu; phone: (949)-
824-7320; fax: (949)824-2541.                      The summertime pollution signal was divided into four
 † University of California.
                                  periods of time (events) based on the presence of unique TC
 ‡ Present address: Department of Civil and Environmental
                                  sources that impaired beach water quality for multiple years.
Engineering, Stanford University, Stanford, CA 94305-4020.
                                  During each of the events, water quality in the entire surf
 § Orange County Sanitation District.

                                  zone, or at a subset of surf zone stations, was analyzed for
 | Chapman University.


                © 2002 American Chemical Society                                   3885
10.1021/es020524u CCC: $22.00                    VOL. 36, NO. 18, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY  9
Published on Web 08/14/2002
FIGURE 1. Map of the study area. Red circles represent monitoring stations. Only stations 0, 3N, 6N, 9N, 12N, 15N, 21N, and 27N have
been sampled regularly over the last 43 years. TM and SAR are the Talbert Marsh and Santa Ana River, respectively.

lunar periodicity as follows. The data were binned according      each hour that contained bacteria levels above the detection
to when a sample was collected in the lunar calendar (day        limit.
0 is the full moon). The geometric mean and 95% confidence         Short-Term Studies: Mesocosms. The effect of sunlight
intervals of TC were then calculated for each day of the lunar     on the survival of TC, FC, and ENT was investigated with two
calendar.                                mesocosm studies on October 20 and 27, 2001. Water was
  Short-Term Studies: Twice Daily Sampling. Between          collected from the surf zone at station 9N (Figure 1) at
November 1963 and March 1965, surf zone water sampling         midnight and placed into four 60-L aquariums. Aquariums
was conducted twice daily at stations 0, 3N, 6N, 9N, 12N, and      were placed in a large water bath and maintained between
                                    18 and 19 °C, which is within the temperature range measured
15N, once between 8:00 and 9:00 and again around 14:00.
Samples were collected and analyzed for TC using the same        in the surf zone. Of the four aquariums, two were exposed
standard methods described above for regulatory monitoring.       to sunlight and two were covered with a black tarp. 225-mL
The geometric means of TC in the morning and afternoon         aliquots were removed from each aquarium hourly between
samples were computed.                         4:00 and 23:00 and analyzed for indicator bacteria. The
                                    indicator bacteria in the mesocosms were present in the surf
  Short-Term Studies: Hourly Sampling. TC, FC, and ENT
                                    zone water at the time of collection (i.e., the aquariums were
were measured hourly at four surf zone stations for 2 weeks
                                    not seeded with bacteria). On October 27, samples were
from May 2 to May 16, 2000. 1-L samples were collected at
                                    analyzed for TC using Colilert-18 (IDEXX, Westbrook, MN).
ankle and waist depth on an incoming wave in sterile bottles
                                    On October 20, samples were assayed for FC using SM 9222D
at stations 0, 3N, 100m, and 9N (Figure 1). Within 6 h of
                                    and ENT using both EPA Method 1600 and Enterolert (IDEXX,
collection, samples were analyzed for TC (SM 9221B), FC
                                    Westbrook, MN). Colilert-18 and Enterolert are defined
(SM 9221E), and ENT (EPA Method 1600). In addition, solar
                                    substrate tests implemented in a 97-well quanti-tray. Detec-
irradiance was recorded every 30 min with a thermopile
                                    tion limits were 10 mpn/100 mL for IDEXX methods and 1
radiometer (Kipp & Zonen, CM3 Thermopile Radiometer,
                                    mpn/100 mL for others. On both days, UV intensity was
The Netherlands) located at the San Joaquin Marsh, 6 km
                                    recorded hourly with a UV Minder handheld radiometer
west of Huntington Beach.
                                    (Apprise Technologies, Duluth, MN). On October 20, peroxide
  Data collected during the 2-week study were binned
                                    levels were monitored in both light and dark aquariums
according to the hour of day when they were collected, and
                                    utilizing an enzyme-mediated fluorescence decay method
the geometric means and 95% confidence intervals of
                                    with horseradish peroxidase and scopoletin (5).
indicator bacteria, and average and standard deviation of
                                      Short-Term Studies: Ten-Minute Sampling. TC, Escheri-
solar irradiance measurements were calculated for each hour.
                                    chia coli (EC, a subset of FC), and ENT levels were measured
Concentrations below the detection limit were set equal to
                                    every 10 min at shoreline stations 0, 3N, 6N, 7N, 8N, 9N, and
the lower limit of detection (10 most probable number (mpn)/
100 mL). We also calculated the percent of samples collected      12N (Figure 1) for 12 h from 21:00 September 14 to 9:00

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FIGURE 2. The 43-yr history of water quality at Huntington Beach, CA. The geometric means and 95% confidence intervals of total coliform
(TC) bacteria during January-February-March (JFM) (top panel) and June-July-August (JJA) (bottom panel) calculated using all
samples collected within study site. Total rainfall is shown in blue. El Nino events are designated by gray bars; strong and weak events
                                      ˜
are labeled (+) and (-), respectively, while average events are not labeled. A time line of important events is shown beneath the graph.
Red lines in bottom panel delineate specific contamination events in the JJA signal and are discussed in the text. SAR and OCSD are
acronyms for the Santa Ana River and the Orange County Sanitation District. This graph summarizes 33 910 TC (approximately 400 per
GM) and 743 rainfall measurements.

September 15, 2001. Samples were collected from ankle depth      storms in February. The raw sewage flowed into the ocean
on an incoming wave in a sterile bottle every 10 min and       from the Santa Ana River and caused some of the highest TC
immediately stored on ice. Samples were transported to the      levels ever recorded at Huntington Beach (compare TC levels
laboratory within 6 h and assayed for TC, EC, and ENT using      in top panel to historical time line at bottom of Figure 2).
Colilert-18 and Enterolert (IDEXX).                  Little rain falls in the study area during the summer, and
                                   consequently, TC and rainfall do not correlate during JJA (r2
                                   ) -0.15).
Results and Discussion
                                     To determine how water quality at Huntington Beach
Historical Data: Infrastructure Changes and Seasonal
                                   has changed over time, we performed linear regressions
Variability. Forty-three years of historical monitoring data
                                   between the seasonal (JFM or JJA) geometric mean of TC
at Huntington Beach is summarized in Figure 2. The top and
                                   and the year. The regression slopes indicate that water quality
bottom panels show the geometric means and 95% confi-
                                   at Huntington Beach has improved over the past 43 years
dence intervals of TC (black) and total rainfall (blue) during
                                   (slopes and 95% confidence intervals of m ) -2 ( 6 and -0.3
winters (JFM) and summers (JJA), respectively. On average,
                                   ( 0.4 mpn/100 mL each year for JFM and JJA, respectively).
the geometric mean of TC during JFM is three times greater
                                   However, this overall improvement is biased by the dramatic
than the geometric mean of TC during JJA. Furthermore,
                                   improvement in water quality that resulted from the con-
during JFM the log mean of TC is correlated with rainfall (r2
                                   struction of the new wastewater outfall in 1971 (see discussion
) 0.6), and the peak TC values align with El Nino events
                           ˜
                                   below). If we regress only data collected after the outfall’s
(gray bars in top panel of Figure 2). While TC events appear
                                   construction, the results suggest that TC concentrations have
to coincide with El Nino events, the converse is not true; i.e.,
            ˜
                                   been slowly rising over time (m ) 2 ( 3 and 0.2 ( 0.4 mpn/
not all El Nino events coincide with elevated TC in the surf
       ˜
                                   100 mL each year for JFM and JJA, respectively).
zone. Hence, the relationship between El Nino events, local
                       ˜
                                     The summertime TC signal at Huntington Beach is
rainfall, and coastal pollution is not straightforward. This
                                   characterized by a series of contamination events that persist
region of southern California has separate storm and sanitary
                                   for 5-8 years (red arrows in JJA panel of Figure 2). The
sewer systems, and both can contribute to surf zone pollution
                                   probable causes of these events were reconstructed from
during storms (6, 7). During the winter of 1969, for example,
                                   written records maintained by OCSD and from interviews
OCSD records indicate that upstream sewage treatment
                                   with their staff. From 1954 until 1971, OCSD discharged a
plants discharged raw sewage into the Santa Ana River during

                                                                   3887
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mixture of primary and secondary treated sewage that was        tides when the tidal prism extends farther inland and greater
intermittently chlorinated into the ocean through a 2.1 km       volumes of water are exchanged with the ocean (8, 9). The
long outfall that terminated directly offshore of Huntington      recent dry weather contamination at Huntington Beach
Beach. On the basis of evidence that the original outfall was      (event 4), which appeared abruptly in 1997, has a lunar pattern
impacting the beach (e.g., the frequent sighting of grease),      that is unlike events 1-3 (compare lunar patterns in Figure
the local Water Pollution Control Board issued a cease and       3, panels A and B). TC, FC, and ENT levels all peak a couple
desist order that required OCSD to improve sewage treatment       days before the new moon spring tide and again around the
and disposal in 1961. In 1965 a new diffuser was installed on      full moon spring tide (Figure 3B). The center of the recent
the end of the outfall pipe to increase the near-field mixing      contamination is located 2-3 km north of the Santa Ana
of the sewage field. Instead of improving local surf zone water     River mouth (around 6N and 9N, see Figure 3C) and
quality, however, the concentration of TC during JJA increased     shoreward of a short (700 m) thermal outfall operated by a
abruptly and remained high until the short outfall was         872 MW power generating station. Investigations are currently
replaced with a longer (7.5 km) outfall in 1971 (event 1 in       underway to determine if the thermal outfall is a source of
Figure 2). The construction of the new outfall was supported      fecal indicator bacteria. The fact that each pollution event
by a grant from the Federal Clean Water Act program, and        is characterized by a unique lunar signature raises the
hence this appears to be a case where federal investment in       intriguing possibility that sources of coastal pollution might
point source control led to measurable improvement in          be identifiable based on their lunar patterns. For example,
receiving water quality. The improvement in JJA water quality      the contamination of a surf zone by sewage released from
that occurred after construction of the new outfall is probably     an offshore outfall might be characterized by elevated
more dramatic than appears in Figure 2 because the time of       concentrations during neap tides (event 1).
day when surf zone samples were collected shifted from early         Short-Term Studies: Hourly Variability. Concentra-
afternoon (before 1971) to early morning (after 1974). In the      tions of indicator bacteria in the surf zone at Huntington
twice daily sampling experiments conducted at Huntington        Beach exhibit diurnal variability based on a study in which
Beach from 1963 to 1965, OCSD personnel found that, on         TC, FC, and ENT were measured hourly at four shoreline
average, surf zone samples collected early in the morning        stations for 2 weeks during May 2000. Figure 4A shows the
had TC concentrations twice that of samples collected in the      geometric means and 95% confidence intervals for all samples
early afternoon. (The geometric means of TC measured in         collected each hour of the day (bottom panel), the percent
the morning and afternoon samples were 250 mpn/100 mL          of samples collected each hour that were above the detection
and 100 mpn/100 mL (n ) 294), respectively.) As will be         limit of 10 mpn/100 mL (middle panel), and the average
documented later in the paper, at least part of this time-       solar radiation each hour (top panel). The concentration of
of-day sampling effect is due to sunlight-induced mortality       indicator bacteria and the percentage of samples that tested
of indicator bacteria.                         positive for indicator bacteria are both highest in the middle
                                    of the night; as solar radiation peaks at midday, the
  The next two JJA contamination events in Figure 2 appear
                                    concentration of indicator bacteria falls to levels near or below
to have been caused by dry weather flows from a storm drain
                                    the detection limit.
at the northeast end of the study area near station 21N (event
2) and from the mouth of the Santa Ana River (event 3).           The diurnal trend noted above is due, at least in part, to
Presently, contamination at Huntington Beach is centered        sunlight-induced bacterial die-off or injury. In a set of
between surf zone stations 6N and 9N (event 4). All four JJA      unseeded mesocosm experiments (Figure 4B), the concen-
contamination events are discussed in more detail below.        trations of ENT, FC, and TC in isolated samples of surf zone
                                    water exposed to sunlight dropped below detectable levels
  Historical Data: Lunar Variability. Lunar variability in
                                    by noon (open symbols) but remained elevated throughout
surf zone water quality may arise if the loading and/or
                                    the day in samples of the same water kept in the dark (closed
nearshore transport of contamination is modulated by the
                                    symbols). Photolysis of organic material in the sunlight-
tides. Possible examples include the tidal flushing of estuaries
                                    exposed surf zone water caused peroxide levels to increase
and storm channels (8, 9), tidally modulated nearshore
                                    to 400 nM (blue open circles in top panel in Figure 4B) (16).
circulation patterns (10, 11), foreshore washing of contami-
                                    These data confirm earlier reports that sunlight accelerates
nated beach sand by wave action, exfiltration of sewage-
                                    the die-off and injury of indicator bacteria in marine waters
contaminated groundwater by tidal pumping (12), and
                                    (17-19) and raise the possibility that peroxide and other
horizontal and vertical movement of offshore wastewater
                                    photochemically produced oxidants may play a role in this
fields by internal tides (13, 14). To determine if the pollution
                                    process, as has been suggested previously for coliform die-
events at Huntington Beach exhibit lunar variability, geo-
                                    off in sewage fields (19).
metric means and 95% confidence intervals of indicator
                                       The data presented in Figure 4A raise an equally important
bacteria were plotted against the day since the full moon
                                    question: Why is the surf zone so rapidly resupplied with
(Figure 3A,B) following an approach used by Pineda (15) to
                                    indicator bacteria after the sun goes down? There are several
examine tidally forced nearshore upwelling. TC concentra-
                                    possible explanations. (i) During daylight hours a substantial
tions in the surf zone were higher during the neap tide after
                                    fraction of indicator bacteria in the surf zone are injured,
the new moon (around day 20) from 1964 to 1970 when the
                                    and these organisms are resuscitated by photoreactivation
source was discharge from the short outfall (event 1); there
                                    and/or dark-repair mechanisms (20, 21). (ii) Indicator bacteria
is no obvious lunar pattern at station 21N from 1972 to 1981
                                    are rapidly growing in the surf zone, and after dark their
when the source was dry weather runoff from a storm drain
                                    growth outpaces their removal by die-off and bacteriovory.
(event 2); and TC levels at station 0 were highest during spring
                                    (iii) There is a more or less continuous supply of indicator
tides (around days 0 and 15) from 1983 to 1990 when the
                                    bacteria to the surf zone from onshore or offshore sources
source was outflow from the Santa Ana River (event 3). The
                                    of pollution. (iv) There is a large reservoir of indicator bacteria
lunar pattern for event 1 might reflect less overall dilution
                                    in the foreshore and nearshore sediments that are continu-
of the sanitation district sewage field during neap tides, for
                                    ously resuspended by wave action.
example, because of less energetic tidal-band nearshore
currents. The absence of a clear lunar pattern for event 2 is        In the mesocosm experiments described above, we found
consistent with a more or less steady input of dry weather       that the concentration of indicator bacteria declined after
runoff from a storm drain. The spring tide lunar pattern        isolated samples of surf zone water from Huntington Beach
evident for event 3 can be explained by increased transport       were exposed to sunlight. Importantly, the concentration of
of contaminants out of the Santa Ana River during spring        indicator bacteria in the mesocosms did not rebound after

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FIGURE 3. (A) Geometric means (GM) (solid lines) and 95% confidence intervals (dashed lines) of TC as a function of day in the lunar
cycle measured during JJA from 1964 to 1970 (event 1) at monitoring stations 0, 3N, 6N, 9N, 12N, and 15N (21N and 27N were not utilized
during this period) (top panel), from 1972 to 1981 (event 2) at station 21N (middle panel), and from 1983 to 1990 (event 3) at station 0 (bottom
panel). The lunar phase is indicated at the top of the graph (O and b are full and new moons, respectively). (B) GMs and 95% confidence
intervals of TC (red), FC (green), and ENT (black) during JJA from 1998 to 2001 (event 4) at monitoring stations 0, 3N, 6N, 9N, 15N, 21N,
and 27N as a function of day in the lunar cycle. The average tide range (defined as the daily difference between the high-high and the
low-low tide) and standard errors are shown in blue. (C) The spatial distribution of the lunar signal at Huntington Beach during JJA
from 1998 to 2001 (event 4). The number of data points used to calculate each lunar plot is indicated next to the curves.

sunset. This result does not support the idea that bacterial       (data not shown). Between 6N and 9N an ENT pulse ap-
reactivation and/or growth is the cause of surf zone           pears to propagate in a northeast direction at approxi-
replenishment (hypotheses i and ii above). The possibility        mately 0.3 m/s (dashed line in the figure), consistent with
that indicator bacteria are continuously entrained in the surf      an earlier measurement of littoral drift velocities at Hun-
zone from onshore and offshore sources (hypothesis iii) seems       tington Beach during similar wave conditions (8). Assuming
likely given what is already known about this system (8, 9,        a littoral drift velocity of 0.3 m/s and a maximum pulse
14). Foreshore sediments, on the other hand, appear to have        duration of 80 min, we estimate that individual pulses of
relatively low concentrations of fecal indicator bacteria (8),      ENT in the surf zone are less than 1.4 km in length. The
and hence particle resuspension is probably not responsible        results of a dye study (8) indicate that one rip cell in Hun-
for the rebound of bacteria after sunset (hypothesis iv).         tington Beach is approximately 800 m in length, and thus,
  Short-Term Studies: Ten-Minute Variability. The vari-         the pulse size is on the order of the distance between rip
ability of surf zone water quality extends to time scales shorter     cells. This observation is consistent with the idea that pulses
than 1 h based on results of a study in which surf zone samples      of indicator bacteria originate when contamination from
were collected every 10 min for 12 h at six shoreline sites        intermittent onshore or offshore sources is mixed into the
(Figure 5). Coherent pulses of ENT are evident in these time       surf zone by rip cell currents (8, 22). If this is the case, then
series, although they are quite short-lived (<80 min); similar      high-frequency variability should not be unique to Hun-
high frequency variability is evident in the TC and EC signals      tington Beach as rip currents are a universal characteristic

                                                                       3889
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FIGURE 4. (A) Results from the hourly 2-week sampling program from May 2-16, 2000. A total of 6336 TC, FC, and ENT measurements
were sorted according to the time of day they were collected. Shown are the percent of samples above the detection limit of 10 mpn/100
mL (middle panel), and the geometric mean and 95% confidence intervals of indicator bacteria (bottom panel). The average solar irradiance
and standard error for each hour are shown in the top panel. (B) Results from mesocosm experiments on October 20 (circles and triangles)
and 27 (squares), 2001. TC, FC, and ENT concentrations as a function of time in aquariums exposed to sunlight (open symbols) and covered
with a black tarp (closed symbols) are shown in the second, third, and fourth panel from top, respectively. For ENT, concentrations
determined using EPA Method 1600 and Enterolert are designated by circles and triangles, respectively. In the top panel, UV intensity
on both days (black) is shown along with the concentration of H2O2 (blue) measured in one light (open circles) and one dark (solid circles)
aquarium on October 20.




FIGURE 5. ENT concentrations measured during 10-min sampling from 21:00 on September 14, 2001, to 9:00 on September 15, 2001, at six
surfzone stations. Concentrations in excess of 35 mpn/100 mL are indicated by filled portions of the curves. This plot summarizes a total
of 584 ENT measurements.

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FIGURE 6. Surf zone water quality at Huntington Beach varies over time scales that span at least 7 orders of magnitude, from minutes
to decades.

of wave-dominated beaches (22). It should be noted that       bacteria. On the basis of all the measurements made during
resuspension of sediments by wave-driven turbulence and       the hourly and 10-min sampling programs conducted as part
precision limits associated with biological assays might also    of this study, we calculate that at least 70% of the single-
                                  sample exceedences last less than 1 h (n ) 86) and at least
contribute to the intermittent character of the bacterial signal.
                                  40% last less than 10 min (n ) 28). Even if indicator bacteria
  Implications. The results presented above can be un-
                                  could be detected instantaneously, the high-frequency
derstood within the conceptual framework illustrated in
                                  character of the bacterial signal in the surf zone would result
Figure 6. At the finest scale, the pollution signal in the surf
                                  in the untenable situation where beach postings would have
zone consists of individual contamination pulses that last
                                  to be updated on a minute-by-minute basis.
on the order of 100 min or less. These pulses may be generated
when intermittent sources of pollution (e.g., ebb flow from       (ii) The geometric mean standard, in which the geometric
rivers and estuaries or cross-shelf transport of offshore      mean of multiple samples collected over a specified window
wastewater fields) are mixed into the surf zone by rip cells.    of time is used to make decisions about beach postings or
The frequency with which bacterial pulses appear in the surf    closures, may represent a better way of assessing beach water
zone and their magnitude are modulated by a number of        quality as compared to the single-sample standard. Future
different processes operating over many time scales including    research should focus on refining marine bathing water
the rise and fall of the sun, phase of the moon, change of     standards to determine the optimal number of samples and
season (JJA vs JFM), El Nino events, and changes in the
                ˜                  days over which to calculate the mean. Currently, California’s
treatment and disposal of wastewater and dry weather runoff.    geometric mean standards (35, 200, and 1000 mpn or cfu/
The lunar variability patterns are interesting because they     100 mL for ENT, FC, and TC, respectively) are based on a
suggest an underlying mechanism for the delivery and mixing     30-day averaging window.
of pollutants in the coastal ocean and may may also prove        (iii) Fecal indicator bacteria in the surf zone are strongly
useful for fingerprinting specific types of point and nonpoint   affected by sunlight and possibly its secondary effects (e.g.,
sources of coastal pollution.                    photochemically produced oxidants). Hence, the time a
  The variability documented in this paper has immediate     sample is collected can dramatically influence the concen-
practical implications for the monitoring and mitigation of     tration of indicator bacteria detected. This observation has
coastal pollution:                         several important implications. First, routine water quality
                                  monitoring programs should, at a minimum, collect samples
  (i) Decisions to post or close a beach should not be based
                                  at the same time every day, ideally early in the morning before
on the concentration of indicator bacteria in a single grab
                                  sunlight has had a chance to reduce bacterial concentrations.
sample. In many coastal areas of the United States, warning
                                  Early morning sampling is justified both because it represents
signs are posted on public beaches if the concentration of
                                  a conservative approach (i.e., the concentration of bacteria
indicator bacteria in a single sample exceeds a set of single-
                                  in the morning is likely to be higher than at mid-day) and
sample standards. For example, in California, the single-
                                  because human viruses, which can also be associated with
sample standards for ENT, FC, and TC are respectively 104,
                                  sewage-contaminated coastal waters, are more resistant than
400, and 10 0000 mpn or colony forming units (cfu) per 100
                                  bacteria to sunlight (25). Second, spatial surveys intended to
mL; a lower single-sample standard for TC of 1000 mpn or
                                  isolate sources of coastal pollution should carefully take into
cfu per 100 mL applies when the TC/FC ratio falls below 10.
                                  account potential artifacts associated with collecting samples
There is generally a 24-96-h delay between when a sample
                                  at different times of the day. For example, apparent spatial
is taken and when the testing results are known. Hence, if
                                  gradients in the concentration of fecal indicator bacteria may,
a surf zone sample exceeds one of the single-sample
                                  in fact, reflect when during the day different samples were
standards, it is likely that the pollution event that caused the
                                  collected.
exceedence will have passed by the time a sign is posted.
Indeed, a study of Los Angeles daily monitoring data found       (iv) Despite public perceptions to the contrary (1), beach
that 70% of single-sample exceedences lasted 1 day or less     water quality has actually improved over time. The record
(23), and similar results were reported for beaches along      at Huntington Beach indicates that large-scale investment
Lake Michigan (24). This problem cannot be resolved solely     in waste treatment and disposal infrastructure has had a
by developing more rapid methods of detecting indicator       positive effect on coastal water quality over time. It is also

                                                                   3891
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interesting to note that it takes, on average, 5-8 yr to identify    (6) Schiff, K. C.; Weisberg, S.; Dorsey, J. Environ. Manage. 2001, 27,
                                       149.
and mitigate small-scale point sources of shoreline pollution,
                                     (7) Schiff, K. C.; Morton, J.; Weisberg, S. Mar. Environ. Res. (in press).
for example, storm drains. Perhaps better coordination
                                     (8) Grant, S. B.; Sanders, B. F.; Boehm, A. B.; Redman, J. A.; Kim,
between governmental agencies responsible for monitoring,          J. H.; Mrse, R. D.; Chu, A. K.; Gouldin, M.; McGee, C. D.; Gardiner,
regulating, and mitigating coastal pollution would reduce          N. A.; Jones, B. H.; Svejkovsky, J.; Leipzig, G. V.; Brown, A. Environ.
this overall response time.                         Sci. Technol. 2001, 35, 2407.
                                     (9) Sanders, B. F.; Green, C. L.; Chu, A. K.; Grant, S. B. J. Hydraul.
Acknowledgments                               Eng. 2001, 127, 795.
                                    (10) Winant, C. D.; Olson, J. R. Deep-Sea Res. 1976, 23, 925.
This work was supported by the National Water Research
                                    (11) List, E. J.; Winant, C. D. J. Hydraul. Eng. 1990, 116, 1158.
Institute (NWRI) (EC 699-632-00) and matching funds from        (12) Paul, J. H.; Rose, J. B.; Jiang, S. C.; Zhou, X.; Cochran, P. K.;
the Santa Ana Regional Water Quality Control Board; The           Kellog, C.; Kang, J. B.; Farrah, S.; Lukasik, J. Water Res. 1997, 31,
County of Orange Sanitation District, Orange County; and           1448.
the Cities of Huntington Beach, Santa Ana, Costa Mesa,         (13) Petrenko, A. A.; Jones, B. H.; Dickey, T. D.; Hamilton, P. Cont.
                                       Shelf Res. 2000, 20, 1.
Fountain Valley, and Newport Beach. A.B.B. was supported
                                    (14) Boehm, A. B.; Sanders, B. F.; Winant, C. D. Environ. Sci. Technol.
by a University of California Faculty Fellowship, J.H.K. was
                                       2002, 36, 1899.
supported by an NWRI graduate fellowship, C.D.C. was          (15) Pineda, J. Cont. Shelf Res. 1995, 15, 1023.
supported by the Office of Naval Research (N000140110609),       (16) Cooper, W. J.; Zika, R. G.; Petasne, R. G.; Fischer, A. M. In Aquatic
and D.M.F. and D.E.W. were supported by W. M. Keck              humic substances: Influence on fate and treatment of pollutants;
Foundation. We gratefully acknowledge three anonymous            Suffet, J., MacCarthy, P., Eds.; American Chemical Society:
                                       Washington, DC, 1989; p 219.
reviewers and the hundreds of people involved in the
                                    (17) Fujioka, R. S.; Hashimoto, H. H.; Siwak, E. B.; Young, R. H. Appl.
collection of the data described in this paper. Special thanks
                                       Environ. Microbiol. 1981, 41, 690.
to the following institutions and individuals: URS Greiner
                                    (18) Sinton, L. W.; Finlay, R. K.; Lynch, P. A. Appl. Environ. Microbiol.
Woodward-Clyde, Sierra Laboratories, B. Sanders, R. Linsky,         1999, 65, 3605.
C. Crompton, R. Reeves, L. Grant, K. Willis, M. Mazur, L.        (19) Chamberlain, C. E.; Mitchell, R. In Water Pollution Microbiology;
Honeybourne, S. Jiang, J. Fuhrman, S. Weisberg, C. Poor,           Mitchell, R., Ed.; John Wiley and Sons: New York, 1978.
and K. Theisen.                             (20) Oguma, K.; Katayamam, H.; Mitani, H.; Morita, S.; Hirata, T.;
                                       Ohgaki, S. Appl. Environ. Microbiol. 2001, 67, 4630.
                                    (21) Sommer, R.; Lhotsky, M.; Haider, T.; Cabaj, A. J. Food Protect.
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