1

Measurement of Multiple Microbial Indicators

at two Miami-Dade County Beaches

Tomoyuki Shibata, M.S.

Dept of Civil, Arch., and Environmental Engineering

University of Miami

2

[Abstract]The objectives of this study are to compare multiple microbial indicators

(enterococci, fecal and total coliform, C. perfringens and E. coli) to determine if they correlate with one another and preliminarily assess sources of contamination.

The study was conducted within two beaches in Miami-Dade County, FL: Hobie & Crandon Beach. Monitoring was conducted in three phases: daily water monitoring, beach sand sampling, and spatially intense water sampling.

Results of the daily monitoring indicated that different indicators provide conflicting results concerning beach water quality. For example, at one site the monthly averages for enterococci were 81/100 ml during the dry month and 55/100 ml during the wet month, which exceeded the USEPA criterion of 35/100 ml. On the other hand, the monthly averages for fecal coliform were considerably lower than the Florida guideline of 200/100 ml.

The results of the sand sampling at 27 points in Hobie Beach showed significant differences in microbe concentrations with different sand conditions. These conditions were sand under seaweed, uncovered sand, and submerged sand. For instance, the largest numbers of C. perfringens were observed in submerged sand, intermediate numbers were observed in sand under seaweed and the smallest numbers in uncovered sand (p = 0.0044 ~ 0.3721). These results suggested that beach sand may not be main source of C. perfringens and that sunlight exposure may influence the concentrations.

The results of the spatially intense water sampling at 58 points around Hobie Beach indicated that significantly higher numbers of microbes were observed near the shoreline than for samples collected offshore (p < 0.05). Comparatively large numbers of microbes were observed at east end of Hobie Beach at high tide. l data inclusive, any strong correlation was not observed between indicator microbes and

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[Background]• Role of Indicator Microbes for Recreational Water:

– If large numbers of indicator microbes are detected in water body The water body is assumed to be contaminated by human waste

Since the microbes exist in human feces in high concentration.Thus, it’s unsafe for recreational use.

• Questions: Are they reliable?– The studies to establish EPA criteria were conducted in the northern area of

the United States. Thus, the criteria may not be suitable for tropical environment.

– E. coli and enterococci exist in the natural environment. – Total coliform multiply in tropical environment.

• New Face: C. perfringens (utilized by Hawaii)– Advantages: Behave similar to enteric viruses and does not multiply in the

natural environment. – Disadvantages: Tolerate to chlorine disinfection and the studies to establish

Hawaiian guideline did not include epidemiological consideration.

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[Study Sites]: Hobie and Crandon Beach in Miami-Dade County

Hobie Beach: Located in the southern portion of Biscayne Bay.• Poor water circulation.• Dogs allowed, seaweed over a very silty, muddy floor.

Crandon Beach: Located about 2.5 miles southeast of Hobie Beach. • Well managed beach compared with Hobie Beach.

HobieBeach

CrandonBeach

Miami Mainland

VirginiaKey

KeyBiscayne

HobieBeach

CrandonBeach

Miami Mainland

VirginiaKey

KeyBiscayne

MiamiSeaquarium

CDWWTP

Ocean Outfall from CDWWTP

University of Miami Marine School

Bear Cut

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[Analytical Methods]• Microbes

– Enterococci: 1) Membrane filter (MF) method (USEPA 1997)

2) Chromogenic substrate method (sold by IDEXX)

– Fecal coliform: MF method (APHA 1995)

– C. perfringens: MF method (USEPA 1995)

– Total coliform & E. coli: IDEXX method

• Physical-Chemical Parameters

– Turbidity: TD-40 nephelometer (Turner Design, Sunnyvale, CA)

– Salinity: Model 4081 EC meter (Amber Science, Eugene, OR)

– pH: Model 525 A pH meter (Orion, Beverly, MA)

– Temperature: Mercury Thermometer

Laser Thermometer MiniTemp MT4 (ReyYek, Santa Cruz, CA)

• Others: Data Retrieval

– Tide: National Ocean and Atmospheric Administration (NOAA)

– Rainfall: National Climate Dada Center (NCDC)

South Florida Water Management District (SFWMD)

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[Daily Water Sampling] H1,H2,C1 and C2

• Dry Month (March 10 ~ April 9, 01)

• Wet Month (July 11 ~ August 10, 01)

OUTFALL2SQM3

OUTFALL1SQM2

SQM1

H1

SP 12

SP 11

SP 10

1 Km

1 mile

H2

C1

C2

Daily Sampling Stations

DOH sampling stations

DERM sampling stations

RICKENBACKER CY

HBE

Wind SurferBeach

HOBIE BEACH

Miami Seaquarium

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[Beach Sand Sampling] May 29, 01

• Three sand samples at each location (one at Windsurfer Beach and eight at Hobie Beach)

– Sand from under seaweed

– Sand from not covered with seaweed

– Sand from bottom within knee deep water

As Cs

Es

Gs

Is

Ks

MsOs

Qs1 Km

1 mile

Hobie Beach

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[Spatially Intense Water Sampling] 58 points around Hobie Beach

• High tide period (June 25, 01)

• Low tide period (July 2, 01)

TL

SRA1 A2

A3 HBB1

B2

3B

C3

D3

E3

SQ

Q3

Q2

Q1CH

C1C2 D1

D2 E1

E2 F1

F2

F3

G3

G1

G2 H1

H2

H3

I1

I3

J1

J2

J3

K1

K2

K3

L1

L2

L3

M1M2M3

N1

N2N3

O1

O2

O3

P1

P2

P3

HB2

HB3

EX

1 Km

1 mile

Hobie Beach

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Guideline for Marine Recreational Water

FDOH: Florida Dept. of Health

FDEP: Florida Dept. of Environmental Protection

Indicator Microbes Guidelines Guideline or Criteria Developed By:

E. coli

Not recommended for marine waters. For freshwater a geometric mean of 126/100 ml and 235/100 ml on a single day.

USEPA (1986)

Enterococci A geometric mean of 35/100 ml and 104/100 ml on a single day

USEPA (1986) FDOH

Fecal coliform A monthly average of 200/100 ml, nor 400/100 ml in 10% of samples, nor 800/100 ml on any day.

USEPA (1976) FDEP FDOH

Total coliform

A monthly average of neither 1000/100 ml, 1000/100 ml in 20% of samples, nor 2400/100 ml on any day.

USEPA (1976) FDEP

C.perfringens

A geometric mean of 5/100 ml (open ocean) A geometric mean of 50/100 ml (interior waters)

Suggested in Hawaii

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[Results]

{Water Quality Evaluation}

• Each indicator microbe provides different evaluation.

• “Good”: did not exceeded average nor daily maximum guideline.

• “Moderate”:exceeded the daily maximum at least one day but the daily average was below guideline.

• “Poor”:both the average and daily maximum were exceeded.

Sites Enterococci

(MF) Enterococci

(IDEXX) E coli Fecal coliform Total coliform C. perfringens

H1 Moderate Moderate Moderate Good Poor Poor H2 Poor Moderate Poor Good Poor Poor C1 Moderate Moderate Good Good Good Good

C2 Moderate Moderate Moderate Good Good Good

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{Between Sites}

• Indicator microbes concentrations (significant at 95% confidence)

– Hobie Beach >> Crandon Beach.

– H2 >> H1 (except for fecal coliform)

{Daily Changes}• Indicator microbes concentrations varied considerably everyday

• Similar patterns showed but also not consistent all the time.

• Standard deviation of the microbial concentrations Hobie > Crandon Beach.

= Varied largely at Hobie Beach and more stable at lower level at Crandon Beach

• Even though Hobie Beach is considered the more contaminated beach,

it is important to emphasize that it was not always contaminated.

• Water quality of Hobie Beach was known to be often good based on USEPA, FDEP, and FDOH guidelines.

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Site H1

10

100

1,000

10,0003/

10

3/12

3/14

3/16

3/18

3/20

3/22

3/24

3/26

3/28

3/30 4/

1

4/3

4/5

4/7

4/9

CFU

or M

PN/1

00 m

l

ENT(MF)FC(MF)TC (IDX)CP(MF)EC(IDX)

Sewage Spill

Site H2

10

100

1,000

10,000

100,000

3/10

3/12

3/14

3/16

3/18

3/20

3/22

3/24

3/26

3/28

3/30 4/

1

4/3

4/5

4/7

4/9

CFU

or M

PN/1

00 m

l

ENT(MF)FC(MF)TC (IDX)CP(MF)EC(IDX)

Sewage Spill

10

100

1,000

3/10

3/12

3/14

3/16

3/18

3/20

3/22

3/24

3/26

3/28

3/30 4/

1

4/3

4/5

4/7

4/9

CFU

or M

PN/1

00 m

l

ENT(MF) FC(MF)

TC (IDX) CP(MF)

EC(IDX)

Site C1

Sewage Spill

10

100

1,000

10,000

100,000

3/10

3/12

3/14

3/16

3/18

3/20

3/22

3/24

3/26

3/28

3/30 4/

1

4/3

4/5

4/7

4/9

CFU

or M

PN/1

00 m

l

ENT(MF)FC(MF)TC (IDX)CP(MF)EC(IDX)

Site C2

Sewage Spill

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1

10

100

1,000

10,0007/

11

7/13

7/15

7/17

7/19

7/21

7/23

7/25

7/27

7/29

7/31 8/

2

8/4

8/6

8/8

8/10

CFU

or M

PN/1

00 m

l ENT(MF) FC(MF)TC (IDX) CP(MF)EC(IDX)

Site H1

1

10

100

1,000

10,000

100,000

7/11

7/13

7/15

7/17

7/19

7/21

7/23

7/25

7/27

7/29

7/31 8/

2

8/4

8/6

8/8

8/10

CFU

or M

PN/1

00 m

l

ENT(MF)

FC(MF)

TC (IDX)

CP(MF)

EC(IDX)

Site H2

1

10

100

1,000

10,000

7/11

7/13

7/15

7/17

7/19

7/21

7/23

7/25

7/27

7/29

7/31 8/

2

8/4

8/6

8/8

8/10

CFU

or M

PN/1

00 m

l

ENT(MF)FC(MF)TC (IDX)CP(MF)EC(IDX)

Site C2

DateDate

Date Date

1

10

100

1,000

10,000

7/11

7/13

7/15

7/17

7/19

7/21

7/23

7/25

7/27

7/29

7/31 8/

2

8/4

8/6

8/8

8/10

CFU

or M

PN/1

00 m

l

ENT(MF)FC(MF)TC (IDX)CP(MF)EC(IDX)

Site C1

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{Seasonal Changes}• Hypothesis prior to this study

– Numbers of indicator microbes in wet season >> in dry season

due to larger amounts of rainfall, elevated temperatures, and more bather.

• Results: The hypothesis was generally rejected (95% confidence)

– Exception: Total coliform in the wet >> in the dry.

• Conclusion: Numbers of indicator microbes were not effected by seasonal changes.

– Rainfall: 2.87in (dry) << 8.24in (wet)

– Temperature: 25.6°C (dry) << 30.7°C (wet)

– pH: 8.4 (dry) > 8.2(wet)

– Salinity: 34.4 ‰ (dry) >> 30.0 ‰ (wet)

– Turbidity: 4.9ntu (dry) < 5.7ntu (wet)

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{Beach Sand}• All indicator microbes were observed in all beach sand samples.

• Relatively large numbers of indicator microbes were observed at the east end of Hobie beach.

• Some indicator microbes were significantly different in sand conditions (95% confidence).

– Total coliform: under seaweed >> uncovered > submerged

– C. perfringens:submerged > seaweed >uncovered [submerged >> uncovered]

{Spatially Intense Water Quality}• Microbes concentrations in shoreline area >> in offshore area (95% confidence).

• Microbes concentrations during high tide > during low tide.

• Considerably, large numbers of indicators microbes were observed at the shoreline area at the east end of Hobie Beach at high tide. – Enterococci (MF) was 252 CFU/100 ml,

– total coliform was 8,664 MPN/100 ml,

– C. perfringens was 94 CFU/100 ml.

All these numbers were larger than the regulatory.

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0

2 0 0

4 0 0

6 0 0

8 0 0

1 0 0 0

1 2 0 0

A s C s E s G s I s K s M s O s Q s

L o c a t i o n

MPN/

100

ml

S u b m e r g e d s a n dU n c o v e r e d s a n dU n d e r s e a w e e d s a n d

T o t a l C o l i f o r m

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

A s C s E s G s Is K s M s O s Q s

L o c a t i o n

CFU/

100

ml

S u b m e r g e d s a n dU n c o v e r e d s a n dU n d e r s e a w e e d s a n d

F e c a l C o l i f o r m

0

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

5 0

A s C s E s G s Is K s M s O s Q s

L o c a t i o n

MPN

/100

ml

S u b m e r g e d s a n dU n c o v e r e d s a n dU n d e r s e a w e e d s a n d

E . c o l i

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

A s C s E s G s I s K s M s O s Q s

L o c a t i o n

CFU/

100

ml

S u b m e r g e d s a n dU n c o v e r e d s a n dU n d e r s e a w e e d s a n d

E n t e r o c o c c i , M F M e t h o d

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

A s C s E s G s I s K s M s O s Q s

L o c a t i o n

CFU/

100

ml

S u b m e r g e d s a n dU n c o v e r e d s a n dU n d e r s e a w e e d s a n d

C . p e r f r i n g e n s

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Enterococci at high tide low tide (contour Interval: 25CFU/100 ml)

E. coli at high tide low tide (contour Interval: 50MPN/100 ml)

108

306

50

25 50

50100

270

1 Km

1 mile

TL

Hobie Beach 116

25

1 Km

1 mile

TL

238

179

50 1008

135

50

226

1 Km

1 mile

TL

Hobie Beach

50

100

150

209

25

50

100

2550

213

251 Km

1 mile

TL

Hobie Beach

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Fecal coliform at high tide low tide (contour Interval: 50MPN/100 ml)

C. perfringens at high tide low tide (contour Interval:5CFU/100 ml)

50

50

50 100

458

1 Km

1 mile

TL

Hobie Beach

120

20

10

20

20

10

62

1 Km

1 mile

TL

Hobie Beach

10

10

20

10 2094

10

1 Km

1 mile

TL

Hobie Beach

5

15

10

36

50

1020

10

30

1 Km

1 mile

TL

Hobie Beach

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{Correlations}• Any significant correlation was not observed between microbes and physical-

chemical parameters

Rain Tide Temp pH Salinity Turbidity TC FC E.coli Ent(IDX) Ent(MF) CP

Rain 1

Tide 0.000 1

Temp 0.005 0.035 1

pH 0.035 0.000 0.088 1

Salinity 0.048 0.000 0.424 0.182 1

Turbidity 0.021 0.005 0.001 0.006 0.024 1

TC 0.035 0.021 0.000 0.006 0.051 0.151 1

FC 0.008 0.031 0.007 0.004 0.005 0.046 0.092 1

E.coli 0.000 0.003 0.012 0.000 0.000 0.034 0.324 0.110 1

Ent(IDX) 0.002 0.044 0.008 0.008 0.000 0.058 0.352 0.065 0.214 1

Ent(MF) 0.002 0.043 0.016 0.000 0.003 0.146 0.417 0.081 0.532 0.509 1

CP 0.004 0.025 0.032 0.002 0.001 0.238 0.432 0.152 0.413 0.339 0.662 1

Data from Daily Monitoring (Total 240 samples)

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[Conclusions]• Multiple microbial indicators provide conflict evaluations.

• Two beach water qualities can be significantly different even thought they are a few miles apart.

• Even thought the beach is considered to be more contaminated beach such as Hobie Beach it could be qualified as good water body since the numbers of microbes vary from small numbers to large numbers significantly on day to day and different indicator guidelines provide different water quality evaluations.

• Source of indicator microbes were beach sand.

– This was proved by some results of this study that all indicators were detected in beach sand and high concentrations were observed in shoreline at high tide. The locations of hotspots in beach sand and water body were the same.

• Seasonal changes did not affect the numbers of indicator microbes except total coliform. Total coliform concentrations were higher during wet season than during dry season.

• No significant correlations between physical-chemical parameters and microbes was observed.

– Correlations between rainfall and indicator density did not exist with the exception of extremely large storm.

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Recommendations for Further Study

• Measurement of additional microbes, such as coliphage and pathogenic bacteria, protozoan, and viruses.

• Evaluation of

– Reasons why the concentrations of indicator microbes vary significantly.

– Role of sand and seaweed in terms of promoting the survival and potential multiplication of the indicator microbes.

– Effects of sunlight, moisture, and salinity on the ability of the indicator microbes to survive.

– Settling rates of the various indicator microbes and their response to nutrients found in sewage.

• Development of a water circulation model of the Hobie Beach to determine the degree of flushing that is naturally provided to this side of the beach versus other portion of the beach. Installation of a weather station at Hobie Beach.

• Identification of the ultimate source of indicator microbes to the hotspots.

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Contact Information

Tomoyuki Shibata, M.S.

Environmental Engineering Lab

University of Miami1251 Memorial Dr. McArthur Bldg.#325

Coral Gables, FL 33146

tshibata@umsis.miami.edu

305-284-3172(lab)/2013(office)