1

ABSTRACT

The quality of water flowing

southward in the Everglades and

the Big Cypress Swamp was characterized by three synoptic surveys

along an 80-mile section of the

Tamiami Trail and along a 24-mile

transect down the Shark River

Slough, by monthly sampling of a

background reference site in the

central Big Cypress Swamp, and

by sampling of fish tissue for contaminants at several sites near the

Trail. The quality of water along

the Trail is spatially variable due to

natural and human influences.

Concentrations of dissolved solids

and common ions such as chloride

and sulfate were lowest in the

central and eastern Big Cypress

Swamp and were higher to the west

due to the effects of seawater,

especially during the dry season,

and to the east due to canal drainage from the northern Everglades.

Concentrations of total phosphorus

tended to decrease from west to

east along the 80-mile section of

the Trail, and were usually about

0.01 milligram per liter or less in

the Everglades. Short-term loads

(based on average discharge for 4

days) of total phosphorus and total

Kjeldahl nitrogen (ammonia plus

organic nitrogen) across four gaged

sections of the Tamiami Trail were

highest in the Everglades near the

S-12 structures primarily due to the

relatively greater discharges in that

section. Concentrations of dissolved solids and total phosphorus

at the central Big Cypress Swamp

site increased significantly during

the dry season as waters ponded.

Effects of nearby, upstream agricultural activities were evident at a

site in the western Big Cypress

Swamp where relatively high concentrations of total phosphorus,

total mercury, and dissolved

organic carbon and high periphyton

biomass accumulation rates were

measured and where several pesticides were detected. The most frequently detected pesticides along

the Trail were atrazine (14 detections), tebuthiuron (11 detections),

and metolachlor (5 detections), and

most concentrations were less than

0.1 microgram per liter. DDT

compounds were the only pesticides detected in fish from five

sites. Total DDT ranged from 5 to

6 micrograms per kilogram in

largemouth bass and from 11 to

17 micrograms per kilogram in

Florida gar.

INTRODUCTION

The National Water-Quality

Assessment (NAWQA) Program is

designed to assess the status and

trends in water quality over more

than half of the Nation. This significant task is subdivided into about

59 study units to focus more attention on local settings and issues.

The work within each study unit is

intended to continue for decades as

Water Quality in the Southern Everglades and Big Cypress Swamp

in the Vicinity of the Tamiami Trail, 1996–97

By Ronald L. Miller, Benjamin F. McPherson, and Kim H. Haag

Department of the Interior, U.S. Geological Survey

Below: Southerly view of Tamiami Trail near S-12-B
2

Figure 1. Selected land use and physical features in southern Florida.

EXPLANATION

Urban land

Agricultural land

Water Conservation Areas 1-3

Big Cypress National Preserve

Everglades National Park

Other

1

2

3

N

Lake

Okeechobee

ALABAMA GEORGIA

FLORIDA

Southern

Florida

NAWQA

Study Unit

a series of repeated cycles of a few

years of intensive sampling and

interpretative studies followed by a

few years of low-intensity sampling. Study units use fixed sites to

gather data on a regular basis, but

also use synoptic studies to gain

insight into topics of special interest, such as transport of water and

water-quality constituents,

improvement of spatial resolution

of water-quality data, and identification of sources of water-quality

constituents (Gilliom and others,

1995). The Southern Florida

(SOFL) NAWQA study began a

3-year period of intensive sampling

in 1996 (Haag and others, 1998).

This report summarizes a synoptic

study of water quality near the

southern end of the SOFL NAWQA

study unit (fig. 1). The movement

and quality of water in this area is

of great interest because of its

importance to State and National

parks and preserves and to the

ecosystem restoration underway in

the region.

Surface waters near the southern

end of the SOFL study unit are predominantly dispersed over broad

wetlands in Everglades National

Park (ENP), Big Cypress National

Preserve (BCNP), and several other

preserves and flow into coastal

waters from the Ten Thousand

Islands to Florida Bay (figs. 1 and 2).

The Tamiami Trail (U.S. 41) spans

these wetlands with numerous

bridges and culverts and, as the last

significant roadway that crosses the

mainland before the coast, provides

a location from which to sample,

measure, and characterize water

near the downstream end of the

study unit (fig. 2).

Most of the Tamiami Trail

between Naples and Miami is

within two physiographic provinces—the Big Cypress Swamp

and the Everglades (Davis, 1943).

The Big Cypress Swamp is

characterized by numerous

cypress strands, cypress domes,

and forested wetlands that grow

on limestone with little soil cover

(Duever and others, 1979). The

Everglades is characterized by a

wetland mosaic of tree islands,

dense sawgrass, and wet prairies

with peat soils and has periods and

depths of inundation generally

greater than those in the Big

Cypress Swamp (Davis and others,

1994). The two physiographic

provinces also differ in their land

use. Much of the central and

southern Big Cypress Swamp is

relatively undisturbed by channelization and development. North

of BCNP, the land is primarily

used for farming and ranching.

The Everglades has been more

highly modified north of the

Tamiami Trail, but is relatively

undisturbed to the south.

Below: Shark River Slough in the

Everglades (The River of

Grass) with tree islands

At left: Big Cypress Swamp near Loop Road
3

Trail during construction of

the road and served as a source

of limestone road base. Water

from canals, rivers, and sheetflow from wetlands collects in

the canal and flows southward

under the Tamiami Trail

through more than 100 culverts

and bridges. The Tamiami Trail

was widened in the 1950’s and

1960’s by adding limerock fill

from nearby excavations to the

old road bed; however, the

number and length of the

bridges was unaltered (Duever

and others, 1979; p. 705-748).

The western part of the Big

Cypress Swamp was drained

by the Barron River Canal

(completed in 1926, fig. 2) and

the Faka Union Canal System

(competed in the 1970's, fig. 2).

The central and southern Big

Cypress Swamp has remained

relatively undisturbed by drainage and development; however, much of the southern

Everglades, though protected

as wetlands in the ENP, has

been affected by water management activities to the north

(Klein and others, 1975).

Predevelopmental hydrology in south Florida is largely

inferred from vegetation and

soils and from historical documents. Actual measurements

Hydrologic Changes

Major modification of southern

Florida's natural drainage system

began in 1882 with the construction

of small drainage canals in the Kissimmee and Caloosahatchee basins

and gained momentum in 1905 when

the Florida Legislature passed the

first drainage law creating the Everglades Drainage District (Klein and

others, 1975). In subsequent years,

major modifications were made to

the hydrologic system through construction of large canals and levees

(earthen embankments), by establishment of water conservation areas

(WCAs), and through land-use

changes that continued throughout

the century. Development and

hydrologic modifications have been

most intense in the northern Everglades (which has been drained for

farming) and along the east coast

(which has been urbanized). The central and southern Everglades and the

Big Cypress Swamp have remained

mostly wilderness, but the effects of

drainage to the north were already

affecting water levels and flows in

some parts of the Everglades early in

the century. Construction of the

Tamiami Trail, which crosses the

southern Everglades and Big Cypress

Swamp and connects Miami with

Naples, began in the 1920's and was

completed in 1928 (Klein and others,

1975). The Tamiami Canal was dug

on the north side of the Tamiami

of water levels, water flows, and water

quality only began around midcentury, after substantial hydrologic modifications had been made. Parker and

others (1955) described hydrologic

conditions in the southern Everglades

during the 1940's and 50's. U.S. Geological Survey (USGS) records continued after that report and provide

information on water levels and flows

near the Tamiami Trail during the last

half of the 20th century. These records

include the southerly discharge of

water between State Road (SR) 29

and SR 997 (Krome Avenue) through

five east-west sections (fig. 2) of the

Trail for which discharge through

bridges, culverts, and water-control

structures are continuously gaged.

Figure 2. Sampling sites along and south of the Tamiami Trail (U.S. 41) between Naples and Miami.

0 25 50 MILES

0 50 KILOMETERS 25

Florida Bay ATLANTIC OCEAN

GULF OF MEXICO

Ten Thousand

Islands

Blackwater Creek

Kissimmee

River

River

Lake

Okeechobee

Tamiami Trail

and Canal

West Palm

Beach Canal

Canal

Hillsboro

North New

River

Miami Canal

Carnestown

Monroe

25

HW Rookery Br.

(23.1 mi)

23-S-1 (22.3 mi)

22-P-36 (17.5 mi)

SR-951

2-Tomato Road (6.8 mi)

6-Barron River Canal (24.1 mi)

9-Br 86 (32.9 mi)

3-Faka Union Canal (14.0 mi)

4-Br 64 (18.0 mi)

5-Br 70 (20.2 mi)

12-Br 105 (48.3 mi)

11-Br 98 (44.0 mi)

13-Br 114 (53.6 mi)

14

S-343B

(58.8 mi)

C-111

L-67A

L-67C

L-30

SR-29

SR-997 L-31N

S-8

S-7

Naples

Miami

7-Br 83 (30.4 mi)

15-S-12-A (60.7 mi)

16-S-12-B (63.9 mi)

17-S-12-C (66.6 mi)

18-S-12-D (69.5 mi)

Caloosahatchee

10-Roberts Lake Strand at Loop Road (40.9 mi)

1-Henderson Creek (0.8 mi)

8-3 Culverts (31.0 mi)

40-Mile Bend

P-34 21-P-33 (10.1 mi)

20-Bridge 870585

(81.1 mi) 19

Culvert 5.3 mi

(74.8 mi)

24

P-35

(23.6 mi)

15

S-12-A

(60.7 mi)

24

P-35

(23.6 mi)

EXPLANATION

EVERGLADES

BIG CYPRESS SWAMP

SHARK RIVER SLOUGH

BOUNDARY

SAMPLING SITE—Location, number,

name, and milage east of SR-951

CONTROL STRUCTURE—Location

and number

COMBINED SAMPLING SITE AND CONTROL

STRUCTURE—Location, number, name,

and milage east of SR-951

S-8
4

Annual water-level fluctuations

at a central location along the Trail

(Bridge 105 in the Big Cypress

Swamp, fig. 3a) illustrate changes

during the last 30 years in a region

that has been least modified by

drainage and land development.

Reduced fluctuations and higher

water levels occurred after about

1990 at this site. Similar changes

are also evident at other locations

in the southern Everglades.

Water-quality measurements

across the Tamiami Trail have been

unevenly distributed. Extensive

monitoring has been done in recent

years by the South Florida Water

Management District (SFWMD)

in the Everglades section of the

Trail, but relatively few data have

been collected in the Big Cypress

Swamp section. However,

between 1978 and 1993, the

40-Mile Bend to Monroe section

(fig. 2) of the Trail was sampled as

a USGS National Stream Quality

Assessment Network (NASQAN)

site. According to A. Clint Lietz

(U.S. Geological Survey, oral commun., 1998), water-quality samples

for the NASQAN program were

composites of water from one to

three bridges that had flow.

Changes in water quality have

been extensive in some regions of

south Florida; nutrients and pesticides are in higher concentrations in

agricultural and urban lands of the

northern Everglades than in remote

areas of the Big Cypress Swamp

and southern Everglades (McPherson and Halley, 1996). However,

even some remote parts of the

southern Everglades have undergone water-quality changes during

the last 30 years, as shown by the

significant increase in chloride

concentrations at P-33 (fig. 4;

shown as site 21 on fig. 2). No comparable change in the concentration

of chloride is evident in the central

Big Cypress Swamp at Bridge 105

(fig. 4; shown as site 12 on fig. 2)

during the same period. The

increase in chloride concentration

at P-33 is attributable to the construction of the L-67A Canal

(fig. 2) about 1962 and its extension

in 1967. The L-67A Canal and its

extension transport large amounts

of dissolved chloride from developed lands in the northern Everglades into the southern Everglades

(McPherson and others, 1976).

In recent years, a consensus has

developed among governmental

officials and environmentalists that

undeveloped parts of the Everglades should be protected and

restored. Restoration of the Everglades will require large-scale

changes in surface-water flow

patterns to recreate predevelopment hydrologic conditions. These

changes will include the diversion

of more water from the WCAs

southward under the Tamiami Trail

to restore historic drainage pathways, such as the Shark River

Slough, and to approximate predevelopment hydropatterns. Both an

understanding of historic and current water quality and a sustained

monitoring program are required to

ensure that water quality is suitable

for successful restoration.

Figure 3. Water-level fluctuations at Bridge 105 on the Tamiami Trail in

the Big Cypress Swamp, (a) 1968–97 and (b) 1996–97.

Figure 4. Long-term concentrations of chloride at P-33 in the

Everglades and at Bridge 105 in the Big Cypress Swamp.

J F M A M J J A S O N D J F M A M J J A S O N

1996 1997

6

9

7

8

WATER LEVEL, IN FEET ABOVE SEA LEVEL

68 70 72 74 76 78 80 82 84 86 88 90 92 94 96

2

10

4

6

8

Aug. 96 Synoptic

June 97 Synoptic

Aug. 97 Synoptic

b

a

D

195019601970198019902000

200

0

50

100

150

CHLORIDE, IN MILLIGRAMS PER LITER

P-33

Bridge 105
5

Table 1. Synoptic sampling sites with estimated distance along the Tamiami

Trail transect starting at State Road 951

[Map numbers shown on fig. 2; mileages are approximations from odometer readings

along the Tamiami Trail; SR, State Road; Br, bridge; L, lake]

Map

number

Estimated

distance

east of

SR 951,

in miles

USGS station

identification

number

Short name Physiographic

province

1 0.8 260326081412200 Henderson Creek Big Cypress Swamp

2 6.8 260020081363300 Tomato Road Big Cypress Swamp

3 14.0 255734081303400 Faka Union Big Cypress Swamp

4 18.0 255615081273600 Br 64 Big Cypress Swamp

5 20.2 255531081252000 Br 70 Big Cypress Swamp

6 24.1 255511081213000 Barron River Big Cypress Swamp

7 30.4 255327081161300 Turner River (Br 83) Big Cypress Swamp

8 31.0 255401081154100 Turner R. Rd. 3 Culverts Big Cypress Swamp

9 32.9 02290975 Br 86 Big Cypress Swamp

10 40.9 254714081055700 Roberts L. Strand at Loop Rd. Big Cypress Swamp

11 44.0 255133081033400 Gannet Strand (Br98) Big Cypress Swamp

12 48.3 02288798 Br 105 Big Cypress Swamp

13 53.6 254957080541600 Br 114 Big Cypress Swamp

14 58.8 254716080511900 Culvert below S-343B Big Cypress Swamp

15 60.7 254543080491100 S-12-A Everglades

16 63.9 02289018 S-12-B Everglades

17 66.6 02289041 S-12-C Everglades

18 69.5 254543080405400 S-12-D Everglades

19 74.8 254539080354800 Culvert 5.3 mile east of

S-12-D

Everglades

20 81.1 254540080295500 Br 870585 Everglades

Purpose and Scope

Water-quality data have been

collected extensively in some parts

of the Everglades; however, broadscale sampling across the southern

end of the Florida Peninsula is less

common (Haag and others, 1996).

The purpose of this report is to provide a broad synoptic or “snap-shot”

view of selected water-quality characteristics and short-term mass

transport of nutrients at selected

sites across the southern Everglades

and Big Cypress Swamp near the

southern end of the SOFL study

unit. The synoptic view identifies

high concentrations of and notable

patterns in selected water-quality

constituents that will be helpful in

understanding regional variations

in water quality and in selecting

future sampling locations for monitoring or refining mass transport

estimates.

This report presents waterquality data collected from 20 sites

along an 80-mile section of the

Tamiami Trail (table 1) between

SR 951 in the west and SR 997

(Krome Avenue) in the east and

from five sites along a 24-mile

transect through the Shark River

Slough (table 2) starting near

S-12-D on the Trail and running

southwesterly to the headwaters of

Rookery Branch (fig. 2). Approximately 20 of the 115 bridges, culverts, and flood-control gates along

the 80-mile section of the Trail

(table 3) were sampled during three

synoptic sampling periods (fig. 3b)

that represent both high summer

runoff (August 19–22, 1996, and

August 11–14, 1997) and low latespring runoff (June 2–5, 1997).

Historical water-quality information in the vicinity of the Trail is

also included to show time trends

or make comparisons.

METHODS

Sampling sites were categorized as either primary or secondary

sites. Primary sites were sampled

for more constituents than secondary sites and required more time for

sample processing in the field. At

most primary sites, water samples

were collected by the equal-widthincrement or multiple-vertical

method in which sample water is

collected continuously (depth integrated) from the water surface to

near the bottom at several places

(verticals) across a canal (Shelton,

1994). If aquatic plants were abundant, verticals were made in the

deepest areas that were clear of

plants. All bottles and equipment

that were used to collect and process samples were rinsed at least

three times with native water prior

to sample collection. At the primary

sites, sample water from all verticals was passed through a cone

splitter according to NAWQA

Table 2. Synoptic sampling sites with estimated distances down the Shark River

Slough transect starting at S-12-D

[Map numbers shown on fig. 2; mileages were computed from latitudes and longitudes]

Map

number

Distance

southwest of

S-12-D,

in miles

USGS station

identification

numbers

Short name

Physiographic

province

21 10.1 02290815 P-33 Everglades

22 17.5 02290828 P-36 Everglades

23 22.3 252818080504200 S-1 Everglades

24 23.6 02290830 P-35 Everglades

25 23.1 252756080512900 Headwaters Rookery Branch Everglades
6

parts-per-billion protocols (Shelton,

1994) to ensure that each sample

bottle received a representative mix

of water (Capel and others, 1995;

Capel and Larson, 1996). At secondary sites, water was collected at

a single point approximately 6

inches below the water surface. In

June and August 1997, extra water

was collected at secondary sites and

filtered for dissolved nutrient and

anion determinations. All water

samples for mercury were collected

at a single point. All water samples

were shipped to the laboratories on

ice, with the exception of mercury

which was preserved with hydrochloric acid and shipped at ambient

temperatures. After each use,

equipment that contacted sample

water was cleaned with laboratory

detergent, rinsed with deionized

water and then methanol, and

stored in closed containers to

prevent contamination of the next

sample.

Water samples from primary

sites were analyzed for nutrients,

major ions, pesticides, dissolved

organic carbon (DOC), and UV

absorbance at 254 nanometers

(nm). Most samples from secondary sites were analyzed for sulfate,

chloride, nutrients (only total

phosphorus, TP, and total Kjeldahl

nitrogen, TKN, were determined in

August 1996), DOC, and UV

absorbance at 254 nm. Nutrient

concentrations are all reported as

the elements nitrogen (N) and phosphorus (P). Water samples for total

mercury were collected in August

1996 and June 1997 at selected

sites. Field determinations of dissolved oxygen (DO), specific conductance, temperature, and pH were

made at most sites close to the time

of sample collection. For quality

assurance, eight organic or inorganic field blanks of high-quality

blank water (11 percent of environmental samples) and seven replicates (9 percent of environmental

samples) were collected during the

synoptic sampling trips, and additional field blanks were collected at

some other sampling sites near the

time of the synoptic sampling.

Biomass (ash-free dry mass,

AFDM) and chlorophyll–a (an

indicator of the algal component of

the periphyton) accumulation rates

were determined for periphyton

from glass slides deployed near the

Tamiami Trail in June and August

1997. Periphyton samplers were

floated just below the water surface

starting the week that water samples were collected for the synoptic

surveys. The slides were collected

2 to 3 weeks later and processed

for laboratory analysis. The rate of

periphyton growth can be computed

from accumulated mass, surface

area, and the length of time that

slides are exposed to water.

The USGS National WaterQuality Laboratory in Arvada,

Colorado, analyzed the samples

with a few exceptions. Sulfate and

chloride samples collected at secondary sites in August 1996 were

analyzed at the USGS Quality

Water Service Unit in Ocala,

Florida. The DOC and UV absorbance at 254 nm were determined

by Dr. George Aiken, USGS, Boulder, Colorado, and total mercury in

water was determined by Dr. David

Krabbenhoft, USGS, Middleton,

Wisconsin.

Total Dissolved Solids,

Specific Conductance,

and Major Ions

Chloride, sulfate, other major

ions, DOC, and silica contribute to

total dissolved solids (TDS).

Specific conductance is a measure

of the electrical conductivity of

dissolved ions in water and, when

Table 3. Historical mean annual discharges and numbers of water-conveyance features within sections of the Tamiami Trail

[ft3 s-1, cubic feet per second; SR, State Road]

1

Richard Semple, DOT, Tampa, Fla., written comm., 1998; 2Ernesto Mangual, USGS, Miami, Fla., written comm., 1998; 3Price and others, 1997.

Station

identification

number

Discharge sections Flow under Tamiami Trail is through

Annual mean

discharge,

(ft3

 s-1)

1

Averaging period,

water years

Not applicable Carnestown to SR 951 41 bridges and culverts1 Ungaged, most are

tidally influenced

Not

applicable

02288800 Monroe to Carnestown 19 bridges and 1 culvert2 3933 1960–1996

02288900 40-Mile Bend to Monroe 29 bridges3 3613 1964–1996

02289040 Levee 67A to 40-Mile Bend 4 flood control structures (S-12A, B,

C, and D)3

8053 1964–1996

02289060 Levee 30 to Levee 67A 19 culverts and S-12–E2 1573 1964–1996

02290767 Bridge 870585 Flow under Trail is at Bridge 870585. Discharge is measured at Levee 31 North Extension at 1 mile.

2433

(median)

1992–1996

Sum for all six reaches 115 water-conveyance features under the

Tamiami Trail between SR 951 and Krome

Avenue (SR 997)

Water-Quality Characteristics

Along the Tamiami Trail and

the Shark River Slough
7

multiplied by 0.65, provides a rough

and inexpensive estimate of the

TDS. Sources of TDS that contribute to specific conductance include

agricultural and urban drainage, seawater, dissolution of rocks and soils,

and wastes from wildlife.

Specific conductance varied

widely along the 80-mile section of

the Tamiami Trail, depending on

location, season, upstream land

use, and proximity to the coast

(fig. 5a-c). Specific conductance

values were generally higher along

the western Big Cypress Swamp

(approximately miles 0–30) and the

Everglades (approximately miles

66–81) sections of the Trail than in

the central section (miles 30–66).

Higher values in the west, where

the Trail is within a few miles of

the coast, are attributed to effects

of seawater, particularly during dry

periods when marine waters extend

farthest inland. Higher specific

conductance values in the Everglades (miles 66–81) are attributed

to canal transport of mineralized

water from the northern Everglades. The sources of the mineralized water include Lake Okeechobee; the Everglades Agricultural Area south of Lake Okeechobee; and naturally occurring,

shallow, mineralized water

beneath the northern Everglades

(Parker and others, 1955, p. 764).

Water from the northern Everglades flows under the Trail

through culverts and the S-12

water-control structures into ENP

and then south and southwest down

the Shark River Slough toward the

coast. Specific conductance values

in the Shark River Slough tended

to decline slightly downstream of

the S-12 structures (fig. 5d-f).

Specific conductance values

vary seasonally at locations that are

relatively unaffected by canal

drainage or coastal waters. This

seasonal variation is illustrated for

a 22-month period at Bridge 105 in

the central Big Cypress Swamp by

comparing specific conductance

and selected ion concentrations

with discharge (figs. 6a-f). Specific

conductance increased from a minimum of 207 microsiemens per

centimeter at 25 degrees Celsius

(μS cm-1) on October 8, 1996, near

the end of the rainy season when

the daily mean discharge was 1,230

cubic feet per second (ft3 s

-1) to a

maximum of 535 μS cm-1 on

March 25, 1997, near the end of the

dry season when discharge was

only 30 ft3 s

-1. Approximately 91

percent of the increase in specific

conductance between these two

sampling times was due to

increases in concentrations of

calcium and bicarbonate (shown as

alkalinity) ions. Magnesium

(not shown), sodium, and chloride

Figure 5. Specific conductance along the Tamiami Trail and down the Shark River Slough, August 1996 and June and August 1997.

0 90 10 20 30 40 50 60 70 80

0

2,000

500

1,000

1,500

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

0 90 10 20 30 40 50 60 70 80

DISTANCE, MILES EAST OF STATE ROAD 951

0

2,000

500

1,000

1,500

0 90 10 20 30 40 50 60 70 80

0

2,000

500

1,000

1,500

0 25 5 10 15 20

0

2,000

500

1,000

1,500

0 25 5 10 15 20

DISTANCE, MILES SOUTHWEST OF S-12-D

0

2,000

500

1,000

1,500

0 25 5 10 15 20

0

2,000

500

1,000

1,500

Shark River Slough

August 1996

Shark River Slough

June 1997

Shark River Slough

August 1997

Tamiami Trail

August 1996

Tamiami Trail

June 1997

Tamiami Trail

August 1997

3 sites more than 11,000

S-12-DP-33P-36S-1Rookery Branch P-35

a b c

def

AT 25 DEGREES CELSIUS
8

ions were responsible for approximately 9 percent of the

increase in specific conductance, whereas potassium, sulfate, and fluoride ions had only a minor effect on specific

conductance. The percentage increases in calcium (174

percent), and bicarbonate (189 percent) ion concentrations were greater than for the sodium (71 percent),

potassium (33 percent), and chloride (95 percent) ions.

Processes that could contribute to increased TDS and

specific conductance in surface waters during the dry

season are evapotranspiration, increased density of animal populations in and around dwindling surface waters,

and relatively greater ground-water contributions to the

remaining surface waters (as surface water flows and

rainfall decline). If evaporation of ponded surface water

were the only process occurring during the dry season,

the concentration of ions such as sodium, chloride, calcium, and bicarbonate would all increase by similar percentages. The relatively greater increase in calcium and

bicarbonate ion concentrations at Bridge 105 cannot be

explained by evaporation alone. Increased ground-water

inflow from the limestone surficial aquifer, relative to

surface-water inflow and rainfall, is likely the cause of

much of the relatively greater increase in the calcium and

bicarbonate ions, compared with the increases in the

sodium, chloride, and magnesium ions.

The plot of chloride concentration along the Tamiami

Trail is U-shaped (fig. 7a) with the highest concentrations

occurring near the west and east ends of the study area.

Concentrations in the central section of the Tamiami

Trail (approximately miles 30–66) were typically about

10 to 30 milligrams per liter (mg L-1) and increased to

40 mg L-1 or more in the western Big Cypress Swamp

and the Everglades from about S-12-C and eastward

(miles 66–81). The highest concentrations were in western Big Cypress Swamp in June 1997, when seawater

moved inland from the nearby coast during the low runoff period. The higher concentrations of chloride in the

Everglades east of S-12-C, compared with concentrations

in the central section, are due to the canal transport of

mineralized water from the northern Everglades (Parker

and others, 1955).

Like chloride, the plot of sulfate concentration across

the Tamiami Trail is U-shaped (fig. 7b). The higher concentrations in the western Big Cypress Swamp are due to

the effects of seawater, and the higher concentrations in

the Everglades are due to the effects of mineralized water

from the north. In the central section of the Tamiami

Trail (approximately miles 30–66), most sulfate concentrations were quite low (30 out of 31 concentrations were

from less than 0.1 to 2.0 mg L-1) during the three synoptic sampling periods and during monthly sampling at

Bridge 105 between May 1996 and January 1998 (25 out

of 27 concentrations were less than 0.8 mg L-1). These

low background concentrations make sulfate ion a sensitive indicator of human impacts on water quality in the

central Big Cypress Swamp.

Figure 6. Concentrations of calcium, alkalinity, sodium, and

chloride; discharge; and specific conductance at Bridge 105 in

the Big Cypress Swamp from May 1996 to February 1998.

0

20

10

DISSOLVED SODIUM,

0

100

20

40

60

80

DISSOLVED CALCIUM,

0

40

20

DISSOLVED CHLORIDE,

0

400

200

TOTAL ALKALINITY,

MJ J ASOND J FMAMJ J ASOND J F 0

600

200

400

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS

a

b

c

d

e

f

0

2,500

500

1,000

1,500

2,000

DAILY MEAN DISCHARGE,

IN MILLGRAMS PER LITER

AS CaCO

IN MILLIGRAMS

PER LITER

IN MILLIGRAMS

PER LITER

IN MILLIGRAMS

PER LITER

IN CUBIC FEET

PER SECOND

Periodic

Continuous

3

1996 1997 1998
9

Nutrient Concentrations and

Periphyton Growth

Phosphorus and nitrogen are the

most common nutrients that limit

the growth of aquatic plants.

Phosphorus is usually growthlimiting in freshwater and even

small increases in concentrations

and loadings can have significant

ecological impacts. Phosphorus

generally occurs at quite low concentrations (less than 0.01 mg L-1)

in unimpacted wetlands of southern

Florida and at higher concentrations (median concentrations of

0.060 mg L-1 at S-7 and 0.067

mg L-1 at S-8 for 1984–93, data

from SFWMD) in parts of the

northern Everglades. The high

concentrations in the northern parts

of the Everglades have been implicated in changes in wetland communities, such as the shift from

sawgrass to cattails and the change

from calcareous periphyton mats of

cyanobacteria and diatoms to periphyton dominated by filamentous

green algae (McCormick and

O’Dell, 1996).

Figure 7. Concentrations of chloride, sulfate, and total phosphorus along the Tamiami Trail in August 1996 and June and August 1997.

0 90 10 20 30 40 50 60 70 80

0

0.10

0.02

0.04

0.06

0.08

TOTAL PHOSPHORUS,

MILLIGRAMS PER LITER

0 90 10 20 30 40 50 60 70 80

DISTANCE, MILES EAST OF STATE ROAD 951

0

0.10

0.02

0.04

0.06

0.08

0 90 10 20 30 40 50 60 70 80

0

0.10

0.02

0.04

0.06

0.08

0 90 10 20 30 40 50 60 70 80

0

150

50

100

SULFATE, MILLIGRAMS

PER LITER

0 90 10 20 30 40 50 60 70 80

0

150

50

100

0 90 10 20 30 40 50 60 70 80

0

150

50

100

0 90 10 20 30 40 50 60 70 80

0

200

50

100

150

CHLORIDE, MILLIGRAMS

PER LITER

0 90 10 20 30 40 50 60 70 80

0

200

50

100

150

0 90 10 20 30 40 50 60 70 80

0

200

50

100

150

August 1996

August 1996

August 1996

June 1997

June 1997

June 1997

August 1997

August 1997

August 1997

3 sites more

than 3,400

a

b

c

300

3 sites more

than 500

Tomato Road Tomato Road 0.36

more than 0.18

Tomato Road 0.30
10

Unlike chloride and sulfate, the

plot of TP concentration along the

Tamiami Trail was not U-shaped,

but generally decreased from west

to east (fig. 7c). The highest concentrations (0.30, greater than 0.18,

and 0.36 mg L-1) during our three

sampling events were at the

Tomato Road site (mile 6.8) and

were probably caused by agricultural activities just north and upgradient of the site. Water from these

agricultural lands may also contribute to the high phosphorus concentrations in Blackwater Creek

(0.016 to 0.095 mg L-1; Joseph

Boyer, written commun., Florida

International University, 1998) a

few miles downstream of Tomato

Road and in the Ten Thousand

Islands (Florida International

University, 1998). East of Tomato

Road, concentrations of TP tended

to decrease across the Big Cypress

Swamp from about 0.05 to 0.01

mg L-1 (fig. 7c). During the synoptic sampling, concentrations of TP

along the Everglades section of the

Tamiami Trail (miles 60–81) and at

sites in Shark River Slough were

generally less than 0.01 mg L-1,

except for higher concentrations at

S-12-D (mile 69.5 in August 1997;

0.030 mg L-1) and at the headwaters of Rookery Branch (0.027

mg L-1; fig. 2, site 25) in the Shark

River Slough. Concentrations of

TP less than 0.01 mg L-1 are consistent with long-term (1984–93) patterns in phosphorus concentrations

for these areas (fig. 8, data from

SFWMD).

At Bridge 105 in the central Big

Cypress Swamp, concentrations of

TP ranged from 0.005 to 0.086

mg L-1 over a 22-month period

from May 1996 to February 1998

(fig. 9a). Highest concentrations

were associated with low discharge

and low water levels. TP concentrations had a pattern quite similar

to that of specific conductance

(fig. 6f); whereas, concentrations

of total nitrogen (TN; fig. 9b) had

no apparent relation with seasonal

changes in discharge. TP increased

760 percent from a minimum of

0.01 mg L-1 on October 8, 1996,

near the end of the rainy season

when the daily mean discharge was

1,230 ft3 s

-1, to a maximum of

0.086 mg L-1 on March 25, 1997,

near the end of the dry season

when discharge was only 30 ft3 s

-1.

As a basis of comparison, dissolved nitrogen, total Kjeldahl

nitrogen (TKN is total organic

nitrogen plus ammonia), ammonia,

and orthophosphate increased by

225, 29, 17, and more than 700

percent, respectively, whereas

dissolved Kjeldahl nitrogen and

nitrate decreased by 33 and 21

percent, respectively, between the

same sampling dates.

Biomass and growth rate of

periphyton (biological communities living on submerged surfaces

such as rocks and aquatic plants)

can serve as indicators of the

availability of nutrients and of the

potential of water to support plant

growth. A number of studies in the

Everglades have addressed the

.

Figure 8. Median and percentiles of concentrations of

total phosphorus at Bridge 105, the S-12 Structures,

and Shark River Slough sites, 1984–93. (S12s means

S-12-A, S-12-B, S-12-C, and S-12-D combined.)

.

Figure 9. Monthly concentrations of total phosphorus and total nitrogen at

Bridge 105 in the Big Cypress Swamp, 1996–98.

.

BR105

S12s

P34P33P36P35

0

0.10

0.02

0.04

0.06

0.08

TOTAL PHOSPHORUS, IN

MILLIGRAMS PER LITER

EXPLANATION

10th percentile

25th percentile

Median

75th percentile

90th percentile

TOTAL PHOSPHORUS

.

MJ J ASOND J FMAMJ J ASOND J F

1996 1997 1998

.

0

2

1

TOTAL NITROGEN, IN

MILLIGRAMS PER LITER

Bridge 105

a

b

MJ J ASON D J FMAMJ J ASON DJF

1996 1997 1998

.

0

0.10

0.05

TOTAL PHOSPHORUS, IN

MILLIGRAMS PER LITER

Bridge 105
11

influence of water-column phosphorus on the biomass and growth

rate of periphyton communities.

Generally, periphyton biomass and

growth rates in the Everglades are

significantly changed by nutrient

enrichment (Swift, 1981; Swift and

Nicholas, 1987; Hall and Rice,

1990; Browder and others, 1994;

McCormick and O’Dell, 1996).

Other studies have focused on the

influence of phosphorus enrichment on periphyton community

composition (Scheidt and others,

1987; McCormick and O’Dell,

1996; McCormick and others,

1999). Changes in community

composition of periphyton have

important implications for the

Everglades food web.

We evaluated periphyton

growth (as accumulation of AFDM

and of chlorophyll-a) along the

Tamiami Trail using artificial substrates that allow sample collection

in a standardized way and facilitate

comparisons between water bodies.

Periphyton biomass accumulated at

sites along the Trail at rates of 0.09

to 0.9 grams per square meter per

day (g m-2 d-1) as AFDM and 0.05

to 1.0 milligrams per square meter

per day (mg m-2 d-1) as chlorophyll-a

with no obvious spatial patterns,

although the highest rate for

AFDM was at the Tomato Road

site (fig. 10a) just downgradient of

agricultural land. The absence of

obvious spatial patterns of chlorophyll-a and AFDM accumulation

rates may be due to the limited

number of samples collected and

the inherent variability of the methods. Chlorophyll-a accumulation

rates measured during this study in

June and August 1997 were comparable with rates reported by

Swift and Nichols (1987; 0.04 to

0.07 mg m-2 d-1 as chlorophyll-a for

June through August was computed from data in fig. 3) at a lownutrient (average TP of 0.011

mg L-1) marsh site in the northern

Everglades.

Phosphorus and Nitrogen

Loads

Nutrient loads are measures of

“new” nutrient matter moving into

an ecosystem from a source such as

a stream or the atmosphere.

Increased annual nutrient loading

can change an ecosystem from

oligotrophic to eutrophic. Nutrient

loads in surface water are computed by multiplying the concentration of a nutrient by the

discharge of water (the volume of

water flowing past a cross section

of the stream or other water course

per unit of time). Usually, the product of the concentration and discharge of water must be multiplied

by a conversion factor to make the

concentration and flow units compatible and to produce a number

that is neither too large nor too

small to use conveniently. Longterm (annual or multi-annual)

nutrient loads average seasonal

variations and are more representative of the inputs to an ecosystem

than are daily loads. Daily loads,

such as those given below, can

provide insight into seasonal variations and the relative magnitude of

various nutrient sources.

We computed daily loads of TP

and TKN for each of the three synoptic sampling periods. Loads were

determined for each of the five

gaged sections (see table 3) of the

Trail from the mean daily discharge

for the 4-day sampling period and

the average concentration of

selected nutrients within each section. Loads for TKN are reasonable

estimates of loads of TN along the

Trail because TN is composed

predominantly of TKN. TKN

Figure 10. Biomass (as ash-free dry mass, AFDM) and chlorophyll-a

accumulation rates across the Tamiami Trail, June and August 1997.

0 90 10 20 30 40 50 60 70 80

DISTANCE, IN MILES EAST OF STATE ROAD 951

0

1.5

0.5

1.0

CHLOROPHYLL-A, IN MILLIGRAMS

PER SQUARE METER PER DAY

0 90 10 20 30 40 50 60 70 80 .

0

1.0

0.2

0.4

0.6

0.8

BIOMASS ACCUMULATION RATE, IN GRAMS

OF DRY MASS PER SQUARE METER PER DAY

June 1997

August 1997

a

b

Tomato Road

Tomato

Road

June 1997

August 1997
12

concentrations for 59 samples

averaged 98 percent and ranged

from 82 to 100 percent of the TN

concentrations during this study.

Across the gaged sections of the

Trail, daily loads of TP and TKN

were usually highest in the Everglades section through the S-12

structures (fig. 11a and b, miles

60.7–69.5). This was due more to

the large flows from the northern

Everglades than to high concentrations at the S-12 structures. The

maximum daily loads for TP (57

kilograms (kg)) and TKN (6,300 kg)

occurred at the S-12 structures during the rainy season in August

1997. A relatively high daily TP

load (35 kg) also occurred in the

Monroe to Carnestown section

during August 1997.

Dissolved Organic Carbon

and Ultraviolet Absorbance

DOC can originate from natural

sources such as living plants and

decaying plant matter or from

human sources. DOC is of ecological significance because it can

(1) contribute to water color which

absorbs light in the photosynthetically active wavelength region and

thus reduce the amount of light

available for the growth of submerged aquatic plants, (2) serve as

a source of carbon for bacterial

growth, and (3) form complexes

with trace elements (such as mercury) and make them more soluble

and mobile in water. DOC concentrations near the Tamiami Trail

ranged from 4.8 to 26.9 mg L-1 and

had a U-shaped plot (fig. 12a)

similar to chloride and sulfate ions.

Lowest concentrations of DOC

occurred in the central section of

the Tamiami Trail (approximately

miles 30–60), and highest concentrations were at bridges 64 and 70

(miles 18.0 and 20.2) in the west

and between S-12-B and culverts

5.3 miles east of S-12-D (miles

63.9–74.8) in the east.

Aromatic (containing conjugated double bonds like those in

benzene) DOC compounds that

contain carboxylic acid, hydroxyl,

and amino functional groups (parts

of a molecule) form complexes

with trace elements (Stumm and

Morgan, 1981, p. 375). One of the

simplest and most inexpensive

means of comparing the relative

abundance of aromatic carbon in

DOC is to measure the ultraviolet

absorbance at 254 nanometers

(UV254) and compute the ratio

UV254/DOC (specific ultraviolet

absorbance) as an indicator of the

relative abundance. A higher ratio

indicates a greater potential for

complexing and transporting trace

elements.

The UV254/DOC ratio ranged

from 0.017 to 0.060 along the

Tamiami Trail during the three synoptic sampling periods, and tended

to decrease from west to east

(fig. 12b). The highest ratios

(indicative of a relatively high fraction of aromatic carbons in DOC)

occurred at bridges 64 and 70

(miles 18.0-20.2) during low flow

in June 1997. These bridges are

within 5 miles of the Gulf of Mexico and were affected by marine

water during this low-flow period,

as evident from specific conductance values greater than 11,000

μS cm-1 and by the presence of

marine organisms such as blue

crabs (Callinectes sapidus). Thus,

coastal marshes or mangrove forests may be the source of the high

ratios.

Figure 11. Short-term loads of total phosphorus and total Kjeldahl nitrogen (ammonia

plus organic nitrogen) along sections of the Tamiami Trail, August 1996 and June and

August 1997 with long-term loads for two of the sections (from Haag and others, 1996).

0 90 10 20 30 40 50 60 70 80

DISTANCE, MILES EAST OF STATE ROAD 951

0

60

20

40

TOTAL PHOSPHORUS LOAD, IN

KILOGRAMS OF PHOSPHORUS PER DAY

August 1996

June 1997

August 1997

0 90 10 20 30 40 50 60 70 80

0

8,000

2,000

4,000

6,000

TOTAL KJELDAHL NITROGEN LOAD, IN

KILOGRAMS OF NITROGEN PER DAY

a

b

August 1996

June 1997

August 1997

Long-term 800

Long-term 2,000

Long-term 30

Long-term

10
13

Mercury

The Florida Department of

Health and Rehabilitative Services

(1993) issued a health advisory recommending that, because of high

mercury concentrations, fish consumption be restricted in some parts

of Florida and completely avoided

in other areas, such as the Everglades. The high concentrations of

mercury in the biota are related to

processes in the water and sediment

that favor methylation of mercury

and concentration of mercury in the

Everglades food chain. USGS

researchers and others are currently

studying the sources and cycling of

mercury and the relation of these

processes to the high concentrations

reported in fish and other wildlife.

We collected water samples for

total mercury analysis at eight and

seven sites along the Tamiami Trail

in August 1996 and June 1997,

respectively. The highest value for

total mercury (8.3 ng L-1) occurred

at Tomato Road (mile 6.8) in June

1997. All other values were

between 1.4 and 3.7 ng L-1 (fig. 13).

Our data are consistent with those of

others sampling for mercury in

waters of the northern Everglades

(David Krabbenhoft, U.S. Geological Survey, oral commun., 1996).

There was no obvious relation

between mercury concentrations

and DOC and UV254 along the Trail

based on plots of 13 data pairs

(not shown).

Concentrations of mercury in

fish provide a better time-integrated

sample than concentrations in water.

Largemouth bass and Florida gar

collected by a NAWQA team at four

sites near the Tamiami Trail in

August–December 1995 (Haag and

McPherson, 1997) were analyzed

for mercury in fish livers (composites of 5 to 10 livers). Largemouth

bass had mercury concentrations of

25 micrograms per gram (μg g-1)

at P-33 and 26 μg g-1 at L-67A

Canal. Florida gar had concentrations of 110 μg g-1 at Bridge 105 and

160 μg g-1 at Loop Road.

Figure 12. Dissolved organic carbon and specific ultraviolet absorbance (ratio of ultraviolet

absorbance at 254 nonometers to the concentration of dissolved organic carbon) along the

Tamiami Trail, August 1996 and June and August 1997. (Analyses were done by Dr.

George Aiken, USGS, Boulder, Colorado.)

Figure 13. Concentrations of total mercury in water along the Tamiami Trail,

August 1996 and June 1997. (Analyses were done by Dr. David Krabbenhoft,

USGS, Middleton, Wisconsin.)

0 90 10 20 30 40 50 60 70 80 .

0

30

10

20

DISSOLVED ORGANIC CARBON,

IN MILLIGRAMS PER LITER

a

b

0 90 10 20 30 40 50 60 70 80

DISTANCE, MILES EAST OF STATE ROAD 951

0

0.08

0.02

0.04

0.06

SPECIFIC ULTRAVIOLET ABSORBANCE, IN

ABSORBANCE UNITS AT 254 NANOMETERS

PER MILLIGRAM PER LITER OF DISSOLVED

ORGANIC CARBON

August 1996

June 1997

August 1997

August 1996

June 1997

August 1997

0 90 10 20 30 40 50 60 70 80

DISTANCE, MILES EAST OF STATE ROAD 951

0

10

2

4

6

8

TOTAL MERCURY IN WATER,

IN NANOGRAMS PER LITER

August 1996

June 1997

Tomato Road
14

Pesticides

Pesticides are applied in agricultural and urban areas and are

also sprayed directly into canals to

kill nuisance aquatic weeds or onto

weeds and shrubs along the roadsides and canal banks. Because

pesticides can be transported long

distances in air (Majewski and

Capel, 1995), they are sometimes

detected in areas remote from the

point of application.

Water samples were collected at

selected sites during the three synoptic sampling periods and analyzed for more than 100 different

pesticides. Pesticide concentrations

above the minimum reporting level

(detections) are listed in table 4

along with criteria recommended

for protection of aquatic life

(National Academy of Sciences

and National Academy of Engineering, 1972; NAWQA NST,

1998). All of the compounds

detected were herbicides or a herbicide degradation product (deethylatrazine) except for single detections

of the insecticides or nematicides

malathion, diazinon, and azinphosmethyl. Atrazine was the most

frequently detected pesticide (14

detections), followed by tebuthiuron (11 detections) and metolachlor

(5 detections). One or more pesticides were detected at all sites

except Bridge 114, and the greatest

number of detections were at

S-12-D and Tomato Road. In all

but five samples, concentrations

of pesticides were less than

0.1 μg L-1. A few concentrations

exceeded the aquatic life criteria:

metolachlor at Tomato Road and

S-12-D, malathion at P-33, and

azinphos-methyl at Bridge 105

(table 4).

Table 4. Concentrations of pesticides detected in water along the Tamiami Trail and Shark River Slough transects,

August 1996 and June and August 1997

[E behind the value means the number is an estimate. Estimated values below the usual reporting level are given for samples in which the

compound’s presence was verified from spectra. Values above the reporting levels are estimated if there are interferences, values

below the lowest standard, or extraction recoveries less than normal. For other pesticides detected only once during the synoptics, the

superscripts represent: d, diazinon; m, malathion; n, napropamide; p, propanil; t, triclopyr; z, azinphos-methyl . #Canadian criteria/NAS-NAE

recommendations for protection of aquatic life (see text for references).

Synoptic site

and date

Deethylatrazine,

μg L-1

Atrazine,

μg L-1

Tebuthiuron

μg L-1

Simazine,

μg L-1

Metolachlor,

μg L-1

Metribuzin

sencor,

μg L-1

2,4-D,

μg L-1

Other pesticides

detected once,

μg L-1

Aquatic-Life Criteria # none/none 2/none 1.6/none 10/10 8/0.005 1/none 4/3

Tomato Road at gage

Aug. 1996

June 1997

Aug. 1997

0.008 0.14

0.02

0.01

0.010

0.011

0.023

0.017

0.007 0.50E

0.004Ed, 0.0063n

1.2Et

Faka Union Canal

June 1997 0.002E

Bridge 70

June 1997 0.34

Barron River

Aug. 1996

June 1997

0.004

0.003E 0.003E 0.15

0.0056p

Bridge 105

Aug. 1996

June 1997

Aug. 1997

0.005

0.003E

0.042Ez

 S-343B at Trail

Aug. 1996

June 1997

0.001E 0.004

0.004

0.01E

S-12D

Aug. 1996

June 1997

Aug. 1997

0.004E

0.013E

0.006E

0.036

0.40

0.065

0.03

0.03

0.04E

0.022 0.037

0.032

ENP P-33

Aug. 1996

June 1997

Aug. 1997

0.006

0.005E

0.038

0.019

0.02

0.01

0.03E

0.015m

ENP Rookery Branch

June 1997

0.002E 0.01

Reporting level <0.002 <0.001 <0.01 <0.005 <0.002 <0.004 <0.035
15

Conclusions

The quality of surface water

flowing southward in the Everglades and Big Cypress Swamp in

the vicinity of an 80-mile section

of the Tamiami Trail is spatially

variable due to natural and human

influences. Concentrations of chloride, sulfate, specific conductance,

and DOC tended to be relatively

low in the undeveloped center of

the Tamiami Trail from the Turner

River (mile 30.4) to about S-12-C

(mile 66.6) and relatively high at

the more developed west and east

ends, especially during the dry season. These water-quality characteristics suggest that three distinct

subsections should be considered

as the minimum number required

to describe and monitor water quality along the 80-mile study section.

Relatively high concentrations of

these constituents occurred to the

west of the Turner River due to

agricultural and marine inputs and

to the east of S-12-C due to the

inflow of mineralized water from

the northern Everglades through a

network of canals. Twelve pesticides or pesticide degradation

products were detected across the

Tamiami Trail, with highest concentrations usually at Tomato Road

in the west or S-12-D in the east

where agricultural influences were

greatest. Total phosphorus tended

to decrease from west to east along

the Tamiami Trail.

Seasonal variations in water

quality are superimposed on spatial

variations in the study area.

Concentrations of many dissolved

constituents and total phosphorus

increased during the dry season due

to processes such as the inland

movement of seawater near the

western coast, evapotranspiration,

ground-water inflow, or the higher

density of wildlife in and around

the Tamiami Canal.

Fish and bottom sediment

provide time-integrated samples of

pesticide occurrence. Fish and bedsediment samples were collected

during an earlier phase of our study

at a number of sites in southern

Florida (Haag and others, 1998).

In the vicinity of the Tamiami Trail,

the fish included largemouth bass

and Florida gar collected at the Barron River, Loop Road, Bridge 105,

S-12 structures (S-12-A through

S-12-D), and in the L-67A Canal in

August-December 1995. Composite fish samples (5-10 fish of a species at each site) were analyzed for

25 organochlorine pesticides (Haag

and McPherson, 1997). DDT compounds were the only pesticides

detected in fish at these five sites

near the Trail. Total DDT ranged

from 5 to 6 μg kg-1 in largemouth

bass and from 11 to 17 μg kg-1 in

Florida gar. These DDT concentrations were lower than the concentrations found in largemouth bass and

gar samples from six sites in the

northern Everglades, where total

DDT ranged from about 220 to

1,200 μg kg-1 (Haag and McPherson, 1997). A single bottom sediment sample collected at Bridge 105

in August 1996 contained 41 μg kg-1

of total DDT; concentrations at five

other southern Florida sites ranged

from 0.7 to 310 μg kg-1 of total

DDT.

References

Browder, J.A., Gleason, P.J., and

Swift, D.R., 1994, Periphyton in

the Everglades: Spatial variation,

environmental correlates, and ecological implications, in Davis,

S.M., and Ogden, J.C., eds., Everglades—The ecosystem and its

restoration: Delray Beach, Fla.,

St. Lucie Press, p. 379–418.

Capel, P.D., and Larson, S.J., 1996,

Evaluation of selected information

on splitting devices for water samples: U.S. Geological Survey

Water-Resources Investigations

Report 95–4141, 103 p.

Capel, P.D., Nacionales, F.C., Larson,

S.J., 1995, Precision of a splitting

device for water samples: U.S.

Geological Survey Open-File

Report 95–293, 6 p.

Davis, J.H., Jr., 1943, The natural features of southern Florida, especially the vegetation and the

Everglades: Florida Geological

Survey Bulletin 25, 311 p.

Davis, S.M., Gunderson, L.H., Park,

W.A., Richardson, J.R., and Mattson, J.E., 1994, Landscape dimensions, composition, and function

in a changing Everglades ecosystem, in Davis, S.M., and Ogden,

J.C., eds., Everglades—The ecosystem and its restoration: Delray

Beach, Fla., St. Lucie Press,

p. 419–444.

Duever, M.J., Carlson, J.E., Meeder,

J.F., Duever, L.C., Gunderson,

L.H., Riopelle, L.A., Alexander,

T.R., Myers, R.F., and Spangler,

D.P., 1979, Resource inventory

and analysis of the Big Cypress

National Preserve: Final report to

the U.S. National Park Service,

University of Florida, and

National Audubon Society,

vol. 1—Natural Resources, 700 p.

Fishman, M.J., Raese, J.W., Gerlitz,

C.N., and Husband, R.A., 1994,

U.S. Geological Survey approved

inorganic and organic methods for

the analysis of water and fluvial

sediment, 1954–94: U.S. Geological Survey Open-File Report

94–351, 55 p.

Florida Department of Health and

Rehabilitative Services, 1993,

Health advisory mercury in Florida freshwater fish: brochure, 2 p.

Florida International University, 1998,

Southeast Environmental

Research Program: accessed

July 16, 1998, at URL

http://www.fiu. edu/~serp/jrpp/

wqmn/datamaps/tp_1097.gif.

Gilliom, R.J., Alley, W.M., and Gurtz,

M.E., 1995, Design of the

National Water-Quality Assessment Program: Occurrence and

distribution of water-quality conditions: U.S. Geological Survey

Circular 1112, 33 p.
16

Haag, K.H., Bernard, B.A., Bradner,

L.A., McCulloch, D.S., McPherson, B.F., and Miller, R.L., 1998,

National Water-Quality Assessment Program: Study design for

data collection in the southern

Florida study unit, 1996–98: U.S.

Geological Survey Fact Sheet

FS–061–98, 4 p.

Haag, K.H., and McPherson, B.F.,

1997, Organochlorine pesticides

and PCBs in southern Florida

fishes: Then and now: U.S.

Geological Survey Fact Sheet

FS–110–97, 4 p.

Haag, K.H., Miller, R.L., Bradner,

L.A., and McCulloch, D.S., 1996,

Water-quality assessment of

southern Florida: An overview of

available information on surfaceand ground-water quality and

ecology: U.S. Geological Survey

Water-Resources Investigations

96–4177, 42 p.

Hall, G.B. and Rice, R.G., 1990,

Response of the Everglades marsh

to increased nitrogen and phosphorus loading—Part III:

Periphyton community dynamics:

Homestead, Fla., Everglades

National Park, technical report.

Klein, H., Armbruster, J.T., McPherson, B.F., and Freiberger, H.J.,

1975, Water and the south Florida

environment: U.S. Geological

Survey Water-Resources Investigations 24–75, 165 p.

Majewski, M.S., and Capel, P.D.,

1995, Pesticides in the atmosphere: Distribution, trends, and

governing factors: Pesticides in

the hydrologic system series, v. 1:

Chelsea, Mich., Ann Arbor Press,

214 p.

McCormick, P.V., and O’Dell, M.B.,

1996, Quantifying periphyton

responses to phosphorus in the

Florida Everglades: A synopticexperimental approach: Journal

North American Benthological

Society, v. 15, no. 4, p. 450–468.

McCormick, P., Newman, S., Miao, S.,

Reddy, R., Gawlik, D., Fitz, C.,

Fontaine, T., and Marley, D.,

1999, Ecology needs for the Everglades, in West Palm Beach,

South Florida Water Management

District, Everglades interim

report, p. 3–1 to 3–66.

McPherson, B.F., Hendrix, G.Y.,

Klein, Howard, and Tyus, H.M.,

1976, The environment of south

Florida—A summary report: U.S.

Geological Survey Professional

Paper 1011, 82 p.

McPherson, B.F., and Halley, R., 1996,

The south Florida environment—

A region under stress: U.S. Geological Survey Circular 1134,

61 p.

National Academy of Sciences and

National Academy of Engineering

(NAS/NAE) (1973 [1974]) Water

quality criteria, 1972: Washington, U.S. Environmental Protection Agency Report R3–73–033.

NAWQA NST, 1998, U.S. Geological

Survey, National Water-Quality

Assessment Program, Pesticide

national synthesis project:

accessed August 18, 1998, at

URL http://water.wr.usgs.gov/

pnsp/anstrat/.

Parker, G.G., Ferguson, G.E., Love,

S.K., and others, 1955, Water

resources of southeastern Florida:

U.S. Geological Survey WaterSupply Paper 1255, 965 p.

Price, E.C., Murray, M.H., and Richards, T.E., 1997, Water resources

data, Florida, water year 1996,

south Florida surface water,

Vol. 2A: U.S. Geological Survey

Water-Resources Data Report

FL–96–2A, 401 p.

Scheidt, D.J., Flora, M.D., and Walker,

D.R. , 1987, Water quality management for Everglades National

Park: Paper presented at the North

American Lake Management

Society 75th International Symposium, Orlando, Fla., November 4,

1987, 26 p.

Shelton, L.R., 1994, Field guide for

collecting and processing streamwater samples for the National

Water-Quality Assessment Program: U.S. Geological Survey

Open-File Report 94–455, 42 p.

Stumm, W., and Morgan, J.J., 1981,

Aquatic chemistry—An introduction emphasizing chemical equilibria in natural waters (2d ed.):

New York, John Wiley, 780 p.

Swift, D.R., 1981, Preliminary investigations of periphyton and water

quality in the Everglades Water

Conservation Areas: West Palm

Beach, South Florida Water Management District Technical Publication 81–05.

Swift, D.R., and Nicholas, R.B., 1987,

Periphyton and water quality relationships in the Everglades Water

Conservation Areas 1978–1982:

West Palm Beach, South Florida

Water Management District Technical Publication 87–02.

The National Water-Quality Assessment (NAWQA) Program

In 1991, the U.S. Geological Survey began the NAWQA Program to describe the status of and trends in the quality of a large representative part of

the Nation’s surface- and ground-water resources and to identify the natural

and human factors that affect the quality of these resources. The NAWQA

Program is designed to produce water-quality information that is useful to

policymakers and managers at Federal, State, and local levels. The 60 proposed study units represent 60 to 70 percent of the Nation’s water use and

population served by public water supplies. The Southern Florida study was

begun in 1994.

Hydrologic data and other information

related to the Southern Florida NAWQA

Program can be obtained from:

Project Chief

Southern Florida NAWQA Study

U.S. Geological Survey

4710 Eisenhower Blvd., Suite B5

Tampa, FL 33634

U.S. Geological Survey Water-Resources Investigations Report 99–4062 1999