Cover photograph

View of the Laguna Tortuguero, Vega Baja, Puerto Rico. 

Photograph taken by Francisco Maldonado-Isales, September 2006.
Water-Quality Reconnaissance of Laguna 

Tortuguero, Vega Baja, Puerto Rico, 

March 1999-May 2000

By Luis R. Soler-López, Senén Guzmán-Ríos, and Carlos Conde-Costas

Prepared in cooperation with the

PUERTO RICO ENVIRONMENTAL QUALITY BOARD

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2006-1049
U.S. Department of the Interior

Dirk Kempthorne, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Suggested citation:

Soler-López, L.R., Guzmán-Ríos, Senén, and Conde-Costas, Carlos, 2006, Water-quality evaluation of Laguna 

Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000: U.S. Geological Survey Open-File Report 2006-1049, 19 p.

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.
 iii

Contents

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Methods and Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Water Quality of Laguna Tortuguero. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

References Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figures

1. Map showing location of Laguna Tortuguero, Vega Baja, Puerto Rico, between

the Río Cibuco and the Río Grande de Manatí, east and west of the towns of Manatí

and Vega Baja, respectively. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Map showing location of water-quality stations at Laguna Tortuguero, Vega Baja, 

Puerto Rico. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3. Graphs showing temperature and pH measurements, and dissolved oxygen, total 

nitrogen, and total phosphorus concentration at stations 1, 2, 4, and 5 in and near 

the Laguna Tortuguero, March 1999 to May 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Tables

1. U.S. Geological Survey station identification numbers, station names, and geographic 

coordinates for the Laguna Tortuguero water-quality sampling stations . . . . . . . . . . . . . . . . . . . . . . . . .4

2. Water-quality constituents and physical and biological characteristics analyzed and 

calculated at stations 1, 2, 4, and 5 in the Laguna Tortuguero, Vega Baja, Puerto Rico . . . . . . . . . . . .5

3. Physical parameters at selected water-quality stations in the Laguna 

Tortuguero, Vega Baja, Puerto Rico, from March 1999 to May 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

4. Nitrogen species concentrations at selected water-quality stations in the Laguna 

Tortuguero, Vega Baja, Puerto Rico from March 1999 to May 2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

5. Phosphorus species and organic carbon concentrations at selected water-quality 

stations in the Laguna Tortuguero, Vega Baja, Puerto Rico, from March 1999 to 

May 2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

6. Chlorophyll a and b, and plankton biomass concentrations at selected water-quality 

stations in the Laguna Tortuguero, Vega Baja, Puerto Rico, from March 1999 to 

May 2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7. Total hardness and alkalinity as calcium carbonate, and major ions concentration at 

selected water-quality stations in the Laguna Tortuguero, Vega Baja, Puerto Rico, 

from March 1999 to May 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

8. Diel study data on temperature, specific conductance, dissolved oxygen, and dissolved 

oxygen saturation at selected water-quality stations in the Laguna Tortuguero, 

Vega Baja, Puerto Rico, August 3-4, 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
iv 

Conversion Factors, Water-Quality Units, and Acronyms

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 x °C) + 32

Water-quality units used in this report

μS/cm microsiemens per centimeter

mg/L milligrams per liter

μg/L micrograms per liter

Acronyms used in this report:

PRDNER Puerto Rico Department of Natural and Environmental Resources

PREQB Puerto Rico Environmental Quality Board

USGS U.S. Geological Survey

Multiply By To obtain

Length

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi) 

 Area

hectare (ha) 2.471 acre

Flow rate

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)
Water-Quality Reconnaissance of Laguna Tortuguero, 

Vega Baja, Puerto Rico, March 1999-May 2000

By Luis R. Soler-López, Senén Guzmán-Ríos, and Carlos Conde-Costas

Abstract

The Laguna Tortuguero, a slightly saline to freshwater 

lagoon in north-central Puerto Rico, has a surface area of about 

220 hectares and a mean depth of about 1.2 meters. As part of a 

water-quality reconnaissance, water samples were collected at 

about monthly and near bi-monthly intervals from March 1999 

to May 2000 at four sites: three stations inside the lagoon and 

one station at the artificial outlet channel dredged in 1940, 

which connects the lagoon with the Atlantic Ocean. Physical 

characteristics that were determined from these water samples 

were pH, temperature, specific conductance, dissolved oxygen, 

dissolved oxygen saturation, and discharge at the outlet canal. 

Other water-quality constituents also were determined, 

including nitrogen and phosphorus species, organic carbon, 

chlorophyll a and b, plankton biomass, hardness, alkalinity as 

calcium carbonate, and major ions. Additionally, a diel study 

was conducted at three stations in the lagoon to obtain data on 

the diurnal variation of temperature, specific conductance, 

dissolved oxygen, and dissolved oxygen saturation. The data 

analysis indicates the water quality of Laguna Tortuguero 

complies with the Puerto Rico Environmental Quality Board 

standards and regulations.

Introduction

The Laguna Tortuguero is located in Vega Baja, Puerto 

Rico (fig. 1), about 30 kilometers (km) west of San Juan. This 

slightly saline to freshwater coastal lagoon, with specific 

conductance ranging from 800 to 1,700 microsiemens per 

centimeters (μS/cm) at 25 degrees Celsius (°C), has a surface 

area of about 220 hectares (ha), a maximum depth of about 2.5 

meters (m), and a mean depth of about 1.2 m (Quiñones and 

Fusté, 1977). An artificial outlet channel is present in the northcentral part of the lagoon (fig. 2), which was dredged in 1940. 

Discharge from the lagoon to the Atlantic Ocean is mostly 

ground water, because the lagoon constitutes the principal 

ground-water discharge feature of the North Coast Limestone 

upper aquifer between the Río Grande de Manatí and the Río 

Cibuco (Cherry, 2001) (fig. 2). The Laguna Tortuguero and its 

immediate surroundings were designated a natural reserve area 

by the Puerto Rico Department of Natural and Environmental 

Resources (PRDNER) in 1978, because of its environmental 

uniqueness. The Puerto Rico Environmental Quality Board 

(PREQB) classifies the Laguna Tortuguero as an SE Class 

lagoon, a surface-water body with exceptional ecological value 

(Puerto Rico Environmental Quality Board, 2003). As of today 

(2005), the lagoon is a passive recreational area that also is used 

as a natural "laboratory" for the scientific community.

In 1974-75, a baseline study was conducted to determine 

concentrations of chemical constituents and physical and 

biological characteristics in the Laguna Tortuguero. Additional 

data are needed to evaluate whether any substantial variations 

in water quality have occurred in the lagoon since the prior 

reconnaissance. The U.S. Geological Survey (USGS), in 

cooperation with the PREQB, conducted a study to determine 

concentrations of selected chemical constituents and physical 

and biological characteristics in the Laguna Tortuguero from 

March 1999 to May 2000. The results can be used by water 

managers to implement strategies to protect the lagoon and its 

function as a natural reserve.

Purpose and Scope

The purpose of this report is to present and summarize 

results of a water-quality reconnaissance for selected chemical 

constituents and physical and biological characteristics at four 

sites in and near the Laguna Tortuguero. Determinations were 

made for discharge, pH, temperature, specific conductance, 

dissolved oxygen, dissolved oxygen saturation, nitrogen and 

phosphorus species, organic carbon, chlorophyll a and b, 

plankton biomass, major ions, and alkalinity as calcium 

carbonate. Results also are presented for a diel study that was 

conducted during August 3-4, 2000, at three stations within the 

lagoon to obtain data on the diurnal variations of temperature, 

specific conductance, and dissolved oxygen. Diurnal variations 

in dissolved oxygen can be used in estimating community 

productivity because its concentration in water bodies is 

affected by biological metabolic processes, such as 

photosynthesis and respiration. Community productivity is 

defined as the rate in which new organic matter is created or 

consumed by autotrophic and heterotrophic processes, 

respectively. Aquatic autotrophic organisms produce organic 

matter by photosynthesis (or chemosynthesis) resulting in the 

production of carbohydrates and dissolved oxygen. Aquatic 

heterotrophic organisms incorporate organic matter into their 

tissue by respiration resulting in the synthesis of proteins and 

dissolved oxygen consumption.
Figure 1. Location of Laguna Tortuguero, Vega Baja, Puerto Rico, between the Río Cibuco and the Río Grande de Manatí, east and west of the townrespectively.
Figure 2. Location of water-quality stations at Laguna Tortuguero, Vega Baja, Puerto Rico.
4 Water-Quality Evaluation of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000

Methods and Procedures

Water samples were collected at stations 2, 4, and 5 in the 

Laguna Tortuguero and at station 1 in the outlet channel of the 

lagoon (fig. 2) from March 1999 to May 2000. These sites were 

established to coincide with some of the locations sampled in 

the 1974-75 water-quality reconnaissance study (Quiñones and 

Fusté, 1977). The USGS station identification numbers, station 

names, and geographic coordinates are listed in table 1.

Water-quality constituents that were analyzed in the study 

include physical characteristics (pH, temperature, specific 

conductance, and dissolved oxygen), nitrogen and phosphorus 

species, organic carbon, chlorophyll a and b, plankton biomass, 

hardness, alkalinity as calcium carbonate, and major ions. 

Measurements of pH, temperature, specific conductance, and 

dissolved oxygen were obtained in the field at stations 1, 2, 4, 

and 5 by means of using a water-quality multi-parameter 

instrument. Instantaneous discharge was measured only at the 

outlet channel site (station 1) during sample collection. Surfacewater samples (0.3-m deep) were collected by using the "handdip" method in the lagoon and by using depth- and widthintegration techniques at the outlet channel. Determinations 

were made for nitrogen and phosphorus species, organic 

carbon, chlorophyll a and b, plankton biomass, hardness, 

alkalinity and major ions according to USGS protocols (U.S. 

Geological Survey, 1998). All of these surface-water 

constituents were determined at stations 1, 2, 4, and 5, except 

for chlorophyll a and b, which were determined only at stations 

2, 4, and 5.

The following were collected on a monthly basis: physical 

characteristics (pH, temperature, specific conductance, 

dissolved oxygen, and discharge), dissolved concentration for 

nutrients, total organic carbon concentration, chlorophyll a and 

b concentration, plankton biomass concentration, total hardness 

as calcium carbonate, and dissolved concentrations of major 

ions. The total concentration for nutrients and dissolved organic 

carbon were determined on a near bi-monthly basis. The water 

samples were analyzed at the former USGS Water Quality 

Research Laboratory in Ocala, Florida, and at the USGS 

National Water Quality Laboratory in Denver, Colorado. 

Water-quality constituents and physical and biological 

characteristics that were analyzed for this study are listed in 

table 2.

Table 1. U.S. Geological Survey (USGS) station identification numbers, station names, and geographic 

coordinates for the Laguna Tortuguero water-quality sampling stations.

USGS identification 

number Station name Latitude Longitude 

50038200 Laguna Tortuguero number 1 (outlet) 18°28'29" 66°26'50"

50038191 Laguna Tortuguero number 2 18°27'53" 66°27'50"

50038193 Laguna Tortuguero number 4 18°27'55" 66°26'40"

50038194 Laguna Tortuguero number 5 18°27'52" 66°25'50"
Water Quality of Laguna Tortuguero 5

Water Quality of Laguna Tortuguero

The quality of surface water can be described in terms of 

its chemical constituents and physical and biological 

characteristics. The PREQB standards for SE-Class surfacewater bodies, such as the Laguna Tortuguero, establish that no 

existing natural chemical constituents and physical and 

biological characteristics should be altered by human activities 

in order to preserve their existing natural phenomena and 

processes. Summaries of selected surface-water-quality data 

(March 1999 to May 2000) are presented in tables 3 to 7. 

Specifically, measurements of physical characteristics (pH, 

temperature, specific conductance, dissolved oxygen, and 

discharge) are given in table 3; nitrogen species concentrations 

are given in table 4; phosphorus species and organic carbon 

concentrations are given in table 5; values of biological 

characteristics (chlorophyll a and b and plankton biomass) are 

given in table 6; and concentrations of hardness, alkalinity, and 

major ions are given in table 7. The diel study for temperature, 

specific conductance, dissolved oxygen, and dissolved oxygen 

saturation are presented in table 8.

The Laguna Tortuguero is considered to be in a nearnatural state (Puerto Rico Environmental Quality Board, 2003), 

so there are no specific values and concentrations established 

for the various chemical constituents and physical and 

biological characteristics. Therefore, in order to categorize 

these constituents and characteristics, the water quality of the 

lagoon was compared with the PREQB standards for nearly 

comparable SB-Class water bodies; coastal and estuarine 

waters used for primary and secondary contact (for example, 

fishing and boating) and intended for the propagation and 

preservation of desirable species, including those that are 

threatened or endangered (Puerto Rico Environmental Quality 

Board, 2003). The Laguna Tortuguero fits part of this 

characterization because it is used as a recreational area and 

visitors often wade, fish, and boat in the lagoon.

Determinations of pH, temperature, dissolved oxygen, 

total nitrogen, and total phosphorus were made at stations 1, 2, 

4, and 5 from March 1999 to May 2000 (fig. 3). The PREQB 

regulated standards should be between 7.3 to 8.5 units for pH, 

should not exceed 32.2 °C for temperature, should not be below 

5.0 milligrams per liter (mg/L) for dissolved oxygen, should not 

exceed 5.0 mg/L for total nitrogen concentration, and should 

not exceed 1.0 mg/L for total phosphorus concentration. These 

standards should not be disrupted other than for natural reasons. 

Nearly all of the values and concentrations measured during this 

study were within the standards (fig. 3). However, one pH value 

at station 1 was outside the standard range, three dissolved 

oxygen concentrations at stations 2, 4, and 5 were below the 

standard, and one total nitrogen concentration at station 5 

equaled the standard. The overall results indicate that the water 

quality of Laguna Tortuguero complies with the PREQB 

standards and regulations.

Table 2. Water-quality constituents and physical and biological characteristics analyzed and calculated at stations 1, 2, 4, and 5 

in the Laguna Tortuguero, Vega Baja, Puerto Rico. 

Station name Constituents and physical and biological characteristics

Laguna Tortuguero number 1 pH, temperature, specific conductance, dissolved oxygen, dissolved-oxygen saturation percent, 

nutrients, organic carbon, plankton biomass, hardness as calcium carbonate, major ions, and 

discharge

Laguna Tortuguero number 2 pH, temperature, specific conductance, dissolved oxygen, dissolved-oxygen saturation percent, 

nutrients, organic carbon, chlorophyll a and b, hardness as calcium carbonate, major ions, and 

plankton biomass

Laguna Tortuguero number 4 pH, temperature, specific conductance, dissolved oxygen, dissolved-oxygen saturation percent, 

nutrients, organic carbon, chlorophyll a and b, hardness as calcium carbonate, major ions, and 

plankton biomass

Laguna Tortuguero number 5 pH, temperature, specific conductance, dissolved oxygen, dissolved-oxygen saturation percent, 

nutrients, organic carbon, chlorophyll a and b, hardness as calcium carbonate, major ions, and 

plankton biomass
6 Water-Quality Evaluation of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000

Table 3. Physical parameters at selected water-quality stations in the Laguna Tortuguero, Vega Baja, Puerto Rico, from 

March 1999 to May 2000. 

[pH in standard units; T, temperature in degrees Celsius; SC, specific conductance in microsiemens per centimeter at 25°; DO, 

dissolved oxygen in milligrams per liter; DO sat, dissolved oxygen saturation in percent; Q, discharge in cubic meters per second, 

number in parenthesis is the U.S. Geological Survey laboratory parameter code; ---, no data] 

50038191

Station 2 Time pH (00400) T (00010) SC (00095) DO (00300) DO sat Q (00061)

03/10/1999 1300 8.4 27.8 1,580 9.9 127 ---

04/16/1999 1500 7.9 30.5 1,670 8.7 117 ---

05/14/1999 1030 8.2 29.2 1,720 2.2 29 ---

06/16/1999 1315 7.9 30.9 1,690 9.1 123 ---

07/16/1999 1235 8.0 28.9 1,590 8.6 112 ---

08/20/1999 1300 7.4 31.3 1,540 7.9 108 ---

09/17/1999 1350 7.9 31.3 1,540 9.2 112 ---

10/15/1999 1400 7.9 29.9 1,500 8.2 109 ---

11/19/1999 1200 7.4 26.4 1,200 6.7 84 ---

12/20/1999 1215 8.1 25.7 1,130 9.0 110 ---

01/21/2000 1330 7.8 24.8 1,110 8.6 104 ---

02/17/2000 1300 8.2 26.6 1,180 10.2 128 ---

03/22/2000 1300 --- --- --- --- --- ---

05/04/2000 1320 --- --- --- --- --- ---

 Mean 7.9 28.6 1,450 8.2 105

50038193

Station 4 Time pH T SC DO DO sat Q

03/10/1999 1530 8.4 28.0 1,060 9.6 124 ---

04/16/1999 1440 8.0 30.1 1,140 8.7 115 ---

05/14/1999 1145 8.4 29.3 1,180 2.4 31 ---

06/16/1999 1650 8.4 30.8 1,150 8.7 117 ---

07/16/1999 1220 8.1 29.0 1,140 7.6 99 ---

08/20/1999 1440 8.1 31.3 1,140 7.6 104 ---

09/17/1999 1450 8.1 31.5 1,140 9.3 127 ---

10/15/1999 1530 8.1 29.8 1,100 8.9 118 ---

11/19/1999 1315 7.7 26.7 920 6.4 80 ---

12/20/1999 1400 8.0 25.6 840 9.8 120 ---

01/21/2000 1400 8.0 24.8 790 9.0 110 ---

02/17/2000 1420 8.0 26.6 820 10.5 131 ---

03/22/2000 1410 --- --- --- --- --- ---

05/04/2000 1430 --- --- --- --- --- ---

 Mean 8.1 28.6 1,030 8.2 106
Water Quality of Laguna Tortuguero 7

50038194

Station 5 Time pH T SC DO DO sat Q

03/10/1999 1640 8.4 27.9 1,060 10.1 129 ---

04/16/1999 1550 7.9 30.3 1,120 9.1 122 ---

05/14/1999 1415 8.4 29.7 1,150 2.9 38 ---

06/16/1999 1600 8.4 30.9 1,150 9.0 121 ---

07/16/1999 1425 8.1 29.4 1,160 9.1 120 ---

08/20/1999 1615 8.3 31.8 1,120 8.0 110 ---

09/17/1999 1545 8.3 31.8 1,140 9.8 135 ---

10/15/1999 1645 8.3 29.9 1,090 9.4 124 ---

11/19/1999 1345 7.8 26.9 960 7.9 99 ---

12/20/1999 1445 8.2 25.7 830 9.2 112 ---

01/21/2000 1415 8.1 24.6 780 9.6 116 ---

02/17/2000 1520 8.3 26.8 820 11.3 142 ---

03/22/2000 1450 --- --- --- --- --- ---

05/04/2000 1400 --- --- --- --- --- ---

 Mean 8.2 28.8 1,030 8.8 114

50038200

Station 1 Time pH T SC DO DO sat Q

03/10/1999 1200 7.8 27.5 1,010 6.4 82 0.14

04/21/1999 1210 7.8 29.5 1,100 6.2 82 0.17

05/14/1999 1100 7.9 29.5 1,160 6.8 90 0.17

06/16/1999 1230 8.1 31.0 710 6.2 84 0.27

07/16/1999 1330 7.8 29.7 1,070 6.6 90 0.48

08/20/1999 1315 7.9 31.5 1,170 6.2 85 0.27

09/17/1999 1430 8.1 31.5 1,140 9.3 87 0.35

10/15/1999 1355 7.1 30.0 1,080 6.4 85 0.28

11/19/1999 1230 7.7 26.7 860 6.4 80 1.09

12/20/1999 1220 7.7 25.5 820 7.0 86 0.98

01/21/2000 1355 7.9 24.5 780 7.5 90 0.78

02/17/2000 1340 8.0 27.0 810 7.4 93 0.48

03/22/2000 1330 --- --- --- --- --- ---

05/04/2000 --- --- --- --- --- --- ---

 Mean 7.8 28.7 980 6.9 86

Table 3. Physical parameters at selected water-quality stations in the Laguna Tortuguero, Vega Baja, Puerto Rico, from 

March 1999 to May 2000. —Continued

[pH in standard units; T, temperature in degrees Celsius; SC, specific conductance in microsiemens per centimeter at 25°; DO, 

dissolved oxygen in milligrams per liter; DO sat, dissolved oxygen saturation in percent; Q, discharge in cubic meters per second, 

number in parenthesis is the U.S. Geological Survey laboratory parameter code; ---, no data]
8 Water-Quality Evaluation of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000

Table 4. Nitrogen species concentrations at selected water-quality stations in the Laguna Tortuguero, Vega Baja, Puerto Rico from 

March 1999 to May 2000. 

[All concentrations are in milligrams per liter and expressed as N, except where indicated. Number in parenthesis is the U.S. Geological Survey 

laboratory parameter code; ---, no data; <, less than] 

Date Time

Ammonia, 

dissolved 

(00608)

Ammonia, 

total 

(00610)

Nitrite, 

dissolved 

(00613)

Nitrite 

total 

(0015)

Nitrite 

plus 

nitrate, 

dissolved 

(00631)

Nitrite 

plus 

nitrate, 

total 

(00630)

Organic 

nitrogen, 

dissolved 

(00607)

Organic 

nitrogen, 

total 

(00605)

Nitrogen, 

total as N 

(00600)

Nitrogen, 

total as 

NO3

(71887)

50038191 Laguna Tortuguero number 2

03/10/1999 1300 0.06 --- <0.01 <0.01 0.11 --- 0.40 --- 0.58 ---

04/16/1999 1500 0.28 0.29 0.01 0.01 0.22 0.23 0.80 1.21 1.73 ---

05/14/1999 1030 0.47 0.47 <0.01 <0.01 0.21 0.22 0.60 1.13 1.82 ---

06/16/1999 1315 0.24 0.15 0.02 0.01 0.25 0.24 0.59 0.72 1.14 5.05

07/16/1999 1235 0.11 --- <0.01 --- 0.14 --- 0.77 --- 1.01 ---

08/20/1999 1300 0.19 0.20 <0.01 <0.01 0.13 0.14 0.77 0.8 1.14 5.05

09/17/1999 1350 0.26 --- <0.01 --- 0.20 --- 0.57 --- 1.07 ---

10/15/1999 1400 0.28 0.27 <0.01 <0.01 0.18 0.18 0.67 0.83 1.28 5.67

11/19/1999 1200 0.23 --- <0.01 --- 0.12 --- 0.69 --- 1.04 ---

12/20/1999 1215 0.18 0.19 0.01 <0.01 0.21 0.21 0.50 0.74 1.11 4.91

01/21/2000 1330 0.16 --- <0.01 --- 0.19 --- 0.51 --- --- ---

02/17/2000 1300 0.13 0.15 <0.01 <0.01 0.21 0.19 0.55 0.71 1.09 4.82

03/22/2000 1300 0.11 --- <0.01 --- --- --- 0.58 --- --- ---

05/04/2000 1320 0.22 0.22 0.01 0.01 0.34 0.34 0.70 1.08 1.64 7.26

 Mean 0.21 0.24 0.01 0.01 0.19 0.22 0.62 0.90 1.17 5.46

50038193 Laguna Tortuguero number 4

03/10/1999 1530 0.09 --- 0.01 --- 0.34 --- 0.41 --- 0.84 ---

04/16/1999 1440 0.21 0.22 <0.01 0.01 0.42 0.43 0.68 0.98 1.63 ---

05/14/1999 1145 0.23 0.26 0.01 0.01 0.52 0.53 0.90 1.04 1.62 ---

06/16/1999 1650 0.13 0.14 0.02 0.02 0.38 0.38 0.75 0.86 1.38 6.11

07/16/1999 1220 0.19 --- <0.01 --- 0.43 --- 0.64 --- 1.27 ---

08/20/1999 1440 0.26 0.27 <0.01 0.01 0.41 0.40 0.69 1.03 1.70 7.53

09/17/1999 1450 0.28 --- 0.01 --- 0.42 --- 0.47 --- 1.19 ---

10/15/1999 1530 0.28 0.29 0.02 0.02 0.45 0.45 0.56 0.81 1.55 6.86

11/19/1999 1315 0.25 --- 0.01 --- 0.52 --- 0.66 --- 1.43 ---

12/20/1999 1400 0.29 0.29 0.02 0.03 1.90 1.90 0.40 0.53 2.70 12.0

01/21/2000 1400 0.23 --- 0.02 --- 1.20 --- 0.33 --- 1.76 ---

02/17/2000 1420 0.24 0.27 0.02 0.03 1.10 1.10 0.73 0.56 1.90 8.41

03/22/2000 1410 0.23 --- 0.08 --- 0.83 1.00 0.53 --- 2.00 8.85

05/04/2000 1430 0.20 0.21 0.02 0.02 0.58 0.58 0.61 0.70 1.49

 Mean 0.22 0.24 0.02 0.02 0.68 0.72 0.60 0.81 1.58 8.29
Water Quality of Laguna Tortuguero 9

50038194 Laguna Tortuguero number 5

03/10/1999 1640 0.07 --- 0.01 --- 0.27 --- 0.44 --- --- ---

04/16/1999 1550 0.14 0.18 <0.01 0.01 0.18 0.24 0.8 1.42 1.84 ---

05/14/1999 1415 0.17 0.22 <0.01 <0.01 0.27 0.26 0.75 4.48 4.96 ---

06/16/1999 1600 0.10 0.10 0.01 0.01 0.23 0.23 0.66 0.72 1.03 4.56

07/16/1999 1425 0.08 --- <0.01 --- 0.18 --- 0.71 --- --- ---

08/20/1999 1615 0.12 0.12 0.01 <0.01 0.13 0.12 0.75 0.88 1.12 4.96

09/17/1999 1545 0.20 <0.01 --- 0.23 --- 0.48 --- 0.91 ---

10/15/1999 1645 0.19 0.21 0.01 0.01 0.26 0.27 0.73 0.79 1.27 5.62

11/19/1999 1345 0.20 --- 0.01 --- 0.27 --- 0.68 --- --- ---

12/20/1999 1445 0.27 0.28 0.02 0.02 1.30 1.30 0.53 0.40 2.00 8.85

01/21/2000 1415 0.27 --- 0.03 --- 1.40 --- 0.39 --- 2.06 ---

02/17/2000 1520 0.23 0.24 0.02 0.02 1.00 1.10 0.43 0.49 1.80 7.97

03/22/2000 1450 0.20 --- 0.02 --- 0.70 1.00 0.47 --- 2.00 8.85

05/04/2000 1400 0.18 0.20 0.02 0.02 0.54 0.54 0.48 1.10 1.84 8.14

 Mean 0.17 0.19 0.01 0.01 0.50 0.51 0.59 1.29 1.65 6.99

50038200 Laguna Tortuguero number 1

03/10/1999 1200 0.19 0.19 0.01 0.01 0.31 0.32 0.47 0.74 1.25 ---

04/21/1999 1210 0.28 0.28 0.01 0.01 0.31 0.30 0.82 1.02 1.61 ---

05/14/1999 1100 0.30 0.31 0.01 0.01 0.54 0.54 0.67 1.09 1.94 ---

06/16/1999 1230 0.22 0.23 0.02 0.02 0.40 0.41 0.65 0.87 1.51 6.68

07/16/1999 1330 --- --- --- --- --- --- --- --- --- ---

08/20/1999 1315 0.26 0.27 <0.01 <0.01 0.25 0.25 0.73 0.93 1.45 6.42

09/17/1999 1430 0.29 --- 0.02 --- 0.35 --- 0.61 --- --- ---

10/15/1999 1355 0.32 0.33 0.02 0.02 0.44 0.45 0.78 0.87 1.65 7.30

11/19/1999 1230 0.25 --- 0.01 --- 0.40 --- 0.73 --- --- ---

12/20/1999 1220 0.28 0.28 0.03 0.03 1.40 1.40 0.56 0.57 2.25 10.2

01/21/2000 1355 0.26 --- 0.03 --- 1.40 --- 0.44 --- --- ---

02/17/2000 1340 0.27 0.29 0.03 0.02 1.10 1.10 0.43 0.51 1.90 8.41

03/22/2000 1330 0.30 --- 0.02 --- 0.75 1.00 --- --- --- 8.85

05/04/2000 --- --- --- --- --- --- --- ---

 Mean 0.26 0.27 0.02 0.02 0.64 0.33 0.63 0.83 1.70 7.98

Date Time

Ammonia, 

dissolved 

(00608)

Ammonia, 

total 

(00610)

Nitrite, 

dissolved 

(00613)

Nitrite 

total 

(0015)

Nitrite 

plus 

nitrate, 

dissolved 

(00631)

Nitrite 

plus 

nitrate, 

total 

(00630)

Organic 

nitrogen, 

dissolved 

(00607)

Organic 

nitrogen, 

total 

(00605)

Nitrogen, 

total as N 

(00600)

Nitrogen, 

total as 

NO3

(71887)

Table 4. Nitrogen species concentrations at selected water-quality stations in the Laguna Tortuguero, Vega Baja, Puerto Rico from 

March 1999 to May 2000.—Continued

[All concentrations are in milligrams per liter and expressed as N, except where indicated. Number in parenthesis is the U.S. Geological Survey 

laboratory parameter code; ---, no data; <, less than] 
10 Water-Quality Evaluation of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000

Table 5. Phosphorus species and organic carbon concentrations at selected water-quality stations in the Laguna Tortuguero, 

Vega Baja, Puerto Rico, from March 1999 to May 2000. 

[All concentrations are in milligrams per liter. Number in parenthesis is the U.S. Geological Survey laboratory parameter code; ---, no data; 

E, estimated; <, less than] 

Date Time

Phosphorus, 

dissolved

as P

(00666)

Phosphorus, 

total as P

(00665)

Ortho 

phosphorus,

dissolved

as P

(00671)

Ortho 

phosphorus,

total as P 

(70507)

Ortho 

phosphate,

dissolved 

as PO4

(00660)

Organic 

carbon, 

total 

as C

(00680)

Organic

carbon,

dissolved

as C

(00681)

50038191 Laguna Tortuguero number 2

03/10/1999 1300 < 0.02 --- <0.01 --- --- 9.3 ---

04/16/1999 1500 < 0.02 < 0.02 <0.01 0.01 --- 9.5 9.0

05/14/1999 1030 < 0.02 < 0.02 <0.01 0.01 --- 9.7 ---

06/16/1999 1315 < 0.02 < 0.02 <0.01 0.01 --- 12.0 11.0

07/16/1999 1235 < 0.02 --- <0.01 --- --- 8.8 ---

08/20/1999 1300 < 0.02 < 0.02 <0.01 0.01 --- 8.9 8.9

09/17/1999 1350 < 0.02 --- <0.01 --- --- 8.7 ---

10/15/1999 1400 < 0.02 < 0.02 <0.01 0.01 --- 8.4 7.9

11/19/1999 1200 < 0.02 --- 0.03 --- 0.09 7.7 ---

12/20/1999 1215 < 0.02 < 0.02 0.03 0.03 0.09 10.0 8.9

01/21/2000 1330 < 0.02 --- 0.01 --- 0.03 8.8 ---

02/17/2000 1300 < 0.02 < 0.02 0.02 0.01 0.06 8.7 8.7

03/22/2000 1300 < 0.02 --- 0.01 --- --- 9.0 ---

05/04/2000 1320 < 0.02 < 0.02 <0.01 0.01 --- 10.0 9.6

 Mean 0.02 <0.01 0.01 0.07 9.2 9.1

 50038193 Laguna Tortuguero number 4

03/10/1999 1530 < 0.02 --- <0.01 --- --- 8.5 ---

04/16/1999 1440 E 0.02 < 0.02 <0.01 0.01 --- 9.5 9.1

05/14/1999 1145 < 0.02 < 0.02 <0.01 0.01 --- 9.7 ---

06/16/1999 1650 E 0.02 0.02 0.02 0.01 0.06 12.0 9.6

07/16/1999 1220 0.04 --- <0.01 --- --- 8.5 ---

08/20/1999 1440 < 0.02 < 0.02 <0.01 0.01 --- 8.9 8.3

09/17/1999 1450 < 0.02 --- <0.01 --- --- 8.8 ---

10/15/1999 1530 < 0.02 < 0.02 <0.01 0.01 --- 8.2 7.9

11/19/1999 1315 < 0.02 --- 0.02 --- 0.06 7.5 ---

12/20/1999 1400 < 0.02 < 0.02 0.03 0.03 0.09 6.3 5.6

01/21/2000 1400 < 0.02 --- 0.02 --- 0.06 6.1 ---

02/17/2000 1420 0.02 < 0.02 <0.01 0.01 --- 9.1 5.8

03/22/2000 1410 < 0.02 --- <0.01 --- --- 6.0 ---

05/04/2000 1430 < 0.02 < 0.02 <0.01 0.01 --- 9.2 7.5

 Mean 0.02 0.02 0.01 0.01 0.07 8.6 8.0
Water Quality of Laguna Tortuguero 11

50038194 Laguna Tortuguero number 5

03/10/1999 1640 < 0.02 --- < 0.01 --- --- 8.6 ---

04/16/1999 1550 < 0.02 < 0.02 < 0.01 0.01 --- 9.9 9.6

05/14/1999 1415 < 0.02 E 0.03 0.01 0.01 --- 10.0 ---

06/16/1999 1600 < 0.02 < 0.02 < 0.01 0.01 --- 10.0 8.9

07/16/1999 1425 < 0.02 --- < 0.01 --- --- 9.1 ---

08/20/1999 1615 < 0.02 < 0.02 < 0.01 0.01 --- 10.0 8.8

09/17/1999 1545 < 0.02 --- < 0.01 --- --- 9.2 ---

10/15/1999 1645 < 0.02 0.02 < 0.01 0.01 --- 8.2 7.9

11/19/1999 1345 < 0.02 --- 0.02 --- 0.06 7.5 ---

12/20/1999 1445 0.02 0.02 0.01 0.01 0.09 6.4 6.2

01/21/2000 1415 < 0.02 --- 0.02 --- 0.06 6.0 ---

02/17/2000 1520 < 0.02 0.02 < 0.01 0.01 --- 7.8 5.8

03/22/2000 1450 < 0.02 --- < 0.01 --- --- 6.6 ---

05/04/2000 1400 < 0.02 0.02 < 0.01 0.01 --- 8.0 7.7

 Mean 0.02 < 0.01 0.01 0.07 8.4 7.8

50038200 Laguna Tortuguero number 1

03/10/1999 1200 < 0.02 < 0.02 < 0.01 0.01 --- 8.5 ---

04/21/1999 1210 E 0.03 < 0.02 < 0.01 0.01 0.03 9.5 9.5

05/14/1999 1100 < 0.02 < 0.02 < 0.01 0.01 --- 9.2 ---

06/16/1999 1230 < 0.02 < 0.02 < 0.01 0.01 --- 10.0 9.3

07/16/1999 1330 --- --- --- --- --- 9.6 ---

08/20/1999 1315 < 0.02 < 0.02 < 0.01 < 0.01 --- 9.3 8.7

09/17/1999 1430 < 0.02 --- < 0.01 < 0.01 --- 8.9 ---

10/15/1999 1355 < 0.02 < 0.02 < 0.01 < 0.01 0.06 8.2 7.9

11/19/1999 1230 < 0.02 < 0.02 0.03 --- 0.09 8.4 ---

12/20/1999 1220 < 0.02 < 0.02 < 0.02 < 0.01 0.06 10.2 6.2

01/21/2000 1355 0.01 --- 0.01 --- 0.03 5.5 ---

02/17/2000 1340 < 0.02 < 0.02 < 0.01 < 0.01 --- 5.9 5.7

03/22/2000 1330 --- --- --- --- --- 6.3 ---

05/04/2000 --- --- --- --- --- --- --- ---

 Mean 0.01 0.01 0.01 < 0.01 0.05 8.4 7.9

Date Time

Phosphorus, 

dissolved

as P

(00666)

Phosphorus, 

total as P

(00665)

Ortho 

phosphorus,

dissolved

as P

(00671)

Ortho 

phosphorus,

total as P 

(70507)

Ortho 

phosphate,

dissolved 

as PO4

(00660)

Organic 

carbon, 

total 

as C

(00680)

Organic

carbon,

dissolved

as C

(00681)

Table 5. Phosphorus species and organic carbon concentrations at selected water-quality stations in the Laguna Tortuguero, 

Vega Baja, Puerto Rico, from March 1999 to May 2000. —Continued

[All concentrations are in milligrams per liter. Number in parenthesis is the U.S. Geological Survey laboratory parameter code; ---, no data; 

E, estimated; <, less than] 
12 Water-Quality Evaluation of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000

Table 6. Chlorophyll a and b, and plankton biomass concentration at selected water-quality stations in the Laguna Tortuguero, Vega 

Baja, Puerto Rico, from March 1999 to May 2000. 

[Chlorophyll a and b in micrograms per liter, plankton biomass in milligrams per liter; Number in parenthesis is the U.S. Geological Survey 

laboratory parameter code; ---, no data; <, less than].

Date Time

Chlorophyll a 

(70953)

Chlorophyll b

(70954)

Biomass, 

plankton, 

dry 

weight

(81354) 

Biomass, 

plankton, 

ash 

weight 

(81353)

Biomass, 

plankton, 

ash-free 

weight 

(49953) 

Time

Chlorophyll a 

(70953)

Chlorophyll b

(70954)

Biomass, 

plankton, 

dry 

weight 

(81354) 

Biomass, 

plankton, 

ash 

weight 

(81353)

Biomass, 

plankton, 

ash-free 

weight 

(49953) 

50038191 Laguna Tortuguero number 2 50038193 Laguna Tortuguero number 4

03/10/1999 1300 0.57 <0.10 276.4 271.2 5.2 1530 2.20 <0.1 261.4 254.8 6.6

04/16/1999 1500 2.60 <0.10 459.7 447.3 12.4 1440 2.00 <0.1 456.3 445.7 10.6

05/14/1999 1030 0.76 <0.10 272.0 264.8 7.2 1145 0.51 <0.1 279.2 271.6 7.6

06/16/1999 1315 2.30 <0.10 275.0 268.2 6.8 1650 2.10 <0.1 266.6 261.4 5.2

07/16/1999 1235 1.20 <0.10 271.4 264.8 6.6 1220 2.30 <0.1 274.0 267.4 6.6

08/20/1999 1300 0.83 <0.10 273.2 267.8 5.4 1440 1.10 <0.1 273.6 267.2 6.4

09/17/1999 1350 1.10 <0.10 272.6 267.2 5.4 1450 1.50 <0.1 276.2 270.0 6.2

10/15/1999 1400 1.20 <0.10 271.4 264.2 7.2 1530 1.80 <0.1 275.0 267.4 7.6

11/19/1999 1200 1.80 <0.10 263.6 258.2 5.4 1315 1.40 <0.1 270.4 263.6 6.8

12/20/1999 1215 2.30 <0.10 261.2 254.8 6.4 1400 1.60 <0.1 271.2 265.4 5.8

01/21/2000 1330 1.90 <0.10 274.2 268.4 5.8 1400 1.20 <0.1 272.4 266.6 5.8

02/17/2000 1300 2.20 <0.10 277.8 270.6 7.2 1420 1.60 <0.1 271.2 264.8 6.4

03/22/2000 1300 2.10 <0.10 366.4 356.8 9.6 1410 1.70 <0.1 268.2 274.4 6.2

05/04/2000 1320 2.60 <0.10 305.3 297.6 7.7 1430 1.60 <0.1 339.3 336.8 2.5

 Mean 1.70 <0.10 294.3 287.3 7.0 1.60 <0.1 290.1 283.6 6.5

50038194 Laguna Tortuguero number 5 50038200 Laguna Tortuguero number 1

03/10/1999 1640 0.76 <0.10 272.6 268.4 4.2 1200 --- --- --- --- ---

04/16/1999 1550 1.30 <0.10 460.0 448.7 11.3 1210 --- --- 281.6 272.6 9.0

05/14/1999 1415 0.58 <0.10 262.8 257.4 5.4 1100 --- --- 275.4 268.8 6.6

06/16/1999 1600 1.80 <0.10 260.0 254.2 5.8 1230 --- --- 277.2 270.4 6.8

07/16/1999 1425 1.80 <0.10 273.8 267.6 6.2 1330 --- --- 275.4 268.6 6.8

08/20/1999 1615 0.79 <0.10 286.4 278.2 8.2 1315 --- --- 281.4 276.0 5.4

09/17/1999 1545 2.30 <0.10 273.0 267.2 5.8 1430 --- --- 274.8 268.6 6.2

10/15/1999 1645 1.30 <0.10 268.0 261.0 7.0 1355 --- --- 273.0 265.8 7.2

11/19/1999 1345 1.10 <0.10 264.8 258.2 6.6 1230 --- --- 276.4 269.4 7.0

12/20/1999 1445 1.60 <0.10 267.2 261.0 6.2 1220 --- --- 274.8 268.6 6.2

01/21/2000 1415 0.99 <0.10 271.4 266.2 5.2 1355 --- --- 275.6 270.2 5.4

02/17/2000 1520 1.80 <0.10 273.0 267.2 5.8 1340 --- --- 275.2 269.0 6.2

03/22/2000 1450 1.30 <0.10 305.6 298.4 7.2 1330 --- --- 269.4 262.8 6.6

05/04/2000 1400 1.90 <0.10 343.0 335.7 7.3 --- --- --- --- --- ---

 Mean 1.40 <0.10 291.5 285.0 6.5 1200 --- --- 300.9 293.7 6.6
Water Quality of Laguna Tortuguero 13

Table 7. Total hardness and alkalinity as calcium carbonate, and major ions concentration at selected water-quality stations in the 

Laguna Tortuguero, Vega Baja, Puerto Rico, from March 1999 to May 2000. 

[All concentrations are in milligrams per liter. Number in parenthesis is the U.S. Geological Survey laboratory parameter code; ---, no data; <, 

less than]

Date Time 

Hardness, 

total as 

CaCO3

(00900)

Acid 

neutralizing 

capacity 

as CaCO3 

(00410) 

Calcium, dissolved 

as Ca

(00915)

Magnesium, 

dissolved 

as Mg 

(00925)

Potassium, 

dissolved 

as K 

(00935)

Sodium, 

dissolved

As Na 

(00930)

Chloride,

dissolved

as Cl 

(00940)

Fluoride,

dissolved 

as F 

(00950)

Silica, 

dissolved 

as SiO2 

(00955)

Sulfate, 

dissolved 

as SO4

 (00945)

50038191 Laguna Tortuguero number 2

03/10/1999 1300 239 116 56 24 5.4 200 380 <0.1 5.7 46

04/16/1999 1500 245 116 57 25 5.9 210 410 <0.1 7.9 50

05/14/1999 1030 274 125 65 27 7.0 220 420 <0.1 9.4 51

06/16/1999 1315 256 105 58 27 6.3 230 410 <0.1 9.3 55

07/16/1999 1235 212 93 47 23 5.2 190 370 <0.1 8.0 48

08/20/1999 1300 249 100 57 26 5.8 190 390 <0.1 11.0 50

09/17/1999 1350 237 110 57 23 5.2 190 360 <0.1 11.0 47

10/15/1999 1400 223 --- 53 22 5.1 180 360 <0.1 10.0 46

11/19/1999 1200 194 97 48 18 4.0 140 280 <0.1 8.7 35

12/20/1999 1215 204 --- 52 18 3.7 130 260 <0.1 8.0 31

01/21/2000 1330 200 --- 52 17 3.8 120 240 <0.1 7.0 29

02/17/2000 1300 211 121 55 18 4.0 140 270 <0.1 6.4 32

03/22/2000 1300 --- --- --- --- --- --- --- --- --- ---

05/04/2000 1320 --- --- --- --- --- --- --- --- --- ---

 Mean 229 109 55 22 5.1 178 346 <0.1 8.5 43

50038193 Laguna Tortuguero number 4

03/10/1999 1530 189 112 46 18 3.5 120 230 <0.1 6.3 27

04/16/1999 1440 195 115 45 20 4.3 130 260 <0.1 7.7 31

05/14/1999 1145 206 115 48 21 3.9 130 260 <0.1 9.2 33

06/16/1999 1650 198 98 43 22 4.6 150 270 <0.1 9.9 34

07/16/1999 1220 199 110 45 21 4.3 140 240 <0.1 9.2 30

08/20/1999 1440 206 --- 48 21 4.5 150 270 <0.1 10.0 33

09/17/1999 1450 207 120 50 20 3.9 130 240 <0.1 10.0 30

10/15/1999 1530 211 --- 53 19 4.2 120 250 <0.1 11.0 29

11/19/1999 1315 183 115 47 16 3.2 95 180 <0.1 9.0 23

12/20/1999 1400 214 --- 61 15 2.5 73 150 <0.1 7.7 20

01/21/2000 1400 198 --- 56 14 2.5 70 130 <0.1 7.0 18

02/17/2000 1420 193 139 54 14 2.6 76 150 <0.1 6.3 20

03/22/2000 1410 191 --- 50 16 3.0 95 180 --- 6.5 23

05/04/2000 1430 193 --- 46 19 3.6 110 220 --- 7.9 29

 Mean 199 116 49 18 3.6 114 216 <0.1 8.4 27
14 Water-Quality Evaluation of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000

50038194 Laguna Tortuguero number 5

03/10/1999 1640 191 114 45 19 3.6 120 240 <0.1 6.3 27

04/16/1999 1550 187 107 42 20 4.3 140 260 <0.1 7.9 31

05/14/1999 1415 199 107 45 21 4.8 140 260 <0.1 9.2 33

06/16/1999 1600 189 94 41 21 4.6 150 280 <0.1 9.9 35

07/16/1999 1425 185 92 41 20 4.4 140 250 <0.1 9.5 31

08/20/1999 1615 196 100 44 21 4.2 140 260 <0.1 10.0 32

09/17/1999 1545 197 100 46 20 4.1 140 240 <0.1 10.0 30

10/15/1999 1645 205 --- 49 20 4.2 120 250 <0.1 11.0 29

11/19/1999 1345 176 103 44 16 3.3 110 200 <0.1 8.8 25

12/20/1999 1445 202 --- 56 15 2.7 78 150 <0.1 8.0 20

01/21/2000 1415 195 --- 55 14 2.5 69 140 <0.1 7.0 18

02/17/2000 1520 188 136 52 14 2.6 78 140 <0.1 6.3 19

03/22/2000 1450 186 --- 48 16 2.9 92 180 --- 6.5 23

05/04/2000 1400 196 --- 47 19 3.5 110 220 --- 8.0 29

 Mean 192 106 47 18 3.7 116 219 <0.1 8.5 27

50038200 Laguna Tortuguero number 1

03/10/1999 1200 198 120 48 19 3.8 120 230 <0.1 6.4 28

04/21/1999 1210 214 110 51 21 4.5 140 270 <0.1 8.4 33

05/14/1999 1100 215 120 50 22 5.2 140 280 <0.1 9.2 33

06/16/1999 1230 205 110 46 22 4.8 150 280 <0.1 10.0 34

07/16/1999 1330 190 100 43 20 4.4 140 240 <0.1 8.8 32

08/20/1999 1315 204 110 47 21 4.5 150 270 <0.1 10.0 33

09/17/1999 1430 205 110 49 20 4.1 130 250 <0.1 10.0 30

10/15/1999 1355 217 120 54 20 4.3 120 250 <0.1 11.0 30

11/19/1999 1230 174 112 45 15 3.2 92 180 <0.1 8.4 23

12/20/1999 1220 204 125 57 15 2.7 70 150 <0.1 7.8 20

01/21/2000 1355 200 149 57 14 2.5 70 140 <0.1 6.8 19

02/17/2000 1340 190 143 54 14 2.6 77 150 <0.1 6.3 20

03/22/2000 1330 191 --- 50 16 3.0 94 180 < 0.1 6.5 23

05/04/2000 --- --- --- --- --- --- --- --- --- --- ---

 Mean 200 119 50 19 3.9 117 224 <0.1 8.6 28

Date Time 

Hardness, 

total as 

CaCO3

(00900)

Acid 

neutralizing 

capacity 

as CaCO3 

(00410) 

Calcium, dissolved 

as Ca

(00915)

Magnesium, 

dissolved 

as Mg 

(00925)

Potassium, 

dissolved 

as K 

(00935)

Sodium, 

dissolved

As Na 

(00930)

Chloride,

dissolved

as Cl 

(00940)

Fluoride,

dissolved 

as F 

(00950)

Silica, 

dissolved 

as SiO2 

(00955)

Sulfate, 

dissolved 

as SO4

 (00945)

Table 7. Total hardness and alkalinity as calcium carbonate, and major ions concentration at selected water-quality stations in the 

Laguna Tortuguero, Vega Baja, Puerto Rico, from March 1999 to May 2000.—Continued

[All concentrations are in milligrams per liter. Number in parenthesis is the U.S. Geological Survey laboratory parameter code; ---, no data; 

<, less than]
Water Quality of Laguna Tortuguero 15

Table 8. Diel study data on temperature, specific conductance, dissolved oxygen, and dissolved oxygen saturation, at selected waterquality stations in the Laguna Tortuguero, Vega Baja, Puerto Rico, August 3-4, 2000. 

[Temperature in degrees Celsius; specific conductance in microsiemens per centimeter at 25°; dissolved oxygen in milligrams per liter; 

dissolved oxygen saturation in percent] 

Date Time Temperature

Specific 

conductance

Dissolved 

oxygen

Dissolved 

oxygen 

saturation

Time Temperature

Specific 

conductance

Dissolved 

oxygen

Dissolved 

oxygen 

saturation

50038191 Laguna Tortuguero number 2 50038193 Laguna Tortuguero number 4

08/03/2000 1042 29.84 1,500 8.08 107 1030 29.52 1,100 7.62 100

08/03/2000 1140 29.89 1,500 8.27 110 1130 29.57 1,100 7.58 100

08/03/2000 1242 30.12 1,500 8.68 115 1230 29.85 1,100 8.43 112

08/03/2000 1340 30.40 1,500 8.28 111 1330 29.97 1,100 8.12 108

08/03/2000 1440 30.69 1,500 7.75 105 1433 30.20 1,100 7.50 100

08/03/2000 1547 30.98 1,500 7.75 105 1540 30.38 1,100 7.70 103

08/03/2000 1646 31.06 1,500 8.30 113 1637 30.39 1,100 8.15 110

08/03/2000 1745 31.01 1,500 8.44 114 1737 30.36 1,100 7.88 106

08/03/2000 1847 30.91 1,500 8.24 112 1838 30.47 1,100 8.05 108

08/03/2000 1950 30.71 1,500 8.04 108 1940 30.36 1,100 7.72 104

08/03/2000 2110 30.53 1,500 7.84 105 2056 30.24 1,100 7.52 100

08/03/2000 2215 30.43 1,500 7.66 103 2210 29.92 1,100 7.50 100

08/03/2000 2310 30.22 1,500 7.47 99 2300 29.93 1,100 7.53 100

08/04/2000 0018 30.11 1,500 7.48 99 0007 29.90 1,100 7.48 99

08/04/2000 0100 29.90 1,500 7.65 102 0110 29.60 1,100 7.35 97

08/04/2000 0210 29.90 1,500 7.27 97 0220 29.50 1,100 6.88 91

08/04/2000 0307 29.81 1,500 7.18 95 0315 29.34 1,100 6.84 90

08/04/2000 0410 29.75 1,500 7.18 95 0420 29.30 1,100 6.89 91

08/04/2000 0513 29.63 1,500 6.98 92 0522 29.21 1,100 6.79 89

08/04/2000 0605 29.60 1,500 7.51 99 0614 29.19 1,100 7.29 95

080/4/2000 0700 29.53 1,500 7.49 99 0710 29.18 1,100 7.26 95

08/04/2000 0810 29.51 1,500 8.01 106 0823 29.21 1,100 7.83 102
16 Water-Quality Evaluation of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000

Date Time Temperature

Specific 

conductance

Dissolved 

oxygen

Dissolved 

oxygen 

saturation

50038194 Laguna Tortuguero number 5

08/03/2000 1020 29.66 1,100 8.33 110

08/03/2000 1120 29.79 1,100 8.31 110

08/03/2000 1225 30.03 1,100 8.59 114

08/03/2000 1320 30.23 1,100 8.91 118

08/03/2000 1425 30.50 1,100 8.02 108

08/03/2000 1533 30.76 1,100 8.47 115

08/03/2000 1630 30.79 1,100 8.34 113

08/03/2000 1727 30.69 1,100 8.45 114

08/03/2000 1831 30.64 1,100 8.42 113

08/03/2000 1928 30.57 1,100 8.18 110

08/03/2000 2046 30.46 1,100 8.00 108

08/03/2000 2200 30.37 1,100 7.97 107

08/03/2000 2332 30.16 1,100 7.77 103

08/04/2000 2400 29.90 1,100 7.59 101

08/04/2000 0120 30.07 1,100 7.74 103

08/04/2000 0235 29.96 1,100 7.24 96

08/04/2000 0330 29.85 1,100 7.22 96

08/04/2000 0430 29.79 1,100 7.24 96

08/04/2000 0532 29.72 1,100 7.15 94

08/04/2000 0620 29.61 1,100 7.74 102

080/4/2000 0730 29.57 1,100 7.84 103

08/04/2000 0830 29.63 1,100 8.24 109

Table 8. Diel study data on temperature, specific conductance, dissolved oxygen, and dissolved oxygen saturation, at selected 

water-quality stations in the Laguna Tortuguero, Vega Baja, Puerto Rico, August 3-4, 2000.—Continued

[Temperature in degrees Celsius; specific conductance in microsiemens per centimeter at 25°; dissolved oxygen in milligrams per liter; 

dissolved oxygen saturation in percent]
Water Quality of Laguna Tortuguero 17

Figure 3. Temperature and pH measurements, and dissolved oxygen, total nitrogen, and total phosphorus concentration at 

stations 1, 2, 4, and 5 in and near the Laguna Tortuguero, March 1999 to May 2000.
18 Water-Quality Evaluation of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000

Figure 3. Temperature and pH measurements, and dissolved oxygen, total nitrogen, and total phosphorus concentration at 

stations 1, 2, 4, and 5 in and near the Laguna Tortuguero, March 1999 to May 2000.—Continued
References Cited 19

References Cited

Cherry, G.S., 2001, Simulation of flow in the upper north coast 

limestone aquifer, Manatí-Vega Baja area, Puerto Rico: U.S. 

Geological Survey Water-Resources Investigations Report 

00-4266, 82 p.

Puerto Rico Environmental Quality Board, 2003, Junta de 

Calidad Ambiental de Puerto Rico, Reglamentos de 

estándares de calidad de agua de Puerto Rico, Versión 

Enmendada: Marzo 2003, 82 p.

Quiñones-Márquez, Ferdinand, and Fusté, L.A., 1977, 

Limnology of Laguna Tortuguero, Puerto Rico: U. S. 

Geological Survey Water-Resources Investigations Report 

77-122, 84 p.

U.S. Geological Survey, 1998, National field manual for the 

collection of water-quality data: Techniques of WaterResources Investigations, Book 9, Handbooks for WaterResources Investigations, 9 chps. 

Figure 3. Temperature and pH measurements, and dissolved oxygen, total nitrogen, and total phosphorus concentration at 

stations 1, 2, 4, and 5 in and near the Laguna Tortuguero, March 1999 to May 2000.—Continued
Soler-López and others—Water-Quality Reconnaissance of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000—OFR 2006-1049