U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5192

Prepared in cooperation with the Grand Portage Band of Chippewa Indians and the Science 

Museum of Minnesota

Water Quality (2000–08) and Historical Phosphorus 

Concentrations from Paleolimnological Studies of Swamp 

and Speckled Trout Lakes, Grand Portage Reservation, 

Northeastern Minnesota
Cover photo.  Swamp Lake, September 11, 2006. Photograph by Perry Jones, U.S. Geological Survey.
Water Quality (2000–08) and Historical 

Phosphorus Concentrations from 

Paleolimnological Studies of Swamp and 

Speckled Trout Lakes, Grand Portage 

Reservation, Northeastern Minnesota

By Victoria G. Christensen, Perry M. Jones, Mark B. Edlund, and Joy M. 

Ramstack

Prepared in cooperation with the Grand Portage Band of Chippewa Indians and 

the Science Museum of Minnesota

Scientific Investigations Report 2010–5192

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Christensen, V.G., Jones, P.M., Edlund, M.B., and Ramstack, J.M., 2010, Water quality (2000–08) and historical phosphorus concentrations from paleolimnological studies of Swamp and Speckled Trout Lakes, Grand Portage Reservation, northeastern Minnesota: U.S. Geological Survey Scientific Investigations Report 2010–5192, 53 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Description of Study Area ...................................................................................................................2

Methods...........................................................................................................................................................5

Water-Data Collection and Analysis by the Grand Portage Reservation

Environmental Department....................................................................................................5

Sample Collection and Analysis by U.S. Geological Survey..........................................................6

Sediment Core Collection and Analysis............................................................................................6

Water Quality of Swamp and Speckled Trout Lakes, 2000–08 ...............................................................7

Historical Phosphorus Concentrations from Paleolimnological Studies ...........................................10

Swamp Lake Sediments ....................................................................................................................10

Speckled Trout Lake Sediments .......................................................................................................12

Comparison of 2000–08 Total Phosphorus Concentrations to Inferred Historical 

Concentrations................................................................................................................................12

Summary .......................................................................................................................................................13

References Cited..........................................................................................................................................15

Figures

1. Map showing location of watershed boundaries of Swamp and Speckled

Trout Lakes, Grand Portage Reservation, northeastern Minnesota ....................................3

 2. Map showing watershed boundaries, lake-sediment coring sites, and waterquality sampling sites, Swamp and Speckled Trout Lakes, Grand Portage 

Reservation, northeastern Minnesota ......................................................................................4

3. Map showing bogs and swamps in the Swamp and Speckled Trout Lakes 

areas, Grand Portage Reservation, northeastern Minnesota...............................................5

4. Graphs showing Swamp Lake sediment core analyses, Grand Portage 

Reservation, Minnesota.............................................................................................................11

5. Graphs showing Speckled Trout Lake sediment core analyses, Grand Portage

Reservation, Minnesota.............................................................................................................13
iv

Tables

1. Method reference and reporting levels of nutrients, chlorophyll a, and

pheophyton analyzed by Era Laboratories and Northeast Technical Services in

Swamp and Speckled Trout Lakes near Grand Portage, Grand Portage

Reservation, northeastern Minnesota, 2000–08 ......................................................................7

2. Water-quality data collected by the Grand Portage Reservation, Environmental

Department for Swamp Lake near Grand Portage, Grand Portage Reservation,

northeastern Minnesota, 2000–08..............................................................................................8

3. Water-quality data collected by the Grand Portage Reservation, Environmental

Department for Speckled Trout Lake near Grand Portage, Grand Portage

Reservation, northeastern Minnesota, 2000–08 ......................................................................9

Appendix

1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand

Portage Reservation, northeastern Minnesota, 1997–2008.................................................20

2. Depth profiles of field properties for Speckled Trout Lake near Grand

Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.....................36

3. Water-quality data collected by the U.S. Geological Survey for Swamp and

Speckled Trout Lakes near Grand Portage, Grand Portage Reservation,

northeastern Minnesota, September 11, 2006 .......................................................................53
v

Conversion Factors

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

hectare (ha) 2.471 acre

square kilometer (km2) 0.3861 square mile (mi2)

square centimeter (cm2) 0.1550 square inch (in2)

Volume

liter (L) 0.2642 gallon (gal)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

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

 °F=(1.8×°C)+32

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25°C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L) or 

micrograms per liter (μg/L).
vi
Water Quality (2000–08) and Historical Phosphorus 

Concentrations from Paleolimnological Studies of Swamp 

and Speckled Trout Lakes, Grand Portage Reservation, 

Northeastern Minnesota

By Victoria G. Christensen1, Perry M. Jones1, Mark B. Edlund2, and Joy M. Ramstack2

1

 U.S. Geological Survey.

2

 Science Museum of Minnesota, St. Croix Watershed Research Station.

Abstract

A paleolimnological approach was taken to aid the Grand 

Portage Reservation, in northeastern Minnesota, in determining reference conditions for lakes on the reservation. The U.S. 

Geological Survey, in cooperation with the Grand Portage 

Band of Chippewa Indians and the Science Museum of Minnesota, conducted a study to describe water quality (2000–08) 

and historical total phosphorus concentrations (approximately 

1781–2006) for Swamp and Speckled Trout Lakes. Results 

from this study may be used as a guide in establishing nutrient criteria in these and other lakes on the Grand Portage 

Reservation. 

Historical phosphorus concentrations were inferred 

through paleolimnological reconstruction methods involving 

diatom analysis and lead-210 dating of lake-sediment cores. 

Historical diatom-inferred total phosphorus concentrations in 

Swamp Lake ranged from 0.017 to 0.025 milligrams per liter 

(mg/L) based on diatom assemblages in sediment samples 

dated 1781–2005. Historical diatom-inferred total phosphorus 

concentrations in Speckled Trout Lake ranged from 0.008 to 

0.014 mg/L based on diatom assemblages in sediment samples 

dated 1825–2006. In both lakes, historical changes in diatominferred total phosphorus concentrations did not exceed model 

error estimates, indicating that there has been minimal change 

in total phosphorus concentrations in the two lakes over about 

two centuries. 

Nutrient concentrations in monthly water samples collected May through October during 2000, 2002, 2004, 2006, 

and 2008 were compared to the diatom-inferred total phosphorus concentrations. Total phosphorus concentrations from 

water samples collected from Swamp Lake during 2000–08 

ranged from less than 0.002 to 0.160 mg/L (median=

0.023 mg/L) compared to diatom-inferred total phosphorus 

concentrations of 0.018 to 0.020 mg/L for 2002 to 2005. Total 

phosphorus concentrations in water samples collected from 

Speckled Trout Lake during 2000–08 were similar to those 

of Swamp Lake, ranging from less than 0.002 to 0.147 mg/L 

(median=0.012 mg/L), whereas the diatom-inferred total phosphorus concentrations were smaller, ranging from 0.009 to 

0.010 mg/L for 2003 to 2006. Differences in total phosphorus 

concentrations between the two lakes may be because of differences in watershed characteristics, particularly the number 

of wetlands in the two watersheds. Similarities between recent 

total phosphorus concentrations in water-quality samples and 

diatom-inferred total phosphorus indicate that diatom-inferred 

phosphorus reconstructions might be used to help establish 

reference conditions. Nutrient criteria for Grand Portage Reservation lakes may be established when a sampling program 

is designed to ensure representative phosphorus concentrations in water samples are comparable to diatom-inferred 

concentrations.

Introduction

The Grand Portage Reservation, in northeastern Minnesota, established water-quality standards in 2005 and subsequently has the responsibility to derive nutrient criteria for 

the reservation. The U.S. Environmental Protection Agency 

(USEPA) has established ecoregion-specific guidance for 

developing and defining local nutrient criteria (U.S. Environmental Protection Agency, 2000). The development of these 

nutrient criteria may be based on historical information of 

reference conditions, local nutrient-enrichment trends, and theoretical modeling of historical and current data. In accordance 

with the ecoregion-specific guidance, three general approaches 

are available for establishing reference conditions: (1) direct 

observation (data collection) of sites and estimation or inference of reference conditions, (2) model-based estimation or 

extrapolation of reference conditions for datasets of related 
2 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies

information, and (3) paleolimnological reconstruction of past 

conditions (U.S. Environmental Protection Agency, 2000).

Water-quality data collected by Grand Portage Reservation Environmental Department (GPR) and U.S. Geological 

Survey (USGS) during 1997–98 and 2003–04 indicated that 

nutrient concentrations in lakes on the reservation are quite 

low, commonly less than reporting levels (Winterstein, 2000; 

Jones, 2006). Most lakes on the reservation currently (2010) 

are not substantially affected by major sources of nutrients 

such as agricultural activities or wastewater discharge. Possible sources for nutrients in lakes are the bacterial and fungal 

decomposition of plant and animal protein (Christensen and 

Pope, 1997) and precipitation (Jones, 2006). 

GPR personnel have chosen to undertake direct observation and the paleolimnological approach to aid in establishing 

reference conditions for lakes on the reservation. A paleolimnological approach establishes the historical nutrient productivity of a lake through the characterization of nutrients and 

the fossil remains of organisms (diatoms and chrysophytes) 

in lake-sediment cores. Lead-210 dating of sediments is well 

documented (Robbins and Edgington, 1975; Pennington and 

others, 1976; Oldfield and Appleby, 1984) as is paleolimnological research based on diatoms preserved in lake sediments 

(Round, 1964; Bradbury, 1975). Many species of diatoms are 

sensitive to specific water conditions and are useful bioindicators. Statistical methods are used to estimate quantitative 

environmental properties or constituent concentrations (for 

example, total phosphorus) from diatom assemblages. This 

approach has been used to infer historical chemical conditions 

in many lakes in Minnesota and other States (Dixit and others, 

1992; Charles and Smol, 1994; Ramstack and others, 2003, 

2004; Heiskary and others, 2004). 

The paleolimnological approach was undertaken on two 

lake types that are common on the Grand Portage Reservation: 

a dystrophic (Swamp Lake) and an oligotrophic (Speckled 

Trout Lake, also called Trout Lake) lake. Dystrophic and oligotrophic are terms that refer to the trophic state of a lake, or 

the rate at which organic matter is produced or supplied to the 

lake. Dystrophic lakes receive large amounts of organic matter from sources in the lake’s watershed, have large amounts 

of dissolved humic matter, have low planktonic productivity 

(Wetzel, 2001, p. 274), and commonly are heavily stained. 

Oligotrophic lakes receive few nutrients from the watershed, 

contain small amounts of organic matter dominantly produced 

in the lake, and may be stained. The amounts of organic material and dissolved organic carbon play major roles in nutrient 

concentrations in lakes. For example, humic material can bind 

nutrients, and nutrients may affect the production of dissolved 

organic carbon. 

The U.S. Geological Survey, in cooperation with the 

Grand Portage Band of Chippewa Indians and the Science 

Museum of Minnesota, conducted a study to describe water 

quality (2000–08) and historical phosphorus concentrations 

(approximately 1781–2006) for Swamp and Speckled Trout 

Lakes. The purpose of the study was to aid the Grand Portage 

Reservation in establishing nutrient criteria and determining 

reference conditions for lakes on the reservation. 

Purpose and Scope

The purpose of this report is to describe water quality and 

nutrient conditions in two lakes on the Grand Portage Reservation—Swamp and Speckled Trout Lakes. This report summarizes recent (2000–08) water-quality data and compares the 

results to historical total phosphorus concentrations (approximately 1781–2006) inferred through paleolimnological reconstruction methods based on diatom analysis of lead-210 dated 

lake-sediment cores. 

Nutrient concentrations were analyzed in water samples 

collected during the ice-free season in 2000–08, including 

nitrite plus nitrate, total Kjeldahl nitrogen, total nitrogen, and 

total phosphorus. Other properties and constituents analyzed in 

water samples included field properties (specific conductance, 

pH, water temperature, and dissolved-oxygen concentrations), 

major ions, chlorophyll a, pheophyton, and dissolved organic 

carbon. The sediment cores were collected in 2006 and dated 

back to 1781 for Swamp Lake and 1825 for Speckled Trout 

Lake. Diatom analysis on these cores was used to infer historical total phosphorus concentrations in lake water. 

Description of Study Area 

The Grand Portage Reservation is located along the 

northwestern shore of Lake Superior in northern Cook County, 

Minnesota, at the boundary between Minnesota, United States, 

and Ontario, Canada (fig. 1). The Grand Portage Reservation covers 228 square kilometers (Goldstein, 2000) in the 

Northern Lakes and Forests Ecoregion (Omernik, 1987) and 

contains numerous hills, small valleys, streams, lakes, and 

wetlands within boreal and mixed hardwood forest communities (Jones, 2006). Most of the residential areas and tourist 

and historical attractions are located in the community of 

Grand Portage, along State Highway 61, and along State 

Highway 17 (Ruhl, 1995). Swamp and Speckled Trout Lakes 

are in the western part of the reservation, near the reservation 

boundary (fig. 1).

The reservation was almost entirely logged during the 

late 1800s and early 1900s (Winterstein, 2002). The northeast 

shore of Swamp Lake was logged in 1958 (Edlund and others, 

2007). Some areas of the reservation continue to be logged 

(Goldstein, 2000); however, most of the forest on the reservation is undisturbed second growth (Winterstein, 2002). 

Climate on the reservation is continental and locally 

affected by Lake Superior, with cold winters and warm summers (Jones, 2006). The mean temperature in August is about 

16.7 degrees Celsius (oC), whereas the mean temperature in 

January is about -12oC (High Plains Regional Climate Center, 

2009). Mean annual precipitation is about 72.5 centimeters 

(cm; High Plains Regional Climate Center, 2009).
Introduction 3

The topography and hydrology of the Grand Portage Reservation are affected by bedrock geology, which is described 

in detail in Jones (2006). Poorly sorted glacial till and lake 

clay of Pleistocene age cover much of the bedrock of the 

reservation. These glacial deposits are thin, generally less than 

19 meters (m) thick (Winterstein, 2002). The glacial till is part 

of ground and end moraines deposited during advances and 

subsequent wasting of ice sheets that moved southwesterly 

and westerly out of what is now Lake Superior (Wright, 1972). 

Post-glacial deposits (including alluvium, beach deposits, and 

peat) also overlie bedrock of the reservation (Jones, 2006). 

The land surface of the reservation rises from Lake Superior in the southeast to highlands in the center of the reservation and then declines near the Pigeon River in the north 

(fig. 1). Land-surface altitudes range from about 183 m at 

the shore of Lake Superior to about 553 m at Mount Sophie 

(Jones, 2006). Large changes in altitude occur along diabase 

dikes and gabbro intrusions that cross the reservation (Jones, 

2006).

In general, rivers and streams in the southeastern part of 

the reservation flow toward Lake Superior, whereas rivers and 

streams in the northeastern part flow toward the Pigeon River 

(fig. 1). The courses of rivers and streams are affected by the 

diabase dikes, with rivers and streams crossing the dikes along 

fault and fracture zones (Winterstein, 2002). Numerous lakes 

and wetlands are present, with the lakes lying mainly between 

the diabase dikes. 

Surface water is used for most public water supplies, 

whereas groundwater is used for domestic water supplies 

(Jones, 2006). Much of the groundwater on the reservation 

is rich in calcium, sodium, and chloride and too saline to be 

used for water supplies (Olcott and others, 1978; Winterstein, 

2002). Throughout the reservation, springs also are used by 

individuals whose wells are completed in (or sealed off in) 

deep fractured bedrock aquifers that contain unusable saline 

iron-rich water (Jones, 2006). Beaver activity is common, 

affecting the local hydrology. Swamp Lake has numerous 

Wauswaugon g

Bay

Grand Portage

Bay

Deronda Bay

in

Lake Superior

Grand Portage 

Indian Reservation

Ely Hovland

Cook County

Lake County

MINNESOTA

Pigeon

Red Rock

Reservation River

Creek

River

Hollow Rock

Creek

Poplar

Creek

Grand 

Portage Ck.

17

17

61

61

Grand

Portage

National Monument

MINNESOTA

MICHIGAN

ONTARIO,

CANADA

47°52'30"

48°

89°52'30" 45' 37'30" 89°30'

Reservation boundary

Loon

Lake Speckled

Trout

Lake

Center

Lake

Dutchman

Lake Cuffs

Lake

Teal

Lake

North

Lake

Taylor 

Lake

Chevans

Lake

Mt. Maude

Lake

Little

Lake

Turtle

Lake

Swede

Lake

Swamp

Lake

Grand

Portage

Mineral

Center

Hat Point Grand

Portage

Island

Raspberry Point

Lucille Island

uzie Island S

Base from Minnesota Department of Transportation, 1997, 1:24,000

U.S. Albers Equal Area projection

Standard parallels 29o30' and 45o30', central meridian -96o

Figure 1. Location of watershed boundaries of Swamp and Speckled Trout Lakes, Grand Portage Reservation, northeastern Minnesota.

Mount Sophie

1 2 3 MILES

0 1 2 3 KILOMETERS

0

Grand Portage Indian Reservation

Grand Portage National Monument

Watershed boundaries of Swamp and 

 Speckled Trout Lakes

EXPLANATION

Figure 1. Location of watershed boundaries of Swamp and Speckled Trout Lakes, Grand Portage Reservation, northeastern 

Minnesota.
4 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies

beaver lodges in small bays and inlets. Speckled Trout Lake 

has no in-lake lodges, but has a few lodges in the surrounding 

wetlands and inlets (Margaret Watkins, Grand Portage Band of 

Chippewa, written commun., 2009).

Swamp Lake is large relative to other Grand Portage 

lakes with an area of 144 hectares and a maximum depth of 

5.8 m (Lafrancois and others, 2009). Speckled Trout Lake has 

an area of 26 hectares and a maximum depth of 6.4 m (Lafrancois and others, 2009). The altitudes of the two lakes are high 

relative to other Grand Portage lakes at 476 m and 475 m, 

respectively (fig. 2). The watershed area is larger for Swamp 

Lake than Speckled Trout Lake (1,458 and 114 hectares, 

respectively; LaFrancois and others, 2009), and Swamp Lake 

is surrounded by several bogs and swamps (fig. 3).

A shoreline development value is the ratio of the length 

of the shoreline to the circumference of a circle of area equal 

to that of the lake (Wetzel, 2001). The shoreline development 

value provides an indication of potential littoral community, 

and higher values indicate less circular lakes and, therefore, 

higher biological productivity (Wetzel and Likens, 2000). 

The shoreline development value was higher in Swamp Lake 

(1.89) than in Speckled Trout Lake (1.44), indicating higher 

potential for nutrient production in Swamp Lake. 

Swamp and Speckled Trout Lakes are natural lakes that 

are stocked and fished (Goldstein, 2000). These lakes were 

monitored as part of the Grand Portage Reservation Monitoring Program for change in resource quality and to provide 

additional information about the fishery (Goldstein, 2000). 

Reservation River

Swamp

(altitude

 476 meters)

(altitude 475 meters)

Lake

Speckled 

Trout Lake

North

Lake

Swede

Lake

Turtle

Lake

Loon Lake

Unpaved Road

Indian Reservation Boundary

47°57'

58'

47°59'

89°53' 52' 51' 50' 49' 89°48'

1 MILE

0 1 KILOMETER

0

17

31 32 33 34

4 3 5 6

7

8 9 10

15

18 17 16

11 12

13 14

2 1

35 36

State Forest Boundary

Mtoun. Sophie Mount Sophie

EXPLANATION

 Watershed boundaries of Swamp and Speckled Trout Lakes

Lake-sediment coring site

U.S. Geological Survey/Grand Portage Reservation water-quality sampling site

Figure 2. Watershed boundaries, lake-sediment coring sites, and water-quality sampling sites, Swamp

and Speckled Trout Lakes, Grand Portage Reservation, northeastern Minnesota.

Base from U.S. Geological Survey and Minnesota Department of Natural Resources 

 digital data, 1:24,000, 2007, 

Universal Transverse Mercator projection

Zone 15 

Horizontal coordinate information is referenced to the 

 North American Datum of 1983

Vertical coordinate information is referenced to the 

 North American Vertical Datum of 1988

Figure 2. Watershed boundaries, lake-sediment coring sites, and water-quality sampling sites, Swamp and Speckled 

Trout Lakes, Grand Portage Reservation, northeastern Minnesota.
Methods 5

Stocking programs to maintain a successful sport fishery usually have minor effects on the quality of the water resource 

(Goldstein, 2000). However, game fish could alter food-web 

dynamics by preying on fish that forage on algae and zooplankton. Alternately, game fish could be affected by excessive nutrient loads that alter algal populations. 

Methods

Site selection for water-quality and sediment-core sampling was based on the site’s applicability to USEPA’s definition of reference conditions (U.S. Environmental Protection 

Agency, 2000), the availability of recent (1997 or later) waterquality (nutrient) data for the lake, minimal development 

around the lake, knowledge of the lake’s watershed ecology, 

and accessibility to the lake. Swamp Lake and Speckled Trout 

Lake were selected as reference lakes for water-quality and 

sediment-core sampling based on their different trophic states. 

The sampling locations (fig. 2) were identified by global positioning systems (GPS) to establish a common sampling location (at the deepest point) for each lake for all sampling trips.

Water-Data Collection and Analysis by the 

Grand Portage Reservation Environmental 

Department

Water sampling for field properties, major ions, and nutrients was conducted at Swamp and Speckled Trout Lakes by 

GPR personnel. Samples generally were collected on the same 

day in Swamp and Speckled Trout Lakes, with two exceptions, 

October 2000 and July 2008. 

Depth profiles were recorded (appendixes 1 and 2) 

for field properties (specific conductance, pH, temperature, 

and dissolved oxygen). Field properties are important to 

Reservation River

Swamp

Lake

Speckled Trout Lake

North

Lake

Swede

Lake

Turtle

Lake

Loon Lake

Unpaved Road

31 32 33 34

4 3 5 6

7

8 9 10

15

18 17 16

11 12

14 13

2 1

35 36

State Forest Boundary

Indian Reservation Boundary

47°57'

58' 

47°59'

89°53' 52' 51' 50' 49' 89°48'

1 MILE

0 1 KILOMETER

0

Mt. Sophie Mount Sophie

EXPLANATION

Bogs

Wooded swamp

Shrub swamp

Watershed boundaries of Swamp 

 and Speckled Trout Lakes 

Figure 3. Bogs and swamps in the Swamp and Speckled Trout Lakes areas, Grand Portage Reservation,

 northeastern Minnesota.

Base from Minnesota Department of Transportation base map 99, 1:24,000, 1999, and modified from

 Minnesota Department of Natural Resources, National Wetlands Inventory digital data, 1997

Universal Transverse Mercator projection

Zone 15

Horizontal coordinate information is referenced to the 

 North American Datum of 1983 

Figure 3. Bogs and swamps in the Swamp and Speckled Trout Lakes areas, Grand Portage Reservation, 

northeastern Minnesota.
6 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies

water-quality studies in lakes because they can be indicators 

of overall lake quality. Depth profiles of field properties were 

measured with a multiprobe sonde. 

Water samples were collected and field properties were 

measured by GPR personnel monthly during the ice-free 

season (May through October) in 2000, 2002, 2004, 2006, 

and 2008 according to the GPR Quality Assurance Project 

Plan (Margaret Watkins, Grand Portage Band of Chippewa, 

written commun., September 10, 2009). Briefly, lake samples 

were collected using a 2-m long integrated sampler, which 

was rinsed with distilled water and then lake water prior to 

sampling. The water in the integrated sampler was poured into 

a 2-liter (L) brown polyethylene container. The 2-L container 

was capped and gently shaken to mix the contents. The water 

from the 2-L container was used to fill a 1-L general chemistry

bottle and one 500-mL nutrients bottle. Pre-cleaned sample 

containers were provided by the laboratories performing the 

analyses. Each container was labeled, indicating location, 

date, and time of collection. All containers were transferred to 

an ice chest for temporary storage until they were shipped or 

delivered to the laboratories.

The samples were analyzed by Era Laboratories Inc., 

Duluth, Minn., or Northeast Technical Services, Virginia, 

Minn. The GPR alternated monthly samples between the two 

laboratories according to their Quality Assurance Project 

Plan (Margaret Watkins, Grand Portage Band of Chippewa, 

written commun., 2009). Samples were not filtered in the field 

and, therefore, samples were analyzed for total (unfiltered) 

concentrations of calcium, magnesium, chloride, sulfate, 

ammonia plus organic nitrogen, nitrite plus nitrate, nitrogen, 

phosphorus, chlorophyll a, and pheophyton. The laboratories 

filtered samples for dissolved organic carbon (Robert Magnuson, Era Laboratories, written commun., April 2, 2010, 

and Brandy Baker-Muhich, Northeast Technical Services, 

written commun., April 22, 2010). Analytes were determined 

with the following methods: major ions by EPA 200.7 (U.S. 

Environmental Protection Agency, 1994) and EPA 375.4 (U.S. 

Environmental Protection Agency, 1978); nutrients by EPA 

351.1, EPA 353.2, EPA 365.2, and EPA 365.4 (U.S. Environmental Protection Agency, 1978) and Lachat 20–107–04–1B 

(Era Standard Operating Procedure Number 9503, Robert 

Magnuson, Era Laboraties, written commun., April 13, 2010); 

and chlorophyll a and pheophyton by SM10200H (American 

Public Health Association and others, 1999). 

Era Laboratories and Northeast Technical Services 

were provided a copy of the GPR Quality Assurance Project 

Plan (Margaret Watkins, Grand Portage Reservation, written 

commun., 2009), which states that contract laboratories are 

required to adhere to the methodology, limits of detection, and 

quality-assurance objectives and criteria outlined in the plan. 

Era Laboratories and Northeast Technical Services were Minnesota Department of Health approved laboratories through 

the Minnesota Department of Health Laboratory Certification 

Program. The Minnesota Department of Health Certification 

Program rules and statutes may be found on the Minnesota 

Department of Health Web site at http://www.health.state.

mn.us/accreditation (accessed October, 2010). A laboratory 

receives certification for 2 years and certified laboratories are 

inspected every 3 years. A certified laboratory must successfully complete a proficiency test study demonstrating analytical proficiency for all its certified analyses annually. In addition, certified laboratories must use specific quality-control 

practices and maintain records according to the certification. 

Era Laboratories and Northeast Technical Services provided information on their expected precision and expected 

accuracy for the constituents of interest (table 1). Expected 

precision indicates acceptance criteria for laboratory duplicates. Expected accuracy refers to the acceptance criteria for 

laboratory spikes. A review of the quality-assurance results 

for total phosphorus provided by the laboratories indicates 

expected precision of 10–15 percent and an expected accuracy 

of 80–120 percent (table 1). 

Sample Collection and Analysis by U.S. 

Geological Survey

The USGS collected water samples and measured field 

properties from Swamp Lake and Speckled Trout Lake on 

September 11, 2006. Water samples were collected concurrent with samples collected by GPR personnel, using the 

same sampling methods. Field properties were measured 

with a multi-probe sonde according to methods presented in 

Wagner and others (2006). Alkalinity was measured within 

24 hours after sampling using the inflection point titration 

method (U.S. Geological Survey, variously dated). USGS 

water samples were processed according to methods described 

in the National Field Manual (U.S. Geological Survey, variously dated), which included the filtering of nutrient samples. 

Samples were sent to the National Water Quality Laboratory 

(NWQL) in Lakewood, Colo., and analyzed for dissolved concentrations of chloride, ammonia plus organic nitrogen, nitrite 

plus nitrate, total nitrogen, total phosphorus, and organic 

carbon using methods described by Fishman and Friedman 

(1989), Patton and Kryskalla (2003), Patton and Truitt (2000), 

Fishman (1993), and Brenton and Arnett (1993). Because 

USGS nutrient samples were filtered, analytical results are for 

dissolved concentrations and thus are not compared to diatominferred total phosphorus concentrations in this report. USGS 

analytical results for Swamp Lake (site 475702089511901) 

and Speckled Trout Lake (site 475704089504401) are 

available at http://waterdata.usgs.gov/mn/nwis/qw and in 

appendix 3.

Sediment Core Collection and Analysis

Lake sediments were cored at the two selected sites 

(fig. 2) on September 11, 2006, by the USGS and Science 

Museum of Minnesota, St. Croix Watershed Research Station personnel. Sediment cores were collected in 6.5-cm 

diameter polycarbonate tubes with a hand-operated piston 

sampler pushed into the sediments with rigid coring rods. The 
Water Quality of Swamp and Speckled Trout Lakes, 2000–08 7

recovered cores were approximately 1 m in length. The cores 

were collected at water depths of 1.4 and 4.3 m for Swamp 

and Speckled Trout Lakes, respectively. The two lakesediment cores were collected, labeled, described, logged, 

and sampled in the field by Science Museum of Minnesota, 

St. Croix Watershed Research Station personnel. Descriptions 

included color, texture, odor, and presence of biota and organic 

detritus or other visible characteristics. 

At the St. Croix Watershed Research Station, samples 

were stored at 4oC and subsampled at intervals of 1.0 to 

2.0 cm (Edlund and others, 2007, 2009). Selected subsamples 

were analyzed for lead-210 age dates, loss-on-ignition (LOI), 

and subfossil diatom community assemblage as described by 

Edlund and others (2007, 2009). Unused core portions were 

freeze dried and stored for future reference. Dates and sedimentation rates were determined according to the constant rate 

of supply model (Appleby and Oldfield, 1978).

Core subsamples were analyzed for diatom microfossils 

at 15 depths spanning the length of the cores from Swamp 

Lake (Edlund and others, 2007) and Speckled Trout Lake 

(Edlund and others, 2009); diatoms were identified to the 

lowest taxonomic level. Multivariate statistical analyses 

(Detrended Correspondence Analysis and Principal Components Analysis) were performed on the diatom data to interpret 

variations in the subfossil diatom assemblages (Edlund and 

others, 2007, 2009). 

A transfer function, based on weighted-averaging regression and calibration on diatom assemblages and total phosphorus concentrations, was used to estimate historical diatominferred total-phosphorus concentrations. The transfer function 

used for Swamp and Speckled Trout Lakes was derived 

by comparing modern diatom species assemblages to total 

phosphorus concentrations in 89 reference lakes (Edlund and 

Ramstack, 2006; Edlund and others, 2007, 2009). These 89 

reference lakes spanned major Minnesota ecoregions (Edlund 

and Ramstack, 2006) that differed in their history of settlement 

and land use, and in surficial geology, climate, and vegetation 

(Ramstack and others, 2003). A similar transfer function, using 

55 reference lakes, is described in detail in Ramstack and others (2003). Relations between total phosphorus concentrations 

in the 89 reference lakes and diatom assemblages were evaluated using canonical correspondence analysis. In the canonical 

correspondence analysis total phosphorus concentrations had a 

statistically significant (p-value less than (<) 0.005) influence 

on diatom distribution (Ramstack and others, 2003). 

Water Quality of Swamp and Speckled 

Trout Lakes, 2000–08

Median values for field properties were smaller in Swamp 

Lake (table 2) than in Speckled Trout Lake (table 3). Median 

specific conductance values measured in Swamp and Speckled 

Trout Lakes were 36.9 and 48.0 microsiemens per centimeter at 25o

C (μS/cm), respectively, indicating that dissolved 

ion concentrations in waters of both lakes are small. Median 

values for pH and alkalinity were lower in water samples from 

Swamp Lake than in water samples from Speckled Trout Lake. 

The pH at Swamp Lake likely is lower because bogs and other 

wetlands, which typically have lower pH (Mitsch and Gosselink, 1993), are attached to the shoreline (fig. 3). This also is 

supported by higher dissolved organic carbon in Swamp Lake 

(table 2) than in Speckled Trout Lake (table 3)

The pH and alkalinity values of waters in both lakes indicate that general water-quality conditions likely are not threatening fish or acid-intolerant forms of aquatic life. Alkalinity is 

Table 1. Method reference and reporting levels of nutrients, chlorophyll a, and pheophyton analyzed by Era Laboratories and 

Northeast Technical Services in Swamp and Speckled Trout Lakes near Grand Portage, Grand Portage Reservation, northeastern 

Minnesota, 2000–08. Site location shown in figure 2. 

[mg/L, milligrams per liter; μg/L, micrograms per liter; N, nitrogen; P, phosphorus; expected precision, acceptance criteria for laboratory duplicate analyses; 

expected accuracy, the acceptance criteria for laboratory spikes; --, no data]

Era Laboratories Northeast Technical Services

Method 

reference

Reporting 

level

Expected 

precision 

(percent)

Expected 

accuracy 

(percent)

Method Reporting 

level

Expected 

precision1

(percent)

Expected 

accuracy2

(percent)

Nitrite plus nitrate (mg/L as N) -- -- -- -- EPA 353.2 0.1 15 85–115

Total nitrogen (mg/L as N) Lachat 20-

107-04- 0.1 10 80–120 EPA 351.2/ 353.2 .1 15 85–116

Total Kjeldahl nitrogen (mg/L as N) -- -- -- -- EPA 351.2 .5 15 85–117

Total phosphorus (mg/L as P) EPA 365.2 0.002 10 80–120 EPA 365.1 

Rev. 2.0 .004 15 85–118

Chlorophyll a (μg/L) SM10200H 1 25 -- SM10200H 1 15 85–119

Pheophyton (μg/L) SM10200H 1 25 -- -- -- -- --

1

 Beginning in mid-2007, the expected precision for nutrients analyzed by Northeast Technical Services changed to 10 percent.

2

 Beginning in mid-2007, the expected accuracy for nutrients analyzed by Northeast Technical Services changed to 90–100 percent.
8 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Table 2. Water-quality data collected by the Grand Portage Reservation Environmental Department for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 2000–08. [μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; ERA, Era Laboratories; NTS, Northeast Technical Services; --, no data; <, less than] Date and time Analyzing laboratory Specific conductance (μS/cm) pH (standard units) Alkalinity (mg/L) Hardness (mg/L) Calcium (mg/L) Magnesium (mg/L) Chloride (mg/L) Sulfate (mg/L)1 Nitrite plus nitrate (mg/L)1 Total nitrogen (mg/L) Total Kjeldahl nitrogen (mg/L)1 Total phosphorus (mg/L)1 Chlorophyll a (μg/L) Pheophyton (μg/L)1 Dissolved organic carbon (mg/L) 5/1/00 11:00 ERA 37.0 7.20 8.0 14.0 3.0 1.49 0.80 3.0 -- 0.50 -- 0.032 4.0 <1 -- 6/6/00 10:10 NTS 45.0 7.20 12.0 16.0 -- -- .70 <1 <0.1 .80 0.80 .020 1.0 -- -- 7/10/00 10:30 ERA 37.0 7.10 12.0 22.0 -- -- .80 4.0 -- .80 -- .024 7.0 <1 -- 8/14/00 12:00 NTS 36.7 7.88 8.0 20.0 -- -- <.20 <1 <.1 1.40 1.40 <.002 5.0 -- -- 9/11/00 11:00 ERA 38.0 8.00 20.0 24.0 -- -- .80 3.0 -- .80 -- .026 8.0 <1 -- 10/1/00 10:30 NTS 36.4 -- <1 38.0 -- -- .80 <1 <.1 .95 .95 .020 20.0 -- -- 5/13/02 10:00 ERA 28.0 7.00 9.0 14.0 3.8 1.18 .80 4.0 -- .60 -- .024 4.0 <1 -- 6/17/02 10:30 NTS 36.0 6.81 10.0 20.0 5.4 -- .50 <1 <.1 .30 .30 .002 <1 -- -- 7/17/02 10:00 ERA 36.0 6.80 15.0 20.0 5.1 -- .50 5.0 -- .80 -- .031 8.0 <1 -- 8/13/02 14:35 NTS 43.0 -- 16.0 42.0 6.9 -- 1.30 <1 .200 1.00 .80 .040 1.0 -- -- 9/10/02 10:45 ERA 42.0 7.20 14.0 19.0 4.7 -- .50 3.0 -- .60 -- .029 10.0 <1 -- 10/2/02 11:30 NTS 34.6 6.60 18.0 38.0 5.7 -- .80 <1 <.1 .80 .80 .160 2.0 -- -- 5/24/04 10:20 NTS 28.1 6.60 10.0 15.0 3.5 -- .90 6.3 <.1 1.60 1.60 .020 2.0 -- -- 6/7/04 10:20 ERA 31.0 6.30 8.0 15.0 4.0 -- .80 6.0 -- .50 -- .022 3.0 1 -- 7/12/04 9:50 NTS 41.1 6.90 13.1 20.0 4.8 -- .25 .5 <.1 1.60 1.60 .005 10.0 -- -- 8/2/04 15:00 ERA 54.0 8.60 20.0 20.0 5.2 1.80 .40 4.0 -- .70 -- .010 5.0 2.0 -- 9/7/04 10:10 NTS 49.7 6.90 15.5 22.0 5.5 -- .25 .5 <.1 .75 .75 .070 8.0 -- -- 10/6/04 14:15 ERA 38.0 7.20 11.0 18.0 4.4 -- .80 4.0 -- 1.00 -- .038 1.0 <1 -- 5/15/06 10:05 NTS 38.5 8.10 17.7 13.0 3.3 1.10 <.5 2.1 <.1 .83 .83 <.01 1.0 -- 21.1 6/7/06 10:00 ERA 29.0 6.80 8.0 15.0 3.8 -- .70 5.0 <.01 1.00 1.00 .020 6.0 <1 20.8 7/10/06 9:52 NTS 32.0 7.70 14.3 18.0 4.5 1.73 <1 2.9 <.1 .77 .77 .030 <1 -- 20.3 8/15/06 10:30 ERA 38.0 6.90 12.0 19.0 4.4 2.00 .80 3.0 <.01 1.10 1.10 .038 11.0 <1 19.2 9/11/06 10:40 NTS 36.2 7.00 14.6 21.0 5.0 2.25 <.5 2.6 <.1 1.84 1.84 .040 7.0 -- 20.4 10/3/06 10:10 ERA 41.0 7.00 13.0 20.0 4.5 -- .70 4.0 .690 2.00 1.30 .030 8.0 <1 20.4 5/12/08 10:40 NTS 16.0 6.40 <1 11.7 3.1 .96 <.5 2.3 <.1 .96 .96 .010 1.0 -- 12.7 6/2/08 9:15 ERA 28.0 6.40 8.0 13.0 3.3 -- 1.10 3.4 <.01 .70 .70 .020 2.0 <1 13.3

7/15/08 10:10 NTS 21.3 7.00 <1 18.4 4.9 1.52 <.5 2.4 <.1 .98 .98 .016 6.0 -- 20.58/11/08 11:34 ERA 41.0 6.60 14.0 21.5 5.6 1.80 1.00 2.5 <.02 .90 .90 .021 7.0 <1 22.49/8/08 9:50 NTS 30.3 7.20 17.4 22.3 6.0 1.78 <.5 2.9 <.1 4.24 4.24 .007 4.0 -- 19.110/2/08 10:00 ERA 42.0 7.00 16.0 21.7 5.8 -- .30 2.4 <.02 1.00 1.00 .021 7.0 <1 22.0Number of samples 30 28 30 30 25 11 30 30 21 30 21 30 30 15 12Median concentration 36.9 7.00 12.5 20.0 4.7 1.73 .80 2.9 <.1 .87 .96 .023 5.5 <1 20.4

1Differences in reporting levels and types of analyses occur because two laboratories, Era Laboratories in Duluth, Minn. and Northeast Technical Services in Virginia, Minn., were used for the analyses,

generally alternating monthly (Margaret Watkins, Grand Portage Band of Chippewa, written commun., 2009).
Water Quality of Swamp and Speckled Trout Lakes, 2000–08 

9

Table 3. Water-quality data collected by the Grand Portage Reservation Environmental Department for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 2000–08.[μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; ERA, Era Laboratories; NTS, Northeast Technical Services; --, no data; <, less than]

Date and time Analyzing laboratory Specific conductance (μS/cm) pH (standard units) Alkalinity (mg/L) Hardness (mg/L) Calcium (mg/L) Magnesium (mg/L) Chloride (mg/L)1 Sulfate (mg/L)1 Nitrite plus nitrate (mg/L)1 Total nitrogen (mg/L) Total Kjeldahl nitrogen (mg/L)1 Total phosphorus (mg/L)1 Chlorophyll a (μg/L)1 Pheophyton (μg/L)1 Dissolved organic carbon (mg/L)

5/1/00 11:40 ERA 48.0 7.20 12.0 14.0 2.7 1.69 0.4 3.0 -- 0.40 -- 0.011 3.0 <1 --6/6/00 11:20 NTS 51.0 7.66 18.0 22.0 -- -- <.2 <1 <0.1 .50 0.53 .010 39.0 -- --7/10/00 11:20 ERA 49.0 7.40 19.0 22.0 -- -- .4 4.0 -- .40 -- .012 3.0 <1 --8/14/00 12:00 NTS 48.0 7.70 16.0 20.0 -- -- <.2 <1 <.1 .88 .88 <.002 2.0 -- --9/11/00 11:40 ERA 41.0 7.80 21.0 30.0 -- -- .4 2.0 -- .50 -- .012 6.0 <1 --10/3/00 10:30 NTS 43.9 6.46 24.0 38.0 -- -- <.2 3.0 <.1 .61 .61 .010 5.0 -- --5/13/02 11:00 ERA 40.0 7.10 17.0 20.0 5.2 1.82 .4 2.0 -- 2.90 -- .147 1.0 <1 --6/17/02 11:30 NTS 45.0 6.84 18.0 22.0 5.9 -- .5 <1 <.1 .20 .20 <.002 <1 -- --7/17/02 10:30 ERA 46.0 7.00 21.0 21.0 5.3 -- .4 2.0 -- .30 -- .011 4.0 <1 --8/13/02 15:15 NTS 49.0 -- 22.0 44.0 7.7 -- 1.3 2.5 .50 1.20 .70 <.002 <1 -- --9/10/02 11:25 ERA 52.0 7.30 21.0 22.0 5.6 -- .4 3.0 -- 1.00 -- .014 8.0 <1 --10/2/02 12:20 NTS 44.6 6.40 20.0 22.0 6.3 -- .5 <1 <.1 .60 .60 .090 2.0 -- --5/24/04 11:40 NTS 50.4 7.10 20.0 22.0 5.2 -- .3 <1 <.1 1.60 1.60 .005 2.0 -- --6/7/04 11:25 ERA 52.0 6.90 21.0 19.0 4.8 -- .4 5.0 1.20 -- .013 2.0 <1 --7/12/04 10:40 NTS 58.0 7.90 20.8 21.0 5.0 -- .3 <1 <.1 1.70 1.70 .005 <1 -- --8/2/04 16:05 ERA 38.0 6.90 12.0 19.0 4.5 1.80 .9 5.0 1.00 -- .030 3.0 <1 --9/7/04 11:00 NTS 64.0 7.70 23.3 19.0 4.4 -- .3 <1 <.1 .94 .94 .090 7.0 -- --10/6/04 15:10 ERA 51.0 7.60 21.0 21.0 5.5 -- .3 3.0 .70 -- .017 2.0 <1 --5/15/06 10:45 NTS 52.7 8.40 27.1 22.0 5.6 2.00 <.6 3.2 <.1 1.00 1.00 .020 1.0 -- 12.56/7/06 11:25 ERA 47.0 7.50 17.0 20.0 5.2 -- .3 3.0 .10 .30 .20 .010 2.0 <1 7.47/10/06 10:50 NTS 48.0 7.70 26.9 23.0 5.9 1.96 <1 3.8 <.1 <.1 <.5 <.01 <1 -- 7.88/15/06 11:30 ERA 51.0 7.40 20.0 23.0 5.8 2.00 .4 4.0 <.02 .40 .40 .009 2.0 <1 7.39/11/06 11:50 NTS 45.2 7.40 32.0 23.0 5.8 2.08 <.6 3.1 <.1 1.14 1.14 .030 2.0 -- 7.710/3/06 11:10 ERA 52.0 7.40 21.0 22.0 5.3 -- .4 4.0 .03 .70 .70 .009 1.0 <1 8.25/12/08 11:35 NTS 32.0 7.10 17.7 20.2 5.3 1.69 <.6 2.2 <.1 1.24 1.24 .006 3.0 -- 6.26/2/08 11:48 ERA 46.0 7.20 18.0 19.0 4.9 -- .3 2.6 .04 .54 .50 .011 <1 <1 5.77/14/08 11:00 NTS 31.2 7.10 17.4 21.6 5.5 1.94 <.6 2.2 <.1 .80 .80 .007 2.0 -- 6.68/11/08 0:58 ERA 75.0 6.40 28.0 24.4 6.6 1.95 .5 4.8 <.02 1.40 1.40 .021 5.0 <1 8.99/8/08 11:00 NTS 29.8 7.30 18.2 19.8 5.1 1.73 <.6 2.3 <.1 .76 .76 .007 3.0 -- 7.010/2/08 11:00 ERA 45.0 6.90 19.0 19.7 5.0 -- .3 2.2 <.02 .60 .60 .015 <1 <1 8.1Number of samples 30 29 30 30 25 11 30 30 21 30 21 30 30 15 12Median concentration 48.0 7.30 20.0 21.8 5.3 1.94 .4 2.6 <.1 .76 .73 .012 2 <1 7.6

1Differences in reporting levels and types of analyses occur because two laboratories, Era Laboratories in Duluth, Minn. and Northeast Technical Services in Virginia, Minn., were used for the analyses, 

generally alternating monthly (Margaret Watkins, Grand Portage Band of Chippewa, written commun., 2009).
10 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies

defined as the capacity of solutes in the water to react with and 

neutralize acid. Lakes with a low alkalinity have a low buffering capacity and, thus, could have low (acidic) pH values. 

Lethal effects for aquatic life begin to appear near a pH of 4.5 

(Wetzel, 2001, p. 191). The pH levels in low-alkalinity lakes 

can decrease because of acid from rainfall. Although alkalinity 

concentrations are low in both lakes, the pH levels are close 

to neutral (7.0) indicating that recent (2000–08) conditions do 

not pose a substantial threat for fish or acid-intolerant forms of 

aquatic life. 

Median total calcium and magnesium concentrations 

were smaller in Swamp Lake than in Speckled Trout Lake, 

whereas total chloride concentrations were larger in Swamp 

Lake (tables 2 and 3). Cations (calcium and magnesium) and 

anions (chloride and sulfate) occur naturally in all surface 

water at varying concentrations and may concentrate in water 

as a result of natural dissolution of minerals from bedrock, 

glacial deposits, and soils. The natural variability in concentration depends on chemical characteristics of drainage-basin 

soils and in some situations the minerals in deeper geologic 

strata (Christensen and Pope, 1997). Total chloride and 

sulfate concentrations are small in Swamp and Speckled Trout 

Lakes compared with concentrations in some saline groundwater on the reservation, which have exceeded the USEPA 

Secondary Maximum Contaminant Level of 250 mg/L 

(Winterstein, 2002). 

Median total nitrogen concentrations were larger in 

Swamp Lake than in Speckled Trout Lake, perhaps indicating 

a larger source of organic matter in Swamp Lake or its watershed. However, the difference in total nitrogen concentrations 

between the lakes was not significant using a Wilcox signedrank test (Helsel and Hirsch, 1992) with a significance value 

(α) of 0.05 (p-value=0.0597). 

Total phosphorus concentrations also are small in 

both lakes with medians of 0.023 mg/L in Swamp Lake and 

0.012 mg/L in Speckled Trout Lake (tables 2 and 3). The difference was statistically significant (p-value=0.0043). Nitrogen to phosphorus ratios based on median concentrations were 

38:1 in Swamp Lake and 63:1 in Speckled Trout Lake. Nitrogen to phosphorus ratios greater than 23:1 indicate phosphorus 

limitation (Wetzel, 2001).

Chlorophyll-a concentrations were larger in Swamp Lake 

than in Speckled Trout Lake (tables 2 and 3). In other northern 

Minnesota lakes, chlorophyll a tends to vary seasonally with 

peak concentrations normally occurring in late summer (Christensen and others, 2004). However, seasonal patterns generally 

were not evident in the Swamp Lake or Speckled Trout 

Lake water samples. For both Swamp and Speckled Trout 

Lakes, the peak concentrations occurred in 2000 and were 20 

and 39 micrograms per liter (mg/L), respectively. This possibly indicates a larger algal biomass during 2000 than in later 

years. Lower-than-normal precipitation rates in September and 

October may have affected the peak chlorophyll-a concentrations. The peak concentration in Swamp Lake occurred in 

October, and total precipitation for September and October 

2000 was about 7 cm below normal (Minnesota Climatology 

Working Group, 2009). The peak concentration at Speckled 

Trout Lake occurred in June, and total precipitation for June 

was about 10 cm, near the average for the period of record 

(Minnesota Climatology Working Group, 2009). Although 

median pheophyton concentrations were the same in both 

lakes (< 1 μg/L), one sample from Swamp Lake, had a 

pheophyton concentration of 2.0 μg/L.

Dissolved organic carbon concentrations were larger in 

Swamp Lake than in Speckled Trout Lake (tables 3 and 4) 

with median concentrations of 20.4 and 7.6 mg/L, respectively. Dissolved organic carbon is an approximation of the 

total concentration of dissolved organic material (Hem, 1992). 

Differences in concentrations of total phosphorus, chlorophyll a, and dissolved organic carbon between the two lakes 

may be because of differences in watershed characteristics, 

particularly the number of wetlands in the two watersheds 

(fig. 3). The attached bogs and upgradient swamps in the 

Swamp Lake watershed are a possible nutrient and organic 

carbon source, leading to enhanced algal growth and thus 

higher chlorophyll-a concentrations in Swamp Lake than 

Speckled Trout Lake. Water quality in Swamp and Speckled 

Trout Lakes were compared to concentrations in other reservation lakes (LaFrancois and others, 2009). The median total 

phosphorus concentration for 15 lakes on the Grand Portage 

Reservation, including Swamp and Speckled Trout Lakes 

(0.024 mg/L; LaFrancois and others, 2009) was similar to the 

median concentration for Swamp Lake (0.023 mg/L). Swamp 

Lake also had similar total nitrogen and larger dissolved 

organic carbon concentrations, whereas Speckled Trout Lake 

had smaller total nitrogen, total phosphorus, and dissolved 

organic carbon concentrations than most other reservation 

lakes. 

Historical Phosphorus Concentrations 

from Paleolimnological Studies

Lake-sediment cores from Swamp and Speckled Trout 

Lakes were collected in 2006 and dated back to 1781 for 

Swamp Lake and 1825 for Speckled Trout Lake. Historical 

phosphorus concentrations were inferred through paleolimnological reconstruction methods involving diatom analysis and 

lead-210 dating of lake-sediment cores.

Swamp Lake Sediments

Dry-weight percentages of organic matter, calcium 

carbonate, and inorganic matter were determined by LOI 

for Swamp Lake sediments (fig. 4A). Results indicated that 

sediment from Swamp Lake historically has been dominated 

by the inorganic component with a shift to a higher organic 

component after about 1900.

Lead-210 dating decreased downward to a depth of 

16 cm (Edlund and others, 2007). An age-depth model 
Historical Phosphorus Concentrations from Paleolimnological Studies 11

indicated that sediments below 16 cm were deposited prior 

to 1875 (fig. 4A). The large shifts in the percentages of organic 

and inorganic components (fig. 4A) and in the sediment 

accumulation rate (fig. 4B) at core depths of 15 to 16 cm 

(1880s) likely were because of logging during early European 

settlement (1880–1920) of the area (Edlund and others, 2007). 

A large increase in sediment accumulation rate after 1960 

likely was a result of logging along the northeastern shore of 

Swamp Lake in 1958 (Edlund and others, 2007). 

The diatom flora of Swamp Lake is very diverse with 

more than 280 diatom taxa found in the core samples. These 

diatoms included many rare or uncommon species and 

several unknown taxa (Edlund and others, 2007). Detrended 

correspondence and principal components analyses were 

applied to the diatom data to visualize relations among diatom 

communities with depth. Stratigraphic zones of the diatom 

assemblages were identified by the principal components 

analysis, but only minor changes were seen in the historical 

Swamp Lake diatom communities.

The diatom assemblages were used to reconstruct historical epilimnetic total phosphorus concentrations in Swamp 

Lake (fig. 4C). Diatom-inferred total phosphorus concentrations ranged from 17 to 25 μg/L (0.017 to 0.025 mg/L) in 

sediments dated 1781–2005. The transfer function reconstructs 

logarithmic total phosphorus concentrations with model error 

estimates (fig. 4D). Results of the transfer function were backtransformed to total phosphorus concentrations in milligrams 

per liter (fig. 4C). Differences among these values were not 

greater than the root mean square error of prediction for the 

transfer functions. In other words, there were no statistically 

1760

1780

1800

1820

1840

1860

1880

1900

1920

1940

1960

1980

2000

2020

0 0.005 0.010 0.015 0.020 0.025 0.030

C

TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER

LEAD-210 AGE, IN YEARS

LEAD-210 AGE, IN YEARS

0

20

40

60

80

100

0 10 20 30 40 50 60

DRY-WEIGHT PERCENTAGE

DEPTH, IN CENTIMETERS 

3

5

11

16

20

DEPTH, IN CENTIMETERS

A

Calcium carbonate 0rganics

Inorganics

YEAR,DECIMAL

2001.7

1994.5

1960.2

1875.5

1781.2

Figure 4. Swamp Lake sediment core analyses, Grand Portage Reservation, Minnesota. A, dry weight percentage of calcium 

carbonate, organic matter, and inorganic matter; B, sediment accumulation rates; and C, diatom-inferred total phosphorus 

concentrations; D, model error estimates (from Edlund and others, 2007).

1760

1780

1800

1820

1840

1860

1880

1900

1920

1940

1960

1980

2000

2020

0 0.0005 0.0010 0.0015 0.0020

LOGARITHM OF TOTAL PHOSPHORUS CONCENTRATION, 

IN MILLIGRAMS PER LITER

D

Median 2000–08

total phosphorus

concentration in

lake water

1760

1780

1800

1820

1840

1860

1880

1900

1920

1940

1960

1980

2000

2020

0 0.01 0.02 0.03

B

SEDIMENT ACCUMULATION RATE,

IN GRAMS PER SQUARE CENTIMETER PER YEAR

Figure 4. Swamp Lake sediment core analyses, Grand Portage Reservation, Minnesota. A, dry-weight percentage of calcium 

carbonate, organic matter, and inorganic matter; B, sediment accumulation rates; C, diatom-inferred total phosphorus concentrations; 

and D, model error estimates (from Edlund and others, 2007).
12 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies

significant changes given the uncertainties associated with 

the transfer functions, inferring that no major changes in total 

phosphorus concentrations occurred during the past 200 years. 

Comparison of the Swamp Lake diatom communities with diatom communities of the 89 Minnesota lakes indicated that any 

shift in the Swamp Lake communities could not be correlated 

to a specific environmental stressor (Edlund and others, 2007). 

Speckled Trout Lake Sediments 

LOI analysis on the Speckled Trout Lake core indicated 

that sediment from Speckled Trout Lake historically has been 

dominated by the inorganic component with the organic component increasing between 1850 and 1900 (fig. 5A). This shift 

could represent the effects of the initial logging in the watershed around 1900–1910 (Edlund and others, 2009). Disturbance of soils during logging could lead to enhanced erosion 

and an increase in the rate of deposition. Slash (the unused 

logs and debris left after land has been logged) may contribute 

to increased organic content relative to inorganic material. 

Similar increases were present in dated cores from other lakes 

along Minnesota’s North Shore region (Edlund and others, 

2009). The percentage of inorganic sediments decreased to 

39 percent at the top of the core (above a depth of 28 cm).

Minor increases in sediment accumulation rates in 

the Speckled Trout Lake core occurred between 1840 and 

1880. These increases may have resulted from fires following droughts in northeastern Minnesota. Heinselman (1973) 

identified five periods of fire in the 1800s for the Boundary 

Waters Canoe Area, Minnesota: 1801, 1824, 1863–64, 1875, 

and 1894. Most of these fire periods followed prolonged 

droughts of subcontinental extent, including the 1864 drought 

(Heinselman, 1973). These minor increases are followed by an 

increase in sediment accumulation rate from about 0.01 gram 

per square centimeter per year (g/cm2/yr) in 1900 to about 

0.03 g/cm2/yr in 2005 (fig. 5B). Overall, sedimentation rates 

were slightly larger for the Speckled Trout Lake core than for 

the Swamp Lake core, possibly because of the steeper slope 

in the land surface surrounding Speckled Trout Lake or basin 

morphometry that produces more focused sedimentation.

Sediments from the Speckled Trout Lake core were 

analyzed for diatom microfossils at 15 discrete depths in the 

core, spanning the time before European settlement (which 

occurred about 1870) to 2006, when the core was collected. 

Similar to the Swamp Lake core, the diatom flora of the 

Speckled Trout Lake core was very diverse and dominated by 

softwater diatoms. More than 215 diatom taxa were found in 

the core samples including many rare or uncommon species 

and several unknown taxa (Edlund and others, 2009). Similar 

to the Swamp Lake core, only minor changes in the diatom 

communities occurred through the length of the cores. As a 

reflection of these minor changes, historical diatom-inferred 

total phosphorus concentrations indicated that there were no 

major changes in total phosphorus concentrations since the 

early 1860s. Diatom-inferred total phosphorus concentrations 

ranged from 8 to 14 μg/L (0.008 to 0.014 mg/L) in sediments 

dated between 1825 and 2006 (fig. 5C). Differences among 

these values were not greater than the root mean square error 

of prediction for the transfer function and infer that no major 

changes in total phosphorus concentrations have occurred in 

the past 200 years. 

Comparison of 2000–08 Total 

Phosphorus Concentrations to Inferred 

Historical Concentrations

Total phosphorus concentrations from water samples 

collected from Swamp Lake during 2000–08 by GPR personnel ranged from less than 0.002 to 0.16 mg/L (median=

0.023 mg/L, table 2) compared to diatom-inferred total 

phosphorus concentrations of 0.017 to 0.025 mg/L based on 

sediments dated 1781–2005. Sediments deposited concurrently with monitoring (sediments dated from 2002 to 2005) 

produced diatom-inferred total phosphorus concentrations of 

0.018 to 0.020 mg/L. 

Total phosphorus concentrations from water samples collected from Speckled Trout Lake during 2000–08 were similar 

to those of Swamp Lake, ranging from less than 0.002 to 

0.147 mg/L (median= 0.012 mg/L, table 3). Diatom-inferred 

total phosphorus concentrations in Speckled Trout Lake 

ranged from 0.008 to 0.014 mg/L based on sediments dated 

1825–2006, which are somewhat smaller than those inferred 

for Swamp Lake. Diatom-inferred total phosphorus concentrations based on sediments deposited during the monitoring 

period ranged from 0.009 to 0.010 mg/L (sediments dated 

from 2003 to 2006). The diatom-inferred total phosphorus values for Swamp and Speckled Trout Lakes were similar to the 

diatom-inferred total phosphorus concentrations determined 

for other lakes in the Northern Lakes and Forest ecoregion 

in Cook and Lake Counties (range of 0.011 to 0.027 mg/L; 

Ramstack and others, 2003).

The narrow range of diatom-inferred values (from 2002 

to 2005 for Swamp Lake and 2003 to 2006 for Speckled Trout 

Lake) represent temporally integrated samples (1 to 3 years). 

As expected with monthly ice-free seasonal sampling in 

Swamp and Speckled Trout Lakes, water-sample total phosphorus concentrations have a much greater range of values 

than diatom-inferred values. Although the median water-sample total phosphorus concentrations (0.023 and 0.012 mg/L) 

compare favorably with the diatom-inferred concentrations 

(figs. 4C and 5C), a limitation of this study was the absence 

of field replicate samples analyzed for total phosphorus 

concentrations. The small differences between 2000–08 

total phosphorus concentrations and diatom-inferred total 

phosphorus concentrations for the Swamp and Speckled 

Trout Lakes may be because of several factors, including 

(1) the lack of year-round total phosphorus data for the 

lakes; (2) the transfer functions based on other Minnesota 
Summary 13

lakes, possibly with different diatom-phosphorus relations; 

(3) historic nutrient production rates may be different than 

current rates; (4) differences in field and laboratory techniques 

used for samples collected from the Swamp and Speckled 

Trout Lakes and the 89 lakes used in the transfer function; and 

(5) the time period of the sample collection may have been too 

short to capture the inherent variability of the water-quality 

data.

This study showed similarities between median values 

of recent total phosphorus concentrations in water-quality 

samples and diatom-inferred phosphorus concentrations based 

on recent sedimentation, coupled with strong analogues for 

subfossil diatom communities for both lakes within the 89 

Minnesota lakes diatom transfer function. This indicates that 

recent and historical diatom-inferred phosphorus reconstructions might be used to help develop reference conditions and 

nutrient criteria for Grand Portage Reservation lakes, when 

a sampling program is designed to ensure representative 

phosphorus concentrations in water samples are comparable to 

diatom-inferred concentrations.

Summary 

The Grand Portage Reservation, in northeastern Minnesota, established water-quality standards in 2005 and subsequently has the responsibility to derive nutrient criteria for the 

reservation. Personnel from the Grand Portage Reservation. 

0

20

40

60

80

100

120 0 10 20 30 40 50 60

0rganic

Calcium carbonate Inorganics

1760

1780

1800

1820

1840

1860

1880

1900

1920

1940

1960

1980

2000

2020

0 0.01 0.02 0.03

1760

1780

1800

1820

1840

1860

1880

1900

1920

1940

1960

1980

2000

2020

DEPTH, IN CENTIMETERS

LEAD-210 AGE, IN YEARS

LEAD-210 AGE, IN YEARS

SEDIMENT ACCUMULATION RATE, 

IN GRAMS PER SQUARE CENTIMETER PER YEAR

DRY-WEIGHT PERCENTAGE

B

D

A

C

TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER

LOGARITHM OF TOTAL PHOSPHORUS CONCENTRATION, 

IN MILLIGRAMS PER LITER

Figure 5. Speckled Trout Lake sediment core analyses, Grand Portage Reservation, Minnesota. A, dry weight percentage of 

calcium carbonate, organic matter and inorganic matter; B, sediment accumulation rates; and C, diatom-inferred total phoshorus 

concentrations for the Speckled Trout Lake sediment core, Grand Portage Reservation, Minnesota; D, model error estimates (from 

Edlund and others, 2009).

Median 2000–08

total phosphorus

concentration in

lake water

DEPTH, IN CENTIMETERS 

9

15

28

34

50

YEAR,DECIMAL

1997.6

1984.9

1940.2

1910.9

1851.8

1760

1780

1800

1820

1840

1860

1880

1900

1920

1940

1960

1980

2000

2020

0 0.005 0.010 0.015 0.020 0.025 0.030 0 0.0005 0.0010 0.0015 0.0020

Figure 5. Speckled Trout Lake sediment core analyses, Grand Portage Reservation, Minnesota. A, dry weight percentage of 

calcium carbonate, organic matter and inorganic matter; B, sediment accumulation rates; and C, diatom-inferred total phoshorus 

concentrations for the Speckled Trout Lake sediment core, Grand Portage Reservation, Minnesota; D, model error estimates (from 

Edlund and others, 2009).
14 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies

Environmental Department (GPR) have chosen to undertake a 

paleolimnological approach and direct observation to establish 

reference conditions for lakes on the reservation. A paleolimnological approach establishes the historical nutrient productivity of a lake through the characterization of nutrients and 

the fossil remains of organisms (diatoms and chrysophytes) in 

lake-sediment cores. The U.S. Geological Survey (USGS), in 

cooperation with the Grand Portage Band of Chippewa Indians 

and the Science Museum of Minnesota, conducted a study 

to describe the water quality (2000–08) and historical phosphorus concentrations (1781–2006) for Swamp and Speckled 

Trout Lakes. Results from this study may be used as a guide in 

establishing reference conditions and nutrient criteria in these 

and other lakes on the Grand Portage Reservation.

This report summarizes recent (2000–08) water-quality 

data and their comparison to historical total phosphorus 

concentrations (1781–2006) in Swamp and Speckled Trout 

Lakes. The historical total phosphorus concentrations were 

inferred through paleolimnological reconstruction methods 

involving diatom analysis of lead-210 dated lake-sediment 

cores. Water samples were analyzed for field properties, major 

ions, nutrients, and dissolved organic carbon concentrations. 

Median specific conductance, pH, and alkalinity values were 

smaller in Swamp Lake than in Speckled Trout Lake. This is 

likely because of more bogs and swamps attached to the shoreline of Swamp Lake. Median total calcium and magnesium 

concentrations were smaller in Swamp Lake than in Speckled 

Trout Lake, whereas total chloride concentrations were larger 

in Swamp Lake. 

Median nutrient concentrations for water samples collected by GPR personnel during 2000–08 in both lakes were 

small, as Swamp and Speckled Trout Lakes are not substantially affected by major sources of nutrients such as agricultural activities or wastewater discharge. Total phosphorus 

concentrations were small in both lakes with a median concentration of 0.023 mg/L in Swamp Lake and a median concentration of 0.012 mg/L in Speckled Trout Lake. Chlorophyll-a

concentration, an indicator of algal biomass, and dissolved 

organic carbon concentrations were larger in Swamp Lake 

than in Speckled Trout Lake. 

Results of loss-on-ignition analyses indicated that sediment from Swamp Lake historically has been dominated by 

the inorganic component with a shift to an organic component 

in modern sedimentation. Lead-210 dating and an age-depth 

model indicated that sediments below 16 centimeters (cm) in 

Swamp Lake were deposited prior to 1875. A large shift in 

the percentage of organic and inorganic components and in 

the sedimentation rate occurred at a core depth of 15 to 16 cm 

(1880s). This shift was likely because of logging during early 

European settlement (1880–1920) of the area. A large increase 

in sedimentation rate after 1960 likely was a result of logging 

along the northeastern shore of Swamp Lake in 1958. 

Loss-on-ignition analysis on the Speckled Trout Lake 

core indicated that the sediment historically has been dominated by the inorganic component with the organic component 

increasing between 1850 and 1900. Above a depth of 28 cm, 

the percentage of inorganic components decreased to 39 percent. Overall, sedimentation rates were slightly larger for the 

Speckled Trout Lake core than in the Swamp Lake core, possibly because of the steeper slope in the land surface surrounding Speckled Trout Lake or greater sediment focusing because 

of basin morphometry.

The diatom flora of Swamp and Speckled Trout Lakes 

was diverse. These diatoms included many rare or uncommon species and several unknown taxa. Diatom-inferred total 

phosphorus concentrations ranged from 0.017 to 0.025 mg/L 

in Swamp Lake from sediment samples dated 1781–2005 and 

from 0.008 to 0.014 mg/L in the Speckled Trout Lake core 

based on sediments dated 1825–2006. Differences among 

the diatom-inferred total phosphorus concentrations were not 

greater than the model error estimates, inferring that no major 

changes in total phosphorus concentrations occurred during 

the past 200 years in either Swamp Lake or Speckled Trout 

Lake. 

Total phosphorus concentrations from water samples 

collected from Swamp Lake during 2000–08 ranged from less 

than 0.002 to 0.160 mg/L (median=0.023 mg/L) compared to 

diatom-inferred total phosphorus concentrations of 0.018 to 

0.020 mg/L from sediments dated from 2002 to 2005. Total 

phosphorus concentrations from water samples collected from 

Speckled Trout Lake during 2000–08 were similar to those 

from Swamp Lake, whereas the diatom-inferred total phosphorus concentrations were smaller in Speckled Trout Lake 

than in Swamp Lake. Total phosphorus concentrations in 

water samples collected from Speckled Trout Lake during 

2000–08 ranged from less than 0.002 to 0.147 mg/L (median=

0.012 mg/L). Historical diatom-inferred total phosphorus 

concentrations in Speckled Trout Lake ranged from 0.009 to 

0.010 mg/L in sediments dated from 2003 to 2006. Differences 

in total phosphorus concentrations between the two lakes may 

be because of differences in watershed characteristics, particularly the number of wetlands in the two watersheds. 

Median values of recent (2000–08) total phosphorus 

concentrations in water-quality samples and diatom-inferred 

phosphorus in recent sedimentation in Swamp and Speckled 

Trout Lakes were similar. These similarities, coupled with 

strong analogues for subfossil diatom communities for both 

lakes within the 89 Minnesota lakes diatom transfer function, 

indicate that recent and historical diatom-inferred phosphorus reconstructions might be used to help establish reference 

conditions and nutrient criteria for Grand Portage Reservation 

lakes when a sampling program is designed to ensure representative phosphorus concentrations in water samples are 

comparable to diatom-inferred concentrations.
References Cited 15

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18 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies
Appendixes 1–3 19

Appendixes 1–3
20 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky condition Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH (standard units) Oxidation reduction potential (mV) Turbidity (NTU) 7/16/1997 230 -- 23.9 Clear 0.6 25.7 7.34 29 7.03 313 16.9 7/16/1997 230 -- 23.9 Clear 1.2 25.6 7.20 26 6.90 309 28.3 6/26/1998 930 28.27 21.1 Pcloudy .3 19.3 8.21 26 7.32 -- 3.0 6/26/1998 930 28.27 21.1 Pcloudy .9 18.7 8.27 25 7.21 -- 3.3 6/26/1998 930 28.27 21.1 Pcloudy 1.5 18.6 8.14 26 7.19 -- 3.8 6/26/1998 930 28.27 21.1 Pcloudy 2.1 18.4 7.81 26 7.16 -- 3.9 6/26/1998 930 28.27 21.1 Pcloudy 2.7 18.4 7.70 26 7.14 -- 4.0 6/26/1998 930 28.27 21.1 Pcloudy 3.4 18.3 7.66 26 7.05 -- 3.7 6/26/1998 930 28.27 21.1 Pcloudy 4.0 18.3 7.45 26 7.07 -- 5.8 6/26/1998 930 28.27 21.1 Pcloudy 4.6 18.2 7.40 26 7.06 -- 4.7 7/16/1998 1000 28.47 21.1 Clear .3 21.9 7.81 28 7.26 324 -- 7/16/1998 1000 28.47 21.1 Clear .9 21.9 7.29 28 7.28 319 -- 7/16/1998 1000 28.47 21.1 Clear 1.5 21.9 7.41 28 7.41 313 3.8 7/16/1998 1000 28.47 21.1 Clear 2.1 21.9 7.40 29 7.40 315 3.0 7/16/1998 1000 28.47 21.1 Clear 2.7 21.4 7.33 28 7.38 316 5.5 7/16/1998 1000 28.47 21.1 Clear 3.4 20.9 7.01 28 7.22 325 3.2 7/16/1998 1000 28.47 21.1 Clear 4.0 20.7 6.93 28 7.22 325 4.1 7/16/1998 1000 28.47 21.1 Clear 4.6 20.6 6.88 28 7.20 321 6.9 9/25/1998 1000 27.99 15.6 Pcloudy .3 12.8 9.75 30 7.35 333 3.0 9/25/1998 1000 27.99 15.6 Pcloudy .9 12.7 9.25 30 7.32 343 5.7

9/25/1998 1000 27.99 15.6 Pcloudy 1.5 12.7 9.17 30 7.37 347 5.79/25/1998 1000 27.99 15.6 Pcloudy 2.1 12.7 9.14 31 7.37 351 5.59/25/1998 1000 27.99 15.6 Pcloudy 2.7 12.8 9.07 31 7.37 354 5.99/25/1998 1000 27.99 15.6 Pcloudy 3.4 12.8 9.05 31 7.37 357 5.89/25/1998 1000 27.99 15.6 Pcloudy 4.0 12.6 8.43 32 7.28 357 5.59/25/1998 1000 27.99 15.6 Pcloudy 4.6 12.6 2.77 43 6.38 283 8.1
Appendixes 1–3 21

Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air 

temperature 

(°C)

Sky

condition

Depth 

(m)

Water

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

10/21/1998 1150 28.65 7.2 Pcloudy 0.3 5.4 11.77 28 6.94 268 3.310/21/1998 1150 28.65 7.2 Pcloudy .6 5.4 11.71 28 6.88 264 3.510/21/1998 1150 28.65 7.2 Pcloudy .9 5.4 11.63 28 6.89 264 3.310/21/1998 1150 28.65 7.2 Pcloudy 1.2 5.4 11.60 28 6.90 263 3.410/21/1998 1150 28.65 7.2 Pcloudy 1.5 5.4 11.59 28 6.90 263 3.210/21/1998 1150 28.65 7.2 Pcloudy 1.8 5.4 11.53 28 6.90 263 3.210/21/1998 1150 28.65 7.2 Pcloudy 2.1 5.4 11.48 28 6.90 262 3.410/21/1998 1150 28.65 7.2 Pcloudy 2.4 5.4 11.49 28 6.92 261 3.210/21/1998 1150 28.65 7.2 Pcloudy 2.7 5.4 11.50 28 6.91 261 3.210/21/1998 1150 28.65 7.2 Pcloudy 3.0 5.4 11.45 28 6.93 261 3.010/21/1998 1150 28.65 7.2 Pcloudy 3.4 5.4 11.50 28 6.93 261 3.410/21/1998 1150 28.65 7.2 Pcloudy 3.7 5.4 11.49 28 6.93 260 3.010/21/1998 1150 28.65 7.2 Pcloudy 4.0 5.4 11.44 28 6.93 260 3.410/21/1998 1150 28.65 7.2 Pcloudy 4.3 5.4 11.46 28 6.93 260 3.210/21/1998 1150 28.65 7.2 Pcloudy 4.6 5.4 11.46 28 6.94 255 4.25/1/2000 1021 29.09 20.7 Pcloudy .3 11.3 10.24 32 7.08 357 --5/1/2000 1021 29.09 20.7 Pcloudy .9 11.3 10.13 32 7.01 356 --5/1/2000 1021 29.09 20.7 Pcloudy 1.5 10.7 4.79 27 6.64 237 --5/1/2000 1021 29.09 20.7 Pcloudy 2.1 10.7 4.79 37 6.32 252 3.05/1/2000 1021 29.09 20.7 Pcloudy 2.7 11.0 4.60 37 6.29 251 --5/1/2000 1021 29.09 20.7 Pcloudy 3.4 10.9 4.63 37 6.23 243 --5/1/2000 1021 29.09 20.7 Pcloudy 4.0 10.9 .10 37 6.23 240 --6/6/2000 950 29.44 20.6 Pcloudy .3 15.8 9.16 30 7.15 368 --6/6/2000 950 29.44 20.6 Pcloudy .6 15.8 9.25 30 7.16 363 --6/6/2000 950 29.44 20.6 Pcloudy .9 15.8 9.11 30 7.12 365 --6/6/2000 950 29.44 20.6 Pcloudy 1.2 15.8 9.11 31 7.09 366 --6/6/2000 950 29.44 20.6 Pcloudy 1.5 15.8 9.12 31 7.06 366 --
22 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky condition Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH (standard units) Oxidation reduction potential (mV) Turbidity (NTU) 6/6/2000 950 29.44 20.6 Pcloudy 1.8 15.8 9.08 31 7.13 363 -- 6/6/2000 950 29.44 20.6 Pcloudy 2.1 15.8 9.03 31 7.12 363 -- 6/6/2000 950 29.44 20.6 Pcloudy 2.4 15.7 9.06 31 7.06 365 -- 6/6/2000 950 29.44 20.6 Pcloudy 2.7 15.8 9.03 31 7.05 364 -- 6/6/2000 950 29.44 20.6 Pcloudy 3.0 15.6 9.02 31 7.03 365 -- 6/6/2000 950 29.44 20.6 Pcloudy 3.4 15.6 9.02 31 7.04 364 -- 6/6/2000 950 29.44 20.6 Pcloudy 3.7 15.5 8.94 31 7.04 364 -- 6/6/2000 950 29.44 20.6 Pcloudy 4.0 15.5 8.88 31 7.02 364 -- 6/6/2000 950 29.44 20.6 Pcloudy 4.3 15.3 9.69 31 7.04 361 -- 6/6/2000 950 29.44 20.6 Pcloudy 4.6 15.2 8.91 31 6.99 362 -- 6/6/2000 950 29.44 20.6 Pcloudy 4.9 14.9 8.73 31 7.02 362 -- 6/6/2000 950 29.44 20.6 Pcloudy 5.2 14.5 .70 108 6.10 296 -- 7/10/2000 1010 29.32 24.9 Pcloudy .3 21.8 8.91 31 7.25 311 1.6 7/10/2000 1010 29.32 24.9 Pcloudy .6 21.8 8.92 31 7.24 311 3.1 7/10/2000 1010 29.32 24.9 Pcloudy .9 21.9 9.02 31 7.23 311 2.6 7/10/2000 1010 29.32 24.9 Pcloudy 1.2 21.8 8.77 31 7.23 310 3.2 7/10/2000 1010 29.32 24.9 Pcloudy 1.5 21.9 8.36 31 7.24 310 2.2 7/10/2000 1010 29.32 24.9 Pcloudy 1.8 21.9 8.47 31 7.25 310 2.3 7/10/2000 1010 29.32 24.9 Pcloudy 2.1 21.8 8.45 31 7.25 310 2.3 7/10/2000 1010 29.32 24.9 Pcloudy 2.4 21.8 8.46 31 7.23 311 2.4 7/10/2000 1010 29.32 24.9 Pcloudy 2.7 21.8 7.49 31 6.90 209 2.4 7/10/2000 1010 29.32 24.9 Pcloudy 3.0 21.3 7.97 31 7.05 218 2.7

7/10/2000 1010 29.32 24.9 Pcloudy 3.4 21.0 6.73 33 6.08 183 2.67/10/2000 1010 29.32 24.9 Pcloudy 3.7 18.6 6.41 33 6.52 218 2.47/10/2000 1010 29.32 24.9 Pcloudy 4.0 18.3 4.02 34 6.41 189 2.37/10/2000 1010 29.32 24.9 Pcloudy 4.3 18.3 5.64 34 6.41 207 2.47/10/2000 1010 29.32 24.9 Pcloudy 4.6 18.0 1.74 86 6.07 1,434 27.1
Appendixes 1–3 23

Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air 

temperature 

(°C)

Sky

condition

Depth 

(m)

Water

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

8/15/2000 950 29.59 23.6 Pcloudy 0.3 19.8 8.35 36 6.92 291 3.18/15/2000 950 29.59 23.6 Pcloudy .6 19.8 8.35 36 6.92 291 4.48/15/2000 950 29.59 23.6 Pcloudy .9 19.8 8.34 35 6.92 291 4.78/15/2000 950 29.59 23.6 Pcloudy 1.2 19.8 8.38 36 6.92 291 2.88/15/2000 950 29.59 23.6 Pcloudy 1.5 19.7 8.24 36 6.90 291 3.38/15/2000 950 29.59 23.6 Pcloudy 1.8 19.7 8.18 35 6.89 292 2.78/15/2000 950 29.59 23.6 Pcloudy 2.1 19.7 8.15 36 6.91 291 3.08/15/2000 950 29.59 23.6 Pcloudy 2.4 19.7 8.31 36 6.92 292 2.98/15/2000 950 29.59 23.6 Pcloudy 2.7 19.7 8.32 36 6.92 292 3.08/15/2000 950 29.59 23.6 Pcloudy 3.0 19.7 8.33 35 6.93 292 3.38/15/2000 950 29.59 23.6 Pcloudy 3.4 19.7 8.28 35 6.93 293 3.18/15/2000 950 29.59 23.6 Pcloudy 3.7 19.7 8.33 36 6.92 294 3.38/15/2000 950 29.59 23.6 Pcloudy 4.0 19.7 8.30 36 6.92 294 3.18/15/2000 950 29.59 23.6 Pcloudy 4.3 19.7 8.30 36 6.92 295 3.28/15/2000 950 29.59 23.6 Pcloudy 4.6 19.7 8.23 36 6.91 295 3.18/15/2000 950 29.59 23.6 Pcloudy 4.9 19.6 3.21 42 6.25 155 --9/11/2000 1035 28.73 24.1 Pcloudy .3 16.7 9.13 33 7.27 344 --9/11/2000 1035 28.73 24.1 Pcloudy .6 16.3 9.09 33 7.22 346 1.89/11/2000 1035 28.73 24.1 Pcloudy .9 16.2 9.05 33 7.17 348 2.29/11/2000 1035 28.73 24.1 Pcloudy 1.2 16.1 9.01 33 7.12 349 2.79/11/2000 1035 28.73 24.1 Pcloudy 1.5 16.1 8.90 33 7.10 349 2.19/11/2000 1035 28.73 24.1 Pcloudy 1.8 16.0 8.83 33 7.07 351 2.39/11/2000 1035 28.73 24.1 Pcloudy 2.1 15.9 8.82 33 7.08 350 2.39/11/2000 1035 28.73 24.1 Pcloudy 2.4 15.9 8.85 33 7.07 350 2.49/11/2000 1035 28.73 24.1 Pcloudy 2.7 15.9 8.63 33 6.89 234 2.39/11/2000 1035 28.73 24.1 Pcloudy 3.0 15.9 8.84 33 7.00 223 2.89/11/2000 1035 28.73 24.1 Pcloudy 3.4 15.9 8.75 33 6.99 224 2.39/11/2000 1035 28.73 24.1 Pcloudy 3.7 15.8 8.44 34 6.89 206 2.3
24 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky condition Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH (standard units) Oxidation reduction potential (mV) Turbidity (NTU) 9/11/2000 1035 28.73 24.1 Pcloudy 4.0 15.7 8.00 34 6.51 196 2.8 9/11/2000 1035 28.73 24.1 Pcloudy 4.3 14.7 7.36 37 6.36 191 -- 10/3/2000 1005 28.85 20.9 Clear .3 12.0 9.98 34 7.43 347 -- 10/3/2000 1005 28.85 20.9 Clear .6 12.0 9.90 34 7.43 347 0 10/3/2000 1005 28.85 20.9 Clear .9 12.0 9.84 34 7.40 348 2.9 10/3/2000 1005 28.85 20.9 Clear 1.2 11.9 9.90 34 7.37 348 1.9 10/3/2000 1005 28.85 20.9 Clear 1.5 11.9 9.81 34 7.40 347 2.0 10/3/2000 1005 28.85 20.9 Clear 1.8 11.8 9.83 34 7.37 348 2.3 10/3/2000 1005 28.85 20.9 Clear 2.1 11.7 9.82 34 7.37 347 2.4 10/3/2000 1005 28.85 20.9 Clear 2.4 11.7 9.83 34 7.37 346 2.5 10/3/2000 1005 28.85 20.9 Clear 2.7 11.7 9.90 34 7.37 346 2.1 10/3/2000 1005 28.85 20.9 Clear 3.0 11.6 9.86 34 7.40 345 2.2 10/3/2000 1005 28.85 20.9 Clear 3.4 11.6 9.91 34 7.40 345 3.0 10/3/2000 1005 28.85 20.9 Clear 3.7 11.6 9.90 34 7.40 345 2.2 10/3/2000 1005 28.85 20.9 Clear 4.0 11.6 9.98 34 7.41 344 2.8 10/3/2000 1005 28.85 20.9 Clear 4.3 11.6 9.94 34 7.41 345 2.2 10/3/2000 1005 28.85 20.9 Clear 4.6 11.6 9.91 34 7.41 344 2.5 10/3/2000 1005 28.85 20.9 Clear 4.9 11.6 9.94 34 7.39 330 20.1 5/13/2002 939 29.12 17.5 Pcloudy .3 8.1 12.31 20 6.99 435 6.7 5/13/2002 939 29.12 17.5 Pcloudy .6 8.1 12.20 20 6.94 430 6.4 5/13/2002 939 29.12 17.5 Pcloudy .9 8.0 12.14 20 6.89 428 6.4

5/13/2002 939 29.12 17.5 Pcloudy 1.2 8.0 12.11 20 6.88 426 6.55/13/2002 939 29.12 17.5 Pcloudy 1.5 7.8 12.11 20 6.87 424 6.35/13/2002 939 29.12 17.5 Pcloudy 1.8 7.8 12.02 21 6.86 422 6.35/13/2002 939 29.12 17.5 Pcloudy 2.1 7.8 11.97 20 6.84 421 6.35/13/2002 939 29.12 17.5 Pcloudy 2.4 7.8 11.96 21 6.83 420 6.05/13/2002 939 29.12 17.5 Pcloudy 2.7 7.6 -- 126 6.40 132 --
Appendixes 1–3 25

Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air 

temperature 

(°C)

Sky

condition

Depth 

(m)

Water

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

6/17/2002 1010 29.06 24.9 Pcloudy 0.3 18.1 9.00 29 7.21 369 9.86/17/2002 1010 29.06 24.9 Pcloudy .6 18.0 9.09 29 7.22 366 9.36/17/2002 1010 29.06 24.9 Pcloudy .9 17.8 9.13 29 7.21 365 10.26/17/2002 1010 29.06 24.9 Pcloudy 1.2 17.7 9.06 29 7.19 364 9.86/17/2002 1010 29.06 24.9 Pcloudy 1.5 17.7 9.01 29 7.15 356 12.96/17/2002 1010 29.06 24.9 Pcloudy 1.8 17.4 8.94 29 7.10 356 9.56/17/2002 1010 29.06 24.9 Pcloudy 2.1 17.3 8.84 29 7.05 354 15.26/17/2002 1010 29.06 24.9 Pcloudy 2.4 17.2 8.81 29 7.03 352 11.86/17/2002 1010 29.06 24.9 Pcloudy 2.7 17.1 8.72 29 7.00 351 9.66/17/2002 1010 29.06 24.9 Pcloudy 3.0 17.0 8.59 29 6.70 350 10.36/17/2002 1010 29.06 24.9 Pcloudy 3.4 17.0 8.51 29 6.89 352 9.66/17/2002 1010 29.06 24.9 Pcloudy 3.7 17.0 8.60 29 7.09 350 9.27/17/2002 940 29.12 27.5 Pcloudy .3 25.4 7.16 37 7.18 376 9.67/17/2002 940 29.12 27.5 Pcloudy .6 25.3 7.17 37 7.15 376 9.77/17/2002 940 29.12 27.5 Pcloudy .9 25.3 7.19 37 7.16 376 9.67/17/2002 940 29.12 27.5 Pcloudy 1.2 25.3 7.27 37 7.14 376 9.37/17/2002 940 29.12 27.5 Pcloudy 1.5 25.3 7.12 37 7.11 376 9.27/17/2002 940 29.12 27.5 Pcloudy 1.8 25.2 7.14 37 7.11 376 9.57/17/2002 940 29.12 27.5 Pcloudy 2.1 25.2 6.98 37 7.06 377 9.77/17/2002 940 29.12 27.5 Pcloudy 2.4 24.9 6.75 37 6.98 380 9.67/17/2002 940 29.12 27.5 Pcloudy 2.7 24.7 6.35 37 6.86 380 9.57/17/2002 940 29.12 27.5 Pcloudy 3.0 24.5 4.96 39 6.76 386 9.97/17/2002 940 29.12 27.5 Pcloudy 3.4 20.4 3.52 40 6.73 219 10.07/17/2002 940 29.12 27.5 Pcloudy 3.7 19.5 1.01 53 6.86 163 10.07/17/2002 940 29.12 27.5 Pcloudy 4.0 18.6 .31 59 7.13 109 10.47/17/2002 940 29.12 27.5 Pcloudy 4.3 18.1 .20 83 7.14 77 --
26 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky condition Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH (standard units) Oxidation reduction potential (mV) Turbidity (NTU) 8/13/2002 211 29 24.4 Pcloudy 0.3 21.7 9.03 35 7.91 300 10.4 8/13/2002 211 29 24.4 Pcloudy .6 21.6 9.27 35 7.88 301 10.1 8/13/2002 211 29 24.4 Pcloudy .9 21.6 9.00 35 7.86 301 10.3 8/13/2002 211 29 24.4 Pcloudy 1.2 21.5 8.91 35 7.72 305 10.2 8/13/2002 211 29 24.4 Pcloudy 1.5 21.3 8.91 35 7.62 309 10.3 8/13/2002 211 29 24.4 Pcloudy 1.8 20.8 8.33 36 7.46 314 10.3 8/13/2002 211 29 24.4 Pcloudy 2.1 20.7 8.53 36 7.37 318 10.5 8/13/2002 211 29 24.4 Pcloudy 2.4 20.6 8.10 36 7.27 321 10.2 8/13/2002 211 29 24.4 Pcloudy 2.7 20.5 7.54 36 7.16 324 10.4 8/13/2002 211 29 24.4 Pcloudy 3.0 20.5 7.04 36 7.07 328 10.5 8/13/2002 211 29 24.4 Pcloudy 3.4 20.3 7.01 37 6.95 331 11.1 8/13/2002 211 29 24.4 Pcloudy 3.7 20.3 4.42 41 6.88 280 -- 9/10/2002 1018 29.18 16.7 Clear .3 20.2 8.56 35 7.10 356 10.8 9/10/2002 1018 29.18 16.7 Clear .6 20.1 8.27 35 7.05 356 10.6 9/10/2002 1018 29.18 16.7 Clear .9 20.1 8.30 34 7.05 356 10.7 9/10/2002 1018 29.18 16.7 Clear 1.2 20.1 8.29 35 7.04 355 10.8 9/10/2002 1018 29.18 16.7 Clear 1.5 20.1 8.21 34 7.01 355 10.7 9/10/2002 1018 29.18 16.7 Clear 1.8 20.1 8.24 35 7.01 355 10.6 9/10/2002 1018 29.18 16.7 Clear 2.1 20.1 8.11 35 6.97 356 10.7 9/10/2002 1018 29.18 16.7 Clear 2.4 20.1 8.18 34 6.96 356 10.8 9/10/2002 1018 29.18 16.7 Clear 2.7 20.1 8.08 34 6.94 356 11.1 9/10/2002 1018 29.18 16.7 Clear 3.0 20.0 8.11 35 6.92 357 10.5

9/10/2002 1018 29.18 16.7 Clear 3.4 20.1 8.09 35 6.92 356 10.99/10/2002 1018 29.18 16.7 Clear 3.7 20.0 8.11 35 9.88 357 11.09/10/2002 1018 29.18 16.7 Clear 4.0 20.0 8.11 35 6.89 358 11.310/2/2002 1120 29.44 15.6 Pcloudy .3 11.2 11.07 30 7.71 369 11.310/2/2002 1120 29.44 15.6 Pcloudy .6 11.1 11.13 30 7.70 369 10.5
Appendixes 1–3 27

Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air 

temperature 

(°C)

Sky

condition

Depth 

(m)

Water

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

10/2/2002 1120 29.44 15.6 Pcloudy 0.9 11.2 10.95 30 7.72 367 11.210/2/2002 1120 29.44 15.6 Pcloudy 1.2 11.2 10.95 30 7.72 367 10.710/2/2002 1120 29.44 15.6 Pcloudy 1.5 11.2 10.87 30 7.72 367 10.810/2/2002 1120 29.44 15.6 Pcloudy 1.8 11.2 10.89 30 7.64 367 10.910/2/2002 1120 29.44 15.6 Pcloudy 2.1 11.2 10.98 30 7.67 368 10.810/2/2002 1120 29.44 15.6 Pcloudy 2.4 11.2 10.84 30 7.66 368 10.810/2/2002 1120 29.44 15.6 Pcloudy 2.7 11.2 10.94 30 7.66 364 10.610/2/2002 1120 29.44 15.6 Pcloudy 3.0 11.1 10.86 30 7.63 369 10.710/2/2002 1120 29.44 15.6 Pcloudy 3.4 11.1 10.85 30 7.61 369 10.810/2/2002 1120 29.44 15.6 Pcloudy 3.7 11.0 -- 30 7.59 369 --5/24/2004 1005 29.97 16.6 Clear .3 9.2 10.82 25 6.63 184 10.45/24/2004 1005 29.97 16.6 Clear .6 9.2 10.83 25 6.63 213 10.05/24/2004 1005 29.97 16.6 Clear .9 9.0 10.87 25 6.51 234 10.35/24/2004 1005 29.97 16.6 Clear 1.2 8.9 10.86 25 6.49 245 9.95/24/2004 1005 29.97 16.6 Clear 1.5 8.9 10.93 25 6.46 251 10.15/24/2004 1005 29.97 16.6 Clear 1.8 8.9 10.84 25 6.46 255 9.95/24/2004 1005 29.97 16.6 Clear 2.1 8.8 10.86 25 6.45 259 10.15/24/2004 1005 29.97 16.6 Clear 2.4 8.9 10.81 25 6.46 233 10.85/24/2004 1005 29.97 16.6 Clear 2.7 8.9 9.95 25 6.13 105 --5/24/2004 1005 29.97 16.6 Clear 3.0 9.3 6.09 147 5.93 67 --5/24/2004 1005 29.97 16.6 Clear 3.4 9.4 1.45 128 5.96 60 --6/7/2004 1001 28.91 15.3 Cloudy .3 16.4 9.69 25 6.52 393 10.56/7/2004 1001 28.91 15.3 Cloudy .6 16.4 9.46 25 6.51 392 10.36/7/2004 1001 28.91 15.3 Cloudy .9 16.2 9.34 26 6.47 392 10.66/7/2004 1001 28.91 15.3 Cloudy 1.2 16.2 9.42 25 6.45 392 10.76/7/2004 1001 28.91 15.3 Cloudy 1.5 16.2 9.29 25 6.45 392 10.86/7/2004 1001 28.91 15.3 Cloudy 1.8 16.2 9.32 25 6.44 392 9.8
28 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky condition Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH (standard units) Oxidation reduction potential (mV) Turbidity (NTU) 6/7/2004 1001 28.91 15.3 Cloudy 2.1 16.2 9.38 26 6.42 310 10.1 6/7/2004 1001 28.91 15.3 Cloudy 2.4 16.0 9.36 25 6.41 324 9.7 6/7/2004 1001 28.91 15.3 Cloudy 2.7 16.2 9.09 25 6.39 319 10.7 6/7/2004 1001 28.91 15.3 Cloudy 3.0 15.5 8.75 26 6.28 294 10.1 6/7/2004 1001 28.91 15.3 Cloudy 3.4 14.9 7.92 46 5.94 112 10.7 6/7/2004 1001 28.91 15.3 Cloudy 3.7 14.7 5.15 47 6.02 145 -- 6/7/2004 1001 28.91 15.3 Cloudy 4.0 15.1 2.12 202 6.06 97 -- 7/12/2004 930 29.06 23.4 Clear .3 21.8 8.21 29 6.95 342 11.6 7/12/2004 930 29.06 23.4 Clear .6 21.5 8.20 29 6.92 341 12.6 7/12/2004 930 29.06 23.4 Clear .9 21.1 8.11 29 6.93 338 11.7 7/12/2004 930 29.06 23.4 Clear 1.2 20.9 8.12 29 6.94 335 11.4 7/12/2004 930 29.06 23.4 Clear 1.5 19.3 7.03 30 6.62 343 11.7 7/12/2004 930 29.06 23.4 Clear 1.8 18.1 7.08 29 6.55 343 11.3 7/12/2004 930 29.06 23.4 Clear 2.1 17.5 6.94 30 6.48 344 11.0 7/12/2004 930 29.06 23.4 Clear 2.4 17.1 6.90 30 6.47 344 11.3 7/12/2004 930 29.06 23.4 Clear 2.7 16.8 6.90 30 6.46 343 11.3 7/12/2004 930 29.06 23.4 Clear 3.0 16.7 6.82 30 6.43 344 11.0 7/12/2004 930 29.06 23.4 Clear 3.4 16.5 6.15 31 6.39 345 11.1 7/12/2004 930 29.06 23.4 Clear 3.7 16.4 5.89 32 6.35 346 11.7 7/12/2004 930 29.06 23.4 Clear 4.0 16.3 3.47 108 6.08 137 -- 8/2/2004 222 29.06 27.8 Pcloudy .3 23.2 9.07 32 7.54 389 39.1

8/2/2004 222 29.06 27.8 Pcloudy .6 22.5 9.09 31 7.47 389 29.78/2/2004 222 29.06 27.8 Pcloudy .9 21.8 9.05 32 7.47 389 40.48/2/2004 222 29.06 27.8 Pcloudy 1.2 21.4 9.04 32 7.43 391 39.68/2/2004 222 29.06 27.8 Pcloudy 1.5 21.1 9.04 32 7.36 393 39.48/2/2004 222 29.06 27.8 Pcloudy 1.8 21.0 8.96 32 7.32 394 39.28/2/2004 222 29.06 27.8 Pcloudy 2.1 21.0 8.96 32 7.29 395 39.1
Appendixes 1–3 29

Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air 

temperature 

(°C)

Sky

condition

Depth 

(m)

Water

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

8/2/2004 222 29.06 27.8 Pcloudy 2.4 20.3 8.61 32 7.23 397 39.48/2/2004 222 29.06 27.8 Pcloudy 2.7 19.8 8.22 32 7.15 398 39.18/2/2004 222 29.06 27.8 Pcloudy 3.0 19.4 7.93 32 7.07 397 17.18/2/2004 222 29.06 27.8 Pcloudy 3.4 18.9 3.19 220 6.19 277 --8/2/2004 222 29.06 27.8 Pcloudy 3.7 18.7 1.53 200 6.10 247 --9/7/2004 947 30.05 16.4 Cloudy .3 16.4 10.24 33 7.01 333 5.29/7/2004 947 30.05 16.4 Cloudy .6 16.4 9.95 33 6.95 327 5.39/7/2004 947 30.05 16.4 Cloudy .9 16.4 9.81 33 6.89 323 5.49/7/2004 947 30.05 16.4 Cloudy 1.2 16.3 9.60 33 6.86 318 5.49/7/2004 947 30.05 16.4 Cloudy 1.5 16.3 9.60 33 6.83 315 5.39/7/2004 947 30.05 16.4 Cloudy 1.8 16.2 9.58 33 6.79 312 5.39/7/2004 947 30.05 16.4 Cloudy 2.1 16.3 9.56 33 6.81 309 5.39/7/2004 947 30.05 16.4 Cloudy 2.4 16.1 9.44 33 6.76 308 5.29/7/2004 947 30.05 16.4 Cloudy 2.7 15.9 9.31 33 6.74 307 5.19/7/2004 947 30.05 16.4 Cloudy 3.0 15.9 9.35 33 6.77 306 5.29/7/2004 947 30.05 16.4 Cloudy 3.4 15.9 9.38 33 6.69 304 5.19/7/2004 947 30.05 16.4 Cloudy 3.7 15.9 9.39 33 6.88 304 5.39/7/2004 947 30.05 16.4 Cloudy 4.0 15.9 8.93 33 6.55 240 --9/7/2004 947 30.05 16.4 Cloudy 4.3 15.9 5.91 69 6.06 108 --10/6/2004 120 28.37 19.9 Clear .3 7.9 12.61 31 7.64 284 .710/6/2004 120 28.37 19.9 Clear .6 7.8 12.51 31 7.60 283 .810/6/2004 120 28.37 19.9 Clear .9 7.7 12.43 31 7.59 281 .710/6/2004 120 28.37 19.9 Clear 1.2 7.6 12.49 31 7.62 279 .810/6/2004 120 28.37 19.9 Clear 1.5 7.5 12.52 31 7.62 278 .810/6/2004 120 28.37 19.9 Clear 1.8 7.5 12.55 31 7.62 276 .910/6/2004 120 28.37 19.9 Clear 2.1 7.5 12.47 31 7.60 275 .810/6/2004 120 28.37 19.9 Clear 2.4 7.2 12.49 31 7.60 275 .8
30 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky condition Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH (standard units) Oxidation reduction potential (mV) Turbidity (NTU) 10/6/2004 120 28.37 19.9 Clear 2.7 7.1 12.36 31 7.57 276 0.7 10/6/2004 120 28.37 19.9 Clear 3.0 7.0 12.33 31 7.55 275 .7 10/6/2004 120 28.37 19.9 Clear 3.4 7.0 11.67 33 7.24 226 2.6 10/6/2004 120 28.37 19.9 Clear 3.7 7.0 12.26 34 7.20 224 -- 10/6/2004 120 28.37 19.9 Clear 4.0 7.2 5.15 222 6.31 140 -- 10/6/2004 120 28.37 19.9 Clear 4.3 8.5 2.87 247 6.32 150 -- 5/15/2006 930 29.26 13.3 Cloudy .3 8.9 12.53 18 6.78 454 0 5/15/2006 930 29.26 13.3 Cloudy .6 8.8 12.49 18 6.79 453 0 5/15/2006 930 29.26 13.3 Cloudy .9 8.8 12.38 18 6.82 450 0 5/15/2006 930 29.26 13.3 Cloudy 1.2 8.8 12.36 17 6.84 450 0 5/15/2006 930 29.26 13.3 Cloudy 1.5 8.8 12.28 18 6.84 450 0 5/15/2006 930 29.26 13.3 Cloudy 1.8 8.7 12.30 18 6.85 450 0 5/15/2006 930 29.26 13.3 Cloudy 2.1 8.6 12.25 18 6.85 451 0 5/15/2006 930 29.26 13.3 Cloudy 2.4 8.5 12.31 18 6.86 452 0 5/15/2006 930 29.26 13.3 Cloudy 2.7 8.6 12.12 18 6.90 305 .5 5/15/2006 930 29.26 13.3 Cloudy 3.0 8.6 12.21 18 6.90 320 .2 5/15/2006 930 29.26 13.3 Cloudy 3.4 8.1 12.28 18 6.92 329 .7 5/15/2006 930 29.26 13.3 Cloudy 3.7 7.5 4.96 123 6.49 200 -- 5/15/2006 930 29.26 13.3 Cloudy 4.0 7.8 .94 153 6.57 170 -- 6/7/2006 930 29.06 24.3 Clear .3 19.9 7.95 22 6.91 235 1.4 6/7/2006 930 29.06 24.3 Clear .6 19.8 8.00 22 6.89 242 1.5

6/7/2006 930 29.06 24.3 Clear .9 19.8 7.95 22 6.82 248 1.46/7/2006 930 29.06 24.3 Clear 1.2 19.7 7.94 22 6.85 253 1.46/7/2006 930 29.06 24.3 Clear 1.5 19.5 7.90 22 6.89 255 1.46/7/2006 930 29.06 24.3 Clear 1.8 19.5 7.81 22 6.87 259 1.46/7/2006 930 29.06 24.3 Clear 2.1 19.0 7.32 23 6.85 262 1.56/7/2006 930 29.06 24.3 Clear 2.4 19.0 7.38 22 6.85 263 1.4
Appendixes 1–3 31

Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air 

temperature 

(°C)

Sky

condition

Depth 

(m)

Water

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

6/7/2006 930 29.06 24.3 Clear 2.7 19.0 7.34 22 6.84 265 1.46/7/2006 930 29.06 24.3 Clear 3.0 19.9 7.14 22 6.83 266 1.66/7/2006 930 29.06 24.3 Clear 3.4 18.9 7.03 23 6.77 265 --6/7/2006 930 29.06 24.3 Clear 3.7 18.5 2.24 82 6.43 170 --6/7/2006 930 29.06 24.3 Clear 4.0 16.7 1.75 196 6.47 135 --6/7/2006 930 29.06 24.3 Clear 4.3 15.1 .85 153 6.54 117 --7/10/2006 930 29.21 14.8 Clear .3 20.6 8.50 26 6.79 249 7.57/11/2006 930 29.21 14.8 Clear .6 20.2 8.53 26 6.79 270 7.67/12/2006 930 29.21 14.8 Clear .9 20.0 8.52 26 6.79 277 7.17/13/2006 930 29.21 14.8 Clear 1.2 19.8 8.34 26 6.68 286 6.27/14/2006 930 29.21 14.8 Clear 1.5 19.7 8.37 26 6.85 289 5.77/15/2006 930 29.21 14.8 Clear 1.8 19.6 8.32 26 6.84 290 5.57/16/2006 930 29.21 14.8 Clear 2.1 19.6 8.26 26 6.85 292 5.37/17/2006 930 29.21 14.8 Clear 2.4 19.6 8.19 26 6.84 294 5.47/18/2006 930 29.21 14.8 Clear 2.7 19.5 8.17 26 6.83 296 5.57/19/2006 930 29.21 14.8 Clear 3.0 19.4 8.14 26 6.84 298 5.77/20/2006 930 29.21 14.8 Clear 3.4 19.4 8.00 26 6.81 294 --7/21/2006 930 29.21 14.8 Clear 3.7 19.4 5.18 88 6.09 201 --7/22/2006 930 29.21 14.8 Clear 4.0 19.3 4.75 125 6.13 190 --7/23/2006 930 29.21 14.8 Clear 4.3 19.3 5.04 185 6.15 170 --8/15/2006 1012 29.68 17.2 Clear .3 17.8 10.09 29 7.09 374 5.48/15/2006 1012 29.68 17.2 Clear .6 17.8 9.60 29 7.02 376 5.68/15/2006 1012 29.68 17.2 Clear .9 17.8 9.44 29 7.01 377 5.78/15/2006 1012 29.68 17.2 Clear 1.2 17.8 9.48 29 7.03 377 5.78/15/2006 1012 29.68 17.2 Clear 1.5 17.6 9.33 29 7.06 375 5.58/15/2006 1012 29.68 17.2 Clear 1.8 17.4 9.16 29 7.06 374 5.68/15/2006 1012 29.68 17.2 Clear 2.1 17.3 9.25 29 7.05 375 5.7
32 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky condition Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH (standard units) Oxidation reduction potential (mV) Turbidity (NTU) 8/15/2006 1012 29.68 17.2 Clear 2.4 17.2 9.13 29 7.03 376 5.5 8/15/2006 1012 29.68 17.2 Clear 2.7 17.2 9.08 29 7.06 377 5.4 8/15/2006 1012 29.68 17.2 Clear 3.0 17.1 8.87 29 7.06 378 5.5 8/15/2006 1012 29.68 17.2 Clear 3.4 17.0 8.54 29 6.74 383 5.1 8/15/2006 1012 29.68 17.2 Clear 3.7 17.4 1.03 184 6.15 299 -- 9/11/2006 1005 29.41 14.3 Pcloudy .3 14.7 9.73 32 7.42 384 3.3 9/11/2006 1005 29.41 14.3 Pcloudy .6 14.5 9.65 32 7.33 388 3.5 9/11/2006 1005 29.41 14.3 Pcloudy .9 14.3 9.47 32 7.24 392 3.6 9/11/2006 1005 29.41 14.3 Pcloudy 1.2 14.2 9.47 32 7.18 394 3.4 9/11/2006 1005 29.41 14.3 Pcloudy 1.5 14.2 9.52 32 7.16 395 3.5 9/11/2006 1005 29.41 14.3 Pcloudy 1.8 14.1 9.39 32 7.13 396 3.2 9/11/2006 1005 29.41 14.3 Pcloudy 2.1 14.1 9.38 32 7.11 397 3.4 9/11/2006 1005 29.41 14.3 Pcloudy 2.4 14.1 9.48 33 7.11 398 3.0 9/11/2006 1005 29.41 14.3 Pcloudy 2.7 14.0 9.24 33 7.10 399 3.6 9/11/2006 1005 29.41 14.3 Pcloudy 3.0 14.0 9.53 33 7.08 399 3.8 9/11/2006 1005 29.41 14.3 Pcloudy 3.4 13.9 9.20 32 7.06 401 4.8 9/11/2006 1005 29.41 14.3 Pcloudy 3.7 13.9 9.08 33 6.86 369 6.0 10/3/2006 955 29.21 12.3 Cloudy .3 11.8 11.44 30 7.42 379 4.3 10/3/2006 955 29.21 12.3 Cloudy .6 11.8 11.43 30 7.37 381 4.2 10/3/2006 955 29.21 12.3 Cloudy .9 11.8 11.45 30 7.32 383 4.2 10/3/2006 955 29.21 12.3 Cloudy 1.2 11.7 11.31 30 7.29 384 4.3

10/3/2006 955 29.21 12.3 Cloudy 1.5 11.7 11.36 30 7.29 384 4.410/3/2006 955 29.21 12.3 Cloudy 1.8 11.6 11.40 30 7.27 385 4.410/3/2006 955 29.21 12.3 Cloudy 2.1 11.2 11.45 30 7.26 386 4.410/3/2006 955 29.21 12.3 Cloudy 2.4 10.5 11.08 30 7.18 391 4.610/3/2006 955 29.21 12.3 Cloudy 2.7 9.3 10.73 30 7.06 397 4.610/3/2006 955 29.21 12.3 Cloudy 3.0 8.8 10.46 30 7.00 400 5.0
Appendixes 1–3 33

Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air 

temperature 

(°C)

Sky

condition

Depth 

(m)

Water

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

10/3/2006 955 29.21 12.3 Cloudy 3.4 8.7 10.20 30 6.94 403 5.110/3/2006 955 29.21 12.3 Cloudy 3.7 8.6 10.09 30 6.89 405 4.910/3/2006 955 29.21 12.3 Cloudy 4.0 8.6 9.95 30 6.87 406 5.710/3/2006 955 29.21 12.3 Cloudy 4.3 8.6 10.05 30 6.84 406 5.810/3/2006 955 29.21 12.3 Cloudy 4.6 8.6 10.06 30 6.82 407 6.05/12/2008 1010 29.09 13.9 Pcloudy .3 8.0 11.04 21 7.52 486 .65/12/2008 1010 29.09 13.9 Pcloudy .6 7.4 11.28 20 7.59 485 .55/12/2008 1010 29.09 13.9 Pcloudy .9 7.3 11.20 20 7.59 487 .45/12/2008 1010 29.09 13.9 Pcloudy 1.2 7.2 11.15 20 7.60 488 .35/12/2008 1010 29.09 13.9 Pcloudy 1.5 7.2 11.15 20 7.58 489 .35/12/2008 1010 29.09 13.9 Pcloudy 1.8 7.1 11.09 20 7.57 490 .35/12/2008 1010 29.09 13.9 Pcloudy 2.1 7.0 11.12 20 7.58 490 .35/12/2008 1010 29.09 13.9 Pcloudy 2.4 7.0 11.12 20 7.58 491 .35/12/2008 1010 29.09 13.9 Pcloudy 2.7 6.9 11.07 20 7.57 491 .25/12/2008 1010 29.09 13.9 Pcloudy 3.0 6.9 11.07 20 7.54 493 .25/12/2008 1010 29.09 13.9 Pcloudy 3.4 6.9 4.17 21 8.03 390 --6/2/2008 1020 29.8 18.3 Clear .3 16.3 9.51 27 6.54 539 .46/2/2008 1020 29.8 18.3 Clear .6 16.3 9.54 25 6.62 537 .56/2/2008 1020 29.8 18.3 Clear .9 16.1 9.57 25 6.65 537 .86/2/2008 1020 29.8 18.3 Clear 1.2 16.1 9.56 25 6.67 537 .46/2/2008 1020 29.8 18.3 Clear 1.5 15.9 9.56 25 6.48 544 .46/2/2008 1020 29.8 18.3 Clear 1.8 15.8 9.51 25 6.54 543 .56/2/2008 1020 29.8 18.3 Clear 2.1 15.8 9.45 25 6.61 541 .56/2/2008 1020 29.8 18.3 Clear 2.4 15.7 9.45 25 6.66 541 .46/2/2008 1020 29.8 18.3 Clear 2.7 15.5 9.35 25 6.60 542 .36/2/2008 1020 29.8 18.3 Clear 3.0 15.4 9.28 25 6.61 542 .46/2/2008 1020 29.8 18.3 Clear 3.4 15.4 8.82 25 6.56 469 .1
34 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky condition Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH (standard units) Oxidation reduction potential (mV) Turbidity (NTU) 6/2/2008 1020 29.8 18.3 Clear 3.7 15.1 8.76 26 6.47 431 -- 6/2/2008 1020 29.8 18.3 Clear 4.0 14.3 7.17 26 6.34 397 -- 7/15/2008 943 30.27 22.0 Clear .3 18.6 8.82 31 6.76 412 0 7/15/2008 943 30.27 22.0 Clear .6 18.5 8.86 31 6.80 410 0 7/15/2008 943 30.27 22.0 Clear .9 18.4 8.84 31 6.85 405 0 7/15/2008 943 30.27 22.0 Clear 1.2 18.4 8.82 31 6.81 406 0 7/15/2008 943 30.27 22.0 Clear 1.5 18.4 8.79 31 6.78 407 0 7/15/2008 943 30.27 22.0 Clear 1.8 18.2 8.75 31 6.87 400 .2 7/15/2008 943 30.27 22.0 Clear 2.1 18.1 8.71 31 6.89 398 .1 7/15/2008 943 30.27 22.0 Clear 2.4 18.1 8.68 31 6.84 396 .1 7/15/2008 943 30.27 22.0 Clear 2.7 17.7 8.67 31 6.86 393 0 7/15/2008 943 30.27 22.0 Clear 3.0 16.8 8.55 31 6.72 396 0 7/15/2008 943 30.27 22.0 Clear 3.4 16.4 8.51 32 6.70 397 0 7/15/2008 943 30.27 22.0 Clear 3.7 15.9 8.14 31 6.62 394 0 7/15/2008 943 30.27 22.0 Clear 4.0 15.8 7.97 32 6.54 396 1.1 7/15/2008 943 30.27 22.0 Clear 4.3 15.8 7.65 33 6.54 300 -- 7/15/2008 943 30.27 22.0 Clear 4.6 15.8 5.30 94 6.32 342 -- 8/11/2008 1036 30.86 20.3 Clear .3 21.2 8.63 36 6.87 487 2.5 8/11/2008 1036 30.86 20.3 Clear .6 20.6 8.53 36 6.86 493 2.6 8/11/2008 1036 30.86 20.3 Clear .9 20.3 8.30 36 6.80 498 2.5 8/11/2008 1036 30.86 20.3 Clear 1.2 20.3 8.21 37 6.76 501 2.6 8/11/2008 1036 30.86 20.3 Clear 1.5 20.2 8.10 37 6.68 509 2.4

8/11/2008 1036 30.86 20.3 Clear 1.8 20.1 8.06 36 6.69 509 2.88/11/2008 1036 30.86 20.3 Clear 2.1 20.1 7.96 37 6.71 507 2.98/11/2008 1036 30.86 20.3 Clear 2.4 20.1 7.76 37 6.63 506 3.18/11/2008 1036 30.86 20.3 Clear 2.7 20.0 7.30 37 6.56 503 3.08/11/2008 1036 30.86 20.3 Clear 3.0 20.0 7.30 37 6.53 503 3.18/11/2008 1036 30.86 20.3 Clear 3.4 19.9 7.18 37 6.48 505 --8/11/2008 1036 30.86 20.3 Clear 3.7 19.6 1.16 233 5.90 271 --
Appendixes 1–3 35

Appendix 1. Depth profiles of field properties for Swamp Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts, NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air 

temperature 

(°C)

Sky

condition

Depth 

(m)

Water

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

(standard 

units)

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

8/11/2008 1036 30.86 20.3 Clear 4.0 19.2 0.29 223 5.88 231 --8/11/2008 1036 30.86 20.3 Clear 4.3 19.1 0.24 213 5.91 247 --9/8/2008 940 30.22 10.4 Clear .3 13.8 9.19 40 7.05 538 1.39/8/2008 940 30.22 10.4 Clear .6 13.9 9.19 40 6.99 540 1.39/8/2008 940 30.22 10.4 Clear .9 13.9 9.16 40 9.97 541 1.19/8/2008 940 30.22 10.4 Clear 1.2 13.9 9.17 40 6.95 542 1.19/8/2008 940 30.22 10.4 Clear 1.5 13.9 9.15 40 6.97 541 1.39/8/2008 940 30.22 10.4 Clear 1.8 13.9 9.14 40 6.96 541 1.39/8/2008 940 30.22 10.4 Clear 2.1 13.9 9.13 40 6.97 539 1.39/8/2008 940 30.22 10.4 Clear 2.4 13.9 9.13 40 7.01 535 1.59/8/2008 940 30.22 10.4 Clear 2.7 13.9 9.13 40 7.02 531 1.79/8/2008 940 30.22 10.4 Clear 3.0 13.8 9.11 40 6.98 531 2.89/8/2008 940 30.22 10.4 Clear 3.4 13.8 9.07 40 6.97 527 2.69/8/2008 940 30.22 10.4 Clear 3.7 13.8 8.75 40 6.94 471 3.79/8/2008 940 30.22 10.4 Clear 4.0 13.8 8.79 41 6.84 414 7.09/8/2008 940 30.22 10.4 Clear 4.3 13.9 5.28 119 6.53 345 --10/2/2008 945 30.62 7.6 Cloudy .3 10.4 10.18 38 7.24 446 1.310/2/2008 945 30.62 7.6 Cloudy .6 10.3 10.16 38 7.20 448 1.210/2/2008 945 30.62 7.6 Cloudy .9 10.3 10.13 38 7.20 448 1.810/2/2008 945 30.62 7.6 Cloudy 1.2 10.3 10.14 37 7.16 449 1.410/2/2008 945 30.62 7.6 Cloudy 1.5 10.4 10.14 38 7.13 450 1.410/2/2008 945 30.62 7.6 Cloudy 1.8 10.4 10.15 38 7.12 451 1.310/2/2008 945 30.62 7.6 Cloudy 2.1 10.4 10.13 38 7.10 452 1.310/2/2008 945 30.62 7.6 Cloudy 2.4 10.4 10.13 38 7.11 450 1.310/2/2008 945 30.62 7.6 Cloudy 2.7 10.4 10.12 38 7.11 450 1.310/2/2008 945 30.62 7.6 Cloudy 3.0 10.4 10.13 38 7.12 450 1.410/2/2008 945 30.62 7.6 Cloudy 3.4 10.4 10.15 38 7.13 449 1.810/2/2008 945 30.62 7.6 Cloudy 3.7 10.4 10.13 38 7.14 449 1.710/2/2008 945 30.62 7.6 Cloudy 4.0 10.4 10.12 38 7.16 447 1.9
36 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky conditions Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH Oxidation reduction potential (mV) Turbidity (NTU) 7/16/1997 315 -- -- Pcloudy 0.3 25.6 7.78 40 7.69 276 2.7 7/16/1997 315 -- -- Pcloudy .9 25.5 7.71 40 7.68 274 12.9 7/16/1997 315 -- -- Pcloudy 1.5 25.2 7.87 40 7.70 265 11.4 7/16/1997 315 -- -- Pcloudy 2.1 25.1 7.70 40 7.61 186 11.2 10/10/1997 325 -- 7.22 Clear .3 11.8 9.65 37 7.34 -- 0 10/10/1997 325 -- 7.22 Clear .9 11.7 9.48 37 7.32 -- 2.6 10/10/1997 325 -- 7.22 Clear 1.5 11.4 9.40 37 7.31 -- 7.2 6/26/1998 1040 28.29 23.89 Pcloudy .3 20.5 7.79 40 7.67 -- -- 6/26/1998 1040 28.29 23.89 Pcloudy .9 20.2 7.82 40 7.67 -- .2 6/26/1998 1040 28.29 23.89 Pcloudy 1.5 20.1 7.71 40 7.64 -- .9 6/26/1998 1040 28.29 23.89 Pcloudy 2.1 19.8 7.91 39 7.70 -- .7 6/26/1998 1040 28.29 23.89 Pcloudy 2.7 18.6 8.03 39 7.73 -- .7 6/26/1998 1040 28.29 23.89 Pcloudy 3.4 19.5 2.43 54 6.81 -- -- 7/16/1998 1110 28.48 21.11 Clear .3 23.7 7.32 45 7.63 340 -- 7/16/1998 1110 28.48 21.11 Clear .9 23.6 7.29 45 7.55 343 .2 7/16/1998 1110 28.48 21.11 Clear 1.5 23.5 7.15 45 7.56 343 .7 7/16/1998 1110 28.48 21.11 Clear 2.1 23.5 7.10 45 7.59 341 .2 7/16/1998 1110 28.48 21.11 Clear 2.7 23.3 7.15 45 7.68 338 1.3 7/16/1998 1110 28.48 21.11 Clear 3.4 23.0 3.69 57 6.68 71 --

9/25/1998 1110 28.48 21.11 Clear .3 14.6 9.51 41 7.61 345 1.39/25/1998 1110 28.48 21.11 Clear .9 14.5 8.68 41 7.61 346 09/25/1998 1110 28.48 21.11 Clear 1.5 14.4 8.49 41 7.63 346 19/25/1998 1110 28.48 21.11 Clear 2.1 14.4 8.45 41 7.62 348 1.49/25/1998 1110 28.48 21.11 Clear 2.7 14.3 8.63 41 7.62 300 19/25/1998 1110 28.48 21.11 Clear 3.4 14.5 5.60 61 6.54 246 --
Appendixes 1–3 37

Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air

temperature 

(°C)

Sky

conditions

Depth

(m)

Water 

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

10/21/1998 300 28.65 7.22 Pcloudy 0.3 7.6 10.87 36 7.50 293 010/21/1998 300 28.65 7.22 Pcloudy .6 7.6 10.79 37 7.48 291 .410/21/1998 300 28.65 7.22 Pcloudy .9 7.4 10.81 36 7.49 291 .610/21/1998 300 28.65 7.22 Pcloudy 1.2 7.3 10.91 36 7.48 291 .710/21/1998 300 28.65 7.22 Pcloudy 1.5 7.3 10.91 36 7.48 291 .510/21/1998 300 28.65 7.22 Pcloudy 1.8 7.2 10.89 36 7.51 290 .410/21/1998 300 28.65 7.22 Pcloudy 2.1 7.2 10.86 36 7.52 290 .710/21/1998 300 28.65 7.22 Pcloudy 2.4 7.2 10.85 36 7.52 290 .710/21/1998 300 28.65 7.22 Pcloudy 2.7 7.1 10.94 36 7.52 290 .510/21/1998 300 28.65 7.22 Pcloudy 3.0 6.9 10.86 36 7.52 289 1.110/21/1998 300 28.65 7.22 Pcloudy 3.4 7.0 10.04 38 7.37 253 --5/1/2000 1140 29.15 12.78 Cloudy .3 10.5 11.45 42 7.31 345 --5/1/2000 1140 29.15 12.78 Cloudy .9 10.5 11.01 43 7.20 339 --5/1/2000 1140 29.15 12.78 Cloudy 1.5 10.5 11.06 43 7.18 337 .25/1/2000 1140 29.15 12.78 Cloudy 2.1 10.5 11.05 43 7.15 337 --5/1/2000 1140 29.15 12.78 Cloudy 2.7 10.5 11.04 43 7.13 336 --5/1/2000 1140 29.15 12.78 Cloudy 3.4 10.5 6.00 43 6.61 250 --6/6/2000 1120 29.44 18.33 Clear .3 16.7 9.34 41 7.58 333 --6/6/2000 1120 29.44 18.33 Clear .6 16.7 9.26 41 7.53 333 --6/6/2000 1120 29.44 18.33 Clear .9 16.7 9.20 41 7.50 334 --6/6/2000 1120 29.44 18.33 Clear 1.2 16.6 9.14 41 7.50 334 --6/6/2000 1120 29.44 18.33 Clear 1.5 16.5 9.09 41 7.49 334 --6/6/2000 1120 29.44 18.33 Clear 1.8 16.5 9.08 41 7.48 334 --6/6/2000 1120 29.44 18.33 Clear 2.1 16.2 9.02 41 7.46 335 --6/6/2000 1120 29.44 18.33 Clear 2.4 16.1 9.01 41 7.45 335 --6/6/2000 1120 29.44 18.33 Clear 2.7 16.1 9.00 41 7.40 336 --6/6/2000 1120 29.44 18.33 Clear 3.0 15.9 8.87 41 7.30 338 --
38 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky conditions Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH Oxidation reduction potential (mV) Turbidity (NTU) 6/6/2000 1120 29.44 18.33 Clear 3.4 15.8 8.48 41 7.25 337 -- 6/6/2000 1120 29.44 18.33 Clear 3.7 15.7 8.71 41 7.28 337 -- 6/6/2000 1120 29.44 18.33 Clear 4.0 15.7 8.80 41 7.33 335 -- 6/6/2000 1120 29.44 18.33 Clear 4.3 15.6 7.31 42 6.91 277 -- 6/6/2000 1120 29.44 18.33 Clear 4.6 15.1 6.52 56 6.61 233 -- 7/10/2000 1130 29.35 24.22 Pcloudy .3 21.8 9.40 44 7.79 204 -- 7/10/2000 1130 29.35 24.22 Pcloudy .6 21.7 9.12 44 7.78 207 1.2 7/10/2000 1130 29.35 24.22 Pcloudy .9 21.7 9.00 44 7.80 209 .6 7/10/2000 1130 29.35 24.22 Pcloudy 1.2 21.7 8.95 44 7.80 210 .6 7/10/2000 1130 29.35 24.22 Pcloudy 1.5 21.7 8.93 43 7.81 212 .5 7/10/2000 1130 29.35 24.22 Pcloudy 1.8 21.6 8.96 44 7.80 214 .9 7/10/2000 1130 29.35 24.22 Pcloudy 2.1 21.6 8.87 44 7.80 215 1 7/10/2000 1130 29.35 24.22 Pcloudy 2.4 21.5 8.88 43 7.79 217 .8 7/10/2000 1130 29.35 24.22 Pcloudy 2.7 21.5 8.89 44 7.76 220 .8 7/10/2000 1130 29.35 24.22 Pcloudy 3.0 20.6 8.73 43 7.65 223 .9 7/10/2000 1130 29.35 24.22 Pcloudy 3.4 20.1 8.26 43 7.50 237 1.4 7/10/2000 1130 29.35 24.22 Pcloudy 3.7 19.4 7.06 44 7.11 248 1.9 7/10/2000 1130 29.35 24.22 Pcloudy 4.0 18.3 5.93 45 6.76 255 2.2 7/10/2000 1130 29.35 24.22 Pcloudy 4.3 17.1 2.27 48 6.54 262 3.6 7/10/2000 1130 29.35 24.22 Pcloudy 4.6 17.0 .86 88 6.20 158 -- 8/15/2000 1100 29.62 20.50 Pcloudy .3 21.2 8.15 48 7.13 246 --

8/15/2000 1100 29.62 20.50 Pcloudy .6 21.2 8.21 48 7.15 247 08/15/2000 1100 29.62 20.50 Pcloudy .9 21.1 8.19 48 7.16 248 08/15/2000 1100 29.62 20.50 Pcloudy 1.2 21.1 8.18 48 7.16 249 .88/15/2000 1100 29.62 20.50 Pcloudy 1.5 21.1 8.19 48 7.17 250 2.38/15/2000 1100 29.62 20.50 Pcloudy 1.8 21.1 8.05 48 7.17 252 1.18/15/2000 1100 29.62 20.50 Pcloudy 2.1 21.1 8.15 48 7.17 252 1.7
Appendixes 1–3 39

Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air

temperature 

(°C)

Sky

conditions

Depth

(m)

Water 

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

8/15/2000 1100 29.62 20.50 Pcloudy 2.4 21.1 8.10 48 7.17 253 1.18/15/2000 1100 29.62 20.50 Pcloudy 2.7 21.0 7.94 48 7.16 255 1.48/15/2000 1100 29.62 20.50 Pcloudy 3.0 20.9 7.83 48 7.11 258 1.38/15/2000 1100 29.62 20.50 Pcloudy 3.4 20.9 7.91 48 7.09 259 1.78/15/2000 1100 29.62 20.50 Pcloudy 3.7 20.9 7.90 48 7.08 260 1.48/15/2000 1100 29.62 20.50 Pcloudy 4.0 20.8 7.27 48 6.99 249 1.98/15/2000 1100 29.62 20.50 Pcloudy 4.3 20.6 5.86 49 6.50 176 8.39/11/2000 1140 28.67 26.39 Pcloudy .3 16.7 9.30 43 7.56 270 --9/11/2000 1140 28.67 26.39 Pcloudy .6 16.6 9.41 43 7.55 270 1.19/11/2000 1140 28.67 26.39 Pcloudy .9 16.5 9.48 43 7.53 269 1.89/11/2000 1140 28.67 26.39 Pcloudy 1.2 16.5 9.41 43 7.53 269 1.49/11/2000 1140 28.67 26.39 Pcloudy 1.5 16.4 9.48 43 7.54 268 1.59/11/2000 1140 28.67 26.39 Pcloudy 1.8 16.4 9.44 43 7.55 267 1.29/11/2000 1140 28.67 26.39 Pcloudy 2.1 16.3 9.43 43 7.52 269 1.39/11/2000 1140 28.67 26.39 Pcloudy 2.4 16.2 9.32 43 7.48 269 1.59/11/2000 1140 28.67 26.39 Pcloudy 2.7 16.2 9.26 42 7.46 270 1.49/11/2000 1140 28.67 26.39 Pcloudy 3.0 16.1 9.20 42 7.45 269 1.69/11/2000 1140 28.67 26.39 Pcloudy 3.4 16.1 9.13 43 7.43 270 1.59/11/2000 1140 28.67 26.39 Pcloudy 3.7 16.1 9.11 43 7.37 272 1.79/11/2000 1140 28.67 26.39 Pcloudy 4.0 16.0 8.29 44 7.09 203 --10/3/2000 1115 28.88 12.50 Clear .3 12.5 10.53 43 7.49 317 --10/3/2000 1115 28.88 12.50 Clear .6 12.5 10.44 43 7.51 316 010/3/2000 1115 28.88 12.50 Clear .9 12.5 10.47 42 7.52 317 010/3/2000 1115 28.88 12.50 Clear 1.2 12.5 10.41 43 7.54 317 .310/3/2000 1115 28.88 12.50 Clear 1.5 12.5 10.39 43 7.54 318 2.310/3/2000 1115 28.88 12.50 Clear 1.8 12.5 10.34 42 7.58 317 .910/3/2000 1115 28.88 12.50 Clear 2.1 12.5 10.37 43 7.56 318 1.2
40 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky conditions Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH Oxidation reduction potential (mV) Turbidity (NTU) 10/3/2000 1115 28.88 12.50 Clear 2.4 12.5 10.30 43 7.58 318 1.3 10/3/2000 1115 28.88 12.50 Clear 2.7 12.5 10.32 43 7.57 319 1.1 10/3/2000 1115 28.88 12.50 Clear 3.0 12.4 10.27 42 7.58 319 1.3 10/3/2000 1115 28.88 12.50 Clear 3.4 12.4 10.23 42 7.57 320 -- 10/3/2000 1115 28.88 12.50 Clear 3.7 12.4 10.20 42 7.55 321 1.5 10/3/2000 1115 28.88 12.50 Clear 4.0 12.4 7.92 42 7.23 204 -- 5/13/2002 1100 29.12 17.50 Pcloudy .3 8.4 12.00 36 7.67 267 3.6 5/13/2002 1100 29.12 17.50 Pcloudy .6 8.4 12.01 36 7.65 268 3.0 5/13/2002 1100 29.12 17.50 Pcloudy .9 8.1 12.06 36 7.64 268 3.1 5/13/2002 1100 29.12 17.50 Pcloudy 1.2 7.9 12.13 36 7.63 269 3.0 5/13/2002 1100 29.12 17.50 Pcloudy 1.5 7.9 12.08 36 7.61 270 3.0 5/13/2002 1100 29.12 17.50 Pcloudy 1.8 7.8 12.06 36 7.59 271 2.7 5/13/2002 1100 29.12 17.50 Pcloudy 2.1 7.8 12.02 36 7.57 272 2.9 5/13/2002 1100 29.12 17.50 Pcloudy 2.4 7.8 12.05 36 7.58 271 6.4 5/13/2002 1100 29.12 17.50 Pcloudy 2.7 7.8 11.19 39 7.35 150 -- 5/13/2002 1100 29.12 17.50 Pcloudy 3.0 7.4 9.13 43 7.32 120 -- 5/13/2002 1100 29.12 17.50 Pcloudy 3.4 7.8 11.19 38 7.34 271 6.4 5/13/2002 1100 29.12 17.50 Pcloudy 3.7 7.7 11.18 39 7.36 271 6.3 5/13/2002 1100 29.12 17.50 Pcloudy 4.0 7.7 11.19 38 7.35 271 6.3 5/13/2002 1100 29.12 17.50 Pcloudy 4.3 7.7 11.20 39 7.36 271 6.3 6/17/2002 1122 29.06 24.89 Pcloudy .3 18.5 8.99 40 7.34 264 8.0

6/17/2002 1122 29.06 24.89 Pcloudy .6 18.4 8.93 40 7.34 265 8.26/17/2002 1122 29.06 24.89 Pcloudy .9 18.1 8.89 40 7.34 265 8.06/17/2002 1122 29.06 24.89 Pcloudy 1.2 18.0 8.90 40 7.35 266 8.26/17/2002 1122 29.06 24.89 Pcloudy 1.5 18.0 8.89 40 7.36 266 8.36/17/2002 1122 29.06 24.89 Pcloudy 1.8 17.9 8.95 40 7.33 268 8.26/17/2002 1122 29.06 24.89 Pcloudy 2.1 17.9 8.88 40 7.32 269 8.3
Appendixes 1–3 41

Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air

temperature 

(°C)

Sky

conditions

Depth

(m)

Water 

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

6/17/2002 1122 29.06 24.89 Pcloudy 2.4 17.8 8.90 40 7.35 269 8.16/17/2002 1122 29.06 24.89 Pcloudy 2.7 17.7 8.95 39 7.39 267 10.46/17/2002 1122 29.06 24.89 Pcloudy 3.0 17.5 8.70 40 7.32 162 --7/17/2002 1024 29.15 27.72 Pcloudy .3 25.6 7.31 46 7.43 331 8.77/17/2002 1024 29.15 27.72 Pcloudy .6 25.6 7.38 46 7.39 329 8.57/17/2002 1024 29.15 27.72 Pcloudy .9 25.6 7.37 46 7.38 329 8.27/17/2002 1024 29.15 27.72 Pcloudy 1.2 25.5 7.37 46 7.37 328 8.77/17/2002 1024 29.15 27.72 Pcloudy 1.5 25.4 7.24 46 7.30 331 8.67/17/2002 1024 29.15 27.72 Pcloudy 1.8 25.4 7.10 47 7.23 331 8.77/17/2002 1024 29.15 27.72 Pcloudy 2.1 25.4 7.05 47 7.22 330 8.67/17/2002 1024 29.15 27.72 Pcloudy 2.4 25.3 7.03 47 7.16 330 9.07/17/2002 1024 29.15 27.72 Pcloudy 2.7 25.3 6.93 47 7.13 296 --8/13/2002 315 28.63 22.22 Pcloudy .3 22.2 8.71 46 7.74 259 9.38/13/2002 315 28.63 22.22 Pcloudy .6 22.2 8.73 46 7.73 260 9.18/13/2002 315 28.63 22.22 Pcloudy .9 22.2 8.75 45 7.72 262 8.78/13/2002 315 28.63 22.22 Pcloudy 1.2 22.1 8.71 46 7.72 262 8.98/13/2002 315 28.63 22.22 Pcloudy 1.5 22.1 8.75 46 7.73 264 8.98/13/2002 315 28.63 22.22 Pcloudy 1.8 22.1 8.71 46 7.76 264 9.48/13/2002 315 28.63 22.22 Pcloudy 2.1 22.0 8.70 45 7.83 2439/10/2002 1125 29.15 18.33 Pcloudy .3 21.1 7.68 45 7.14 364 9.89/10/2002 1125 29.15 18.33 Pcloudy .6 21.1 7.59 45 7.10 361 9.59/10/2002 1125 29.15 18.33 Pcloudy .9 21.1 7.66 45 7.07 361 9.69/10/2002 1125 29.15 18.33 Pcloudy 1.2 21.1 7.60 45 7.10 358 9.59/10/2002 1125 29.15 18.33 Pcloudy 1.5 21.1 7.63 45 7.08 359 9.49/10/2002 1125 29.15 18.33 Pcloudy 1.8 21.1 7.69 45 7.06 360 9.59/10/2002 1125 29.15 18.33 Pcloudy 2.1 21.1 7.77 45 7.06 359 9.7
42 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky conditions Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH Oxidation reduction potential (mV) Turbidity (NTU) 9/10/2002 1125 29.15 18.33 Pcloudy 2.4 21.0 7.82 45 7.06 359 9.5 9/10/2002 1125 29.15 18.33 Pcloudy 2.7 21.0 7.70 45 7.06 359 9.6 9/10/2002 1125 29.15 18.33 Pcloudy 3.0 21.0 7.73 45 7.07 357 9.5 9/10/2002 1125 29.15 18.33 Pcloudy 3.4 21.0 7.70 45 7.07 358 9.5 9/10/2002 1125 29.15 18.33 Pcloudy 3.7 21.0 7.18 50 6.98 195 -- 10/2/2002 1215 29.44 17.22 Pcloudy .3 12.2 9.13 41 7.97 277 9.9 10/2/2002 1215 29.44 17.22 Pcloudy .6 12.1 9.02 41 7.86 282 9.8 10/2/2002 1215 29.44 17.22 Pcloudy .9 12.1 8.98 41 7.85 283 10.0 10/2/2002 1215 29.44 17.22 Pcloudy 1.2 12.1 8.94 41 7.74 288 9.7 10/2/2002 1215 29.44 17.22 Pcloudy 1.5 12.1 8.95 41 7.72 291 9.9 10/2/2002 1215 29.44 17.22 Pcloudy 1.8 12.1 9.01 41 7.67 294 9.9 10/2/2002 1215 29.44 17.22 Pcloudy 2.1 12.1 8.99 41 7.66 295 9.7 10/2/2002 1215 29.44 17.22 Pcloudy 2.4 120.5 8.98 41 7.64 297 9.6 10/2/2002 1215 29.44 17.22 Pcloudy 2.7 120.5 8.94 41 7.62 298 9.6 10/2/2002 1215 29.44 17.22 Pcloudy 3.0 12.0 8.94 41 7.61 299 9.8 10/2/2002 1215 29.44 17.22 Pcloudy 3.4 12.1 8.97 41 7.58 302 9.8 10/2/2002 1215 29.44 17.22 Pcloudy 3.7 12.0 8.96 41 7.57 302 9.7 10/2/2002 1215 29.44 17.22 Pcloudy 4.0 11.9 8.95 41 7.57 303 9.7 5/24/2004 1127 29.97 13.78 Clear .3 10.9 10.84 47 7.16 309 8.8 5/24/2004 1127 29.97 13.78 Clear .6 10.8 10.76 47 7.12 309 9.0 5/24/2004 1127 29.97 13.78 Clear .9 10.8 10.70 47 7.13 309 8.7

5/24/2004 1127 29.97 13.78 Clear 1.2 10.6 10.64 47 7.10 309 8.25/24/2004 1127 29.97 13.78 Clear 1.5 10.6 10.76 47 7.10 308 8.35/24/2004 1127 29.97 13.78 Clear 1.8 10.5 10.75 47 7.10 307 8.65/24/2004 1127 29.97 13.78 Clear 2.1 10.5 10.74 47 7.09 307 8.55/24/2004 1127 29.97 13.78 Clear 2.4 10.6 10.62 48 6.75 150 --5/24/2004 1127 29.97 13.78 Clear 2.7 10.5 8.43 70 6.42 57 --5/24/2004 1127 29.97 13.78 Clear 3.0 10.4 4.12 53 6.44 75 --
Appendixes 1–3 43

Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air

temperature 

(°C)

Sky

conditions

Depth

(m)

Water 

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

6/7/2004 1111 28.88 14.89 Cloudy 0.3 15.9 10.58 44 7.34 282 8.46/7/2004 1111 28.88 14.89 Cloudy .6 15.9 10.58 44 7.33 278 8.36/7/2004 1111 28.88 14.89 Cloudy .9 15.9 10.61 44 7.32 279 8.56/7/2004 1111 28.88 14.89 Cloudy 1.2 15.9 10.55 44 7.31 279 8.26/7/2004 1111 28.88 14.89 Cloudy 1.5 15.8 10.58 44 7.30 278 8.56/7/2004 1111 28.88 14.89 Cloudy 1.8 15.7 10.57 44 7.31 278 8.76/7/2004 1111 28.88 14.89 Cloudy 2.1 15.5 10.54 44 7.30 278 9.06/7/2004 1111 28.88 14.89 Cloudy 2.4 15.4 10.68 44 7.29 278 8.66/7/2004 1111 28.88 14.89 Cloudy 2.7 15.7 9.58 44 7.16 130 --6/7/2004 1111 28.88 14.89 Cloudy 3.0 15.6 8.86 56 6.95 90 --7/12/2004 1027 29.09 28.78 Clear .3 21.6 9.10 44 8.04 292 8.67/12/2004 1027 29.09 28.78 Clear .6 21.3 9.18 44 8.00 293 8.17/12/2004 1027 29.09 28.78 Clear .9 21.2 9.25 44 8.04 290 8.37/12/2004 1027 29.09 28.78 Clear 1.2 21.1 9.31 44 8.12 283 8.67/12/2004 1027 29.09 28.78 Clear 1.5 21.0 9.30 45 8.08 282 8.57/12/2004 1027 29.09 28.78 Clear 1.8 20.9 9.22 44 8.17 283 8.87/12/2004 1027 29.09 28.78 Clear 2.1 20.8 9.20 44 8.03 284 8.57/12/2004 1027 29.09 28.78 Clear 2.4 20.2 9.53 44 8.43 269 8.97/12/2004 1027 29.09 28.78 Clear 2.7 19.7 9.38 44 8.05 163 --7/12/2004 1027 29.09 28.78 Clear 3.0 18.4 2.90 68 6.37 119 --8/2/2004 340 29.06 26.78 Pcloudy .3 23.1 9.16 46 8.36 295 30.78/2/2004 340 29.06 26.78 Pcloudy .6 22.9 9.21 46 8.37 296 29.68/2/2004 340 29.06 26.78 Pcloudy .9 22.7 9.29 46 8.39 296 30.48/2/2004 340 29.06 26.78 Pcloudy 1.2 22.4 9.27 46 8.41 297 30.38/2/2004 340 29.06 26.78 Pcloudy 1.5 22.1 9.42 46 8.41 298 30.78/2/2004 340 29.06 26.78 Pcloudy 1.8 21.9 9.46 46 8.44 299 30.68/2/2004 340 29.06 26.78 Pcloudy 2.1 21.9 9.46 46 8.46 299 30.0
44 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky conditions Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH Oxidation reduction potential (mV) Turbidity (NTU) 8/2/2004 340 29.06 26.78 Pcloudy 2.4 21.9 9.51 46 8.46 299 33.0 8/2/2004 340 29.06 26.78 Pcloudy 2.7 21.9 8.57 50 8.18 287 -- 9/7/2004 1041 30.05 16.61 Pcloudy .3 18.1 10.43 46 7.67 264 .8 9/7/2004 1041 30.05 16.61 Pcloudy .6 18.1 10.13 46 7.64 262 .8 9/7/2004 1041 30.05 16.61 Pcloudy .9 18.0 9.88 46 7.64 257 .9 9/7/2004 1041 30.05 16.61 Pcloudy 1.2 18.0 9.89 46 7.64 255 .9 9/7/2004 1041 30.05 16.61 Pcloudy 1.5 18.0 9.99 46 7.65 253 1.0 9/7/2004 1041 30.05 16.61 Pcloudy 1.8 18.0 9.84 46 7.66 252 1.0 9/7/2004 1041 30.05 16.61 Pcloudy 2.1 18.0 9.95 46 7.74 249 1.0 9/7/2004 1041 30.05 16.61 Pcloudy 2.4 18.0 9.93 46 7.78 247 1.4 9/7/2004 1041 30.05 16.61 Pcloudy 2.7 18.0 9.85 46 7.73 220 25.5 9/7/2004 1041 30.05 16.61 Pcloudy 3.0 18.0 9.74 57 6.99 59 -- 10/6/2004 300 28.37 20.28 Clear .3 10.5 11.30 44 7.73 266 0 10/6/2004 300 28.37 20.28 Clear .6 10.5 11.34 44 7.74 264 0 10/6/2004 300 28.37 20.28 Clear .9 10.4 11.19 44 7.74 262 0 10/6/2004 300 28.37 20.28 Clear 1.2 10.3 11.27 44 7.74 260 0 10/6/2004 300 28.37 20.28 Clear 1.5 10.3 11.29 44 7.76 259 0 10/6/2004 300 28.37 20.28 Clear 1.8 10.3 11.26 44 7.78 257 0 10/6/2004 300 28.37 20.28 Clear 2.1 10.2 11.27 44 7.79 256 0 10/6/2004 300 28.37 20.28 Clear 2.4 9.4 11.27 43 7.71 213 9.5 10/6/2004 300 28.37 20.28 Clear 2.7 9.5 11.26 43 7.78 200 23.3

10/6/2004 300 28.37 20.28 Clear 3.0 9.8 9.62 51 7.56 111 --5/15/2006 1030 29.26 14.11 Rain .3 9.3 11.96 38 7.48 338 05/15/2006 1030 29.26 14.11 Rain .6 9.3 12.01 37 7.47 341 05/15/2006 1030 29.26 14.11 Rain .9 9.3 11.92 38 7.50 341 05/15/2006 1030 29.26 14.11 Rain 1.2 9.3 11.94 38 7.52 341 0
Appendixes 1–3 45

Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air

temperature 

(°C)

Sky

conditions

Depth

(m)

Water 

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

5/15/2006 1030 29.26 14.11 Rain 1.5 9.2 11.96 38 7.54 341 05/15/2006 1030 29.26 14.11 Rain 1.8 9.1 12.01 38 7.55 341 05/15/2006 1030 29.26 14.11 Rain 2.1 9.1 11.96 38 7.54 342 05/15/2006 1030 29.26 14.11 Rain 2.4 8.9 11.97 37 7.56 343 05/15/2006 1030 29.26 14.11 Rain 2.7 8.9 11.90 38 7.56 343 05/15/2006 1030 29.26 14.11 Rain 3.0 8.8 11.85 38 7.56 344 05/15/2006 1030 29.26 14.11 Rain 3.4 8.8 11.85 38 7.55 345 05/15/2006 1030 29.26 14.11 Rain 3.7 8.7 11.88 38 7.56 346 05/15/2006 1030 29.26 14.11 Rain 4.0 8.6 11.89 38 7.57 346 05/15/2006 1030 29.26 14.11 Rain 4.3 8.6 11.84 38 7.58 350 05/15/2006 1030 29.26 14.11 Rain 4.6 8.5 11.87 38 7.57 348 05/15/2006 1030 29.26 14.11 Rain 4.9 8.5 11.89 38 7.57 351 05/15/2006 1030 29.26 14.11 Rain 5.2 8.4 11.75 38 7.56 351 05/15/2006 1030 29.26 14.11 Rain 5.5 8.4 11.68 38 7.56 352 05/15/2006 1030 29.26 14.11 Rain 5.8 8.4 11.64 38 7.56 348 --6/7/2006 1100 29.09 23.94 Clear .3 20.9 9.08 38 7.91 263 06/7/2006 1100 29.09 23.94 Clear .6 20.9 9.17 38 7.90 263 06/7/2006 1100 29.09 23.94 Clear .9 20.9 9.19 38 7.93 262 06/7/2006 1100 29.09 23.94 Clear 1.2 20.8 9.13 38 7.95 261 06/7/2006 1100 29.09 23.94 Clear 1.5 20.8 9.19 38 7.98 259 06/7/2006 1100 29.09 23.94 Clear 1.8 20.8 9.07 38 8.00 258 06/7/2006 1100 29.09 23.94 Clear 2.1 20.5 9.02 38 8.00 258 06/7/2006 1100 29.09 23.94 Clear 2.4 20.2 9.03 38 7.98 258 06/7/2006 1100 29.09 23.94 Clear 2.7 20.1 8.98 38 7.95 259 06/7/2006 1100 29.09 23.94 Clear 3.0 19.8 9.13 38 7.92 261 06/7/2006 1100 29.09 23.94 Clear 3.4 19.0 10.45 37 8.01 256 06/7/2006 1100 29.09 23.94 Clear 3.7 17.0 11.34 37 8.09 255 06/7/2006 1100 29.09 23.94 Clear 4.0 16.1 11.23 37 8.04 258 0
46 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky conditions Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH Oxidation reduction potential (mV) Turbidity (NTU) 6/7/2006 1100 29.09 23.94 Clear 4.3 15.4 11.47 38 8.06 257 0 6/7/2006 1100 29.09 23.94 Clear 4.6 14.9 11.49 38 8.10 256 0 6/7/2006 1100 29.09 23.94 Clear 4.9 14.2 11.33 39 8.07 258 1.4 6/7/2006 1100 29.09 23.94 Clear 5.2 13.7 10.46 40 7.92 266 2.6 6/7/2006 1100 29.09 23.94 Clear 5.5 13.5 7.30 63 7.03 191 -- 6/7/2006 1100 29.09 23.94 Clear 5.8 13.4 3.56 65 6.76 200 -- 7/10/2006 1040 29.21 18.61 Clear .3 22.1 8.67 41 7.37 248 2.0 7/10/2006 1040 29.21 18.61 Clear .6 21.9 8.62 40 7.39 251 2.1 7/10/2006 1040 29.21 18.61 Clear .9 21.8 8.68 41 7.41 252 2.0 7/10/2006 1040 29.21 18.61 Clear 1.2 21.7 8.70 41 7.47 251 2.1 7/10/2006 1040 29.21 18.61 Clear 1.5 21.6 8.57 41 7.48 251 1.9 7/10/2006 1040 29.21 18.61 Clear 1.8 21.6 8.57 41 7.48 251 1.8 7/10/2006 1040 29.21 18.61 Clear 2.1 21.6 8.47 41 7.49 252 1.9 7/10/2006 1040 29.21 18.61 Clear 2.4 21.5 8.57 41 7.49 253 2.0 7/10/2006 1040 29.21 18.61 Clear 2.7 51.5 8.58 41 7.49 253 2.0 7/10/2006 1040 29.21 18.61 Clear 3.0 51.4 8.61 41 7.53 253 1.9 7/10/2006 1040 29.21 18.61 Clear 3.4 21.3 8.68 41 7.51 254 2.0 7/10/2006 1040 29.21 18.61 Clear 3.7 21.3 8.50 41 7.50 255 1.9 7/10/2006 1040 29.21 18.61 Clear 4.0 21.3 8.52 41 7.49 256 1.9 7/10/2006 1040 29.21 18.61 Clear 4.3 21.3 8.48 41 7.48 257 1.8 7/10/2006 1040 29.21 18.61 Clear 4.6 21.3 8.48 41 7.47 258 1.9 7/10/2006 1040 29.21 18.61 Clear 4.9 21.3 8.45 41 7.46 259 1.8

7/10/2006 1040 29.21 18.61 Clear 5.2 21.2 2.75 67 6.59 184 --7/10/2006 1040 29.21 18.61 Clear 5.5 20.9 1.54 78 6.28 188 --8/15/2006 1118 29.68 18.44 Clear .3 20.4 7.49 43 7.49 322 1.48/15/2006 1118 29.68 18.44 Clear .6 20.4 7.51 43 7.51 322 1.38/15/2006 1118 29.68 18.44 Clear .9 20.4 7.52 42 7.52 322 1.3
Appendixes 1–3 47

Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air

temperature 

(°C)

Sky

conditions

Depth

(m)

Water 

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

8/15/2006 1118 29.68 18.44 Clear 1.2 20.4 7.55 43 7.55 321 1.48/15/2006 1118 29.68 18.44 Clear 1.5 20.4 7.58 42 7.58 320 1.58/15/2006 1118 29.68 18.44 Clear 1.8 20.3 7.61 42 7.61 319 1.58/15/2006 1118 29.68 18.44 Clear 2.1 20.3 7.63 43 7.63 319 1.48/15/2006 1118 29.68 18.44 Clear 2.4 20.3 7.63 42 7.63 319 1.68/15/2006 1118 29.68 18.44 Clear 2.7 20.2 7.64 42 7.64 318 1.58/15/2006 1118 29.68 18.44 Clear 3.0 20.2 7.63 43 7.63 319 1.48/15/2006 1118 29.68 18.44 Clear 3.4 20.1 7.63 43 7.63 319 1.58/15/2006 1118 29.68 18.44 Clear 3.7 20.1 7.62 43 7.62 320 1.48/15/2006 1118 29.68 18.44 Clear 4.0 20.1 7.61 42 7.61 321 1.38/15/2006 1118 29.68 18.44 Clear 4.3 20.1 8.98 42 7.62 321 1.68/15/2006 1118 29.68 18.44 Clear 4.6 20.1 7.42 43 7.28 307 5.48/15/2006 1118 29.68 18.44 Clear 4.9 20.1 6.52 62 6.78 299 --9/11/2006 1132 29.41 16.22 Pcloudy .3 17.0 9.58 42 7.66 282 09/11/2006 1132 29.41 16.22 Pcloudy .6 17.0 9.34 42 7.67 283 .39/11/2006 1132 29.41 16.22 Pcloudy .9 17.0 9.36 42 7.66 285 .29/11/2006 1132 29.41 16.22 Pcloudy 1.2 17.0 9.46 42 7.66 287 .39/11/2006 1132 29.41 16.22 Pcloudy 1.5 16.9 9.43 42 7.66 287 .49/11/2006 1132 29.41 16.22 Pcloudy 1.8 16.8 9.35 42 7.64 289 09/11/2006 1132 29.41 16.22 Pcloudy 2.1 16.7 9.23 42 7.64 289 .29/11/2006 1132 29.41 16.22 Pcloudy 2.4 16.6 9.29 42 7.63 290 09/11/2006 1132 29.41 16.22 Pcloudy 2.7 16.6 9.26 42 7.63 292 .29/11/2006 1132 29.41 16.22 Pcloudy 3.0 16.6 9.23 42 7.62 292 09/11/2006 1132 29.41 16.22 Pcloudy 3.4 16.5 9.14 42 7.59 295 09/11/2006 1132 29.41 16.22 Pcloudy 3.7 16.5 9.18 42 7.58 295 09/11/2006 1132 29.41 16.22 Pcloudy 4.0 16.4 9.26 42 7.58 296 .19/11/2006 1132 29.41 16.22 Pcloudy 4.3 16.4 9.23 42 7.58 296 09/11/2006 1132 29.41 16.22 Pcloudy 4.6 16.5 4.24 51 7.04 236 --
48 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky conditions Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH Oxidation reduction potential (mV) Turbidity (NTU) 10/3/2006 1100 29.18 13.00 Cloudy 0.3 11.4 11.05 40 7.51 347 1.3 10/3/2006 1100 29.18 13.00 Cloudy .6 11.4 10.98 40 7.50 347 1.0 10/3/2006 1100 29.18 13.00 Cloudy .9 11.4 10.99 40 7.49 348 2.0 10/3/2006 1100 29.18 13.00 Cloudy 1.2 11.4 10.95 40 7.48 349 1.6 10/3/2006 1100 29.18 13.00 Cloudy 1.5 11.4 10.98 40 7.46 350 1.1 10/3/2006 1100 29.18 13.00 Cloudy 1.8 11.4 10.90 40 7.45 351 1.3 10/3/2006 1100 29.18 13.00 Cloudy 2.1 11.4 10.88 40 7.43 351 1.7 10/3/2006 1100 29.18 13.00 Cloudy 2.4 11.3 10.85 40 7.42 353 1.6 10/3/2006 1100 29.18 13.00 Cloudy 2.7 10.9 10.84 40 7.42 354 1.2 10/3/2006 1100 29.18 13.00 Cloudy 3.0 10.8 10.88 40 7.39 355 1.2 10/3/2006 1100 29.18 13.00 Cloudy 3.4 10.8 10.83 40 7.39 355 1.2 10/3/2006 1100 29.18 13.00 Cloudy 3.7 10.7 10.85 40 7.39 356 1.2 10/3/2006 1100 29.18 13.00 Cloudy 4.0 10.7 10.85 40 7.37 357 1.4 10/3/2006 1100 29.18 13.00 Cloudy 4.3 10.7 10.91 40 7.36 357 1.2 10/3/2006 1100 29.18 13.00 Cloudy 4.6 10.7 10.84 40 7.35 358 1.0 10/3/2006 1100 29.18 13.00 Cloudy 4.9 10.6 10.86 40 7.35 358 .9 10/3/2006 1100 29.18 13.00 Cloudy 5.2 10.6 10.48 40 7.30 361 1.5 10/3/2006 1100 29.18 13.00 Cloudy 5.5 10.8 4.18 51 6.62 365 -- 5/12/2008 1120 29.09 11.11 Cloudy .3 7.8 9.61 42 8.10 420 0 5/12/2008 1120 29.09 11.11 Cloudy .6 7.8 9.51 42 8.04 421 0 5/12/2008 1120 29.09 11.11 Cloudy .9 7.8 9.40 42 7.91 425 0

5/12/2008 1120 29.09 11.11 Cloudy 1.2 7.8 9.38 42 7.91 425 .15/12/2008 1120 29.09 11.11 Cloudy 1.5 7.8 9.38 42 7.89 426 05/12/2008 1120 29.09 11.11 Cloudy 1.8 7.7 9.39 42 7.83 428 05/12/2008 1120 29.09 11.11 Cloudy 2.1 7.5 9.36 42 7.90 427 .15/12/2008 1120 29.09 11.11 Cloudy 2.4 7.4 9.36 42 7.88 428 .15/12/2008 1120 29.09 11.11 Cloudy 2.7 7.3 9.35 42 7.87 428 .1
Appendixes 1–3 49

Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air

temperature 

(°C)

Sky

conditions

Depth

(m)

Water 

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

5/12/2008 1120 29.09 11.11 Cloudy 3.0 7.3 9.34 42 7.85 428 0.25/12/2008 1120 29.09 11.11 Cloudy 3.4 7.2 9.23 42 7.86 430 .25/12/2008 1120 29.09 11.11 Cloudy 3.7 7.1 9.23 42 7.82 431 .15/12/2008 1120 29.09 11.11 Cloudy 4.0 7.1 9.20 42 7.83 431 .25/12/2008 1120 29.09 11.11 Cloudy 4.3 7.1 9.15 42 7.82 430 .35/12/2008 1120 29.09 11.11 Cloudy 4.6 7.0 9.19 42 7.83 430 .45/12/2008 1120 29.09 11.11 Cloudy 4.9 7.0 9.23 42 7.80 431 .45/12/2008 1120 29.09 11.11 Cloudy 5.2 6.6 5.15 53 7.54 422 --6/2/2008 1130 29.8 20.56 Clear .3 16.2 10.49 41 7.41 486 06/2/2008 1130 29.8 20.56 Clear .6 16.2 10.49 41 7.50 486 06/2/2008 1130 29.8 20.56 Clear .9 16.1 10.48 41 7.57 484 06/2/2008 1130 29.8 20.56 Clear 1.2 16.1 10.45 41 7.55 485 06/2/2008 1130 29.8 20.56 Clear 1.5 16.1 10.44 41 7.54 486 06/2/2008 1130 29.8 20.56 Clear 1.8 15.6 10.52 41 7.55 488 06/2/2008 1130 29.8 20.56 Clear 2.1 15.4 10.59 41 7.60 486 06/2/2008 1130 29.8 20.56 Clear 2.4 15.2 10.63 41 7.59 487 06/2/2008 1130 29.8 20.56 Clear 2.7 15.0 10.65 41 7.57 487 06/2/2008 1130 29.8 20.56 Clear 3.0 15.0 10.69 41 7.62 485 06/2/2008 1130 29.8 20.56 Clear 3.4 14.8 10.77 41 7.62 484 06/2/2008 1130 29.8 20.56 Clear 3.7 14.7 10.84 41 7.64 483 06/2/2008 1130 29.8 20.56 Clear 4.0 14.4 10.71 41 7.53 484 06/2/2008 1130 29.8 20.56 Clear 4.3 14.0 10.36 42 7.36 489 06/2/2008 1130 29.8 20.56 Clear 4.6 13.7 10.21 41 7.26 491 06/2/2008 1130 29.8 20.56 Clear 4.9 13.5 9.85 41 7.12 490 06/2/2008 1130 29.8 20.56 Clear 5.2 12.7 9.11 41 6.99 421 .26/2/2008 1130 29.8 20.56 Clear 5.5 12.5 6.42 44 6.50 366 --
50 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky conditions Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH Oxidation reduction potential (mV) Turbidity (NTU) 7/14/2008 954 29.53 19.50 Pcloudy 0.3 18.7 8.26 42 7.50 407 0 7/14/2008 954 29.53 19.50 Pcloudy .6 18.7 8.38 42 7.52 412 0 7/14/2008 954 29.53 19.50 Pcloudy .9 18.7 8.41 42 7.48 416 0 7/14/2008 954 29.53 19.50 Pcloudy 1.2 18.7 8.40 42 7.40 422 0 7/14/2008 954 29.53 19.50 Pcloudy 1.5 18.7 8.40 43 7.42 422 0 7/14/2008 954 29.53 19.50 Pcloudy 1.8 18.6 8.41 42 7.46 421 0 7/14/2008 954 29.53 19.50 Pcloudy 2.1 18.4 8.34 42 7.37 426 0 7/14/2008 954 29.53 19.50 Pcloudy 2.4 18.4 8.33 42 7.38 428 0 7/14/2008 954 29.53 19.50 Pcloudy 2.7 18.3 8.32 43 7.37 427 0 7/14/2008 954 29.53 19.50 Pcloudy 3.0 18.3 8.31 43 7.40 427 0 7/14/2008 954 29.53 19.50 Pcloudy 3.4 18.3 8.31 42 7.37 428 0 7/14/2008 954 29.53 19.50 Pcloudy 3.7 18.3 8.32 43 7.36 429 0 7/14/2008 954 29.53 19.50 Pcloudy 4.0 18.2 8.31 42 7.39 428 0 7/14/2008 954 29.53 19.50 Pcloudy 4.3 18.1 8.38 43 7.32 437 0 7/14/2008 954 29.53 19.50 Pcloudy 4.6 18.0 8.40 42 7.37 435 0 7/14/2008 954 29.53 19.50 Pcloudy 4.9 17.9 8.43 42 7.41 434 0 7/14/2008 954 29.53 19.50 Pcloudy 5.2 17.8 8.47 43 7.37 435 0 7/14/2008 954 29.53 19.50 Pcloudy 5.5 17.8 8.44 42 7.36 412 -- 7/14/2008 954 29.53 19.50 Pcloudy 5.8 17.6 3.34 95 6.39 299 -- 8/11/2008 1218 30.3 20.11 Clear .3 23.3 8.50 42 7.22 252 1.4 8/11/2008 1218 30.3 20.11 Clear .6 22.3 8.58 42 7.32 265 1.5 8/11/2008 1218 30.3 20.11 Clear .9 22.1 8.57 42 7.37 275 1.4

8/11/2008 1218 30.3 20.11 Clear 1.2 22.0 6.59 42 7.39 281 1.68/11/2008 1218 30.3 20.11 Clear 1.5 22.0 8.72 42 7.46 285 1.78/11/2008 1218 30.3 20.11 Clear 1.8 22.0 8.76 42 7.45 292 1.78/11/2008 1218 30.3 20.11 Clear 2.1 21.9 8.60 42 7.42 293 1.88/11/2008 1218 30.3 20.11 Clear 2.4 21.9 8.59 42 7.39 298 1.78/11/2008 1218 30.3 20.11 Clear 2.7 21.8 8.61 42 7.37 300 1.7
Appendixes 1–3 51

Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued[BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy]

Date Time BP

Air

temperature 

(°C)

Sky

conditions

Depth

(m)

Water 

temperature 

(°C)

Dissolved 

oxygen 

(mg/L)

Specific 

conductance 

(μS/cm)

pH

Oxidation 

reduction 

potential 

(mV)

Turbidity 

(NTU)

8/11/2008 1218 30.3 20.11 Clear 3.0 21.8 8.60 42 7.35 302 1.88/11/2008 1218 30.3 20.11 Clear 3.4 21.8 8.57 42 7.29 604 1.98/11/2008 1218 30.3 20.11 Clear 3.7 21.8 8.56 42 7.30 605 1.98/11/2008 1218 30.3 20.11 Clear 4.0 21.7 8.54 42 7.24 609 1.98/11/2008 1218 30.3 20.11 Clear 4.3 21.6 8.16 42 7.13 313 2.18/11/2008 1218 30.3 20.11 Clear 4.6 21.2 6.94 43 6.79 327 3.38/11/2008 1218 30.3 20.11 Clear 4.9 20.2 2.02 49 6.34 393 4.48/11/2008 1218 30.3 20.11 Clear 5.2 19.2 .59 51 6.22 347 58/11/2008 1218 30.3 20.11 Clear 5.5 18.5 .29 56 6.13 309 4.68/11/2008 1218 30.3 20.11 Clear 5.8 18.1 .24 67 6.19 235 --8/11/2008 1218 30.3 20.11 Clear 6.1 17.3 .23 114 6.09 197 --8/11/2008 1218 30.3 20.11 Clear 6.4 17.3 .22 124 6.03 188 --9/8/2008 1042 30.21 14.28 Clear .3 17.1 8.66 44 7.27 423 09/8/2008 1042 30.21 14.28 Clear .6 17.1 8.64 43 7.25 425 09/8/2008 1042 30.21 14.28 Clear .9 17.1 8.60 44 7.26 425 09/8/2008 1042 30.21 14.28 Clear 1.2 17.1 8.57 44 7.20 428 09/8/2008 1042 30.21 14.28 Clear 1.5 17.1 8.57 43 7.16 430 09/8/2008 1042 30.21 14.28 Clear 1.8 17.1 8.58 43 7.12 430 09/8/2008 1042 30.21 14.28 Clear 2.1 17.0 8.55 43 7.16 431 09/8/2008 1042 30.21 14.28 Clear 2.4 17.0 8.55 44 7.16 431 09/8/2008 1042 30.21 14.28 Clear 2.7 17.0 8.53 44 7.12 433 09/8/2008 1042 30.21 14.28 Clear 3.0 17.0 8.51 43 7.13 433 09/8/2008 1042 30.21 14.28 Clear 3.4 17.0 8.51 44 7.12 433 09/8/2008 1042 30.21 14.28 Clear 3.7 17.0 8.50 43 7.11 434 09/8/2008 1042 30.21 14.28 Clear 4.0 17.0 8.48 44 7.12 434 09/8/2008 1042 30.21 14.28 Clear 4.3 16.9 8.47 44 7.09 436 09/8/2008 1042 30.21 14.28 Clear 4.6 16.8 8.36 44 7.08 436 .19/8/2008 1042 30.21 14.28 Clear 4.9 16.9 8.36 44 7.08 435 1.9
52 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies Appendix 2. Depth profiles of field properties for Speckled Trout Lake near Grand Portage, Grand Portage Reservation, northeastern Minnesota, 1997–2008.—Continued [BP, barometric pressure in millimeters mercury; °C, degrees Celsius; m, meters; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25°C; mV, millivolts; NTU, nephelometric turbidity units; --, no data; Pcloudy, partly cloudy] Date Time BP Air temperature (°C) Sky conditions Depth (m) Water temperature (°C) Dissolved oxygen (mg/L) Specific conductance (μS/cm) pH Oxidation reduction potential (mV) Turbidity (NTU) 9/8/2008 1042 30.21 14.28 Clear 5.2 16.8 8.28 44 7.10 429 0.4 9/8/2008 1042 30.21 14.28 Clear 5.5 16.9 3.00 49 6.27 353 -- 10/2/2008 1057 30.65 9.17 Cloudy .3 12.9 9.34 41 7.45 421 0 10/2/2008 1057 30.65 9.17 Cloudy .6 13.0 9.31 41 7.46 421 0 10/2/2008 1057 30.65 9.17 Cloudy .9 13.0 9.29 41 7.43 422 0 10/2/2008 1057 30.65 9.17 Cloudy 1.2 13.0 9.28 41 7.45 420 0 10/2/2008 1057 30.65 9.17 Cloudy 1.5 12.9 9.28 40 7.44 420 0 10/2/2008 1057 30.65 9.17 Cloudy 1.8 13.0 9.26 41 7.43 421 0 10/2/2008 1057 30.65 9.17 Cloudy 2.1 13.0 9.25 40 7.36 424 0 10/2/2008 1057 30.65 9.17 Cloudy 2.4 13.0 9.24 41 7.36 424 0 10/2/2008 1057 30.65 9.17 Cloudy 2.7 13.0 9.23 41 7.35 424 0 10/2/2008 1057 30.65 9.17 Cloudy 3.0 13.0 9.24 41 7.33 424 0 10/2/2008 1057 30.65 9.17 Cloudy 3.4 13.0 9.24 41 7.30 426 0 10/2/2008 1057 30.65 9.17 Cloudy 3.7 13.0 9.23 40 7.35 423 0 10/2/2008 1057 30.65 9.17 Cloudy 4.0 13.0 9.23 40 7.36 422 0 10/2/2008 1057 30.65 9.17 Cloudy 4.3 13.0 9.21 41 7.32 424 0 10/2/2008 1057 30.65 9.17 Cloudy 4.6 13.0 9.21 41 7.31 424 0 10/2/2008 1057 30.65 9.17 Cloudy 4.9 13.0 9.20 40 7.33 423 0 10/2/2008 1057 30.65 9.17 Cloudy 5.2 13.0 9.21 41 7.31 424 0 10/2/2008 1057 30.65 9.17 Cloudy 5.5 13.0 9.20 41 7.29 424 0
Appendixes 1–3 53

Appendix 3. Water-quality data collected by the U.S. Geological Survey for Swamp and Speckled Trout Lakes 

near Grand Portage, Grand Portage Reservation, northeastern Minnesota, September 11, 2006. 

[Site locations shown in figure 2; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; mg/L, milligrams per 

liter; CaCO3, calcium carbonate; Cl, Chloride; N, nitrogen; P, phosphorus; <, less than; E, estimated, less than laboratory reporting level 

and greater than the long-term method detection limit (Childress and others, 1993) for low concentration method; C, carbon]

Swamp Lake sample Speckled Trout Lake sample

Sample time 11:50 15:40

Specific conductance (μS/cm) 38.6 49.7

pH 7.07 7.52

Water temperature (°C) 15.0 17.2

Dissolved oxygen (mg/L) 8.36 8.2

Alkalinity (mg/L as CaCO3) 12 21

Bicarbonate (mg/L as CaCO3) 14 25

Chloride, dissolved (mg/L as Cl) .21 .21

Nitrogen, dissolved ammonia plus organic (mg/L as N) .6 .45

Nitrogen, dissolved nitrite plus nitrate (mg/L as N) <.04 <.04

Total dissolved nitrogen (mg/L as N) .76 .45

Total dissolved phosphorus (mg/L as P) .005 E.0024

Carbon, dissolved organic (mg/L as C) 16.65 4.78
54 Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies

Publishing support provided by: 

Rolla Publishing Service Center

For more information concerning this publication, contact:

Director, USGS Minnesota Water Science Center

2280 Woodale Drive

Mounds View, Minnesota 55112

(763) 783-3100

Or visit the Minnesota Water Science Center Web site at: 

http://mn.water.usgs.gov/
Appendixes 1–3 55
Christensen and others—Water Quality (2000–08) and Historical Phosphorus Concentrations from Paleolimnological Studies—Scientific Investigations Report 2010–5192