NOAA Technical Memorandum NOS ORCA 136

 

Baseline Clam Monitoring Study

Cannelton Industries Site

Sault Ste. Marie, Michigan

Summer 1997

Seattle, Washington

September 1998

noaa NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

National Ocean Service
Office of Ocean Resources Conservation and Assessment

National Ocean Service

National Oceanic and Atmospheric Administration

U.S. Department of Commerce

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NOAA Technical Memorandum NOS ORCA 136

Baseline Clam Monitoring Study

Cannelton Industries Site

Sault Ste. Marie, Michigan

Summer 1997

Hazardous Materials Response and Assessment Division

National Ocean Service

National Oceanic and Atmospheric Administration

7600 Sand Point Way NE

Seattle, Washington 98115-0070

and

EVS Consultants, Inc.

200 West Mercer Street, Suite 403

Seattle, Washington 98119

September 1998

Seattle, Washington

United States National Oceanic and National Ocean Service

Department of Commerce Atmospheric Administration Nancy Foster

William Daley D. James Baker Assistant Administrator

Secretary Under Secretary for Oceans for Ocean Services and

and Atmosphere Coastal Zone Management
Hazardous Materials Response and Assessment Division

Office of Ocean Resources Conservation and Assessment

National Ocean Service

National Oceanic and Atmospheric Administration

U.S. Department of Commerce

Silver Spring, Maryland

Citation

NOAA and EVS Consultants, Inc. 1998. Baseline Clam Monitoring Study, Cannelton Industries Site,

Sault Ste. Marie, Michigan, Summer 1997. NOAA Technical Memorandum NOS ORCA 136. Prepared

for U.S. Environmental Protection Agency, Region V, Chicago, Illinois. Seattle WA: Hazardous

Materials Response and Assessment Division, National Ocean Service, National Oceanic and Atmospheric

Administration, and EVS Consultants, Inc. September 1998, 44 pages + tables, figures, and appendices.

NOTICE

This report has been reviewed by the National Ocean Service of the National Oceanic and Atmospheric

Administration (NOAA) and approved for publication. Such approval does not signify that the contents of

this report necessarily represent the official position of NOAA or of the Government of the United States,

nor does mention of trade names or commercial products constitute endorsement or recommendation for

their use.
Baseline Clam Monitoring Study

Cannelton Industries Site

Sault Ste. Marie, Michigan

Summer 1997: Final Report

Prepared for

U.S. Environmental Protection Agency, Region V

77 West Jackson Boulevard

Chicago, Illinois 60604

Prepared by

Hazardous Materials Response and Assessment Division

National Oceanic and Atmospheric Administration

7600 Sand Point Way NE

Seattle, Washington 98115-0070

and

EVS Consultants, Inc.

200 West Mercer Street, Suite 403

Seattle, Washington 98119

EVS Project No. 2/575-38

September 1998
ii

Contents

1.0 INTRODUCTION.............................................................................................................. 1

1.1 Background ........................................................................................................................ 1

1.2 Program Objectives............................................................................................................ 3

2.0 STUDY DESIGN AND METHODS.................................................................................. 4

2.1 Site Description, Sampling, and Reference Stations ....................................................... 4

2.2 Species Selection ................................................................................................................ 5

2.3 Clam Collection, Sorting, Distribution, and Deployment.............................................. 6

2.4 Beginning-of-Test Tissue Preparation.............................................................................. 9

2.5 End-of-Test Measurements and Tissue Preparation..................................................... 10

2.6 Chemical Analyses .......................................................................................................... 11

2.7 Data Quality and Status Summary ................................................................................ 13

2.7.1 Tissue Chemistry Data ............................................................................................. 13

2.7.2 Clam Growth Data ................................................................................................... 14

2.8 Data Analysis ................................................................................................................... 14

2.8.1 Survival, Tissue Chemistry, and Clam Growth Metrics ........................................... 15

2.8.2 Temperature............................................................................................................. 17

3.0 RESULTS .......................................................................................................................... 18

3.1 Data Quality Review ....................................................................................................... 19

3.1.1 Tissue Chemistry Data ............................................................................................. 19

3.1.2 Growth Data............................................................................................................. 20

3.2 Survival............................................................................................................................. 20

3.3 Tissue Chemistry—Concentration and Content........................................................... 20

3.3.1 Arsenic ..................................................................................................................... 21

3.3.2 Cadmium.................................................................................................................. 21

3.3.3 Total Chromium....................................................................................................... 22

3.3.4 Lead.......................................................................................................................... 23

3.3.5 Total Mercury .......................................................................................................... 23

3.3.6 Methylmercury......................................................................................................... 24

3.3.7 Trace Element Bioavailability ................................................................................... 25

3.4 Clam Growth Metrics ...................................................................................................... 25

3.4.1 Whole-Animal Wet Weight....................................................................................... 25

3.4.2 End-of-Test Tissue Weights...................................................................................... 27

3.4.3 Percent Lipids........................................................................................................... 27

3.4.4 Percent Solids........................................................................................................... 28
iii

3.5 Temperature..................................................................................................................... 28

3.5.1 Testing for Differences in Mean Temperature........................................................... 28

3.5.2 Testing for Differences in Temperature Range.......................................................... 29

3.6 Sediment and Surface Water Chemistry vs. Tissue Chemistry................................... 29

3.7 Tissue Chemistry vs. Survival and Clam Growth Metrics........................................... 31

3.8 Temperature vs. Clam Growth....................................................................................... 31

4.0 DISCUSSION ................................................................................................................... 31

4.1 Meeting the Purpose and Objectives of the Study........................................................ 31

4.2 Survival of Deployed Clams........................................................................................... 32

4.3 Tissue Chemistry ............................................................................................................. 32

4.3.1 Tissue Concentration................................................................................................ 33

4.3.2 Tissue Content ......................................................................................................... 33

4.4 Sediment and Surface-Water Chemistry ....................................................................... 34

4.5 Comparison of Bioavailability and Sediment Contamination ..................................... 35

4.6 Comparison with Previous Studies................................................................................ 37

4.7 Growth.............................................................................................................................. 38

4.8 Temperature..................................................................................................................... 39

4.9 Problems Encountered during the Study ...................................................................... 40

5.0 RECOMMENDATIONS.................................................................................................. 41

6.0 REFERENCES .................................................................................................................. 42

7.0 TABLES

Table 1. Deployment position, time, water depth, and range of depth at each station.

Table 2. Analyte list and targeted detection limits for clam tissues.

Table 3. End-of-test percent survival for clams deployed in Tannery Bay and at reference

stations.

Table 4. Mean concentration (dry and wet weights) of trace elements in clam tissues.

Table 5. Mean content (μg dry weight) of trace elements in clam tissues.

Table 6. Results of statistical analyses on tissue concentration data.

Table 7. Results of statistical analyses on tissue content data.
iv

Table 8. Quotients derived by dividing end-of-test tissue content by initial tissue content.

Table 9. Descriptive statistics on clam growth metrics.

Table 10. Results of statistical analyses on clam growth metrics.

Table 11. Summary of water temperature conditions during the study, by station, summer

1997.

Table 12. Results of statistical analyses on mean daily temperature data.

Table 13. Differences in weekly temperature ranges across stations.

Table 14. Results of chemical analyses on sediment samples collected at the end of the

study.

Table 15. Results of chemical analyses on surface water samples collected at the beginning

and end of the study.

Table 16. Calculated quotients for end-of test sediment concentration/LEL, and sum of

quotients by station.

Table 17. Correlation coefficients for trace elements in surface water, sediment, and clam

tissues.

Table 18. Correlation coefficients for tissue chemistry vs. clam growth metrics based on

concentration and content.

Table 19. Correlation coefficients for temperature vs. clam growth metrics.

8.0 FIGURES

Figure 1. Location of Cannelton Industries, Inc., Sault Ste. Marie, Michigan, and clam

deployment stations in Tannery Bay and at reference stations near Waiska Bay (REF-1)

and Seymour Creek (REF-2).

Figure 2. Deployment layout at each experimental station.

Figure 3. Water level fluctuations in Tannery Bay throughout deployment period.

Figure 4. End-of-test percent survival of clams deployed in Tannery Bay and at reference

stations.

Figure 5a. Arsenic concentration in tissues of clams deployed in Tannery Bay and at

reference stations.

Figure 5b. Arsenic content of clams deployed in Tannery Bay and at reference stations.

Figure 6a. Cadmium concentration in tissues of clams deployed in Tannery Bay and at

reference stations.

Figure 6b. Cadmium content in clams deployed in Tannery Bay and at reference stations.
v

Figure 7a. Total chromium concentration in tissues of clams deployed in Tannery Bay and

at reference stations.

Figure 7b. Total chromium content in clams deployed in Tannery Bay and at reference

stations.

Figure 8a. Lead concentration in tissues of clams deployed in Tannery Bay and at reference

stations.

Figure 8b. Lead content in clams deployed in Tannery Bay and at reference stations.

Figure 9a. Total mercury concentration in tissues of clams deployed in Tannery Bay and at

reference stations.

Figure 9b. Total mercury content in clams deployed in Tannery Bay and at reference

stations.

Figure 10a. Methylmercury concentration in tissues of clams deployed in Tannery Bay and

at reference stations.

Figure 10b. Methylmercury content in clams deployed in Tannery Bay and at reference

stations.

Figure 11. End-of-test whole-animal wet weight for clams deployed in Tannery Bay and at

reference stations.

Figure 12. Whole-animal wet-weight growth rates for clams deployed in Tannery Bay and

at reference stations.

Figure 13. End-of-test tissue weights for clams deployed in Tannery Bay and at reference

stations.

Figure 14. Percent lipids for clams deployed in Tannery Bay and at reference stations.

Figure 15. Percent solids for clams deployed in Tannery Bay and at reference stations.

Figure 16. Water temperatures in Tannery Bay and at reference stations.

Figure 17. Average daily temperatures in Tannery Bay and at reference stations.

9.0 APPENDICES

Appendix A Draft standard guide for conducting field bioassays with marine,

estuarine and freshwater bivalves.

Appendix B Tissue chemistry laboratory reports.

Appendix C Brooks Rand, Ltd., Standard Operating Procedures.

Appendix D Statistical analyses and results for chemistry and growth.

Appendix E Clam measurement data.

Appendix F Photographs of sampling events and activities.
1

1.0 Introduction

The purpose of this document is to present the results of the baseline clam

monitoring study conducted for the Cannelton Industries, Inc. site, situated

adjacent to the St. Mary’s River, Sault Ste. Marie, Michigan. This baseline is

being conducted as an initial phase of long-term monitoring to verify the

effectiveness of the selected remedy for this site. There is concern that

indigenous and migrating species utilizing the site may be subject to adverse

impacts from waste materials at the site (Cannelton Ind. 1995a). Metals

contamination in Tannery Bay is largely present in tannery waste and organic

soils, which have the capacity to immobilize metals and limit their

bioavailability.

Previous analyses indicated that contaminated soils, wastes, and sediments have

low potential for leaching (Cannelton Ind. 1995a). The results of these studies

also suggest that there is minimal leaching and movement of contaminants from

site soils into groundwater and surface water. Sediment toxicity and

bioaccumulation studies performed during pre-design investigations indicated

that contaminated soil and sediment which would remain unremediated do not

pose an unacceptable risk to aquatic and terrestrial organisms. However, some

results of these studies were inconclusive. The Pre-Design studies suggest that

the high organic load in Tannery Bay sediments is reducing the availability of

metals for accumulation by aquatic organisms (Cannelton Ind. 1995a). Analysis

of aerial photos indicates that sedimentation is occurring in the western portion

of Tannery Bay and may be providing a natural cap for contaminated sediments.

The Amended ROD (U.S. EPA 1996) requires that a monitoring program for

Tannery Bay include evaluation of the bioavailability of site contaminants to

ensure the protectiveness of the remedy for aquatic organisms and wildlife. In

response to the U.S. EPA’s request, NOAA designed a biological monitoring

program using caged clams and conducted the baseline sampling. This report

details the methods and results for the baseline study, and provides

recommendations for future years’ monitoring.

1.1 Background

The Cannelton Industries, Inc. site, the location of a former tannery, covers 23

hectares (ha) (75 acres) along St. Mary’s River in Sault Ste. Marie, Michigan

(Figure 1). Most of the shore areas are wetlands, with wetland vegetation, soils,

and hydrology. Wetland forest species and emergent cattail marshes are the

primary vegetation types present. From 1900 to 1958, tannery and animal-hide

processing operations were conducted at the site. Waste products from these

operations were routinely discharged to shoreline areas via three facility
2

drainage systems. Trace elements (chromium, mercury, lead, cadmium, and

arsenic), cyanide, calcium carbonate, sulfide, brine, organic solvents, formic acid,

carbolic acid, formaldehyde, ammonia, and alcohols were the primary

contaminants associated with the waste products (WW Engineering 1991). In

1955 the site became the property of the Fiborn Limestone Company, a

subsidiary of Algoma Steel Corporation. A fire damaged the buildings in 1958,

which were subsequently torn down and removed. The facility has remained

unused and vacant since then. In 1964 the property was transferred to

Cannelton Industries, another Algoma subsidiary.

In 1978, the Michigan Department of Natural Resources determined that soils,

groundwater, and river sediment from the site were contaminated with heavy

metals, primarily chromium and mercury (U.S. EPA 1994). The site was listed as

a National Priorities List (NPL) site in 1990 (U.S. EPA 1994). Supplemental

investigations confirmed that surface sediments in Tannery Bay contained

elevated concentrations of chromium and mercury (Kracko 1992). Maximum

concentrations of chromium and mercury reported in that study were 40,000 and

2.29 mg/kg dry weight, respectively. Laboratory tests conducted with

sediments collected from St. Mary’s River and Tannery Bay suggested potential

toxicity. However, the responses of test organisms were associated, not clearly

correlated, with site contaminant concentrations. The small size of the data set

limits definitive conclusions. Laboratory tests were conducted with the midge

(Chironomus riparius), amphipods (Hyalella azteca), and green algae (Selenastrum

capricornutum). The results of the Chironomus bioassays indicated that sediments

were not acutely toxic; there were no statistically significant differences in

mortality between sample locations and the reference location or the laboratory

control. The weight of C. riparius was moderately correlated (r

2=0.63) with

chromium concentration. The results of the Hyalella test were mixed. Mortality

was observed in all sediment samples, including sediment from the upstream

reference location, and ranged from 45% to 100%. There was no correlation

between observed mortality and chromium concentrations, nor between any

other metal concentration or physical parameter measured.

As mandated in the signed 1992 ROD for the Cannelton Industries site, a study

was initiated in 1994 to determine the extent of contamination in river sediments

and the bioaccumulation of chromium and mercury in aquatic biota. Sediments

in Tannery Bay were found to be contaminated with chromium and mercury at

maximum concentrations of 30,000 and 1.7 mg/kg wet weight, respectively (U.S.

EPA/ERT 1995). Fish and crayfish were also collected from Tannery Bay during

that study; tissues were analyzed for metals and percent moisture. Maximum

concentrations of chromium in minnows and crayfish collected from Hairball

Beach were 7.6 and 29 mg/kg wet weight, respectively. Maximum

concentrations of mercury in the same species were 0.03 and 0.08 mg/kg wet

weight, respectively. Based on the results of aquatic studies, the U.S. EPA has

concluded that, although there are potential ecological risks due to mercury
3

exposure at the site, there is no incremental increase in mercury risk associated

with the site (Jones 1996). This decision was based on the absence of any

demonstrated difference in mercury body burden between the reference and any

other sampling locations, or between sampling locations. The mercury risk

conclusion was consistent with the system-wide problem of mercury in St.

Mary’s River.

1.2 Program Objectives

The purpose of the biomonitoring program is to document whether the selected

remedy for the site is effective at reducing concentrations of bioavailable trace

elements in Tannery Bay. The specific objectives of the biomonitoring program

are to determine 1) whether chromium, total mercury, methylmercury, lead,

cadmium, and arsenic in Tannery Bay sediments are available to biota residing

in and/or using the Bay, and 2) whether exposure to bioavailable concentrations

of metals may adversely affect local biota.

The objective of this study is to provide baseline data for the biomonitoring

program. To assess availability, uptake of these trace elements was measured in

tissues of caged clams, Corbicula fluminea, transplanted to Tannery Bay and

reference areas. Changes in bioavailability over time will be determined by

comparing tissue residue levels measured in future years with the values

measured in the present baseline study. Survival and changes in clam wholeanimal weights and end-of-test tissue weights were evaluated as indicators of

potentially adverse effects. This study is not designed to assess all acute and

chronic aquatic toxicity endpoints. Therefore, lack of effects demonstrated by

this study does not preclude the potential for reproductive or other physiological

effects. Measurements made during 1997 will provide a baseline for subsequent

monitoring years. Impacts of contamination to the ecological food chain will be

assessed in subsequent sampling events following remediation.

The long-term biomonitoring program will generate biological and chemical

data to meet the program objectives. This biomonitoring program has three

components: 1) evaluation of clams transplanted to the study area for uptake of

trace elements and growth effects, 2) analysis of sediments for concentrations of

metals and selected physicochemical parameters, and 3) analysis of surface

water for chlorophyll-a and selected physicochemical parameters. Evaluation of

these synoptic data can be used to evaluate changes in chemical bioavailability

and potential effects on local biota.
4

2.0 Study Design and Methods

This section describes the methods used in the baseline biomonitoring study

with caged clams. The bioavailability of chemicals was assessed by measuring

accumulation in clam tissues after a fixed exposure period. Effects from

exposure to site-specific conditions were assessed by comparing survival and

changes in growth among stations. The methods used to collect and analyze the

surface-water and sediment samples are being prepared by Cannelton as a

separate report. The appendices contain all data obtained during the baseline

monitoring study, as well as the statistical processes used to analyze this data,

and procedures for elements of this study that are not readily available in the

open literature.

2.1 Site Description, Sampling, and Reference Stations

The Cannelton Industries site is located on the south bank of St. Mary’s River in

Sault Ste. Marie, Chippewa County, Upper Peninsula, Michigan (Figure 1). The

site is bounded to the north by St. Mary’s River and Tannery Bay, to the south by

4

th Avenue and the Soo Railway, to the west by 18th Street, and to the east by

open land. Tannery Bay and St. Mary’s River were general waste dumping

areas and tannery waste discharge areas during facility operations (U.S.

EPA/ERT 1995). Aerial photographs indicate that some of the tannery waste

deposited on the St. Mary’s River shoreline has eroded over time. Both this

eroded material and material dumped into the river during the plant’s operation

were likely carried downstream by the river and deposited both along the

shoreline of Tannery Point and in the low-energy water found downstream in

Tannery Bay (WW Engineering 1991).

Tannery Bay was selected as the primary area of investigation for this

biomonitoring program because sediments from this area historically have the

highest concentrations of trace elements associated with tannery wastes. Eight

stations in Tannery Bay were monitored during this baseline monitoring study

(Figure 1). The distribution of stations in Tannery Bay was designed to allow a

thorough evaluation of chemical bioavailability. Some of these stations represent

areas previously identified as ìhot spotsî of chromium and/or mercury

contamination.

Reference areas have a key role in evaluating field bioassays. Reference areas

should be similar to the treatment sites, with no source of contamination, and

reflect conditions that exist at the treatment sites. Because of the difficulty in

identifying one representative reference site, more than one reference station is

used. In this approach, the reference locations are not viewed as a single station

or point, but as the average of all the individual reference samples. Because of

widespread contamination in Tannery Bay and in St. Mary’s River in the vicinity

of the tannery site, it was deemed necessary to situate reference stations in other
5

embayments of the river. Potential reference sites along the open shore areas of

St. Mary’s River to the west of the Cannelton facility–including Seymour Creek,

Izaak Walton Bay, and Waiska Bay–were surveyed and evaluated for their

suitability as reference areas. One reference station (Reference Station 1) was

established in Waiska Bay to represent highly vegetated, shallow habitats. A

second reference station (Reference Station 2) was established in St. Mary’s River

near the mouth of Seymour Creek to represent sandy, shallow habitats with

minimal vegetation. St. Mary’s River is a highly dynamic system, with very few

low-energy areas similar to Tannery Bay making it difficult to identify areas

appropriate for use as reference.

In addition to the two reference areas, a holding site was identified and used for

short-term holding of clams and as a source of clean water from St. Mary’s River.

The holding site was located nearshore in St. Mary’s river upstream of the old

Oriole Boulevard boat ramp (Figure 1).

2.2 Species Selection

A non-resident freshwater clam, Corbicula fluminea, was selected for this

monitoring program because they are routinely used in environmental

assessment programs and have been used extensively to assess metals and

organic chemical contamination (Belanger et al. 1987; Colombo et al. 1995;

Doherty 1990; Elder and Mattraw 1984; Farris et al. 1988; Foe and Knight 1987;

Leland and Scudder 1990; Luoma et al. 1990; Mac et al. 1984; Tatem 1986).

Corbicula fluminea exhibit a high tolerance for the effects resulting from exposure

to toxic substances. They accumulate and concentrate trace elements and metals

to concentrations that are orders of magnitude greater than concentrations found

in surface waters without demonstrating high rates of mortality. If the

transplanted species shows accumulation of chemicals, then exposure and effects

in resident species, including predator species, may also be of concern.

Corbicula live in the sediments but are filter feeders – they feed primarily on

suspended seston (i.e., phytoplankton, bacteria, and fine detritus) by filtering

suspended material from water as it passes over the gills. Corbicula filter

particles from 1.5 to 10 microns (μ) in size and can efficiently filter particles

smaller than 1.0 μ. Although Corbicula inhabit, and remove detrital particles

from the sediments, they do not ingest sediment directly (D. Cherry, pers.

commun. 1998). Researchers conducting extensive studies on Corbicula over the

past 20 years have examined numerous clams and found none to contain

sediment in their gut. Denser, larger particles are bound in mucus and carried

by a ciliated ventral groove to the tip of the palp for release onto the mantle as

pseudofeces; pseudofeces are carried by mantle cilia and expelled through the

inhalant siphon. Particle sorting appears to be a function of particle size and

density (McMahon 1991). This feeding strategy makes Corbicula a good

biomonitoring organism: they are actively exposed to the sediment/surfacewater interface where chemical activity and chemical exchange between the

water and sediments are high due to continuously changing physical/chemical

conditions (D. Cherry, pers. commun. 1998).
6

2.3 Clam Collection, Sorting, Distribution, and Deployment

Clams (Corbicula fluminea) were collected by hand from runs and riffles in Saline

River, Arkansas on July 8, 1997 by Dr. J. L. Farris, Arkansas State University. All

clams were collected from areas presumed free of chemical contamination,

disease, and pest species (e.g., Zebra mussels). At the collection site, clams were

sorted by size (>1 cm, <3 cm shell length) and checked for condition (i.e.,

damaged shells). Clams outside the desired size range or in poor condition were

rejected. Clams were held in a laboratory flow-through system without

sediment for 4 days for acclimation to temperature, dissolved oxygen, and pH

conditions characteristic of the deployment sites. The clams were not fed during

the acclimation period to encourage elimination of all material from the gut.

After acclimation, approximately 5000 clams were placed in ice chests containing

cool, moist packing material (not wet) and sent via air freight to Sault Ste. Marie,

Michigan. Total shipment time was approximately 15 hours. Within 6 hours of

delivery in Sault Ste. Marie on July 15, 1997, the clams were removed from their

packing and inspected for overall condition. The clams appeared to be in

excellent health, with less than 1% mortality.

Whole-animal wet weight, measured to the nearest 0.01 g, was the criterion used

to select clams for this baseline monitoring study. The clams were removed

from their packing material and placed into tubs containing fresh water from the

holding site. All clams were processed and treated according to the draft

guidelines submitted to ASTM for review (Appendix A). A rough sort was

conducted to separate clams into small, medium, large, and extra large sizeclasses. Based on the distribution of sizes, the number within each size category,

and the amount of tissue required for chemical analyses, only clams >4.0 and

<8.0 g whole-animal wet weight were selected for use in this study. Following

the rough sort, the clams were distributed to the mesh tubes as described below.

The pre-sorted clams were maintained in the holding tubs until needed for

distribution. Their normal temperature range was maintained during all phases

of the setup activities by placing bags of ice in the tubs of fresh river water.

Detailed attention was given to the care and handling of clams throughout the

setup process to minimize stress to the animals and to ensure that all test animals

were of high quality.

Just before the final measurement and distribution processes, small batches of

clams were removed from the holding tubs and placed into smaller bowls filled

with cool, fresh water. The clams were kept in water before being measured to

ensure the internal cavity between the shells was completely filled with water,

eliminating potential errors in whole-animal wet weights associated with air

bubbles. Only live animals that were completely submerged and fully closed, or

those that closed immediately upon light physical stimulation, were used.

Closed clams that appeared to be ìfloatingî or ìbuoyantî were not used because

this is a sign of air bubbles between the shells.
7

The measurement process involved obtaining and recording the whole-animal

wet weight for each clam, measured to the nearest 0.01†g with an electronic

balance. After the weight measurements, each clam was placed into a prelabeled mesh tube ∼10.2 cm (4 inches) in diameter and 2.1 m

(7 ft) long; 0.6-cm (0.25-inch) mesh size. Nylon cable ties were used to separate

individual clams within the tube. Each tube contained 25 clams. After all clams

were distributed to the mesh tubes, they were placed in an ice chest and

transported to the holding area for overnight deployment. To minimize

predation, the mesh tubes containing clams were placed inside an envelope

made of heavy-duty plastic screen. The clams were held at this location for

approximately 14 hours before deployment in Tannery Bay beginning on July

16, 1997.

Four cages, each containing 75 clams, were deployed at ten stations: eight

Tannery Bay and two reference stations. Station 11 was used to represent the

clams to be used for beginning-of-test weight measurements and chemical

analysis of tissues. Prior to deployment in Tannery Bay and at the reference

stations, the mesh tubes containing clams were affixed to cages ∼0.5 m wide by 1

m high constructed of 2.5-cm diameter polyvinyl chloride (PVC) pipe material.

Each cage contained 75 clams, and 4 cages were prepared for each station for a

total of 300 clams per station. Large nylon cable ties were used to secure the

mesh bags to the PVC cage. One continuously recording temperaturemonitoring device was attached to one clam cage for each station and set to

collect temperature data at 12-min intervals over the deployment period. The

cages were then wrapped with the heavy-duty plastic screen (∼2.5-cm mesh size)

to discourage predators. The completed cages were then placed back into the

water at the holding area until deployment.

Before deployment, a random-numbers table was used to assign cages to

stations. The cages, numbered from 1 to 44, were assigned station numbers by

using the first 2 digits of the 5-digit random numbers. If the 2-digit number was

between 01 and 11, it was used as the station number for Cage 1. The next 2-

digit number between 01 and 11 was identified and used as the station number

for Cage 2. This process was continued until all cages were assigned a station

number from 1 through 11, with four occurrences of each station number.
8

The data were normally distributed; an Analysis of Variance test (ANOVA) was

used to confirm statistically similar size distribution of clams among cages and

stations (P=0.05). At the beginning of the test, the mean clam weight was

statistically similar among all 44 cages. The data were pooled by station and

analyzed for similar size distribution; there was no statistical difference in mean

clam size among any of the 11 stations at the beginning of the test. Results of the

statistical analyses are summarized below; complete details are provided in

Appendix D.

ANOVA Results

H0 = No significant differences in whole-animal wet weight among cages.

Source of Variation SS df MS F P-value F crit

Between groups 32.24341 42 0.7677 1.093392 0.314455 1.387843

Within groups 2234.168 3182

0.702127

Total 2266.411 3224

ANOVA Results

 H0 = No significant differences in whole-animal wet weight among stations.

Source of Variation SS df MS F P-value F crit

Between groups 5.851184 10 0.585118 0.831173 0.598455 1.833573

Within groups 2315.347 3289 0.703967

Total 2321.199 3299

SS–sums of squares; df–degrees of freedom; MS–mean square; F–F statistic = group MS/ error MS;

P-value–probability value; F crit–critical value for determining significance of F statistic.

Cages were deployed at Stations 1, 3, 4, 5, 6, and 8 on July 16, 1997. The

remaining cages for Stations 2, 7, 9 and 10 were held overnight at the holding

area until deployment the following day. Four cages of clams were deployed at

each station and placed about 2 m apart around the center of the station (Figure

2). A cement block was positioned in the center of the deployment station. The

cages were secured to the block with nylon rope and situated ∼2 m from the

block. Smaller cement blocks were used as weights to hold each cage in

position. Surface markers were used to identify the deployment locations.

Cages for Station 8 and Reference Station 2, areas likely encountered by boaters,

were labeled with a warning tag to discourage vandalism or removal by

trespassers. Stations were positioned using a Trimble ProXL and ProBeacon

differential GPS. Latitude and longitude coordinates for the stations are

provided in Table 1. The survey locations are accurate to approximately ±2 m.

The water depth at each station was taken during deployment using a stick and

metal tape measure. Depths ranged from 0.5 m (1.6 ft) to 1.4 m (4.5 ft) (Table 1).

Because of the concern that some areas of Tannery Bay or Saint Mary’s River

would be exposed to air during a seiche, two pressure transducers (InSitu, Inc.,

PDX-260) were installed on July 18, 1997, one at the ìnorthernî end of the bay

and one at the ìsouthernî end (Figure 1). The purpose of these transducers was

to record water-level changes over the course of the biomonitoring study.
9

The transducers were removed on September 10, 1997. Figure 3 illustrates the

water-level fluctuations during the study. The water levels ranged from −0.2 to

0.4 m (−0.47 to 0.97 ft) relative to the initial baseline measurement (Table 1).

Comparing the initial water depths with the changes in depth shown in Figure 3

shows that the clams remained submerged throughout the entire study.

2.4 Beginning-of-Test Tissue Preparation

An additional 300 clams (i.e., 4 cages of 75 clams each) were used for initial

tissue-weight determinations and chemical analyses to obtain background

concentrations of contaminants. For tissue chemistry analysis, tissues from 75

individual clams in each cage are combined to form a replicate; therefore, each

cage is considered an analytical replicate. All equipment (i.e., shucking knives

and the aluminum foil covering the cutting boards) used during tissue extraction

was thoroughly cleaned before processing a new batch (i.e., replicate) according

to the following process: Wash with Liquinox, rinse with hot tapwater, rinse

with deionized water. Prior to tissue removal, all staff thoroughly washed their

hands with Liquinox. Gloves were not worn during the shucking process to

reduce the potential for injury from slippery hands and handling wet clams.

The shucking process began by notching the clam shell with a sturdy knife to

allow penetration of a thin-bladed knife. A thin-bladed stainless steel knife was

inserted into the notch and used to slice the clams in half. After the shells were

spread apart, the thin-bladed knife was used to remove the soft tissues. The

severed tissue was held in such a position that the excess liquid was allowed to

drain. The soft tissues were kept on the shell during extraction and after

complete separation. The shell was used as a ìholding dishî until tissue weights

were made. A weigh pan was made from decontaminated aluminum foil. The

soft tissues were placed on the weigh pan using the original shucking knife.

When all tissues of a ìreplicateî were weighed, the tissues were transferred from

the weigh pan to certified clean sample jars provided by Brooks Rand, the

analytical laboratory. Each sample jar was tightly capped, affixed with a

prepared label, and placed in the freezer. The aluminum-foil weigh boat and

cutting-board cover were discarded after all tissues of a given replicate were

shucked and weighed. All shucking equipment was decontaminated before

proceeding to the next sample.

The average whole-animal wet weights by cage for these 300 clams were

statistically similar to each of the other cages prepared for deployment at the

Tannery Bay stations. Actual whole-animal wet weights and tissue weight data

for the 300 clams used to define initial weights for all clams are provided in

Appendix E. The average tissue weight of 0.66 g was used as an initial estimate

for all field-deployed clams.
10

2.5 End-of-Test Measurements and Tissue Preparation

All clam cages were successfully found and retrieved after the 55-day exposure

period. Clams at Stations 1, 3, 4, 5, 6, and 8 were retrieved on September 9, 1997;

clams at Stations 2, 7, 9 and 10 were retrieved the following day. After removal

from the field stations, the caged clams were transported to Station 2 (the

shallow-water reference site) for an overnight depuration period to purge their

guts. To facilitate deployment logistics, the cages retrieved on September 9 were

altered by combining all clam tubes for a given station onto one PVC frame. A

fewer number of cages were retrieved on September 10th so that all station clams

were not combined onto one cage for overnight depuration; clams remained

attached to their original cages. For both days, the cages were deployed in a

horizontal configuration on top of the cinder blocks used for tethering at each

site. Several cinder blocks were used to ensure a stable configuration. This

configuration prevented the clams from coming in direct contact with the

sediments at the depuration site. Before retrieving the cages the following

morning, they were visually inspected to ensure that they had not shifted via

river current or vandalism during the night. Prior to making the end-of-test

measurements, the clams were assessed for overall condition, and the number of

dead and/or missing animals was recorded for each station. Clams that were

gaping or did not close upon light physical stimulation were considered dead.

The end-of-test measurements involved whole-animal wet weights and softtissue weights for each live individual. The clams were processed one cage at a

time. The clams were removed from the mesh tubes and placed, in sequence

starting with the first clam in Bag-1, into compartmentalized holding trays. If a

dead clam was encountered, the empty shells were placed into the

compartmentalized holding tray as a marker. These holding trays were then

placed into tubs containing river water to eliminate air bubbles between the clam

shells. Starting with the first clam, the clam was taken from the holding tray,

blotted dry, and the whole-animal wet-weight measurements were made using

an electronic balance. The weighed clam was then put into a second

compartmentalized tray to maintain proper sequence. The weight data were

recorded manually onto laboratory data sheets and electronically to a computer

file. The process was repeated until all individuals of a given cage were

measured.

The clam tissues were processed after all whole-animal wet-weight

measurements were made. The tissue extraction process was the same for the

beginning-of-test clams (see Section 2.3). Tissues from all live clams (~75

individuals) found within each cage were pooled, creating a replicate sample for

chemical analysis. When all tissues of a ìreplicateî were weighed, the tissues

were transferred from the weigh pan into certified cleaned sample jars, as

provided by Brooks Rand, Ltd. Immediately after compositing, the clam tissue

samples were placed into a freezer. The frozen tissue samples were packed,

cooled with blue ice to 0°C, and hand delivered to Brooks Rand, Ltd., of Seattle,

Washington for homogenization, lipid analysis, percent water determination,
11

and chemical analysis of chromium, total and methylmercury, lead, cadmium,

and arsenic.

2.6 Chemical Analyses

All tissue samples were received, stored, prepared, and analyzed according to

Brooks Rand, Ltd., Standard Operating Procedures (Appendix C). Upon receipt,

the tissue samples were assigned an internal tracking number. The tissue

samples were preserved by freezing and stored in a Brooks Rand freezer until

further processing.

For each chemical replicate, all tissues comprising that replicate were

homogenized using stainless-steel homogenization equipment. All equipment

was cleaned with Alconox and thoroughly rinsed with deionized water. One

homogenization blank was collected for each homogenization batch. Blanks

were collected between samples after equipment had undergone the normal

cleaning procedure. All samples were homogenized prior to weighing aliquots

for the various analytical parameters.

Methylmercury analyses were conducted in accordance with Brooks Rand

Standard Operating Procedure (SOP) BR-0011. Before analysis, the tissue

samples were digested in 25% KOH in methanol (w/v) in Teflon vials for 4 hr at

65°C. Samples were then analyzed by aqueous phase ethylation, Tenax trap

collection, gas chromatograph (GC) separation, isothermal decomposition, and

cold vapor atomic fluorescence spectrophotometry (CVAFS).

Total mercury analyses were conducted in accordance with SOP BR-0002. Before

analysis, all tissue samples were digested with a 70:30 HNO3:H2SO4 acid mixture

and allowed to reflux for at least 3 hr. Samples were then brought to volume

with deionized water and further oxidized with the addition of BrCl. Samples

were analyzed by SnCl2 reduction, gold amalgamation, and CVAFS detection.

Tissue samples to be analyzed for arsenic, cadmium, chromium, and lead were

digested in accordance with EPA Method 200.3. No problems were encountered

and no unusual observations were made during these analyses. Analyses for

total lead, chromium, total cadmium, and total arsenic were performed in

accordance with EPA Method 200.9. Samples were analyzed by stabilized

temperature platform−graphite furnace atomic absorption (STP-GFAA)

detection.
12

Dry-weight determinations (SOP BR-1501) were made by weighing out tissues

on pre-weighed weigh boats and placing them in a drying oven (105°C). After

16 to 24 hr, the samples were removed and reweighed. One duplicate dry

weight was measured for each batch of samples.

Percent lipid determinations were made by the Bligh and Dyer method.

Weighed tissue-sample aliquots were placed in a glass tissue grinder with

chloroform and methanol and ground for at least 2 min. More chloroform was

added and the sample ground for 30 sec. Deionized water was added and the

sample was ground again for approximately 30 sec. In the resulting biphase

system, the chloroform layer contains the lipids and the methanol-water layer

the non-lipids. A purified lipid extract is obtained when the chloroform layer is

isolated. Samples were then allowed to dry at 55°C for at least 30 min. After

drying, total lipids were determined by weight and converted to percent lipids

based on the original aliquot weight, according to the following equation:

Total lipid = (weight of lipid in aliquot) * (volume of chloroform layer) .

Volume of aliquot

For each chemical, the content (μg) in clam tissues was calculated on a perreplicate basis using the average whole-animal dry-weight value for that

replicate and the chemical concentration data for that replicate. The content is

reported in units of μg because this eliminates the need for many decimal places

in the presentation. This process provided four content values per station for

statistical comparison. Tissue content was calculated according to the following

equation:

 Content (μg) = [concentration (mg/kg dry)] * [EOT tissue weight (g dry)]

 * 1 kg/1000 g * 1000 μg/1 mg .

The content information was used to determine whether growing clams actually

accumulated chemicals of concern, since the overall concentrations may actually

decrease in fast-growing individuals due to growth dilution. Salazar & Salazar

(1995) and Riisgård & Hansen (1990) have shown that faster-growing, smaller

bivalves take up more contaminants, even though tissue concentrations decrease.

Therefore, content provides data on net uptake or depuration and was used in

this study to determine whether clams transplanted in St. Mary’s River for 55

days contained more of a specific trace element than at the onset of the study.
13

2.7 Data Quality and Status Summary

2.7.1 Tissue Chemistry Data

All chemical data for this project were subjected to a quality

assurance/quality control (QA/QC) review. Results of the laboratory QC

measurements are provided in Appendix B. The data for the chemical analyses

were also evaluated using the criteria described in the ìFunctional Guidelines for

Evaluating Inorganics Analysesî in conjunction with laboratory-established quality

control limits and the data-quality objectives specified in the ìQuality Assurance

Project Plan for Development and Implementation of Bivalve Monitoring Studyî

prepared for U.S. EPA Region V by NOAA/EVS Consultants (1997). In addition

to checking the data against the project-specific data quality objectives (Table 2),

the data were evaluated as listed below.

Holding Times3⁄4The holding times for arsenic, cadmium, chromium, and

lead are 6 months for unfrozen or 2 years for frozen samples. The holding times

for mercury and methylmercury are 28 days for unfrozen and 1 year for frozen

samples.

Initial calibrations and continuing calibration verifications3⁄4The initial

calibration must be established before each analysis period and have a

regression factor of 0.995 or better. The continuing calibrations must be

analyzed after every 10 samples and be within 25% of the absolute value.

Blanks3⁄4A preparation blank must be digested and analyzed with each

sample batch. In addition, a continuing calibration-verification blank must be

analyzed after each continuing calibration verification. Analytes present in

blanks must not be greater than 5 times the method reporting limit.

Laboratory control sample or certified reference material3⁄4A laboratory

control sample or certified reference material must be analyzed with each

sample batch. The value must be within the project specific limit for accuracy.

Duplicate sample analyses3⁄4A duplicate sample analysis must be

analyzed with each sample batch. The relative percent difference determined

from the two analyses must be within the project specific limit for precision.

Matrix spike analyses3⁄4A matrix spike analysis must be performed with

each sample batch. The percent recovery must be within the project specific

limit for accuracy.
14

Sample result verification3⁄4At least 10% of the sample results should be

verified for calculation and/or transcription errors. In addition, 100% of the

quality-control sample results (relative percent differences and percent recovery)

should be verified for calculation and/or transcription errors.

Overall assessment3⁄4Sample results should be assessed for overall use.

2.7.2 Clam Growth Data

The QA/QC procedures for the clam growth measurements stated that

5% of the clams would be remeasured for shell length and whole-animal wet

weight. These procedures further stated that this QA/QC check would be

conducted only if sufficient time was available, without jeopardizing the other

components of the study. The formal QA/QC check was completed during both

the initial and end-of-test field components of this study.

2.8 Data Analysis

The bioavailability and uptake of trace elements were assessed using the tissue

concentration and content measurements. Whole-animal wet weights and tissue

weights were used to calibrate, or normalize, the tissue chemistry data by

determining whether growth dilution or ìshrinkage-enhancementî had occurred.

Effects were assessed using survival, changes in whole-animal wet weights, and

tissue weight measurements. Survival was used as a general indicator of

conditions at the stations. Low survival would suggest physicochemical

conditions at the station are degraded, but it would be impossible to determine

which parameter is responsible for the observed mortality.

For bioaccumulation, each composited sample (e.g., tissues from all surviving

clams from one cage) is considered a replicate. Four composites were prepared

for each station; therefore, the level of replication for the bioaccumulation data is

four. For whole-animal wet weight and end-of-test tissue weight, each

individual clam is considered a replicate. Therefore, for these measurements,

the maximum possible level of replication at each station is 300, if all clams

survived. For this monitoring study, the maximum survival was 284 clams,

which occurred at Station 8. Descriptive summary statistics (e.g., mean and

standard deviation) were calculated for all bioaccumulation and clam growth

data collected during this baseline monitoring study.

For the reference stations, all data for both reference stations were pooled and

analyzed as a single unit for comparisons against the Tannery Bay stations. The

pooled results are referred to as the average of the Reference Stations.
15

2.8.1 Survival, Tissue Chemistry, and Clam Growth Metrics

Statistical analyses were performed on bioaccumulation (i.e.,

concentration and content), survival, whole-animal weight, and tissue weight

data from the in†situ clam study. Two general hypotheses were tested:

1. Contaminants in Tannery Bay sediments and surface waters

are bioavailable to aquatic receptors in Tannery Bay

2. Accumulation of bioavailable metals may adversely affect

aquatic receptors in Tannery Bay as assessed by changes in

whole-animal wet weights and tissue weights in clams

These general hypotheses were tested by statistical analyses of

contaminant accumulation and growth in caged clams exposed to ambient

Tannery Bay conditions. The following specific hypotheses were tested:

ï There is no difference in mean response between Tannery Bay stations

and reference stations.

ï There is no difference in mean response among Tannery Bay 

stations.

ï There is no difference in mean response between beginning and end of

test.

The specific hypotheses were tested using a one-way Analysis of

Variance (ANOVA). If the hypotheses were rejected, indicating that significant

differences among all stations were detected, pairwise contrasts were performed

to determine which stations differed from the reference stations. The Student

Newman-Keuls test was used to test for differences among Tannery Bay stations.

All tests were conducted at P=0.05.

Before proceeding with the ANOVA, the bioaccumulation, whole-animal

weight, and tissue weight data were evaluated to ensure that they met the

assumptions of the statistical tests (i.e., approximate normality and homogeneity

of variances for the ANOVA, Bonferroni multiple contrasts, and Dunnett’s

multiple contrasts). This evaluation was performed using normal probability

plots and a plot of the variance on a station-by-station basis (Appendix D). Data

that violated the assumptions of the statistical tests were transformed before

parametric analysis. The normal probability plots were used to guide the

transformation process. Data that had a log distribution were log transformed;

data that did not conform to a normal distribution were transformed using the

rank-it process.
16

Survival3⁄4Survival rates for the in situ study were based on the number

of live clams found at the end of the test relative to the total number of

individuals (both dead and alive) found at the end of the test. Clams were

considered ìmissingî if there was an empty space between 2 nylon cable ties,

although only 3 clams were found to be missing out of the 3000 clams deployed

in the study. Survival rates among stations were compared using a chi-squared

contingency analysis (P=0.05). A chi-square test compares the observed and

expected frequencies of animals alive or dead at the end of the test, with the null

hypothesis stating that the probability of survival is the same at all stations. If

rejected, the contingency table was partitioned to compare each station with a

mean survival less than the mean of the reference stations with expected values

to determine where differences occurred. ëExpected’ frequencies were based on

the mean of the percent survival for Reference Stations 1 and 2.

Pairwise multiple comparisons between survival values at all sites were

performed using Simes method for binomial data (Piegorsch & Bailer 1997). The

procedure is directly analogous to multiple comparisons between population

means using normal statistics. The Simes procedure includes a necessary

adjustment for using binomial data while maintaining some control over

experiment-wise error. The null hypothesis (of no difference in survival) is

rejected if the test statistic is greater than the Simes-corrected critical P-value,

which takes into account the results from the other comparisons.

Tissue Chemistry The bioaccumulation potential at Tannery Bay

stations was considered to be the component of primary interest for this study.

For this reason, the statistical design chosen for analysis of the bioaccumulation

data was one which considered the Type I pair-wise and Type II experimentwise error rates at each station. Using standard values for the pair-wise

comparisons, the station-specific rates were set at 5% for false positives (Type I

errors, a=0.05) and 20% for false negatives (Type II errors,

a=0.2). An a priori power analysis using data on the variability among replicates

for similar species and similar compounds indicated that three replicates were

sufficient to detect as low as a 50% increase over reference tissue concentrations,

for the one-tail t-test using the specified error rates. As a precaution against

possible increased variability in the chemistry data, a forth replicate has been

added to improve the confidence with which a 50% difference can be detected.

These power results were used to approximate the power of the planned

multiple contrasts.

For tissue chemistry data, the concentrations of chromium, lead, and

mercury across all stations failed to fit a normal distribution. However, each of

these trace elements came within reasonable bounds of a normal distribution

when log-transformed. Cadmium, chromium, lead, and mercury were not

normal after calculated as content. The first three were corrected through logtransformation, though mercury required rank-it transformation to correct for

one data point which lay significantly outside of the bounds of the normal

distribution.
17

Bonferroni’s multiple contrasts test was used for the post hoc comparisons

for the tissue chemistry data because of its ability to account for the number of

means being tested against the two references. Because two reference stations

were used in this study, the hypothesis comparing each Tannery Bay station to

ìreferenceî is represented by the following equation:

μsite1 = 1/2(μref1 + μref2) .

The pair-wise error rate was set at 0.05 as an upper boundary.

Clam Growth Metrics3⁄4Among the clam measurement data, tissue

weights were normally distributed, end-of-test whole-animal wet weight

required log-transformation, and growth rates based on weight needed to be

transformed using rank-its to comply with statistical assumptions for the

ANOVA.

Dunnett’s multiple comparisons tests were used for the post hoc

comparisons for the clam growth data. The Dunnett’s test was used for these

data rather than the Bonferroni test because of the high level of replication (i.e.,

n=284) available for each growth metric and the extreme robustness of the

Dunnett’s test.

2.8.2 Temperature

Water temperatures were taken at 8 study sites and 2 reference stations in

12-min intervals over a period of approximately 55 days (7/17/97−9/9/97).

Temperature data were downloaded from the logging devices using the

instruments’ data recovery software. The start and end of the temperature series

at some sites were dropped so that all series would be of equal length and

covered the same time period. Minimum, maximum, and mean temperatures

were calculated for each station. Temperature profiles were generated for each

station and used to identify overall temperature trends. Temperature

differences among reference and treatment stations were investigated using

statistical approaches to test two primary hypotheses:

1. There is no difference in mean temperature across stations, and

2. There is no difference in the range of temperatures across stations.

Before testing for differences in mean temperatures across stations, it was

necessary to test for autocorrelations, a measure of the dependence between
18

observations of the same series. The temperature series for all stations showed

very strong trend and cyclical autocorrelations, requiring a non-standard

analysis of mean differences. To reduce variability and autocorrelation, each

series was reduced to daily mean temperatures, then a pair-wise station analysis

was performed on the differences between the daily means at each site. This

analysis requires the assumption that the trend in the daily averages is similar

across stations. These series of mean differences were then regularly

subsampled at a frequency determined by the autocorrelation function. For

example, if the series of differences in daily means was autocorrelated to lag 6,

an essentially independent set of observations was generated by choosing every

7th time point. The extent of the autocorrelation varies in the mean difference

series; therefore, to achieve equal sample sizes across sites the maximum

significant autocorrelation was used to subsample all sites. The observed pattern

of differences in daily mean temperatures can be used to determine whether one

station was consistently warmer than another; if the differences were not

distinguishable from zero, then the two stations are said to have similar daily

mean temperatures. The data were reduced to 16 sets of independent

observations describing pair-wise differences in temperature between two

reference sites and eight study sites. These 16 sets were tested for differences

from zero using one-sample t-tests, with two-tailed alpha levels of 0.05.

To assess the effects of temperature conditions on clam growth,

temperature ranges over 1-week periods were evaluated. First, the minimum

weekly temperature was subtracted from the maximum weekly temperature at

each station, resulting in eight observations of temperature range per station.

These series were not significantly autocorrelated, and the variances were

approximately equal across stations. Normality was assessed by plotting a

histogram and quantile plot for residuals from an initial ANOVA fit. There was

one large outlier (Reference Station 2, 7/17/97 6:48) which may have too large an

influence on the results. With this outlier removed and the ranges recalculated,

the data were approximately log-normal. A one-way ANOVA was performed to

test for differences between the log-transformed ranges.

3.0 Results

The in situ bioaccumulation study with caged clams was completed as proposed.

Clams were deployed on July 16 and 17, 1997 and retrieved 55 days (7.85 weeks)

later from all field stations on September 9 and 10, 1997. All cages were in

excellent condition upon retrieval. There were no signs of predation or

vandalism. In general, the clams were in very good condition. A few

individuals had broken or eroded shells.

Appendix B contains detailed data reports for tissue chemistry; Appendix C

contains the laboratory operating procedures: Appendix D contains tissue

chemistry and growth statistical analyses; Appendix E contains the data reports

for clam whole-animal wet weight, growth rates, and tissue weights. Appendix

F contains a series of photographs depicting the sampling events and activities.
19

3.1 Data Quality Review

All data collected as part of the baseline clam monitoring study were subjected

to data quality review to ensure that the data met the project quality objectives

and were suitable for analysis and interpretation. The data-quality parameters

used to assess the acceptability of the data were precision, accuracy,

representativeness, comparability, and completeness.

3.1.1 Tissue Chemistry Data

The chemistry data package received from Brooks Rand consisted of 40

tissue samples and three filter blank samples. All data were acceptable as

reported and were considered usable. Data qualified J were considered usable

as estimates. A summary of the data review is provided in this section. All

data-quality objectives for this project (Table 2) were met with the exceptions

discussed below. Chemicals reported as undetected were included in statistical

calculations using a value of one-half of the reported detection limit.

Arsenic, Chromium, Cadmium, Lead 3⁄4A method blank was digested

with each batch of samples submitted for metals. In addition, continuing

calibration blanks were analyzed for every 10 samples. No target analytes were

detected with the exception of chromium. Low levels of chromium were

detected in two preparation blanks (0.62 μg Cr/L each) and two continuing

calibration blanks (0.47 μg Cr/L each). The levels detected in the blanks were

less than 5 times the target detection limit. Since the values detected in the

associated samples were greater than 5 times the amount detected in the blanks,

the results for chromium were not affected. A matrix spike and a certified

reference material were analyzed with each batch, and all results were within

the specified control limits. A sample duplicate was analyzed with each batch

and the results met the established control limit.

Mercury, Methylmercury3⁄4A method blank was digested with each batch

of samples submitted for total mercury and methylmercury. In addition,

continuing calibration blanks were analyzed for every 10 samples. No target

analytes were detected in any of the blanks. A matrix spike and a certified

reference material were analyzed with each batch, and all results were within

the specified control limits. A sample duplicate was analyzed with each batch

and the results met the established control limit.
20

3.1.2 Growth Data

All clam whole-animal wet-weight, tissue-weight, and growth-rate data

are considered usable for the purpose of this report. The remeasurement process

indicated that field staff were consistent in the measurement technique and that

the error associated with those measurements was well within the 5% deviation

as described in the Field Sampling Plan. No data were considered outliers;

therefore, none were excluded from the data set.

Growth rates (mg/wk) were calculated as:

 (Measurementfinal − Measurementinitial)/7.85.

Growth rates were calculated for individuals using the beginning- and

end-of-test whole-animal wet-weight data. In some cases, negative values

appear for growth rates. A loss in whole body weight can be attributed to

adverse conditions or measurement error.

3.2 Survival

Survival was moderately high, ranging from 77% to 97% for all cages (Figure 4;

Table 3). Average survival by station ranged from 87% to 95%. The survival

data were analyzed for differences among stations using a contingency table.

Station 5, with a significantly lower percentage of animals surviving, was the

only treatment station that differed significantly from the average of the

reference clams (Table 3). Survival of individual cages at Station 5 ranged from

77% to 96%, a difference of 19% among cages. Survival at other stations varied

only 6% on average among the four cages. Results of the within-Tannery Bay

comparisons using the Simes procedure indicated that Stations 5 and 8 were the

only two bay stations which differed significantly from each other in percent

survival.

3.3 Tissue ChemistryóConcentration and Content

The concentrations of all trace elements measured in clam tissues are expressed

as dry weight. The results presented for each station represent the average of

the four replicated samples for that station. For each trace element, the

concentration results (Table 4) and the content results (Table 5) are presented.

The end-of-test tissue chemistry results were statistically analyzed as follows: a)

Tannery Bay stations (for each station, n=4) were compared with the 2 reference

stations (n=8); b) Tannery Bay stations were compared against each other, and c)

all stations (n=4 for each) were compared against the initial tissue chemistry

measurements made on the 4 composited samples from the 300 T0 clams. The

results of statistical comparisons on tissue concentration are provided in Table 6;

results for statistical comparisons on tissue content are provided in Table 7.
21

3.3.1 Arsenic

Clams at all stations, including the references, contained lower

concentrations of arsenic at the end of the test than the average initial

concentration of 6.25 mg/kg (Figure 5a; Tables 4, 6). Clams from Stations 4, 7,

and 9 contained significantly less arsenic in their tissues than the T0 clams.

Average arsenic concentrations by station ranged from 5.04 to 5.92 mg/kg dry

weight. The lowest mean concentration was detected in clams at Station 9 and

the highest concentration was found in clams at Station 8. No significant

differences (P=0.05) were detected between arsenic concentrations measured in

any of the treatment station clams and the reference station clams. Similarly, no

significant differences in arsenic concentration were detected among Tannery

Bay stations when compared with one another (Table 6).

Arsenic content ranged from 0.62 μg in clams at Station 1 to 0.82 μg in

clams at Station 8. The end-of-test arsenic content was significantly higher in

clams at Stations 3, 6, and 8 than the initial arsenic content of 0.63 μg (Figure 5b;

Table 5). Clams from these stations, as well as Station 7, also had significantly

higher arsenic contents than the 0.65 μg average of clams at the reference stations

(Table 7). Clams at Stations 4, 5, 9, and 10, while not statistically significant, had

higher arsenic contents than the average of the reference clams. Results of the

within-Tannery Bay comparison (Table 7) indicated the following statistical

differences in end-of-test arsenic contents:

Station 8  Station 4, 5, 10.

3.3.2 Cadmium

Cadmium concentrations in end-of-test clams ranged from 2.23 to 3.40

mg/kg dry weight (Figure 6a, Table 4). None of these concentrations were

significantly different from the average concentration of 3.06 mg/kg dry weight

measured in T0 clams (Table 6). At the end of the deployment, clams at Station 8

had a cadmium concentration of 3.40 mg/kg dry weight, which was

significantly higher than the average concentration of the reference clams (Table

6). Although the cadmium concentration in clams at Stations 5, 6, and 10 were

slightly higher than the average of the reference stations, the increase was not

statistically significant. The results of the within-Tannery Bay comparison

indicated cadmium concentrations in clams at Station 8 (3.40 mg/kg dry weight)

were significantly higher than for clams at Station 4 (2.26 mg/kg dry weight).

Among the Tannery Bay stations, only clams at Stations 4 and 8 differed from

each other in cadmium concentration (Table 6).

Cadmium content ranged from 0.25 μg at Station 1 to 0.47 μg at Station 8

(Table 5). At the end of the study, clams at Station 8 contained significantly more

cadmium than the initial content of T0 clams (Figure 6b; Table 5) and

significantly more cadmium per individual than the average of the reference
22

stations (Table 7). Results of the within-Tannery Bay comparison indicated

cadmium content for clams at Station 8 was significantly different from clams at

Stations 4, 5, 6, 9, and 10 (Table 7).

3.3.3 Total Chromium

All Tannery Bay clams accumulated chromium during the deployment

period when compared with the initial concentration of 2.74 mg/kg dry weight

(Figure 7a; Table 4). At the end of the study, clams at the reference stations had

an average chromium concentration of 7.04 mg/kg dry weight. This average

concentration was significantly lower than that measured in clams from Stations

4, 5, 6, 7, and 8 in Tannery Bay (Table 6). The highest chromium concentrations

were measured in clams from Station 5 (70.23 mg/kg dry weight) and Station 8

(49.90 mg/kg dry weight); the lowest concentration measured in Tannery Bay

clams was 9.47 mg/kg dry weight (Station 10). Results of the within-Tannery

Bay comparison (Table 6) indicated that clams at Stations 5 and 8 had similar

chromium concentrations, but these were significantly higher than

concentrations measured in other Tannery Bay stations.

Historical concentrations of chromium in sediments indicate that the

highest concentrations of chromium on the site are located between Stations 4

and 5 and range between 15,000 and 31,000 mg/kg dry weight (U.S. EPA/ ERT

1995). Clams from Station 4 had the third-highest and those from Station 5 had

the highest chromium concentrations at the site. Clams from Station 8, where

historical concentrations of chromium in the sediments are about 7,600†mg/kg

dry weight, had the second highest concentration among all Tannery Bay

stations.

Clams from all reference and Tannery Bay stations had significantly

higher total chromium content per organism when compared with the initial

content of 0.28 μg (Figure 7b; Table 5). The chromium content in Tannery Bay

clams ranged from 1.19 μg at Station 10 to 8.36 μg at Station 5. Clams at the

reference stations accumulated the least amount of chromium, with an average

content of 0.81 μg. Clams at Tannery Bay stations 3 through 8 had significantly

higher chromium contents than the average of the reference stations (Table 7).

Results of the within-Tannery Bay comparison (Table 7) indicated the following

statistical differences in chromium content:

Station 5  Stations 3, 4, 6, 7, 9, 10

Station 8  Stations 3, 4, 7, 9, 10

Station 10  Stations 3, 4, 5, 6, 7, 8.
23

3.3.4 Lead

Concentrations of lead in clams from the reference and Tannery Bay

stations were significantly higher when compared with the average initial

concentration of 0.244 mg/kg dry weight (Figure 8a; Table 4). The lead

concentration in clams from Tannery Bay ranged from 0.64 to 1.68 mg/kg dry

weight (Stations 3 and 5, respectively); the concentration in clams at the

reference station averaged 0.89 mg/kg dry weight. Concentrations of lead in

clams from Tannery Bay Stations 4, 5, 6, 8, and 10 were greater than the average

of the reference stations, but these differences were not statistically significant

(Table 6). Results of the within-Tannery Bay comparison indicated lead

concentration in clams at Station 5 (1.68 mg/kg dry weight) was significantly

higher than for clams at Station 3 (0.64 mg/kg dry weight). There were no

differences in lead concentration among the other Tannery Bay stations (Table 6).

The lead content in all clams was significantly higher at the end of the

study when compared with the initial content of 0.03 μg (Figure 8b; Table 5).

Clams at Stations 4, 5, and 8 had the highest lead contents. Clams from all

Tannery Bay stations, except Station 3, had higher lead contents than the average

of the reference clams; however, the differences were not statistically significant

(Table 7). Results of the within-Tannery Bay comparison indicated lead content

in clams at Station 5 (0.20 μg) was significantly higher than for clams at Station 3

(0.09 μg). There were no differences in lead contents among the other Tannery

Bay stations (Table 7).

3.3.5 Total Mercury

At the end of the study, all clams had a lower total mercury concentration

when compared with the initial concentration of 1.26 mg/kg dry weight (Figure

9a; Table 4); the difference was statistically significant for clams from Stations 2,

6, and 7. For clams deployed in Tannery Bay, the highest mercury

concentration, 1.100 mg/kg dry weight, was measured in clams at Station 9.

Clams at Stations 4, 5, and 9 had mercury concentrations that were greater than

the average of the reference stations (Table 4), but none of these were

significantly higher than the average of the reference stations (Table 6). No

significant differences in mercury concentration were detected among Tannery

Bay stations when compared with one another (Table 6).

End-of-test total mercury content was not significantly different than

initial content for clams at any station (Figure 9b; Table 5). Only clams at

Stations 4 and 9 had final mercury contents higher than the initial content of

0.128 μg, but neither of these were significantly higher than the initial content.

The lowest mercury content, 0.108 μg, was measured in clams at Station 10.

Only clams at Station 4 had a mercury content that was significantly higher than

the average of the clams at the reference stations (Table 7). The content value for
24

clams at Station 9 is not significantly greater than the average of the reference

clams. This is because, although the mean content at Station 9 appears larger

than Station 4 (Figure 9b), one replicate with a very large content caused the

large mean and variance and skewed the distribution. When analyzing the

rank-it transformed data, the other three replicates within Station 9, which lie

directly around the mean of the references, were more influential in determining

significance. No significant differences in mercury content were detected

among Tannery Bay stations when compared with one another (Table 7).

3.3.6 Methylmercury

End-of-test concentrations of methylmercury in clams from all stations

were significantly lower than the average initial concentration of 0.259 mg/kg

dry weight (Figure 10a; Tables 4, 6). End-of-test methylmercury concentrations

ranged from 0.102 to 0.183†mg/kg dry weight. Tissues of clams at Stations 3, 4,

and 5 contained significantly higher concentrations of methyl-mercury when

compared with the average of the reference clams. Clams at Stations 7, 9, and 10

had methylmercury concentrations that were slightly, but not significantly,

higher than the average of the reference clams. Clams at Reference Station 2 had

the lowest methylmercury concentration measured at all stations. Results of the

within–Tannery Bay comparison (Table 6) indicated the following statistical

differences in tissue methylmercury concentrations:

Station 8  Station 3, 4, 5

Station 4  Stations 6, 7, 8, 9, 10.

End-of-test methylmercury content in clam tissues was significantly lower

than the initial content of 0.026 μg at all stations except 3 and 4 (Figure 10b;

Table 5). The highest methylmercury contents, 0.023 to 0.025 μg, were found in

clams from Stations 3 and 4, but these were not significantly different than the

initial content. At the end of the study, clams at Stations 3, 4, 5, 6, 7, and 9 all

had significantly higher methylmercury contents than the average of the

reference clams (Table 7). Station 8 was the only Tannery Bay station with a

methylmercury content that was below 0.015 μg, the average content of the

reference clams. Results of the within–Tannery Bay comparison on

methylmercury content (Table 7) indicated the following statistical differences:

Station 3  Station 8, 10

Station 4  Stations 5, 6, 7, 8, 9, 10.
25

3.3.7 Trace Element Bioavailability

The stations were ranked according to their relative degree of bioavailable

trace elements. The increase in trace element content in clams was used as an

indicator of bioavailability. For each trace element, the amount of trace element

uptake was weighted by dividing the end-of-test content by the initial content.

The quotients from each of the five trace elements were then summed for each

station. The quotients calculated for each station are summarized in Table 8. By

using this weighted ranking process, Station 5 appears to have the most

bioavailable trace elements, followed by Station 8 and Station 4. The reference

stations had the least amount of bioavailable trace elements, followed by Stations

10 and 9. The following ranked order, from stations with the most to the least

bioavailable trace elements, resulted from this analysis:

Sta 5 > Sta 8 > Sta 4 > Sta 6 > Sta 7 > Sta 3 > Sta 9 > Sta 10 > Sta 2 > Sta 1.

3.4 Clam Growth Metrics

Two metrics were used to assess growth: whole-animal wet weight and end-oftest tissue weight. Only whole-animal wet weight was measured for each

individual at both the beginning and end of the test. Therefore, the only growth

rates based on changes (i.e., increase or decrease) in whole-animal wet weights

could be calculated. Initial tissue weights were determined only for the T0 clams

sampled at the start of the test for chemical analysis. Because there was no

statistical difference in the whole-animal weight of clams among individual

cages (including the clams used for the initial tissue-weight determinations and

chemical analyses) at the start of the test, it was assumed that the average tissue

weight was also similar among all cages. Based on this assumption, the end-oftest tissue weights were evaluated for statistical differences; any differences

observed were assumed to have occurred during the test period. Appendix E

contains the actual weight measurements made during the field study.

Descriptive statistics were calculated for the various growth metrics and are

summarized in Table 9. The end-of-test values are provided for each of these

metrics; the absolute change after the 55-day exposure period is provided only

for the whole-animal wet-weight data.

3.4.1 Whole-Animal Wet Weight

At the start of the test, whole-animal wet weights by individual ranged

from 4.01 to 7.95†g; mean whole-animal wet weight by station was ∼5.5 g. Endof-test whole-animal wet weights by individual ranged from 3.44 to 8.29 g.

Mean end-of-test whole-animal weights by station ranged from 5.56 to 5.76 g.

The lowest end-of-test whole-animal wet weights were found for clams at

Reference Station 1; the highest for clams at Tannery Bay Stations 6 and 7 (Figure

11; Table 9).
26

The clams at Reference Stations 1 and 2 had the lowest increase in all

growth metrics evaluated after the 55-day exposure. Clams at Station 1, the

Waiska Bay site, had the poorest growth. The data for the two reference stations

were compared statistically to determine the utility of the reference data in

subsequent comparisons. The results of that comparison indicated that, based

on growth rates and end-of-test tissue weights, the clams at Reference Station 1

were significantly smaller than those at Reference Station 2. However, data for

both reference stations were retained as a point of comparison for clams exposed

to relatively uncontaminated conditions even though clam growth was less than

expected.

The end-of-test whole-animal wet-weight data were suitable for an

ANOVA after log transformation. Results of the Dunnett’s multiple range test

indicated that clams at Stations 3, 4, 6 and 7 were, on average, significantly

heavier than those at the reference stations (Figure 11; Table 10). There were no

significant differences in end-of-test whole-animal wet weights among Tannery

Bay stations (Table 10).

Growth rates based on whole-animal wet weight were calculated from the

initial and end-of-test data. The lowest mean growth rate by station was 5.16

mg/week, measured for clams at Reference Station 1; the highest mean growth

rate of 28.04 mg/week was measured for clams at Station 6 (Figure 12; Table 10).

On an individual basis, the minimum growth rate was -80.15 mg/week and the

maximum growth rate was 99.24 mg/week. The growth rate data required a

rank-it transformation before testing with the ANOVA and Dunnett’s test.

Results of these analyses indicated that growth rates at Stations 3, 4, 6, 7, 8, 9,

and 10 were significantly higher than those at the reference stations. Clams at

Station 5 were the only animals that grew less than the average of the reference

clams. Results of the within-Tannery Bay comparison (Table 10) indicated the

following statistical differences in growth rates:

Station 3 ≠ Stations 4, 5, 6, 8, 9, 10

Station 4 ≠ Stations 3, 5, 6, 7, 9

Station 5 ≠ Stations 3, 4, 6, 7, 8, 9, 10

Station 6 ≠ Stations 3, 4, 5, 7, 8, 10

Station 7 ≠ Stations 4, 5, 6, 8, 9, 10

Station 8 ≠ Stations 3, 5, 6, 7, 9

Station 9 ≠ Stations 3, 4, 5, 7, 8, 10

Station 10 ≠ Stations 3, 5, 6, 7, 9.

Stations 4, 8, and 10 had similar growth rates, as did the following pairs:

Stations 3 and 7, and 9 and 6. Clams at Station 5 had a significantly lower

growth rate (9.57 mg/week) than clams at all other stations in Tannery Bay.
27

3.4.2 End-of-Test Tissue Weights

Mean tissue weight at the start of the test by station was estimated at 0.66

g wet weight. This estimate was based on the tissue weights measured for the

300 animals used for test initiation (T0) tissue-chemistry analyses (Table 10).

Mean end-of-test tissue weights by station ranged from 0.74 to 0.92 g wet

weight, the overall range for individuals was 0.34 to 1.71†g wet weight (Figure

13; Table†10). The lowest mean tissue weights were measured in clams

deployed at Reference Station 1 and Station 5. The end-of-test tissue-weight data

were suitable for analysis with an ANOVA and Dunnett’s multiple comparison

without transformation. Results of these analyses indicated that the average

end-of-test tissue weight for the reference stations was significantly lower than

tissue weights for clams at all treatment stations, with the exception of Station 5.

End-of-test tissue weights for clams at Station 5 were statistically similar to the

average of the reference clams (Table 10). Results of the within-Tannery Bay

comparison (Table 10) indicated the following statistical differences in tissue

weights:

Station 3 ≠ Stations 4, 5, 7, 8, 9, 10

Station 4 ≠ Stations 3, 5, 10

Station 5 ≠ Stations 3, 4, 6, 7, 8, 9, 10

Station 6 ≠ Stations 5, 10

Station 7 ≠ Stations 3, 5, 10

Station 8 ≠ Stations 3, 5, 10

Station 9 ≠ Stations 3, 5, 10

Station 10 ≠ Stations 3, 4, 5, 6, 7, 8, 9.

Stations 4, 6, 7, 8, and 9 had similar tissue weights, as did stations 3 and 6.

3.4.3 Percent Lipids

Clams from all stations contained slightly higher percentages of lipids

than the 1.30% found in T0 clam tissues (Table 9). Station 9 clams had a

significantly greater percentage of lipids than the average of the reference station

clams (Figure 14). Clams from the other Tannery Bay stations had slightly more

lipids per mass than the average of clams at the reference stations, but

percentages were not statistically different. Results of the within-Tannery Bay

comparison indicated no differences in percent lipids among clams at any of the

stations (Table 10).
28

3.4.4 Percent Solids

Clams at Reference Station 2 and Tannery Bay Stations 5 and 10 had lower

percentages of solids in their tissues at the end of deployment than T0 clams

(Figure 15). All the end-of-test values were significantly similar to the 15.2%

solids measured in the T0 clams (Table 9). Clams at Stations 6, 7, and 9 had

significantly higher percentages of solids than the reference station clams. Only

clams at Station 5 had a slightly lower percentage than the reference stations.

Results of the within-Tannery Bay comparison indicated that Station 5 clams had

a significantly lower percentage of solids in tissues than clams at Station 7 (Table

10).

3.5 Temperature

Water temperatures at each station were recorded at approximate 12-min

intervals over the 55-day exposure period using one in situ computerized data

logger per station (HoboTemp, Onset Instruments). Data were downloaded

from the logging devices using the instruments’ data-recovery software.

Minimum, maximum, and mean temperatures for each station at the depth of

the cages are summarized in Table 11. Reference Station 1 had a higher

minimum, maximum, and mean temperature than all other stations over the

deployment period, while Station 5 had the lowest minimum and mean

temperature. The actual temperature profiles (Figure 16) show that the

remaining eight stations follow similar patterns and seem to lie in approximately

the same range.

The temperature data were statistically analyzed to determine whether the

apparent differences were significant. The following two null hypotheses were

tested:

1. There is no difference in daily average temperature across stations;

2. There is no difference in the range of temperatures across stations.

3.5.1 Testing for Differences in Mean Temperature

Temperatures at all stations displayed similar patterns with daily and

seasonal cycles (Figure 16), although Reference Station 1 had a higher average

temperature and treatment Station 5 had a lower average temperature than the

other stations. The temperature series for all stations showed very strong

autocorrelations (a measure of dependence between observations of the same

series), requiring a non-standard analysis of mean differences. To reduce

variability and autocorrelation, each series was reduced to daily mean

temperatures (Figure 17), then an analysis of pairwise station differences was

performed using one-sample t-tests (two tailed; P=0.05) to determine if there

were statistical differences in daily average temperatures among stations. The
29

results of the t-tests on paired data (Table 12) show that the mean daily

temperature for Reference Station 1 is significantly warmer than all study sites.

The mean temperature for Reference Station 2 is significantly warmer than

Station 5, and significantly colder than Stations 7, 8, and 10. Comparisons of

mean daily temperature between Tannery Bay stations showed that several

treatment stations also differed significantly from each other (Table 12).

3.5.2 Testing for Differences in Temperature Range

To assess the effects of temperature conditions on clam growth,

temperature ranges over 1-week periods were evaluated. This time interval was

selected because 7 days is a manageable time period, as opposed to comparisons

based on an hourly or daily basis, and it is expected to have some biological

relevance. Weekly intervals are also commonly used to measure changes in

environmental conditions and growth in aquatic organisms.

The results of the one-way ANOVA performed to test for differences

between temperature ranges indicate a significant difference between the

average weekly temperature ranges at all stations (Table 13). The results of the

Newman-Keuls Multiple Range test to determine which stations differed from

which other stations indicated the weekly range in temperature at Reference

Station 1 was significantly smaller than at all other stations (P=0.05). There is no

evidence that the range of temperatures at Reference Station 2 is different from

that at the study sites.

3.6 Sediment and Surface Water Chemistry vs. Tissue Chemistry

Results of chemical analyses performed on surface water collected by

HydroQual at the beginning and end of test, and sediment samples collected at

the end of the test are summarized in Tables 14 and 15. Sediments were also

collected at the beginning of the test and analyzed for methyl- and total mercury.

The end-of-test (EOT) sediment chemistry values were compared with the

lowest effect level (LEL) values developed by the Ontario Ministry of

Environment (1993) as a means of ranking the stations for relative toxicity. For

each trace element, the concentration measured in the sediment was divided by

its corresponding LEL value. The quotients of the five measured trace elements

(excluding methylmercury, since there was no LEL value) were summed by

station and provide a relative estimate of the severity of sediment contamination

(Table 16).

For example, LEL quotients <1 for a single contaminant indicate low risk from

that contaminant; therefore, a sum of LEL quotients <5 would equate to low risk

at the station based on the 5 trace elements measured; potential additive effects
30

of toxicity were not taken into account. Reference Stations 1 and 2 had the

lowest Sums of Quotients, both < 5. The highest Sums (820 and 720,

respectively, from Stations 3 and 4) were from sediments situated between the

peninsula forming Tannery Point and the small island. Sediments in this area

also have the highest amount of TOC at 11.7% and 12.4%, a potential source of

binding ligands for the uncomplexed trace elements. The next highest Sums of

Quotients were found for Stations 5, 6, 7, and 8, ranging between 161 and 423.

The TOC concentration at each of these stations, except Station 5, was about half

of that measured at Stations 3 and 4. TOC at Station 5 was similar to TOC at

Stations 3 and 4. Although the Sums of Quotients from Tannery Bay were

lowest at Stations 9 and 10 (40.52 and 51.96, respectively), chromium

concentrations exceeded their LEL value at these stations. A TOC of <1% at

Stations 9 and 10 may have reduced potential binding sites for trace elements

resulting in lower concentrations at these stations. TOC at Reference Stations 1

and 2 was also <1%.

End-of-test sediment and surface-water data were compared with the tissue

chemistry data, and correlation analyses (Table 17) were used to determine the

strength of the relationship between these variables.

For non-detect values, one-half the detection limit was used. The strongest

relationships were seen for chromium in surface water and clam tissues and

methylmercury in sediment and tissue (Table 17). The concentration of

chromium in clam tissues was better correlated with the chromium in surface

water (r=0.62) than chromium in sediments (r=0.27). This is not surprising

because the clams are filter feeders, and although placed directly on top of the

sediments, they actively take in copious quantities of particulate material

associated with the water column during the normal filtration process. These

correlations suggest that the clams are obtaining chromium from particulates

associated with the water column. The limited number of paired data points

used in these analyses may alone drive a stronger correlation. The tissue and

surface-water correlation used only 5 data points, and the tissue and sediment

comparison used only 10.

The correlation coefficients for total mercury in water, sediment, and tissue were

low (Table 17). The strongest correlation for methylmercury was for sediment

and tissue (r=0.68). The correlation coefficients for arsenic, cadmium, and lead

among the different media were very poor (Table 17). No correlation

coefficients could be calculated for cadmium and lead for the water:sediment

and water:tissue comparisons because for both cadmium and lead, the

concentration in each surface-water sample collected at the four stations was

reported as “less than” the detection limit, resulting in insufficient data to

perform correlation analyses.
31

3.7 Tissue Chemistry vs. Survival and Clam Growth Metrics

The concentration of each trace element measured in clam tissue was compared

with survival, whole-animal wet weight, growth rates, and end-of-test tissue

weights (both wet and dry). All correlation coefficients were very low (Table

18), although there was a high degree of variability.

3.8 Temperature vs. Clam Growth

Temperature was compared with survival, whole-animal wet-weight, growth

rates, and end-of-test tissue weights (both wet and dry). For each comparison,

there was a high degree of variability and all correlation coefficients were very

low (Table 19). Positive relationships were found for growth rates and survival;

negative relationships were found for tissue weights (both wet and dry). These

results suggest that none of the clam growth metrics are strongly correlated with

temperature.

4.0 Discussion

The baseline biomonitoring study was successfully completed as proposed and

the project-specific objectives were met. All cages were retrieved; high survival

permitted assessments of chemical uptake and adverse effects. Clams at most of

the Tannery Bay stations accumulated significant amounts of chromium when

compared with reference clams. All clams increased in both soft-tissue weights

and whole-animal wet weights after the 55-day exposure period; however,

compared with reference clams, Tannery Bay clams did not demonstrate any

significant growth effects due to exposure conditions. This discussion will focus

on the interpretation of the tissue chemistry results when evaluated in light of

the sediment and surface-water chemistry and the utility of growth metrics as

indicators of effects.

4.1 Meeting the Purpose and Objectives of the Study

The purpose of the monitoring program is to document whether the selected

remedy for the site is effective at reducing concentrations of bioavailable trace

elements in Tannery Bay. This purpose is achieved by meeting the specific

objectives of this study: 1) Determine whether chromium, total mercury,

methylmercury, lead, cadmium, and arsenic in Tannery Bay sediments are

available to biota residing in and/or using the Bay, and 2) determine whether

exposure to bioavailable concentrations of metals may have adverse effects on

local biota.

The concentrations of trace elements measured in the soft tissues of clams after

the 55-day deployment provide a baseline of trace-element bioavailability for

filter-feeding organisms that dwell within the surficial sediments or on top of

these sediments.
32

4.2 Survival of Deployed Clams

Clam survival was very good at 92% which ensured sufficient tissues for the

chemical analyses and sufficient individuals for assessment of effects. Although

survival is usually not a very discriminating metric to evaluate adverse effects

unless physical conditions (i.e., temperature, salinity, DO) are outside the

normal range for the species, or toxic materials are present at extremely high

concentrations, survival can provide a means of quickly identifying hot spots

and prioritizing exposure conditions.

Based on mean survival by station, Station 5 appears to be the only station where

exposure conditions may be deleterious. However, survival by cage within

Station 5 is variable: two cages had low survival rates (77% and 81%; Table 3)

and two had high survival (96% and 93%), comparable to other Tannery Bay

stations. No other Tannery Bay station had such high variability in survival

rates among cages at a single station. High variability in survival at Station 5

may be due to environmental heterogeneity. The American Corbicula has a

preference for lotic conditions commonly found in shallow, well-oxygenated

shore lake habitats (Aldridge & McMahon 1978, McMahon 1979). In native lotic

habitats, C. fluminea is able to inhabit a wide variety of substrata, including bare

rock, loose gravel, sand, and even silt and mud (Horne & McIntosh 1979). This

species is nearly always eliminated from areas with decreasing sand, mud, or silt

sediments of high organic and low oxygen content (Aldridge & McMahon 1978,

Eng 1979, Fast 1971, Lenat & Weiss 1973, McMahon 1979). Station 5 was located

at the furthest end of Tannery Bay in a highly vegetated area. It is possible that

two of the cages were situated on top of decaying plant material, subjecting

clams to high organics and low dissolved-oxygen conditions.

Percent survival in this study is comparable to survival reported for this species

in other studies. For example, in a field study conducted to evaluate thermal

plumes, survival of reference clams ranged from 93.5% to 99.6% (Foe & Knight

1987); survival of clams exposed to the thermal plumes ranged from 2% to

95.5%.

4.3 Tissue Chemistry

Changes in trace element concentration and content were used to assess

bioavailability. The concentration data are useful for comparisons with previous

or other studies. The change in trace-element content, or actual mass, in the clam

is a direct measure of uptake, and provides an indication of exposure to

organisms higher in the food chain. In this study, arsenic bioavailability was

discovered only by analysis of the content data.
33

4.3.1 Tissue Concentration

The results of this study indicate that bioavailable chromium is present at

all Tannery Bay stations. Although clams at Stations 9 and 10 accumulated the

least amount of chromium, the end-of-test concentrations in clams at these

stations were greater than initial concentrations. Clams at Stations 5 and 8

accumulated the most chromium, with an increasing gradient in tissue

concentration from Stations 3 and 4 to 5.

The results for total and methylmercury are difficult to interpret due to

the high concentration present in clams at the beginning of the test. C. fluminea

collected from the Saline River in Arkansas for this study contained 1.263 μg/g

dry weight (0.193 μg/g wet weight) total mercury compared with total mercury

of 0.10-0.2 μg/g dry weight in Corbicula collected in other studies (Leland and

Scudder 1990; Elder and Mattraw 1984). Unfortunately, the beginning-of-test

tissue samples were frozen and not analyzed until the end-of-test. Therefore,

there was no indication until the end of the study that the initial mercury

concentration was high. Clams at all stations had lower end-of-test mercury

concentrations when compared with initial concentrations. Although it is

difficult to use the mercury tissue-chemistry data to establish true baseline

conditions, they may be useful in establishing trends or ranking areas within

Tannery Bay. Total mercury concentrations were highest at stations 4, 5, and 9.

Methylmercury concentrations were highest at Stations 3, 4, and 5. Whether the

differences noted in mercury concentrations within Tannery Bay are due to

differential depuration among stations, differential uptake among stations, or

some combination of these mechanisms cannot be determined from this study.

Clams at Stations 4, 5, and 8 had the highest lead concentrations.

However, clams at all stations, including the reference stations, increased their

lead concentration over the duration of the study. The lack of a statistically

significant difference between reference and Tannery Bay stations suggests that

lead contamination is not restricted to Tannery Bay.

By evaluating only the tissue-chemistry concentration data, arsenic and

cadmium do not appear to be bioavailable in Tannery Bay. Except for cadmium

at Station 8, end-of-test concentrations for both arsenic and cadmium were lower

than those measured at the beginning of the test.

4.3.2 Tissue Content

The content data normalize the tissue chemistry with respect to clam

growth, allowing comparisons of uptake unbiased by differences in tissue mass

at the end of the test. The trends in the tissue content data are similar to those

identified for the tissue concentration data, with one notable exception. The

content data show that arsenic and cadmium were both bioavailable to clams.
34

Clams at Stations 3, 6, 7, and 8 accumulated significantly more arsenic than the

average of the reference stations, with clams at Station 8 having the highest

arsenic content. Cadmium content in clams at Stations 2 and 8 were significantly

higher than the initial content. Station 8 cadmium content was significantly

higher than the average of the reference stations.

Based on content, the clams at Station 3 also accumulated significant

amounts of chromium compared with the average of the reference clams. For

total mercury, clams at Station 4 had a statistically significant accumulation

based on content. Clams at all Tannery Bay stations, except Stations 8 and 10,

had significantly higher methylmercury contents compared with the average of

the reference clams. However, content data for both total and methylmercury

must be interpreted with the knowledge that initial values were higher than in

the test area, as discussed in Section 4.3.1.

The bioavailability of arsenic and cadmium was not evident from analysis

of the tissue concentration data alone. Although the clams accumulated arsenic

and cadmium, they grew enough to maintain concentrations similar to, or

slightly lower than, the initial concentrations, indicating that growth dilution did

occur.

For predatory species, it is the content or dose (i.e., the quantifiable

amount of a material introduced into an animal (Rand and Petrocelli 1985)) in

food sources that is significant with respect to potential adverse effects. The

toxicity of a metal is determined by the dose at the receptor site. The primary

difference between concentration and content is that concentration allows for

common reporting of a contaminant per unit weight of the animal, whereas

content is an indication of the total amount of contaminant available within the

animal. Thus, for arsenic and cadmium, there appeared to be no concern when

only the tissue concentration data were examined; however, by evaluating the

content data it is evident that these trace elements are available for uptake and

could enter the food chain through organisms resident in Tannery Bay.

4.4 Sediment and Surface-Water Chemistry

Both sediment and surface-water samples were collected during clam

deployment and retrieval. The sediment deployment samples were analyzed

only for total- and methylmercury and conventional parameters (e.g., grain size,

TOC, etc.). Sediment retrieval samples were analyzed for all study trace

elements. These data indicate high variability in the sediment chemistry data, as

well as in the composition of sediments. The area is heterogeneous, with wide

fluctuations in the amount of fine-grained material and TOC present.

Chromium and lead concentrations were highly correlated with TOC (r=0.94 and

r=0.92, respectively). Chromium and lead concentrations also correlated with

percent fines (r=0.80 and r=0.75, respectively). The association of metals with

these fine organic-rich materials helps explain some of the spatial variability in

sediment chemistry.
35

Surface waters for one reference and four Tannery Bay stations were analyzed

from both the deployment and retrieval samples. Except for chromium and

methylmercury, the correlation analyses indicated poor relationships between

water and sediment chemistry. However, because of the small surface-water

sample size, results from these correlation analyses must be used cautiously;

small sample size alone may drive a stronger correlation. The correlation for

chromium suggests that the unfiltered surface water over sediments has

proportionate amounts of chromium, most likely associated with the particulate

material within the water column.

4.5 Comparison of Bioavailability and Sediment Contamination

To assess the relative bioavailability of all five trace elements measured for clams

at different stations, quotients calculated from the end-of-test tissue content

divided by the initial tissue-content data were summed for five contaminants at

each station (Table 8). Stations were ranked according to degree of uptake as

follows:

Ranked order based on tissue quotients from greatest contaminant uptake to

least uptake:

Sta 5 > Sta 8 > Sta 4 > Sta 6 > Sta 7 > Sta 3 > Sta 9 > Sta 10 > Sta 2 > Sta 1.

This ranked order is somewhat different than the station rankings calculated for

sediments based on exceedance of the Ontario LEL values (Table 16).

Ranked order based on sediment LEL quotients from most contaminated to least

contaminated:

Sta 3 > Sta 4 > Sta 5 > Sta 6 > Sta 7 > Sta 8 > Sta 10 > Sta 9 > Sta 1 > Sta 2.

The tissue and sediment rankings agree on the areas of lesser concern in Tannery

Bay (i.e., Stations 9 and 10) and the areas of modest concern (i.e., Stations 6 and

7). There is some agreement on the most contaminated areasóthose around

Stations 4 and 5. The primary differences in bioavailability and degree of

sediment contamination are Stations 3 and 8. Based on tissue chemistry, Station

8 appears to be a greater concern than Station 3; sediment chemistry suggests

that Station 3 is the area of greatest concern. The reason for this discrepancy is

uncertain, but is probably a result of several environmental factors affecting

contaminant availability discussed below. The reference stations had the lowest

concentrations of contaminants and the smallest contaminant uptake.
36

Station 3 is characterized by sediments composed primarily of fines containing

high concentrations of trace elements and TOC; bioavailability was found to be

moderate. Station 8 is characterized by sediments composed primarily of sand

and moderate-to-low concentrations of both trace elements and TOC;

bioavailability was found to be very high. Bioavailability at Station 8 may be

increased relative to sediment concentrations due to lower binding of

contaminants. Another possible explanation is tied to the apparent semicircular, northwest-to-northeast, surface-water flow in Tannery Bay. Under this

scenario, Station 3 would receive more flow from the river, whereas Station 8

would receive water that had come in contact with contaminated bay sediments

for a longer duration. Of all the areas monitored in Tannery Bay, Stations 3, 4,

and 5 have the highest TOC levels and the highest percent fines. Although both

organic carbon and fine, particulate material can serve as binding sites for labile

trace elements, the high levels of trace elements measured in clam tissue at

Stations 5 and 4 suggest that not all of the trace elements are bound and

biologically unavailable to aquatic receptors.

Clams at Station 3 may not have accumulated trace elements in proportion to

their supply in sediment due to both sediment binding and influence of water

from St. Mary’s River. A fair relationship was found between water and tissue

chemistry (r=0.62), suggesting that biologically available trace elements are

present in the water column. It is likely that the clams also accumulated

chromium from the sediments, but the weakest relationship was found between

these parameters (r=0.27). The tissue chemistry data and the correlation

coefficients suggest that clams are integrating exposure from both the sediment

and surface-water pathways, and that the contribution from each pathway is

different, depending on conditions specific to the area of deployment. The

moderate correlation coefficients obtained between sediment and tissues and

between water and tissues are probably due to uptake from both sediment and

water sources. Water circulation, and the distribution of particulate-bound trace

elements, are likely a key factor in bioavailability to the filter-feeding clams. The

beginning- and end-of-test surface-water chemistry (Table 15) clearly shows

high variability in total trace elements. At the start of the test, the highest

concentrations were found near Stations 4 and 5. Surface water was not

collected at Station 8, but data for Station 9 indicate that trace elements in surface

water were among the lowest at the start of the test. At the end of the test, the

trace-element concentrations in surface water were similar for all locations

sampled.

One unknown is the relationship between the horizon of sediment to which the

clams were exposed and the horizon of sediment used in chemical analysis.

Clams were probably exposed to trace element concentrations in the top 1-2 cm.

It is uncertain if the sediment analyzed included deeper sediments and

potentially different trace element concentrations. If surface sediments were

homogenized with slightly deeper sediments, the correlation coefficients

between tissue and sediment concentration could be lower as a consequence of

sampling technique.
37

4.6 Comparison with Previous Studies

The 1997 baseline monitoring study data corroborate the presence of sediments

in Tannery Bay contaminated with chromium and other trace elements.

Sediment chromium concentrations measured during the 1997 baseline

monitoring study are fairly consistent with data collected in 1993 (Cannelton

Ind. 1995a), 1994 (US EPA/ERT 1995), and 1995 (Cannelton Ind. 1995b). The

most comprehensive data set appears to be associated with the 1994 and 1995

sampling events. In all sampling events, the highest concentrations of chromium

were found in sediments between the mainland and the small island in the

western corner of the bay. In general, the highest concentrations are found to the

west of the small island in Tannery Bay while the lowest are along the outer

portion of Tannery Bay as it merges with the Saint Mary’s River; mid-range

concentrations are found in sediments in the eastern portion of Tannery bay.

The surficial sediments from the area surrounding the 1997 baseline monitoring

Station 4 historically have had the highest chromium concentrations: 18,430

mg/kg measured in 1993 (Cannelton Ind. 1995a), 30,000 mg/kg measured in

1994 (US EPA/ERT 1995), and 28,400 measured in 1995 in sediments collected

from an area slightly to the southeast (Cannelton Ind. 1995b). In the 1997

baseline monitoring study, the highest chromium concentration in surficial

sediments, 20,598 mg/kg, was measured in sediments collected from Station 3.

In previous studies, chromium concentrations in sediments from the vicinity of

Station 3 were reported as 1,871 mg/kg (Cannelton Ind. 1995a) and 8,200 mg/kg

(US EPA/ERT, 1995); samples collected in 1995 from an area slightly to the east

of Station 3 had a chromium concentration of 16,300 mg/kg (Cannelton Ind.

1995b). In the 1997 baseline monitoring study, the lowest chromium

concentration was measured in sediments from Station 9. Historically,

chromium concentrations in this area have been quite variable, reported as 3,014

mg/kg in 1993 (Cannelton Ind. 1995a), 5,800 mg/kg in 1994 (US EPA/ERT

1995), and 1,850 in 1995 (Cannelton Ind. 1995b). In the 1995 sampling event

(Cannelton Ind. 1995b), subsurface sediments were collected and reported to

contain chromium concentrations equal to, or higher than, those measured in the

surficial sediments. It is possible that currents and ice movement in Tannery

Bay and the Saint Mary’s River continue to move surficial sediments, causing

deeper, more contaminated sediments to become exposed. Both historical and

recent data emphasize the need for continued monitoring.

The amount of chromium accumulated by crayfish in 1994 (U.S. EPA/ERT 1995)

is similar to the amount accumulated by clams in this biomonitoring study. In

1994, tissues of crayfish from Tannery Bay were reported to contain between 1.4

and 9.6 mg Cr/kg tissue wet weight. One very high value of 29 mg/kg wet
38

weight was reported at one station from Hairball Beach (Station HB-3). The

chromium concentrations in clams deployed in Tannery Bay ranged from 1.43 to

11.24 mg/kg wet weight. The concentrations of chromium in fish tissues

measured in 1994 were within the ranges reported for both crayfish and clams.

Tissue chemistry data were collected for the mayfly Hexagenia during the

remedial pre-design studies (Cannelton Ind. 1995a). The concentration of

chromium in mayflies collected from Tannery Bay ranged from 255 to 776

mg/kg dry weight compared with dry weights of 9.49 to 70.23 mg/kg in clams.

Concentrations in mayflies are 1 to 2 orders of magnitude higher than measured

in clam tissues during this baseline study (Table 4).

In contrast to the tissue:sediment correlations for the clams in this study,

chromium concentrations in mayfly tissues were highly correlated with

sediment concentrations measured in 1994 (r=0.987). It is unclear if the mayfly

data, or even the crayfish or fish data, are directly comparable to the clam data.

Concerns include their different feeding strategy as selective sediment feeders

(mayflies actively feed on lighter, finer sediments containing higher amounts of

organic material), their duration in the sediments (up to 2 years for mayflies),

their migratory nature (none of these species remain within a specified area),

and potential changes in exposure conditions between 1993 and 1997. Filterfeeding clams and sediment-feeding mayflies receive very different exposures to

trace elements in the same sediments. Clams integrate exposure from two

media, while the sediment- dwelling mayflies reflect a narrower source. Adding

another species with a different feeding strategy (such as crayfish) to the

monitoring program would improve the dataset on availability and sediment

recovery. A sediment-feeding organism may have higher concentrations than

the filter-feeding clams. The differences portrayed by the mayfly data support

the need for a second species, particularly if information on the bioavailability of

trace elements within the upper 10 cm of sediment is required.

4.7 Growth

One component of the study was to evaluate the potential for adverse effects

associated with exposure to trace elements in Tannery Bay. The metrics used to

evaluate growth, end-of-test whole-animal wet weight, growth rates based on

whole weights, and end-of-test tissue weights did not indicate impact due to

exposure in Tannery Bay when compared with the average of the reference

stations. The data generated in this study should be used for baseline purposes.

Limited comparison should be made to growth with respect to reference clams

because of the poor growth observed in Reference Station 1 clams. Clams at

Reference Station 1 had the lowest growth of all clams; the Reference Station 2

clams had slightly better whole-animal and tissue growth than those at Station 1.

However, on average, the reference clams did not grow as well as the clams

deployed in Tannery Bay.
39

The most interesting comparisons with the growth data are those among

Tannery Bay stations only. The clams at Station 5 had the lowest performance

for each of the growth metrics evaluated. Station 5 Replicates 3 and 4, with low

survival, had very low growth (3.5 mg/week) compared with Replicates 1 and 2

(14.6 mg/week), with high survival. The replicates with high survival and

growth still had lower growth rates than any of the other Tannery Bay stations.

Growth rates, end-of-test tissue weights, and whole-animal wet weights all

decreased along a gradient across Stations 3, 4, and 5. Although no strong

relationships were found when the tissue-chemistry data were correlated with

the growth data, a very strong relationship exists between these parameters for

Stations 3, 4, and 5.

Although no significant differences were found in percent solids for the clams

after deployment, there are some trends with solids that follow those seen with

elevated tissue chemistry and reduced growth. Significant reductions in percent

solids have been associated with stress and exposure to various chemicals

(Belanger et al. 1986a,b; Doherty 1990). The clams at Station 5 had the lowest

percent solid concentration at the end of the study when compared with the

other clams. The lowest percent-solids data came from replicates 3 and 4 at

Station 5. Although the percent-solid data do not distinguish between classes of

contaminants or stressors, this metric responds in a negative fashion to any

detrimental agent. Tissues of stressed clams will have higher percentages of

water than unstressed individuals. This adds to the weight-of-evidence in

evaluating the impact of exposure conditions.

These growth-effects data will be most useful in future years by providing a

basis for comparison with other data. Significant differences in growth

parameters compared with the baseline data may reflect changes in sediment

and/or surface-water chemistry.

4.8 Temperature

Although the sites within Tannery Bay and St. Mary’s River were selected to

minimize temperature differences, statistically significant differences were

found among stations. Separating statistical significance from ecological

significance is important, but difficult. What effect, if any, do the measured

temperature differences have on the observed growth results? None of the clam

growth metrics were strongly correlated with temperature, as indicated by the

poor correlation coefficients (i.e., r<0.5) obtained when each of the growth

metrics were compared with temperature. Although there were some

differences in temperature among stations, the overall exposure conditions are

within the preferred limits (viz., 10−25°C) for this species, except at Reference

Station 1 where the temperature reached 26.3°C for a very short period.

Prolonged exposure to temperatures > 25°C have extensive effects on Corbicula

biology, including depressed filtration rates (Mattice 1979), feeding rates, and
40

reproductive capacity. When exposed to these elevated temperatures,

individuals spend most of the time with their siphons withdrawn and valves

closed (McMahon 1979). It is doubtful that the brief exposure to the high

temperature at Station 1 greatly affected the caged clams transplanted there,

although this is one concern regarding the appropriateness of Station 1 as a

reference area.

Station 5 is the only station that stands apart as having different temperatures

within Tannery Bay. The mean temperature was 3.3°C lower than the means of

the other Tannery Bay stations, and Station 5 had the lowest temperature, 10.5°C.

Groundwater discharge occurring in the wetlands in the southwest corner of

Tannery Bay possibly explains the lower water temperatures measured at this

station. The temperatures measured at Station 5 are well within the clam’s

tolerance range, although it has been noted that low temperatures may reduce

growth rates (Abbott 1979, Buttner & Heidinger 1980, Dreier & Tranquilli 1981)

and inhibit veliger release (Heinsohn 1958, Aldridge 1976, Aldridge & McMahon

1978). The lower lethal temperature limit for Corbicula is near 2°C (Mattice &

Dye 1976). Several reports of massive midwinter mortalities and/or total

extinctions have been associated with ambient water temperatures near 0°C

(Bickel 1966; Dreier & Tranquill 1981; Horning & Keup 1964).

4.9 Problems Encountered during the Study

The most significant problem encountered during this study was the presence of

mercury in clam tissues at the beginning of the test. The problem of background

contamination experienced in this and previous studies suggests that it may be

very difficult to obtain freshwater bivalves that are free of mercury

contamination. It may be necessary to obtain test specimens months in advance

of the study to allow for depuration at a location known to be contaminant-free.

The half-life of mercury depuration is approximately 90 days (N. Bloom, pers.

commun., 1998); this length of time may be necessary to remove all traces of

mercury from field-collected specimens. One of the most important elements of

future monitoring studies should be the chemical characterization of source

animals well before initiating the study.

A second problem in this study was the selection of the reference stations. The

data strongly suggest that exposure conditions, excluding chemical

contaminants, were dissimilar between the reference and Tannery Bay stations.

The physical attributes of the reference stations must be as similar as possible to

the test stations, including temperature ranges, food availability, vegetation,

water depth, and currents.
41

5.0 Recommendations

1) NOAA recommends that studies conducted in future years retain all study

parameters. Tissue chemistry, growth effects, sediment chemistry, and surfacewater chemistry are required to determine the effectiveness of the remedial

alternative. A minimum of three data sets must be collected to establish a trend

and provide sufficient information to re-evaluate the program requirements. At

that time it may be appropriate to adjust the study parameters.

2) The second round of monitoring should not occur until shore-side remedial

activities are completed.

3) Further studies should be conducted at the same time of the year to allow

direct comparison of tissue-chemistry and growth-effects data.

4) The initial mercury concentration in bivalves should be reduced. Either an

alternative source of clams should be identified, or the clams should be collected

long enough before the study commences to allow complete, or near complete,

depuration of mercury.

5) Replicate data at Station 5 was quite variable. In future years, cages placed at

this station should be located away from highly vegetated sediments to ensure

similar conditions for all clams.

6) NOAA recommends conducting a site reconnaissance to determine if a more

appropriate and representative reference station can be located to replace the

Waiska Bay Reference Station 1 for use in future years’ monitoring.

7) Although the clams integrate both sediment and water chemistry, it would be

advantageous to add a second species (i.e., crayfish) to the study to obtain

specific data on bioavailability of trace elements in the surficial sediments and to

ensure sufficient characterization of chemical bioavailability to all species (i.e.,

filter-feeding and deposit/sediment-feeding) currently or potentially using

Tannery Bay. This recommendation should be implemented to help assess food

chain impacts in the event that future year sampling data reveals no decrease in

contaminant bioavailability.
42

6.0 References

Abbott, R.T. 1979. Asiatic clam (Corbicula fluminea) vertical distributions in Dale

Hollow Reservoir, Tennessee. Proc. First Int. Corbicula Symp., p. 111-118.

Aldridge, D.W. 1976. Growth, reproduction, and bioenergetics in a natural population

of the Asiatic freshwater clam, Corbicula manilensis Philippi. Master’s Thesis, Univ.

Texas at Arlington.

Aldridge, W.E., & R.F. McMahon. 1978. Growth, fecundity, and bioenergetics in a

natural population of the freshwater clam, Corbicula manilensis Philippi, from North

Central Texas. J. Mol. Study 44:49-70.

Belanger, S.E., D.S. Cherry, & J. Cairns, Jr. 1986a. Uptake of chrysotile asbestos fibers

alters growth and reproduction of Asiatic clams. Can. J. Fish. Aquat. Sci. 43:43-52.

Belanger, S.E., J.L. Farris, D.S. Cherry, and J. Cairns. 1986b. Growth of Asiatic clams

(Corbicula sp.) during and after long-term zinc exposure in field-located and laboratory

artificial streams. Arch. Environ. Contam. Toxicol. 15:427-434.

Belanger, S., D. Cherry, J. Cairns, Jr., and M. McGuire. 1987. Using Asiatic clams as a

biomonitor for chrysotile asbestos in public water supplies. Journal AWWA - Research

and Technology pp. 69-74.

Bickel, D. 1966. Ecology of Corbicula manilensis Philippi in the Ohio River at Louisville,

Kentucky. Sterkiana 23:19-24.

Bloom, N. 1998. Personal communication, Frontier Geosciences, Inc. Seattle, March 16,

1998.

Buttner, J.K., & R.C. Heidinger. 1980. Seasonal variations in growth of the Asiatic

clam, Corbicula fluminea (Bivalvia: Corbiculidae) in a Southern Illinois fish pond.

Nautilus 94:8-10.

Cannelton Ind. 1995a. Remedial design pre-design studies. Rep. CANN 94-4 by

Cannelton Industries, Inc., Sault Ste. Marie, MI. Chicago: U.S. EPA Region V.

Cannelton Ind. 1995b. Preliminary Design Report, Cannelton Industries Site, CANN

95-4, May 1995. by Cannelton Industries, Inc., Sault Ste. Marie, MI. Chicago: U.S. EPA

Region V.

Cherry, D. 1998. Personal communication, Virginia Technical University, June 30,

1998.

Colombo, J., C. Bilos, M. Campanaro, and M. Presa. 1995. Bioaccumulation of

polychlorinated biphenyls and chlorinated pesticides by the Asiatic clam Corbicula

fluminea: Its use as sentinel organism in the Rio de La Plata Estuary, Argentina.

Environ. Sci. Technol. 29(4):914-927.

Doherty, F.G. 1990. The Asiatic clam, Corbicula spp., as a biological monitor in

freshwater environments. Environ. Monit. Assess. 15:143-181.
43

Dreier, H., & J.A. Tranquilli. 1981. Reproduction, growth, distribution, and

abundance of Corbicula in an Illinois cooling lake. Bull. Ill. Nat. Hist. Surv. 32:

 378-393.

Elder, J.G. and H.C. Mattraw. 1984. Accumulation of trace elements, pesticides, and

polychlorinated biphenyls in sediments and the clam Corbicula manilensis of the

Apalachicola River, Florida. Arch. Environ. Contam. Toxicol. 13: 453-469.

Eng, L.L. 1979. Population dynamics of the Asiatic clam, Corbicula fluminea (Muller), in

the concrete-lined Delta–Mendota Canal of central California. Proc. First Int. Corbicula

Symp., p. 39-68.

Farris, J., J. Van Hassel, S. Belanger, D. Cherry, and J. Cairns, Jr. 1988. Application of

cellulolytic activity of Asiatic clams (Corbicula sp.) to in-stream monitoring of power

plant effluents. Environ. Toxicol. Chem. 7:701-713.

Fast, A.W. 1971. The invasion and distribution of the Asiatic clam (Corbicula manilensis)

in a southern California reservoir. Bull. South. Calif. Acad. Sci. 70:91-98.

Foe, C., & A. Knight. 1987. Assessment of the biological impact of point source

discharges employing Asiatic clams. Arch. Environ. Contam. Toxicol. 16:39-51.

Heinsohn, G.E. 1958. Life history and ecology of the freshwater clam, Corbicula

fluminea. Master’s Thesis, Univ. Calif., Santa Barbara.

Horne, F.R., & S. McIntosh. 1979. Factors influencing distribution of mussels in the

Blanco River of Central Texas. Nautilus 94:119-133.

Horning, W.B., & L. Keup. 1964. Decline of the Asiatic clam in the Ohio River.

Nautilus 78:29-30.

Jones, B.R. 1996. Ecological risk management of mercury at the Cannelton Industries

Superfund Site. Memo. to Rosita Clark, RPM, U.S. EPA Region V, Oct. 7, 1996.

Kracko, K. 1992. Cannelton Industries Final Report. R. F. Weston, Inc., Edison, NJ

[unpag.].

Leland, H.V. and B.C. Scudder. 1990. Trace elements in Corbicula fluminea from the

San Joaquin River, California. Sci. Total Environ. 97/98:641-672.

Lenat, D.R., & C.M. Weiss. 1973. Distribution of benthic macroinvertebrates in Lake

Wylie North Carolina—South Carolina. Publ. 331, Dep. Environ. Sci. & Eng., School of

Public Health, Univ. North Carolina at Chapel Hill.

Luoma, S., N. R. Dagovitz, and E. Axtmann. 1990. Temporally intensive study of trace

metals in sediments and bivalves from a large river-estuarine system: Suisan

Bay/Delta in San Francisco Bay. Sci. Total Environ. 97/98:685-712.

Mac, M., C. Edsall, R. HesselBerg, and R. Sayers Jr. 1984. Flow-through bioassay for

measuring bioaccumulation of toxic substances from sediment. Final Report. Great

Lakes National Program Office, U.S. Environmental Protection Agency, Contribution

No. 616 of the Great Lakes Fishery Laboratory.
44

McMahon, R.F. 1979. Response to temperature and hypoxia in the oxygen

consumption of the introduced Asiatic freshwater clam Corbicula fluminea (Muller).

Comp. Biochem. Physiol. A 63:383-388.

McMahon, R.F. 1991. Mollusca: bivalvia. In: J.H. Thorp and A.P. Covich, Eds. Ecology

and Classification of North American freshwater Invertebrates. San Diego: Academic

Press. p 315-399.

Mattice, J.S. 1979. Interactions of Corbicula sp. With power plants. Proc. First Int.

Corbicula Symp., p. 119-138.

Mattice, J.S., & L.L. Dye. 1976. Thermal tolerance of adult Asiatic clam. ERDA Symp.

Ser. 40:130-135.

NOAA/EVS Consultants. 1997. Quality assurance project plan for development and

implementation of bivalve monitoring study: Cannelton Industries site − Sault Ste.

Marie, Michigan. Chicago: U.S. EPA Region V.

Ontario Ministry of Environment. 1993. Guidelines for the protection and

management of aquatic sediment quality in Ontario. Ottawa: Ontario Ministry of

Environment, August 1993.

Piegorsch, W.W., & A.J. Bailer. 1997. Statistics for environmental biology and

toxicology. London: Chapman and Hall.

Rand, G. M. and S. R. Petrocelli. 1985. Fundamentals of aquatic toxicology.

Hemisphere Publishing Corporation, New York. Page 653

Riisgård, H.U.T., & S. Hansen. 1990. Biomagnification of mercury in a marine grazing

food-chain: Algal cells Phaeodactylum tricornutum, mussels Mytilus edulis and flounders

Platichthys flesus studied by means of a stepwise-reduction-CVAA method. Mar. Ecol.

Prog. Ser. 62:259-270.

Salazar, M.H., & S.M. Salazar. 1995. In-situ bioassays using transplanted mussels. I.

Estimating chemical exposure and bioeffects with bioaccumulation and growth, p. 216-

241. In: Hughes, J.S., G.R. Biddinger, and E. Mones (eds.), Third symposium on

environmental toxicology and risk assessment. ASTM STP 1218. Philadelphia:

American Society for Testing and Materials.

Tatem, H. 1986. Bioaccumulation of polychlorinated biphenyls and metals from

contaminated sediment by freshwater prawns, Macrobrachium rosenbergii and clams,

Corbicula fluminea. Arch. Environ. Contam. Toxicol. 15:171-183.

U.S. EPA. 1994. Cannelton Industries, Inc: Site Description, Threats and

Contaminants, Cleanup Approach, and Environmental Progress. May 1994, 2 p.

U.S. EPA. 1996. Amended Record of Decision. ìCannelton Industries Siteî [unpag.]

U.S. EPA/ERT. 1995. Final Report. Ecological Risk Assessment, Cannelton Industries

Site, Sault Ste. Marie, Michigan. Environmental Response Branch, Emergency Response

Division, Office of Emergency and Remedial Response. January 1995, 93 p. + figs.

WW Engineering. 1991. Remedial investigation of Cannelton Industries site, Sault Ste.

Marie, MI. Proj. #04002, Sept. 1991.
7.0 TABLES
Table 1. Deployment position, time, water depth, and range of depth

at each station.

Station

Cage

numbers

Deployment

time

GPS

coordinates

Water

depth (ft)

Range of

depth (ft)

1

(Ref 1)

13, 22, 25, 43 7/16; 2:30pm 46o26'30.60"N

84o35'54.31"W

2' 6" 2'1" - 3'6"

2

(Ref 2)

5, 15, 24, 35 7/17;10:45am 46o29'21.51"N

84o24'03.37"W

2' 5" 2' - 3'5"

3 2, 11, 30, 37 7/16; 5:50pm 46o29'34.54"N

84o23'24.33"W

3' 6" 3'1" - 4'6"

4 3, 17, 23, 34 7/16; 7:00pm 46o29'32.94"N

84o23'23.72"W

2' 7" 2'2" - 3'7"

5 4, 18, 27, 42 7/16; 7:15pm 46o29'30.74”N

84o23'23.45”W

1' 9" 1'4" - 2'9"

6 14, 19, 26, 41 7/16; 7:30pm 46o29'32.34”N

84o23'19.23”W

1' 7" 1'2" - 2'7"

7 1, 9, 20, 38 7/17; 11:07am 46o29'31.89”N

84o23'15.05”W

2' 9" 2'4" - 3'9"

8 16, 28, 33, 44 7/16; 6:20pm 46o29'36.56”N

84o23'12.14”W

4' 6" 4'1" - 5'6"

9 8, 10, 21, 39 7/17: 10:08am 46o29'35.39”N

84o23'17.62”W

3' 8" 3'3" - 4'8"

10 6, 12, 31, 40 7/17; 10:20am 46o29'37.08”N

84o23'23.45”W

3' 2" 2'7" - 4'2"

11

(Initial tissue)

7, 29, 32, 36 NA NA NA NA

NA - Not applicable

Table 2. Analyte list and targeted detection limits for clam tissues.

Analyte Method Target detection limit*

Chromium (total) EPA 200.9 STP-GFAA 0.01 mg/kg

Cadmium EPA 200.9 STP-GFAA 0.005 mg/kg

Lead EPA 200.9 STP-GFAA 0.07 mg/kg

Arsenic EPA 200.9 STP-GFAA 0.05 mg/kg

Total Mercury BR-0002 CVAFS 0.0001 mg/kg

Methylmercury BR-0011 CVAFS 0.001 mg/kg

Percent Solids BR-1501 0.1%

Percent Lipids EPA 8290 1.0%

* Detection limits are not guaranteed due to the possibility of matrix interferences

STP-GFAA − Stabilized temperature platform-graphite furnace atomic absorption

CVAFS − Cold vapor atomic fluorescence spectrometry

BR − Brooks Rand
Table 3. End-of-test percent survival for clams deployed in Tannery Bay

and at reference stations.

Sta 1 Sta 2 Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Replicate 1 85 93 95 96 96 93 91 95 95 96

Replicate 2 96 95 88 87 93 97 92 95 95 91

Replicate 3 95 95 88 92 77 92 87 97 92 93

Replicate 4 93 91 93 85 81 96 97 92 92 89

Mean 92 94 91 90 87 94 92 95 94 92

SD 5.0 1.9 3.6 5.0 9.2 2.4 4.1 2.1 1.7 3.0

N 277 280 273 270 261 284 275 284 280 277

Results of statistical analyses on clam survival.

Tannery Bay stations compared with the average of reference stations

Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Survival NS NS -- NS NS NS NS NS

-- Clams from Tannery Bay station significantly less than the average of reference stations.

NS − No significant difference between Tannery Bay station and the average of reference stations.
Table 4. Mean concentration (dry and wet weights) of trace elements in clam

tissues.

Dry Weight Concentration (mg/kg)

Initial Sta 1 & 2a Sta 1 Sta 2 Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Arsenic

Rep 1 6.07 6.09 4.68 5.75 4.63 4.67 4.82 5.44 5.14 5.04 5.45

Rep 2 6.25 4.78 6.01 4.53 5.41 5.48 5.00 4.73 5.76 4.45 5.33

Rep 3 6.56 5.82 5.56 5.99 5.00 6.47 5.98 5.30 6.52 5.43 5.37

Rep 4 6.12 5.79 5.41 4.89 5.17 6.52 5.90 4.95 6.26 5.22 5.15

 Mean 6.25 5.52 5.62 5.42 5.29 5.05 5.79 5.43 5.11 5.92 5.04 5.33

±2SE 0.22 0.53 0.58 0.55 0.69 0.33 0.88 0.60 0.32 0.61 0.42 0.13

Cadmium

Rep 1 3.19 2.61 2.81 3.10 1.91 2.44 1.99 2.54 2.92 2.47 2.83

Rep 2 3.15 1.78 3.35 2.01 2.60 2.63 2.09 2.47 3.22 2.17 2.82

Rep 3 2.74 2.44 3.64 3.01 2.25 2.91 2.81 2.52 3.97 2.53 3.19

Rep 4 3.15 2.08 2.93 2.36 2.29 3.15 3.97 2.56 3.48 2.55 2.72

 Mean 3.06 2.71 2.23 3.18 2.62 2.26 2.78 2.72 2.52 3.40 2.43 2.89

±2SE 0.21 0.62 0.37 0.38 0.52 0.28 0.31 0.91 0.04 0.44 0.18 0.21

Chromium

Rep 1 2.38 6.51 6.31 17.80 18.10 62.20 14.50 26.20 34.30 8.83 7.92

Rep 2 2.77 4.48 4.68 20.80 32.80 79.20 17.50 16.30 19.20 12.50 7.12

Rep 3 2.92 13.00 5.69 17.50 9.10 82.20 19.60 17.60 101.00 13.30 14.70

Rep 4 2.90 8.77 6.87 13.10 40.80 57.30 22.60 17.70 45.10 24.80 8.13

 Mean 2.74 7.04 8.19 5.89 17.30 25.20 70.23 18.55 19.45 49.90 14.86 9.47

±2SE 0.25 2.76 3.65 0.94 3.17 14.27 12.32 3.42 4.54 35.68 6.91 3.52

Lead

Rep 1 0.620 0.895 1.570 0.778 0.800 1.450 0.568 0.663 0.879 0.822 0.826

Rep 2 0.026 0.460 0.887 0.426 2.770 1.730 1.460 0.872 0.779 0.702 0.973

Rep 3 0.165 0.764 0.997 0.554 0.925 2.190 0.879 0.903 2.260 0.988 1.070

Rep 4 0.165 0.625 0.920 0.807 1.050 1.360 1.170 0.698 1.530 0.994 0.805

 Mean 0.244 0.890 0.686 1.094 0.641 1.386 1.683 1.019 0.784 1.362 0.877 0.919

±2SE 0.259 0.326 0.187 0.321 0.183 0.928 0.373 0.383 0.121 0.685 0.141 0.126

Mercury

Rep 1 0.993 1.210 0.793 0.830 0.885 0.932 0.827 0.644 0.697 0.879 0.781

Rep 2 1.660 0.858 0.771 0.876 0.995 1.030 0.844 0.814 1.090 0.783 0.873

Rep 3 1.060 1.130 0.877 0.862 0.981 1.260 0.678 0.987 0.792 1.930 0.853

Rep 4 1.340 1.100 0.893 0.894 1.040 1.020 0.675 0.810 1.030 0.807 0.926

 Mean 1.263 0.954 1.075 0.834 0.866 0.975 1.061 0.756 0.814 0.902 1.100 0.858

±2SE 0.304 0.167 0.152 0.060 0.027 0.065 0.140 0.092 0.140 0.188 0.555 0.060

Methylmercury

Rep 1 0.255 0.149 0.121 0.153 0.171 0.153 0.146 0.116 0.086 0.139 0.125

Rep 2 0.243 0.105 0.077 0.162 0.180 0.124 0.143 0.146 0.097 0.141 0.135

Rep 3 0.267 0.201 0.093 0.136 0.157 0.197 0.113 0.159 0.102 0.143 0.131

Rep 4 0.269 0.185 0.105 0.176 0.223 0.151 0.100 0.103 0.123 0.137 0.134

 Mean 0.259 0.130 0.160 0.099 0.157 0.183 0.156 0.126 0.131 0.102 0.140 0.131

±2SE 0.012 0.045 0.043 0.019 0.017 0.028 0.030 0.023 0.026 0.016 0.003 0.005
Table 4 (continued)

Wet Weight Concentration (mg/kg)

Initial Sta 1 & 2a Sta 1 Sta 2 Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Arsenic

Rep 1 0.91 0.93 0.68 0.89 0.76 0.73 0.78 0.92 0.85 0.79 0.84

Rep 2 0.97 0.73 0.88 0.77 0.82 0.88 0.80 0.74 0.88 0.72 0.80

Rep 3 0.98 0.89 0.84 0.87 0.81 1.04 0.98 0.82 1.02 0.87 0.81

Rep 4 0.94 0.89 0.81 0.79 0.76 1.05 0.95 0.85 0.94 0.84 0.77

 Mean 0.95 0.83 0.86 0.80 0.83 0.79 0.93 0.88 0.83 0.92 0.81 0.80

±2SE 0.03 0.09 0.09 0.09 0.06 0.03 0.15 0.10 0.08 0.08 0.07 0.03

Cadmium

Rep 1 0.48 0.40 0.41 0.48 0.32 0.38 0.32 0.43 0.48 0.39 0.44

Rep 2 0.49 0.27 0.49 0.34 0.40 0.42 0.33 0.39 0.49 0.35 0.42

Rep 3 0.41 0.37 0.55 0.44 0.36 0.47 0.46 0.39 0.62 0.41 0.48

Rep 4 0.48 0.32 0.44 0.38 0.34 0.51 0.64 0.44 0.52 0.41 0.41

 Mean 0.46 0.41 0.34 0.47 0.41 0.35 0.45 0.44 0.41 0.53 0.39 0.44

±2SE 0.04 0.09 0.06 0.06 0.06 0.03 0.05 0.15 0.03 0.06 0.03 0.03

Chromium

Rep 1 0.36 1.00 0.91 2.74 2.99 9.77 2.35 4.43 5.66 1.39 1.23

Rep 2 0.43 0.69 0.69 3.52 4.99 12.75 2.80 2.54 2.94 2.01 1.07

Rep 3 0.44 1.99 0.86 2.56 1.47 13.23 3.21 2.73 15.86 2.14 2.21

Rep 4 0.44 1.34 1.02 2.11 6.00 9.23 3.64 3.04 6.77 3.99 1.21

 Mean 0.42 1.06 1.25 0.87 2.73 3.86 11.24 3.00 3.19 7.80 2.38 1.43

±2SE 0.04 0.43 0.56 0.14 0.59 2.02 2.04 0.55 0.85 5.60 1.12 0.52

Lead

Rep 1 0.09 0.14 0.23 0.12 0.13 0.23 0.09 0.11 0.15 0.13 0.13

Rep 2 0.00 0.07 0.13 0.07 0.42 0.28 0.23 0.14 0.12 0.11 0.15

Rep 3 0.05 0.12 0.15 0.08 0.15 0.35 0.14 0.14 0.35 0.16 0.16

Rep 4 0.05 0.10 0.14 0.13 0.15 0.22 0.19 0.12 0.23 0.16 0.12

 Mean 0.05 0.13 0.10 0.16 0.10 0.21 0.27 0.16 0.13 0.21 0.14 0.14

±2SE 0.04 0.05 0.03 0.04 0.03 0.14 0.06 0.06 0.01 0.11 0.02 0.02

Mercury

Rep 1 0.149 0.185 0.115 0.128 0.146 0.146 0.134 0.109 0.115 0.138 0.121

Rep 2 0.257 0.131 0.113 0.148 0.151 0.166 0.135 0.127 0.167 0.126 0.131

Rep 3 0.159 0.173 0.132 0.126 0.159 0.203 0.111 0.153 0.124 0.311 0.128

Rep 4 0.205 0.168 0.133 0.144 0.153 0.164 0.109 0.139 0.155 0.130 0.138

 Mean 0.193 0.144 0.164 0.123 0.136 0.152 0.170 0.122 0.132 0.140 0.176 0.129

±2SE 0.050 0.028 0.023 0.011 0.011 0.005 0.024 0.014 0.019 0.024 0.090 0.007

Methylmercury

Rep 1 0.038 0.023 0.018 0.024 0.028 0.024 0.024 0.020 0.014 0.022 0.019

Rep 2 0.038 0.016 0.011 0.027 0.027 0.020 0.023 0.023 0.015 0.023 0.020

Rep 3 0.040 0.031 0.014 0.020 0.025 0.032 0.019 0.025 0.016 0.023 0.020

Rep 4 0.041 0.028 0.016 0.028 0.033 0.024 0.016 0.018 0.018 0.022 0.020

 Mean 0.039 0.020 0.024 0.015 0.025 0.028 0.025 0.020 0.021 0.016 0.022 0.020

±2SE 0.002 0.007 0.007 0.003 0.004 0.003 0.005 0.004 0.003 0.002 0.001 0.000

aValue represents average of data (n=8) for Reference Stations 1 and 2
Table 5. Mean content (μg dry weight) of trace elements in clam tissues.

Content (μg dry weight)

Initial Sta 1 & 2a Sta 1 Sta 2 Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Arsenic

Rep 1 0.62 0.62 0.58 0.79 0.67 0.58 0.72 0.82 0.77 0.72 0.70

Rep 2 0.65 0.64 0.75 0.73 0.70 0.69 0.74 0.67 0.78 0.62 0.65

Rep 3 0.66 0.60 0.69 0.81 0.74 0.73 0.87 0.71 0.92 0.77 0.67

Rep 4 0.60 0.64 0.67 0.72 0.64 0.72 0.81 0.73 0.82 0.72 0.67

 Mean 0.63 0.65 0.62 0.67 0.76 0.69 0.68 0.79 0.73 0.82 0.71 0.67

±2SE 0.02 0.05 0.02 0.07 0.05 0.04 0.07 0.07 0.06 0.07 0.07 0.02

Cadmium

Rep 1 0.33 0.27 0.35 0.43 0.27 0.30 0.30 0.38 0.44 0.35 0.36

Rep 2 0.33 0.24 0.42 0.32 0.33 0.33 0.31 0.35 0.44 0.30 0.34

Rep 3 0.27 0.25 0.45 0.41 0.33 0.33 0.41 0.34 0.56 0.36 0.40

Rep 4 0.31 0.23 0.36 0.35 0.29 0.35 0.54 0.38 0.46 0.35 0.35

 Mean 0.31 0.32 0.25 0.40 0.38 0.31 0.33 0.39 0.36 0.47 0.34 0.36

±2SE 0.02 0.09 0.02 0.05 0.05 0.03 0.02 0.11 0.02 0.06 0.03 0.02

Chromium

Rep 1 0.24 0.66 0.78 2.45 2.61 7.73 2.18 3.97 5.16 1.26 1.02

Rep 2 0.29 0.60 0.58 3.36 4.22 10.04 2.61 2.32 2.60 1.74 0.86

Rep 3 0.29 1.35 0.71 2.37 1.34 9.31 2.85 2.35 14.18 1.90 1.83

Rep 4 0.29 0.97 0.85 1.93 5.09 6.36 3.09 2.62 5.90 3.40 1.05

 Mean 0.28 0.81 0.89 0.73 2.53 3.31 8.36 2.68 2.81 6.96 2.07 1.19

±2SE 0.02 0.25 0.34 0.11 0.60 1.67 1.64 0.39 0.78 5.02 0.92 0.43

Lead

Rep 1 0.063 0.091 0.195 0.107 0.115 0.180 0.085 0.100 0.132 0.117 0.106

Rep 2 0.003 0.061 0.111 0.069 0.356 0.219 0.217 0.124 0.106 0.098 0.118

Rep 3 0.016 0.079 0.124 0.075 0.136 0.248 0.128 0.120 0.317 0.141 0.133

Rep 4 0.016 0.069 0.114 0.119 0.131 0.151 0.160 0.103 0.200 0.136 0.104

 Mean 0.03 0.11 0.08 0.14 0.09 0.18 0.20 0.15 0.11 0.19 0.12 0.12

±2SE 0.027 0.043 0.013 0.040 0.024 0.115 0.043 0.056 0.012 0.094 0.020 0.013

Mercury

Rep 1 0.102 0.124 0.099 0.114 0.127 0.116 0.124 0.098 0.105 0.125 0.101

Rep 2 0.172 0.114 0.096 0.142 0.128 0.131 0.126 0.116 0.148 0.109 0.106

Rep 3 0.106 0.117 0.109 0.117 0.145 0.143 0.099 0.132 0.111 0.275 0.106

Rep 4 0.132 0.121 0.111 0.131 0.130 0.113 0.092 0.120 0.135 0.111 0.120

 Mean 0.128 0.111 0.119 0.104 0.126 0.132 0.126 0.110 0.116 0.125 0.155 0.108

±2SE 0.032 0.010 0.004 0.007 0.013 0.008 0.014 0.017 0.014 0.020 0.080 0.008

Methylmercury

Rep 1 0.026 0.015 0.015 0.021 0.025 0.019 0.022 0.018 0.013 0.020 0.016

Rep 2 0.025 0.014 0.010 0.026 0.023 0.016 0.021 0.021 0.013 0.020 0.016

Rep 3 0.027 0.021 0.012 0.018 0.023 0.022 0.016 0.021 0.014 0.020 0.016

Rep 4 0.026 0.020 0.013 0.026 0.028 0.017 0.014 0.015 0.016 0.019 0.017

 Mean 0.026 0.015 0.018 0.012 0.023 0.025 0.018 0.018 0.019 0.014 0.020 0.017

±2SE 0.001 0.004 0.003 0.002 0.004 0.002 0.003 0.004 0.003 0.001 0.001 0.001

aValue represents average of data (n=8) for Reference Stations 1 and 2
Table 6. Results of statistical analyses on tissue concentration data.

Tannery Bay stations compared with the average of reference stations

Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Arsenic NS NS NS NS NS NS NS NS

Cadmium NS NS NS NS NS * NS NS

Chromium NS * * * * * NS NS

Lead NS NS NS NS NS NS NS NS

Mercury NS NS NS NS NS NS NS NS

Methylmercur

y

* * * NS NS -- NS NS

* Concentration in clams from Tannery Bay station significantly greater than the average of reference stations.

NS − No significant difference between Tannery Bay station and the average of reference stations.

-- Concentration in clams from Tannery Bay station significantly less than the average of reference stations.

All Stations compared with the Initial (T0) concentration

Sta 1 Sta 2 Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Arsenic NS NS NS -- NS NS -- NS -- NS

Cadmium NS NS NS NS NS NS NS NS NS NS

Chromium * NS * * * * * * * *

Lead * * * * * * * * * *

Mercury NS -- NS NS NS -- -- NS NS NS

Methylmercur

y

-- -- -- -- -- -- -- -- -- --

* Concentration in clams from station significantly greater than the initial (T0) concentration.

NS - No significant difference between station and the initial (T0) concentration.

-- Concentration in clams from station significantly less than the initial (T0) concentration.

Results of Student Newman-Keuls analyses on Tannery Bay stations

Arsenic Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .814270 .584874 .935425 .637188 .495301 .911501 .928815

Sta 4 .430691 .869236 .893374 .311926 .964431 .894614

Sta 5 .361812 .420663 .730462 .476945 .471481

Sta 6 .841382 .420587 .910960 .798480

Sta 7 .317988 .982237 .838171

Sta 8 .340642 .432228

Sta 9 .942486

Cadmium Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .665661 .862052 .763521 .757503 .126046 .816730 .822549

Sta 4 .565403 .602881 .686484 .02436* .596451 .433798

Sta 5 .830683 .838204 .141291 .789479 .733573

Sta 6 .812403 .155535 .797992 .841996

Sta 7 .091184 .769555 .763650

Sta 8 .063363 .117045

Sta 9 .683025
Table 6 (continued).

Log-transformed

Chromium Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .846750 .00100* .812555 .922308 .04041* .476774 .098294

Sta 4 .00166* .834543 .670226 .03548* .549013 .063644

Sta 5 .00122* .00113* .093466 .00032* .00015*

Sta 6 .886829 .04532* .606781 .103420

Sta 7 .03528* .688880 .113172

Sta 8 .01085* .00056*

Sta 9 .162674

Log-transformed

Lead Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .098554 .00935* .391874 .361751 .102810 .363678 .401195

Sta 4 .416405 .348370 .377600 .922398 .523952 .480659

Sta 5 .140419 .060593 .246678 .119946 .134218

Sta 6 .815750 .550275 .906747 .831228

Sta 7 .407054 .652333 .786808

Sta 8 .585958 .589559

Sta 9 .837986

Rank-it

transformed

Mercury Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .728777 .494554 .438258 .585298 .994971 .932098 .752391

Sta 4 .560977 .181286 .352135 .564255 .502584 .658985

Sta 5 .069875 .162117 .385769 .424959 .399499

Sta 6 .602263 .552391 .435239 .460747

Sta 7 .748399 .660360 .504001

Sta 8 .728451 .943398

Sta 9 .904760

Methylmercury Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .089930 .973275 .308626 .423846 .01550* .500263 .329013

Sta 4 .190474 .01073* .01939* .00039* .03636* .01444*

Sta 5 .256465 .337308 .01273* .280296 .225946

Sta 6 .711838 .120665 .758777 .919554

Sta 7 .138031 .815107 .986674

Sta 8 .103081 .215748

Sta 9 .557576

Values in bold face and marked with an asterisk indicate a significant difference between stations.
Table 7. Results of statistical analyses on tissue content data.

Tannery Bay Stations compared with the average of reference stations

Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Arsenic * NS NS * * * NS NS

Cadmium NS NS NS NS NS * NS NS

Chromium * * * * * * NS NS

Lead NS NS NS NS NS NS NS NS

Mercury NS * NS NS NS NS NS NS

Methylmercury * * * * * NS * NS

* Content in clams from Tannery Bay station significantly greater than the average of reference stations.

NS − No significant difference between Tannery Bay station and the average of reference stations.

-- Concentration in clams from Tannery Bay station significantly less than the average of reference stations.

All Stations compared with the Initial (T0) content

Sta 1 Sta 2 Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Arsenic NS NS * NS NS * NS * NS NS

Cadmium NS NS NS NS NS NS NS * NS NS

Chromium * * * * * * * * * *

Lead * * * * * * * * * *

Mercury NS NS NS NS NS NS NS NS NS NS

Methylmercur

y

-- -- NS NS -- -- -- -- -- --

* - Content in clams from station significantly greater than the initial (T0) content.

NS - No significant difference between station and the initial (T0) content.

--Content in clams from station significantly less than the initial (T0) content.

Results of Student Newman-Keuls analyses on Tannery Bay stations

Arsenic Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .246178 .294896 .567017 .479323 .329379 .356169 .232615

Sta 4 .935554 .123708 .463488 .02674* .608212 .924048

Sta 5 .140279 .581636 .02906* .820743 .768725

Sta 6 .409248 .390203 .222626 .099445

Sta 7 .159087 .501585 .522781

Sta 8 .060453 .01858*

Sta 9 .805475

Log-transformed

Cadmium Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .271655 .623085 .883704 .935928 .052864 .732871 .750743

Sta 4 .438111 .260652 .272000 .00216* .479573 .352153

Sta 5 .627829 .541491 .01082* .703402 .695554

Sta 6 .959430 .02906* .762610 .886242

Sta 7 .065513 .500424 .979693

Sta 8 .02008* .04653*

Sta 9 .759936
Table 7 (continued)

Log-transformed

Chromium Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .929033 .00375* .802568 .931000 .04635* .398803 .03103*

Sta 4 .00395* .933628 .808083 .02598* .593180 .02991*

Sta 5 .00485* .00404* .228600 .00072* .00015*

Sta 6 .915009 .053327 .516024 .03141*

Sta 7 .03848* .620461 .03736*

Sta 8 .00914* .00025*

Sta 9 .075181

Log-transformed

Lead Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .124241 .03979* .330186 .354026 .104362 .555812 .540986

Sta 4 .724440 .479289 .451652 .835989 .397792 .410296

Sta 5 .459243 .213493 .580128 .256272 .214819

Sta 6 .760396 .628120 .552991 .671570

Sta 7 .419832 .923403 .901421

Sta 8 .435976 .404338

Sta 9 .800440

Rank-it

transformed

Mercury

Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .592114 .961570 .647329 .905831 .999189 .997012 .630697

Sta 4 .825743 .384487 .720227 .959687 .925465 .382022

Sta 5 .599712 .844918 .996174 .979763 .565254

Sta 6 .711649 .438136 .520619 .921914

Sta 7 .469784 .710685 .495380

Sta 8 .953808 .343351

Sta 9 .461216

Methylmercury Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .338606 .102697 .133255 .080469 .00140* .092543 .02270*

Sta 4 .01893* .02323* .01710* .00027* .03042* .00305*

Sta 5 .956651 .888703 .112302 .791600 .558412

Sta 6 .979007 .074222 .892308 .333662

Sta 7 .123403 .612682 .642834

Sta 8 .058875 .199605

Sta 9 .454670

Values in bold face and marked with an asterisk indicate a significant difference between stations.
Table 8. Quotients derived by dividing end-of-test tissue content by

initial tissue content.

As Cd Cr Pb Hg Sum

Sta 1 0.990 0.797 3.23 3.041 0.931 9.0

Sta 2 1.068 1.283 2.648 5.51 0.812 11.3

Sta 3 1.209 1.218 9.127 3.738 0.986 16.3

Sta 4 1.086 0.992 11.97 7.473 1.036 22.6

Sta 5 1.081 1.064 30.19 8.075 0.982 41.4

Sta 6 1.246 1.264 9.691 5.977 0.863 19.0

Sta 7 1.163 1.174 10.17 4.536 0.910 18.0

Sta 8 1.302 1.528 25.14 7.64 0.975 36.6

Sta 9 1.120 1.104 7.49 4.977 1.213 15.9

Sta 10 1.062 1.177 4.302 4.67 0.846 12.1
Table 9. Descriptive statistics on clam growth metrics.

Initial

(T0)

Sta 1 Sta 2 Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Initial Mean 5.45 5.53 5.52 5.52 5.58 5.49 5.55 5.58 5.46 5.49 5.51

WAWW Min. 4.01 4.02 4.04 4.01 4.02 4.10 4.07 4.04 4.02 4.01 4.02

(g) Max. 7.79 7.90 7.93 7.92 7.95 7.79 7.89 7.91 7.75 7.75 7.85

SD 0.83 0.84 0.84 0.88 0.88 0.79 0.83 0.88 0.80 0.85 0.82

±2SE 0.10 0.10 0.10 0.10 0.10 0.09 0.10 0.10 0.09 0.10 0.09

End-of-test Mean 5.56 5.62 5.71 5.72 5.58 5.76 5.76 5.58 5.70 5.63

WAWW Min. 3.98 4.03 4.20 4.15 4.03 4.12 4.15 4.13 3.44 4.30

(g) Max. 7.98 8.11 8.06 8.06 7.95 7.83 8.09 7.77 8.28 8.29

SD 0.82 0.81 0.86 0.85 0.79 0.83 0.88 0.79 0.86 0.81

±2SE 0.10 0.10 0.10 0.10 0.10 0.10 0.11 0.09 0.10 0.10

 WAWW Mean 0.04 0.11 0.18 0.14 0.08 0.22 0.19 0.15 0.21 0.15

(g) Min. -0.39 -0.60 -0.25 -0.45 -0.55 -0.18 -0.21 -0.63 -0.58 -0.15

Max. 0.31 0.36 0.57 0.78 0.39 0.56 0.55 0.70 0.58 0.46

SD 0.09 0.11 0.12 0.12 0.11 0.12 0.12 0.13 0.11 0.09

±2SE 0.01 0.01 0.02 0.02 0.01 0.02 0.01 0.02 0.01 0.01

WAWW Mean 5.16 14.49 22.49 17.92 9.57 28.04 24.26 19.25 27.24 18.56

Growth Min. -49.62 -76.34 -31.81 -57.25 -69.97 -22.90 -26.72 -80.15 -73.79 -19.08

(mg/wk) Max. 39.44 45.80 72.52 99.24 49.62 71.25 69.97 89.06 73.79 58.52

SD 11.80 14.17 15.31 15.49 14.63 15.56 14.77 16.40 14.51 11.18

±2SE 1.42 1.69 1.85 1.88 1.81 1.85 1.78 1.95 1.73 1.34

End-of-test Mean 0.66 0.74 0.84 0.92 0.87 0.81 0.90 0.88 0.89 0.88 0.83

Tissue Min. 0.32 0.34 0.39 0.50 0.47 0.42 0.42 0.41 0.45 0.42 0.42

(g) Max. 1.09 1.18 1.28 1.39 1.30 1.27 1.63 1.41 1.71 1.25 1.33

SD 0.14 0.14 0.14 0.16 0.15 0.13 0.16 0.17 0.15 0.15 0.14

±2SE 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02

Percent Mean 15.2 15.2 14.8 15.8 15.7 14.7 16.2 16.3 15.6 16.0 15.1

Solids Min. 15.0 14.4 14.5 14.6 14.7 14.0 16.0 15.5 15.0 15.7 14.9

Max. 15.5 17.4 15.1 16.9 16.5 15.6 16.4 17.2 16.5 16.1 15.5

±2SE 0.24 1.48 0.26 0.98 0.84 0.75 0.17 0.88 0.65 0.20 0.27

Percent Mean 1.30 1.36 1.35 1.56 1.39 1.40 1.50 1.48 1.43 1.72 1.37

Lipids Min. 1.08 1.11 1.06 1.41 1.00 1.24 1.34 1.33 1.21 1.54 1.15

Max. 1.46 1.65 1.91 1.70 1.82 1.72 1.84 1.66 1.69 1.93 1.54

±2SE 0.18 0.23 0.38 0.12 0.42 0.22 0.24 0.14 0.20 0.16 0.18

N 300 277 280 273 270 261 284 275 284 280 277

WAWW − Whole-animal wet weight.
Table 10. Results of statistical analyses on clam growth metrics. 

Tannery Bay stations compared with the average of reference stations

Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

WAWW * * NS * * NS NS NS

WAWW Growth rate * * NS * * * * *

EOT Tissue weight * * NS * * * * *

% Solids NS NS NS * * NS * NS

% Lipids NS NS NS NS NS NS * NS

WAWW − Whole-animal wet weight.

EOT − End-of-test.

* Clams from Tannery Bay station significantly greater than the average of reference stations.

NS − No significant difference between Tannery Bay station and the average of reference stations.

Results of Student Newman-Keuls analyses on Tannery Bay stations

Log-transformed endof-test WAWW Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .867246 .377873 .861547 .789735 .284385 .861222 .526827

Sta 4 .365780 .810651 .625932 .293884 .937562 .597062

Sta 5 .164255 .179095 .987677 .368545 .755777

Sta 6 .896708 .137959 .873297 .424607

Sta 7 .145318 .840497 .412874

Sta 8 .244659 .485442

Sta 9 .365668

Rank- it transformed

Growth Rate Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .00072* .00002* .00004* .139430 .00892* .00012* .00266*

Sta 4 .00001* .00003* .00002* .437565 .00002* .597145

Sta 5 .00003* .00002* .00001* .00003* .00002*

Sta 6 .00683* .00002* .708783 .00002*

Sta 7 .00014* .00782* .00002*

Sta 8 .00001* .485304

Sta 9 .00002*

Tissue Weight Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .00072* .00003* .075583 .01181* .04229* .00485* .00003*

Sta 4 .00002* .151994 .581178 .352838 .554438 .00523*

Sta 5 .00003* .00002* .00002* .00001* .03653*

Sta 6 .403761 .527323 .330604 .00002*

Sta 7 .513972 .687648 .00090*

Sta 8 .542322 .00010*

Sta 9 .00207*
Table 10 (continued)

Percent Lipids Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .902962 .866733 .745944 .893682 .848253 .313136 .903733

Sta 4 .950793 .953924 .937862 .974102 .405374 .901736

Sta 5 .917972 .864730 .877328 .372000 .980931

Sta 6 .901736 .879546 .378010 .959420

Sta 7 .722749 .462647 .953924

Sta 8 .373886 .985781

Sta 9 .393714

Percent Solids Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Sta 3 .834347 .225505 .646079 .654861 .962322 .601823 .526351

Sta 4 .232043 .686619 .648643 .958376 .742218 .485736

Sta 5 .067887 .04795* .159345 .112709 .435463

Sta 6 .793791 .771365 .714562 .242913

Sta 7 .710338 .802691 .189968

Sta 8 .856783 .277800

Sta 9 .342190

WAWW − Whole-animal wet weight.

Values in bold face and marked with an asterisk indicate a significant difference between stations.

Table 11. Summary of water temperature conditions

during the study, by station, summer 1997.

Min. temp.

(

oC)

Max. temp.

(

oC)

Mean temp.

(

oC)

Sta 1 15.9 26.3 20.2

Sta 2 13.9 23.1 18.2

Sta 3 12.4 24.0 18.2

Sta 4 12.1 24.5 17.8

Sta 5 10.5 24.1 15.1

Sta 6 11.8 24.2 18.3

Sta 7 13.4 23.7 18.7

Sta 8 14.1 23.5 18.7

Sta 9 13.2 23.2 18.5

Sta 10 13.9 24.1 18.5
Table 12. Results of statistical analyses on mean daily temperature data.

Comparison stations Mean difference Standard deviation t-statistic df p-value

Station 1 - Station 2 1.93 0.46 4.21 10 0.0018*

Station 1 - Station 3 1.95 0.27 7.23 10 0.0000*

Station 1 - Station 4 2.45 0.22 11.29 10 0.0000*

Station 1 - Station 5 5.08 0.29 17.32 10 0.0000*

Station 1 - Station 6 1.82 0.27 6.85 10 0.0000*

Station 1 - Station 7 1.35 0.33 4.06 10 0.0023*

Station 1 - Station 8 1.61 0.35 4.58 10 0.0010*

Station 1 - Station 9 1.60 0.38 4.23 10 0.0018*

Station 1 - Station 10 1.67 0.35 4.81 10 0.0007*

Station 2 - Station 3 0.01 0.21 0.03 10 0.9765

Station 2 - Station 4 0.49 0.28 1.72 10 0.1164

Station 2 - Station 5 3.27 0.32 10.26 10 0.0000*

Station 2 - Station 6 0.08 0.27 0.30 10 0.7705

Station 2 - Station 7 0.51 0.18 2.91 10 0.1555

Station 2 - Station 8 0.40 0.11 3.51 10 0.0056*

Station 2 - Station 9 0.41 0.21 2.00 10 0.0732

Station 2 - Station 10 0.29 0.07 3.91 10 0.0029*

Station 3 - Station 4 0.31 0.10 3.29 10 0.0081*

Station 3 - Station 5 3.28 0.25 13.07 10 0.0000*

Station 3 - Station 6 0.05 0.18 0.28 10 0.7865

Station 3 - Station 7 0.47 0.07 6.26 10 0.0001*

Station 3 - Station 8 0.47 0.16 2.87 10 0.0166

Station 3 - Station 9 -0.37 0.09 -4.13 10 0.0021*

Station 3 - Station 10 0.28 0.16 1.77 10 0.1076

Station 4 - Station 5 2.72 0.22 12.38 10 0.0000*

Station 4 - Station 6 0.47 0.08 6.01 10 0.0001*

Station 4 - Station 7 1.16 0.19 6.20 10 0.0001*

Station 4 - Station 8 0.93 0.27 3.41 10 0.0067*

Station 4 - Station 9 0.68 0.16 4.32 10 0.0015*

Station 4 - Station 10 0.78 0.25 3.16 10 0.0102

Station 5 - Station 6 3.03 0.15 19.58 10 0.0000*

Station 5 - Station 7 3.46 0.22 15.48 10 0.0000*

Station 5 - Station 8 3.65 0.35 10.40 10 0.0000*

Station 5 - Station 9 3.44 0.39 8.88 10 0.0000*

Station 5 - Station 10 3.40 0.43 7.91 10 0.0000*

Station 6 - Station 7 0.53 0.17 3.19 10 0.0097*

Station 6 - Station 8 0.49 0.27 1.81 10 0.0999

Station 6 - Station 9 -0.24 0.18 -1.32 10 0.2161

Station 6 - Station 10 0.20 0.24 0.83 10 0.4281

Station 7 - Station 8 0.23 0.12 1.85 10 0.0948

Station 7 - Station 9 0.28 0.12 2.28 10 0.0460

Station 7 - Station 10 0.23 0.13 1.86 10 0.0924

Station 8 - Station 9 0.11 0.10 1.05 10 0.3172

Station 8 - Station 10 0.06 0.12 0.49 10 0.6319

Station 9 - Station 10 -0.02 0.09 -0.20 10 0.8481

NOTE: p-values in bold with asterisk represent significant difference between comparison stations.

df–degrees of freedom.
Table 13. Differences in weekly temperature ranges across stations.

Sta 1 Sta 2 Sta 3 Sta 4 Sta 5 Sta 6 Sta 7 Sta 8 Sta 9 Sta 10

Means of ranges 4.87 7.00 7.97 8.43 8.47 8.84 6.79 5.90 6.62 7.32

Comparison Test statistic # of means p-value

Station 1 - Station 2 5.676 5 <0.005*

Station 1 - Station 3 7.763 7 <0.001*

Station 1 - Station 4 8.551 9 <0.001*

Station 1 - Station 5 8.296 8 <0.001*

Station 1 - Station 6 9.182 10 <0.001*

Station 1 - Station 7 5.376 4 <0.005*

Station 1 - Station 8 3.329 2 <0.025*

Station 1 - Station 9 4.888 3 <0.005*

Station 1 - Station10 6.380 6 <0.001*

Station 2 - Station 6 3.505 6 >0.10

Station 2 - Station 8 2.348 4 >0.20

NOTE: p-values in bold with asterisk represent significant difference between comparison stations.
Table 14. Results of chemical analyses on sediment samples collected at the end of the study.

THg MeHg As Cd Cr Pb TOC Dry wt Gravel Sand Silt Clay Porosity Dry bulk

(μg/g) (μg/g) (μg/g) (μg/g) (μg/g) (μg/g) (%) (%) (%) (%) (%) (%) (%) density

(g/cm3)

Sta 1 0.0896 0.000737 6.49 0.98U 27.1 16.8 0.86 23.2 0.07 91.79 6.23 1.91 48.15 1.37

Sta 2 0.0311 0.0000385 2.00U 0.98U 13.4U 13.6U 0.23 79.7 0.81 95.35 2.66 1.18 44.07 1.5

Sta 3 2.07 0.00226 12.3 5.33 20598 218 11.72 16.2 0 48.61 32.97 18.42 81.3 0.35

Sta 4 1.27 0.00648 24 13.1 17789 142 12.38 26 0 28.59 47.97 23.44 81.86 0.35

Sta 5 1.04 0.00461 14.4 14.1 10108 114 10.53 25.1 0 21.62 50.39 27.99 85.07 0.31

Sta 6 0.433 0.0032 23.8 2.75 7800 60.7 5.09 51.2 0 50.56 40.39 9.05 68.06 0.79

Sta 7 0.264 0.0016 8.36 3.67 4479 53 1.66 63.3 0 54.4 40.3 5.3 54.82 1.15

Sta 8 0.19 0.000998 10.5 2.15 3980 55.7 5.52 71 0.04 80.25 16.16 3.55 50.57 1.22

Sta 9 0.0969 0.000707 5.19 0.98U 984 15.7 0.7 69.8 0 89.06 8.22 2.71 50.87 1.28

Sta 10 0.126 0.000409 2.00U 0.98U 1291 21.5 0.67 72.7 0.54 93 4.79 1.67 49.04 1.37

Table 15. Results of chemical analyses on surface water samples collected at the beginning and end of the study.

THg

(UF)

THg

(Dis)

MeHg

(UF)

MeHg

(Dis)

As

(UF)

As

(Dis)

Cd

(UF)

Cd

(Dis)

Cr

(UF)

Cr

(Dis)

Pb

(UF)

Pb

(Dis)

TSS TOC DOC HardnessNH4 NO2 Chl-a Phaeo pH

(ng/L) (ng/L) (ng/L) (ng/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg N/L) (μg/L) (μg/L)

Deployment

Sta 1 2.07 1.87 0.224 0.201 0.26 0.18 0.1U 0.1U 1.70U 1.70U 0.61U 0.61U 2 10.2 11.42 46.8 0.018 NA 2.03 1.58 7.0

Sta 4 5.7 0.728 0.0939 0.0214(J) 0.18 0.11 0.1U 0.1U 45.4 3.06 0.61U 0.61U 2.63 2.13 2.12 79.7 0.015 NA 2.19 1.25 7.0

Sta 5 0.771 0.488 0.0843 0.0376 0.2 0.15 0.1U 0.1U 32.7 2.28 0.61U 0.61U 2.19 2.09 1.95 78.5 0.024 NA 1.86 0.78 7.0

Sta 9 1.35 0.315 0.0317 0.0294(J) 0.21 0.2 0.1U 0.1U 6.95 0.79J 0.61U 0.61U 2.49 1.39 1.88 51.3 0.011 NA 1.62 0.55 7.0

Sta 10 2.63 0.431 0.0173(J) 0.0279(J) 0.27 0.2 0.1U 0.1U 5.82 0.42J 0.61U 0.61U 4.38 1.86 1.73 48.7 0.008 NA 3.22 1.13 7.0

Retrieval

Sta 1 1.19 1.57 0.112 0.0788 < 0.05 < 0.05 < 0.05 < 0.05 < 0.20 < 0.20 < 0.41 < 0.41 0.641 3.94 3.2 40 0.005 0.0013 2.75 1.55 6.81

Sta 4 2.14 0.94 0.0478 0.0321 0.06 0.06 < 0.05 0.06 7.23 1.23 < 0.41 < 0.41 0.226 2.37 1.9 61.3 0.022 0.0034 1.99 0.76 5.99

Sta 5 1.9 0.755 0.0628 < 0.0306(U) 0.08 0.1 < 0.05 < 0.05 6.27 1.01 < 0.41 < 0.41 0.604 2.3 1.92 64.7 0.041 0.0042 1.83 0.97 6.07

Sta 9 1.93 1.12 0.0619 < 0.0310(U) 0.16 0.11 < 0.05 0.05 8.12 1.05 < 0.41 < 0.41 0.415 2.24 1.89 61.1 0.048 0.0037 1.95 0.93 6.29

Sta 10 1.32 1.08 0.0304 < 0.0307(U) 0.06 0.05 < 0.05 < 0.05 3.15 0.7 < 0.41 < 0.41 0.181 2.31 1.89 43 0.038 0.0038 2.8 1.34 6.52

J = uncertain value; U = below detection limit; UF = unfiltered; Dis = dissolved; NA = Not available

All metals in terms of total concentration

Table 16. Calculated quotients for EOT sediment concentration/LEL, and

sum of quotients by station.

THg MeHg As Cd Cr Pb Sum of

Quotients

TOC %

fines

Sta 1 0.45 na 1.08 0.82 1.04 0.54 3.93 0.86 8.14

Sta 2 0.16 na 0.17 0.82 0.26 0.22 1.62 0.23 3.84

Sta 3 10.35 na 2.05 8.88 792.23 7.03 820.55 11.72 51.39

Sta 4 6.35 na 4.00 21.83 684.19 4.58 720.96 12.38 71.41

Sta 5 5.20 na 2.40 23.50 388.77 3.68 423.55 10.53 78.38

Sta 6 2.17 na 3.97 4.58 300.00 1.96 312.67 5.09 49.44

Sta 7 1.32 na 1.39 6.12 172.27 1.71 182.81 1.66 45.6

Sta 8 0.95 na 1.75 3.58 153.08 1.80 161.16 5.52 19.71

Sta 9 0.48 na 0.87 0.82 37.85 0.51 40.52 0.7 10.93

Sta 10 0.63 na 0.17 0.82 49.65 0.69 51.96 0.67 6.46

LEL

values

(μg/g)

0.2 na 6.0 0.6 26.0 31.0

na − not available

Table 17. Correlation coefficients (r) for trace elements

in surface water, sediment, and clam tissues.

Cr THg MeHg As Cd Pb

water : sediment 0.53 0.48 0.03 -0.83 na na

water : tissue 0.62 -0.46 0.52 0.300 na na

sediment : tissue 0.27 0.0001 0.68 -0.042 -0.3 0.12

na = not able to calculate coefficients because there was no linear spread in the data

Table 18. Correlation coefficients for tissue chemistry vs. clam growth

metrics based on concentration and content.

Clam Tissue Concentration

Cr THg MeHg As Cd Pb

Survival -0.251 -0.355 -0.484 -0.354 0.019 -0.253

EOT WAWW -0.210 -0.055 0.097 -0.274 -0.284 -0.169

Growth Rate -0.223 -0.340 -0.256 -0.477 -0.102 -0.283

Tissue Weight

(wet)

0.267 -0.082 -0.238 0.115 0.089 0.109

Tissue Weight (dry) 0.342 -0.162 -0.324 0.247 0.260 0.175

Clam Tissue Content

Cr THg MeHg As Cd Pb

Survival -0.172 -0.162 -0.309 0.064 0.223 -0.133

EOT WAWW -0.175 0.190 0.351 0.238 -0.034 -0.075

Growth Rate -0.133 0.068 0.162 0.380 0.307 -0.116

Tissue Weight

(wet)

0.283 -0.031 -0.176 0.256 0.160 0.137

Tissue Weight (dry) 0.355 -0.114 -0.268 0.385 0.322 0.198

EOT WAWW − end-of-test whole-animal wet weight.
Table 19. Correlation coefficients for

temperature vs. clam growth metrics.

Survival 0.363

Growth Rate 0.122

Tissue Weight (wet) -0.196

Tissue Weight (dry) -0.292
8.0 FIGURES
N

0 10 20

 meters

9

7

6

5

4

3

2

Tannery

Point

B a y

Clam deployment station ID

Previous sediment sampling station ID

Cannelton Industries site boundary

Barren zone

Wetlands

Water level stations

South Street

SOO RAILROAD

4th Avenue West

Oak Street

4th Avenue West

16th

Street

18th

St. W

12th St. W

scale is approximate

SD-REF-02

REF-2

SD-HQ-REF-01

SD-REF-03

SD-03

SD-15

SD-15

SD-13

SD-11

SD-12

SD-02

SD-14

SD-05

SD-06A

SD-07

SD-16

SD-09

SD-10

SD-08

1

Saint Mar y's

Riv e r

Seymour

Creek

SD-HQ-REF-02

Hairball Beach

Waiska

Bay

Bay Mills

Point

Back

Bay

Saint Mary's River Canada

United States

Izaak

Walton Bay

75

Sault Ste

Marie Cannelton

Industries

REF-1

1

MI

WI

IA

IL IN

KY VA

WV

Ohio

PA

NY

CANADA

Lake Superior Lake Huron

Lake Michigan

Lake Erie

Lake Ontario

Holding Site
Clam rep #1

Clam rep #3

Clam rep #4

Clam rep #2

2 m

2 m

2 m

2 m

Figure 2. Deployment layout at each station.
















and at atnce stations.

Date

07/17/97 07/31/97 08/14/97 08/28/97

Stn 1

Stn 2

Stn 3

Stn 4

Stn 5

Stn 6

Stn 7

Stn 8

Stn 9

Stn 10