USGS



BIOLOGICAL AND ECOTOXICOLOGICAL CHARACTERISTICS OF TERRESTRIAL VERTEBRATE SPECIES RESIDING IN ESTUARIES

Snapping Turtle
Snapping Turtle photo by Harry B. Barrett
(Photo by Harry B. Barrett)


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Biological Characteristics

Species

Chelydra serpentina is 20-47 cm in length, with a massive head and powerful jaws. Males are often larger than females (McVey et al., 1993). In both sexes, the heavily-serrated carapace is tan to dark brown. (Behler and King, 1979).

Status in Estuaries

This species can be found in freshwater and brackish areas, and prefers soft mud bottoms and abundant vegetation. A typical clutch is composed of 25-50 eggs, laid in a deep flask-like cavity that can be several hundred meters from the water (Behler and King, 1979; McVey et al., 1993). Females may lay 1 or 2 clutches per season. In winter months, snapping turtles hibernate by burrowing in mud or debris, sometimes in large congregations, for periods of 5-7 months (McVey et al., 1993). The maximum age of a snapping turtle recorded in nature is 24 years (McVey et al., 1993).

Abundance and Range

Snapping turtles occur in the U.S. east of the Rockies, ranging from Canada to the Gulf of Mexico (Behler and King, 1979).

Site Fidelity

Most turtles stay in one general area from year to year. One study found 91.9% of turtles returning to the same nesting site one year later (McVey et al., 1993).

Ease of Census

Difficult

Feeding Habits

Generalists. Snapping turtles eat invertebrates, carrion, aquatic plants, fish, birds, and small mammals (Behler and King, 1979).

Snapping Turtle Contaminant Exposure Data

I.

Organochlorine Contaminants

A.

Concentrations in Adults

1.

There were no detectable concentrations of DDE, dieldrin, or heptachlor epoxide present in a female snapping turtle, or its eggs, collected in Iowa in 1974 (Punzo et al., 1979).

2.

Organochlorine content was measured in fat, liver, skeletal muscle and eggs of snapping turtles captured in 1976-78 from the Hudson River and other middle and northern New York localities (Stone et al., 1980). In fat tissue, PCBs averaged 2990 g/g lipid weight in Hudson R. and 464 g/g at other sites. DDE and dieldrin were detected in the fat tissue of approximately 70% of specimens at values <81.30 (Hudson R.) and <34.10 g/g (other sites). Mean PCB levels were significantly higher in 23 turtles from Hudson R. at 66.05 and 4.24 g/g wet weight in liver and skeletal muscle, respectively, than in 8 turtles from other waters at 7.77 and 0.44 g/g. DDE was detected in 16 of 18 livers tested from Hudson R. and 5 of 7 from elsewhere, with one value of 17.40 g/g, and all others <2.11 g/g. In skeletal muscle, DDE was detected in 17 of a total of 24 turtles analyzed, with concentrations <0.74 g/g. Dieldrin was found in 11 of a total of 17 turtles analyzed, with all values <0.99 g/g.

3.

Fat from snapping turtles collected from the Hudson River was analyzed for PCDF (Rappe et al., 1981). PCB in the fat was found at a concentration of 750 g/g. A total of 18 different PCDF isomers were detected at the following levels: 45 pg/g TCDFs, 820 pg/g PnCDFs, 700 pg/g HxCDFs, 1000 pg/g HpCDFs, and 350 pg/g OCDF. Total PCDF concentration was 3 ng/g.

4.

Two snapping turtles, one from Irondequoit Bay, Lake Ontario (LO), and another from the upper Hudson River (HR), were collected and analyzed to determine their suitability as a biological screen for PCBs (Olafsson et al., 1983). Total PCB levels were 663 g/g wet weight in the LO turtle and 3608 g/g in the HR sample. Fifty-one congeners were measured in the LO turtle and 46 in the HR turtle. Other pesticides analyzed were DDE, 87 g/g LO and 14 g/g HR, and mirex, 28 LO and 1.9 HR. Due to their high tolerance to toxic substances, snapping turtles were concluded to be an excellent sentinel species.

5.

Two snapping turtles were collected from separate ponds at a hazardous waste site in Moreau, Saratoga County, New York in the early 1980's (Watson et al., 1985).  Total PCBs in fat ranged from 81-4,530 g/g wet weight.  Total PCB concentration in liver and muscle of the latter specimen was 185 and 17 g/g, respectively.  The former specimen had 0.053 ng/g 2,3,7,8-TCDF in its fat. One snapping turtle had 0.830 ng/g combined penta- and hexachloronapthalene in its liver.

6.

Seventeen snapping turtles were collected from six locations in Minnesota in 1981 for contaminant analysis (Helwig and Hora, 1983). Concentrations of PCB ranged from <0.2-60.5 g/g in fat and were <0.1 g/g in muscle for all locations. Highest PCB concentrations were detected at the Mississippi River locations.

7.

Snapping turtles were collected during the summers of 1981 and 1982 from brackish and fresh waters of the Hackensack Meadowlands in New Jersey, and relatively uncontaminated freshwater in Maryland, were analyzed for metal and organochlorine contaminants (Albers et al, 1986). Sample sizes per sex ranged between 3-8. PCBs were detected in the visceral fat of all samples, with a significantly higher mean of 291.13 g/g of lipid in males from brackish waters in New Jersey, and means of 23.55-41.20 g/g in other locations. Combined levels of PCB from all locations were significantly higher in males compared to females. Oxychlordane was detected in 88% of samples, with locality means ranging between 1.30-9.33 g/g. cis-Nonachlor and trans-nonachlor, detected in 59% and 53% of the turtles, respectively, had similar means ranging from 0.31-4.01 g/g. DDE was detected in 63% of turtles, with a mean concentration of 2.03 g/g in from freshwater sites in New Jersey, which was significantly higher than that for males from brackish waters in New Jersey, 0.16 g/g. Males from Maryland also had a significantly higher mean (0.39 g/g) than females from the same location (0.10 g/g). All other organochlorines were detected in 25% or less of samples. Cis-chlordane was found only in females from brackish waters in New Jersey (0.12 g/g) and DDD only in males from freshwater in New Jersey (0.13 g/g). trans-Chlordane was found in both sexes, but only from the Maryland location, with means <0.08 g/g. Dieldrin and heptachlor epoxide were found only in turtles from freshwater locations at means <0.07 and <0.38 g/g, respectively. DDT, endrin, and toxaphene were not detected in any samples.

8.

Abdominal fat and liver tissues were taken from three snapping turtles collected from the upper St. Lawrence River in 1984-85 for PCDD and PCDF analysis (Ryan et al., 1986). Contaminants were identified in the following concentrations in fat and liver, respectively, (pg/g, wet weight): 6-300 and <74 2,3,7,8-TCDF, 232-470 and 32-107 2,3,7,8-TCDD, <600 and <100 1,2,3,7,8-PnCDF, 95-3020 and 13-480 2,3,4,7,8-PnCDF, 33-104 and 4.6-22 1,2,3,7,8-PnCDD, <890 and <480 total HxCDFs, 16-102 and 3-18 total HxCDDs, <69 and <13 1,2,3,4,6,7,8-HpCDF, 2.3-17 and 3.7-4.5 1,2,3,4,6,7,8-HpCDD, and 17-36 and <27 1,2,3,4,6,7,8,9-OCDD.

9.

PCB congeners were compared between a snapping turtle from an environment with "low pollution" in Chenango County, New York, to one with "high pollution" in Saratoga County, New York (Bryan et al., 1987b). Total PCB (g/g) distribution in tissues of turtles from the low and high pollution areas was: 4.2 and 1600 fat, 1.6 and 100 testes, 1.0 and 82 brain, 1.0 and 72 liver, 0.64 and 49 heart, 1.2 and 48 kidney, 1.2 and 48 pancreas, and 0.41 and 13 lungs. A total of 31 congeners were measured and each was detected in both turtles. Congeners detected in the highest amounts were (low and high pollution, g/g): 0.151 and 272 2,4,3',4'-tetrachlorobiphenyl; 0.117 and 297 2,3,6,2',3',6'-hexachlorobiphenyl; 0.54 and 166 2,4,2',4',5'-pentachlorobiphenyl; 0.332 and 152 2,3,6,2',3',4',6'-heptachlorobiphenyl; and 0.159 and 171 3,4,2',3',4'-pentachlorpbiphenyl.

10.

A male snapping turtle was collected from the Upper Hudson River near Moreau, New York (Olafsson et al., 1987). PCB congener concentrations were measured in the adipose tissue, heart, spleen, pancreas, liver, neck muscle, and testes. Concentrations in adipose tissue were 0.808 g/g for 2,3'4,4',5-pentachlorobiphenyl, 1.87 g/g for 2,3',4,4',5,5'-hexachlorobiphenyl, 2.11 g/g for 2,3,3',4,4',5,5'-heptachlorobiphenyl, 8.53 g/g for 2,3,3',4,4',5-hexachlorobiphenyl, and 33.5 g/g for 2,3,3',4,4'-pentachlorobiphenyl. In other tissues, concentrations ranged from 0.0228-0.287 g/g for 2,3,3',4,4',5-hexachlorobiphenyl, 0.195-1.68 g/g for 2,3,3',4,4'-pentachlorobiphenyl and were <0.1 g/g for 2,3',4,4',5-pentachlorobiphenyl, 2,3',4,4',5,5'-hexachlorobiphenyl, and 2,3,3',4,4',5,5'-heptachlorobiphenyl.

11.

Four snapping turtles collected from the Tinicum National Environmental Center in Pennsylvania contained total PCB concentrations ranging from 11.6-27.3 g/g in fat (Schwartz et al., 1987).

12.

Organochlorines were measured in 78 adult snapping turtles collected in 1988-89 from 16 sites in southern Ontario (Hebert et al., 1993). The range of mean contaminant levels in muscle for all sites were as follows (ng/g wet weight): 0.00-655.28 total PCB, 0.00-164.60 total DDT, 0.00-3.95 mirex, and 0.00-1.26 OCS. Significant intersite differences were found for all four substances. A highly significant relationship was found between contaminants in adult female turtles and their eggs.

13.

Gravid snapping turtles were collected in New York state (n=6) from 5 different sites (Pagano et al., 1999).  All amounts are in g/g. 

Annandale, NY, Hudson (sample 1) contained 22.4 PCB, 0.13 DDE, 0.06 mirex, and 0.05 HCB in liver; 19.3 PCB, 0.29 DDE, 0.04 mirex, and 0.01 HCB in adipose.

Annandale, NY, Hudson sample 2 contained: liver tissue 68.5 PCB, 0.07 DDE, 0.13 mirex, and 0.02 HCB; adipose tissue 45.8 PCB, 0.06 DDE, 0.05 mirex, and 0.01 HCB.

Massena, NY Massena sample contained: liver tissue 695.9 PCB, DDE ND, 8.41 mirex, 0.08 HCB; adipose tissue 894.8 PCB, DDE ND, 9.98 mirex, 0.05 HCB. 

Rochester, NY, Sodus Bay sample: liver tissue 2.2 PCB, 0.66 DDE, 0.04 mirex, and 0.02 HCB; adipose tissue 2.0 PCB, 0.71 DDE, 0.02 mirex, 0.01 HCB.

Oswego, NY, Rice Creek sample: liver tissue 3.8 PCB, 0.93 DDE, 0.17 mirex, and 0.01 HCB; adipose tissue 4.7 PCB, 1.10 DDE, 0.15 mirex, and 0.01 HCB.

Oswego, NY, Industrial sample: liver tissue 140.8 PCB, DDE ND, 0.42 mirex, and 0.01 HCB; adipose tissue 215.3 PCB, DDE ND, 0.74 mirex, 0.01 HCB.

14.

Blood was collected from adult snapping turtles in June 2001 and 2002 from 2 sites in Areas of Concern in the Lake Erie basin and 1 reference sites outside of the basin for contaminant analysis (de Solla and Fernie 2004).  Contaminants were analyzed per clutch and detected at the following levels (ng/g wet weight): 15.2-96.3 total PCBs, 0.58-4.63 DDE, 0.18-6.65 mirex, 0.13-0.72 HCB, nd-1.12 trans-nonachlor and nd-0.45 cis-nonachlor.

B.

Concentrations in Eggs

1.

Organochlorine content was measured in 6 snapping turtle eggs collected from the Hudson River in 1976-77, and in the liver and skeletal muscle of adult turtles also captured from the area (Stone et al., 1980). PCB was present in all of the eggs at a mean of 28.9 g/g wet weight. DDE was detected in all 4 eggs tested at values <0.56 g/g and dieldrin in all 6 eggs analyzed at levels <0.055 g/g.

2.

A study on the disposition of toxic PCB congeners in snapping turtle eggs concluded that 2,3,3',4,4'-pentachlorobiphenyl and 2,3,3',4,4',5-hexachlorobiphenyl made up more than 99% of the total toxicity in the egg, and that over 95% of the total toxicity resided in the yolk (Bryan et al., 1987a).

3.

Snapping turtle eggs were collected in 1981 and 1984 from a total of 49 clutches from 9 locations within the Great Lakes-St. Lawrence River basin and one reference site (Algonquin Provincial Park in Ontario) for contaminant analysis (Struger et al., 1993). Contaminants were analyzed per clutch and detected at the following levels (g/g wet weight, % clutches detected): 0.0057-4.758 total PCBs (100%), <0.430 DDE (98%), 0.220 mirex (84%), <0.130 HCB (46%), <0.100 dieldrin (86%), <0.110 oxychlordane (88%), <0.060 cis-chlordane (72%), <0.030 trans-nonachlor (68%), <0.010 heptachlor epoxide (72%), and <0.040 -HCH (34%). Pentachlorobenzene, 1234-TeCB, and 1235/1245-TeCB were not detected in any sample. Both high variation among clutches from the same locality and high variation for all organochlorines between sites were exhibited. Eggs from Hamilton Harbour, Port Franks, Bay of Quinte/Murray Canal, and Lake St. Clair tended to be the most contaminated. Eggs from Hamilton Harbour analyzed for PCDDs and PCDF contained the following concentrations: 67 pg/g 2,3,7,8-TCDD, 6 pg/g 1,2,3,7,8-PnCDD, 4 pg/g 1,2,3,6,7,8-HxCDD, 1 pg/g 1,2,3,7,8,9-HxCDD, 2 pg/g 1,2,3,4,6,7,8-HpCDD, and 14 pg/g 2,3,4,7,8-PnCDF. OCDD, 2,3,7,8-TCDF, 1,2,3,4,7,8/1,2,3,4,6,7-HxCDF, and 1,2,3,6,7,8-HxCDF were not detected.

4.

In 1981, 1984, 1988, 1989, and either 1990 or 1991, snapping turtle eggs were collected from nests in five locations in the Great Lakes basin and from Algonquin Provincial Park (APP) in northcentral Ontario (Bishop et al., 1996). The following organochlorines were detected (range of yearly means in g/g wet weight): 0.32-3.38 APP, 5.27-54.36 other sites, total PCBs; 0.04-0.49 APP, 0.66-10.65 other sites, DDE; 0.003-0.02 APP, 0.03-0.35 other sites HCB; 0.01-0.07 APP, 0.05-0.94 other sites dieldrin; 0.003-0.07 APP, and 0.03-2.12 other sites mirex. Significant differences between sites occurred for each chemical in various years, though Cootes Paradise/Hamilton Harbour and Lynde Creek eggs tended to be the most contaminated. Contaminants were determined for 6 PCB congeners, 8 PCDDs, and 14 PCDFs. Lynde Creek contained the highest occurrence of these contaminants with detection all PCB and PCDD compounds and 11/14 PCDFs. APP was the least contaminated site containing all PCB congeners, 1 PCDD, and no PCDFs.

5.

Organochlorine accumulation and intra-clutch variation was studied in snapping turtles collected from 7 nests in 1986 and 1987 from Cootes Paradise in western Lake Ontario (Bishop et al., 1995). In comparing the first five eggs laid, the last five eggs, and a "composite" sample of eggs laid after the first five and before the last five, the first five tended to have the highest mean concentrations of chlorinated hydrocarbons on a wet weight basis and on a lipid weight basis. The last five eggs tended to have the lowest values, and composite eggs were generally intermediate. Concentrations for the first five, the composite, and last five, respectively were as follows (ng/g wet weight): 43.9, 16.6, 20.9 HCB; 109.2, 92.0, 38.9 cis-chlordane; 298.3, 138.3, 92.1 trans-nonachlor; 487.0, 70.4, 153.7 DDE; and 2099.2, 1716.9, 1653.9 sum PCBs. Contaminants were quantified in eggs detected at oviposition, at "stage" 20, 22, and 24 of development, on the day of hatch, and 18 days posthatch. The percent contaminant transferred from egg at oviposition into embryo tissues increased for all chemicals until day of hatch, then decreased at 18 days posthatch. Percentages decreased from day of hatch to 18 days posthatch by the following amounts: 55.2% to 51.9% HCB; 74.1% to 45.7% cis-chlordane; 90.5% to 52.2% trans-nonachlor; 71.9% to 45.3% DDE; and 88.3% to 62.2% sum PCBs.

6.

Snapping turtle eggs collected immediately after oviposition from Algonquin Provincial Park (APP) and 4 locations in the Great Lakes between 1986 and 1989 were analyzed for hatching success, incidence of deformities, and contaminant concentrations (Bishop et al., 1991). A total of 129 clutches were sampled for organochlorine analysis. For 1986-87, APP contaminant levels were significantly lower than all other sites with means of 1.3 ng/g wet weight HCB, 76 ng/g total PCBs, and no detection of cis-chlordane or trans-nonachlor. Cootes Paradise and Lynde Creek were significantly higher than all other sites with means up to 17 ng/g HCB, 112 ng/g cis-chlordane, 136 ng/g trans-nonachlor, and 2708 ng/g total PCBs. In 1988-89, Cootes Paradise was significantly higher than all locations for all contaminants and APP had the lowest values of all but heptachlor epoxide. Mean values were as follows (ng/g): 0.7-25 HCB, 2.4-112 cis-chlordane, 1.6-249 trans-nonachlor, 8.0-877 DDE, 0.5-143 mirex, 0.6-20 dieldrin, 0.2-5.6 heptachlor epoxide, and 25-3322 total PCBs. Of 10 PCDD congeners and 9 PCDFs analyzed, none were detected in APP, and 17 were detected in Lynde Creek, the most of any site.

7.

Snapping turtle eggs collected immediately after oviposition from 15 nests in Hamilton Harbour, Lake Ontario had the following mean organochlorine levels (g/g lipid weight): 5.9 DDE, 1.4 mirex, 0.49 dieldrin, 0.02 PCB #52, 1.7 PCB #105, 7.3 PCB #118, 9.3 PCB #138, 9.3 PCB #153, 6.4 PCB #180, 0.61 PCB #194, and 54.3 total PCB (Bishop et al., 1994). No significant correlation was found for body size and any of the contaminants measured in the eggs.

8.

Snapping turtle eggs were collected from 39 clutches in 10 locations on the St. Lawrence River and its tributaries in Canada in 1989 and 1990 (Bonin et al., 1995). Five eggs from each clutch were pooled and analyzed for organochlorines and mercury, and pools from similar localities were averaged. The following contaminants were detected in all samples (ranges of locality means in ng/g wet weight): 106-5094 PCB; 0.4-17.2 HCB; 7.0-372.7 DDE; 0.4-133.5 mirex; 2.8-101.5 oxychlordane; 2.4-128.6 trans-nonachlor; 1.1-85.7 cis-nonachlor; 0.4-10 heptachlor epoxide; and 2.5-44.6 dieldrin. Cis-chlordane was found in 92% of samples with means of 0.1-62.4 ng/g and p-mirex in 82 % with means of 0.1-49.5 ng/g. DDD, detected in 67% had means ranging from 0.2-16.4 ng/g. Trans-chlordane, -HCH, OCS, and DDT, detected in 85, 62, 56, and 41% of samples respectively, had mean levels 5.6 ng/g. 1245-TeCB, 1234-TeCB, and pentachlorobenzene, and gamma-s.gif (58 bytes)-HCH were not detected in any samples, and alpha-s.gif (59 bytes)-HCH was detected in 3 clutches only. PCB congeners 118, 138, and 153 accounted for over half of the PCBs detected. Overall, less contaminated samples tended to be from the Ottawa River, while eggs from the St. Lawrence were highly variable.

9.

From 1989-1991, snapping turtle eggs were collected from seven study locations in the Great Lakes basin and St. Lawrence River, and Algonquin Provincial Park (reference site) in north-central Ontario (Bishop et al., 1998). Mean total PCB concentrations were 0.241-3.95 g/g wet weight at the study sites and 0.018 g/g at the reference site. Non-ortho PCB congeners measured were 37 (2.8-27.2 pg/g at study sites, 3.8 pg/g at the reference site), 81 (32.4-960.8 pg/g study, 12.0 pg/g reference), 77 (14.0-256.6 pg/g study, 6.2 pg/g reference), 126 (201.1-2972.2 pg/g study, 51.7 pg/g reference), 169 (11.6-70.1 pg/g study, 2.9 pg/g reference), and 189 (4.2-58.9 pg/g study, 1.1 pg/g reference). When measuring PCDDs and PCDFs, only one congener was detected at the reference site (0.9 pg/g 1,2,3,4,6,7,8,9-OCDD). Other congeners were infrequently detected, with detection of each congener ranging from all to none of the seven of the study sites. Maximum mean concentrations (pg/g) were 27.4 2,3,7,8-TCDD, 36.4 1,2,3,7,8-PnCDD, 2.6 1,2,3,4,7,8-HxCDD, 27.0 1,2,3,6,7,8-HxCDD, 2.8 1,2,3,7,8,9-HxCDD, 4.9 1,2,3,4,6,7,9-HpCDD, 10 1,2,3,4,6,7,8-HpCDD, 21 1,2,3,4,6,7,8,9-OCDD, 30.6 1,2,4,7,8-PnCDF, 24.1 2,3,4,7,8-PnCDF, 7.9 2,3,4,6,7-PnCDF, 2.7 1,2,3,6,7,8-HxCDF, 6.2 1,2,4,6,8,9-HxCDF, 1.2 1,2,3,4,7,8-HxCDF, 3.2 1,2,3,6,7,8-HxCDF, 1.8 1,2,3,7,8,9-HpCDF, 0.3 2,3,4,6,7,8-HpCDF, 1.4 1,2,3,4,6,7,8-HpCDF, 0.2 1,2,3,4,6,8,9-HpCDF, 0.8 1,2,3,4,7,8,9-HpCDF, and 1.6 1,2,3,4,6,7,8,9-OCDF. Pesticides detected in at least one study site at concentrations <1 g/g were DDE, DDD, DDT, 1,2,4,5-chlorobenzene, 1,2,3,4-chlorobenzene, pentachlorobenzene, photomirex, mirex, alpha-s.gif (59 bytes)-HCH, -HCH, OCS, dieldrin, trans-chlordane, cis-chlordane, oxychlordane, trans-nonachlor, cis-nonachlor, and heptachlor epoxide.

10.

In 1995, blood samples were collected from adult snapping turtles from four sites in Southern Ontario (de Solla et al., 1998). Mean total PCB in blood plasma from males ranged from 0.018 to 0.415 g/g wet weight among sites. Mean concentrations of all other organochlorine contaminants analyzed were <0.025 g/g. PCB congeners 37, 81, 77, 169, and 189 were detected at colony means ranging from ND to 4.77 pg/g in female turtles, and PCB-126 occurred at means up to 57.68 pg/g. Octachlorodibenzodioxin reached a maximum mean of 4.59 pg/g in females, while concentrations of other PCDD and PCDF congeners were generally <1 pg/g.

11.

Gravid snapping turtles were collected in New York state (n=6) from 5 different sites (Pagano et al., 1999).  All amounts of contaminants in eggs are in g/g. 

Annandale, NY, Hudson sample 1: 7.2 PCB, 0.014 DDE, 0.03 mirex, and 0.01 HCB.

Annandale, NY, Hudson sample 2: 22.3 PCB, 0.06 DDE, 0.02 mirex, and 0.01 HCB.

Massena, NY Massena sample: 310.1 PCB, DDE ND, 2.84 mirex, and 0.05 HCB. 

Rochester, NY, Sodus Bay sample: 1.1 PCB, 0.23 DDE, 0.02 mirex, 0.01 HCB.

Oswego, NY, Rice Creek sample: 1.5 PCB, 0.28 DDE, 0.04 mirex, and 0.01 HCB.

Oswego, NY, Industrial sample:  79.8 PCB, DDE ND, 0.19 mirex, and 0.01 HCB. 

12.

In June of 1998, 5 eggs were collected from each of 8 clutches in Akwesasne, Ontario, Canada (de Solla et al., 2001).  

Mean (and SD for Snye) concentrations in snapping turtle eggs at the Raquette (N=1), Turtle Creek (N=1), St. Regis (N=1), and Snye (N=5) sites were, respectively: 2, 117, 1, and 0.8 (1.10) ng/g wet weight hexachlorobenzene; 1, 7, ND, and ND ng/g octachlorostyrene; 3, 38, trace, and 1.00 (1.00) ng/g heptachlor epoxide; ND, 29, 3, and 5.20 (3.90) ng/g oxychlordane; trace, 27, trace, and ND ng/g cis-chlordane; 16, 176, 4, and 4.20 (4.09) ng/g trans-nonachlor; 29, 852, 11, and 9.80 (7.40) ng/g DDE; 5, 280, 4, and 3.20 (2.59) ng/g dieldrin; trace, 2, ND, and ND ng/g DDD; trace, trace, ND, and trace or ND ng/g DDT; 8, 85, 2, and 2.00 (2.12) ng/g cis-nonachlor; 27, 213, 3, and 6.20 (6.50) ng/g photomirex; 59, 438, 5, and 12.40 (13.214) ng/g mirex; 5960, 737,683, 6785, and 2378.2 (2116.29) ng/g total PCB; and 8918, 265,438, 2603, and 2721 (2935.35) ng/g arochlor 1254:1260 (1:1). Turtle Creek had the highest concentrations, especially that of PCBs

Pooled snapping turtle eggs had the following concentrations of organochlorines (in ng/kg): 1064.62 PCB-37, 4564.81 PCB-77, 37418.0 PCB-81, 15042.1 PCB-126, 90.58 PCB-169, 69.43 PCB-189, 6.66 2378-TCDD, 1.06 123678-HCDD, 1.93 12346789-OD, 2.64 2378-TCDF, 1.71 12378-PCDF, 60.48 23478-PCDF, 7.09 123478-PCDF, 3.34 123678-PCDF, and 0.89 1234678-PCDF. 12378-TCDD and 1234678-HCDD were not detected. 

TCDD equivalents of total PCBs (in ng/kg) for snapping turtle eggs calculated from Kennedy et al., 1996, Ahlborg et al., 1994, Van den Berg et al., 1998 were, respectively: 6.07, 0.32, and 0.29 for Raquette; 736.4, 13.2, and 12.97 for Turtle Creek; 6.72, 0.12, and 0.12 for St. Regis; and 2.56, 0.11, and 0.1 for Snye Marsh. Turtle Creek values were higher than the other sites. 

TCDD equivalents (ng/kg) for pooled snapping turtle eggs calculated from Van den Berg et al., 1998, were: 0.46 PCB-77, 3.47 PCB-81, 1504.21 PCB-126, 0.91 PCB-169, 1547.46 total non-ortho PCBs, 6.66 2378-TCDD, 0.11 123678-HCDD, 0.00019 12346789-OD, 0.26 2378-TCDF, 0.086 12378-PCDF, 30.24 23478-PCDF, 0.71 123478-PCDF, 0.33 123678-PCDF, 0.0089 1234678-PCDF, and 38.41 total PCDD/PCDF. 

TCDD equivalents (in ng/kg) for pooled snapping turtle eggs calculated from Kennedy et al., 1996, were: 0.43 PCB-37, 136.94 PCB-77, 6944.59 PCB-81, 4512.64 PCB-126, 1.81 PCB-169, 11595.4 total non-ortho PCBs, 6.66 2378-TCDD, 2.9 2378-TCDF, and 9.56 total PCDD/PCDF. 

TCDD equivalents (ng/kg) for pooled snapping turtle eggs calculated from Ahlborg et al., 1994, were: 2.28 PCB-77, 1504.21 PCB-126, 0.91 PCB-169, 0.069 PCB-189, and 1547.46 total non-ortho PCBs. 

TCDD equivalents (ng/kg) for pooled snapping turtle eggs calculated from Safe, 1994, were: 45.65 PCB-77, 1504.21 PCB-126, 4.53 PCB-169, 1554.39 total non-ortho PCBs, 6.66 2378-TCDD, 0.11 123678-HCDD, 0.0019 12346789-OD, 0.26 2378-TCDF, 0.086 12378-PCDF, 30.24 23478-PCDF, 0.71 123478-PCDF, 0.33 123678-PCDF, 0.0089 1234678-PCDF, and 38.41 total PCDD/PCDF. 

TCDD equivalents (ng/kg) for pooled snapping turtle eggs calculated from Zabel et al., 1995, were: 0.73 PCB-77, 19.44 PCB-81, 75.21 PCB-126, 0.0037 PCB-169, 95.39 total non-ortho PCBs, 6.66 2378-TCDD, 0.025 123678-HCDD, 0.074 2378-TCDF, 0.058 12378-PCDF, 21.71 23478-PCDF, 1.99 123478-PCDF, and 30.52 total PCDD/PCDF.

13.

Snapping turtle eggs were collected from 3 sites in Ontario, Canada, for artificial incubation in June 1998 (de Solla et al., 2002). The three sites were Hamilton Harbor; number of clutches=14 (heavily contaminanted), Akwesasne Mohawk Territory; n=3 (moderately contaminated) and Algonquin Provincial Park; n=14 (reference site). Mean concentrations in ng/g wet weight.  

Hamilton  - HCB 2.79, OCS 1.93, Heptachlor epoxide 3.50, Oxychlordane 31.71, cis-Chlordane 4.29, cis-Nonachlor 33.36, trans-Nonachlor 57.57, DDE 135.14, DDD 2.29, Dieldrin 8.21, Photomirex 19.79, Mirex 42.21, total chlorinated hydrocarbon 343.79, sum PCB 2,956.28. 

Akwesasne - HCB 1.00, OCS ND, Heptachlor epoxide 0.67, Oxychlordane 4.33, cis-Chlordane ND, cis-Nonachlor 2.33, trans-Nonachlor 4.33, DDE 10.00, DDD ND, Dieldrin 3.00, Photomirex 6.00, Mirex 13.00, total chlorinated hydrocarbon 44.67, sum PCB 3,377.00. 

Algonquin - HCB ND, OCS ND, Heptachlor epoxide ND, Oxychlordane 0.67, cis-Chlordane ND, cis-Nonachlor ND, trans-Nonachlor ND, DDE 1.67, DDD ND, Dieldrin ND, Photomirex ND, Mirex ND, total chlorinated hydrocarbon 2.33, sum PCB 20.33.

14.

Snapping turtle eggs were collected in 1999 and 2000 from Lake Sasajewun, Coote’s Paradise, Walpole Island, and 6 sites in the St. Lawrence River Area (Ashpole et al. 2004).  Five eggs from each clutch were collected and pooled for chemical analysis.  Contaminants were analyzed per clutch and detected at the following levels (ng/g wet weight): 32-61,000 total PCBs, 6.4-69 DDE, 0.0024-0.028  total dioxins, 0.0012-0.058 total furans, nd-75 mirex and 0.39-14 dieldrin.  Hg ranged from 50-720 ng/g dw.

15.

Snapping turtle eggs were collected in June 2001 and 2002 from 5 sites in 3 Areas of Concern in the Lake Erie basin and two reference sites outside of the basin for contaminant analysis (de Solla and Fernie 2004). Contaminants were analyzed per clutch and detected at the following levels (ng/g wet weight): 15.7-928.6 total PCBs, 1.33-57.9 DDE, 0.18-6.65 mirex, 0.16-2.42 HCB, 0.11-5.86 dieldrin, 1.22-24.4 sumchlordane, 0.06-1.95 heptachlor epoxide, and nd-1.31 octachlorostyrene.   Eggs were pooled from 4 sites to determine TEQs.  PCB TEQs ranged from 1.83-40.56 pg/g ww.  PCDD/F’s TEQs ranged from 1.28-11.22 pg/g ww.

II.

Cholinesterase-Inhibiting Pesticides

 

No direct exposure data available

III.

Trace Elements, Metals, and Metalloids

1.

Concentrations of Cd in the liver and skeletal muscle of 6 snapping turtles captured in 1976-77 from the Hudson River ranged from <0.06-26.20 g/g wet weight and <0.06- 1.41 g/g, respectively (Stone et al., 1980).

2.

Seventeen snapping turtles were collected from six locations in Minnesota in 1981 for contaminant analysis (Helwig and Hora, 1983). Concentrations of Hg ranged from 0.05-0.30 g/g in meat and were 0.04 g/g in fat. Concentrations of Cd were measured in meat only and were 0.025 g/g for all locations.

3.

Snapping turtles collected during the summers of 1981 and 1982 from brackish and fresh waters of the Hackensack Meadowlands in New Jersey and relatively uncontaminated freshwater sites in Maryland were analyzed for metal and organochlorine contaminants (Albers et al, 1986). Sample sizes per sex ranged between 3-8. Chromium, Cu, Hg, and Zn were detected in both the liver and kidney of all samples. Mean liver concentrations of Cr were significantly lower in New Jersey in males from brackish sites (0.36 g/g wet weight) than other groups (0.60-1.97 g/g). In the kidney, turtles from the two brackish sites showed significantly higher mean Cr concentrations (2.97 and 2.70 g/g) than freshwater locations (<1.26 g/g). Mean Cu concentration in liver was significantly higher in samples from brackish sites (9.72 and 5.17 g/g) than from freshwater sites (<2.08 g/g); however, Cu values in kidney of males from both brackish and freshwater sites in New Jersey were (1.73 g/g) greater than those in Maryland (<1.07 g/g). Mean hepatic Hg concentrations were significantly higher in turtles from brackish water (1.28 and 1.27 g/g) than from freshwater (<0.90 g/g), but showed no difference in mean kidney concentrations, 0.39-0.56 g/g. Mean hepatic Zn concentrations were significantly higher in samples from brackish water (50.38 and 38.95 g/g) than from freshwater (<30.68 g/g), but for kidney only differences were observed between males from brackish water in New Jersey (10.51 g/g) compared to all samples from Maryland (<9.60 g/g). Nickel, detected in at least 80% of all samples, had significantly higher kidney values from turtles from brackish water (1.24 and 1.07 g/g) than those from freshwater (<0.45 g/g). In the liver, Ni was significantly lower in freshwater males from New Jersey (0.13 g/g) than all other samples (0.24-0.99 g/g). Lead and Cd were found in <50% of samples, at means <0.30 g/g for both tissues.

4.

Adult snapping turtles collected in 1987 from Oak Ridge, Tennessee (N=12), and Bearden Creek (N=9), a reference site 5.23 km upstream were analyzed for radionuclide and Hg contamination (Meyers-Schne et al., 1993). Mean Hg levels at the Oak Ridge site were significantly higher in both the kidney (1.30 g/g wet weight) and muscle (0.17 g/g) than at the reference site (0.34 and 0.10 g/g, respectively).

5.

A total of 37 snapping turtles collected from the Big River in the Old Lead Belt of Missouri were analyzed for Pb tissue levels and blood chemistry (Overmann and Krajicek, 1995). Two collection sites were upstream of the Desloge tailings pile (one within the Old Lead Belt and one outside) and one site was downstream. The downstream site tended to have higher Pb values than upstream sites for tissues sampled, and significantly higher values for liver, blood, carapace, and bones. The site outside the Belt had the lowest concentrations for each tissue. Mean Pb concentrations (g/g wet weight) for the three study locations ranged from: 0.126-0.201 muscle, 0.166-0.292 brain, 0.177-0.490 liver, 0.280-2.514 blood, 0.977-33.013 carapace, and 1.015-114.563 bone.

6.

Snapping turtle eggs were collected from 39 clutches in 10 locations on the St. Lawrence River and its tributaries in Canada in 1989 and 1990 (Bonin et al., 1995). Five eggs from each clutch were pooled and analyzed for organochlorines and Hg, and pools from similar localities were averaged. Mercury was detected in all samples analyzed with means ranging from 0.050-0.180 g/g wet weight.

7.

From 1989-1991, Hg concentrations determined in snapping turtle eggs collected from five study locations in the Great Lakes basin and St. Lawrence River were 0.14 g/g wet weight (Bishop et al., 1998).

IV.

Petroleum

 

No residue data available

V.

Other

1.

Mean radioactivity in bone ash of two snapping turtles collected in Mississippi in 1970 was 218 pCi/g (Holcomb et al., 1971).

2.

Snapping turtles were collected from freshwater areas in the South for analysis of the exoskeletal burden of Sr-90 (Jackson et al., 1974). Two individuals from Florida had an observed range of radioactivity of 4.2-16.3 pCi/g of bone ash and two individuals from Georgia had a range of 52.0-119.6 pCi/g.

3.

Adult snapping turtles collected in 1987 from Oak Ridge, Tennessee (N=12), and Bearden Creek (N=9), a reference site 5.23 km upstream, were analyzed for radionuclide and mercury contamination (Meyers-Schne et al., 1993). Mean radionuclide liver levels for Oak Ridge and Bearden Creek, respectively, were 0.174 and <0.0037 Bq/g wet weight Cs-137, and 0.0517 and 0.0037 Bq/g Co-60. In the muscle tissue, Cs-137 means were 0.396 and 0.0037 Bq/g. Mean levels of Sr-90 were 16.5 and <0.18 Bq/g in the bone and 16.6 and <0.18 Bq/g in the carapace. All radionuclides were significantly higher in the Oak Ridge site.

Snapping Turtle Contaminant Response Data

I.

Organochlorine Contaminants

1.

Snapping turtle eggs collected immediately after oviposition from Algonquin Provincial Park and 4 locations in the Great Lakes between 1986 and 1989 were analyzed for hatching success, incidence of deformities, and contaminant concentrations (Bishop et al., 1991). A total of 202 clutches were artificially incubated for the study of embryos, hatchlings, and hatching success. Lynde Creek and Cootes Paradise, which were the sites most contaminated by organochlorines, contained the highest incidence of deformities, including deformities of the tail, hind legs, head, eyes, scutes, forelegs, dwarfism, yolk sac enlargement, and missing claws. The most common deformity, occurring at all sites was abnormality of the tail. Hatching success was lowest in Cootes Paradise with the mean number of unhatched eggs/egg ranging from less than 0.1 to greater than 0.4 between 1986-88. Algonquin Park, the least contaminated site, showed the greatest hatching success with the mean number of unhatched eggs/egg less than 0.1 each year. PCBs were the chemical most strongly associated with deformities and hatching success, though the presence of other chemicals in the eggs was a confounding factor.

2.

From 1989-1991, snapping turtle eggs from seven study locations in the Great Lakes basin and St. Lawrence River, and Algonquin Provincial Park (reference site) in north-central Ontario were collected and artificially incubated (Bishop et al., 1998). Incidence of abnormal development (including curled, bent, twisted, or absent tail; shortened or absent legs or digits; deformed eyes; recessed lower jaw, reduced body size; undeveloped carapace; presence of absence of scutes; and unresorbed yolk sac) increased significantly with increasing concentrations of polychlorinated aromatic hydrocarbons, particularly PCDD and PCDF, yet was not correlated with TEQs in eggs. The percentage of unhatched eggs, due to infertility or early interruption of embryonic development, ranged from 0-10% for all but a single clutch in which 40% of eggs failed to hatch. EROD and cytochrome P4501A activities were significantly higher in liver of hatchlings from Lake Ontario compared to the reference site. Porphyria was not observed in turtles from either site.

3.

Three snapping turtles were anesthetized, and intestinal mucosa, cloacal bladder, kidney, and liver were incubated with 0.53, 5.3, and 53 M DDT for 30 min to measure ATPase inhibition (Phillips and Wells, 1994).  At 53 M DDT, total (Na+, K+,Mg2+)-dependent ATPase activity was inhibited by approximately 52%in the intestinal mucosa, 45%in the cloacal bladder, 25% in kidney, and 38% in liver.

4.

In 1995, sex differentiation and reproductive endocrine function was studied in adult snapping turtles from organochlorine-contaminated sites in Southern Ontario (de Solla et al., 1998). The ratio of precloacal length to the posterior lobe of the plastron (PPR), the value which is normally indicative of sex, was significantly smaller in males from three contaminated sites in the Great Lakes than males from the reference site. A significantly larger proportion of males from one of the contaminated sites had a PPR that overlapped with that of females than PPRs of males at a reference site, confounding identification of sex based on secondary sexual characteristics alone. Little change was observed in plasma 17 -estradiol or testosterone concentrations.

5.

Snapping turtle eggs collected in 1996 from uncontaminated sites in Algonquin Park, Ontario were subject to topical application of DDE at doses selected to simulate concentrations found in the Great Lakes (0.52-65 g/5 l ethanol) or estradiol-17  (positive control) (Portelli et al., 1999).  Eggs were incubated at a male-producing temperature.  Though eggs treated with estradiol did produce females at this temperature, eggs treated with DDE did not effect sexual differentiation at any exposure level.  It was concluded that DDE, at levels that are currently found at the Great Lakes, does not cause feminization of snapping turtles during embryonic development.

6.

Snapping turtle eggs were collected from 3 sites in Ontario, Canada, for artificial incubation in June 1998 (de Solla et al., 2002). The three sites were Hamilton Harbor; number of clutches=14 (heavily contaminated), Akwesasne Mohawk Territory; n=3 (moderately contaminated) and Algonquin Provincial Park; n=14 (reference site). Differences in sexually dimorphic morphology were found between contaminated and uncontaminated sites. Alterations in secondary sexual characteristics occur in early development, suggesting transfer of organochlorines from exposed females to offspring.

II.

Cholinesterase-Inhibiting Pesticides

 

No response data available

III.

Trace Elements, Metals, and Metalloids

1.

Blood plasma analysis was performed on snapping turtles collected during the summers of 1981 and 1982 from brackish and freshwater sites high in metal contamination in the Hackensack Meadowlands in New Jersey and relatively uncontaminated freshwater sites in Maryland (Albers et al, 1986). Turtles from Maryland had significantly higher ALAD and significantly lower hemoglobin than turtles from brackish waters in New Jersey, and significantly lower albumin, glucose, and total protein than turtles from freshwater in New Jersey. None of the differences were thought to indicate physiological impairment related to contaminants.

2.

A total of 37 snapping turtles collected from the Big River in the Old Lead Belt of Missouri were analyzed for Pb tissue levels and blood chemistry (Overmann and Krajicek, 1995). Two collection sites that were upstream of the Desloge tailings pile (one within the Old Lead Belt and one outside) tended to have lower Pb levels than one site was located downstream. Blood indices measured were hematocrit, hemoglobin, and plasma glucose, osmolality, and Cl, and were found not to differ between capture locations. delta-s.gif (58 bytes)-ALAD activity was highest in the upstream area outside the Belt, followed by the upstream area inside the Belt, followed by the downstream area, with significant differences between sites. Enzyme activity was depressed (>90%) in turtles from the most contaminated site in relation to those from the "cleanest" site. Significant negative correlations were found between blood Pb concentrations and delta-s.gif (58 bytes)-ALAD activities.

3.

An adult male snapping turtle presented to the Tufts Wildlife Clinic in Grafton, Massachusetts had a Pb concentration in blood of 3.6 g/g and was diagnosed with Pb poisoning (Borkowski, 1997). A Pb sinker was recovered from the intestine and Pb concentrations declined to undetectable levels after 6 weeks with chelation therapy.

IV.

Petroleum

 

No response data available

V.

Other

1.

Six snapping turtles were collected from a polluted stretch of the Kalamazoo River, Otsego, Michigan in 1965 (Gibbons, 1968).  Turtles were aged using carapace lengths and annular ring lengths.  The oldest turtle was 15 years old.  Mean carapace length increased by an average of 32 mm/yr for the first 6 years, although the growth rate declined after the first year.

2.

Snapping turtles were collected from a marsh at Great Meadows National Wildlife Refuge, Concord, Massachusetts in 1976, which received 4.0-5.5 mg/l P from sewage treatment plant effluent (Graham and Perkins, 1976).  Mean growth rate, measure by carapace length, was 26 mm/yr.  The two oldest individuals, which were 7 years old, grew by 26 mm/yr for the first 6 years, and then grew 48.2 mm in their most recent year.  The growth surge was attributed to a dietary switch to larger prey such as waterfowl. 

3.

Adult snapping turtles collected from Oak Ridge, Tennessee (N=12) in 1987 were found to have significantly greater levels of radionuclide and mercury contamination, and 3.2 times as many breaks in DNA strands compared to those from Bearden Creek (N=9), a reference site 5.23 km upstream (Meyers-Schne et al., 1993).  

References for Snapping Turtle

Albers, P.H., L. Sileo, and B.M. Mulhern. 1986. Effects of environmental contaminants on snapping turtles of a tidal wetland. Arch. Environ. Contam. Toxicol. 15:39-49.

Ashpole, S.L., C.A. Bishop, and R.J. Brooks.  2004.  Contaminant residues in Snapping Turtle (Chelydra serpentina) eggs from the Great Lakes – St. Lawrence River Basin (1999-2000).  Arch. Environ. Contam. Toxicol. 47:240-252.

Behler, J.L., and F.W. King. 1979. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, New York. 743 pp.

Bishop, C.A., R.J. Brooks, J.H. Carey, P. Ng, R.J. Norstrom, and D.R.S. Lean. 1991. The case for a cause-effect linkage between environmental contamination and development in eggs of the common snapping turtle (Chelydra s. serpentina) from Ontario, Canada. J. Toxicol. Environ. Health 33:521-547.

Bishop, C.A., G.P. Brown, R.J. Brooks, D.R.S. Lean, and J.H. Carey. 1994. Organochlorine contaminant concentrations in eggs and their relationship to body size, and clutch characteristics of the female common snapping turtle (Chelydra serpentina serpentina) in Lake Ontario, Canada. Arch. Environ. Contam. Toxicol. 27:82-87.

Bishop, C.A., D.R.S. Lean, R.J. Brooks, J.H. Carey, and P. Ng. 1995. Chlorinated hydrocarbons in early life stages of the common snapping turtle (Chelydra serpentina serpentina) from a coastal wetland on Lake Ontario, Canada. Environ. Toxicol. Chem. 14:421-426.

Bishop, C.A., P. Ng, R.J. Norstrom, R.J. Brooks, and K.E. Pettit. 1996. Temporal and geographic variation of organochlorine residues in eggs of the common snapping turtle (Chelydra serpentina serpentina) (1981-1991) and comparisons to trends in the herring gull (Larus argentatus) in the Great Lakes Basin in Ontario, Canada. Arch. Environ. Contam. Toxicol. 31:512-524.

Bishop, C.A., P. Ng, K.E. Pettit, S.W. Kennedy, J.J. Stegeman, R.J. Norstrom, and R.J. Brooks. 1998. Environmental contamination and developmental abnormalities in eggs and hatchlings of the common snapping turtle (Chelydra serpentina serpentina) from the Great Lakes-St. Lawrence River basin (1989-1991). Environ. Pollut. 101:143-156.

Bonin, J., J-L. DesGranges, C.A. Bishop, J. Rodrigue, A. Gendron, and J.E. Elliott. 1995. Comparative study of contaminants in the mudpuppy (Amphibia) and the common snapping turtle (Reptilia), St. Lawrence River, Canada. Arch. Environ. Toxicol. 28:184-194.

Borkowski, R. 1997. Lead poisoning and intestinal perforations in a snapping turtle (Chelydra serpentina) due to fishing gear ingestion. J. Zoo Wildl. Med. 28:109-113.

Bryan, A.M., W.B. Stone, and P.G. Olafsson. 1987a. Disposition of toxic PCB congeners in snapping turtle eggs: Expressed as toxic equivalents of TCDD. Bull. Environ. Contam. Toxicol. 39: 791-796.

Bryan, A.M., P.G. Olafsson, and W.B. Stone. 1987b. Disposition of low and high environmental concentrations of PCBs in snapping turtle tissues. Bull. Environ. Contam. Toxicol. 38: 1000-1005.

de Solla, S.R., C.A. Bishop, D. Van der Kraak, and R.J. Brooks. 1998. Impact of organochlorine contamination on levels of sex hormones and external morphology of common snapping turtles (Chelydra serpentina serpentina) in Ontario, Canada. Environ. Health Perspect., 106: 253-260.

de Solla, S.R., C.A. Bishop, H. Lickers, and K. Jock. 2001. Organochlorine pesticides, PCBs, dibenzodioxin, and furan concentrations in common snapping turtles (Chelydra serpentina serpentina) in Akwesasne, Mohawk Territory, Ontario, Canada. Arch. Environ. Contam. Toxicol. 40: 410-417.

de Solla, S.R., C.A. Bishop and R.J. Brooks. 2002. Sexually dimorphic morphology of hatchling snapping turtles (Chelydra serpentina) from contaminated and refernces sites in the Great Lakes and St. Lawrence River basin, North America. Environ. Toxicol. Chem. 21:922-929.

de Solla, S.R., and K.J. Fernie.  2004.  Characterization of contaminants in snapping turtles (Chelydra serpentina) from Canadian Lake Erie Areas of Concern: St. Clair River, Detroit River, and Wheatley Harbor.  Environ. Pollut. 132:101-112.

Gibbons, J.W. 1968. Growth rates of the common snapping turtle, Chelydra serpentina, in a polluted river. Herpetologica 24:266-267.

Graham, T.E. and R.W. Perkins. 1976. Growth of the common snapping turtle, Chelydra s. serpentina, in a polluted marsh. Bull. Maryland Herpet. Soc. 12:123-125.

Hebert, C.E., V. Glooschenko, V., G.D. Haffner, and R. Lazar. 1993. Organic contaminants in snapping turtle (Chelydra serpentina) populations from southern Ontario, Canada. Arch. Environ. Contam. Toxicol. 24:35-43.

Helwig, D.D. and M.E. Hora. 1983. Polychlorinated biphenyl, mercury, and cadmium concentrations in Minnesota snapping turtles. Bull. Environ. Contam. Toxicol. 30:186-190.

Holcomb, C.H., C.G. Jackson, Jr., M.M. Jackson, and S. Kleinbergs.  1971.  Occurrence of radionuclides in the exoskelton of turtles.  3rd National Symposium on Radioecology, Oak Ridge, Tennessee, pp. 385-389. 

Jackson, Jr., C.G., C.M. Holcomb, S. Kleinbregs-Krisans, and M.M. Jackson. 1974. Variation in strontium-90 exoskeletal burdens of turtles (Reptilia: Testudines) in southeastern United States. Herpetologica 30:406-409.

McVey, M., K. Hall, P. Trenham, A. Soast, L. Frymier, and A. Hirst. 1993. Wildlife Exposure Factors Handbook, Volume I. U.S. Environmental Protection Agency, Washington D.C., EPA/600/R-93/187a.

Meyers-Schne, L., L.R. Shugart, J.J. Beauchamp, and B.T. Walton. 1993. Comparison of two freshwater species as monitors of radionuclide and chemical contamination: DNA damage and residue analysis. Environ. Toxicol. Chem. 12:1487-1496.

Olafsson, P.G., A.M. Bryan, and W. Stone. 1987. PCB congener-specific analysis: A critical evaluation of toxic levels in biota. Chemosphere 16:2585-2593.

Olafsson, P.G., A.M. Bryan, B. Bush, and W. Stone. 1983. Snapping turtles - A biological screen for PCB's. Chemosphere 12:1525-1532.

Overmann, S.R., and J.J. Krajicek. 1995. Snapping turtles (Chelydra serpentina) as biomonitors of lead contamination of the Big River in Missouris Old Lead Belt. Environ. Toxicol. Chem. 14:689-695.

Pagano, J.J., P.A. Posenbaum, R.N. Roberts, G.M. Sumner, and L.V. Williamson.  1999.  Assessment of maternal contaminant burden by analysis of snapping turtle eggs.  J. Great Lakes Res. 25:950-961. 

Phillips, J.B., and M.R. Wells. 1974. Adenosine triphosphatase activity in liver, intestinal mucosa, cloacal bladder, and kidney tissue of five turtle species following in vitro treatment with 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane(DDT). J. Agr. Food Chem. 3:404-407.

Portelli, M.J., S.R. de Solla, R.J. Brooks, and C.A. Bishop.  1999.  Effect of dichlorodiphenyltrichloroethane on sex determination of the common snapping turtle (Chelydra serpentina serpentina).  Ecotox. Environ. Safety 43:284-291.

Punzo, F., J. Laveglia, D. Lohr, and P.A. Dahm. 1979. Organochlorine insecticide residues in amphibians and reptiles from Iowa and lizards from the southwestern United States. Bull. Environ. Contam. Toxicol. 21:842-848.

Rappe, C., H.R. Buser, D.L. Stalling, L.M. Smith, and R.C. Dougherty. 1981. Identification of polychlorinated dibenzofurans in environmental samples. Nature 292:524-526.

Ryan, J.J., W.B. Stone, P. OKeefe, and J.F. Gierthy. 1986. 2,3,7,8-tetrachlorodibenzo-p-dioxin and related dioxins and furans in snapping turtle (Chelydra serpentina) tissues from the Upper St. Lawrence River. Chemosphere 15:537-548.

Schwartz, T.R., D.L. Stalling, and C.L. Rice. 1987. Are polychlorinated biphenyl residues adequately described by Aroclor mixture equivalents? Isomer-specific principal components analysis of such residues in fish and turtles. Environ. Sci. Technol. 21:72-76.

Stone, W., E. Kiviat, and S.A. Butkas. 1980. Toxicants in snapping turtles. N.Y. Fish Game J. 27:39-50.

Struger, J., J.E. Elliott, C.A. Bishop, M.E. Obbard, R.J. Norstrom, D.V. (Chip) Weseloh, M. Simon, and P. Ng. 1993. Environmental contaminants in eggs of the common snapping turtle (Chelydra serpentina serpentina) from the Great Lakes-St. Lawrence River Basin of Ontario, Canada (1981, 1984). J. Great Lakes Res. 19:681-694.

Watson, M.R., W.B. Stone, J.C. Okoniewski, and L.M. Smith. 1985. Wildlife as monitors of polychlorinated biphenyls and other organochlorine compounds from a hazardous waste site. Trans. Northeast Sect. Wildl. Soc. 42:91-104.

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