2004 Progress Report: Effects of Multiple Stressors on Aquatic Communities in the Prairie Pothole Region

EPA Grant Number: R830879
Title: Effects of Multiple Stressors on Aquatic Communities in the Prairie Pothole Region
Investigators: Schoff, Pat , Guntenspergen, Glenn R. , Johnson, Carter , Johnson, Lucinda
Current Investigators: Schoff, Pat , Guntenspergen, Glenn R. , Johnson, Carter , Johnson, Lucinda , Olker, Jennifer H.
Institution: University of Minnesota - Duluth
EPA Project Officer: Packard, Benjamin H
Project Period: April 7, 2003 through April 6, 2007
Project Period Covered by this Report: April 7, 2004 through April 6, 2005
Project Amount: $746,433
RFA: Developing Regional-Scale Stressor-Response Models for Use in Environmental Decision-making (2002) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Ecosystems

Objective:

  1. Quantify relationships among differing land use, amphibian community structure and composition in the prairie pothole region.
  2. Quantify relationships among physical and chemical wetland attributes on amphibian organismal and community responses.
  3. Quantify the effects of multiple stressors on health and organismal responses of Rana pipiens.
  4. Predict potential effects of multiple stressors on prairie pothole wetlands and associated amphibian communities.

Progress Summary:

To quantify the effects of multiple stressors on amphibians we are conducting investigations at three spatial scales: landscape (extensive study), wetland (intensive study), and mesocosm. Extensive studies sites are distributed across the U.S. portion of the Prairie Pothole Region (PPR; Figure 1); intensive study sites are concentrated in east-central South Dakota. Mesocosm studies were conducted at the Oak Lake Field Station of South Dakota State University.

Landscape Scale: GIS-based site selection and inspection for the extensive (landscape scale) survey began in February 2004 and continued into April. Beginning in April 2004, 67 sites were selected and sampled in eleven cells (cells = 12 X 12 miles) across the PPR (Figure 1; Tables 1 & 2). In April 2005 we re-sampled four of the eleven cells (26 wetlands), and sampled 47 additional wetlands in seven cells. Site selection was conducted as previously described. A total of 114 wetlands were sampled in the extensive study.

Wetland Scale: We selected eight additional wetlands for 2004 surveys and sampling, resulting in a total of 35 wetlands in the intensive (wetland) portion of the study (Table 1). Amphibian surveys and water sampling took place from mid-April to mid-August.

Amphibian surveys: Amphibian community assessments were conducted in both intensive and extensive study wetlands in three surveys of breeding adults, larvae, and egg masses. Nighttime calling surveys were conducted during April, May-June, and July, in accordance with North American Amphibian Monitoring Program (NAAMP) protocol. Time-constrained daytime visual encounter surveys (VES) identified amphibian adults, larvae, and eggs as well as potential predators. Larval sampling was conducted with dip nets or minnow traps. Amphibians were identified, measured, staged, and examined for malformations prior to release. In addition, several wetlands in the intensive study area were surveyed for malformed metamorphs in late July.

Water quality/depth: Water depth, quality (pH, salinity, temperature, and conductivity), and habitat characteristics (wetland size, wetland type, dominant cover), were assessed three times during the summer field season in extensive sites and weekly (up to 13 weeks, depending on the persistence of water in the wetland) at intensive sites (Table 5). Water samples were collected twice in 2003 and three times in 2004 for analysis of chlorophyll-a (Chl-A), total suspended solids (TSS), true color (color), and dissolved organic carbon (DOC). Incident ultraviolet radiation (UVR) and attenuation was also measured at 18 sites in 2003 and 33 sites in 2004. In 2004, water was sampled for atrazine. In addition, water temperature was recorded every 2 hours throughout both years at all intensive sites.

Mesocsoms: The mesocosms set up in 2004 failed to produce live metamorphs at the end of the season. Possible reasons for this lack of success may involve unknown toxins from plant material used for feeding the animals, or metals leaching from water holding tanks. Experience from 2004 has led to successful mesocosm-scale experiments in 2005.

Accomplishments: We sampled 102 sites in seasonal and semi-permanent wetlands with agricultural (CROP) or grassland/prairie (grass) land cover surrounding wetlands (Table 1).

Table 1: Number of wetlands by treatment type in the intensive (wetland) and extensive (landscape) studies for 2003 and 2004.

 

 

Semi-permanentc

Seasonald

Total

CROPa

Intensive

6

5

11

Extensive

12

23

35

Combined

18

28

46

Grassb

Intensive

13

11

24

Extensive

16

16

32

Combined

29

27

56

Total Sites

47

55

102

a Wetlands with 70 percent or greater row-crop coverage in the 90 m buffer surrounding the basin.
b Wetlands with 70 percent or greater grassland/prairie or pasture/hay coverage in the 90 m buffer surrounding the basin.
c Semi-permanent hydrologic regime from USGS wetland BASINS data.
d Seasonal hydrologic regime from USGS wetland BASINS data.

Amphibian communities

Eleven amphibian species were observed in total; species richness per wetland ranged from zero to five (Table 2). In 2003, at least five amphibian species were identified in the intensive sites. No differences in species richness were observed between wetlands surrounded by row crop versus grassland; however, more species were observed at wetlands in the Central Tall and Northern Tall Grassland Ecoregions than in the Prairie Coteau, Northern Short and Northern Mixed Grassland Ecoregions.

Northern Leopard Frog (Rana pipiens) was represented across the entire Prairie Pothole region during the 2004 surveys, with observations of adults in 44 sites (Table 2) and evidence of breeding (egg masses, larvae or metamorphs; Table 3) in 29 sites. Based on a logistic regression, the probability of R. pipiens presence was significantly influenced by the interaction of hydrology and land cover (p = 0.02; Table 4). The probability of R. pipiens breeding in a wetland was significantly influenced by hydrology, but not by landcover or an interaction of the two treatments (p = 0.08; Table 4).

Table 2. Amphibian species richness for each species by study level (Extensive & Intensive) and treatment type: Semi-permanent crop (SP-c), Semi-permanent grass (SP-g), Seasonal crop (SS-c), and Seasonal grass (SS-g).

 

EXTENSIVE
# sites with species present

INTENSIVE
# sites with species present

Total

 

SP-c

SP-g

SS-c

SS-g

Total

SP-c

SP-g

SS-c

SS-g

Total

Northern Cricket Frog
(Acris crepitans)

0

1

1

1

3

0

0

0

0

0

3

Tiger Salamander
(Ambystoma tigrinum)

0

0

0

0

0

1

1

0

0

2

2

American Toad
(Bufo americanus)

1

5

2

2

10

2

6

4

4

16

26

Great Plains Toad
(Bufo cognatus)

0

0

4

1

5

0

0

0

0

0

5

Canadian Toad
(Bufo hemiophrys)

5

8

3

1

17

0

2

2

0

4

21

Any Toad Species (inc. unknowns & hybrids)
(Bufo spp.)

5

10

6

4

25

2

6

4

6

18

43

Treefrog species
(Hyla spp.)

0

0

1

0

1

0

0

0

0

0

1

Western Chorus Frog
(Pseudacris triseriata)

11

15

21

14

61

6

13

4

8

31

92

Plains Leopard Frog
(Rana blairi)

0

0

2

0

2

0

0

0

0

0

2

Bullfrog
(Rana catesbeiana)

0

1

0

1

2

0

0

0

0

0

2

Northern Leopard Frog
(Rana pipiens)

0

4

16

2

22

2

9

2

8

21

43

Wood Frog
(Rana sylvatica)

8

7

5

5

25

0

0

0

0

0

25

Table 2, continued. Amphibian species richness and presence & evidence of breeding for each species by study level (Extensive & Intensive) and treatment type: Semi-permanent crop (SP-c), Semi-permanent grass (SP-g), Seasonal crop (SS-c), and Seasonal grass (SS-g).

 

EXTENSIVE
# sites with breeding evidence
(eggs, larvae, or metamorphs present)

INTENSIVE
# sites with breeding evidence
(eggs, larvae, or metamorphs present)

Total

 

SP-c

SP-g

SS-c

SS-g

Total

SP-c

SP-g

SS-c

SS-g

total

Northern Cricket Frog
(Acris crepitans)

0

0

1

0

1

0

0

0

0

0

1

Any Toad Species
(Bufo spp.)

0

3

3

1

7

0

0

3

1

4

11

Western Chorus Frog
(Pseudacris triseriata)

2

0

2

1

5

3

4

2

5

14

19

Plains Leopard Frog
(Rana blairi)

0

0

1

0

1

0

0

0

0

0

1

Bullfrog
(Rana catesbeiana)

0

0

0

1

1

0

0

0

0

0

1

Northern Leopard Frog
(Rana pipiens)

0

1

9

1

11

2

6

2

7

17

28

Wood Frog
(Rana sylvatica)

2

3

1

1

7

0

0

0

0

0

7

Species richness average
(range)

2.1
(1-4)

2.6
(0-5)

2.4
(0-5)

1.7
(0-3)

2.2
(0-5)

1.8
(1-3)

2.4
(1-4)

2.4
(1-4)

1.8
(0-3)

2.1
(0-4)

2.2
(0-5)

Table 3. Summary of potential indicators and measures of amphibian breeding success (water levels, presence, evidence of breeding, # of metamorphic R. pipiens) for intensive study wetlands in 2003 and 2004.

Potential indicators and measures
Of amphibian breeding success

2003

2004

# sites surveyed

27

35

# sites dry in April/May

0 (0%)

10 (29%)

# sites dry at end of season

22 (81%)

15 (43%)

# sites with R. pipiens present

23 (85%)

22 (63%)

# sites with R. pipiens breeding

17 (62%)

18 (51%)

# sites with enough metamorphic R. pipiens for malf. surveya

11 (41%)

7 (20%)

Total # R. pipiens metamorphs captured at all sitesb

1389

736

    a if < 10 metamorphic R. pipiens caught in 1.5 people hours metamorphic malformation survey not conducted
    b metamorphic malformation survey time and sample size constrained: continued until 120 metamorphic amphibians captured or up to 2 hours

Table 4. Proportion of wetlands in each treatment with R. pipiens present or breeding in 2004 for the combined intensive and extensive study wetlands.

Proportion of sites with Rana pipiens present

 

 

Hydrology

 

 

 

Semi-permanent

Seasonal

total

Land Cover

CROP

0.11*

0.64

0.43

Grass

0.44

0.37

0.41

 

total

0.32

0.51

0.43

Proportion of sites with Rana pipiens breeding

 

 

Hydrology

 

 

 

Semi-permanent

Seasonal

total

Land Cover

CROP

0.11

0.39

0.28

Grass

0.24

0.30

0.27

 

total

0.19*

0.35

0.27

* significantly different from other treatments (logistic regression, α = 0.1)

The presence of other common species, such as wood frog (Rana sylvatica, present in 25 sites) or western chorus frog (Pseudacris triseriata, present in 92 sites), was not significantly predicted by treatment, interaction of treatments, or ecoregion.

Although more sites were surveyed in 2004 than 2003, fewer R. pipiens metamorphs were captured. Precipitation in the intensive study area was greatly reduced during the winter and early spring of 2004, compared with the previous year, which resulted in many study sites drying before or during the R. pipiens breeding season. Additionally, several of the sites that had abundant metamorphic R. pipiens in 2003 were dry by early July 2004. We observed R. pipiens and evidence of breeding in fewer wetlands in 2004 than in 2003, and metamorph populations appeared greatly reduced, even in wetlands with successful breeding and adequate water levels. This relationship between precipitation and amphibian breeding success may predict the effects of hydrologic changes caused by climate change.

Water Quality

Based on a repeated measures ANOVA including both intensive and extensive sites, hydrology and land cover were significant predictors of several water quality parameters. Seasonal wetlands were significantly more alkaline than semi-permanent wetlands, with seasonal crop wetlands significantly more alkaline than all other treatments (Table 5; Figure 2; p <0.001). Land cover also influenced specific conductivity (μS) and DOC (ppm), both of which were significantly higher in wetlands surrounded by grassland than row crop [specific conductivity, p = 0.056 and DOC, p < 0.0001; intensive sites only] (Table 5). As expected, hydrologic regime influenced maximum depth and water temperature (both day and nighttime). Semi-permanent wetlands were deeper and colder than seasonal wetlands, which could affect amphibian breeding and development.

Table 5. Water quality and general habitat characteristics means (range) by study level (Extensive & Intensive) and treatment type: Semi-permanent crop (SP-c), Semi-permanent grass (SP-g), Seasonal crop (SS-c), and Seasonal grass (SS-g).

Table 5.

Atrazine

Water was collected for atrazine assessment three times during 2004: Survey 1, April 3 - April 30; Survey 2, May 5 – June 11; and Survey 3, June 17 – June 28. The samples were filtered through 0.2 μm membranes into 20 ml plastic vials, placed on ice during transport and held at or below 4°C until analysis using an ELISA kit (Abraxis, Warminster, PA).Atrazine concentrations ranged from non-detectable (<0.01 ppb) to 7.124 ppb, with concentrations ≥0.01 ppb present in 71% of wetlands sampled in Survey 1, and in 100% of wetlands in Surveys 2 and 3. Mean atrazine concentrations differed between surveys (Table 6).

Atrazine concentrations were higher in wetlands where land use within a 90 m buffer was classified as >70 % crop than in those where grassland comprised the greatest proportion of the buffer (≤7.124 ppb v. ≤0.657 ppb, respectively). Semi-permanent wetlands with corn in the 90 m buffer had higher mean atrazine concentrations (Figure 3), and corn presence was the best overall predictor of wetland atrazine concentration for Surveys 2 and 3 (ANOVA, p = <0.001-0.025; Table 6). However, neither land use (crop v. grassland; ANOVA, p = 0.662) nor hydrologic regime (ANOVA, p = 0.878) were significant predictors of maximum atrazine concentration in April-July 2004.

Table 6. Mean atrazine concentration (ppb ±S.E.) in wetlands of the Prairie Pothole Region by survey and presence/absence of corn within a 90m buffer, with p-values for effect of corn (ANOVA).

 

Survey 1
April 3 – April 30 2004
(p=0.897)

Survey 2
May 5 - June 11 2004
(p=0.025)

Survey 3
June 17 – June 28 2004
(p<0.001)

Present

0.064 ± .034
n=17

0.140 ± .026
n=19

0.783 ± .372
n=21

Corn

Absent

0.038 ± .008
n=74

0.092 ± .009 n=79

0.144 ± .013
n=81

Overall

0.043 ± .009
n=91

0.101 ± .009
n=98

0.275 ± .080 n=102

Malformation Study

Malformation assessments were conducted in wetland scale (intensive study area; east-central South Dakota) wetlands where sufficient numbers (~100) of metamorphs were observed. At each site, 100-120 R. pipiens metamorphs were collected using dip nets, snout-vent and snout-tail length were measured, and individuals were thoroughly examined for skeletal, eye, and cutaneous malformations. In 2003, 21 sites were surveyed. Eleven (52.4%) contained malformed R. pipiens metamorphs, and 3.0% (45/1489) of these individuals had at least one identifiable malformation. Hindlimb malformations comprised 80% of the total, with ectrodactyly (missing digit) occurring in 69% of specimens.

Using the same criteria in 2004, 53.8% (7/13) of the surveyed sites contained malformed R. pipiens, with ~3.5% (26/748) of R. pipiens metamorphs captured exhibiting malformations. As in 2003, hindlimb malformations constituted the majority of the total (71.4 %; Figure 4).

Four of the intensive study wetlands produced malformed specimens in both 2003 and 2004. Malformation prevalence was not significantly correlated with surrounding land use or atrazine concentration.

Identical criteria were used to assess malformations in the extensive study area, however, only 14% (1/7) sites contained malformed R. pipiens, and in these, only 0.39 % (2/510) of R. pipiens metamorphs captured were malformed. Malformation prevalence was not significantly correlated with land use or atrazine concentration.

UV Radiation (UVR)

UVR was rapidly attenuated through the water column; however amphibian larvae could be exposed to damaging levels in the upper 10 cm of the water column of many of the study wetlands. We are developing attenuation models for ultraviolet radiation-B in the intensive study wetlands; preliminary analysis indicates that DOC and color, which are the dominant UVR attenuators in lakes, do not appear to be primary influences on attenuation in PPR wetlands.

QA Issues

No obvious major quality issues were encountered during the second year of the study. However, negative results from the mesocosm experiments suggest that unknown toxic processes were taking place either in the mesocosms themselves, in the natural material used as food sources, or in the conditioning process for the water used to supply the mesocosms. Steps to ameliorate all of these possibilities have been carried out for the 2005 mesocosm experiments, which are currently in progress.

Future Activities:

Field efforts in 2005 will originate at NRRI, and will feature an expanded set of sites for the extensive portion of the study. Intensive sites will be monitored on a schedule similar to those of the extensive survey. Mesocosm work will be conducted at NRRI.

Acknowledgments and disclaimers:

This research has been supported by a grant from the U.S. Environmental Protection Agency’s Science to Achieve Results (STAR) program. Award number RD-83087901.

Although the research described in this report has been funded wholly or in part by the U.S. Environmental Protection Agency’s STAR program through grant (number), it has not been subjected to any EPA review and therefore does not necessarily reflect the views of the Agency, and no official endorsement should be inferred.

Journal Articles:

No journal articles submitted with this report: View all 13 publications for this project

Supplemental Keywords:

water, global climate, sensitive populations, animal, ecology, hydrology, histology, modeling, monitoring, surveys, Midwest, Iowa, IA, South Dakota, SD, Minnesota, MN, North Dakota, ND, EPA Region 7, EPA Region 8, agriculture,, RFA, Scientific Discipline, Air, Toxics, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, RESEARCH, Ecosystem/Assessment/Indicators, climate change, pesticides, Air Pollution Effects, Monitoring/Modeling, Ecological Effects - Environmental Exposure & Risk, Monitoring, Regional/Scaling, Environmental Monitoring, Agroecosystems, Ecological Risk Assessment, Atmosphere, anthropogenic stresses, ecological effects, anthropogenic stress, ecological exposure, biomarkers, ecosystem assessment, stressors, UV effects, thermal stratification, climatic influence, praire pothole region, amphibians, coral bleaching, coastal zone, natural stressors, modeling, multiple stressors, prairie pothole region, biomonitoring, regional scale impacts, ecosystem indicators, amphibian models, agriculture, aquatic ecosystems, environmental stressors, water quality, atrazine, hydrologic modeling, Global Climate Change, land use

Relevant Websites:

No web sites have been established specifically for this project. The Natural Resources Research Institute website (http://www.nrri.umn.edu Exit ) contains descriptions of all sponsored projects carried out through the Institute.

Progress and Final Reports:

Original Abstract
  • 2003 Progress Report
  • 2005
  • Final Report