Assessment of Rice Farming and AgricuJtural Chemical Impacts on Amphibians of the Anahuac ...

47 Pages·2008·4.48 MB·English

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DEPARTMENT OF THE INTERIOR
U.S. FISH AND WILDLIFE SERVICE
REGION2
Assessment of Rice Farming and AgricuJtural Chemical
Impacts on Amphibians of the Anahuac National Wildlife Refuge
by
Brian W. Cain, PhD
U. S. Fish & Wildlife Service,
Cindy Howard, PhD
and
Heather Holston, MS
Univ. of Houston Clear Lake
for
Fred Werner, Supervisor
Clear Lake Field Office
17629 El Camino Real Suite 211
Houston, Texas
January,2002
ABSTRACT
This study was designed to determine if the use of agricultural pesticides and
herbicides used in rice farming and Chinese tallow tree control have a noticeable effect
on populations of amphibians on the Anahuac National Wildlife Refuge. Two hour
searches by a two person team were conducted along specific transects in a moist soil
management unit, rice fields, and fallowed rice fields, twice a month between March and
July, and once a month between August and November for two years. All amphibians
seen or heard were recorded, or captured when possible, and examined for gross
malformations. Small dip nets were used to collect tadpoles for external examination and
growth observations.
Three herbicides [Starn M-4 (propanil), Grazon P+D (picloram + 2,4-D) and
Arrosolo (propanil + molinate)] that were approved for use, and used on the Refuge
during the study, were tested for toxicity in the Frog Embryo Teratogenesis Assay
Xenopus (FETA X) of these chemicals to larval amphibians. Dose-response curves are
presented and the LC s were calculated for Grazon P+D and Arrosolo (33% propanil, 33
50
% molinate). Starn M-4 did not yield a definitive test. The LC for Grazon P+D was
50
between 25 and 50 mg/L and for Arrosolo the LC was 13.5 mg/L. Calculated exposure
50
concentration of Arrosolo used in rice farming on the Refuge was less than 0.6 mg/L,
which is 200 times lower than the LC determined in the FETA X assay.
50
Fourteen species of frogs, toads and salamanders were recorded on the Refuge
during this study. Three species (three-toed amphiuma, western lesser siren and pig frog)
were not previously recorded in Chambers County, Texas. Six species of amphibians
recorded from Chambers County (Dixon 1987) were not seen during this study (Table 1) .
In August the moist soil management unit generally contained the largest population of
amphibians averaging 26 individuals per hectare and represented 10 species. The rice
fields had the second largest population of amphibians and averaged 24 individuals per
hectare, representing 11 species, during July. The rice field was usually drained and left
to dry out in August for harvesting. The fallowed rice fields had only eight species of
amphibians and much lower densities. These fields were not flooded and stayed dry for
long time periods during the drought period of 1999 and 2000. Surveys in the months of
December, January or February did not yield any amphibians along the transects.
There were no malformed frogs, toads or tadpoles collected during this study
which indicates that the herbicides currently used on the Anahuac National Wildlife
Refuge are not having a measurable adverse affect on the amphibian populations. Habitat
alteration such as discing, leveling, and terracing the area for rice planting appeared to
have a large but short-term negative effect on the presence, reproduction and abundance
of amphibians. The role of concentrating predators such as birds, snakes and mammals,
in the moist soil unit and the rice fields on the amphibian populations was not evaluated,
but appears as if it could be substantial.
Project No. 2N35, 9920001.2
TABLE OF CONTENTS
Page
1. LIST OF TABLES .... ... ... ... .... . .. ... ... ................ . ....... ii
2. LIST OF FIGURES ... ... ... ... ... .... ................. ..... .. ...... iii
3. INTRODUCTION ...... ... ... .. . .. .. ... ... ....................... ... 1
4. OBJECTIVES ..................... ...... .. .. ............... .. ...... 6
5. STUDY AREA .. ... ......... ........................ ... . ............ 7
General Settinf: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Climate and Soil: ................................................. 10
Vefelative Description: ...................................... . ..... 10
6. METHODS ........................................ .. .............. 12
Amphibian Surveys: ......... ............. ... ... .. ... .............. 12
In-situ Bioassay: .. ... ... ...... ............................... . .... 13
7. RESULTS AND DISCUSSION .. ... .. .. ...................... .. ..... . 16
Amphibian Population: .... ... ... .... ... ... ... ............... ...... 16
1. Moist Soil Unit. .... .. ..... ... ... .. . .. .... ................ 16
2. Fallowed Rice Fields ........................... .. ..... .. .. 19
3. Rice Fields .................. .......................... .. 21
In-Situ Bioassay: ................................... ....... ....... 23
1. Starn M-4 ................................. .. ..... .. ..... 23
2. Grazon P+D .. .................. ............... ..... . ... . 24
3. Arrosolo .. ... ... ... ... .... ... ... ... ... .................. 25
8. MANAGEMENT IMPLICATIONS . .... .... ... ... .................... . 29
9. ACKNOWLEDGMENTS. . ....................... ... .. ... .. ....... .. 30
10. LITERATURE CITED . .... ........................... ... .. . ... ... .. 31
I l. Appendix A: Common and scientific names of plants identified on the
Anahuac National Wildlife Refuge. . . ....................... 37
12. Appendix B: Common and scientific names of non-amphibian animals seen
on the Anahuac National Wildlife Refuge . . .... .. ..... ........ 39
13. Appendix C: Survey ofteratogenic malformations from Arrosolo exposed
embryos .................................... ..... .. .... 41
LIST OF TABLES
Table Page
1. List of amphibians likely to be present on or near the Anahuac National Wildlife
Refuge .............................................................. 2
2. Pesticides, herbicides or fungicides currently approved for use on the Anahuac
National Wildlife Refuge ................................................ 4
3. Amphibian populations recorded for the moist soil unit on the East Bay Bayou Tract
of the Anahuac National Wildlife Refuge. ................................. 17
4. Amphibian populations recorded in fallowed rice fields on the Anahuac National
Wildlife Refuge. . .................................................... 20
5. Amphibian populations recorded in rice fields on the Anahuac National Wildlife
Refuge ............................................................. 22
11
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LIST OF FIGURES
Page
Figure 1. Anahuac National Wildlife Refuge, Chambers County, Texas. ............ 8
Figure 2. Rice farming area, Anahuac National Wildlife Refuge. . ................. 9
Figure 3. Dose response curve for Grazon P+D to Xenopus laevis embryos. . ....... 24
Figure 4. Dose response curve for Arrosolo to Xenopus laevis embryos. . .......... 26
lll
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1
INTRODUCTION
Scientists have expressed concerns about possible effects of pesticides on
amphibians for at least three decades (Cooke 1972), and on the decline of many
amphibian populations (Thornton 1977, Crump 1994). Reports of deformed frogs
observed in large numbers in the mid-northern region of the United States have recently
emerged in the literature (Ouellet et al. 1997, Casper 2000). In many areas these
amphibian population declines have been linked to habitat alterations, such as wetland
draining and agricultural expansion (Thornton 1977) and introduction of exotic predatory
fish or other frog species in rivers and streams (Hayes and Jennings 1986). Recent
literature by Gardiner and Hoppe (1999) and Kaiser et al. (2000) focused on the exposure
of amphibians to industrial chemicals and pesticides as being an important limiting factor
affecting amphibian reproduction and development.
A recent capture of a five-legged northern spring peeper (Hyla crucifer) on the
Trinity River National Wildlife Refuge in Liberty County, Texas (Stuart Marcus, Refuge
Manager, personal communication, 1998) elevated the concern about possible impacts on
amphibian populations that may be exposed to anthropogenic pollution on national
wildlife refuges. The Anahuac National Wildlife Refuge (ANWR) is about 70 miles
south of the area where the five-legged frog was collected and permits rice farming each
year on the refuge. Rice farming occurs on about 600 acres of the approximately 34,000
acre refuge each year and requires the periodic use of some herbicides and pesticides.
There are at least 16 amphibian species recorded in Chambers County, Texas
(Table 1), with 10 additional species reported in the surrounding counties of Liberty
2
Table 1. List of amphibians likely to be present on or near the Anahuac National
Wildlife Refuge.
Common Name Scientific Name1
* Western Lesser Siren Siren intermedia nettingi
* Marbled Salamander Ambystoma opacum
# Smallmouth Salamander Ambystoma texanum
* Three-toed Amphiuma Amphiuma tridactylum
* Southern Dusky Salamander Desmognathus auriculatus
# Central Newt Notophthalmus viridescens
*
Dwarf Salamander Eurycea quadridigitata
# Coastal Cricket Frog Acris crepitans paludicola
# Bullfrog Rana catesbeiana
# Bronze Frog Rana clamitans clamitans
# Southern Leopard Frog Rana sphenocephala
# Southern Crawfish Frog Rana areolata areolata
*
Pickerel Frog Rana palustris
*
Pig Frog Ranagrylio
* Northern Spring Peeper Hyla crucifer crucifer
# Gray Treefrog Hyla versicolor
# Green Treefrog Hyla cinerea
# Squirrel Treefrog Hyla squirella
*
Strecker's Chorus Frog Pseudacris streckeri
# Upland Chorus Frog Pseudacris triseriata
# Hurter's Spadefoot Scaphiopus holbrooki hurteri
# Gulf Coast Toad Bufo valliceps valliceps
# East Texas Toad Bufo woodhousei velatus
*
Dwarf American Toad Bufo americanus charlesmithi
# Eastern Narrow mouth Toad Gastrophryne carolinensis
# Plains Narrow mouth Toad Gastrophryne olivacea
1 Scientific names from Dixon ( 1987)
*
Recorded in surrounding counties but not Chambers County.
# Recorded in Chambers County as well as in surrounding counties.
3
and Jefferson (Dixon 1987) . At the present time, there is no know monitoring of
amphibian or other vertebrate species on the refuge or the surrounding counties for their
presence, abundance or potential impact from exposure to agricultural chemicals.
A contaminant survey of the ANWR (Cain 1993) reported minor contamination
due to heavy metals and organochlorine chemicals in some samples of sediment, fish and
aquatic invertebrates. No residues of herbicide or fungicide used in rice farming and for
the control of invasive Chinese tallow trees, on the ANWR, were included in that study.
Chemicals that were approved for use in the farming and tallow tree control program
during this study are listed in Table 2. Several of these herbicides listed in Table 2 are
chlorinated compounds (i.e. organochlorines) and may be more persistent in the
environment than expected, their breakdown products may be persistent or show
toxicological effects not reported, or these compounds may cause subtle adverse
ecological effects to some species.
Propanil, for example, is used worldwide in the cultivation of rice and has been
reported by Hill et al. (1981) and Di Muccio et al. (1984) to be contaminated with two
chlorinated compounds, tetrachloroazobenzene (TCAB) and tetrachloroazoxybenzene
(TCAOB). Pothuluri et al. (1991) indicates these compounds are structural analogs of a
metabolizing enzyme inducer, tetrachlorodibenzo-p-dioxin (TCDD). Both TCAB and
TCAOB have been reported to be embryolethal, teratogenic and perhaps genotoxic
(Poland and Kende 1977, Hsia 1981, D'Argy et al. 1984) . It has also been reported that
propanil is converted by microbial activity in soil to TCAB and other azo products
(Pothuluri et al. 1991 ).
4
Table 2. Pesticides, herbicides or fungicides currently approved for use on the
Anahuac National Wildlife Refuge.
Trade Name Formulation
Bolero 8EC Thiobencarb 84%
Basagram Sodium Salt of Bentazon 42%
Garlon * Triclopyr
Facet 50 WP * 3, 7- dichloro-8-quinolinecarboxylic
acid 50%
Starn M-4 * 3',4'-Dichloropropionilide 43.5%
Arrosolo * Propanil33.1% and Ordram
(molinate) 33.1%
Rodeo Isopropy lamine salt of Glyphosate
2,4-D Amine Weedar 64 * Dimethylamide Salt of2,4-Di
chlorophenoxyacetic acid 46%
Sevin XLR Plus !-Naphthyl N-Methyl Carbamate
41%
Grazon P+D * Picloram:4 amino-3,5,6-trichloro
picolinic acid as the triiso
propanolamine salt 10 .2%; 2,4-
dichlorophenoxyacetic acid, as
The triisopropanolamine salt 39.6%
Roundup Glyphosate
* Organochlorine pesticides