DENISE M. ROTHBALDWIN-WALLACE COLLEGE

DEPARTMENT OF BIOLOGYMAY 1 , 2009

The Effects of Road Salt (NaCl) on the Survivorship of Two Vernal

Pool-Breeding Amphibians:

The Wood Frog (Rana sylvatica) and Spotted Salamander (Ambystoma

maculatum)

“Why should we care if they all die? They are gross anyway!”

-BW student

Well… Good Question

http://www.fishingfury.com/wp-content/uploads/2008/05/record-halibut.jpg

Algae

http://www.waterencyclopedia.com/images/wsci_01_img0017.jpg

http://doctorswithoutborders.org/images/news/malaria/malaria_header_550x367.jpg

So… What is going on?

E.O. Wilson says:

Habitat destructionInvasive speciesPopulationPollutionOver-harvesting

http://farm1.static.flickr.com/123/330811704_282ee8a597.jpg

What is a Vernal Pool??

Temporary Form from melting

snow and spring rains Dry mid to late

summer Unpredictable

Naturally occurring Shallow (4ft > deep) Impermeable

substrate on bottom

Free of predatory fish

http://www.fs.fed.us/ne/amherst/images/vernalpool.jpg

Vernal Pool (cont.)

Contain one or more of four indicator species

Blue-spotted Salamanders (Ambystoma laterale) Fairy Shrimp (Anostraca) Wood Frog (Rana sylvatica) Spotted Salamander (Ambystoma maculatum)

http://www.umaine.edu/wetlands/VPecology.htm

Wood Frog (Rana

sylvatica)

http://www.nae.usace.army.mil/recreati/uvd/UVD_amphibians/uvdwoodfrog.html

http://wpcontent.answers.com/wikipedia/commons/7/7f/Rana-sylvatica_Range.gif

Wood Frog: Reproduction

Breed mostly in vernal pools

Migration in early spring

500-3,000 Eggs

• Communal nesting

Metamorphose 6-15 weeks

• Terrestrial adults

Spotted Salamander (Ambystoma maculatum)

http://www.vernalpool.org/images/21_ys_a.jpg

http://www.grizzlyrun.com/Files/Images/Image_Gallery/spotted_salamander_Range.gif

Spotted Salamander: Reproduction

Breed only in vernal pools

• Usually same pool every year

Mass migration to ponds

50-250 Eggs• Hatch in 20-60 days

• Aquatic larvae

Metamorphose late summer

• Terrestrial adults

Egg Masses

http://www.vernalpool.org/images/115-js-ys-wf.jpg

Salts as De-Icing Agents

Lower freezing point of water! melts at lower

temperatures

Cheap ~$30/ton

Effective Above ~ 15˚F

NaCl most common 5 million tons/yr in

Canada 10-15 million tons/yr

in US (Environment Canada

Website)

DOMENICO SANZO, STEPHEN J. HECNAR 2003

ENVIRONMENTAL POLLUTION

Effects of road de-icing salt (NaCl) on larval wood frogs

(Rana sylvatica)

Objective

Determine the effect of road salts, if any, on amphibians at environmentally relevant field concentrations

Hypothesis: Road salts have a negative effect on

amphibians.

Study Location

Thunder Bay, Canada

Lakehead University Environmental Laboratories

http://www.lib.utexas.edu/maps/united_states/united_states_wall_2002_us.jpg

Field Concentrations

Water analysis of 59 wetlands2 water samples from opposite ends of eachAnalyzed in university lab

Expected to see: Salt concentrations negatively correlated with

increasing distance of a wetland from the nearest road

Negative correlation between salt concentrations and species richness

Results: Field Concentration

Range in NaCl from 0.39 to 1030.00 mg/l Seawater ~ 3.5% NaCl ( 19,400 mg/l)

NaCl decreased with increasing distance from nearest road

Species richness negatively correlated with NaCl and

positively correlated with increasing distance to nearest road

Materials and Methods:Acute Toxicity

Dilution series of NaCl (0.00-9750mg/L)

Added 10 presorted tadpoles to each

Experiment time 96 hours

Methods cont.

Fed boiled lettuce

Checked jars for mortality every 24 hrs Dead tadpoles removed and weighed

Death defined: “… no response to continued prodding with a glass rod.”

Results: Acute Toxicity

Results: Acute Toxicity (cont.)

Methods:Chronic Toxicity

90 days

• 3 NaCl Concentrations• 0.39 mg/L• 77.50 mg/L• 1030 mg/L

16 tanks (4 replicates per treatment):

30 tadpoles to each tank

Methods (cont.)

Fed boiled lettuce

• Recorded behavioral and physical abnormalities• Counted at 10 day intervals

Checked daily

Results: Chronic Toxicity

Mean time to Morph vs. Chronic Treatment concentrations

Discussion

Roads are source of

contamination

Road salts are toxic

Causes premature

metamorphosis

Physiological effects

Conclusions

Road salts have a negative impact

Chloride in roadside pools much higher than woodlands

Supports hypothesis

Species richness negatively correlated with NaCl concentrations

Fewer tadpoles metamorphose with higher concentrations

Does this relate to other amphibians? and is the evidence

conclusive?

SARA J. COLLINS, RONALD W. RUSSELL 2006

ENVIRONMENTAL POLLUTION

Toxicity of road salt to Nova Scotia amphibians

Objective

“…examine how chloride concentrations in ponds, due to application of road salt, influence amphibian community structure and richness in roadside wetlands of Nova Scotia.”

Hypothesis: Elevated Chloride concentrations affect amphibian

populations

Nova Scotia

April-Sept. 2006

26 ponds

http://www.lib.utexas.edu/maps/united_states/united_states_wall_2002_us.jpg

Field Methods

Pond selection

• 26 within 60m of roads and highways

April- July

• Auditory surveys• Visual surveys • Species samples collected by dip net or by hand

May-September

Water samples collected for lab analysis

Chloride Concentrations

Results: Species Richness

Methods:Acute Toxicity

Larvae of 5 amphibian species: Spotted Salamander Spring Peeper Wood Frog Green Frog American Toad

10 Concentr

ations

Dechlorinated H2O

NaCl

Methods (cont.)

Experiment 96 hrs.

• Spotted Salamander 4 larvae per treatment

24 tadpoles per concentration

Observed daily for physical and behavioral abnormalities

• Dead removed• Distressed animals euthanized

• Body weight recorded

Species Abundance vs. Chloride Concentrations

Results: Acute Toxicity Tests

Conclusions

Spotted Salamanders and Wood Frogs were most sensitive to NaCl

Road salt concentrations affected community structure Sensitive species were absent from high chloride

concentrated ponds

Acute toxicity results supported field observations Behavioral changes could result in reduction of

species fitness

Interpretation

Exposure to road salts can affect amphibian community structure and species richness by excluding salt-sensitive species from high chloride environments

Overall Conclusions

At environmentally realistic concentrations, road salt caused physiological issues and decreased survivorship in amphibians.

Acute toxicity results of both studies showed high rates of mortality

Chronic exposure caused physiological differences

This is not new information!

In 1859 Charles Darwin noted that “nearly all amphibians and their spawn were killed by sea water”

(Origin of Species)

http://kornorstone.com/db3/00225/kornorstone.com/_uimages/BubbleBoy1.jpg

Alternatives

Potassium Acetate -76˚F $700-800/ton Less toxic; less corrosive; can cause %50 solution irritation if inhaled

Future Studies

Why do higher salt concentrations cause tadpoles to metamorphose faster?

Why was there a spike in survival from 7500-9000 mg/l?

Possible mutagenic effects of developing tadpoles

Effects of other road salts on these two species

Reasons for salt tolerance seen in the American Toad

Long term effects on community structure

How chemical runoff affects people

“We now face an extinction episode

on this planet comparable to that which marked the end

of the dinosaurs about 65 million years ago”

(Planet Earth Episode 1)

Thank You!!BW Faculty:

Dr. Bumbulis

Dr. Barratt

Dr. Stanton

Family:

Grandma Jojo

Parents

Friends… all of you!

Questions?

Function of Chloride

Chloride: membrane function and water absorptionIn the body reacts with potassiumHelps maintain osmotic equilibrium by creating

concentration gradientthrough ATP either goes in to the cell or leaves

the cell ~ based on solute concentration in the water vs. solute in the cell

Moves from high to low concentrationsHelps maintain pHKidney function: co-transport proteins

Na+, K+, Cl -