Frogs Australia Network

Frogs in an Effluent Society
© WWF Australia

Why are frogs good indicators of environmental pollution?

Frogs are good indictors of environmental pollution because of their unique physiology. The semi-permeable skin of adult frogs and the gills tadpoles use to breathe are both characteristics that make these animals very susceptible to contaminants. This is because chemicals easily penetrate these exposed areas.

Frogs are also more likely to come into contact with chemicals as they inhabit both aquatic and terrestrial environments.

Download 'Frogs in an Effluent Society' PDF

Broomhall, S. Frogs in an Effluent Society: Risks, Remedies and Responsibilities. WWF-Australia, 2004. 2.12MB PDF

What do we know about the effects of pollutants on frogs?

Not much scientific work has been done to test the effects various pollutants have on frog eggs, tadpoles and adult frogs. This means in many cases we simply do not know how sensitive many species of frogs are to environmental contaminants.

Our knowledge of the pollutants that are in Australian ecosystems is also very limited. Further research needs to be done to investigate whether chemicals combine or breakdown in our waterways to form new toxins.

Where does pollution come from?

Almost all pollutants are created by humans as a direct result or as a by-product of a production process. Everyone produces pollution because the products we use either generate pollution when they are manufactured or become a pollutant when we are finished with them.

Household pollution

Many of the things we use around our own homes pollute the environment. Potential sources of pollution from cities and towns include:

pesticides and fertilizers such as insect repellents, cockroach baits, rat and mice poisons, mold and mildew killers, weed killers, and swimming pool chemicals.
everything we put down our drains and toilets including oils, paint strippers, food scraps and small items of rubbish.
all the rubbish we leave in the streets such as cigarette butts.
rubbish tips which can pollute groundwater.

Industrial and agricultural pollution

A lot of primary and secondary producers make and use significant amounts of pollutants. Potential sources of pollution form these groups are:

the use of pesticides and herbicides by farmers and local councils.
huge amounts of fertilizers used by farmers.
agricultural dip sites (where cattle have chemicals put on them for ticks etc.).
old metal smelting sites, gas plants and power stations that are not managed responsibly.

Chemicals and their known effects on frogs

Current research suggests that lots of chemicals are harmful to frogs but in many cases more studies need to be done. The main contaminants in Australian environments are:

Pesticides

There are thousands of pesticide products registered for use in Australia. These chemicals become more dangerous to frogs when they move from the area they were intended, as they breakdown and accumulate in other habitats. Pesticides include products such as:

Organochlorines: these do not breakdown easily and remain in an environment for a long time. The Organochlorine, Endosulfan is still being used in Australia. The Organochlorine DDT which has not been used in Australia for the last 20 years has been found in low concentrations in one frog species and has had harmful effects.
Herbicides and fungicides: have been found to contaminate many groundwater samples in Australia. These products have been known to reduce testosterone levels and cause embryo malformations in the African Clawed Frog.
Carbamates: are known to produce deformed skeletal and musculature tissue in some frogs. These chemical have also been reported to cause tadpole deaths in some species and change the swimming behaviour in others. It should also be noted that the toxicity of carbamates increase in the presence of UV-B radiation.

Surfactants

These are used in many products to break down the surface tension of water and help other compounds disperse. Surfactants have been found to have toxic effects on the embryos and tadpoles of the African Clawed Frog.

Fertilisers

Phosphates and nitrates are the main components of fertilisers. Australian frogs have evolved in an environment that is relatively low in nitrates and phosphates, thus it is likely that they will be very sensitive to these chemicals.

Fertilisers also contain traces of heavy metals such as lead, cadmium and mercury. Heavy metals have been proven to be very harmful to frogs, mercury being one of the most toxic elements to frogs yet found.

Reference

Broomhall, S. Frogs in an Effluent Society: Risks, Remedies and Responsibilities. WWF-Australia, 2004

For further information visit:

Pollution - New South Wales National Parks and Wildlife Service
http://www.nationalparks.nsw.gov.au/npws.nsf/Content/Pollution

Water Watch Australia
http://www.waterwatch.org.au/

The National Water Quality Management Strategy - Department of Environment and Heritage
http://www.deh.gov.au/water/quality/nwqms/index.html

Australian Pesticides and Veterinary Medicines Authority
http://www.apvma.gov.au/

Pollution