physiology - Is the swimming pool water harmful to frogs who jump in? If so, how?

Here is an odd question:

Frogs have permeable skin. Indeed, via capillary action, frogs absorb water through their skin.

Chlorine is in principle a harmful substance. I am sure what percentage of chlorine is in swimming pools usually, but the pH level is kept to around 7.4. This is the desired pH level, as a pH of 7.4 is the pH-level in human eyes and mucous membranes.

One of the "common wisdoms" I had growing up was that if a leopard frog (i.e. The Northern Leopard Frog, rana pipiens) jumps into a swimming pool, it must die soon, because the chlorine would kill it. However, I now doubt this is true.

So, do frogs die from swimming pool water? If so, why? What exactly is killing them? Chlorine poisoning?

PS: I am having difficulty finding the correct tags for this question. Any help is appreciated.

Answer

The chlorine concentration in pools is +- 0,5 mg/L.

+

0.002 mg/L will fatally damage the sensitive skin on tadpoles, frogs, salamanders and other amphibians.

another source:

Free chlorine (Cl2) is a greenish gas that is well known for its highly toxic properties as can be attested to by the thousands of soldiers that died and were severely injured from chlorine exposure during World War I. In water, chlorine is the most toxic substance that we will discuss. Ironically for the amphibian keeper, it is this toxic nature of chlorine and its ability to denature proteins, which makes its encounter inevitable. Chlorine is generally used as an antibacterial agent in municipal water supplies and may be present in concentrations of over 9 mg/1 in some tap water (measured in Houston, Texas as an example, although levels were generally lower). The concentration of chlorine in municipal water supplies can vary greatly from day to day, or even hour to hour, depending on conditions at the water treatment facilities. Concentrations as low as 0.0034 mg/1 have been noted to reduce reproduction in fathead minnows with 72 hour LC100 (lethal concentration for 100% kill) at 0.15 mg/1 (Arthur and Eaton,1971). LC50 (96 hour) for the shiners (Notemigonus chrysoleucas) was as low as 0.19 mg/1 (Esvelt et al., 1971). The concentrations found in municipal water supplies are many times greater than the minimum lethal concentrations for many aquatic life forms.

Thus, the well being of the frog in the water of the swimming pool depends on the time the frog spends in the water. Eventually, with extended exposure the chlorine concentration will exceed the one compatible will life and the frog will die. This time is multifactorial variable, thus cannot be assessed easily - the weight and the skin surface area and skin permeability will affect the frog survival in a great degree.