Hello everyone!
To continue on from my Acid Mine Drainage series, I would like to discuss more on acid deposition and its effects on animals.
During our lectures, we have talked about acidification through wet or dry deposition affecting soil and water ecosystems. In the most recent lecture on Soil Pollution, the addition of ammonia and ammonium as fertilizer was also discussed to caused soil acidification. We have talked mostly about how heavy metals in the soil becomes bioavailable to plants interfering with plants’ Cation Exchange Capacity. We have also briefly touched on heavy metals accumulating in fishes as a result and possible effects on nudibranch.
With the rapid increase of industrialization and the burning of fossil fuels, releases of nitrogen oxides and sulfur into the atmosphere increased drastically. Acid deposition has been alleviated to some extent in Europe, Canada, and the United States with the introduction of clean air legislation. However, it still remains a pressing issue in other areas like China and India, with rapid industrialization, that relies mainly on coal for power yet with poor pollution control. In this post, I will be focusing on the effects of acid deposition on amphibians as there are reasons to believe they will be adversely affected.
Many amphibians make use of ephemeral aquatic habitats, which are dry periodically and refill with fresh precipitation. Some examples of these habitats are included in the diagram below (Heim et al., 2019).These ponds are typically small in size and have limited contact with the soil and other buffering systems with low calcium and alkalinity (Freda et al., 1991). For these reasons, amphibian habitats are very vulnerable to precipitation chemistry.
As with humans, susceptibility is variable between species. Some species, such as Carpenter frog and Pine Barrens tree frog, breed in acidic water of pH < 4.0. However, most species require water that is less acidic and their eggs and larvae suffer more than 50% mortality in water with pH 4.5. Acidic water disrupts the ionic balance within the cells and typically killing embryos by late gastrula stage (Vitt & Caldwell, 2009). Less acidic water may allow more than 50% survivorship but still affect development. These tadpoles become less vigorous, feed less often causing weight loss and decreased growth rates (Farquharson et al., 2016). Producing a high percentage of development abnormalities such as crooked tails, many resulting in death during metamorphosis.
If acid levels are not lethal, community structure can shift as a result. For example, the glacial soils of central New York are poorly mineralized and are downwind from the heavy industry thus all freshwater communities are acidified. This affected 2 salamanders species of vernal pool the Jefferson Salamander (Ambystoma jeffersonianum) and Spotted salamander (Ambystoma maculatum). Jefferson Salamander is an acid-tolerant species whose larvae can survive in water with pH<4.0 while the Spotted salamander requires water with pH≥5.0. The snowmelt and spring rainfall produces the breeding pool of pH 4.5 allowing Jefferson Salamander to reproduce and slowly outnumber the formerly dominant Spotted Salamander (Vitt & Caldwell, 2009).
Jefferson Salamander (Ambystoma jeffersonianum) (Virginia Herpetological Society, 2020) 
Spotted salamander (Ambystoma maculatum) (Pippen, 2008)
As I have mentioned, most of these breeding ponds are dry prior to rain or snowmelt. These precipitation not only bring their acid load but also runoff from surroundings causing pH to drop below even the tolerance levels of most species. The toxic effect of acid rain is therefore the greatest on species that breed in these ponds as there are no buffer present to dilute or neutralize the acid.
That brings me to the end of this post!
See you guys soon!
References
Farquharson, C., Wepener, V., & Smit, N. J. (2016). Acute and chronic effects of acidic pH on four subtropical frog species. Water SA, 42(1), 52. doi:10.4314/wsa.v42i1.07
Freda, J., Sadinski, W.J. and Dunson, W.A. (1991) Long term monitoring of amphibian populations with respect to the effects of acidic deposition. Water Air Soil Pollut. 55, 445-62.
Heim, K. C., Mcmahon, T. E., Calle, L., Wipfli, M. S., & Falke, J. A. (2019). A general model of temporary aquatic habitat use: Water phenology as a life history filter. Fish and Fisheries. doi:10.1111/faf.12386
Pippen, J. (2008). Spotted Salamander (Ambystoma maculatum). Retrieved October 09, 2020, from https://www.jeffpippen.com/herps/spottedsalamander.htm
Virginia Herpetological Society. (2020). Jefferson Salamander. Retrieved October 09, 2020, from https://www.virginiaherpetologicalsociety.com/amphibians/salamanders/jefferson-salamander/jefferson_salamander.php
Vitt, L. J., & Caldwell, J. P. (2009). Conservation Biology. Herpetology, 379-409. doi:10.1016/b978-0-12-374346-6.00014-6
