In situ effects of pesticides on amphibians in the Sierra Nevada

Abstract

For more than 20 years, conservationists have agreed that amphibian populations around the world are declining. Results obtained through laboratory or mesocosm studies and measurement of contaminant concentrations in areas experiencing declines have supported a role of contaminants in these declines. The current study examines the effects of contaminant exposure to amphibians in situ in areas actually experiencing declines. Early larval Pseudacris regilla were translocated among Lassen Volcanic, Yosemite and Sequoia National Parks, California, USA and caged in wetlands in 2001 and 2002 until metamorphosis. Twenty contaminants were identified in tadpoles with an average of 1.3-5.9 (maximum = 10) contaminants per animal. Sequoia National Park, which had the greatest variety and concentrations of contaminants in 2001, also had tadpoles that experienced the greatest mortality, slowest developmental rates and lowest cholinesterase activities. Yosemite and Sequoia tadpoles and metamorphs had greater genotoxicity than those in Lassen during 2001, as determined by flow cytometry. In 2001 tadpoles at Yosemite had a significantly higher rate of malformations, characterized as hemimelia (shortened femurs), than those at the other two parks but no significant differences were observed in 2002. Fewer differences in contaminant types and concentrations existed among parks during 2002 compared to 2001. In 2002 Sequoia tadpoles had higher mortality and slower developmental rates but there was no difference among parks in cholinesterase activities. Although concentrations of most contaminants were below known lethal concentrations, simultaneous exposure to multiple chemicals and other stressors may have resulted in lethal and sublethal effects.

Effects of metal and predator stressors in larval southern toads (Anaxyrus terrestris)

“…A single-factor approach in an artificial environment, combined with the use of model organisms as surrogates for entire taxa, does not account for many ecological processes that ultimately affect exposure outcomes under field conditions (Boone and James 2005). But this gap between laboratory and field conditions can be bridged, using outdoor mesocosms (Relyea 2006) and in situ studies in known contaminated field sites (Sparling et al 2015). Utilizing outdoor mesocosms effectively increases realism while retaining control of the factors being tested (Boone and James 2005).…”

Organic contaminants in western pond turtles in remote habitat in California

“…This continued agricultural growth can be partly attributed to pesticides, which are used prominently in the state for pest management. The problems associated with heavy pesticide use are well documented, and in some California National Parks, pesticides are found ubiquitously across diverse biological and physical endpoints (LeNoir et al, 1999;Landers et al, 2008;Flanagan Pritz et al, 2014;Sparling et al, 2015).…”

Assessing the links among environmental contaminants, endocrinology, and parasites to understand amphibian declines in montane regions of Costa Rica

“…Amphibians are declining on a global scale and at an unprecedented rate [ 1 – 7 ]. An especially puzzling aspect of this phenomenon involves declines of populations in remote, protected areas [ 1 ].…”