P1.22 Wednesday, Jan. 4 Tadpole responses to combined environmental stressors – pesticides and salinity WOOD, B.E.*; WELCH, A.M.; College of Charleston, SC; College of Charleston, SC email@example.com
Habitats are becoming increasingly degraded due to human activities, often experiencing multiple stressors simultaneously. Many freshwater habitats are compromised by pollution from various sources, including pesticides from agricultural, residential and urban runoff. In addition, increasing salinity is an emerging threat to freshwater habitats, due to runoff of road salts, salinization of inland habitats and saltwater intrusion into coastal freshwater sources, particularly as sea levels rise. Although stressors are often studied in isolation, assessing their combined effects is crucial to understanding how populations respond to human-altered habitats. We investigated the effects of pesticides and salinity, alone and in combination, on growth and development of southern toad tadpoles (Anaxyrus terrestris). Tadpoles were exposed to eight treatments, consisting of three commonly-used pesticides – carbaryl, glyphosate, and atrazine – and a no-pesticide control, with and without elevated salinity. Tadpoles exposed to increased salinity were smaller and less active and ultimately metamorphosed later and at a smaller size. Among the pesticides investigated, carbaryl was particularly harmful, decreasing survival, reducing growth and activity, and leading to delayed metamorphosis. When experienced together, carbaryl and salinity showed a synergistic effect on tadpole growth, with much more pronounced growth suppression than with either stressor experienced alone. Thus, tadpoles are more vulnerable when the two stressors are experienced together, and in some cases the combined effect is greater than predicted by the sum of their individual effects. Ultimately, both pesticides and increasing salinity put amphibian populations at risk, and populations that experience both impacts simultaneously are at particular risk.