Embryonic Survivorship of the Spotted Salamander (Ambystoma maculatum) in Roadside and Woodland Vernal Pools in Southeastern New Hampshire

-Roadside wetlands are often contaminated by highway runoff; however, little is known about the impact of pollution on the organisms that use these wetlands. Most amphibians use wetlands as breeding habitats and are therefore vulnerable to aquatic pollutants. In 1995 and 1996, I conducted transplant experiments to compare the embryonic survivorship of Ambystoma maculatum in temporary woodland pools to that in roadside pools. Chemical parameters were monitored to identify differences between roadside and woodland pool environments. Failure time analysis was used to compare embryonic survival probabilities for transplant experiments in both years. The results indicate that deicing salts heavily contaminate roadside vernal pools. Ambystoma maculatum survivorship was significantly lower in roadside pools for four of five transplants in 1995 and all transplants in 1996. Deicing salts used for highway maintenance contaminated roadside vernal pools, and are a possible factor in the reduced embryonic survival observed in these pools. al of Herpetol gy, Vol. 34, No. 1, pp. 607, 2000 right 20 Society for the Study of Amphibians d Reptil s ryonic Survivorship of the Spotted Salamander stoma maculatum) in Roadsi e and Woodland Vernal Pools in eastern New Hampshire Approximately one-half of the frog species and one-third of the salamander species in North America rely on ephemeral wetlands for embryonic and larval development (Pierce, 1985). Ephemeral (seasonal) wetlands include vernal pools, which dry annually, as well as semi-permanent ponds that dry more infrequently. In New Hampshire, Rana sylvatica (wood frog), Ambystoma maculatum (spotted salamander), Ambystoma laterale (blue spotted salamander), Ambystoma jeffersonianum (Jefferson's salamander) and hybrids of the latter two species depend on these unique wetlands for reproduction. Suitable breeding sites for these amphibians must dry often enough to exclude fish and must retain water long enough to allow amphibian larvae to complete development and metamorphose into terrestrial adults. The impact of pollution on the chemical, physical, and biological properties of vernal pools is not well understood. The chemical composition of the water in vernal pools reflects the chemical content of upper soil horizons, leaf litter, runoff from surrounding areas, and even atmospheric conditions (Rowe and Dunson, 1993). The watersheds of these pools tend to be small; thus, precipitation and runoff entering these pools have little contact with soil buffering systems. There is often little water volume in the pool to dilute polluted inflow (Pough, 1976; Gascon and Planas, 1986), resulting in a greater effect of pollutants on the water in these wetlands than in lakes and streams. In addition, evaporation during late spring and summer may increase the concentration of ions in the water causing chemical and physical stress for 60 This content downloaded from 157.55.39.203 on Sat, 27 Aug 2016 06:25:30 UTC All use subject to http://about.jstor.org/terms SURVIVORSHIP OF AMBYSTOMA MACULATUM EMBRYOS TABLE 1. Description of maximum length and depth of pools and transplant pairs. Transplant Pair (maximum length/maximum depth) Transplant A95 WI (41.3 m/1.4 m) vs. R1 (45 m/1.5 m) Reciprocal Transplant A95 R1 (45 m/1.5 m) vs. W1 (41.3 m/1.4 m) Transplant A96 W1 (41.3 m/1.4 m) vs. R1 (45 m/1.5 m) Transplant B95 W2 (39 m/1.7 m) vs. R2 (34.6 m/1.3 m) Transplant B96 W2 (39 m/1.7 m) vs. R2 (34.6 m/1.3 m) Transplant C95 W3 (29 m/0.87 m) vs. R3 (25 m/0.93) Transplant D95 W5 (15 m/2.1 m) vs. R5 (17.9 m/1.1) Transplant E96 W6 (26.7/1.2 m) vs. R3 (25 m/0.93 m) Transplant F96 W4 (21 m/1.6 m) vs. R5 (17.9/1.1) organisms living in these pools (Albers and Prouty, 1987). The semi-permeability of skin and eggs makes amphibians especially vulnerable to habitat contamination, particularly during embryonic and larval stages (Zug, 1993). Ambystoma salamanders may be at greater risk than other amphibians because they return to natal pools to breed (Shoop, 1968; Stenhouse, 1985). Few studies have investigated the impact of contaminated highway runoff on the animals that depend on these wetlands. Scientists have found elevated levels of lead, cadmium, nickel, zinc, and salts in adjacent highway habitat (Lagerwerrf and Specht, 1970). In New Hampshire a likely source of highway contamination is deicing salt. The New Hampshire Department of Transportation (NHDOT) relies heavily on deicing salt as a safety precaution for motorists in winter. For the past 25 years NHDOT has used an average of 16.75 tons*lanemile-~ of salt on the state's highways. In 1995, NHDOT used 13.90 tons*lanemile-1 and in 1996 they used 18.08 tons*lanemile-1 (R. Hogan, NHDOT, pers. comm.). Stormwater runoff transports the deicing salt to adjacent wetlands and the resulting high salt concentrations affect water chemistry and plant species diversity (Burbeck et al., 1971; Isabelle et al., 1987). The goal of this project was to quantify the impact of highway contamination on vernal pool water chemistry and on A. maculatum embryos. I tested the null hypothesis that A. maculatum embryonic survivorship in roadside pools was not significantly different than woodland pools. Transplant experiments were conducted in two years to detect possible effects of pool type on embryonic survivorship. Water chemistry variables were measured and compared between pool types to determine if they correlated with the outcomes of the transplant experiments. MATERIALS AND METHODS Site Description.-The study areas were located in southeastern New Hampshire in the towns of Durham, Lee, Epping, and Nottingham (Lat. 47?, Long. 71?). A total of six woodland and five roadside pools were use during the two year study (Table 1). Bre ding sites were identified in early spring by the presence of R. sylvatica egg masses, Am ystoma spermatophores, or other signs of amphibian breeding activity in the pools. All pools were less than 0.25 ha in early spring and all dried completely by August both years of this study. A pool was designated as 'woodland' if it was more than 50 m from a paved road and any human development and 'roadside' if it was within 2 m of a paved state highway. Pools were labeled "W" for woodland and "R" for roadside and then numbered in the order in which they were used. W1, W2, W3, Rl, R2, R3, and R5, were located in Nottingham, New Hampshire. W4 was located in Durham, New Hampshire and R4 was located in Epping, New Hampshire. W5 and W6 were located in Lee, New Hampshire. In all cases the surrounding forest was dominated by Quercus rubra, Acer rubrum, Acer saccharinum, Pinus strobus, and Tsuga canadensis. Vaccinium corymbosum and Ilex verticillata were the most common shrubs found in the pools. Transplant Experi ents.-Each roadside pool was paired wi h woodland pool based on similar lengths and water depths (Table 1). In both 1995 and 1996 ransplan experiments were conducted in four pairs of pools. One pair of pools in 1995 involved reciprocal transplants in which eggs were transplanted from woodland to roadside pools and also from roa side to woodland pools; all other experiments involved transplants from a woodland pool to a roadside pool, only. Transplants could only be conducted if pools contained more then 300 embryos. In 1995, pool Rl was the only roadside pool that contained enough A. maculatum egg masses to conduct a roadside to woodland transplant. In 1996 no roadside pool contained enough egg masses to conduct reciprocal transplant experiments. For each woodland to roadside transplant, A. maculatum egg masses were collected from the woodland pool and divided into sections, each 61 This content downloaded from 157.55.39.203 on Sat, 27 Aug 2016 06:25:30 UTC All use subject to http://about.jstor.org/terms