9.5 Friday, Jan. 4 Multiple stressor interactions delay horseshoe crab embryo development VASQUEZ, M.C.*; MURILLO, A.; BROCKMANN, H.J.; JULIAN, D.; University of Florida, Gainesville, FL firstname.lastname@example.org
Fertilized eggs of the American horseshoe crab, Limulus polyphemus, are buried in shallow nests above the high tide line, where they are exposed to variations in abiotic conditions during early development. We examined whether the rate of embryonic development is affected by exposure to environmentally-relevant combinations of three factors: temperature (T; 25°, 30° and 35° C), salinity (S; 5, 15 and 34 ppt), and dissolved O2 (DO; 5%, 13% and 21% O2). Newly fertilized eggs collected from nests of individual mating pairs were returned to the lab and incubated under fully-factorial stressor combinations for 14 d, then placed in “control” conditions (30° C, 34 ppt, 21% O2) for an additional 14 d. Growth rate was measured every 2 d throughout the experiment. We assessed 8 embryos from each of 6 mating pairs at each of the 27 treatment combinations (1296 eggs). We found that although the effect of isolated stressors (high T, low S or low DO) on development was minimal, stressor combinations showed stronger effects with evidence of complex interactions. For example, whereas high T and low S in isolation each had no effect, they were lethal in combination, and although low T in isolation slightly decreased the rate of development, it reduced the negative effects of low S and/or low DO. Furthermore, low DO increased the effect of high T, but it did not affect the response to low S. Low DO also appeared to pause development, which then resumed upon return to control conditions, but only after a 4 d lag. These data demonstrate that complex, synergistic interactions among environmentally-relevant levels of abiotic stressors can substantially alter the development of a coastal invertebrate in ways that may not be predicted from the effects of the stressors in isolation.