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You Better Repeat It: Complex CO<sub>2</sub> × Temperature Effects in Atlantic Silverside Offspring Revealed by Serial Experimentation

Murray, Christopher S., Baumann, Hannes
Diversity 2018 v.10 no.3
Menidia menidia, acidification, developmental stages, forage fish, larval development, ocean acidification, ocean warming, progeny, rearing, temperature
Concurrent ocean warming and acidification demand experimental approaches that assess biological sensitivities to combined effects of these potential stressors. Here, we summarize five CO<inf>2</inf> &times; temperature experiments on wild Atlantic silverside, Menidia menidia, offspring that were reared under factorial combinations of CO<inf>2</inf> (nominal: 400, 2200, 4000, and 6000 &micro;atm) and temperature (17, 20, 24, and 28 &deg;C) to quantify the temperature-dependence of CO<inf>2</inf> effects in early life growth and survival. Across experiments and temperature treatments, we found few significant CO<inf>2</inf> effects on response traits. Survival effects were limited to a single experiment, where elevated CO<inf>2</inf> exposure reduced embryo survival at 17 and 24 &deg;C. Hatch length displayed CO<inf>2</inf> &times; temperature interactions due largely to reduced hatch size at 24 &deg;C in one experiment but increased length at 28 &deg;C in another. We found no overall influence of CO<inf>2</inf> on larval growth or survival to 9, 10, 15 and 13&ndash;22 days post-hatch, at 28, 24, 20, and 17 &deg;C, respectively. Importantly, exposure to cooler (17 &deg;C) and warmer (28 &deg;C) than optimal rearing temperatures (24 &deg;C) in this species did not appear to increase CO<inf>2</inf> sensitivity. Repeated experimentation documented substantial inter- and intra-experiment variability, highlighting the need for experimental replication to more robustly constrain inherently variable responses. Taken together, these results demonstrate that the early life stages of this ecologically important forage fish appear largely tolerate to even extreme levels of CO<inf>2</inf> across a broad thermal regime.