Decreased pH and increased temperatures affect young-of-the-year red king crab (Paralithodes camtschaticus)

Abstract

The red king crab (Paralithodes camtschaticus) is a high-latitude commercially important species with a complex life-history cycle which encompasses a wide variety of conditions and habitats. High-latitude waters, including those around Alaska where red king crab live, are predicted to have increased ocean acidification and temperatures in comparison to other areas. The interaction of ocean acidification and increased temperature has not been examined for any life history stage of red king crab. To determine the effects of near-future ocean acidification and warming temperature on young-of-the-year red king crab survival, growth, and morphology, we conducted a long-term (184 d) fully crossed experiment with two pHs and three temperatures: ambient pH (∼7.99), pH 7.8, ambient temperature, ambient +2 °C, and ambient +4 °C, for a total of six treatments. Mortality increased with exposure to reduced pH and higher temperatures, but a clear trend in the interactive effects of the stressors was not observed. A synergetic effect on mortality was observed in the pH 7.8 and ambient +4 °C temperature treatment. This treatment also had the lowest survival with only 3% surviving to the end of the experiment. However, an antagonistic effect on mortality was observed in the pH 7.8 and ambient +2 °C treatment. Lower pH and warmer temperatures affected intermoult duration, only temperature affected percent increase in size, but carapace length was not affected. Decreased pH and increased temperature had no effect on morphology. The results of this study combined with other studies show that decreased pH and warming has profound negative effects on red king crab. Unless the species is able to adapt or acclimate to changing climate conditions, red king crabs populations may decrease in the upcoming decades due to ocean acidification and rising temperatures.