Elevated temperature elicits greater effects than decreased pH on the development, feeding and metabolism of northern shrimp (Pandalus borealis) larvae

Climate models predict that the average temperature in the North Sea could increase 3–5C and surface-waters pH could decrease 0.3–0.5 pH units by the end of this century. Consequently, we investigated the combined effect of decreased pH (control pH 8.1, decreased pH 7.6) and temperature (control 6.7C, elevated 9.5C) on the hatching timing and success, and the zoeal development, survival, feeding, respiration and growth (up to stage IV zoea) of the northern shrimp, Pandalus borealis. At elevated temperature, embryos hatched 3 days earlier, but experienced 2–4 percent reduced survival. Larvae developed 9 days faster until stage IV zoea under elevated temperature and exhibited an increase in metabolic rates (ca 20 percent) and an increase in feeding rates (ca 15–20 percent). Decreased pH increased the development time, but only at the low temperature. We conclude that warming will likely exert a greater effect on shrimp larval development than ocean acidification manifesting itself as accelerated developmental rates with greater maintenance costs and decreased recruitment in terms of number and size.