Abstract
Both the U.S. and Canadian sea scallop (Placopecten magellanicus) fisheries process scallops at sea and return shells to the water, yet the potential impact on regional carbonate dynamics has not been quantified. This study quantified the effects of discarded scallop shell deposits on the carbon cycle by determining short-term (41–42 days) shell dissolution rates across five environmentally relevant temperatures: 6°C, 8°C, 10°C, 12°C, and 14°C. Shells at 12°C and 14°C dissolved five times faster than those at 6°C, 8°C, and 10°C. The time required to dissolve 50% of the shell (shell half-lives) varied by temperature with mean (±SD) estimated rates of 35.5 ± 19.5 y (6°C), 23.0 ± 16.2 y (8°C), 39.0 ± 49 y (10°C), 19.6 ± 23.5 y (12°C), and 21.3 ± 22.8 y (14°C). In addition, relationships between shell weight and height were determined to assess potential changes in scallop morphology from sites in the Gulf of Maine sampled 40 y prior, with shell height increasing relative to weight. The dissolution of calcium carbonate from discarded scallop shells may contribute to buffering of ocean acidification impacts because of the associated increase in alkalinity, but additional research is needed to properly quantify the impact on oceanic carbon cycles.