The Relation Among Essential Habitat, Ocean Acidification, and Calcification on the Nantucket Bay Scallop (Argopecten irradians)

The relation among essential habitat, ocean acidification, and calcification in Argopecten irradians (Lamarck 1819) was examined through field and laboratory research. Three major questions were addressed: (1) What habitat conditions are associated with abundant populations of bay scallops in Nantucket Harbor? (2) How might future predictions of ocean pH decline affect the biomineralization of shell by bay scallop across juvenile and adult life stages? (3) Are there biochemical indicators that can inform our understanding on how the bay scallop may cope with ocean acidifying events? Elemental fingerprinting of adult and juvenile Nantucket bay scallop shells, A. irradians, revealed distinct element/Ca ratios that can be used to distinguish source habitat of bay scallops in Nantucket Harbor. These ratios were associated with proximity to the harbor mouth with elemental differences attributed to variation in salinity and pH. This study identified boundary salinity and pH conditions that support large abundances of A. irradians within Nantucket Harbor. Impacts of ocean acidification on calcification in both juvenile and adult life stages of bay scallop were examined, specifically, the relation between life stage and net calcification rate across varying levels of pCO 2-induced low pH. Net calcification, estimated by buoyant weight, was lower in adults compared to juveniles raised under the same conditions (e.g. pH = 7.2, Net Calcificationadult = −0.1444, Net Calcification juvenile = −0.0752). The overall impacts across life stages suggest that juvenile bay scallops, as compared to adults, may budget more energy toward calcification of shell. Stress induced by energy demands for shell loss under ocean acidification events was hypothesized to cause an increase in plasma taurine/glycine ratios. High performance liquid chromatography (HPLC) with fluorescence detection was used to measure the abundance of taurine and glycine in plasma (pre-and post-treatment) and the ratio of taurine/glycine was used as an indicator of environmental stress induced by high CO2-induced reduction in pH. A nested general linear model revealed that the taurine/glycine ratio in plasma may be used in future studies as an indicator of pH induced stress for A. irradians.