Dataset: Ocean Acidification Experiment: Phenotypic responses of Eastern oyster

These data water quality readings for oysters exposed to ocean acidification at multiple timepoints over an 80 day period. The experiment was conducted in the summer of 2017 at the Northeastern University's Marine Science Center with a flow-through seawater system that draws water from Broad Sound in Nahant, Massachusetts (42.416884, −70.907564) using oysters collected from Plum Island Sound, Massachusetts, USA (Site 1, 42.751636, −70.837023; Site 2, 42.725186, −70.855022; Site 3, 42.681764, −70.813498) in late April.

Calcification Rate: Net calcification rate was calculated for oysters surviving to either 50 or 80 days (n = 35) by buoyantly weighing oysters prior to exposure (BW1) and on day 33 or 34 of the exposure (BW2) following the methods of Ries et al. (2009). Buoyant weight was measured in a 27.65 liter tank (48 cm long, 24 cm wide and 24 cm deep) filled with seawater from the flow-through system and was maintained at treatment temperature by an Aqua Euro USA Model MC-1/4HP aquarium chiller. Buoyant weight was measured by completely submerging the oyster on a flat platform suspended from a bottom-loading scale (Cole Parmer Symmetry S-PT 413E, precision = 0.001 g). Care was taken to ensure no bubbles were trapped inside oyster shells. Oysters were weighed three times in the weighing basket, removing the oyster from the basket between each measurement. If replicate measurements varied by more than 0.01 g, oysters were re-weighed. A standard of known weight was weighed every 20 oysters to ensure that no drift was occurring in the scale. To establish a relationship between buoyant weight and dry weight for the purpose of estimating net calcification rate, shells of oysters sampled for tissue within four days of a buoyant weight measurement were soaked in 10% ethanol to remove salts, dried, and weighed. The dry weight was then regressed against the buoyant weight measurement to establish an empirical dry-buoyant weight relationship:

DryWgtBWi(mg)  = 1.87*BWi −2.74

This empirical relationship was then used to calculate dry shell weight at each buoyant weight time point via linear regression. Calculated dry weights were then used to calculate daily calcification rate:

calcification rate (%) = (DryWgtBW2 −DryWgtBW1 )/n * 100/DryWgtBW1

where dry weight (DryWgtBWi) was calculated for each individual using the buoyant weight pre-exposure (BW1) and 33-34 days into the exposure (BW2) and n was the number of days between the two measurements. Lastly, the average daily change in dry weight was divided by initial dry weight to standardize calcification rate for allometric effects, and multiplied by 100 to convert that fraction into a percent.

Extrapallial Fluid: Oyster pHEPF was measured by removing each oyster from its tank, inserting a 5 mL syringe with a flexible 18-gauge polypropylene tip through the luer-lock port into the oyster's extrapallial cavity, and extracting ~0.5–2 mL of extrapallial fluid. Care was taken to avoid puncturing the mantle tissue and inadvertently sampling either the hemolymph or stomach fluid. The pHEPF was measured immediately after extraction with an Orion 91'10DJWP Double Junction micro-pH probe calibrated with pH 7.01 and 10.01 NBS buffers (for slope) and Dickson seawater Certified Reference Material (for intercept).