AFSC/RACE/SAP/Foy: The effects of ocean acidification on ovigerous Tanner crab size, calcium, and magnesium content. : Kodiak Island, Alaska.

To study the effects of ocean acidification we conducted laboratory experiments with adult ovigerous females of the economically important southern Tanner crab, Chionoecetes bairdi.

Ovigerous females were reared in one of 3 treatments: control (ambient pH ~8.1), pH 7.8, and pH 7.5 for 2 years. The adult female sizes used for the experiments ranged from 87 to 112 mm

among the three treatments. Throughout the experiment , pH and temperature were measured daily in each of the 3 treatments. The mean daily temperature was 5.0 C, varied seasonally from

a low of ~1 C in January 2012 to a high of ~ 9C in August 2011, and did not vary between treatments. pH remained significantly different among the treatments. Brooding duration for each

female was defined as beginning the day of egg extrusion in 2012 and ended when larval hatching began in 2013. Mean brood duration ranged from 340 to 366 days. Magnesium and calcium content

were determined at the end of the experiment from a portion of exoskeleton. Magnesium did not differ with pH treatment but the ratio of magnesium to calcium did differ among treatments.

The purpose of the female Tanner crab experiment is to provide the initial carapace length, the brood duration, and the death date for each female and the specific treatment data

(pH and temperature) used in the experiment. The (calcium) Ca and (magnesium) Mg dataset is to provide the carapace mineral data associated with the three treatments collected at the

end of the experiment

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MS Excel 2012

The accuracy of the size, seawater pH and temperature, and female calcium and magnesium content is high (less than 1% difference from actual) due

to the low measurement error of the instruments used, measurement accuracy and precision controlled through system calibrations, and frequency of observations

during the experiment. The brood duration data is 100% accurate due to daily (repeated) checking of female condition so that the hatch date is known.

The data collected on the adult female experiments are complete (i.e. not filtered).

Female size data were compared to known size frequency data. No quantitative assessments of consistency were made. Brood Duration information was broadly compared

to previous studies conducted on Tanner crab at the Kodiak Laboratory and to similar species from similar collection locations while considering environmental and

laboratory conditions. No quantitative assessments of consistency were made. Female pH temperature information was broadly compared to known seawater conditions in the

Gulf of Alaska while taking into account laboratory variability and statistically compared to a control (alpha=0.05). Female Ca and Mg information was broadly compared

to previous studies on crab shell mineral content and to similar measurements made on similar crab species and statistically compared to a control (alpha=0.05).

For example, for comparing we used the study described in Mathis, Jeremy T., Jessica N. Cross,

and Nicholas R. Bates. "Coupling primary production and terrestrial runoff to ocean acidification and carbonate

mineral suppression in the eastern Bering Sea." Journal of Geophysical Research: Oceans (19782012) 116.C2 (2011).

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