Cuticle elemental concentrations of juvenile California spiny lobsters (Panulirus interruptus) in response to ocean acidification

We examined the response of multiple structures used for predator defense in the California spiny lobster, Panulirus interruptus, to a series of ocean acidification-like conditions. Lobsters were collected by modified commercial traps offshore La Jolla, CA (in the area around 32.8534193, -117.2687516) in October 2016 and held at ambient conditions (pH 7.97, 16.5°C) before exposure to stable or diurnally fluctuating reduced pH conditions established by bubbling CO2 and as measured using best practices (ambient pH/stable, 7.97, 16.5°C; reduced pH/stable 7.67, 16.6°C; reduced pH with low fluctuations, 7.67 ± 0.05, 16.4°C; reduced pH with high fluctuations, 7.67 ± 0.10, 16.4°C). After three months, inductively-coupled x-ray spectrometry (ICP-MS) was performed on cuticle samples at the Scripps Isotope Geochemistry Laboratory (SIGL) for a precise quantification of elements (µmol/mg sample). The carapace spine was air-dried and then trimmed so only the spine remained with no setae, and the abdominal segment was cut as a 1 x 1 cm² from the center of the second abdominal segment and air-dried. Samples were weighed and placed in Teflon vials for digestion with 0.5 ml of concentrated Teflon-distilled (TD) nitric acid (HNO3) on a hotplate at 100°C for >24 h. Samples were dried down and diluted by a factor of 4000 with 2% TD HNO3 before being transferred to pre-cleaned centrifuge tubes for analysis. Samples were doped with an indium solution to monitor instrumental drift. Measurements were done using a ThermoScientific iCAPq c ICP-MS (Thermo Fisher Scientific GmbH, Bremen, Germany) in standard mode. Masses of Mg and Ca were sequentially measured for 30 ratios, resulting in internal precision of <2% (2 s.d.). Elements were corrected for total mole fraction. Total procedural blanks represented