Examining arm regeneration effects on Ophiuroid Amphipholis gracillima when exposed to lowered pH levels

Ocean acidification occurs when CO2 forms carbonic acid in sea water and effectively lowers prevailing pH levels. This may ultimately be detrimental to benthic marine animals that calcify such as echinoderms in the class Ophiuroidea which have and exoskeleton composed of magnesium calcite. As such, brittlestars are particularly susceptible to dissolution as ocean pH decreases. The purpose of this study was to determine the potential effects of ocean acidification on benthic invertebrate communities by examining how changes in pH may affect calcification in calcareous species. Hydrochloric Acid (HCL) was used to reduce the pH of sea water to simulate the process of acidification. The burrowing brittlestar Amphipholis gracillima was exposed to pH levels of 7.0, 7.2, 7.4, 7.6, 7.8, and 8.0 for 14 days. Theoretically it would be advantageous for A. gracillima to complete the regeneration process quickly so that the arms could fully participate in feeding, and locomotion/burrowing. Triplicate groups of A. gracillima were exposed to various pH levels in over a 14 d period. Total regeneration was measured in centimeters and compared. Arm regeneration was lowest at pH levels less than 7.6. The greatest arm regeneration (0.6cm mean growth) occurred at pH level 7.8. The lowest arm regeneration (0.3cm mean growth) occurred at pH level 7.2. The effects of ocean acidification on regenerating disk of A. gracillima may be of interest in future studies.