Poster Australian Marine Sciences Association 2022

Variable [Mg2+] in seawater forces mineralogy change in Spirobranchus cariniferus calcification     (#537)

Ian Dixon-Anderson 1 , Abigail M. Smith 1 , Christina M. McGraw 1
  1. University of Otago, Tainui, Dunedin, OTAGO, New Zealand

We grew Mytilus edilus (blue mussels) and Spirobrachus cariniferus (tubeworms) in controlled artificial seawater with five different Mg/Ca ratio treatments for 50 days. We measured survival, growth rate, shell thickness and shell composition to understand invertebrate responses to artificial seawater with different Mg/Ca ratios. Survival and growth rate in both mussels and tubeworms were significantly lower in the lowest Mg treatment. Skeletal composition of tubeworms was significantly altered in low Mg treatments, with new calcite shifting to a lower weight percentage of Mg in calcite. These species demonstrate capacity to adjust to variations in seawater, some of which may be recorded in their skeletal composition. Although standard dogma suggests that [Mg2+] is conservative in the open ocean, some studies suggest that Mg/Ca may be more variable than previously thought. Our data show that exposure to seawater with variable Mg/Ca, especially low levels of Mg, could affect survival, growth and skeletal composition in marine invertebrates.