Patterns of magnesium-calcite distribution in the skeleton of some polar bryozoan species

Polar marine environments are already starting to exhibit the effects of climate change. The Arctic is the most rapidly warming place on Earth, and changes of the seawater chemistry of polar oceans have been recorded. Calcifying Bryozoa have diverse skeletal mineralogies making them an ideal model for investigating differences caused by environmental change. The aim of this study is to quantify the skeletal mineralogical diversity of polar bryozoans using X-ray diffraction (XRD). Six species of erect Bryozoa were analysed, three Arctic and three Antarctic species. Within each of the three species from each region, one has a cemented attachment point, one has flexible growth and the third is attached by chitinous rootlets. The analysis shows no significant difference in Mg-calcite distribution along the length of the six species but does show species-specific variation in both the consistency of Mg-calcite distribution along the length of a colony and the relationship between concentration of Mg-calcite in the root and growing tip. Analysis shows a statistically significant trend of increasing Mg-calcite concentration with increasing temperature. This adds further data to a growing body of published evidence for this mineralogy trend. The results of this study suggest that if bryozoan species are to be used as indicators of environmental change then it will be critical to have robust, replicated data of species-specific profiles for Mg-calcite distribution. This data, viewed alongside published mineralogy trends, may allow the use of skeletal mineralogy as a register of environmental effects and may enable monitoring of future impacts of climate change in marine benthic ecosystems.