Latitudinal influences on bryozoan calcification through the Paleozoic

Bryozoans are active non-phototrophic biomineralizers that precipitate their calcareous skeletons in sea-water. Carbonate saturation states vary temporally and spatially in Paleozoic oceans, and we used the Bryozoan Skeletal Index (BSI) to investigate whether bryozoan calcification is controlled by seawater chemistry in Paleozoic trepostome and cryptostome bryozoans. Our results show that cryptostome bryozoan genera are influenced by ocean chemistry throughout the Paleozoic and precipitate the most calcite per autozooid at lower latitudes, where carbonate saturation states are generally higher, and less in mid-latitudes where carbonate will be relatively undersaturated. Trepostome bryozoan genera show a similar, but weaker, trend for the Ordovician to Devonian, suggesting that like the cryptostomes they are unable to metabolically overcome falling saturation states and simply precipitate less robust skeletons at higher-latitudes. Carboniferous to Triassic trepostomes differ however and ...