Influence of seawater temperature on growth bands, mineralogy and carbonate production in a bioconstructional bryozoan

The cheilostome bryozoan Pentapora, an important benthic carbonate producer on non-tropical continental shelves, displays seasonal variations in deposition of the calcareous skeleton reflected by ‘winter’ and ‘summer’ growth bands. Studies on colonies from Atlantic and Mediterranean localities show that the ratio of the heights of these growth bands correlates significantly with mean annual range of temperature (MART) and mean annual temperature (MAT). The locality with the lowest MART and MAT showed the greatest wt% of calcite in the winter growth band. The opposite was true for the locality with the highest MART and MAT. Carbonate standing stock and carbonate production estimated for Atlantic localities were an order of magnitude lower than those measured at Mediterranean localities. Variability in skeletal carbonate depositional pattern and mineralogy suggests that fossil and historical collections of Pentapora may be useful indicators of past thermal conditions.