Zooid size parallels contemporaneous oxygen isotopes in a large colony of Pentapora foliacea (Bryozoa)

Abstract

The relationship between seasonal changes in temperature and the size of zooids within cheilostome bryozoans is explored by comparing zooid size and contemporaneous carbonate mineralogy within a single colony of a perennial species that grew in a highly sea- sonal environment. Previously published oxygen isotope profile data from two fronds of a large colony of Pen- tapora foliacea from the Irish Sea record the cyclical patterns related to seasonal changes in temperature experienced by the colony over 3 years of growth. Zooid size data gathered from the same points at which the oxygen isotope data were taken reveal that zooid size and contemporaneous d 18 O values covary. These and previously published data show that zooid size profiling can be confidently used to easily estimate rates of growth and longevity of bryozoan colonies, and further illus- trate the negative relationship between zooid size and ambient temperature. Some inconsistencies in timing between zooid size and d 18 O data may provide insights into the mechanisms behind temperature mediated body size changes in poikilothermic animals.