Brachiopods as archives of intrannual, annual, and interannual environmental variations

Brachiopods have been employed for environmental and climatic reconstructions in the near and geological past. Traditionally, one datapoint is obtained per shell, providing time-averaged bulk signals. However, brachiopods also have the potential to provide time-resolved information on (sub)annual timescales, but this has been understudied due to difficulties in accounting for brachiopod shell growth. We investigated the distribution of delta O-18, delta C-13 and Element/Ca along growth profiles of three Recent terebratulides from temperate and polar latitudes. We employed a novel approach using the Brody-Bertalanffy equation to transform shell distances into ages, permitting the study of periodicity in the measured signatures. We show that, superimposed on ontogenetic trends, faster-growing temperate species record annual and intrannual changes at collection sites, whereas slower-growing Antarctic species are also controlled by endogenous cycles. delta O-18 profiles reflect annual and intrannual variations in midlatitudes and interannual variations at high latitudes. delta C-13 and Element/Ca are additionally influenced by vital effects.