Next generation sequencing to identify lacustrine haptophytes in the canadian prairies: significance for temperature proxy applications

Long-chain alkenones (LCAs) are lipids produced by a restricted number species of haptophyte algae of the Isochrysidales Order, and which have a great potential for palaeotemperature reconstructions in lacustrine settings. However, it is first essential to identify the LCA-producing haptophyte species present to select the most appropriate calibration of the LCA-based temperature proxy U37K. In this study, we use next generation sequencing (NGS) targeting the haptophyte 18S rRNA gene in five lakes with distinct LCA profiles from the Canadian Prairies to determine the LCA-producer(s). In total 374 operational taxonomic units (OTUs) were identified across the sample studied, of which 234 fell within the Phylum Haptophyta. When considering the most represented OTUs, three were assigned as LCA-producers, one of which was included in the Group I of LCA-producing haptophytes and two in the Group II of LCA-producing haptophytes. Even though the OTU from the Group I haptophytes produced a highly specific LCA profile, one OTU from Group II haptophytes produced different LCA profiles. These results, compared with previous studies, allow us to discuss the importance of genomic identification of LCA-producing species and to determine which calibrations of the U37K index are the most appropriate for temperature reconstructions in the Canadian Prairies. Our results also suggest that the temperature dependency is likely consistent within different taxa from Group I and Group II haptophytes, but that other environmental parameters influence the temperature calibration.