SGER: Radiometric Dating of Whalebones: A Method for Studying Succession and Persistence of Whalefall Chemoautotrophic Assemblages

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Stephens OCE 9902095The discovery of chemoautotrophic communities living on seafloor whale-fall carcass in the Santa Catalina Basin in 1987 and later at a number of other locations has raised the question about their role and importance for deep-sea biology because these communities bear taxonomic similarities to other deep-sea reducing environments, such as hydrothermal vents. Whale-falls are of biological significance for the following reasons: 1) their potential roles as stepping-stones for sulfophilic species in the deep-sea; 2) they enhance the biodiversity of the deep-sea; and 3) they can provide insights into anthropogenic influences, such as sewage sludge emplacement, on the marine environment.Knowledge of community succession and the persistence times of whale-skeleton chemoautotrophic assemblages is needed to reliably estimate the abundance of whale-fall habitats and to understand the dynamics of the whale-fall communities and their potential roles as stepping stones for sulfophilic species. Time series observations of several communities living on carcasses that were experimentally placed on the seafloor up to six years ago are providing information regarding early succession, but currently there is no method available to accurately estimate the ages of skeletons discovered on the seafloor.This study will develop and apply radiochemical methods for estimating the ages of seafloor whalebone communities. Preliminary measurements performed on samples of a known age yielded calculated ages that are in good agreement with the known bone ages, thus confirming the feasibility of the methods. Further testing of the methods and assumptions will be performed using additional whale bones of known age, including samples from a carcass that was planted for over 5 years on the seafloor. Upon successful establishment of the technique, application to bones from two skeletons discovered on the seafloor (of unknown age) will follow. The dating techniques will be useful for determining the patters of succession and development and the persistence times of whale-fall chemoautotrophic communities..