From ecology to geochemistry to DNA: New information about Cibicidoides wuellerstorfi

Abstract:

Cibicidoides wuellerstorfi remains one of the most useful benthic species in paleoceanographic studies due to its epibenthic lifestyle and use in geochemical studies. However, misconceptions exist about this important taxon. Genetic comparisons with Genbank have shown that C. wuellerstorfi living in the Pacific are the same species as those in the North Atlantic, and the Antarctic. Sediment cores taken on a transect through the Southern California Bight oxygen minimum zone (OMZ) have shown that C. wuellerstorfi make up as much as 11.2% of the stained population despite oxygen-poor conditions (0.47-0.63 mL/L with water depths ranging from 360-3000m). Living C. wuellerstorfi has also been found to inhabit many areas of methane seepage with available oxygen levels as low as 0.23mL/L. Colonization of experimental substrates at Hydrate Ridge revealed substantial colonization within 12 months (~1,000 individuals/~5,000cm³) and preference between substrate materials (e.g. abundance on plastic and absence on adjacent wood). As in other seep studies; stable carbon isotopic values of C. wuellerstorfi of Hydrate Ridge seeps exhibit a wider range than their non-seep counterparts. Stable carbon isotopes at Hydrate Ridge were significantly different between seep and non-seep locations despite having an overlapping range. Changes in seep fluid characteristics (e.g. temperature and composition) are evidently recorded in the δ¹⁸O of benthic foraminiferal calcite at methane seeps and hydrothermal seeps in the Pacific. The use of δ¹⁸O of benthic foraminiferal calcite may hold promise as a valuable means to assess seep characteristics, especially in recognizing and evaluating hydrothermal seeps.

These results have significant implications for the cosmopolitan distribution, ecophenotypic variation, and genetic exchange of C. wuellerstorfi. The prevalence of C. wuellerstorfi in areas of low oxygen availability shows that this species is able to thrive in oxygen-poor habitats, and provides strong evidence that this taxon is not a reliable indicator of oxygen rich environments. Geochemical results suggest that there is a relationship between seeping fluids and foraminiferal calcite geochemistry and implying that novel geochemical relationships should be further explored at cold and hydrothermal seeps.