The ecology and morphology of deep-sea benthic foraminifera: The Australian Margin and epifaunal pore characteristics

The distribution and abundance patterns of modern benthic foraminifera are used by paleoceanographers to assess changes in ocean conditions over geologic time. Examination of modern foraminiferal analogs provides the means to determine how these single-celled protists record clues about ambient conditions in their morphology and abundance/distribution patterns. Abundance and vertical distribution patterns of deep-sea benthic foraminifera were examined along the South Australian Margin and Tasman Sea of Australia. This was one of the first studies to examine microhabitat preferences of living (Rose Bengal stained) deep-sea benthic foraminifera within the region. A total of 11 sediment cores were collected via multicorer. Substantial infaunal populations were found in these cores from a region characterized by well oxygenated bottom-water (> 4.0 ml/l) and organic-rich sediments (8--11% organic matter). This mesotrophic environment supported populations of Globocassidulina subglobosa, Valvulineria oblonga, Melonis barleeanum, Pullenia bulloides, Chilostomella oolina, and Hoeglundina elegans. Transport of organic-rich sediments via submarine canyons may account for increased food availability for deep-sea foraminifera in this region.;A relationship between foraminiferal test morphology and ambient oxygen availability has been noted by a number of studies (e.g., Glock et al., 2011; Kuhnt et al., 2013). In an attempt to quantify the relationship between ambient oxygen availability and foraminiferal test pore characteristics, percentage and number of surface pores of 97 specimens of Cibicidoides wuellerstorfi and related taxa were examined from a variety of habitats along an oxygen gradient (0.04--6.20 ml/l). Using ArcGIS and high-resolution SEM images of living (Rose Bengal stained) specimens of Cibicidoides, percentages and number of pores on the tests were quantified. Surface pore percentage (SPORE) analyses of a standardized subset of penultimate and antepenultimate chambers plotted verses ambient bottom-water oxygen concentration yielded a negative correlation with an R2 value of 0.7291, p < 0.001. This SPORE approach provides an effective means to assess ancient bottom-water oxygen concentrations from epifaunal Cibicidoides. .