FORAMINIFERAL COLONIZATION AND PROTOPLASM DEGRADATION EXPERIMENTS AT ACTIVE AND INACTIVE LOCATIONS OF HYDRATE RIDGE, OR

After 12 months on the seafloor, eight colonization experiments, SEA³ (Seafloor Epibenthic Attachment Cubes), deployed at both active and inactive methane seep sites of Hydrate Ridge, OR were colonized by over 1,000 Cibicidoides wuellerstorfi and an appreciable number of Cassidulina braziliensis. In this region, C. braziliensis, traditionally regarded as an infaunal taxon, seems to thrive unattached at the sediment-water interface. Although at least one cage in both the active and inactive region was heavily colonized (143 individuals at active and 397 at inactive), C. wuellerstorfi colonization seems to be greater at areas of relatively inactive seepage. Both large (~1mm) and small (~100µm) and right and left coiling C. wuellerstorfi were observed attached to SEA³surfaces.

SEA³s also assessed the potential for foraminiferal protoplasm retention. Individual living foraminifera, terminated by freezing at -80°C, were deployed within natural sediments, exposed to ambient geochemical and microbiological conditions, but encased in mesh of ~63µm (for retention). Specimens were photographed before deployment and after recovery to assess the extent and character of protoplasm within the test. SEA³s were deployed in a region of methane seepage with dissolved bottom water oxygen concentrations of 0.23 to 0.44mL/L, conditions considered conducive to the preservation of organic matter.

These in situ experiments are some of the first to examine the potential for protoplasm retention after death on the deep-sea floor. Many of the individuals deployed were either damaged beyond recognition or lost to the study, probably the result of dissolution. Although some protoplasm was retained after 12 months on the seafloor, only a small percentage of these individuals (10-20%) had the potential to be misidentified as living under typical assessment of Rose Bengal staining.