Identifier

etd-04042006-114658

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

Two ophiuroid species, Hemipholis elongata and Ophiophragmus spp. were studied in laboratory microcosms to elucidate patterns of sediment mixing for key bioturbators in the Mississippi Sound, Mississippi. The effects of bioturbation on artificially stratified sediments in microcosms were traced via time-series digital x-radiography. Preliminary results indicate that for three population densities of the brittle stars (comparable to field densities), a steady state volumetric bioturbation rate of 1-2 cm3/d is reached within two months of introduction to a fresh system. The preservation quotient, q, a fractional measure of preserved primary fabric, reached a minimum of 0.5 during the 16-week experiment. Maximum depth of bioturbation appears to be inversely proportional to population density in these species, with individuals in sparser populations also being less mobile. Thus, greater dispersive mixing occurs to shallower depths in sediments hosting greater population densities. In addition, bioturbation rates appear to decrease exponentially with depth, with volumetric reworking at the base of the mixed layer being approximately 1x10-3 those at the surface. Field measurements after event layer deposition showed that re-colonization by the original key bioturbators was not immediate and a lag time of at least 8 months may valid for future modeling attempts in similar settings.

Date

2006

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Samuel Bentley

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