Date of Award

12-2012

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Oceanography

Advisor

Peter A. Jumars

Second Committee Member

Sara M. Lindsay

Third Committee Member

Lawrence Mayer

Abstract

Marine sediments are continually reworked by resident organisms that control the ecology, chemistry, and physical structure of these vast systems. For example, the creation of a burrow brings oxygenated water into contact with anoxic sediment, facilitating aerobic respiration and supporting a distinct population of bacteria and meiofauna. Collectively, the effects of infauna on sediments and pore waters are known as bioturbation. Studying the behavior organisms that live beneath the sediment surface (infauna) is crucial to understanding the effects of bioturbation. Infauna can be difficult to study, however, because much their activity cannot be directly observed. The purpose of this thesis is to present the results from a set of experiments conducted to better understand aspects of polychaete burrowing behavior and the small-scale distribution of this behavior, particularly with respect to rigid boundaries (walls). Chapter 1 focuses on the behavior of two polychaetes, Allita virens and Clymenella torquata near a rigid wall in sand and mud. The more mobile A. virens shows a tendency to burrow near the wall in mud but not in sand. The proposed basis for this difference is the distinct material properties of the two sediment types. Burrowing in mud occurs by the propagation of cracks. These cracks, and hence burrows, tend to propagate along the surface of walls. In sand, force chains are collections of particles that experience much more stress than the surrounding particles. Stress chains tend to terminate at walls where there high density may inhibit A. virens from burrowing. In contrast to A. virens, C. torquata does not show a significant difference in distance from the wall in sand vs. mud. Because of its limited mobility, C. torquata may be less likely to encounter a wall. In Chapter 2, I report observation of the burrowing behavior of A. virens made using particle image velocimetry (PIV). PIV has seen very limited use in studying burrowing behavior, and the method used for this study improves upon past methods by eliminating the need to make observations across a rigid glass wall. I present several calculations made using this method, including the burrowing speed of A. virens and the distance of its head from the wall of its enclosure. In addition, I quantify A. virens’s effect on the sediment surface including the radial extent of this effect, which could be useful in interpreting the sedimentary record. This method could also be a valuable tool in studying the behavior of a broad range of infaunal organisms.

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