sediment preference may be related to its equally unique deposit-feeding habit 

 since silt-clay sediments are typically rich in organic matter. MotiUty of N. 

 incisa in fine sediment can best be described as an extended period of open 

 burrow habitation followed by its extension of the burrow developing another 

 temporary burrow. This habit is different from infauna that constantly burrow 

 as predators, or continual deposit-feeders, or those which reburrow only 

 because of complete burrow destruction. Whatever the purpose(s) for high 

 burrowing rates by N. incisa, reported densities of 600 — 1200 per m may 

 significantly perforate the top 10 — 15 cm of sediment during warmer months 

 (such as suggested by model #1 above). This perforation probably results in a 

 large increase in the surface area of the sediment-water interface (model #2). 

 Since both present and some past burrows are irrigated, this expansion of 

 surface area may result in a general biological model for sediment-seawater 

 exchange, assuming a gradient as in dissolved oxygen (model #3). 



ACKNOWLEDGMENT 



We gratefully acknowledge the stimulating discussions and criticisms of Drs. 

 Allen C. Myers, K. John Scott, and Robert B. Whitlatch. This work is a portion of 

 the first author's dissertation and much is owed to his major professor. Dr. Winona 

 B. Vernberg. 



REFERENCES 



l.Aller, Robert C. and Josephine Y. Yingst. 1978. Biogeochemistry of 

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2. Bellan, Gerard. 1969. Contribution a I'Etude des Annelides Polychetes de 

 la Region de Rovinj (Yougoslavia). Jugoslavenska Akademija Znanosti I 

 Umje+nosti. pp. 25-55. 



S.Clark, R.B. 1962. Observations on the Food of Nephtys. Limnol. 

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4. Clark, R.B., J.R. Alder and A.D. Mclntyre. 1962. The Distribution of 

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S.Davis, Wayne R. 1979b. Feeding Activities in Nephtys incisa. Part II of 

 Ph.D. Thesis, University of South Carolina. 



6. Davis, Wayne R. 1979c. Irrigation Activities in Nephtys incisa. Part III of 

 Ph.D. Thesis, University of South Carolina. 



317 



