A mooring system was designed and constructed to make possible the installation and the recovery of racks of sample panels for a study of deep-ocean wood-boring molluscs. Racks containing pine, fir, oak, and cedar boards were exposed to borer attack at six stations with depths of 50, 100, 150, 200, 500 and 1000 meters, all west of Depoe Bay, Oregon. Two wood-boring molluscs, a pholad, Xylophaga washingtona Bartsch, and a teredinid, Bankia setacea (Tyron), were recovered from exposed wood materials. Xylophaga washingtona was the dominant form and was found at all three deep stations. Bankia setacea was found only at the 200-meter site and in very low numbers. This reports the deepest known teredinid actively settling and boring into a test board. Borer attack increased in intensity with time, and in general, decreased with increasing depth. Initial attack appeared to commence right above the line where sample panels were in contact with the sediment. Attack was heaviest in this zone and decreased with increasing distance upward from the sea-sediment interface, approaching zero in about 20 centimeters. In general cedar was the most heavily attacked wood type followed in turn by pine, fir, and then oak, which proved the most resistant to xylophagan borers, The degree of maximum borer penetration into any wood type correlated nicely with the density of the wood, higher density wood being correspondingly most resistant to borer attack. Degree of maximum borer penetration increased with time and decreased with increasing depth. The mooring system is fully described along with a summary of field installation and recovery methods. Future research problems are suggested. / Graduation date: 1968

Thesis (M. Phil.)--University of Hong Kong, 1976.

published_or_final_version / Zoology / Master / Master of Philosophy

Thesis (doctoral)--Université de Paris, 1958. / Includes bibliographical references (leaves 167-173).

Marine bioeroders, borers, and burrowers can have drastic effects to marine habitats and facilities. By physically altering the structure of marine habitats, these organisms may elicit ecosystem-level effects that cascade through the community. While borer damage is typically restricted to a few substratum types, burrowing isopods in the genus Sphaeroma attack a diversity of substrata in tropical and temperate systems. My dissertation examined how boring sphaeromatid isopods affect coastal habitats (saltmarshes, mangroves) and other estuarine substrata as well as marine structures. I used a combination of lab and mensurative field experiments to quantify the effects of boring by isopods and examine how select factors affect the colonization, hence burrowing damage by isopods. I explored these questions primarily using the temperate boring sphaeromatid, Sphaeroma quoianum, as a model organism. My initial lab experiments quantified the per capita erosion rates of S. quoianum in four commonly attacked estuarine substrata. I found marsh banks and Styrofoam substrata were the most affected per capita. I supplemented this lab experiment with a year-long mensurative field experiment examining how erosion rates differ between marshes infested and uninfested by boring isopods. Marshes infested with isopods eroded 300% faster than uninfested marshes. I further examined the boring effects on Styrofoam floats. I compiled surveys and observations and conducted a short experiment to describe how isopods affect Styrofoam floats used in floating docks. I observed dense colonies of isopods attacking floats and expelling millions of plastic particles in the ocean. The boring effects to simulated Styrofoam floats were also affected by seawater temperature. Burrowing effects in Styrofoam floats exhibited a curvilinear relationship with temperature and peaked around 18°C. These results suggest a 1-2°C increase in water temperature could increase boring effects 5-17% of populations of isopods in Oregon and California bays. To examine the small-scale factors that mediate colonization and boring, I conducted a series of binary choice experiments. I found the presence of conspecifics, biofilm, and shade were important factors influencing colonization. These small scale factors likely explain why isopod attack is focused in some substrata. Finally, to examine the boring effects of tropical isopods in mangroves, I examined the associations between burrowing by S. terebrans and mangrove performance and fecundity. I found negative relationships between boring effects and performance and fecundity in two mangrove species in a restored mangrove stand in Taiwan. Together, these studies elucidate the effects of bioerosive isopods on saltmarshes, mangroves, and marine structures. However, the similar mechanisms involved in bioerosion in other boring species suggest that these results can be used to infer similar effects of other borers. In addition, since many species of sphaeromatid isopods have been introduced, this research shows how the effects of a non-native bioeroder can damage marine facilities and degrade and alter marine habitats. Through biological erosion and thus changing the physical structure of a marine habitat these non-native species can have ecosystem-level effects that cascade throughout the local community.

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