The 46-day record from the current meter showed that near- 

 bottom currents at the study site fluctuated semidiurnally, both 

 in speed and direction. The current speed (recorded as 300-s 

 averages) reached a minimum of 28 cm s - -"- , and averaged 

 approximately 10 cm s~ . The flow was omnidirectional, but with a 

 strong bias towards west-northwest. A thermometer mounted on the 

 current meter recorded semidiurnal temperature fluctuations 

 between 7.5 and 9.6°C. 



Dissolution patterns on all six alabaster disks showed greater 

 dissolution of the upper surface near the edges than near the 

 center (Mullineaux and Butman, submitted). The patterns were not 

 symmetric, however, and dissolution was consistently higher along 

 one edge than along the opposite edge. Total dissolution 

 (measured as total weight loss) of four disks placed within a 

 meter of each other was much less variable than dissolution of two 

 disks placed 8 m apart (Table 2). The low weight loss of one disk 

 that was strapped to the submersible during one dive indicates 

 that relatively little dissolution (less than 3 g) occurs during a 

 transit between the study site and the surface. The disks, 

 therefore, predominantly reflect shear stress at the study site, 

 rather than shear stress during transit. 



DISCUSSION 



Current meter measurements over the summit of Cross Seamount 

 indicate that the benthic environment is subject to relatively 

 strong currents varying at semidiurnal frequencies. This record is 

 similar to currents recorded at Horizon Guyot, where the 

 semidiurnal fluctuations are thought to be due to internal tides 

 (Noble and Mullineaux, submitted). The XBT, CTD, and current 

 meter results obtained in the present study are being analyzed for 

 evidence that the benthic flow environment at Cross Seamount is 

 sensitive to interactions between the seamount and general oceanic 

 currents (Mullineaux and Butman, submitted). 



The pattern of greater dissolution at the edges of alabaster 

 disks than at the center suggests that the boundary shear stress 

 near the edges was greater than in the center (see Opdyke, Gust and 

 Ledwell, 1987 for a discussion of the relation between dissolution 

 and shear stress). This may have been a consequence of the thin 

 boundary layer near the leading edge, and/or the recirculating eddy 

 at the leading edge. The asymmetry of this pattern is consistent 

 with the directional bias in near-bottom currents measured by the 

 current meter. If the currents had been omnidirectional, the 

 expected dissolution patterns would have been radially symmetric, 

 with the greatest dissolution occurring around the entire perimeter 

 of the disk. If larvae are indeed responding to boundary shear 

 stress over the settlement plates, then the settlement patterns 

 should be correspondingly asymmetric. 



258 



