Time-integrated patterns of boundary shear stress were 

 measured on the scale of individual settlement plates by 

 quantifying the dissolution of flat disks of alabaster (crystalline 

 calcium sulfate). The disks were 15 cm in diameter and 1-cm thick, 

 so even though they were slightly smaller than the thick settlement 

 plates, they had the same shape and leading-edge thickness. They 

 were glued to plastic bases, and coated with Tile Clad along the 

 edges, so that only the upper surface of the alabaster was exposed 

 to seawater. Disks were deployed on the seafloor at the site for 

 2- and 3-day durations. Total dissolution of a disk was measured 

 by weighing it before and after deployment. Dissolution patterns 

 with respect to the edge of a disk were quantified by placing a 

 grid of 90 points over the disk and measuring (in millimeters) the 

 amount of alabaster dissolved from the upper surface at each point 

 on the grid. Although calculations of u* can be made from flush- 

 mounted alabaster plates (Santschi, Bower, Nyffeler, Azevedo and 

 Broecker, 1983; Opdyke, Gust and Ledwell, 1987); the applicability 

 of these empirical equations to thick plates remains to be tested. 

 The disks used in the Cross Seamount study were made intentionally 

 with thick edges, so that shear stress patterns could be compared 

 directly with larval settlement patterns on the Lexan plates. 

 Thus, it was the spatial patterns of dissolution on the alabaster 

 plates, rather than quantitative estimates of u*, that were of 

 primary interest in this study. 



RESULTS 



Larval Settlement Patterns 



The mean number of attached individuals found on three 

 replicate plates of the four treatments are listed in Table 1. 

 Foraminifers were much more abundant than metazoans on all plate 

 treatments. Settlement onto the thick-elevated plates was 

 significantly higher than onto any of the other plates (Model I 

 ANOVA and Student Neumann Keuls a posteriori test of the log (x+1)- 

 transformed abundance data; P< 0.05), and settlement onto both the 

 thick-elevated plate types (Lexan and manganese covered) was 

 greater than onto the thick-benthic plates. 



Flow Environment 



The results of two sets of XBT profiles, taken in transects 

 over the summit of Cross Seamount during the deployment and 

 recovery cruises, indicated that the upper mixed layer was 70-m 

 thick and the steepest part of the thermocline was between 200-300 

 m water depth. No signature of the seamount was detected in 

 isotherms on the west-to-east transect taken during the deployment 

 cruise. On the recovery cruise, however, a south-to north transect 

 showed isotherms doming over the seamount summit (with vertical 

 displacements of up to 30 m), indicating an interaction between the 

 seamount and the general oceanic currents. 



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