28 



SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES 



500- 



400- 



i 300 



O 200- 



100- 



0 



— ■— Regional Means 

 ■ Specimen means 



N (number of Measurements) 



8 



GOM Aleut 



1 ' T" 



7 6 



N. Lab. ® 



NE NF S. Lab. Arctic 



"1 — ' — I — ' — I — ' — I — ' — r 

 5 4 3 2 1 

 Yearly Mean Temperature (°C) 

 (by region) 



I B^y I 



0 



-1 



FIGURE 22. Cirowth rate of C. conipdctuni (red) and C. nereostratiim (blue) as a function of mean yearly ambient temperature. The regional 

 temperature derivation is described in the Figure 23 caption. The downturn in the curve on the right is due to the length of winter sea ice (Halfar, 

 unpublished data). 



such fractures is sometimes clearly visible in SEM images. Gener- 

 ally, such alteration occurs only near damage sites and is easily 

 detected and avoided. As older clathrostromes are discovered, it 

 will be necessary to carefully examine the oldest part of the coral- 

 line carbonate for potential diagenesis. 



Ecology and Geomorphology 



The 201 0-20 1 1 cruises to Labrador demonstrated that outer 

 coast islands can provide localized optimum conditions (Figures 

 2A,B, 25A,B) for the development of clathrostromes of Clatbro- 

 tnorpbitm coiupactum. On the leeward sides of these islands and 



especially on the more protected parts of outer coast island com- 

 plexes, where wave exposure is moderated, clathrostromes are 

 often well developed. Particularly, where stable bedrock shores 

 have a minimum overburden of glacial till (avoiding wave tools) 

 yet have enough wave action to seasonally limit sea urchin graz- 

 ing, an optimum environment for carbonate production in C. 

 compactum is present. Low-lying, domed bedrock islets lacking 

 the high cliffy shores that could shed falling boulders and cobbles 

 onto the underlying shore can have particularly well-developed 

 clathrostromes. Moderately steep bottoms of cobbles and large 

 boulders that limit downslope movement create the optimum 

 conditions for preserving clathrostromes for many centuries. 



