38 



SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES 



FIGURE 29. Cor-strome, with abundant C. conipactunu from 10-20 m in Arctic Bay in northernmost Baffin Island (73°N). These plants are 

 growing in an inner-bay environment, not the optimum habitat for this species. Although only a single image, it suggests that extensive clath- 

 rostrome development in intermediate-exposure, island-complex environments is likely in the high Arctic. © Nick Caloyianis. Reprinted with 

 permission. 



if fleshy algae production were to be enhanced in a more acidic 

 sea, sea urchin grazing on corallines might actually be reduced 

 because of greater access to preferred seaweed foods. Finally, 

 most significant grazers in clathrostrome environments also have 

 critical carbonate hard parts that could be impacted by increased 

 seawater acidity. Ocean acidification will certainly impact ben- 

 thic communities, but the changes will be hard to predict with- 

 out extensive ecosystem level experiments. Single-species studies 

 are inadequate to the task. 



CONCLUSIONS 



Calcified encrusting coralline algae have a considerably more 

 complex anatomical structure than a reading of current literature 

 would suggest. As we document here, the genus Clathronior- 

 phtim, widespread in Subarctic and Arctic seas, provides a highly 



integrated anatomy and reproduction, modified by numerous envi- 

 ronmental elements. Understanding this complexity is essential to 

 the accurate interpretation of geochemical analyses of the skeleton 

 and has already led to the development of a new archive for sea 

 ice providing paleoclimatic information not previously available. 



Also, the role of corallines in general, and keystone Clath- 

 romorphum species in particular, in forming cold-water rocky- 

 bottom carbonates has been widely interpreted as a degraded 

 ecosystem resulting from intensive overfishing. As we show, 

 Clathromorphum species grow very slowly, primarily under tem- 

 perature control, and have developed anatomical and cellular 

 structures that potentially allow longevities of many centuries. 

 This understanding is crucial to interpreting the ecological im- 

 portance of this widespread carbonate structure, with its unique 

 associations of organisms as a key ecosystem of Subarctic and 

 Arctic rocky shores; its age shows clearly that it is not a degraded 

 system. Also, we show how understanding geomorphological 



