PARTICULATE AND DISSOLVED ORGANIC CARBON IN OCEANS 219 



31. G. A. Riley, Patterns of Production in Marine Ecosystems, in Ecosystem Structure and 

 Function, J. A. Wiens (Ed.), pp. 91-112, Oregon State University Press, Corvallis, Ore., 

 1972. 



32. G. A. Riley, D. Van Hemert, and P. J. Wangersky, Organic Aggregates in Surface and 

 Deep Waters of the Sargasso Sea, Limnol. Oceanogr., 10: 354-363 (1965). 



33. W. H. Sutcliffe, E. R. Baylor, and D. W. Menzel, Sea Surface Chemistry and Langmuir 

 Circulation, Deep-Sea Res., 10: 233-243 (1963). 



34. G. A. Riley, P. J. Wangersky, and D. Van Hemert, Organic Aggregates in Tropical and 

 Subtropical Surface Waters of the North Atlantic Ocean, Limnol. Oceanogr., 9: 546-550 

 (1964). 



35. D. W. Menzel, Bubbling of Seawater and the Production of Organic Particles: A 

 Reevaluation, Deep-Sea Res., 13: 963-966 (1966). 



36. E. Batoosingh, G. A. Riley, and B. Keshwar, An Analysis of Experimental Methods for 

 Producing Particulate Organic Matter in Seawater by Bubbling, Deep-Sea Res., 16: 

 213-219(1969). 



37. R. W. Sheldon, T. P. T. Evelyn, and T. R. Parsons, On the Occurrence and Formation of 

 Small Particles in Seawater, Limnol. Oceanogr., 12: 367-375 (1967). 



38. E. R. Baylor and W. H. Sutcliffe, Dissolved Organic Matter in Seawater as a Source of 

 Particulate Food, Limnol. Oceanogr., 8: 369-371 (1963). 



DISCUSSION BY ATTENDEES 



Olson: For a solar angle of 90° the UV cutoff is about 325 nm at the 

 surface; and for a solar angle of 30°, the cutoff is about 350 nm. When you talk 

 about the effect of UV on the formation of particulate organic matter, do you 

 mean the wavelength region between 400 and 325 nm, and would not it be 

 better to call this region near UV? 



Riley: Those are the wavelengths that were involved. These were experi- 

 ments in which the water was irradiated with approximately the intensity of 

 natural UV in sunlight. There was formation of particles that could later be 

 observed under the microscope, and there was incorporation of labeled amino 

 acids and sugars. So it is a valid procedure at least experimentally, but it is very 

 hard to say how important it is in the sea. 



Holt: Sedimentation rates seem to be running averages due to the churning 

 of sediments by bottom feeders. Would you care to speculate on the depth to 

 which the sediments are indeed plowed? 



Riley: It is true that some burrowing organisms can be found as deep as 10 

 or 20 cm below the surface, and there is constant reworking of the upper 

 sediment layers. Considering the long time scale involved in sedimentation rates, 

 this greatly smooths the curve for geological history. 



Baylor: I address my question to you and to Dr. Cooke: What do you think 

 of the suggestion that a calcium carbonate crystal of some kind, whether it came 

 from an animal or whether it precipitated normally, would adsorb organic 

 material from the seawater and then slowly sink until it was at a level that would 

 dissolve it, thereby getting rid of the calcium carbonate crystal and leaving the 



