The carbon, nitrogen and mass content of marine snow as a function of aggregate size

The particulate organic carbon (POC), particulate organic nitrogen (PON), dry mass, and chlorophyll a content of marine snow as a function of individual aggregate size was determined from undisturbed natural aggregates photographed and collected in situ by SCUBA divers at 15 stations off coastal California in order to quantify the matter available in large particles for various ecological processes. POC, PON, and dry mass content were highly significant exponential functions of aggregate volume and were similar for all aggregates regardless of aggregate type, origin, composition or season of collection. POC and PON made up 17–39% and 1.7–6.0%, respectively, of aggregates by weight. C:N ratios increased with increasing aggregate size, suggesting that larger aggregates were older and more refractory than smaller ones. Similarity in the size-specific POC, PON, and mass content of different types of aggregates indicates that the quantities of these materials existing in the larger particle size fractions of the upper ocean could be estimated from profiles of particle size and abundance with depth obtained with in situ camera systems. Such estimates will allow assessment of the availability of marine snow to large particle consumers and decomposers and to sedimentation processes.