FRACTAL DIMENSIONS OF MARINE SNOW DETERMINED FROM IMAGE-ANALYSIS OF IN-SITU PHOTOGRAPHS

Seventy seven in situ photographs of marine snow ranging in size from 1 to 60 mm were used to calculate one- and two-dimensional fractal dim ensions, 41 and D-2, in order to characterize aggregate morphology wit h respect to aggregate perimeter and cross-sectional area. The lowest fractal dimension of D-2 = 1.28 +/- 0.11 was calculated for marine sno w aggregates composed predominantly of a single type of particle (e.g. diatoms or fecal pellets) containing large amounts of miscellaneous d ebris. Marine snow formed by the aggregation of fecal pellets (4 = 1.3 4 +/- 0.16), non-identifiable particles (amorphous, 42 = 1.63 +/- 0.72 ), and diatoms (D-2 = 1.86 +/- 0.13) had increasingly larger fractal d imensions. When combined into a single group, all marine snow aggregat es had a fractal dimension of 1.72 +/- 0.07. Larvacean houses, formed originally from a single, nearly spherical particle, were found to hav e a 4 value close to the Euclidean value of 2. Based on fractal geomet rical relationships, 42 Should have been equal to previous estimates o f 43, a three-dimensional fractal dimension. Instead, the D-2 value of 1.72 for the combined group was larger than previous estimates of D-3 Of 1.39 and 1.52, probably because of the dominant influence of the d iatom aggregates on the combined group. Diatom aggregates had the high est fractal dimensions and covered the widest size range of all catego ries of particles examined.