Al. Alldredge et Km. Crocker, WHY DO SINKING MUCILAGE AGGREGATES ACCUMULATE IN THE WATER COLUMN, Science of the total environment, 165(1-3), 1995, pp. 15-22
The formation of nuisance scums of mucilage on the ocean surface requi
res that the sinking mucilage aggregates which eventually form the scu
ms first become neutrally buoyant so as to accumulate in the water col
umn. We hypothesize that neutral buoyancy is attained by an aggregate
sinking from a lower density surface layer into a higher density haloc
line if some proportion of the aggregate's volume is occupied by lower
density mucus which is resistant to diffusion of salts and water. A m
odel, based on the porosities, excess densities, and sinking rates of
natural diatom aggregates obtained empirically, demonstrates that only
0.5-2% of the volume of an aggregate need be occupied by mucus for it
to attain neutral buoyancy and accumulate at even modest pycnoclines.
The model predicts accumulations at vertical density gradients increa
sing by only 1-3 sigma(t), similar to vertical changes in density prev
iously observed at the depths of mucus accumulations in the Adriatic S
ea.