As. Ackleh et al., ESTIMATION OF STICKING AND CONTACT EFFICIENCIES IN AGGREGATION OF PHYTOPLANKTON - THE 1993 SIGMA TANK EXPERIMENT, Deep-sea research. Part 2. Topical studies in oceanography, 42(1), 1995, pp. 185-201
The coagulation of phytoplankton, a fundamental mechanism for vertical
flux in the oceans and a possible predatory escape mechanism, is a fu
nction of the density of suspended particles and at least three enigma
tic system processes: the encounter rate of the particles; the contact
efficiency of various sized particles upon encounter; and the efficie
ncy of sticking upon contact. A variant of a continuous coagulation mo
del, including the second-order aggregation rate representation and da
ta obtained from the 1993 SIGMA tank experiment at Santa Barbara, are
used first to estimate 'stickiness', the efficiency of sticking given
that a collision occurs. Primary tools are an inverse, least squares m
ethodology, an aggregation model, and an individual growth model for p
hytoplankton. The model output corresponds well with the data for smal
ler sized particles (<0.4 mm(3)); however, predicted densities for lar
ger particles were less than observed, and the predicted timing of the
bloom was earlier than observed. These anomalies led to an investigat
ion of the interacting roles of stickiness, contact efficiency, and nu
trient storage in individual cells. The analyses suggest that (i) aggr
egation is relatively insensitive to the sticking efficiency, and thus
it is difficult to estimate stickiness accurately by fitting aggregat
ion data; (ii) contact efficiency appears to be more functionally vari
able than assumed in traditional representations, and estimating conta
ct efficiency, jointly with the sticking efficiency, generally produce
s better agreement with the SIGMA experimental size particle data spec
trum; (iii) for the SIGMA tank environment, estimates of contact effic
iency are dimensionally more closely related to diameter than to the t
raditional surface area representation; and (iv) stored nutrient reser
ves may play a fundamental role in governing timing of peak algal bloo
m and dynamics of aggregates; inclusion of nutrient storage improves e
stimation of peak bloom, but does not significantly improve prediction
of aggregate dynamics in the SIGMA tank experiment.