AGGREGATION OF DIATOM BLOOM IN A MESOCOSM - BULK AND INDIVIDUAL PARTICLE OPTICAL MEASUREMENTS

Optical measurements were acquired during a controlled, diatom-dominat ed, phytoplankton bloom and aggregation event engineered in a 1200 lit er laboratory mesocosm. Observations included beam attenuation (c) at 660 nm and particle absorption spectra for phytoplankton and detritus. Despite intense bloom conditions in the mesocosm (chlorophyll a conce ntrations exceeding 165 mg/l and c exceeding 9 m(-1)), most optical pa rameters covaried linearly with biochemical parameters. There were sig nificant positive correlations for dry mass versus the particle attenu ation coefficient (c(p)) at 660 nm, particulate organic carbon versus the computed particle scattering coefficient (b(p)) at 660 nm, and chl orophyll a versus the measured particulate absorption coefficient (a(p )) at 660 nm, and chlorophyll a versus the measured absorption coeffic ient for phytoplankton (a(phi)) at 673 nm. Multiple-component model si mulations of optical and biochemical measurements accurately predicted particulate organic carbon (POC), particulate organic nitrogen (PON), and chlorophyll a concentrations using c(p) and a(p) measurements. Si milar equations for c(p) and a(p) estimates using the biochemical meas urements are also presented. New commercially available instruments to measure c(lambda) and a(lambda) should make remote PON, POC, and Chl a estimates practical upon measurements of site-specific relationships similar to those presented here.