The relationship between floc area and backscatter during a spring phytoplankton bloom

A 10-week study during the spring phytoplankton bloom in Bedford Basin, Nova Scotia showed two different linear functional relationships between estimates of the in situ particulate backscatter coefficient (bbp) and the projected area concentration of particles larger than 100 μm. In the first part of the study (26 February–19 March, 1998), bbp increased more rapidly with floc projected area concentration than it did during the second part of the study (26 March–30 April, 1998). The observed change in relationship was accompanied by an increase in both size and abundance of large particle aggregates in the second part of the study and an inferred shift to more organic bulk particle composition during and after the bloom, also the second part of the study. A simple conceptual model explains these observations. Before the bloom, suspended particles in Bedford Basin were primarily inorganic. As the bloom began and progressed, organic particles became dominant and detrital particles began to aggregate to form flocs.