Turbidity in Tampa Bay was monitored for 6 months using a towable 1-m optical transmissometer system. The system provided for continuous chart readout and allowed short-term water-mass migrations to be mapped quantitatively. Transmission readings ranged from 80% in the open Gulf of Mexico to zero in Hillsborough Bay.

Five major sources of turbidity were identified: (1) resuspended bottom sediment, present both naturally over shoals and caused artificially by dredging and other developmental activities, most important; (2) suspended phytoplankton ("seston") important locally, especially in Hillsborough Bay, where the pollutional nutrient input is excessive and promotes plankton blooms; (3) sewage outfalls and miscellaneous inputs related to urbanization; (4) river-borne tripton; and (5) surf-generated fine debris.

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