An opaque disc, typically white, used to gauge the transparency of water by measuring the depth—known as the Secchi depth—at which the disc ceases to be visible from the surface.‘Overall difference between species in use of Secchi depths varied by habitat type.’
- ‘Mean Secchi depths tended to be higher in 1996 than in 1997, but these differences also were not statistically significant.’
- ‘Temperature (in degrees Celsius) was measured at the surface and close to the bottom, and the Secchi depth was determined.’
- ‘Although light conditions expressed as Secchi depth differed during the later part of the summer, differences over the whole season were not significant.’
- ‘Further, on two dates we also measured Secchi depth and oxygen concentration in the epilimnion of each enclosure during midday.’
Early 20th century named after Angelo Secchi (1818–78), Italian astronomer.