THE RADIOMETRIC DETERMINATION OF TOTAL PIGMENT AND SESTON AND ITS POTENTIAL USE IN SHELF SEAS

A total of 293 radiometric observations of subsurface reflectance and simultaneous measurements of pigment and seston provide the basis for improved algorithms relating surface properties to spectral reflectance R(λ). Without allowance for the effects of seston, total pigment concentration C (chlorophyll a + phaeopigment) for our entire data set fits an algorithm of the form C = aγ-b; γ = R(440 nm) R(550 nm) with constants a = -0·06 and b = 1·60. The effect of inorganic seston concentration, Σi, over the range 0 < Σi < 6 mg l-1, is to modify the exponent b such that it increases significantly according to b = 1·80 + 0·38 Σi. This result confirms the trend apparent in discrete values of b for case 1 and case 2 waters, but also implies that there may be advantages in a (physically more realistic) continuous representation. Σi is found to be related to the intensity of reflectance at 550 nm, but with a slope m which is controlled by the concentration of organic seston Σo through the relation m = 0·094 - 1·046 Σo. Owing to the highly variable nature of the organic component, Σo cannot at present be reliably determined from the radiometric data. Hence, the general problem of determining C, Σi and Σo from radiometer data in remote sensing and in situ applications cannot generally be solved without additional estimates of Σo. © 1990.