Underwater radiant energy absorbed by phytoplankton, detritus, dissolved organic matter, and pure water

Abstract

The spectral irradiance distribution at five stations on lakes and at sea was measured with a portable underwater spectral irradiance meter. Chlorophyll a concentration and the absorption coefficient of the water were concurrently measured. From measured spectral irradiance distributions, radiant energy absorbed per unit volume was computed. At these stations, the effect of upward irradiance on total quanta absorbed by the water was negligibly small for all layers. The relative contributions of phytoplankton, detritus, dissolved organic matter, and pure water to the total absorbed quanta were also computed by taking into consideration the spectral dependency of each component: the contribution of quanta absorbed by phytoplankton was about 3-10% in clear water and about 30-40% in the plankton-rich water.

Variação Na Qualidade Óptica Da Água Do Sistema Rio-Reservatório Da Usina Hidrelétrica De Tucuruí/Pa

“…Vários estudos neste campo foram feitos, destacando-se Grobbelaar & Stegmann (1976), Junk et al (1981, Ribeiro (1983), Kishino et al (1984). 0 material em suspensão também preocupa no que tange ao assoreamento contínuo do lago formado.…”

Effects of solar ultraviolet radiation on biogeochemical dynamics in aquatic environments : report of a workshop, Marine Biological Laboratory, Woods Hole, Massachusetts, October 23-26, 1989

“…In several studies, using a number of approaches, the absorption spectra of particulate material from natural waters have been partitioned into two components: 1) the absorption by phytoplankton pigments, and 2) the absorption by what has been classified as "organic detritus" (e.g., Kiefer and SooHoo, 1982;Kishino et aL., 1984;Maske and Haardt, 1987). Spectrally, these two operational classes of organic chromophoresare quite different.…”

A two‐component description of spectral absorption by marine particles

“…Measurement of the spectral absorption coefficient for suspended particles in seawater has provided useful information since its introduction by Yentsch (1960), who has shown that this measurement can be quickly made using samples concentrated on glassfiber filters and a scanning spectrophotometer (see also Kiefer and SooHoo 1982;Kishino et al 1985;Mitchell and Kiefer 1988). In this technique, the particle absorption coefficient, a,(X) (units given in list of symbols), is computed from the difference between the optical density of a filter that contains suspended particles and a blank filter.…”

“…Absorption by materials other than phytoplankton (e.g. detritus, bacteria, and dis-1500 solved substances) can also be variable, and there is as yet much discussion concerning the identity and origin of these materials (Kishino et al 1984;Smith and Baker 1978).…”

“…The absorption coefficient can be described as a combination of the individual absorbances from three categories: water, suspended particles, and dissolved materials, and the contribution to the total absorption coefficient by the latter is quite variable (Austin and Petzold 1986;Kishino et al 1984;Smith and Baker 198 1). Phytoplankton absorption coefficients are subject to variability due to changes in crop size as well as cellular pigment concentration and composition (Yentsch 1960;Mitchell and Kiefer 1988).…”