Photosynthesis in the Ocean as a Function of Light Intensity1

Abstract

Photosynthesis was measured in 14 species of marine plankton algae in relation to light intensites within the entire range to which natural phytoplankton populations may be exposed. A mean curve was constructed showing relative photosynthesis in marine phytoplankton as related to light intensity. From this curve and surface radiation data, relative values for photosynthesis were determined throughout the day at the surface and at depths in the ocean at which the surface intensity is reduced by given amounts. Integration of these values over the entire day gave values for daily relative photosynthesis at each depth considered, and integration of the daily values with depth resulted in a single figure for daily relative photosynthesis beneath a unit of sea surface.An empirically derived relationship was discovered between daily surface radiation and daily relative photosynthesis within the water column. From this relationship the effect of light intensity upon photosynthesis throughout the year at a temperate latitude was demonstrated.A preliminary method is described for estimating absolute daily photosynthesis beneath a square meter of sea surface from measurement of (1) photosynthesis of a sample of the population at light saturation, (2) the extinction coefficient of light in the water, and (3) the daily surface radiation.From an estimate of the ratio of photosynthesis to respiration at light saturation, the daily ratio P:R for the entire population is calculated. It is shown that phytoplankton populations cannot photosynthesize sufficiently to compensate for their own respiration during periods of low solar radiation, as may occur in the winter months at temperate or northern latitudes.

Biological production in the Indian Ocean upwelling zones –Part 1: refined estimation via the use of a variable compensation depth in ocean carbon models

“…Observations show that the primary production reduces rapidly to 20 % or less of the surface value below a threshold of 10 W m −2 (Parsons et al, 1984;Ryther, 1956;Sarmiento and Gruber, 2006). Moreover higher ocean temperatures (those in the tropics) enhance the respiration rates, resulting in high compensation irradiance (Ryther, 1956;Parsons et al, 1984;Lopez-Urrutia et al, 2006;Regaudix-de-Gioux and Duarte, 2010). A study by Regaudix-de-Gioux and Duarte (2010) reported the mean value of compensation irradiance over the Arabian Sea as 0.4 ± 0.2 mol photon m −2 day −1 , which is close to 10 W m −2 day −1 .…”

Microplankton composition, production and upwelling dynamics in Sagres (SW Portugal) during summer of 2001

“…This can be interpreted as a light limitation of the production rate (e.g. Ryther, 1956;Kirk, 1994). Cloud coverage can affect rates of production by a factor of up to 4.5 (Riegman and Colijn, 1991).…”

Variation with Stream Order in Species Composition, Diversity, Biomass, and Chlorophyll of Periphyton in Otter Creek, Oklahoma

“…Because chlorophyll ~· roughly approximates the rate of photosynthesis, it has been used as a measure of productivity (Ryther 1956, Waters 1961, Yount 1956. Several studies have shown a strong positive correlation between chlorophyll content and biomass (McConnell andSigl,er 1959, Grzenda andBrehmer 1960).…”