Phytoplankton ecology in the Southern Benguela current. II. Carbon assimilation patterns

• Published in: Journal of experimental marine biology and ecology 1982-01, Vol.63 (3), p.229-237
• Main Author: Barlow, R.G.
• Format: Article
• Language: English
• Subjects: Marine
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/0022-0981(82)90180-0

The patterns of carbon assimilation into the major end-products of phytoplankton photosynthesis were studied in the Southern Benguela current during the summer of 1979–1980 using [ 14C]bicarbonate as a tracer. Greater activity was measured in the polysaccharide (TCA-soluble) fraction in aged upwelled water (Type 3) than in maturing upwelled water (Type 2) at both high and low light intensities. Conversely, a greater proportion of the label was incorporated into the protein (TCA-insoluble) fraction in maturing than in aged upwelled water. An approximately equal distribution of the label between polysaccharide and protein at the 50% light intensity was recorded in freshly upwelled water (Type 1), but at the 1% intensity greater activity was detected in the ethanol-soluble fraction. In ageing upwelled water (Types 2 and 3) more carbon-14 was incorporated into polysaccharide at the 50% light intensity than at the 1% intensity, but the percent incorporation was greater in Type 3 water when low nitrate concentrations prevailed. In this ageing water radioactivity in the protein fraction was greater at the 1% intensity than at 50% intensity.