The concentration of chlorophylls a and c in the south-east Indian Ocean

Abstract

Samples were collected in 1959-62, usually at 0, 25, 50, 75, 100, and 150 m, in the region between 90 and 140º E., and 10º N. and 50ºS. At 0 m (and 150 m) the regional average for chlorophyll a was 0.08 (and 0.09) µp/l in summer and 0.12 (and 0.09) µp/l in winter; for chlorophyll c the values were 0.17 (and 0.21) µp/l in summer and 0.21 (and 0.21) µp/l in winter. Most samples had chlorophyll c/a ratios between 1 and 2. The average amount of chlorophyll a in the water column to 150 m was 15 mg/m² in summer and 23 in winter; for chlorophyll c the values were 29 mg/m² in both summer and winter. At most stations the maximum amounts of chlorophyll were at 75 m, often near density and temperature discontinuities. At 75 m the regional average for chlorophyll a was 0.14 µpll in summer and 0.19 in winter; for chlorophyll c the values were 0.35 and 0.24. The results of the present and similar work show that the amounts of the chlorophylls in the water column under 1 m² are similar for all oceans.