RAS-1984 — Page 209

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Y.H. CHEUNG, K.Y. TAI, S.W. TSAO AND L.B. THROWER

PART II: PRODUCTIVITY OF THE KEI WAI

This part is concerned with the sources of food for the economic produce of the kei wai and especially the importance of detritus to productivity.

Materials and Methods

Almost all of the work was done on kei wai No. 7, but a few measurements were made also in kei wai No. 8 (total area ca 20 ha.) and fresh-water fish pond No. 9 (ca 0.2 ha.)

a) Conditions in the kei wai

The following were measured at intervals of 4 weeks from 27 March 1978 to 17 February 1979:

(i) maximum and minimum air temperatures under the mangrove canopy beside kei wai No. 7 Zeal maximum/minimum thermometer left in place throughout.

(ii) air temperature at the time of each visit (“spot temperature”) as (i).

(iii) water temperature — Yellow Springs Instrument Co.

(iv) dissolved oxygen — Model 57 dissolved oxygen meter.

(v) pH of water — Corning Model 10 pH meter.

(vi) salinity of water — Mohr-Knudsen method.

(vii) phosphate content of water — molybdate-antimony reagent and ascorbic acid followed by spectrophotometry.

b) Primary productivity

(i) Phytoplankton was estimated by filtering 2-3 litres of freshly collected water through a layer of MgCO3 by suction.