DEPTH-DEPENDENCY OF THE AGAROPHYTE RED ALGA Gracilaria corticata J. AGARDH FOR AGAR YIELD AND QUALITY DURING ITS GROWING SEASON

Abstract

The impacts of two depth ranges on the rhodophyte Gracilaria corticata for agar yield and quality were determined during its growing season (December to March) at intertidal waters. Average 4-month agar at 2-3 m and 5-6 m were 34 ±0.04% and 42 ±0.05%, respectively. The lowest (30 ±2.89%) and highest (51 ±4.16%) agar yields, respectively, were estimated in December at 2-3 m and in January at 5-6 m. At 2-3 m, the 4-month averages were not significantly different (P>0.05). G. corticata from a depth of 2-3 m yielded the strongest (30.64 ±1.49 g cm−2) agar gel in December, and the alga sampled at 5-6 m in January revealed the lowest agar strength (7.94 ±0.38 g cm−2). Agar lightness (L) ranged from lowest (59.6 ±3.85) at 2-3 m in December to greatest (86.8 ±3.11) at 5-6 m in February. Agar yellowish factor (a) was highest (11.6 ±3.21) at 2-3 m in December and lowest (4.8 ±1.64) at 5-6 m in February. Agar reddish factor (b) was highest (48 ±2.24) in March and lowest (38.8 ±1.30) in December at a depth of 2-3 m. G. corticata growing at relatively deeper intertidal zone yields more quality agar, and December and late winter are the best times to obtain a more rigid and enhanced agar gel.