Photosynthesis, respiration and exudation of organic matter in three common benthic marine macro-algae Chaetomorpha linum (Mull.) kutz., Hypnea museiformis (Wulfen) Lamouroux and Padim gymnoipora OLxKz.) Vickers were studied. Net photosynthetic rates of 3.46 mg C. linum for 3.89 mg C^g-1 dry wt.^h-1 for H.musciformis and 3.25mg C^g-1 dry wt.^h-1 for P.gymnospora Were observed. All the three algae excreted extracellular organic matter both in light and dark. The exudation of carbon in the dark ranged from 33 % to 44% of that during photosynthesis (light). The loss of fixed carbon due to exudation in the light was greater than that due to respiration in all three algae. The estimated daily organic matter flux (g C m^-2 d^-1) by these algae were gross production 4.4, net production 2.7, exudation 1.4, respiration 1.3 and assimilation 1.7. The excreted organic nitrogen and phosphorus fractions were very less compared to carbon.