algae are not just consumed directl

algae are not just consumed directly,they also excrete into the water nutritious organic substances including polysaccharides,complex organic nitrogenous matter,vitamins,proteins,enzymes,DNA,RNA,and phenolic compounds(bold and wynne,1985).some of the dissolved organic matter contributes to the water staining in near-shore habitats and in recirculating aquariums.in the natural environment some of the exudates aggregate to form large particles in the water column, part of the material known as "marine snow."this is besides the contribution by algae of particulate organic matter in the water column,generated from erosion and grazing.rates of exudation increase with photosynthesis during the light period and decrease in the dark(ragan and jensen,1979)and,as for corals with symbiotic zooxanthellae,a significant amount of the carbon budger for seaweeds may be lost(exuded)as dissolved organic carbon(hatcher et al.,1977).