The invention pertains to a method for synthesizing a product of interest by culturing a microalgal cell obtained from a subterranean habitat for producing the product of interest. The microalgal cell obtained from a subterranean habitat can be cultured in the dark, in light, in low nutrition, or nutrient rich conditions for at least a portion of production cycle. A combination of these conditions can be used to specifically manipulate a microalgal cell culture to produce a product of interest. The product of interest can be a water-soluble carotenoid, for example, a water-soluble carotenoid produced by culturing an algae belonging to the genus Haematococcus or a capsular exopolysaccharide produced by culturing an algae belonging to the genus Parachlorella. Compositions containing the water-soluble carotenoid, for example, as sunscreen and compositions containing the exopolysaccharide, for example, as moisturizing cream are also described.