EFFECTS OF NATURAL DISSOLVED ORGANIC-MATTER ON MUCILAGINOUS MATRICES OF BIOFILM COMMUNITIES

We evaluated experimentally the effects of dissolved organic carbon (D OG) derived from leachates of decomposing emergent macrophytes (Typha latifolia) on mucilage development in periphyton communities. Several techniques were used to quantify mucilage development by natural perip hyton communities grown on glass fiber filters and on sand in a define d culture medium with and without exposure to humic acid fractions of the leachate (up to 20 mg C L-1): (a) direct examination by cryogenic scanning electron microscopy (SEM), (b) application of a cationic copp er-containing dye, Alcian Blue 8GX, which binds to the glycosaminoglyc ans in the mucilage, and determination of the relative quantity of cop per retained by the community by energy dispersive X-ray microanalyses , and (c) amounts of dye removed from solution by spectrophotometric a nalyses. Multiple experiments showed that DOG-treated communities cont ained 10 to 57 % less mucilage than untreated controls, and suggested that DOC in littoral and wetland environments can act as an important physical determinant of structural and metabolic attributes of periphy ton.