RESPONSES OF BACTERIAL ASSEMBLAGES ON STANDING-DECAYING BLADES OF SMOOTH CORDGRASS TO ADDITIONS OF WATER AND NITROGEN

Plots of intermediate-height cordgrass (Spartina alterniflora) were fe rtilized with nitrogen, misted with freshwater, given both misting and N, or left untreated. Bacterial responses on standing-decaying leaf b lades were measured as changes in epiphytic mass, rates of shedding of bacterial cells into seawater, and rates of net growth on blades. Epi phytic mass rose with time, and it did so 6-fold more sharply for the combination of fertilization and misting than for control. Since the s ediment surface would offer higher N and water availability, this may indicate that movement of leaf material to marsh sediments would stron gly favor bacterial activity. Net growth on aerially incubated (15 h), wet blades as percentage of standing bacterial mass was unchanging wi th duration of decay period, but was affected by treatment (about 0 to +5% h(-1) for misted treatments, +15% h(-1) for unmisted treatments). Faster growth on newly wetted, unmisted blades may have been due to r elease of cells from growth limitation by desiccation. Plot treatment did not affect specific rate of bacterial shedding (about 8% of standi ng bacterial epiphytic mass during one h of submergence at 4 weeks, an d 149% h(-1) at 12 weeks). It may be that during high spring tides, ba cterial shedding from standing-decaying blades could provide numbers o f new cells in the water column near to or greater than those provided by division of bacterioplanktonic cells.