EFFECT OF INCREASED WATER DEPTH ON GROWTH OF A COMMON PERENNIAL FRESH-WATER-INTERMEDIATE MARSH SPECIES IN COASTAL LOUISIANA

The response of Sagittaria lancifolia to increased water depths of 7.5 and 15 cm was examined in this field study. Water-depth treatments we re achieved by digging sods containing one or two individual plants or ramets of S. lancifolia from the marsh, removing sediment from the re sulting hole, and replacing the sods in their original location at the appropriate lower elevation. Plants subjected to increased water dept h of 15 cm had higher mean and maximum leaf heights than disturbed con trol plants. Aboveground biomass was not affected by water-depth treat ment; however, 15-cm treatment plants had reduced root biomass and low ered leaf tissue concentrations of Ca, Cu, Fe, Mg, and Zn. Marsh sods at 15 cm below the marsh surface had the lowest redox potential and hi ghest interstitial water sulfide concentration, indicating that this t reatment created the most stressful belowground environment. Sagittari a lancifolia plants responded to the level of stress imposed by the ex perimental conditions with an altered growth form of increased leaf he ight.