CONCENTRATIONS OF N AND P IN FLOODWATER AND UPTAKE OF N-15 BY SPARTINA-ALTERNIFLORA IN OIL CONTAMINATED MESOCOSMS

Fertilization of salt marshes to enhance oil biodegradation may not be effective if nutrients in floodwater are rapidly removed by plants or adsorbed to sediments. Three N-15 labeled fertilizers and two commerc ial nitrogen (N) and phosphorus (P) slow-release fertilizers were appl ied at rates of 75-210 kg N ha(-1) with and without 40 kg ha(-1) of su pplemental P to oil-contaminated, flooded mesocosms growing Spartina a lterniflora phosphorus concentrations in floodwater ranged between 0.0 5 and 2.82 mu g P ml(-1) 39 days after P application. Urea and NO3- co ncentrations in floodwater were below detection limits by 2 weeks afte r N application, but NH4+ remained detectable for approximately 3 week s. Approximately 20% of N from urea and ammonium fertilizers was recov ered in shoots of Spartina, but only 7% from nitrate fertilizer was re covered. Frequent applications of fertilizers may be needed to maintai n desirable nutrient concentrations in floodwater for enhancing oil bi odegradation. Copyright (C) 1996 Elsevier Science Ltd.