FOLIAR RELEASE OF SOLUBLE REACTIVE PHOSPHORUS FROM SPARTINA-ALTERNIFLORA IN A GEORGIA (USA) SALT-MARSH

Foliar release of soluble reactive phosphorus (SRP) from live shoots of Spartina alterniflora (Loisel.) was investigated in a Georgia (USA) salt marsh. Average foliar SRP release rates varied from undetectable to 7.5 mug P (g dry wt)-1 h-1 with values from individual plants as high as 61.7 mug P (g dry wt)-1 h-1. Release rates of SRP generally exhibited little diel variation and were highest in midsummer. Estimates of extrafoliar SRP accumulated on leaf surfaces varied from < 1 to 41 mug P (g dry wt leaf)-1 and 0.8 to 1.7 Mg p m-2 normalized to marsh area. Time course experiments revealed that SRP release was a 2-step process with a rapid solubilization of extrafoliar SRP and a constant release thereafter. Releases of SRP from creekbank stands of S. alterniflora during tidal submergence were estimated to be 3.1 to 8.2 Mg p M-2 d-1, with annual releases of 1.7 g P m-2 yr-1. Foliar releases of SRP from the live plants are equivalent to 60 % of the annual production of particulate phosphorus as S. alterniflora detritus reported from Georgia salt marshes.