Release of metals by the leaves of the salt marsh grasses Spartina alterniflora and Phragmites australis

The perennial grass Spartina alterniflora, common to salt marshes of easter n North America, is known to accumulate metals from marsh sediment and rele ase them into the environment. One pathway by which Spartina alterniflora r eleases metals is through the excretion of metal-containing salts produced by leaf salt glands. We examined the differential release of metals by Spar tina alterniflora and the invasive perennial grass Phragmites australis in an urban marsh ecosystem. Leaching rates were measured by cleaning residues off leaf surfaces under field and controlled laboratory conditions. Leaf r esidues and leaf tissue were analysed for copper, chromium, lead and zinc b y atomic absorption spectrophotometry. Spartina alterniflora was found to r elease significantly more metal through leaf tissue than Phragmites austral is, under both field and laboratory situations. Spartina alterniflora was a lso found to accumulate significantly more chromium and lead in leaves than Phragmites australis. Therefore, Spartina alterniflora can release larger quantities of metals into the marsh environment than Phragmites australis, through both excretion and leaf deposition. (C) 2000 Academic Press.