Culture Studies of Halodule wrightii Aschers. Edaphic Requirements

Abstract

Growth rates of H. wrightii Aschers. were compared during laboratory culture on artificial sediments containing varying amounts of soluble sulfide and Fe, but similar amounts of N, P and Mn. Moderate levels of H2S (.apprx. 0.5 mM) and very low levels of soluble Fe (0.5-2.0 .mu.g/ml) in the sediment water correlated with maximal Halodule growth rates. Interstitial water-soluble Fe > 20 .mu.g/ml appeared to inhibit Halodule growth, possible by interfering with S metabolism or limiting the availability of P to the plants. Excess phosphate, but not Mn, added to the sediments containing low H2S levels counteracted some degree of Fe inhibition. Sediment H2S concentrations > 1 mM were also correlated with decreased growth rates, verifying that a poised level of H2S between 0.2-1.0 mM favored Halodule growth. The methodology described is proposed for laboratory culture studies of other seagrasses.