Effects of Organic Matter Additions to Sediment on the Growth of Hydrilla Verticillata

Abstract : Sediment organic water can substantially inhibit the growth of Hydrilla. Other submersed species are similarly affected (Barko and Smart 1983). The inhibitory property of sediment organic matter here was associated either directly or indirectly with high concentrations of soluble organic compounds imparted to the interstitial water. Sediments amended by additions of refractory organic matter possessed macrophyte growth-inhibiting properties for a longer period than those receiving additions of labile organic matter. Thus, the extent of macrophyte growth inhibition appears to be determined by the type as well as the amount of organic matter incorporated into the sediment. Macrophytes modify the sediment environment through both their passive reception of allochthonous materials and their direct contribution of autochthonous primary production to the sediment (Wetzel 1979; Carpenter 1981). It is intriguing to speculate that the development of unfavorable changes in sediment chemistry, associated with the presence of highly productive species such as Hydrilla, may contribute to the decline of such species. In this connection, the influence of sediment composition on the growth and distribution of rooted macrophytes, with emphasis on organic properties, deserves continued investigative attention.