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SUBMERGED MACROPHYTE EFFECTS ON NUTRIENT EXCHANGES IN RIVERINE SEDIMENTS
Wigand, C, M. Finn, S. Findlay, AND D. Fischer. SUBMERGED MACROPHYTE EFFECTS ON NUTRIENT EXCHANGES IN RIVERINE SEDIMENTS. ESTUARIES 24(3):398-406, (2001).
Submersed macrophytes are important in nutrient cycling in marine and lacustrine systems, although their role in nutrient exchange in tidally-influenced riverine systems is not well studied. In the laboratory, plants significantly lowered porewater nutrient pools of riverine sediments compared with bare controls. Deep-rooted Vallisnaria americana lowered the porewater nutrients to a greater extent than the shallow-rooted Potamogeton pectinatus. V. americana showed significantly higher tissue nutrient content (N in roots, P in leaves) than P. pectinatus. Porewater nutrients in the river increased from spring to summer (1995) when vegetation was at its peak (for porewater PO4- P, p < 0.05). In 1996, porewater nutrients were higher during peak plant biomass in the summer than in the fall (for porewater PO4- P, p < 0.05). In the summer the summer (1995) vegetated patches had significantly greater porewater PO4- P than bare patches. We hypothesize that the concentrating of particulates in riverine grassbeds and subsequent microbial processing may provide an indirect source of nutrients for submersed macrophytes. In tidally-influenced riverine systems, biological mechanisms such as root uptake of nutrients and lateral oxygen release may be masked by the interaction of physical forces (i.e., tides, currents) with the structure of the grassbeds.