DECOMPOSITION OF HUDSON ESTUARY MACROPHYTES - PHOTOSYNTHETIC PIGMENT TRANSFORMATIONS AND DECAY CONSTANTS

Plant pigment decay constants were determined for four macrophytes collected from the Hudson Estuary. Typha angustifolia and Scirpus fluviatilis were used as representatives of emergent aquatic vegetation (EAV), and Potamogeton sp. and Vallisneria americana were used to represent submerged aquatic vegetation (SAV). Litter bags were maintained in an environmental chamber in the dark for 104 d. The fastest rate of total mass loss was in the SAV V. americana and slowest in the EAV T. angustifolia. Changes in carotenoid and chloropigment concentration resulting from microbial and meiofaunal heterotrophy in each of the macrophytes were quantified using reverse-phase, high-performance liquid chromatography (RP-HPLC) techniques. Chlorophyll c and the carotenoid, fucoxanthin, provided useful biomakers in determining the presence of epiphytic diatom growth, which only occurred on the SAV. The highest concentrations of phaeophorbide a, commonly used as an indication of metazoan grazing, were found in the SAV V. americana. Low concentrations of phaeophorbide a in the SAV Potamogeton sp. indicate inefficient use of this SAV by meiofaunal grazers. Lutein decayed slower than all other carotenoids in both EAV and SAV. Microcosm studies such as this are necessary to further understand the mechanisms and kinetics of photosynthetic pigment transformations in natural systems.