Early drivers of Black Mangrove ( Avicennia germinans ) leaf litter decomposition in the water column

Abstract

Sequestration of carbon and nutrients, and sustained productivity of estuaries depend on organic turnover and nutrient remineralization. Decomposition of abundant plant material produced by mangroves and other macrophytes in estuaries occurs in both the sediments and the water column. Early and intense processing could be more common in the water. In a previous study, in situ decomposition rates of Black Mangrove (Avicennia germinans) leaf litter suspended in the water column differed among four estuaries in south Texas with moderate differences in salinity, water temperature, available nitrogen (N), and tidal flow. A series of microcosm experiments were conducted to determine the influence, within observed ranges in the estuaries, of these water variables on mass loss of mangrove leaf litter over 60 days. High salinity (66 psu) delayed decomposition, but low temperature (20°C) was a retardant at lower salinities (20–43 psu). Water turbulence greatly accelerated mass loss, whereas N additions and the presence of sediments had minimal effects. The faster decomposition observed in the estuaries compared to the microcosms may be explained by the synergistic effect of these and other environmental factors.