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Nitrogen and Phosphorus Recycling by a Dominant Tropical Seagrass (Thalassia Testudinum) Across a Nutrient Gradient in Florida Bay

Authors: Rosch, Kara L.; Koch, Marguerite S.

Source: Bulletin of Marine Science, Volume 84, Number 1, January 2009 , pp. 1-24(24)

Publisher: University of Miami - Rosenstiel School of Marine and Atmospheric Science

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Abstract:

Nitrogen (N) and phosphorus (P) recycling by the dominant Atlantic/Caribbean seagrass, Thalassia testudinum Banks and Soland. ex Koenig, was investigated to further understand nutrient dynamics in seagrass-dominated tropical estuaries. Nutrient loss from leaves attached to short-shoots and subsequent decay rates of detached senescent leaves, roots, and rhizomes were determined across a nutrient gradient in Florida Bay. The greatest flux of nutrients occurred from leaves as they senesced on the short-shoot, and loss was higher at nutrient-rich (88% P; 51% N) compared to nutrient-poor (49% P; 25% N) sites. The close relationship between live leaf percent N and P decline (R2 = 0.91), high loss rates of P (max = 95%) and N (max = 86%), and the major loss of nutrients at leaf tips, indicate that seagrass live leaf nutrients, a large nutrient pool in the bay, are being turned over via decomposition and/or leaching, rather than internal plant resorption or decay. Detached senescent leaf decay constants (k = 33–129 × 10–4 d–1) were relatively low, and root and rhizome decay even slower (k = 23–66 × 10–4 d–1), thus detrital decomposition is a slow nutrient recycling process. In contrast, the rapid leaching of nutrients from attached leaves indicates that T. testudinum may serve as a sediment nutrient pump. Scaling to the ecosystem, and applying current nutrient budgets, T. testudinum leaf nutrient flux was estimated to contribute 209 and 4343 mt of P and N yr–1, accounting for ∼50% and ∼35% of the annual P and N inputs to Florida Bay, although further studies are required to validate these initial bay-wide estimates.

Document Type: Research Article

Publication date: January 1, 2009

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  • The Bulletin of Marine Science is dedicated to the dissemination of high quality research from the world's oceans. All aspects of marine science are treated by the Bulletin of Marine Science, including papers in marine biology, biological oceanography, fisheries, marine affairs, applied marine physics, marine geology and geophysics, marine and atmospheric chemistry, and meteorology and physical oceanography.
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