The effect of Zostera noltei recolonization on N and P fluxes at the sediment/water interface

Within the scope of an ongoing seagrass active restoration program at Ria de Aveiro, Portugal, the present work aimed at evaluating the recovery of Zostera noltei meadow nutrient regulation ecosystem function, by mediating Nitrogen and Phosphorus biogeochemical processes, and translated on the nutrient fluxes (PO₄-P, NO_x-N and NH₄-N) at the sediment/water interface. This plant-mediated process was evaluated seasonally at three sites (Bare bottom, Zostera noltei Transplant and Natural meadow) and at two tidal conditions which required two distinctive methodologies: (a) the low tide pools during ebb, and (b) flux chambers during high tide. Sediments were collected in situ and physicochemical parameters determined. At Zostera noltei transplanted areas, plant-mediated biogeochemical processes were found to reduce nutrient fluxes (both NH₄-N and PO₄-P) at the sediment/water interface, and its significance varied seasonally and along the tidal cycle. Furthermore, nutrient fluxes for both vegetated sites (Transplant and Natural) were similar, showcasing that the N and P biogeochemical processes and function were re-established no later than a year after transplantation.