A preliminary study on benthic nutrient exchange across sediment-water interfaces in a shallow marine protected area of the Northwestern Arabian Gulf.

Sedimentary processes are expected to play a crucial role in macronutrient cycling of the shallow Arabian Gulf. To investigate this aspect, sediment cores were collected from the shallow intertidal and subtidal expanses of the first Marine Protected Area (MPA) of Kuwait in the Northwestern Arabian Gulf (NAG). Porewater nutrient profiling and whole core incubation experiments were conducted to measure the nutrient fluxes, both with and without the addition of the nitrification inhibitor allylthiourea (ATU). The porewater data confirmed the potential of sediments to host multiple aerobic and anaerobic pathways of nutrient regeneration. The average (±SD) of net nutrient fluxes from several incubation experiments indicated that ammonium (NH) predominantly fluxed out of the sediment (3.81 ± 2.53 mmol m d), followed by SiO (3.07 ± 1.21 mmol m d). In contrast, the average PO flux was minimal, at only 0.06 ± 0.05 mmol m d. Fluxes of NO (ranged from 0.07 ± 0.005 to 1.16 ± 0.35 mmol m d) and NO (0.03 ± 0.003 to 0.71 ± 0.21 mmol m d) were moderate, which either reduced or reversed in the presence of ATU (-0.001 ± 0.0001 to 0.01 ± 0.0001 mmol m d and -0.001 ± 0.0003 to 0.006 ± 0.001 mmol m d for NO and NO respectively). Thus, this study provides preliminary experimental evidence that nitrification can act as a source of NO and NO as well as contribute towards the relatively high concentrations of NO (>1 in the gulf waters.