Rapid nutrient consumption and high respiration rate prevent anthropogenic nutrient accumulation in the northwestern Arabian (Persian) Gulf of Kuwait.

The northwestern Arabian/Persian Gulf of Kuwait is a distinguished shallow and landlocked marine environment where hydrography and biogeochemistry changes biannually due to unique climatic conditions. In recent years, this system suffered severe anthropogenic stress due to reduction in riverine discharges, rapid urbanization, dumping of domestic sewage and release of brine from desalination plants. However, it is not reflected in the accumulation of nutrients and chlorophyll in coastal waters except sporadic events of algal blooms. We present here, nutrient data (nitrate, nitrite, ammonium and phosphate) collected at three sites, roughly, at monthly intervals over more than a decade (2002 to 2015). None of the nutrients showed clear secular increasing trend in concentrations with time. In fact, at all 3 sites declining trends were oberved albeit with low slope values of -0.04, -0.01 and -0.45 µM y^-1. Large inter-annual variability were broadly corresponds to the fluctuations in the discharge from the Shatt-al-Arab River. Present levels of nitrate were found slightly higher (~1µM) than the available data from the 1970s (below detection limit) and probable phosphorus limitation as a consequence of excess nitrogen input particularly in summer/autumn season. Additional nutrient enrichment experiments conducted during late winter/spring and summer revealed rapid nitrate uptake and build-up of chlorophyll. Very high respiration rates were recorded in parallel incubation in dark reaching maximum of 5.34 ml O₂ l^-1d^-1 and averaging to 1.60±1.44 ml O₂ l^-1d^-1. Results obtained from this study suggest that rapid respiration of the photosynthesized organic matter prevents accumulation of both anthropogenic nutrients and phytoplankton biomass in this region.