Heterotrophic consumption may mask increasing primary production fuelled by anthropogenic nutrient loading in the northern Arabian/Persian Gulf.

Monthly measurements of nitrate, nitrite, ammonium and phosphate at three stations off Kuwait during 2002-2015 revealed considerable inter-annual variability, broadly corresponding to fluctuations in the Shatt-al-Arab River discharge, but a lack of secular increasing trend. Nutrient enrichment experiments during two seasons revealed nitrate uptake, chlorophyll build-up and growth of micro-phytoplankton, even in the presence of ammonium, provided the availability of phosphate. Primary production was mostly nitrogen limited, but anthropogenic nitrogen supply may eventually make it phosphorus limited, especially in summer and in the open Gulf. Anthropogenic nutrient inputs appear to have enhanced biological productivity of the northern Gulf, but heterotrophic consumption, indicated by high respiration rates, probably prevented accumulation of phytoplankton biomass, accounting for the observed lack of chlorophyll increase over the past three decades. Consequently high total organic carbon and emerging hypoxia in the Gulf may lead to expansion/intensification of the oxygen minimum zone of the Arabian Sea.

Environmental characterization of a semiarid hyper saline system based on dissolved trace metal-macronutrient synergy: A multivariate spatio-temporal approach.

Trace metals and macronutrients play key roles in marine biogeochemical processes. Despite their higher availability, no reliable information is available on their ecological role in the hypersaline waters of NW Arabian Gulf. The present study identifies their synergistic effect on environmental characteristics and autotrophic biomass in the shallow coastal and offshore waters, off Kuwait on a seasonal basis. Surface water samples collected along four predefined transects were analyzed for physico-chemical and biological variables during summer (n=27) and winter (n=27) seasons. Multivariate analyses revealed clear spatial and seasonal trends, and identified the best suit of environmental variables responsible for the seasonal variability in phytoplankton biomass. Using statistically derived supply to demand ratios, carbon-trace metal stoichiometry, and bioavailability of trace metals, we propose possible growth regulating factors for phytoplankton on a seasonal basis in the NW Arabian Gulf, off Kuwait. This is the first report on trace metals from the entire Arabian Gulf, using clean techniques and multivariate statistical approach.