Chapter 20 Northern Gulf Marine Biodiversity in Relevance to the River Discharge Faiza Al-Yamani, Igor Polikarpov, and Maria Saburova Abstract This chapter summarizes the results of research studies, which addressed the peculiarity of the estuarine and northern Arabian Gulf marine environment and the influence of the Shatt Al-Arab River and its associated marshes on the ocean- ography and biodiversity of the northern Gulf. The findings of the studies indicated that the northern waters of Kuwait, which are impacted by the Shatt Al-Arab River discharge, displayed lower salinity, higher nitrate concentration, higher chlorophyll- a, and higher sedimentation. The biodiversity of the northern waters of the Gulf also was significantly distinguished from the adjacent area away from the influence of the river flow. Discharge of the Shatt Al-Arab is considered to be a dominating driver of the northern Gulf ’s ecology and largely responsible for the primary and secondary productivity of Kuwait’s waters. Long-term reduction in river discharge due to man-made alterations (damming and diversion of rivers) impacted the oceano- graphic characteristics of Kuwait’s waters with implication to fisheries resources. Management of Shatt Al-Arab River discharge into the Gulf requires cooperation among the riparian countries and downstream countries like Kuwait to preserve the productivity, biodiversity, and uniqueness of the northern Gulf ecosystems. Long- term monitoring and assessment as well as joint research programs involving scientists from the three concerned countries, Kuwait, Iraq, and Iran, are needed. Keywords Aquatic biodiversity · Salinity changes · Kuwait · Mesopotamian marshes · Plankton · Benthos · Shatt Al-Arab delta F. Al-Yamani · I. Polikarpov (*) · M. Saburova Ecosystem-based Management of Marine Resources Program, Kuwait Institute for Scientific Research, Salmiya, Kuwait © Springer Nature Switzerland AG 2021 L. A. Jawad (ed.), Southern Iraq’s Marshes, Coastal Research Library 36, https://doi.org/10.1007/978-3-030-66238-7_20 379