Analysis of the spatio-temporal variability of seawater quality in the southeastern Arabian Gulf Nahla Mezhoud ⁎, Marouane Temimi, Jun Zhao, Maryam Rashed Al Shehhi, Hosni Ghedira Institute Center for Water and Environment (iWATER), Masdar Institute of Science and Technology, Masdar City, PO Box 54224, Abu Dhabi, United Arab Emirates abstract article info Article history: Received 19 October 2015 Received in revised form 7 March 2016 Accepted 9 March 2016 Available online xxxx In this study, seawater quality measurements, including salinity, sea surface temperature (SST), chlorophyll-a (Chl-a), Secchi disk depth (SDD), pH, and dissolved oxygen (DO), were made from June 2013 to November 2014 at 52 stations in the southeastern Arabian Gulf. Significant variability was noticed for all collected parame- ters. Salinity showed a decreasing trend, and Chl-a, DO, pH, and SDD demonstrated increasing trends from shal- low onshore stations to deep offshore ones, which could be attributed to variations of ocean circulation and meteorological conditions from onshore to offshore waters, and the likely effects of desalination plants along the coast. Salinity and temperature were high in summer and low in winter while Chl-a, SDD, pH, and DO indi- cated an opposite trend. The CTD profiles showed vertically well-mixed structures. Qualitative analysis of phyto- plankton showed a high diversity of species without anomalous species found except in Ras Al Khaimah stations where diatoms were the dominating ones. © 2016 Elsevier Ltd. All rights reserved. Keywords: United Arab Emirates Water quality Phytoplankton species Seasonality 1. Introduction The Arabian Gulf (AG) is located in an arid region in the Middle East and is a marginal and semi-enclosed sea off the Indian Ocean (Price, 1993). The AG widest section spans over 340 km between the coasts of the United Arab Emirates (UAE) and Iran. Its bathymetry is relatively shallow with an average depth of 36 m. It is asymmetric along its axis with a deeper zone close to the Iranian coast and a broad and shallower shelf off the UAE coast (Elhakeem et al., 2015). It is surrounded by Saudi Arabia, Kuwait, Iraq, Iran, Oman, UAE, Qatar, and Bahrain. It is very essential for countries surrounding it. The scarcity of fresh water re- sources in the region due to the prevailing arid climate leads to substan- tial reliance on desalination for potable water supply. For example, 90% of the domestic and industrial water supply in the UAE is from desalina- tion (Elshorbagy and Elhakeem, 2012). However, marine pollutions, such as oil spills and algal blooms, have been frequently reported in the AG (Al-Shehhi et al., 2014; Foster et al., 2011; Glibert et al., 2002; Heil et al., 2001; Moradi and Kabiri, 2012; Richlen et al., 2010; Subba Rao and Al-Yamani, 1998; Zhao and Ghedira, 2014; Zhao et al., 2014; Zhao et al., 2015a, 2015b). In addition, the fast development of coastal cities and the alteration of coastlines augment the vulnerability of the AG. Therefore, it is essential to study the spatial and temporal variability of seawater quality in the AG as a first step towards developing a full understanding of harmful algal bloom (HAB) occurrences and behaviors and other disturbances that may impact marine ecosystems. The characterization of seawater quality in the AG can rely on one or a combination of the following three sources, namely, in situ observa- tions, modeling techniques, and satellite remote sensing imagery. The latter can only provide information on seawater conditions during cloud-free and clear-atmosphere observations which are not met fre- quently over the AG given the abundant dust sources around it (Zhao et al., 2015b). In addition, the high evaporation rate in the AG raises water vapor contents in the atmosphere and reduces the number of valid sea surface observations from space. Also, satellite data provide integrated information on the surface and near-surface layers but not the full vertical profile. Modeling techniques are computationally demanding and require an extensive amount of in situ observations and ancillary data for their initialization and verification. The limited number of reliable field campaigns and the scarcity of in situ data in the study area reduced the potential of numerical models for the characterization of seawater in the AG. Recently, Al-Azhar et al. (2016) used the dataset from a field campaign in 1992 by Reynolds (1993) to verify their model. So, additional field sampling is very important to develop a full understanding of seawater quality and its variability in the AG. Such effort serves the use of satellite imagery and numerical modeling as well by providing needed ground truth observations for the verification of developed products. Studies related to in situ seawater quality monitoring (SWQM) have been conducted in different parts of the AG. Al-Mutairi et al. (2014) assessed the spatial and temporal variations of water quality between 2009 and 2011 from six stations in the Kuwait Bay. Shriadah and AI-Ghais (1999) studied the hydrographic conditions and nutrient levels from October 1993 to September 1994 at 24 stations in the UAE waters. Moradi and Kabiri (2012) reported the variations of Marine Pollution Bulletin xxx (2016) xxx–xxx ⁎ Corresponding author. E-mail address: nmezhoud@masdar.ac.ae (N. Mezhoud). MPB-07554; No of Pages 12 http://dx.doi.org/10.1016/j.marpolbul.2016.03.016 0025-326X/© 2016 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Please cite this article as: Mezhoud, N., et al., Analysis of the spatio-temporal variability of seawater quality in the southeastern Arabian Gulf, Ma- rine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.03.016