The saltern lies about 500 m from the Mediterranean Sea in the north. It consists of a series of shallow ponds with depths of 0.5–1.5 m and surface areas varying from 70 to a few hundred ha (Figure 1). Seawater is pumped from the Suez Canal through an intake to a large pond (P1) where solar energy and wind combine and evaporation begins. The water volume is reduced and salinity levels gradually build up through consecutive evaporation ponds (P2–P3) and the production pond (P4). As the salinity increases, low-soluble salts precipitate

Roxadustat clinical trial as carbonates and sulphates. The saturated brine then passes through smaller ponds (P5, crystallizer ponds) where evaporation continues (Figure 2). Once the volume has been reduced to about 10% of the original, any furtherk concentration results in the deposition of sodium chloride. Five ponds with different salinities were sampled in summer (June 2010).

Water samples were collected 20 cm below the surface using a 2-L Van Dorn bottle. Water temperature, transparency and pH were measured immediately in situ after sampling using a mercury CP 868596 glass thermometer graduated in 0.1 °C, a Secchi disc and a portable pH meter (Model HI 9124) respectively. Salinity was estimated as total dissolved salts (TDS) according to APHA (1995). A well-mixed sample was passed through a glass fibre filter, after which the filtrate was evaporated to dryness in a weighed

dish, then dried to constant weight at 180 °C. The increase in dish weight represents the salt content [g l− 1]. The total weight of major ions generally Proteasome inhibitor constitutes over 99% of the total salinity (Wetzel & Likens 2000). Nitrates and phosphates were determined in filtered seawater using GF/C filters according to the methods described by Parsons et al. (1984). For phytoplankton examination, water samples were preserved immediately using Lugol’s iodine and concentrated by decanting. The algal count was conducted under an inverted microscope using Utermöhl’s method (Utermöhl 1958) and identified to genus or species level by consulting the works of Prescott (1951), Hendey (1964), Dodge (1982) and Komárek & Anagnostidis (2005). Pearson’s correlation coefficient was performed using the SPSS 17 software program to examine the potential relationships among physicochemical variables and phytoplankton diversity and density. Relations highly significant to the 0.05 level were noted. The waters of the Port Fouad saltworks were always clear, with the Secchi depth corresponding to the maximum depth of water due to the shallowness of the ponds (Table 1). The water of the shallower, more saline pond (P5, crystallizer pond) was warmer (29.3 °C) than that of the deeper, less saline pond (P1, 25.6 °C). The water salinity increased progressively throughout the series of interconnected ponds, giving a value of 340.