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The impacts of different CO 2 concentrations on the growth, physiology and ultrastructure of noncalcifying microalga Chaetoceros gracilis F.Schu¨tt (Diatom) were studied. We incubated Ch. gracilis under different CO 2 concentrations, preindustrial and current ambient atmospheric concentrations (285 and 385 latm, respectively) or predicted year-2100 CO 2 levels (550, 750 and 1050 latm) in continuous culture conditions. The growth of Ch. gracilis measured as cell number was decreased by increasing the pCO 2 concentration from nowadays concentration (385 latm) to 1050 latm. The lowest percentage changes of oxidizable organic matter, nitrite, nitrate, phosphate and silicate were recorded at a higher pCO 2 (1050 latm), and this is in consistence with the lowest recorded cell number indicating unsuitable conditions for the growth of Ch. gracilis. The minimum cell numbers obtained at higher levels of CO 2 clearly demonstrate that, low improvement occurred when the carbon level was raised. This was confirmed by a highly negative correlation between cell number and carbon dioxide partial pressure (r = À0.742, p 6 0.05). On the other hand, highest growth rate at pCO 2 = 385 latm was also confirmed by the maximum uptake of nutrient salts (NO 3 = 68.96 lmol.l À1 , PO 4 = 29.75 lmol.l À1 , Si 2 O 3 = 36.99 lmol.l À1 ). Total protein, carbohydrate and lipid composition showed significant differences (p 6 0.05) at different carbon dioxide concentrations during the exponential growth phase (day 8). Transmission Electron Microscopy of Ch. gracilis showed enlargement of the cell, chloroplast damage, disorganization and disintegration of thylakoid membranes; cell lysis occurs at a higher CO 2 concentration (1050 latm). It is concluded from this regression equation and from the results that the growth of Ch. gracilis is expected to decrease by increasing pCO 2 and increasing ocean acidification.

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In an attempt to evaluate the environmental quality of the Egyptian Mediterranean Sea from El-Dabaa to El-Saloum, environmental parameters as well as amino acids, petroleum hydrocarbons, pesticides and PCBs have been studied in water and sediment samples from seven different locations during the year 2014. Spatial and temporal fluctuations as well as statistical analysis between the analyzed variables were examined. The results demonstrated a wide range of water temperature (13.50-29.00°C), slightly narrow fluctuations in salinity (37.20-38.78), and welloxygenated seawaters (6.40-8.96 mg O 2 /l), relatively low amounts of oxidizable organic matter (0.10-1.60 mg O 2 /l) and the seawater was slightly alkaline (pH range 8.04-8.63). Nutrient characteristics sustained the levels up to 2.45, 5.42, 5.40, 0.28 and 5.36 µM for reactive phosphates, reactive silicates, ammonium, nitrite and nitrate, respectively. These obtained results signified that water quality from El-Dabaa to El-Saloum is good; within the permissible limits in the majority of monitoring sites, and all stations were generally between Oligotrophic and mesotrophic states, characterized by a relatively low to medium level of nutrients. Furthermore, seawater from the most sites did not show any levels of pesticides, PCBs and petroleum hydrocarbons. These levels, if any, may have been much lower than the detection limit for the compounds analyzed. In marine sediments, the concentrations of amino acids demonstrated a range of 1884.5-19569.6 µM, while pesticides, PCBs, and petroleum hydrocarbons were below detection limit to 3086, 120, 145 ng/g; respectively. These results are much lower in sediment of the western part of the Egyptian Mediterranean coast compared to other sites and also much lower than permissible levels given by National Academy of Sciences and National Academy of Engineering. However, The Egyptian marine environment along the Mediterranean Coast has been subjected to a substantial increase since the last decades of pollution due to a great number of industrial, agricultural, commercial and domestic waste effluents and emissions as well as hazardous substances (Emara et al, 1992; El-Deeb 2007; Fathy et al, 2012; Shreadah et al. 2014). Marine pollution affects water, sediments and biota. It can be related to oxygen-depleting substances, persistent organic pollutants (POPs), petroleum hydrocarbons, nutrients introduced by human activities or debris. Many different kinds of pollutants enter the Mediterranean Sea from its shores (land-based sources) either by discharge points and dumping grounds (pointsource pollution) or from surface fluvial runoff (non-point-source pollution). Pollutants also enter the marine environments by atmospheric deposition, while others are introduced directly by marine activities such as shipping, fishing, mining, and oil and gas exploration. Water quality is a critical factor significantly affects human and all oceanic organism health. Monitoring of the environmental quality is of great importance to determine effecti...