Seagrass (Cymodocea nodosa) ability to remove cadmium and nickel ions from single metal solutions was investigated in the present study. Metal ions were measured in the solution using an atomic absorption spectrophotometer. Various operational parameters (initial pH, biomass dose, metal ion concentration, and contact time) were tested and found to affect the uptake capacity of Cd (II) and Ni (II). More than 70% of biosorption capacity occurred in the first few minutes for both metal ions. The pseudo-second-order kinetic model and the Langmuir model were found to best fit the experimental data of Cd (II) and Ni (II) biosorption. The maximum uptake capacity (q_max) was 11.6 and 16.7 mg.g⁻¹ for Cd (II) and Ni (II), respectively. The biosorbent was characterised using Fourier transform infrared spectrometry (FTIR), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX). The infrared spectrum demonstrated that hydroxyl, carboxyl, and phenolic functional groups are the major binding sites for Cd (II) and Ni (II) metals. The ion exchange mechanism plays an important role during biosorption process as shown in EDX analysis. Our results conclude that marine macrophyte C. nodosa can be used as a low-cost biosorbent for the removal of Cd (II) and Ni (II) in wastewater.

The impacts of different CO2 concentrations on the growth, physiology and ultrastructure of noncalcifying microalga Chaetoceros gracilis F.Schütt (Diatom) were studied. We incubated Ch. gracilis under different CO2 concentrations, preindustrial and current ambient atmospheric concentrations (285 and 385μatm, respectively) or predicted year-2100 CO2 levels (550, 750 and 1050μatm) in continuous culture conditions. The growth of Ch. gracilis measured as cell number was decreased by increasing the pCO2 concentration from nowadays concentration (385μatm) to 1050μatm. The lowest percentage changes of oxidizable organic matter, nitrite, nitrate, phosphate and silicate were recorded at a higher pCO2 (1050μatm), 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 CO2 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=−0.742, p⩽0.05). On the other hand, highest growth rate at pCO2=385μatm was also confirmed by the maximum uptake of nutrient salts (NO3=68.96μmol.l−1, PO4=29.75μmol.l−1, Si2O3=36.99μmol.l−1). Total protein, carbohydrate and lipid composition showed significant differences (p⩽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 CO2 concentration (1050μatm). It is concluded from this regression equation and from the results that the growth of Ch. gracilis is expected to decrease by increasing pCO2 and increasing ocean acidification

Poor published data are available for the detections of toxic phenolic compounds in the Egyptian Mediterranean Coast. Seasonal and spatial distributions of eight driven toxic phenolic compounds in coastal waters of Alexandria from ten different locations, situated between Abu Qir bay and Eastern Harbor during July, December (2018), and February, April (2019), were investigated to determine contamination status, possible sources, and ecological risks in the study area. For that purpose, a method was optimized for derivatization and detection of methylphenols, chlorophenols, and nitrophenols in water samples using GC-MS. This analytical method was validated using matrix spikes, indicating detection limits (0.02–0.5 µg/ml) and good recoveries (70–120%). Ranges of phenol concentrations in water samples were as follows: phenol (<LOD-109.2 ng/l), 2,4-DMP (<LOD-117.68 ng/l), 2-nitophenol (<LOD −87.09 ng/l), 2,4 dichlorophenol (19.93–66.30 ng/l), pentachlorophenol (13.50–60.08 ng/l), 2-chlorophenol (13.23–91.43 ng/l), 2,4,6-trichlorophenol (12.9–46.04 ng/l), and 4-chloro-3-methylphenol (15.2–52.3 ng/l). Methylphenols were the major group detected followed by nitrophenols and chlorophenols. Results of the risk assessment revealed that concentrations of the studied phenols were within the safe limits and lower than Surface Water Toxicity Reference Values (TRVs), giving no indication of pollution. Multivariate statistical analysis with different physicochemical parameters of water indicated the greatly variable behavior of phenolic compounds, and the exact sources of these compounds are difficult to identify since no major point sources of pollution are known in the area of study.