The spatial and seasonal variability of the microphytoplankton and ciliates communities in relation to the environmental factors were studied in the southern coastal area of Sfax. Results revealed a striking difference between seasons regarding pH, with strong acidification in autumn generated by industrial activity. Spatial distribution of pH in autumn impacted the microorganisms in different ways: acidic stations to the south showed significant correlations with Cyanobacteria, dinoflagellates and loricate ciliates whereas higher pH values in spring (pH > 8) were linked to diatoms richness. The high availability of inorganic phosphate is associated with the high release of phosphate due to residue from a phosphate treatment manufacture along the coast; consequently, N/P ratios were low (1.34–13.43) suggesting nitrogen limitation. Microphytoplankton abundance shifted from dinoflagellates dominance in autumn to dominance of diatoms during winter and of Euglenophyceae in summer. Loricate ciliates accounted for the largest proportion of the ciliates community while aloricate ciliates were relatively scarce during all seasons. Variability of ciliate community appeared not directly linked to environmental conditions, but significant positive relationships between abundance of loricate ciliates and microphytoplankton suggest that these ciliates may feed on microphytoplankton.

We studied the summer spatial distribution of the copepod community in both the neritic and oceanic areas of the Gulf of Gabès (Tunisia, eastern Mediterranean Sea) coupled with environmental factors. Copepods were the most abundant zooplankton throughout the sampling period, contributing 78% of the total zooplankton. A total of 14 copepod families were identified in all stations, with an overwhelming abundance of Acartiidae and Oithonidae (39.05 and 39.09% of total abundance, respectively). Abundance of Acartia clausi and chlorophyll-a concentrations were negatively correlated with salinity, suggesting that this species probably escaped the high coastal salinity (38 psu). Significant correlation determined between A. clausi and tintinnids at 50 m isobaths indicates that these planktonic ciliates probably served as a substantial food link towards higher trophic levels of this area. Conversely, Oithona nana which was well adapted to high chlorophyll-a concentrations and high salinity along the coast, showed significant correlations with Dictyochophyceae, Dinophyceae, Bacillariophyceae and Euglenophyceae, suggesting that this small copepod was capable of feeding on a wide selection of phytoplankton preys.

The radionuclide contents in waste products and physico-chemical characterization of effluent samples from some selected industries in the city of Lagos were carried out. The radioactivity concentration levels due to 40K, 226Ra and 228Th in the solid wastes were determined using gamma-ray spectrometry while physico-chemical determination of parameters were based on standard methods of measurements. The average radioactivity levels obtained was between 104 ± 14 Bq kg-1 and 1276 ± 31 Bq kg-1 for 40K, 86 ± 18 Bq kg-1 and 122 ± 23 Bq kg-1 for 226Ra and while for 228Th it ranged between 14 ± 2 Bq kg-1 and 73 ± 10 Bq kg-1. No artificial radioactive elements were detected in any of the samples. The average outdoor effective dose rate due to gamma exposure from these waste materials in the city was calculated as 0.12 mSv y-1. This is far less than 1 mSv y-1 recommended limit for the member of the public by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The pH of the effluent samples was slightly alkaline, while the electrical conductivity ranged between 275 and 455 µS cm-1 and total suspended solids ranged from 104 to 5616 mg l-1. All these ranges and those of biochemical and chemical oxygen demand values were all higher than the prescribed limits. Presence of heavy metals in the effluent samples was however lower than prescribed with the exception of iron.

A new contribution on spatial and seasonal variability of physico-chemical parameters of the Golfo San Jorge benthic system from autumn 2001 through summer to 2002 is presented. Temperature, salinity, density, oxygen content and chlorophyll-a in bottom water as well as concentration of total organic matter, total organic carbon, total nitrogen, total phosphorus, chlorophyll-a and phaeopigments in sediments were analysed. The origin and nutritional value of the deposited organic matter were also assessed. The results reflect the existence of: (1) a typical temperate water seasonal cycle; (2) a bimodal cycle in the phytoplanktonic production; and (3) seasonal variations in the chemical variables and in organic matter origin in sediments.

Three sectors which geographically correspond with those identified in previous studies were defined: (1) the inner area of the gulf; (2) the areas next to the north and south extremes; and (3) the coastal and south-east part.