Environmental properties of the southern Gulf of Aqaba, Red Sea, Egypt

Environmental properties (temperature, dissolved oxygen, nutrients and chlorophyll a) of the epipelagic zone off SharmEl-Sheikh, Red Sea, Egypt were studied seasonally throughout a year from March 1995 to March 1996. Water samples werecollected from five water depths (0, 25, 50, 75 & 100 m). The studied parameters exhibited clear seasonal variability along the water column. The vertical distribution of water temperature showed thermal homogeneity during most seasons, and thermal stratification in summer. Dissolved oxygen attained slightly high concentrations (5.3-7.8 mg l-1) in the whole water column, with slight seasonal variation. The concentrations of nutrients reflected dominant oligotrophic conditions in the epipelagic zone and occasional mesotrophic status at some depths. Phosphate fluctuated between 0-0.7 μM, ammonium (0-2.27 μM), nitrite (0-0.72 μM), nitrate (0-1.49 μM) and silicate (0-6.48 M). Phytoplankton biomass was generally low in the epipelagic zone throughout the study, whereas chlorophyll a was less than 0.5 μg l-1, except relatively high concentration (0.7-1.12 μg l-1) in deep layers in spring. In comparison with previous studies on the Gulf of Aqaba all environmental parameters during present study showed pronouncedlydifferent values

Hydrography, nutrients and plankton abundance in the hot spot of Abu Qir Bay, Alexandria, Egypt

The hydrography, nutrient levels and plankton abundance were investigated monthly for a complete annual cycle in the southwestern part of Abu Qir Bay, the most polluted and biologically productive area on the Egyptian Mediterranean coast. Intense temporal and spatial variability was observed in all measured parameters characteristic of the effects of several effluents discharged into the bay. Based on the present investigation, the southwestern Bay can be divided ecologically and biologically into two parts: one including the near shore strip, which is directly affected by the waste waters, and a second comprising the southwestern part of the coastal strip and the offshore stations, both of which are relatively far away from the land-based effluents.The Bay water was characterized by low transparency (monthly average: 64-280 cm), dissolved oxygen (monthly average 2.0-6.8 mg/l) and surface salinity (monthly average: 24.8-37.9 ppt), the highest limits usually being in the offshore section. Water fertility and plankton production were high in the Bay indicating an occasionally acute degree of eutrophication, particularly nearshore. Great variations occurred in the concentrations of nutrients throughout the year, with monthly averages of 0.8-50.88 mM for ammonia, 0.42-3.28 mM for nitrite, 1.29-17.36 mM for nitrate, 0.32-3.61 mM for reactive phosphate and 1.09-33.34 mM for reactive silicate. Similarly, the abundance of both phytoplankton and zooplankton showed pronounced temporal and spatial variability, whereas the monthly average chlorophyll-a fluctuated between 2.06 and 52.64 mg/l and zooplankton between 31x103 and 248.6x103 ind./m3. However, the absolute values of all parameters indicated remarkably wider ranges of variations.Significant correlation was found between chlorophyll-a and some ecological parameters like temperature, salinity, transparency, dissolved oxygen, nitrite and between zooplankton and temperature, while there was a significant correlation between nutrient concentrations and salinity changes

Ecological indices as a tool for assessing pollution in El-Dekhaila Harbour (Alexandria, Egypt)

Statistical analyses of data concerning the phytoplankton standing crop and biomass were applied as a tool for assessing pollution in El-Dekhaila Harbour. Univariate and multivariate analysis showed a succession of three clusters associated with salinity and temperature variations. The first and third clusters comprised mainly diatoms and dinoflagellates. The second cluster, richer in species, was dominated by brackish water cyanophytes, chlorophytes and euglenophytes. The diversity index ranged from 0.08 to 2.41. A high diversity was associated with high evenness, reflecting the multidominance pattern of cluster (2). On the other hand, multiple correlations between salinity and standing crop, richness and evenness, were negative and significant, but positive with the diversity index. The ABC curve showed that the k-dominance curve for numerical abundance extends above that for the biomass when clusters 1an d 3 are dominant. Both curves coincide more or less for another segment of the curve but when cluster 2 becomes dominant the numerical abundance curve runs below that of the biomass. Such a pattern may indicate unpolluted or moderate to heavily polluted conditions in El-Dekhaila Harbour. The present study reveals that the combination of univariate and multivariate analysis with the ABC curve provides a promising tool for the characterization of phytoplankton dynamics under stress conditions. On the other hand, the phytoplankton community in El-Dekhaila Harbour is stressed not by the inflow of brackish water but rather by the inflow of sea water. This is indicated by the higher diversity and evenness, and by the ABC curve during the dominance of cluster (2)

Seasonal changes in the biochemical components of Pseudonereis anomala (Polychaeta, Nereididae) from the Alexandria coast, Egypt

AbstractThe biochemical composition (carbohydrates, protein, lipids, fatty acids and amino acids) of the nereid polychaete Pseudonereis anomala Gravier 1901, from a shallow part of the Alexandria coast (Egypt), was studied seasonally. The results revealed that P. anomala had a lower water content, higher carbohydrates and protein, but approximately similar or higher lipid levels than several other polychaetes.Fatty acids appeared to be dominated by unsaturated acids, constituting seasonally 49.6–81%, while saturated acids reached high amounts in winter and spring (23.3 and 38.3% respectively). C20:5n-3 was the major polyunsaturated fatty acid, accompanied by small amounts of C18:4n-3, C20:4n-6, C16:1n-7 and C20:1n-9. C18:0 dominated the saturated fatty acids for most of the year, except in autumn when C16:0 was the major one

Statistical and fourier analysis of cyclic changes of zooplankton abundance in the eastern harbor of Alexandria

279-290Time series data of monthly averages, over three stations, for counts of zooplankton groups and species, and some environmental factors (water temperature, salinity and chlorophyll a) were collected from the Eastern Harbor of Alexandria, during the period of 48 months, from October 1999 to November 2003. The spectral density graphics with frequency indicated that inspite of the presence of several peaks for different variables the only significant peak, at 95% confidence limit, was found in case of water temperature. The results of Fourier analysis show that the most common periods that are relatively important and affecting the movement of the time-series of environmental and the biological variables are 12, 9 and 6 months. The 12 months was corresponding to seasonal changes, while periods less than 12 months were due to local changes depending on the hydrological exchange between the Eastern Harbor and the open Mediterranean coastal waters in front of the study area. The time lags of the occurrence of the maxima of each two variables at the important cycles with periods 12, 9 and 6 months were calculated to express the response time of the different groups flourishing relative to the occurrence of the effecting environmental factors. The cluster and correlation analyses of the different variables have also been done to show most correlated ones. The results indicated that the annual cycle is the most important one in most cases. The multiple regression equations between the zooplankton counts and the environmental variables showed the important controlling factor in the different species and groups of zooplankton

Eutrophication problems in the Western Harbour of Alexandria, Egypt

Eutrophication-related problems in the Western Harbour ofA lexandria were studied monthly from April 1999 to March 2000. Variation in salinity appeared to be the key to all changes in water quality and plankton abundance in the harbour. Both at the surface and near the bottom the salinity was lower (annual average: 35.1 and 38.3 PSU respectively) than in the open sea (39 PSU). Dissolved oxygen levels indicated poor aeration conditions along the water column (2.3–3.98 mg l−1). Average pH values were approximately similar in the two layers (8.1 and 8 respectively) but exhibited different ranges ofv ariations. Nutrient salts varied widely, often occurring in high concentrations, with ranges of 0.12–5.7 and 0.06–2.6 μM at the surface and the bottom respectively for phosphate, 0.21–20.46 and 0.25–18.12 μM for nitrate, 0.29–3.3 and 0.23–1.66 μM f or nitrite, 0.56–57.46 and 2.32–43.73 μM for ammonia and 0.3–36.3 and 0.48–38.4 μM for silicate. As a result ofn utrient enrichment, phytoplankton growth was very intensive, reflected by an abnormally high concentration ofc hlorophyll a (annual average: 33.82 μg l−1). At the same time the death ofl arge numbers ofp hytoplankton cells could be inferred from the relatively large amount of phaeopigment (annual average: 10.39 μg l−1). The high levels ofn utrient salts and phytoplankton biomass together serve as a good indicator ofhig h eutrophication levels in the Western Harbour throughout the year. These conditions clearly affected the zooplankton stock, which varied between 5.8–93.6×103 indiv. m−3, although for most of the time values remained at a low level (annual average: 26 728 indiv. m−3)

Protozoa in a stressed area of the Egyptian Mediterranean coast of Damietta, Egypt

AbstractThe Damietta coast is part of the Egyptian Mediterranean coast off the Nile Delta and has recently been polluted as a result of intensive human activities. The environmental parameters and protozoan community in the area were studied biweekly from January to December 2007. The results of the environmental parameters indicated low salinity, oxic and anoxic conditions, high nutrient levels and intensive phytoplankton growth. A total of 69 protozoan species were identified, belonging to Amoebozoa (8 species), Foraminifera (12 species), non-tintinnid ciliates (22 species) and tintinnids (27 species). The numerical density of protozoans was high over the whole area, with annual averages between 8.2×103 cells m−3 and 51.4×103 cells m−3. Spring was the most productive season for protozoans, but several distinct peaks were observed during the year at the sampling sites. The protozoan groups showed clearly different spatial patterns in both composition and abundance: whereas amoebozoans and non-tintinnid ciliates were dominant in the more polluted areas (sites IV and V), tintinnids dominated in the less polluted areas (sites, I, II and III). Several pollution indicators were recorded: amoebozoans – Centropyxis aculeata, Centropyxis sp., Cochliopodium sp., Difflugia sp.; non-tintinnids – Bursaridium sp., Frontonia atra, Holophrya sp., Paramecium sp., Paramecium bursaria, Vasicola ciliata, Vorticella sp., Strombidium sp.; tintinnids – Favella ehrenbergii, Helicostomella subulata, Leprotintinnus nordgvisti, Tintinnopsis beroidea, Stenosemella ventricosa, Tintinnopsis campanula, T. cylindrica, T. lobiancoi, Eutintinnus lusus-undae