Chemical Evaluation for Western Coast of Mediterranean Sea in Egypt

pH, dissolved oxygen, oxidizable organic matter, as well as nutrient salts (NH4, NO2, NO3, PO4, and SiO4) were studied in the water of western coast of the Mediterranean Sea in Egypt (west of Alexandria) at different depths ranging from 0-200 m depth for inshore and offshore stations during winter (31 January to 5 February) and summer (3-10 September), 2006. During the last three decades, many touristic cities were constructed along the study coastal area. These coastal areas are exhibiting sings of stress, population pressures, and coastal development may lead to: declining fisheries, proliferation of harmful algal blooms nourished by sewage and agricultural run off close to beaches harming fish and causing health problems. Thus, this paper aimed to assess the eutrophication level in the study area.


INTRODUCTION
In the semi-enclosed Mediterranean Sea, nutrients are important tracers of biological cycles, new production, natural and anthropogenic inputs and transfer processes. 1,2Nutrient budget in the coastal

Study Area
The present study area is the western part of the Mediterranean coast of Egypt extends from Alexandria to Sallum (31˚ 1.2' 29˚ 30' to 32˚ 1.2' 25˚ 25').Nine short sampling stations were chosen to cover the area of study, among which the stations were located to cover the inshore and offshore areas of the coast.For the station locations, see Fig. 1. was analyzed according to the modified Winkler method (Grasshoff  1976). 4idizable organic matter (OOM) according to Calberg method. 5Nutrients (NH4, NO2, NO3, PO4, and SiO4) were analyzed spectrophotometrically according to oceanographic method described by Grasshof (1976) 4 using Shimadzu double beam spectrophotometer.

RESULTS AND DISCUSSION
The vertical profiles and spatial distribution of pH, dissolved oxygen, oxidizable organic matter, and the Nspecies (NH4, NO2, and NO3), as well as

Oxidizable organic matter (OOM):
Dissolved organic matter has various functions and plays important roles in chemical, biological, and even physical oceanography.Primary production is the ultimate source of organic matter in the sea. 7 This may be attributed somehow to vertical mixing of waters in winter under the effect of the prevailing wind and regime of water current.
Significant low values of OOM were noticed at inshore and offshore stations of El-Sallum section (Fig. 4).This expected low level of OOM might be attributed to the location of this section far from the landrunoff related to the human and agricultural activities.Generally, insignificant difference of OOM between the inshore and offshore stations among the studied sections was observed (Fig. 4).

Nutrient
Sea west of Alexandria depends on the water flows and nutrient concentration across the straits of Gibraltar and Sicily, together with atmospheric and terrestrial influxes.The main sources of nutrient salts in the study area from terrestrial environment are the river discharge, coastal water, water outfalls, excess nutrients in fresh water have been well understood and documented since the mid 20 th century.In contrast, an awareness of the potential importance of eutrophication in the coastal and marine environment has been developing only since the early 1980s. 392 Bull High Inst Public Health Vol.38 No.1 [2008] Accordingly, the main objective of the present study was to provide systematic data on nutrient salts, dissolved oxygen, and organic matter along the western part of the Mediterranean coast of Egypt to consider the causes and concerns relating to eutrophication in this coastal area.
winter and summer of 2006, two field trips were performed by research vessel belonging to the National Institute of Oceanography and Fisheries.Sampling was performed by Assistant Lecturer Mohamed Abd El-Naby.This study was a part of the research plan of the Institute, development of the pelagic and the demersal fish and invertebrates along the Egyptian coast between Alexandria and Sallum among the predominant environmental conditions.Temperature and pH were determined in situ at time of sampling using a portable microprocessor based temperature and pH meter model M90.Dissolved oxygen (DO) OOM was measured in the study area during winter only.The results indicate that OOM ranged between 0.0 and 3.96 mg O2/L.Many stations throughout most of the study area recorded 0.0 mg O2/L OOM, while a maximum of 3.96 mg O2/L was found in Ras El-Hekma at 100 m depth (Fig. 2-a).Irregular vertical variations of OOM were observed for almost all stations.

CONCLUSIONS 1 . 4 . 6 .
down to 25 m depth.Obvious high concentrations of all nutrients except NH4 were observed in summer season (Figs.2-a, 2-b, 3-a and 3-b).Ammonia concentration showed an interesting pattern of variation.In winter, at Ras El-Hekma, Alamin, Ras Alam El-Rum and Martouh, ammonia concentrations were increased from surface down to 50 m depth and then decreased down to 100m depth.After that, in deep waters the homogeneity in concentrations was observed in deep water.In contrast, for summer season, the concentrations at all stations were decreased from surface water down to 25 m depth, and then increased down to 50 m depth.After that, more or less constant concentrations of NH4 were recorded in deep water (Fig. 2a).High concentrations of ammonia were Bull High Inst Public Health Vol.38 No.1 [2008] found in winter with values varied from 0.25 to 8.6 µmol/l.This may suggests the occurrence of denitrification process.However, in summer season ammonia showed low concentrations ranged from 0.80 to 3.70 µmol/l.This result demonstrates that in the euphotic zone (up to 25 m depth) of Mediterranean of the west coast of Alexandria, ammonia is the preferable uptake by phytoplankton as a nitrogen source for assimilation during summer, while in winter, nitrate may support primary production more than ammonia does.During the period of study, the water column profiles for NO2 and NO3 showed sharp decrease of both ions from surface down to 25 m depth, reflecting high consumption of these DIN forms by planktonic organisms.Fahmy 8 found that the surfacial water in Dabaa and Sallum area, DIN constituted a mean value of 3.81±0.53% of TN revealing the increasing consumption and deposition rates for these inorganic constituents.In winter season, NO2 depletion was appeared in intermediate water column (50-100 m depth) at Alamin and Matrouh sections.High concentration values ranged from 0.25 to 0.48 µmol/l were observed in the intermediate and bottom water of Alamin, Dabaa, and Ras El-Hekma.In summer, vertical pattern of NO2 variations was almost the same as in winter season, however NO2 content was higher and its values ranged from 0.075 to 1.213 µmol/l at 25 m depth of Ras Alam El-Rum and Ras El-Hekma, respectively.These high summer concentrations of NO2 in the intermediate and bottom waters may be reflecting dentrification process.In winter, NO3 levels increased rapidly (reached to 6.97 µmol/l) at 150 m depth and bottom water of Ras Alam El-Rum, Matrouh, and Sallum sections with respect to surface content.This may be attributed to the release from bottom sediment and occurrence of nitrification process as , the accumulation of nitrate with concentrations ranged from 5.73 to 10.76 µmol/l in the intermediate water (50-100 m depth) at almost all sections demonstrating low rate of nitrate consumption by phytoplankton.Fahmy 8 observed a diminish in phytoplankton biomass in the intermediate water (120-250 m depth) of the same area of the west coast of Alexandria.It is worth to mention that this observation came in accordance with low level of NH4 obtained during this study at the euphoric zone in summer.The content of PO4-P in sea water was greatly higher in summer than in winter.The concentration values ranged from depletion to 0.95 µmol/l in winter and from 0.05 to 3.55 µmol/l in summer.lots of summer resort constructions along the west coast of Alexandria.According to Béthoux et al., 9 the hypothesis of an influx increase from phosphate sources over the whole Mediterranean is in qualitative agreement with global scenario proposed by Meybeck 10 where total dissolved phosphorus in land surface water globally increases proportionally to the watershed population and to its energy consumption.During winter, the potential tourism decreases leading to the decrease of human activity using detergents.Consequently, low PO4 content reached to depletion appearing in the surface water.Moreover, the depletion of PO4 appeared also at the euphotic zone in many stations of the study area.This illustrates that phosphate ion is the limiting factor for phytoplankton growth during this season. 11Bull High Inst Public Health Vol.38 No.1 [2008] Depletion or low level of phosphate in the intermediate and deep waters resulted from phosphate removal by adsorption on particles.High concentration of 0.45 µmol/l was obtained at 150 m depth of Alamin and Ras El-Rum sections during winter reflecting the rapidly recycling of phosphorus in deep water.Krom et al., 11reported that primary production in the eastern Mediterranean has been shown to be phosphorus limited.Silicate behavior in the water column is more or less similar to that of nitrate (Figs.2-b and 3-b).In winter, silicate concentrations were low and ranged from 0.90 µmol/l at 200 m depth of Ras Alam El-Rum to 4.08 µmol/l at 25 m depth of Sidi Barani (Fig. 2-b).However, obvious high concentrations of silicate were found in summer as a result of increasing land runoff and urban activities.These high values ranged from 3.18 µmol/l at 200 m depth of Sidi Barani to 20.13 µmol/l at 100 m depth of Ras El-Hekma (Fig. 3-b).During winter, silicate was consumed in the euphotic zone (25 m depth) in most stations.Enrichment of silicate observed at the intermediate water of certain stations may have resulted from dissolution and sinking of diatom frustules.Regeneration of silicate from the bottom sediment and releasing into the overlying bottom water could be the reason for high silicate content in deep water.The vertical profiles of nutrient concentrations observed in this study are opposite to the classical nutrient profiles obtained by Béthoux et al., 9 at Algero-Provencal basin of the Mediterranean Sea.This study may suggest the characteristic of high eutrophication level in the euphotic zone (25-50 m depth) of the western coast of the Mediterranean Sea (Alexandria) in Egypt. of spatial and seasonal variability for the Mediterranean Sea water of studied area.Seasonal changes are more pronounced than spatial variations (Fig. 4).Generally, spatial distribution of nutrient concentrations showed slight variations among sections during summer and winter.This may be due to well mixing of water mass under the influence of prevailing wind and current regime along the coast.Sharaf El Din et al., 12 mentioned that the current regime appeared at the coastal area of Mediterranean Sea (west of Alexandria) to consist of sustained periods of wind induced, easterly flow, when the dominant wind direction was from the north-west.Increasing trends for nutrient concentrations except ammonia were observed in summer season for both inshore (up to 50 m depth) and offshore (up to 200 m depth) stations.In summer, Ras El-Hekma showed the highest concentration of phosphate (1.83 µmol/l) and silicate (20.13 µmol/l) at offshore stations, while the highest concentration of ammonia (4.70 µmol/l) and nitrite (1.21 µmol/ l) appeared at its inshore stations.Sallum, Matrouh and Ras El Hekma recorded the lowest concentrations of phosphate (0.0-0.25 µmol/l) at inshore and offshore stations during winter.Generally, phosphorus concentrations are low in sea water and can limit biological productivity in some marine ecosystems. 13,14Spatial variability of silicate was very low during both summer and winter.However, silicate content was three times (average value 5.14 µmol/l) for summer season than in winter (average value 1.85 µmol/l).Insignificant difference in nutrient concentrations appeared among inshore and offshore stations during the study period demonstrate extending effect of terrestrial inputs seawards.These results reflect the increased population activity during summer (tourism Season) as an external source of terrestrial inputs to this area of the Mediterranean Sea.The obtained data in this study could serve for more investigation to understand the impact of the development and new constructions established along the Bull High Inst Public Health Vol.38 No.1 [2008] western coast of Mediterranean Sea in Egypt (west of Alexandria).The vertical profiles of nutrients data obtained in this study showed clearly reversed shape to the classical features of nutrients levels in the Mediterranean Sea recorded by Béthoux et al. 9 2. In general, no clear differences between nutrient elements were observed among most of studied sections.This might be attributed to the influence of prevailing winds and water current regime in this region.3. Symptoms of eutrophication were observed at the costal area of Mediterranean, west of Alexandria, the terrestrial and land-run off inputs.This study paid attention to the shallow 25 m depth to under investigation.The obtained data enabled to prove clearly the presence of eutrophication with nutrients in this layer.Moreover, this study added further support to recognize the load of nutrients in surface and euphotic zone after constructions along the coast.5.Both denitrification and nitrification processes appeared in the water column of the area under investigation in summer and winter; respectively.Observed low and depleted phosphate levels in this study confirmed that phosphorous, as usual, is a limiting factor for biological productivity in marine ecosystems.

Fig. 2
Fig. 2-b: Vertical profiles of nutrients concentrations at offshore stations of studied sections along the western coast of Alexandria during winter, 2006

Fig. 3 -
Fig. 3-b: Vertical profiles of nutrients concentrations at offshore stations of studied sections along the western coast of Alexandria during summer, 2006.

Table 1a :
The average values of studied parameters at inshore station of different sections of the western coast of Mediterranean Sea in Egypt (west of Alexandria) during 2006.

Table 1b :
The average values of studied parameters at offshore station of different sections of the western coast of Mediterranean Sea in Egypt (west of Alexandria) during 2006.