Effects of Continental input on marine environment in the Lebanese coastal waters

INOC‐CNRS, International Conference on “Land‐Sea Interactions in the Coastal Zone” Jounieh ‐ LEBANON, 06‐08 November – 2012

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EFFECTS OF CONTINENTAL INPUT ON MARINE ENVIRONMENT IN THE LEBANESE COASTAL WATERS

Marie Abboud-Abi Saab*, Milad Fakhri, Abed El Rahman Hassoun, Mary Tilbian, Marie-Thérèse Kassab, Nada Matar

National Council for Scientific Research - National Center for Marine Sciences,P.O. Box 534, Batroun, Lebanon

E-mail*: [email protected]

SUMMARY

The effect of continental inputs on environmental conditions and chlorophyll-a have been studied monthly in surface water samples from 5 littoral stations in central Lebanese coastal waters for a period of 3 years between September 2009 and June 2012. Three stations show different levels of impact as a result of river inputs and sewage discharges. The other 2 stations were taken as references.

During the study period, temperature followed its normal annual cycle whereas salinity varied spatially and temporarily sometimes with low values due to the continental inputs (range = 1.3 - 39.65). Significant nutrient fluctuations were also recorded (range N-NO3= 0.34-40.8 µmole/L; range P-PO4= 0.11-5.8 µmole/L). High levels of nitrate were observed at stations located near rivers and sewage discharge points while high levels of orthophosphate were detected in the stations affected by sewage waters. These inputs however, cause an increase in primary productivity as evidenced by chlorophyll-a levels; therefore, chl-a concentrations (range= 0.01- 8.9 mg/m3) throughout the study period showed high values in the stations affected both by sewage and river inputs comparing to the reference stations; this result could lead to a dystrophic situation.

The outcome of the one way analysis of variance (ANOVA) for the whole period showed significant differences within the stations for all the considered environmental variables except temperature. The results were different when the analysis was done within seasons. The intermittent discharge of river and sewage effluents and the deteriorated conditions observed near the shoreline created a clear difference in the levels of the studied parameters. According to the results and comparing to the reference values of Lebanese coastal waters, the area of Antelias River shows signs of eutrophication as a direct result of river and sewage inputs.

Keywords: Lebanon, coastal waters, continental input, environmental parameters, chlorophyll-a.

1. INTRODUCTION

Given that it is a Mediterranean country, Lebanon presents two main seasons: a dry hot season and a cold rainy season. However, in the absence of large rivers, coastal waters are fed by a series of small permanent rivers (about 15) and streams distributed all along the coast and whose discharge values of seasonal amplitudes are very important [1]. The regime of precipitation is excessive and large amount of freshwater reach the sea through a series of valleys along the coast. The freshwater input from the river is seasonal while the second source of continental input from discharges of sewers is permanent and considerate knowing that 70% of the Lebanese people live in the coastal cities according to [2]. Nutrients, originated from river inputs may lead to an increase


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in primary production and phytoplankton biomass and a decline in water column N/P ratio in coastal areas, i.e. the system has become more N-limiting [3]. Continental input influences primary productivity in two ways: first, because freshwater (a major component of terrestrial contribution) is less dense: it contains far fewer dissolved salts than the seawater, thus it rests on top of seawater and creates a stratified water column [4]. Second, it often carries nutrients [5] that phytoplankton need to carry out processes, including photosynthesis.

Eutrophication of the coastal area is the outcome of the most pronounced effects resulting from continental input causing a threat to the marine environment. According to [6], this phenomenon is an enrichment of water by nutrients, especially nitrogen and/or phosphorus and organic matter, causing an increased growth of algae and higher forms of plant life to produce an unacceptable deviation in structure, function and stability of organisms present in the water and to the quality of water concerned, compared to reference conditions. Nutrients and chl-a as relevant quality elements are mandatory in some European directives and recommended in others. Therefore, in addition to the measurements of nutrient concentrations (nitrate, nitrite and orthophosphate ions), it’s important to monitor phytoplankton biomass expressed as chl-a, which is considered an important tool in the assessment of eutrophication level due to the pigment composition and the active element of autotrophic cells that it contains [7].

In Lebanon, the study of the effect of continental input on the marine environment in the past was limited to certain areas only [8], [9] & [10]. The aim of this paper is to study monthly the effect of continental input on marine environment on a large part of the central Lebanese coast during three years period.

2. MATERIALS & METHODS

2.1. Study area Within the framework of a Lebanese-Italian project (CANA) carried out in the National Center of Marine Sciences (NCMS), five stations located in the central part of the coast, extending between Anfeh and Beirut, were chosen: two stations (Tri-20 & Bey-11), considered as "references" and not affected by any river outflow and domestic discharges, and three other stations (Byb-20, Byb-22 & Jun-40), influenced at different levels by rivers streams and/or sewage. The geographic coordinates, the locations and the substrates type of the studied stations are mentioned in table (1) and figure (1).

Figure 1: Geographical locations of the studied stations in Lebanese coastal waters


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Table 1: The coordinates and characteristics of the 5 stations monitored on the Lebanese coast between September 2009 & August 2012.

Neighboring City

Stations code

Longitude Latitude Location Substrate type

Anfeh Tri-20 35º 44.160 34º 22.054 Deir Natour/Las-Salinas

Rocky

Fidar-Byblos Byb-20 35º 39.035 34º 06.142 Fidar bridge Sandy

Nahr Ibrahim Byb-22 35º 38.539 34º 03.625 Nahr-Ibrahim river River mouth

Antelias Jun-40 35º 34.970 33º 55.020 Antelias river Sandy

Beirut Bey-11 35º 28.518 33º 54.120 American University of Beirut

Rocky

2.2. Sampling methods & Laboratory analyses

The samples were collected monthly, from September 2009 to August 2012, using a 5 L bucket at surface level near the sea shore. Temperature was measured immediately in situ using an ordinary thermometer. Salinity was measured by the conductometric method using a Beckman salinometer (S7-RC model). Fresh samples intended for the analysis of nutrients were stored in polyethylene bottles to avoid any later alteration of concentrations. It was brought to the laboratory, in ice boxes at darkness, where the samples were frozen at - 20ºC until the analysis time. Nitrite ions (N-NO2) were measured following the method of [11], nitrate ions (N-NO3) by [12] with a slight modification consist in using ammonium chloride instead of EDTA as an activator according to [13] and orthophosphates ions (P-PO4) by [14]. Samples for measuring of total chlorophyll-a (chl-a) were filtered through a Whatmann GF/C filter at low pressure. Pigments were then extracted in 90% acetone for 24h in the cold and the dark. The concentration was determined by a spectrophotometer according to the monochromatic method of [15]. The volume of sea water filtered varied between 1 and 4 liters according to stations. The biomass is expressed in quantity of chl-a over volume of sea water (mg/m3).

Data for precipitation and air temperature between January 2009 and August 2012 were obtained from Byr Hassan coastal station.

2.3. Statistical analysis of data Descriptive statistics (mean, standard deviation (SD), minimum, maximum) for environmental factors at the five studied stations and for biological factor were calculated. One-way ANOVA was performed in order to test statistical differences between four seasons at the five studied stations using JANDAL Sigma Stat software program, version 2 (See table 1 for abbreviations). This analysis was performed on hydrological parameters (temperature and salinity), nutrient concentrations (orthophosphate, nitrite and nitrate), and chlorophyll-a. Data of one biological, 5 environmental parameters measured in 180 samples from 5 stations and monthly precipitation rate were organized in matrices of correlation.

3. RESULTS

3.1. Meteorological parameters Average monthly variations of meteorological parameters (precipitation & air temperature) are presented in figures (2a & b). The average monthly precipitation varied from zero mm in summer period to 256 mm in January 2012. In every year, wet season is almost limited to September-May period. The average monthly air temperature follows its normal annual Mediterranean cycle with a maximum of 29.33 ºC in August 2010 and a minimum of 13.37 ºC in January 2012.


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Figure 2: Average monthly variations of precipitation (mm/month) {a} and air temperature (ºC) {b}at Byr Hassan coastal station, between January 2009 and August 2012. (p < 0.05)

3.2. Environmental parameters Descriptive statistics (mean, standard deviation, minimum and maximum values) of the environmental parameters measured at the 5 stations studied from September 2009 to June 2012 in the Lebanese coastal area are given in Table (2). Table 2: Mean, standard deviation, minimum and maximum values of each parameter in the studied stations

between September 2009 and August 2012. Stations Parameters (abbreviations)

Tri-20 Mean±SD Min-Max

Byb-20 Mean±SD Min-Max

Byb-22 Mean±SD Min-Max

Jun-40 Mean±SD Min-Max

Bey-11 Mean±SD Min-Max

Temperature(ºC) (T )

23.76a ±4.44 17.5-31.5

24.08 a ±4.34 18.5-32

22.79 a ±5.36 13.5-31.5

24.06 a ±4.39 18-31.5

24.19 a ±4.29 18-31

Salinity (S)

39.12 a ±0.31 38.40-39.76

38.43 a ±0.88 35.03-39.92

29.24b ±11.21 1.27-39.44

34.16bc ±5.4 19.07-39.41

39.18 a ±0.26 38.67-39.69

Orthophosphates (µmol/L) (PO4 )

0.25 b ±0.13 0.02-0.62

0.15 b ±0.12 0.04-0.71

0.24 b ±0.14 0.05-0.55

2.12 a ±1.71 0.44-5.77

0.12 b ±0.07 0.02-0.32

Nitrate (µmol/L) (NO3)

0.65 b ±0.86 0.17-5.34

3.35 b ±2.3 0.75-11.3

14.2 a ±11.88 1.55-42.3

11.36a ±11.8 0.71-38.19

0.84 b ±0.6 0.08-3.43

Nitrite (µmol/L) (NO2)

0.05 b ±0.04 0.01-0.13

0.12 b ±0.06 0.04-0.28

0.13 b ±0.06 0.05-0.3

0.91a ±0.79 0.14-4.28

0.13 b ±0.09 0.004-0.4

Chlorophyll-a (mg/m³) (Chl-a)

0.17 b ±0.11 0.03-0.5

0.39 b ±0.21 0.11-1.14

0.3 b ±0.19 0.04-0.87

2.4a ±2.27 0.24-8.9

0.5 b ±1.15 0.06-6.81

ab The differences in the mean values in each row between stations with different superscripts are statistically significant

(a)

(b)


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During the period of study, the water temperature varied between 13.5 ºC at Byb-22 (February 2012) and 32ºC at Byb-20 (August 2012) (figure 3a) and the mean values (±SD) between 22.79°C (±5.36) (Byb-22) and 24.19 °C (±4.29) (Bey-11). The salinity ranged from 1.27 at Byb-22 (May 2010) to 39.92 at Byb-20 (January 2011) (figure 3b) and the mean values (±SD) between 29.24 (±11.21) and 39.18 (±0.26) at Byb-22 and Bey-11 respectively.

Figure 3: Monthly variations of water temperature (ºC) {a} and salinity {b} at the studied stations between

September 2009 and August 2012. Orthophosphates concentrations varied between 0.02 µmol/L at Bey-11 and Tri-20 (April 2012) and 5.77 µmol/L at Jun-40 (February 2011) (figure 4) while the mean values (±SD) varied between 0.12 (±0.07) in Bey-11 and 2.12 (±1.71) µmol/L in Jun-40. Nitrate levels oscillated between 0.08 µmol/L at Bey-11 (January 2010) and 0.17 µmol/L in Tri-20 (September 2009) and 42.3 µmol/L at Jun-40 (February 2012) (figure 5) while the mean values (±SD) varied from 0.65 (±0.86) at Tri-20 and 14.2 µmol/L (±11.88) at Byb-22. Nitrite ions levels varied between 0.004 (Bey-11, June 2010) and 4.28 µmol/L (Jun-40, June 2010) (figure 6) while the mean values (±SD) varied between 0.05 µmol/L (±0.04) in Tri-20 and 0.91 µmol/L (±0.79) at Jun-40.

Figure 4: Monthly variations of orthophosphate ions (PO4) [µmol/L] at different stations between September 2009 and August 2012.


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Figure 5: Monthly variations of nitrate ions (NO3) [µmol/L] at different stations between September 2009 and August 2012.

Figure 6: Monthly variations of nitrite ions (NO2) [µmol/L] at different stations between September 2009 and August 2012.

3.3. Results of analysis of variance The analysis of variance (ANOVA) showed that the differences in the mean values of temperature among the stations are not great enough to exclude the possibility that the difference is due to random sampling variability; there is not a statistically significant differences between stations on temperature (P>0.05); but the ANOVA applied between seasons showed that there is a significant difference between stations only during spring season (Bey-11 vs. Byb-22; Byb-20 vs. Byb-22 and Jun-40 vs. Byb-22) (p<0.05) (figure 8).

Figure 8: Comparison of the mean temperature between seasons in the 5 studied stations from September 2009 to August 2012.


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For salinity, ANOVA showed there is a significant difference between stations (Bey-11 vs. Byb-22, Jun-40; Tri-20 vs. Byb-22, Jun-40; Byb-20 vs. Byb-22; Jun-40 vs. Byb-22) (table2). The comparison between stations of the seasonal mean values of salinity showed significant differences only during spring and summer (figure 9).

Figure 9: Comparison of the mean salinity during seasons between the studied stations from September 2009 to August 2012.

For orthophosphate and nitrite ions, ANOVA showed that there is a significant difference between Jun-40 and the other stations (p<0.05) (table 2); also, the comparison of the mean values between stations at each season showed a significant difference between Jun-40, the most affected station by river input and sewers, and the other stations during all the seasons (P<0.05) (figure 10). The same results for nitrite mean values (figure 12) while for nitrate there is a significant difference between stations for total period (Byb-22 vs. Tri-20, Bey-11 and Byb-20; Jun-40 vs.Tri-20 and Bey-11) and in summer, spring and winter (p<0.05) (figure 11).

Figure 10: Comparison of the mean orthophosphate ions between studied stations on the different seasons between September 2009 and August 2012.


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Figure 11: Comparison of the mean nitrate ions between studied stations during different seasons between

September 2009 and August 2012.

Figure 12: Comparison of the mean nitrite ions between studied stations during the four seasons, between September

2009 and August 2012.

3.4. Biological parameter During the period of study, chlorophyll-a concentrations fluctuated between 0.03 mg/m³ at Tri-20 (November 2010) and 8.9 mg/m³ at Jun-40 (January 2011) (figure 12) but many other peaks are noted in Jun-40. The mean values (±SD) varied from 0.17(±0.11) at Tri-20 to 2.4 (±2.27) mg/m³ at Jun-40 (table 2).

Figure 12: Monthly variations of chlorophyll-a (mg/m³) at different stations between September 2009 and August

2012.


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3.5. Results of analysis of variance Analysis of variance showed that there is a statistically significant difference (P <0.05) in the mean values of chlorophyll–a among the different stations for the whole period (table2) and in all seasons between Jun-40 and the other stations (figure 13).

Figure 13: Mean values of chlorophyll-a (mg/m³) at different stations during seasons, between September 2009 and August 2012.

Results of Bravais–Person correlation matrix, applied at each station between environmental parameters, precipitation rate on one side and the chlorophyll-a on the other side (Table 3) showed the presence of significant positive correlation between temperature and salinity at Tri-20 and the stations influenced by river’s freshwater (Byb-20 & Byb-22), the existence of significant correlations between temperature, salinity and nutrients in the different stations except Tri-20. The rain showed a significant negative correlations (p<0.05) with temperature in Byb-20, Jun-40 and Bey-11 (r = -0.35, -0.36 & -0.34) respectively and positive with orthophosphate in Byb-22 (r=0.52). Chl-a did not show any significant correlation (p>0.05) with any of these parameters in the five studied stations except with salinity in Byb-20 (r= -0.41, p<0.05).

Table 3: Bravais–Person correlation matrix showing relationships between the studied parameters at each station between September 2009 and August 2012. T S PO4 NO3 NO2 Chl-a Rain

1 0.49* 0.28 -0.07 0.28 0.14 -0.32 T 1 0.08 0.01 0.37* -0.02 0.17 S 1 0.12 -0.11 -0.24 -0.12 PO4 1 0.06 -0.26 -0.12 NO3 Tri-20 1 0.26 0.11 NO2 1 0.12 Chl-a 1 Rain T S PO4 NO3 NO2 Chl-a Rain

1 0.45* -0.26 -0.37* 0.13 -0.13 -0.35* T 1 -0.1 -0.53* 0.25 -0.41* -0.06 S 1 0.17 0.46* 0.03 0.31 PO4 1 0.25 0.15 0.33 NO3 1 0.08 0.05 NO2 Byb-20 1 -0.02 Chl-a 1 Rain


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T S PO4 NO3 NO2 Chl-a Rain

1 0.76* -0.67* -0.82* -0.24 0.29 -0.27 T 1 -0.35* -0.87* -0.07 0.29 0.01 S 1 0.42* 0.01 -0.26 0.52* PO4 1 0.16 -0.3 0.17 NO3 1 0.12 0.32 NO2 Byb-22 1 -0.07 Chl-a 1 Rain T S PO4 NO3 NO2 Chl-a Rain

1 0.15 0.09 -0.34* 0.07 0.32 -0.36* T 1 -0.64* -0.77* -0.35* -0.18 0.16 S 1 0.62** 0.65* 0.12 -0.18 PO4 1 0.58* 0.12 -0.03 NO3 Jun-40 1 0.01 -0.27 NO2 1 -0.29 Chl-a 1 Rain T S PO4 NO3 NO2 Chl-a Rain

1 0.31 0.15 0.46* 0.50* 0.24 -0.34* T 1 0.36* 0.02 0.42* -0.09 0.14 S 1 0.36 0.37* -0.04 0.29 PO4 1 0.59* 0.09 -0.13 NO3 1 0.12 -0.08 NO2 1 -0.15 Chl-a Bey-11 1 Rain

NB: *significant correlations (P<0.05); n= 35 The pairs of parameters with significant positive correlation coefficients are colored in blue The pairs of parameters with significant negative correlation coefficients are colored in pink

4. DİSCUSSION

Based on the results presented above and given that Lebanon is a Mediterranean country, it seems that during the period of study the average monthly precipitation rate was concentrated during wet seasons and followed its normal Mediterranean cycle with high levels of rainfall during wet seasons and low rates or absence of rain during dry seasons. The highest mean precipitation rate (256 mm/month) was recorded during January considered the rainiest month. It is clear that the quantity of rain during 2009 and 2012 is more distributed between the months than during the years 2010 and 2011 (figure 2a). The average monthly air temperature followed its normal annual Mediterranean cycle with a maximum in August 2010 and a minimum in January 2012 (figure 2b).

The Lebanese littoral waters follow a normal annual cycle typical for the stations located in the center and north of the country [16] & [7], with maximum in August and minimum in February (figure 3a). The station affected by Ibrahim river input, had significantly the lowest water temperature because of the cold water loaded during snow melting phenomenon and this is why only in spring the differences between stations were significant. Spatially and temporarily, salinity variations were observed depending on the continental inputs. The lowest values of salinity were recorded at the stations affected by the river’s input (Byb-22) during May 2010 and sewage input (Jun-40) during June, whereas the highest values of salinity were recorded in the less influenced stations by continental inputs (Tri-20 and Bey-11) (Figure 3b); the fluctuations at Byb-22 and Jun-40 are


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important and well noted by the high standard deviations compared to the references stations. Following the northward current of the Lebanese coastal waters, the freshwater loaded in Byb-22 continue its path toward Byb-20, which has also its lowest salinity value during spring. During summer, the outflow of Ibrahim river decreases, this is why the salinity on the mouth becomes insignificant and the difference with the other stations not significant too, while the permanent sewage input at Antelias river’s mouth contributes to the persistence of low salinity values. There is a statistically significant difference in salinity between stations located at the rivers mouths during spring and summer seasons and the reference stations (Figure 9).

Nutrients did not present a well marked cycle because the studied stations are coastal and any sporadic or local input can easily disrupt the cycle. In addition, rainfall rate can dilute or concentrate the nutrients’ concentrations in river’s water. For example, during months with the highest precipitation levels (in 2009 & 2012), Antelias river’s water was diluted, consequently, modest values of phosphate ions were recorded, whereas during months with the lowest precipitation levels (in 2010 & 2011), high concentrations of phosphate ions were measured because of the continual contribution of sewage to the river’s water which is in its lowest rate (figure 4). The high values of nutrients at Byb-22 and Jun-40, indicate that these 2 stations are heavily influenced by continental input that increases the nutrients levels and decreases the salinity. This explains the negative significant correlation of phosphate and nitrate ions with salinity in these stations (table 3). The highest levels of nitrites ions were recorded at Jun-40, particularly during the months with low precipitation levels, maybe because of the presence of denitrified bacteria that play an important role in the transformation of nitrate (which is very high in this station) to nitrite during denitrification phenomenon, in a stable environment (weak turbidity, concentrated water in sewage,…) [17]. Almost the same results apply for chlorophyll-a; the highest values were detected at Jun-40 with a peak during January 2011. Whilst the lowest levels were measured at the reference station Tri-20. Comparing the monthly variations of chl-a between the studied stations, an irregularity of chl-a cycle was noted in the stations influenced by river and/or sewer inputs, whereas a very clear chl-a cycle with peaks of chl-a during spring and a slight increase during autumn, very close to what it is found in offshore stations [18], was observed at Bey-11. Comparing the concentration of chl-a between coastal & offshore stations, higher levels of chl-a were remarked even in the reference ones because all the stations are coastal and are affected at different levels by continental input [7] & [18].

It is important to mention that there is not a significant difference on nitrate between stations during autumn (P>0.05) because of the decline of Ibrahim river outflow (P>0.05), whilst significant differences were observed between the stations affected by river outflow and sewage (Byb-20, Byb-22 and Jun-40) and the reference stations during the other seasons (P<0.05) (figure 11).

It is important to note the high mean value of chl-a in Byb-20 compared to Byb-22 (the nearest station to the river mouth) (table 2); the freshwater rich in NO3, is not enough to increase significantly the primary production and thus the chl-a concentrations at the stations located near rivers because the phosphate is the limiting factor whereas the nitrate (provided by the river outflow) is in excess while in Jun-40 the both nutrients are available and thus the chl-a concentrations are the highest.

It is remarked that the positive effect of freshwater coming from rainfall did not lead to a high concentration of chl-a in the stations located near rivers (Byb-22) or discharges outlets; turbidity and water movement prevailing in the mouth river are not suitable conditions for a harmonious development of autotrophic organisms, that’s why a significant increase in chl-a was observed during spring at the less influenced station by continental input (Byb-20 & Bey-11). In addition, a turbulent sea state can cause a mixing of waters and remits bottom particles in suspension which release adsorbing nutrients to the surface, particularly the adsorbed orthophosphate ions on the particles [19].

It is evident that the correlation between temperature and rain on one hand and between temperature and nitrate on the other hand are negatively significant because it rains during the cold season and the freshwater is rich in NO3 (table3); but, due to the morphological characteristics of the Lebanese coastline (straight coast, current speed and direction, mixing water ,…. ) the freshwater inputs spread easily in the marine water and their


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positive supply in nutrients and so autotrophic development (expressed in this study by chl-a) is not shown in the river or stream mouths, that is why the correlation between rain and the chl-a was not significant at the different stations. Finally, comparing our results to the reference values of the Lebanese coastal waters, it’s clear that the station of Antelias River (Jun-40) witnesses signs of eutrophication as a direct result of continental inputs.

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[14] Murphy, J. & Riley, J. P. A modified single solution method for the determination of phosphate in natural waters. Analytica Chimica Acta. 27: 31-36, (1962).

[15] Lorenzen, C.-J. Determination of chlorophyll and pheophytin: spectrophotometric equations. Limnology

& Oceanography, 12 : 343-346, (1967). [16] Abboud-Abi Saab, M. Les caractères hydrologiques des eaux marines entre El-Mina et le Parc des Iles des

Palmiers. Hannon, 22: 59-69, (1993). [17]Grguric G., Wetmore S.S., Fournier R. W. Biological denitrification in a closed seawater

system. Chemosphere , 40 (5): 549–555, (2000). [18]Abboud-Abi Saab M., Fakhri M., Kassab M.-T. & Matar N. Effect of distance from the coast on

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Effects of Continental input on marine environment in the Lebanese coastal waters

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