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Assessment of eutrophication in Lake Timsah, Canal,

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ASSESSMENT OF EUTROPHICATION IN LAKE TIMSAH, , EGYPT

FEDEKAR MADKOUR, MAHER AAMER AND MOHSEN EL-SHERBINY

Department of Marine Science, Suez Canal University, Ismailia, Egypt. E-mail: [email protected]

Keywords: Eutrophication – Physico-chemical parameters – Biomass – Lake Timsah –Suez Canal.

ABSTRACT

To assess the eutrophication level in Lake Timsah, seasonal distribution of physico- chemical parameters and phytoplankton biomass were studied during the period between autumn 2005 and summer 2006. Ten stations were chosen to represent the impact of different human activities on the lake. The results indicated the presence of different habitats in the study area. Variations in salinity appeared to be the key to all changes in water quality in the lake. The western lagoon showed the lowest surface salinity (average: 1.5‰). The surface salinity increased gradually eastward fluctuating between 12 and 37.8‰. The lake is considered as a low transparent water body as the average Secchi disc readings ranged from 0.38 to 1.91 m in the western lagoon and navigation route respectively. Dissolved oxygen showed well oxygenated water at both the surface and near the bottom (annual averages: 5.2-7.7 mg/L). The highest concentrations of all measured nutrients appeared in the western lagoon and decreased gradually eastward coinciding with the increase of salinity reaching to the lowest values in the navigation route. The annual averages of nutrients at the surface and near the bottom respectively fluctuated between 0.68-4.87 and 0.21-1.63 µM for phosphate; 5.11-36.5 and 2.45-7.13 µM for nitrate; 0.06- 0.76 and 0.03-0.09 µM for nitrite and 3.36-29.93 and 0.66-2.71 µM for silicate. As a result of enrichment, phytoplankton growth was intensive as indicated by high concentration of chlorophyll a (annual average: 10.8-22.7 µg/L). The high nutrient salts and phytoplankton biomass together serve as a good indicator to classify Lake Timsah as eutrophic lake.

1. INTRODUCTION nitrogen and/or phosphorus and organic matter, causing an increased growth of algae Eutrophication of coastal waters has been and higher forms of plant life to produce an considered one of the major threats to the unacceptable deviation in structure, function health of marine ecosystems for more than 30 and stability of organisms present in the years (Ryther and Dunstan, 1971; Nixon, water and to the quality of water concerned, 1995; Elmgren, 2001; Bachmann et al., compared to reference conditions. 2006). The different processes and effects of Lake Timsah is considered as one of the coastal eutrophication are well known and important natural resources in Ismailia City. documented (Cloern, 2001; Conley et al., It represents a source of fishes, crustaceans 2002; Ronnberg and Bonsdorff, 2004). and shellfish largely consumed by local Andersen et al., (2006) reviewed recent population. Its role as nursery and feeding developments in the definitions of coastal ground for many larvae and juveniles of eutrophication and concluded that the crustaceans, molluscs and fishes is well accepted definition of eutrophication is the established (Mohammad, 1982; El-Etreby, enrichment of water by nutrients, especially 1986; Ghobashy et al., 1992; El-Mor, 1993; ASSESSMENT OF EUTROPHICATION IN LAKE TIMSAH, SUEZ CANAL, EGYPT

Ahmed, 2005). Moreover, the northern and region. Lake Timsah is considered as the western shores of the lake are rapidly biggest water body at Ismailia City with developing for tourism purposes. surface area of about 15 km2. The maximum Accordingly, increasing human activities depth of the lake is 6m in the western part during the last years in Lake Timsah can (undredged part) and 20 m in the eastern part greatly accelerate eutrophication by (dredged part). At the western side, the lake increasing the rate at which nutrients and is connected to a small, shallow lagoon organic substances enter the lake. These (about 1 m depth) via a narrow connection. substances can over stimulate the growth of This lagoon receives domestic and algae, creating conditions that interfere with agricultural wastewaters mainly from El- the recreational use of the lake, and health Mahsama and Abu-Gamous drains. and diversity of indigenous fish, plant and Accordingly, Lake Timsah suffers from the animal population. In addition, the particular domestic pressure such as sewage pollution, water quality of the lake affects the role of herbisides and pestisides (ETPS, 1995). the Suez Canal on the migration of the organisms between Mediterranean and Red 2. MATERIALS AND METHODS Seas. Many studies were carried on the ecology The present study extended from autumn and distribution of the biota in Lake Timsah 2005 to summer 2006 during four successive and only few of these studies gave seasons. Ten stations were chosen to cover information about the concentrations of the different localities representing variable nutrient and chlorophyll a (Gab-Alla, 1985; impacts on the lake (Fig. 1). Stations 1-3 are El-Serehy, 1989; Eweda, 1998; Nassar and located in the navigation route of the Canal, Shams El-Din, 2006). There is no study stations 4-9 throughout the lake and station performed on the water quality parameters to 10 in the western lagoon. All measurements indicate and characterize the eutrophication and water samples were taken at surface and status in the lake. In this context, the main near bottom waters except at station 10, objective of this study is to introduce data where surface samples only were taken due to about the water quality parameters and its shallowness. Water temperature, salinity, phytoplankton biomass of Lake Timsah that pH and dissolved oxygen were measured in required for assessing the trophic status and situ at each station using ordinary stand on the eutrophication problems in the thermometer, refractometer (ATAGO, lake. S/MILL, Model 8607), pH meter (JENWAY, Model 3070) and oxygen meter (JENWAY, 1.1. Study area Model 9070), respectively. Water Lake Timsah is one of the lakes in which transparency was estimated using a white the Suez Canal passes through (30° 13`, 30° enameled Secchi disc. For nutrients and 35`N and 32° 16`, 32° 18`E). Before the chlorophyll a, water samples were collected opening of the Suez Canal in 1896, the lake by PVC Nansen bottle (1.5 L). Nutrient was a saline shallow swamp which has been concentrations (phosphate, nitrate, nitrite and receiving the fresh water at high floods silicate) were determined in filtered seawater through the valley of . After the using GF/C filters according to the methods Canal opening, the lake was filled with the described by Parsons et al., (1984). For mixture of Mediterranean and Red Sea chlorophyll a, 500 ml of water samples were waters. After the completion of Aswan High filtered by 0.45 µm membrane filter, then Dam, the outflow of the Nile fresh water was extracted with 90% acetone and measured stopped and the lake received fresh water spectrophotometrically at the wave lengths from Ismailia fresh water canal which 630, 645, 665 and 750nm (Parsons et al., provides drinking and irrigation water to the

260 FEDEKAR MADKOUR et al

1984). For statistical analysis, a 2-tailed software program SPSS V. 12. Cluster Pearson Product Moment (PPM) Correlation analysis was applied according to Bray and and one way ANOVA were performed using Curtis (1957) using Primer Package V. 5.

Ismailia Sweet water Canal

1 7 8 Lake Timsah 10 9 4

l

Western lagoon a

n 6 a

C

2 z

e

u

S 5

3

Fig. (1)

261 ASSESSMENT OF EUTROPHICATION IN LAKE TIMSAH, SUEZ CANAL, EGYPT

3. RESULTS (1-2‰) throughout the whole study area (Fig. 2). The surface salinity increased gradually Water temperature in the lake follows the from annual average of 12‰ at station 9 normal seasonal fluctuations of Egyptian (near to the connection with western lagoon), climate. Thus, the lake was progressively to 28.5‰ at station 4 (in the middle of the warmed during spring reaching maximum lake). At navigation route (stations 1-3), the seasonal averages in summer (30.9 and effect of inputs is approximately disappeared. 28.9°C at the surface and the near bottom, The near bottom salinity was much higher respectively). While it decreased through than surface water with seasonal average autumn and reaching minimum seasonal fluctuated between 39.5 and 41.5‰. Seasonal averages in winter (16.7 and 16.6°C at the pattern was observed in surface salinity with surface and near the bottom, respectively) the highest average of 31.4‰ in summer and (Fig. 2). There is no significant variation in the lowest in autumn (37.6‰). water temperature between stations. The The pH of Lake Timsah water lies on the highest and the lowest surface temperatures alkaline side (annual averages: 8 and 8.06 for (32 and 15°C, respectively) were observed in surface and near bottom, respectively), the western lagoon (station 10) due to its demonstrating narrow spatial and temporal shallowness. Bottom water temperature variations (Fig. 2). The vertical distribution remained 1-2°C lower than that at the surface of pH is described by a higher pH near the during the period of study but increased by bottom relative to that at the surface water 0.5°C in autumn. throughout most of the study area. Water transparency is an important factor Lake Timsah was generally well affecting phytoplankton productivity. The oxygenated with annual averages ranged Secchi disc reading recorded throughout the from 5.2 to 7.7 mg/L at the surface and 6.2 to whole study area showed obvious spatial 7.7 mg/L near the bottom (Fig. 2), displaying variation in water transparency (Fig. 2). The similar trends of spatial and seasonal western lagoon was the most turbid area with variations. The oxygen levels showed small Secchi disc reading, fluctuating between 0.25 variations among stations except at station 10 m in summer and 0.50 m in autumn. which recorded the minimum value. The Conversely, the navigation route (stations 1- maximum dissolved oxygen contents were 3) displayed the highest transparency during observed during winter for surface and near the study period (0.85-2.70 m). While inside bottom waters (8.6 mg/L at station 3 and 8.5 the lake (stations 4-9), it was relatively low mg/L at station 1, respectively). The for almost the whole year with Secchi disc minimum values occurred during spring at readings varied between 0.40 m at station 9 in the surface (4.8 mg/L at station 10) and near spring and 1.95 m at station 8 in winter. the bottom (6.0 mg/L at station 6). Seasonal variation in water transparency All nutrients showed relatively similar showed unexpected results wherever autumn spatial trend with high concentrations in the and winter displayed relatively higher values western lagoon and neighborhood western than spring and summer. area of the lake. These concentrations The spatial distribution of surface water decreased gradually eastward and reached the salinity in the lake reflects obviously the lowest concentrations at the eastern side of effect of discharged wastes to the western the lake and the navigation route. lagoon, which sustained the lowest salinity

262 FEDEKAR MADKOUR et al

40 Surface Bottom 20 (°C) 0 autumn winter spring summer Temperature Season

8.2 surface bottom 8.0

pH 7.8

7.6 12345678910

8.0 Surface Bottom 7.0

6.0 DO (mg/l) 5.0 12345678910

) 3.0 Autumn Winter

2.0 Spring Summer

1.0 0.0

reading disc Secchi (m 12345678910

60 Autumn Winter 40 20 Spring Summer

Salinity (‰) 0 12345678910 St at io n s

Fig. (2)

263 ASSESSMENT OF EUTROPHICATION IN LAKE TIMSAH, SUEZ CANAL, EGYPT

Phosphate concentrations varied spatially concentration in the western lagoon and and seasonally within a relatively wide range relatively high values in the western area of (Fig. 3). Its levels were mostly higher at the the lake (stations 4 and 7-10). Summer surface water (annual averages: 0.68-4.87 appeared to be the suitable season for the µM) than near the bottom (annual averages: highest nitrite at the surface throughout the 0.21-1.63 µM). The western lagoon (station study area. The near bottom nitrite 10) and adjacent area in the lake (stations 4 demonstrated irregular seasonal distribution and 7-9) contained the highest concentrations at the different stations (Fig. 3). during autumn and winter, with the maximum Similar to phosphate and nitrate, silicate concentrations in surface water (6.43 µM) at subjected to wide range of variations with station 10 and near bottom (2.81 µM) at annual averages fluctuated from 3.36 to 29.93 station 9. By contrast, phosphate µM at the surface water and 0.66 to 2.71 µM demonstrated obvious decrease in surface near the bottom. The highest silicate content water during summer. On the other hand, the in the surface water was also reported in the surface and near the bottom waters in the western lagoon during all seasons, and eastern side of the lake (station 5) and relatively high contents in the western area of navigation route (stations 1-3) attained the the lake, but with variable values in different lowest concentrations (Fig. 3). seasons (Fig. 3). As usual, the eastern side Nitrate as the main form of dissolved and navigation route sustained the lowest inorganic nitrogen in the water column, silicate over the year. The near bottom waters varied widely at the surface and near the showed markedly lower concentrations of bottom with annual averages of 5.11-36.50 silicate than the surface, with pronouncedly µM and 2.45-7.13 µM, respectively. Variable different seasonal distributional patterns spatial and seasonal distribution patterns were throughout the lake (Fig. 3). observed for surface and near bottom nitrate The phytoplankton biomass (chlorophyll throughout the study area (Fig. 3). The a) was usually high, reflecting a high primary western lagoon attained the highest production in the lake. The annual average concentrations all over the year with values content of chlorophyll a in the lake was 16.5 ranged from 27.35 to 42.17 µM. Inside the µg/L, varying between 10.8 to 22.7 µg/L at lake (stations 4 and 6-9), surface water the surface at stations 5 and 10, respectively sustained almost higher concentrations than and from 2.7 to 5.6 µg/L near the bottom at the navigation route and eastern side (stations stations 5 and 9, respectively. Stations 6-10 1-3 and 5). On the seasonal scale, the nitrate maintained high chlorophyll a as compared to concentrations in the surface water were other stations. The absolute values varied higher in spring and autumn than in winter widely between 1.5-48.6 µg/L at the surface and summer. Near the bottom, the highest and 1.2-9.3 µg/L near the bottom. values were always recorded in spring and Chlorophyll a concentrations showed the lowest in summer, while the values seasonal variations with clearly higher values alternated the dominance during winter and during summer (average: 30.5 and 9.3 µg/L at autumn (Fig. 3). the surface and near the bottom, respectively) Nitrite was often in low concentrations at and spring (average: 23 and 6.1 µg/L at the the surface (annual averages: 0.06-0.76 µM) surface and near the bottom, respectively) and near the bottom (0.03-0.09 µM). In the (Fig. 3). surface water, it attained the highest

264 FEDEKAR MADKOUR et al

autumn Surface autumn Near bottom winter winter 8 spring 3 spring summer 6 summer 2 4 1 2

Phosphate (µM) Phosphate 0 (µM) Phosphate 0

Surface Near bottom

45 12 40 35 10 30 8 25 6 20 Nitrate (µM) Nitrate 15 4

10 Nitrate (µM) 2 5

0 0

Surface Near bottom

1.5 0.2

0.15 1.0 0.1 0.5

Nitrite (µM) Nitrite (µM) 0.05

0.0 0

Surface Near bottom

40 4

20 2 Silicat (µM) 0 Silicate (µM) 0

Surface Near bottom

60 10 40 5 (µg/l) 20 (µg/l) 0 0 Chlorophyll a Chlorophyll a 1234567891 123456789 Stations Stations

Fig. (3)

265 ASSESSMENT OF EUTROPHICATION IN LAKE TIMSAH, SUEZ CANAL, EGYPT

Fig. (4) According to cluster analysis (based on activities that bring large amounts of nutrient different physico-chemical parameters and salts and harmful substances to Lake Timsah chlorophyll a) the lake can be classified into appear to have a pronounced impact on the 3 clusters (Fig. 4). First group include station physico-chemical characteristics and 10 (western lagoon), which was characterized phytoplankton biomass in the lake. by low transparency, low salinity, highest The temperature values clearly reflected nutrients and chlorophyll a. The second the temporal-subtropical conditions of the group contains stations 4, 6-9 (western side lake at a particular sampling time with clear of the lake) which is affected by the fresh maximum in summer and minimum in water discharged from the western lagoon. winter. The maximum temperature (31ºC) The third group includes stations 1-3 and 5 recorded in the present study was similar to that represent the eastern side of the lake, that those recorded earlier (Wimpenny, 1930; contains high salinities and relatively low Shalla, 1985; El-Serehy, 1985; Eweda, 1998). nutrients. A significant difference between surface and deep water temperature (ANOVA, p < 0.01) 4. DISCUSSION was recorded in compatible with that reported by Farghally et al. (1988). Water quality parameters such as In general, the transparency of the lake dissolved oxygen, nitrogen, phosphorus and was almost low throughout the year even in light intensity are among the most important the navigation route with different degree of factors affecting phytoplankton productivity turbidity among stations. The correlation and thus the trophic status of a water body analysis showed there is no obvious (Akbay et al., 1999). Also, chlorophyll a can relationship between transparency and be used as indicator of algal biomass levels chlorophyll a concentration (r=0.41). This and thus eutrophication (Voros and Padisak, may indicates that extinction of light is 1991). According to estimates of ETPS mostly limited by factors other than (1995), the western lagoon receives about chlorophyll a (Oglesby and Schaffner, 1975). 833,000 m3/day of domestic and agricultural A significant correlation was detected wastewaters from many sources (El- between transparency and salinity (r= 0.63, Mahsama and Abu Gamous Drains, Abu- p<0.05). Accordingly, the lowest readings of Attwa sewage works and El-Bahtini Secchi disc were recorded in the western neighborhood). These different human lagoon (annual average: 0.38 m) and adjacent

266 FEDEKAR MADKOUR et al

stations. This may be attributed to the influx conditions that in turns have a positive effect of drainage water from different sources. This on the immigration of the biota throughout finding is in agreement with Eweda (1998) the Suez Canal. who stated that the highest total suspended The pH value in marine system has a very solids concentrations were recorded near the minor ecological role because sea water is western lagoon. On the other hand, the highly buffered and pH value remains relatively low transparency in the navigation relatively constant (Michael, 1984). The route is related to the mixing process caused alkaline nature of the lake water is well by the ship traffic. The high values of documented by the present and the previous transparency in winter and autumn indicate studies (Gab-Alla, 1985; Eweda, 1998 and that the water transparency of the lake is others). The spatial and seasonal fluctuations affected directly with the amount of the of pH in the present study were limited and discharged water. insignificant (ANOVA, p > 0.05). Salinity fluctuations in the lake reflect Dissolved oxygen is one of the most complex set of factors, namely the important factors in any aquatic system as it wastewater discharges from different sources, is involved in the metabolic activities of the evaporation due to insolation, the wind aquatic organisms and also in the action and the current system in the Suez biochemical cycles of the elements, therefore Canal. Significant variations in the salinity it serves as indicator of the water quality between stations and throughout water (Alabaster, 1959; MacCrimmon and Kelso, column (ANOVA, p<0.01) were detected 1970). Wide range of oxygen content in Lake while seasonal fluctuations were Timsah (4.3-11.9 mg/l) was recorded in insignificant. Accordingly, the area of study previous studies (El-Serehy, 1989; ETPS, could be divided into four regions with 1995; Eweda, 1998) and was emphasized in variable surface water salinities. The first is a the present study (4.8-8.6 mg/l). High oxygen freshwater region represented by the western content of the lake could be due to lagoon with salinity did not exceed 2‰, due photosynthetic activity in addition to wind to the discharges of different sources. The action and ship movement. The minimum second is a low salinity region at the western level of oxygen during the present study side of the lake adjacent to the connection virtually did not drop below 4.8 mg/l even in with the western lagoon (stations 8 and 9) the western lagoon. Thus, the oxygen with average salinity ranged between 12 and concentration in the study area was higher 21.8‰. The third region represent the main than the threshold level of well oxygenation basin of the lake (stations 4-7) where the (<4 mg/l) proposed by Heut (1973). This may surface salinity falls within the range of 28.5- indicates that the lake is not completely septic 33.8‰. The fourth region is the navigation and the human impact is still insignificant on route, in which the influence of inputs the levels of oxygen. Lake Timsah exhibited diminished and mostly disappeared from this the highest values of oxygen during winter region. Therefore, the most affecting factors (averages: 8.0 and 7.5 mg/l at the surface and on this region were the northward current near the bottom, respectively). This is mostly prevailing in the Suez Canal during most of due to low winter temperature which may the year and the increasing evaporation rate suppress the activity of many animals and during summer. According to the long-term decrease the rate of oxygen consumption observations, the maximum salinity in the (Welsh, 1952), beside increased aeration lake decreased gradually from 45‰ in 1988 caused by winds. The effect of (Sharaf, 1990) through 44‰ in 1998 (Eweda, aforementioned factors on oxygen 1998) to 42‰ during the present study. This consumption is almost reversed during warm indicates the chronic impact of the land-based seasons and this may explain the relatively effluents on the lake which may create new low oxygen content during summer (average:

267 ASSESSMENT OF EUTROPHICATION IN LAKE TIMSAH, SUEZ CANAL, EGYPT

6.4 mg/l at both the surface and near the supply of nutrients into the lake. No bottom). significant correlation was found between A striking characteristic of the measured chlorophyll a and nutrients due to the high nutrient salts was the presence of similar nutrients concentrations throughout the year. spatial distribution patterns with significant The accumulation of plant biomass variations between stations (ANOVA, depends on the factors that stimulate plant p<0.01). The highest nutrient salt growth. On average, the macronutrients concentrations appeared in the western (nitrogen and phosphorus) are present in lagoon and decreased gradually eastward, marine phytoplankton at an atomic ratio 16:1 coinciding with the increase of salinity, (Redfield, 1958). The differences between reaching the lowest values in the navigation nitrate and phosphate were further illustrated route. Significant correlations were found by the seasonal patterns in the N/P ratio. between salinity and nutrients (r= -0.95, - According to Chiaudani and Vighi (1978), 0.87, -0.86 and -0.51 for silicate, phosphate, the assimilation of these two elements by nitrate and nitrite, respectively; p<0.01). This marine algae is nearly optimal when N/P lies indicates that the freshening resulted from the between 4.5-6; phosphorus becomes the discharges controlled the levels of nutrient limiting element at a ratio > 6. While nitrogen salts. Eweda (1998) stated that the nutrient is the limiting factor at a ratio < 4.5. In the levels in the lake fluctuated between 0.9-7.5 present study, N/P ratio in the surface was > µM for phosphate, 5.7-54.7 µM for nitrate 6 at all stations. The near bottom water of the and 0.5-6.4 µM for nitrite. These levels are eastern side of the lake displayed a ratio > 6, slightly higher than those of the present while the western side showed a ratio < 4. study. This decrease in nutrient levels Since chlorophyll a concentrations reflected coincided with diminishing effluent extremely high phytoplankton production all discharges as compared to those of the last the year round, therefore it seems that a decade. This diminishing is related to the variable N/P ratio is not an indication of improvement of water treatment plants nitrogen or phosphorous limitation in the efficiency in addition to closing of some present study. drains (e.g. El-Bahtini drain). According to OECD (1982) the trophic Chlorophyll a is considered the main state or degree of fertility of water bodies pigment used for the determination of ranges from oligotrophic to mesotrophis to phytoplankton biomass. Carlson (1977) eutrophic with increasing of supply of reported that the number derived from nutrients and organic matter (Table 1). In chlorophyll a is best for estimating algal addition, Franco (1983) stated that biomass in most lakes and that priority should concentration of nitrate in eutrophic water is be given for its use as a trophic state usually 2.0 µM. While in oligotrophic water, indicator. In the present work, the average the nitrate concentration is about 0.5 µM chlorophyll a was 4 and 16.5 µg/L at the (Vucak and Strin, 1982). According to these surface and near the bottom, respectively. above mentioned classifications, the averages These value more or less similar to those of of Secchi disc reading (1.5-3 m), phosphate Eweda (1998) in the same area. The high (0.68-4.87 µM), nitrate (5.11-36.5 µM) and concentration of chlorophyll a in the lake is chlorophyll a (8-25 µg/L) in Lake Timsah undoubtedly due to the rich and continuous indicated eutrophic conditions.

268 FEDEKAR MADKOUR et al

Table (1): Mean annual values for the trophic classification system (sources OECD, 1982). Total phosphorus Chlorophyll a Secchi disc depth (µg/l) (µg/l) (m) Ultra-oligotrophic <4 <1 >12 Oligotrophic <10 <2.5 >6 Mesotrophic 10-35 2.5-8 6-3 Eutrophic 35-100 8-25 3-1.5 Hypertrophic >100 >25 <1.5

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List of figures

Figure 1. Map of Lake Timsah showing position of sampling stations. Figure 2. The distribution patterns of temperature (°C), pH, dissolved oxygen (mg/l), Secchi disc reading (m) and salinity (‰) in Lake Timsah. Figure 3. Seasonal distribution of phosphate, nitrate, nitrite and silicate (µM), and chlorophyll a (µg/l) contents in Lake Timsah. Figure 4. Dendrogram showing the similarity between different stations based on different physico-chemical parameters and phytoplankton bimass in Lake Timsah.

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