Ecological Studies on Lake Al-Asfar (Al-Hassa, Saudi Arabia) with Special References to the Sediment
Some characteristics of Lake Al-Asfar were studied seasonally from May, 2008 to April, 2009. Analysis of sediment core analysis showed that, the maximum content of Zn (5.2 ppm) and Cu (2.5 ppm) were recorded at 5.0 and 25.0 cm depth, respectively. The highest value of Pb was 9.02 ppm at 1.0 cm depth. Eight fungal species belonging to 4 genera were collected from the sediment of Lake Al-Asfar. Penicillium oxalicum was the most common fungus recovered from all sections of the core up. Pythium sp. was the present at the upper section of the sediment. Marked seasonal quantitative and qualitative differences occurred in the phytoplankton communities of the lake. Five algal groups (Chlorophyceae, Cyanophyceae, Chrysophyceae, Bacillariophyceae and Euglenophyceae) were recorded during the investigation. The maximum seasonal succession was found in the spring, whereas the lowest value was occurred in the fall. The total crop densities were mainly a reflection of the trends in numbers of Chlorophyceae. Chlorella sp., Chlorococcus humicola, Oedigonium sp., Scenedsemus bijuga, Cycltella meneghiniana, Cyclotella ocellata, Fragillaria capucina, Gyrosigma sp., Navicula lanceolata, Synedra acus and Rhadomonas ovalis.
Water chemistry exhibit variable physical and chemical characteristics and
consequently variable biological compositions. These variations depend mainly
on the type and nature of the water area itself as well as on the manmade additions
or runoff of minerals and chemicals from agriculture soils (Fathi
and Flower, 2005). It is known that, the environmental variables such as
physical and Chemical factors affect aquatic life, either saline or brackish
water, lead to the appearance of special types of biota (Fathi
and Kobbia, 2000; Fathi et al., 2001; Fathi and
Flower, 2005; Al-Kahtani et al., 2007).
Wetlands are areas on which water covers the soil or if water is present either
at or near the surface of that soil. A wetland may be found in: shallow lakes:
areas of permanent or semi-permanent water with little flow (e.g., ponds, salt
lakes, volcanic crater lakes). Wetland ecosystems are sensitive to any disturbance
and they not only support biological diversity but also provide because of direct
and indirect economic benefits (Flower, 2001).
Lake Al-Asfar represents of those important shallow wetland lakes. However,
much of their limnology and its biotic information are still unknown. Few studies
were conducted on lake Al-Asfar. The vegetation communities (Youssef
et al., 2009) and sedimentological, hydrogeological, chemical structure
(Al-Dakheel et al., 2009) of lake Al-Asfar were
studied. Recently, Fathi et al. (2009) studied
the water quality and phytoplankton communities in lake Al-Asfar, over a period
of one-year (March, 2007 to February, 2008). The area is characterized by widespread
growth of halophyte shrubs associated with a very thin salt crust on the sabkha
surface (The lake is the site of the confluence of migratory birds from outside
the area visited by dozens of the virtues of birds (Fathi
et al. (2009)). This study was designed to investigate the presence
of pollutants (heavy metals) in the lake using sediment records as well as fungal
spores to assess biological patterns. Physical water characteristics and phytoplankton
were also measured.
MATERIALS AND METHODS
Lake Al-Asfar is one of the important shallow wetland lakes. It is located
on Al-Hassa, Eastern region of Saudi Arabia. Al-Hassa Province is one of the
largest oases in the world and located (25° 05' and 25° 40') in the
Southern part of the Eastern region of Saudi Arabia. The main salient morphologic
features of Lake Al-Asfar are wetlands, sabkhas and sand dunes. There are salt
tolerant vegetation (halophyte) found in some of the less salt affected sabkha
Sampling and Analysis
Samples were collected from lake Al-Asfar from May, 2008 to April, 2009.
Subsurface water samples (2 L) were taken from the lake on each visit. A liter
was not filtered and is used for pH, conductivity, alkalinity and chlorophyll.
Other liter one was filtered through a Whatman GF C-1 filter apparatus
equipped with suction pump for analysis. This sample was used for analysis of
the major ions for which preservation is not essential. After tightly capping,
samples were returned to laboratory and kept in the dark at 4°C until analysis.
The sediment samples were taken from the uppermost 1 cm sediment collected
during the April, 2008 by a spade box core device (GKG). One sediment core was
retrieved from the lake using a technique of Berglund and
Ralska-Jasiewiczsowa (1986). The core was sectioned as 2 cm interval and
each 2 cm section sample was placed in a Whirlpak bag for temporary storage
in a cold at 4°C. Sub-sampling for fungal spore occurrence was taken place
during initial core sectioning avoiding contamination.
After dissolution of sediment samples, the metal concentrations were measured by a Varian Atomic Absorption Spectrophotometer (AA-6800F, Shimadzu, Japan).
Sediment core was dissected and side surfaces placed under aseptic conditions
in sterilized plastic bags. Fungal spores were isolated by the dilution plate
method as described by Abdel-Hafez et al. (1990).
Glucose-Czapeks agar medium supplemented by chloromphinicol (0.5 mg L-1)
and rose bengal (30 μg L-1) and incubated at 28°C for 7
days. Five replications were performed for each sample and the developing fungi
were identified and counted and the numbers were calculated per gram dry soil.
Pythium sp., which were expected to be in the sediment were isolated using
VP3 (Ali-Shtayeh et al., 1986) selective medium:
sucrose 20 g L-1, corn meal agar 17 g L-1, agar 23 g L-1,
CaCl2 0.01 g L-1, MgSO4.7H2O 0.01
g L-1, ZnCl2 0.001 g L-1, micro-elements: CuSO4.5H2O
0.02 mg L-1, MoO3 0.02 mg L-1, MnCl2
0.02 mg L-1, FeSO4.7H2O 0.02 mg l L-1,
antibiotics: pimarcin, 5 mg L-1, vancomycin, 75 mg L-1,
penicillin, 50 mg L-1, pentachloronitrobenzene, 130 mg L-1
and thiamine-HCl 100 μg L-1. Soil from the sediment soil was
putted on VP3 media and fungi isolated identified using the Key of Pythium
species (Plaates-Niterink and Van-der, 1981) and others
(Abdelzaher, 1999). Hyphal tips of colonies appeared
in VP3 medium were transferred to Water Agar (WA) 2.5-3% and incubated at 20°C
to obtain a colony c. 1 cm diameter. The agar medium was inverted and incubated
until the colony reached the edge of Petri dish. Slivers of agar containing
single hyphal tips were removed from the margin of the colony and transferred
to Corn Meal Agar (CMA) (Plaats-Niterink and Van-der, 1981)
slants for storage. Hyphal tips were also transferred to CMA+500 μg mL-1
wheat germ oil to stimulate the formation of sexual structures. Pieces from
7-day-old colonies incubated at 25°C were transferred to Nutrient Broth
(NB) to confirm the absence of bacteria. The developing fungi were identified
according to (Booth, 1977; Domsch and
Gams, 1972; Domsch et al., 1980; Raper
and Fennell, 1965; Samson et al., 2004).
Temperature and pH values of lake water were measured in the field by a
digital pH-meter (Lutron, pH 204), respectively. The Secchi disc depth was measured
also in the filed. Conductivity was measured using calibrated conductivity meter
(CM 25 conductivity meter). Dissolved oxygen was measured according to Winkler
method (Strickland and Parsons, 1972). The calculated
values are the mean of triplicates; the standard deviation was less than 5%
of these mean values. Chlorophyll-a content of water was determined according
to the method described by Strickland and Parsons (1972).
Qualitative and Quantitative Analysis of Phytoplankton Composition
The technique developed by Uttermohl (1936) was adopted
for quantitative investigation of the phytoplankton. One and half liter water
sample was collected in a cylinder on each sampling occasion and treated with
Lugols iodine solution (Iodine in potassium iodide). Each sample was then allowed
to settle at least 36 h, where upon the supernatant was siphoned off and the
volume was adjusted to 100 mL and kept at 4°C until analysis. Besides, Sedjwick-Rafter
cell was repeatedly used for cell counting. The simplified methods described
by Willen (1976) and Hobro and Willen
(1977) were followed for counting phytoplankton. The average numbers of
phytoplankton (unicellular, colonial and filamentous) were performed for every
species. The results were then, expressed as number of cells per liter. Qualitative
analysis was carried out using the preserved as well as fresh samples. These
were examined microscopically for the identification of the present genera and
species. Diatoms frustules with and without chloroplast was included. The algal
taxa were identified according to standard references, including Smith
(1950), Fott (1972), Bourrelly
(1981) and Prescott (1987). The calculated values
are the mean of triplicates; the standard deviation was less than 5% of these
RESULTS AND DISCUSSION
The biotic variables used to describe different freshwater areas are often related to environmental factors such as climate, chemistry and pollution. A consideration of these factors leads to a better understanding the biology of aquatic habitats. The present study was carried out in a shallow Lake Al-Asfar.
The results of heavy metals from Lake Al-Asfar are shown in Fig.
1. The data revealed that the maximum content of Zn (5.2 ppm) and Cu (2.5
ppm) were recorded at 5.0 and 25.0 cm depth, respectively. The highest value
of Pb was 9.02 ppm at 1.0 cm depth. Establishment of metal levels in sediments
could play an important role in detecting sources of pollution in aquatic systems
(El-Sammak and El-Sabrouti, 1995; Peters
et al., 2001; Fathi and Abdelzaher, 2003).
Accordingly, the highest value of Pb in the sediment at 0.5 cm depth is a clear
indicator of lake pollution in agreement with Fathi et
al. (2001). Shakweer et al. (1993) reported
that Cu and Zn concentration in the fish flesh were found to be lower than the
levels allowable for the human consumption. However, values of Pb were higher
than the tolerable concentration for man. This pollution could was thought to
be associated with the input from different drains (Fathi
and Abdelzaher, 2003).
Eight fungal species belonging to 4 genera were collected from the sediment
soil of Lake Al-Asfar. Penicillium oxalicum Currie and Thom was the most
common fungus recovered from all sections of the core up to the 10 cm deep section
of the core (Table 1). Penicillium oxalicum could be
tolerating anoxic condition. Pythium sp., was present in the most upper
section of the sediment and disappeared thereafter.
|| Heavy metals stratigraphy from Lake Al-Asfar sediment
|| Fungi presented in Al-Asfar Lake sediment
Pythium catenulatum Matthews, P. flevoense Van der Plaats-Niterink,
P. papillatum Matthews, Pythium group F and Pythium group
P were found to be occurred only in the upper 2 cm of the sediment. This indicates
that Pythium sp., could not to be tolerate the absence of oxygen. Trichoderma
koningii Oudem and Trichoderma sp., were only found in the upper
4 cm of the sediment. In Japan, many isolates of Trichoderma sp. were
isolated from the sediment of Sagami Bay of Off-Izu Islands (Imada
et al., 2001; Fathi and Abdelzaher, 2003).
This result was the harmony with the present study which indicated that Trichoderma
sp., prefers that condition. Aspergillus niger Van Tieghem was detected
up to 6 cm deep while Penicillium oxalicum was detected up to 10 cm depth
and no fungi were found after that. Noteworthy that no active fungal spores
were detected below 10 cm sediment depth (Table 1).
The average water temperature of Lake Al-Asfar was subjected to seasonal variations.
The lowest values were recorded during winter (12.5°C), while the highest
value was found at the summer (33.2°C).
||Seasonal variations of (a) temperature, (b) pH, (c) total
dissolved salts, (d) visibility, (e) oxygen content and (f) Chl-a content
in Lake Al-Asfar during the investigation period. Vertical bars indicate
SE, n = 3
The differences in temperature represent one of the main factors responsible
for the differences in the phytoplankton quantity and quality (Fathi
and Flower, 2005; Fathi et al. (2009)). Like
all inland waters (Flower, 2001) the pH values of Lake
Al-Asfar ranged between 7.65 and 8.86 at winter spring and spring, respectively.
The lowest values of pH recorded in the Al-Asfar lake may be due to the great
amount of agricultural water discharged into the lake (Fig. 2),
as well as, to the decomposition of plankton and organic matter (Gharib
and Soliman, 1998; Fathi et al., 2009).
Figure 2 showed that the total dissolved salts in the Lake
water was higher in summer (8.02 g L¯1), whereas it dropped
to a minimum level in winter (3.32 g L-1). The lake water showed
low transparency in summer (18 cm) and the highest in winter (25.0 cm) (Fig.
2a-f). Water transparency was greatly affected by phytoplankton and zooplankton
blooms (Gharib and Soliman, 1998; Fathi
and Flower, 2005) and disturbance (circulation) of the sediment by wind.
Dissolved oxygen is an important variable for identification of different water
masses (Fathi et al., 2001). Various aquatic
animals including fishes require high levels of oxygen. Figure
2 showed that the maximum oxygen concentration (15.21 mg L-1)
was recorded in spring, while the minimum (5.29 mg L-1) was recorded
in the winter (Fig. 2). The relatively high concentrations
of dissolved oxygen recorded in this study could be due to the increased photosynthetic
activity of phytoplankton populations.
||Relative occurrence of the phytoplankton on Lake Al-Asfar
during the study period
|(High = 4; Moderate = 3; Frequent = 2; Rare = 1)
In this respect, Talling (1976) stated that oxygen super
saturation due to photosynthetic activity is often encountered in regions with
abundant phytoplankton. On the other hand Chlorophyll-a content in spring exceeded
that recorded in other samples (Fig. 2), which could be attributed
to vigorous phytoplankton growth (Fathi and Kobbia, 2000;
Fathi and Abdelzaher, 2003).
It is evident from the data in Table 2 and Fig.
3-5 that there are is a seasonal differences in quantitative
and qualitative composition of the phytoplankton. According to phytoplankton
abundance the data of Fig. 4 shows that the highest count
was found to be in spring (21.30x105 cell L-1), followed
by summer (18.40x105 cell L-1) and the lowest crop was
harvested in autumn (9.40x105 cell L-1).
||Percentage composition of the main algal groups recorded at
Lake Al-Asfar during the investigation period
||Phytoplankton abundance for Lake Al-Asfar during the investigation
period. Vertical bars indicate SE, n = 3
It could be clearly seen that Chlorophyceae was the most dominant group, Bacillariophyceae
ranked second, Cyanophyceae the third, Euglenophyceae the fourth and Dianophycae
come the fifth group in the order of dominance during studied period (Fig.
3). Bacillariophyceae reached maximum in winter (38.32%) which was associated
with increased numbers of Cyclotella meneginiana, while the minimum (21.21%)
was recorded in summer.
||Seasonal variations of the species richness (total number
of phytoplankton taxa encounted per standard sample count) of Lake Al-Asfar
phytoplankton, during the investigation period. Vertical bars indicate SE,
n = 3
In contrast, the blue green algae reached its maximum level in the summer
(34.22%), while the minimum (18.21%) was found to be in winter. Euglenophyceae
was appeared in all seasons except winter. However, Dinophyceae was recorded
in summer, autumn and winter (Fig. 3).
Total of forty three genera were mainly identified during the whole period of study (Table 2). Out of these, 15 genera belong to Chlorophyceae, 17 to Bacillariophyceae, 7 to Cyanophyceae, 3 to Euglenophyceae and 1 to Chrysophyceae. On the other hand, the maximum species richness (38 species) was found in the spring, while the minimum (15 species) was in the winter (Fig. 5). Generally, the phytoplankton showed a remarkable increase as compared with the previous records (Fathi et al. (2009)) and this indicated high level of eutrophication in Lake Sector. Furthermore, Fathi et al. (2009) reported that Lake Al-Asfar is indicates heavy polluted in autumn and winter and moderate pollution in spring and summer.
In conclusion, the investigated lake is contaminated with discharge waters containing chemical fertilizers in addition to domestic and industrial effluents. Pollution and climate greatly affected the hydrography and the physico-chemical properties of water as manifested by the high amounts of organic matter, high concentrations of nutrient salts which caused some increase in levels of eutrophication.
The author would like to acknowledge the assistance provided by different laboratories
of the Biology Department, College of science, King Faisal University for both,
allowing using some of their equipments and/or providing some basic materials
for performing the experiments needed for the study.
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