Relationship between algae diversity and water quality- a case study: Chah Niemeh reservoir Southeast of Iran

Abstract

Algae are known with many detrimental impacts on drinking water quality. Discharge of municipal and agricultural wastewater into the receiving water resources make desirable conditions for algae growth and consequently cause eutrophication phenomena. Water samples were withdrawn monthly from 5 stations in Zabol City within spring and summer seasons. To identify algae species, micronutrients, and physical parameters such as temperature, depth of Secchi disk (SD) and pH on their growth were evaluated. The average phosphate in spring and summer were observed to be 0.034 and 0.028 mg/L, respectively. The results obtained from the present study indicated that the volume and depth of the water reservoirs were less critical on total phosphorus compared with the concentration of algal cells and total nitrogen. The mean pH for water samples taken from Chah Niemeh (CN) in spring and summer were observed to be 8.4 which is suitable for algae growth. Furthermore, the mean temperature (>20 °C) in both seasons were found to be desirable for the growth of algae, especially cyanobacteria in the CN. Moreover, the mean SD in spring and summer samples was 96.16 m and 119.83 m, respectively. As a result, the reservoir had low transparency in terms of algal growth. Totally, most of the identified algae were green algae (50%), algal flagella (19%), cyanobacteria (15.4%) and diatoms (15%). Therefore, cyanobacteria are most possible responsible for the taste and odor in the CN water reservoir. Future efforts should be directed toward preventive measurements for protecting water reservoirs from municipal and agricultural wastewaters and algae control.

Introduction

Protection and optimal use of water resources are considered as a priority for every country to meet the sustainable development goals worldwide [1]. Surface and groundwater resources are most important in supplying water needed for various activities such as agriculture, industry, and drinking objectives [2]. Recently, in pace with the human population explosion and urban development, the discharge of pollutants arisen from urban sewage and agricultural runoff to lakes has increased significantly [3]. Discharge of wastewater into the water bodies and excessive uses of fertilizers in agricultural activities make desirable conditions for algae growth [4]. They contain nutrients including N, P and K, which cause algal blooms and eutrophication phenomena in water resources [5]. Algae taking advantage of phosphatase enzymes can absorb phosphorus through the hydrolysis process. As eutrophication and algal bloom abate the water quality, therefore, monitoring the algae is of great importance in water reservoirs [5]. Determination the quality index and degree of pollution of water resources requires careful considerations and environmental indicators. As organisms inherently respond to any undesirable condition occurred in aquatic ecosystems, bio-monitoring method is a promising technology to detect any adverse effects in the aquatic ecosystem [6]. Thus, bio-monitoring is one of the appropriate indicators to determine water quality and aquatic populations that can provide appropriate responses to environmental challenges [7]. In addition, chemical analysis has some drawbacks such as time, cost and technical restrictions which can influence the survey of water quality [8]. The most common types of freshwater algae in aquatic ecosystems include planktonic and benthic. In the viewpoint of color classification, blue-green (cyanophyta), green (chlorophyta), brown-gold (phaeophyta), and red (radophyta) [9] are mostly observed in aquatic environments. The water body can be affected by intracellular and extracellular metabolites of algae (especially cyanobacteria) which occurred bothduring the growth and decay process. For instance, sulphides and terpenoids compounds could be generated by cyanobacteria [10]. The previous studies indicated that in spite of the importance of algae in water quality, there is no global algal index in “Guideline for Water Quality Monitoring of Reservoirs” in Iran to determine the quality of water resources [11]. There are few studies focusing on heavy metals in water [12], bed sediment [13] and pesticides [14] in Iran water reservoirs which might affect the water quality and the presence of algae. The presence of algae can result in the formation of toxic materials such as microcystin in ponds and lakes as well [15, 16]. In case of addition of nutrients the lake water quality could be deteriorated by high algae production [17],

The Chah Nimeh (CN) water reservoir in Sistan is the only drinking water source for five cities: Zabol, Zahak, Hirmand, Hamoun and Nimroz which serve population of 447,350 people. In addition, one drinking water supply line is stemmed from CN for Zahedan. Water entering into the CN reservoir originates from the Helmand River in Afghanistan. Currently, there is no information available on agricultural activities and level of effluent discharge into the Helmand River in Afghanistan. Previous studies have shown that some early-growing aquatic plants have been breeding in the waters of the CN since early 2001 and 2016 [18]. As these evidences confirm the presence of nutrients in the CN, it can be reluctant to consume water by altering water quality. Therefore, the present study was developed to investigate the influencing parameters on algae growth and identify the algae types in the water reservoir. The better understanding on algae types and water quality of CN can aid to find the essential strategies for control and improvement the drinking water quality.

Materials and methods

Background information

Zabol is situated in southeastern Iran and the northeast of Sistan and Baluchestan province with geographical coordinates: 61. 00° – 39. 593°E longitude and 31.000°– 2.00°N latitude with 480 m above the sea level. It is a hot and dry desert climate with a minimum temperature of 7 °C in January and a maximum temperature of 45 °C in July. The annual average evaporation rate is 4 mm and rainfall is mainly observed in winter (The annual average: 51 mm).

Sampling and experimental analysis

The sampling station approach was designed in a way that include the all reservoir well and human activities in Zabol city. Generally, water samples were withdrawn from 5 stations in the depth of 30 cm underwater environments in different month of spring and summer seasons. The samples were taken in 4-l polyethylene containers and immediately transferred to the laboratory at 4 °C. Nitrate and phosphate were analyzed using photometer plain test 7500. Algae were identified as follow: Firstly, samples were passed through a filter (0.45 μm), then the filter was then rinsed with 1 ml of distilled and was placed on a Sedgewick rafter lam counting and in the next, algae was counted with a light microscope (magnification 10). Algae identification was performed using the image guide of standard method [19]. Water transparency was determined using the depth of the Secchi disk (diameter 30 cm). To calculate the environmental population (T) of individual species from the Sedgwick–Rafter counts: If C = number of organisms counted in N squares, and there is a 10×concentration from the original aquatic sample:

$$T=\frac{1000c}{10N}$$ 1

Where T is expressed as the number of organisms (single cell or colonies) per ml of original sample [20] (Fig. 1).

Fig. 1.

Study area and sampling points in the reservoir

Results and discussion

Identification of algae in CN

Algae are widely found in freshwater environments such as lakes, rivers, dams, and in reservoirs where water is less contaminated. Nutrients such as nitrogen and phosphorus discharged from agricultural, municipal, and industrial effluents enter the reservoir and consequently cause algae bloom [21]. Algae are widely found in freshwater. The chemical structure of the reservoir water are influenced by the characteristics of the drainage area such as the geological texture of the area and the basin, the material and type of soil and its constituents, vegetation, type and extent of erosion. Generally, high erodibility in the basin cause possible transfer of minerals and organic matter throughout the basin and accordingly accumulate within the water reservoir [22].

Table 1 shows the species of algae identified in the well water samples within the spring and summer seasons. In total, 226 algae were found in the CN. The highest amount of algae has corresponded to Green algae, Flagellate algae, Cyanobacteria, and Diatoms, respectively, of which, 146 and 79 algae were identified in spring and in summer, respectively. Furthermore, the highest and the lowest amount of algae was corresponded to botryococcus and lyngbya, respectively.

Table 1.

Types of algae identified in spring and summer in the CN reservoirs

Type of algae	species	spring	summer	Total
Cyanobacteria (Blue-Green algae)	anabaena	22	4	26
	lyngbya	7	2	9
Green algae	closterium	18	8	28
	Oocystis	14	5	19
	botryococcus	31	26	57
	hildenbrandia	6	3	9
Diatoms	cyclotella	8	5	12
	tabellaria	13	9	22
Flagellate algae	ceratium	18	11	29
	chlamydomonas	9	6	15

A possible reason for difference in the number of algae identified is related to algae growth which are affected by competition between different algal groups, predation in the food chain, the degree of pollution, and the flow characteristics of the water [23]. As two species of green-blue algae have been identified; therefore, they could be the effective factors in changing the water quality taste of wells. The previous studies revealed that taste and odor generating factors in Iranian and world reservoirs are related to the algae. Davies et al. (2004) illustrated that there is a strong positive correlation between average TOC and average flavor profile analysis (FPA) intensity in drinking water tanks and lakes [24].

Evaluation the nitrate and phosphate

Agricultural drains containing insecticides, fertilizers, industrial effluents, runoff and sewage effluents are discharged to environmental aqueous with large amounts of mineral ions such as nitrate phosphate and ammonia. In warm seasons, phosphate concentration is important for algae bloom phenomena [25]. The phosphorus entering the water leads to changes in the quantity and quality of biological and non-biological elements of nutrients and can lead to algal blooms and oxygen deficiency [26].

Phosphorus plays a crucial role in metabolic and biological activities. Algae with the phosphatase enzyme can hydrolyze P and then absorb P-rich substances outside their cells. However, algae’s ability to promote this process is varied, on the other hand, organic phosphate cannot be readily consumed compared to inorganic phosphate (orthophosphate) [27]. Phosphates are the only inorganic source of phosphorus; the optimum concentration of these compounds for algae growth is 0.15–15 mg/L. Nitrogen is also an essential nutrient for algae growth. However, unlike phosphorus, it is very difficult to control the sources of nitrogen production because nitrogen directly through the air Different forms are absorbed and dissolved in the water body. In the water sources containing high phosphorus, phytoplankton growth leads to reduction the nitrogen levels and limits growth to nitrogen [28]. The occurrence of algal bloom is related to the low nitrogen to phosphorus ratio (TN:TP). When TN: TP ratio in the water is higher than 14 (>14:1) (by mass), N may exist in surplus and P often limits the algal growth. On the other hand, When N: P is < 14, N plays as the limiting factor. It should be noted that nutrient bioavailability is different for algal taxa which affect the N: P of algal growth [5]. The minimum phosphorus concentration needed for algae growth and blooming in the summer is estimated to be 0.005 to 0.01 mg/L [29].

Table 2 shows the average phosphate in spring (0.034 mg/L) and summer (0.028 mg/L). As a result, it has significant effect on the growth of algae due to the phosphorus load. Jin X (1995) Cited total nitrogen levels >0.2 mg/L and total phosphorus >0.02 mg/L in dams as critical values for nutrition [30]. Results obtained from the location of sampling station No. 2 was the discharge site of agricultural wastewater in the CN. As shown in Figs. 2 and 3, the amount of nitrate at station 4 has an increasing trend compared to other stations. In addition, the phosphate content in this site is clearly increasing compared to other stations. The results of this study are consistent in previous studies; high level of nitrate and phosphate concentrations in are reported in the CN [31]. In a study conducted by Dzialowski AR et al. (2009) focusing on hypertrophic reservoirs in Kansas, they proposed that reducing phosphorus has been identified as the main way of eliminating taste and odor [32]. Burford et al. (2007) reported that the percentage of algal cover in the watershed, reservoir volume, and watershed were all significantly correlated with the concentration of algae cells and total nitrogen. Total phosphorus was only correlated with forest cover ratio in the field, indicating that the volume and depth of the reservoir on total phosphorus were less important than the concentration of algal cells or total nitrogen. These results also indicate that the pattern of the watershed and reservoir characteristics such as volume and depth of water have a measurable effect on the type of algal blooms in the reservoirs [33].

Table 2.

average qualitative parameters affecting the algae growth in spring and summer

algae	Number identified		NO3 (mg/L)		PO4(mg/L)		PH		TEMP
	spring	summer	spring	summer	spring	summer	spring	summer	spring	summer
anabaena	22	4	9	19	0.05	0.011	8.6	8.5	22	31
lyngbya	6	2	8	18	0.04	0	8.5	8.3	22	28
closterium	18	8	8	23	0.04	0	8.5	8.3	21	27
Oocystis	14	5	12	19	0.02	0.018	8.5	8.3	22	26
botryococcus	31	26	13	13	0.01	0.017	8.7	8.3	25	24
hildenbrandia	6	3	10	11	0.03	0.021	8.6	8.4	25	26
cyclotella	8	5	9.5	10	0.05	0.022	8.5	8.6	24	24
tabellaria	13	9	11	8	0.02	0.001	8.3	8.5	26	21
ceratium	18	11	6	5	0.01	0	8.5	8.4	27	20
chlamydomonas	9	6	5	8	0	0	8.4	8.4	25	20

Fig. 2.

Nitrate concentration during the sampling period (spring and summer)

Fig. 3.

Phosphorus concentration during the sampling period (spring and summer)

Physicochemical parameters affecting algae growth in the reservoir

Temperature and pH

Table 3 shows that the mean temperature in spring and summer seasons were observed to be 23.9 (23.9 ±2) and 24.7 (24.7 ± 6.3 °C). In addition, pH values for samples taken in spring and summer seasons were found to be 8.5 (8.5 ±0.1) and 8.4 (8.4 ±0.1), respectively. pH depends on many factors: water-soluble materials, which can be attributed to the types and amount of erosion and bedding materials upstream [34]. pH affects the solubility of nutrients and the forms of nutrients in the water and ultimately the availability of these substances to phytopalcones and more precisely the dominant algae species [35]. Different pH values lead to the growth of different types of algae. At low pH (increased by CO₂) makes green algae have a more competitive coexistence with green-blue algae. Under all conditions, the soluble phosphorus form is directly related to the pH of the water. At pH 6–7, phosphorus is the easiest and best available nutrient for the algae [36]. Acceptable pH values for water quality assessment by the world health organization range from 6.5 to 8.5 [37]. Results obtained from the present study showed that the mean value of pH for spring and summer is 8.4, indicating the pH of CN is suitable for algae growth. The optimum temperature for algae growth is >15 °C and even >20 °C for many cyanobacteria species [38]. Moreover, some studies revealed that a temperature of 25 °C is the minimum temperature required for the maximum growth of most cyanobacteria [21]. Therefore, the mean temperature in both seasons (>20 °C), the temperature is suitable for the growth of algae, especially cyanobacteria in the wells.

Table 3.

Physicochemical parameters affecting algae growth in the CN reservoirs

Physicochemical parameters	spring	summer
Temperature(c)	23.9±2	24.7±3.6
pH	8.5±0.1	8.4±0.1
Secchi(m)	96.16±31.02	119.83±19.28

Depth of Secchi disk

The depth of the Secchi disk partly determines the quality of the water, both aesthetically and visually [22]. According to Table 3, the mean Secchi disks in spring and summer were found to be 96.16 m and 119.83 m, respectively. As a result, the reservoir has poor transparency in terms of algal growth. As the CN reservoir is not in the proper range due to the measurement of the qualitative parameters indicating the growth of the algae, Therefore, other factors, including flood entering into the reservoir, can be considered as one of the factors affecting reservoir opacity.

Algae are of great importance in water reservoirs. They are appropriate indicators to determine water quality and aquatic populations that can provide appropriate responses to environmental challenges as bio-monitoring. In this work, some main parameters affecting the growth of algae were studied. It can help to find the necessary strategies for their control and improvement of drinking water quality. Due to the growth of algae in the CN reservoirs, as well as the presence of phosphate and nitrate, indicates reservoir contamination. Moreover, the presence of cyanobacteria in the reservoir reduced the quality of drinking water; the taste and virtually doubles the water consumption for the consumer. Depending on the amount of water transparency (Secchi disk), the reservoir water is atrophic. Therefore, eutrophication is likely to occur if no action is taken to control and prevent agricultural, urban, industrial effluent from entering the reservoir which leads to algal blooms and increases the cost of water treatment. It is worth to say that surface water quality such as lakes could be classified by a few well known water quality indexes [39].

Compliance with ethical standards

Conflict of interest

The author declares that they have no conflict of interest.