Characterization of Lake Kivu Water Chemistry and Its Environmental Impacts

*Francois Hategekimana, Theophile Mugerwa, Digne Edmond Rwabuhungu Rwatangabo and Young-Seog Kim*

## **Abstract**

Among the world's lakes, Lake Kivu, a rift lake in the western branch of the Eastern African Rift System, has significant reserves of dissolved chemicals. However, no research has been done on their vertical variation in lake and how they affect the environment. This proposed chapter will review earlier research to better understand the origin of Lake Kivu's chemical composition and its effects on the aquatic environment. Water samples were collected using Niskin bottles at various depths, as well as in various locations away from Nyamyumba hot spring sources. Hach kits and procedures were used to conduct chemical analyses on water samples. This study found that the majority of chemical concentrations rise with depth, primarily as a result of the deposition of organic matter. The sewage water from residential buildings, hospitals, runoff from agricultural activities, and rock-water interaction through dissolution process are the possible sources of chemicals discovered in Lake Kivu water. The levels of chemicals in the water of Lake Kivu at this time are less polluting and damaging to the aquatic environment. Therefore, it is important to implement a continuous monitoring strategy to stop eutrophication and other diseases linked to water pollution in humans.

**Keywords:** Lake Kivu, chemicals, water stratification, environment, eutrophication

## **1. Introduction**

Over the last few decades, global awareness of lake eutrophication and aquatic ecological degradation has grown. The process of eutrophication refers to the change in the chemical properties of water caused by the accumulation of excess nutrients such as nitrogen and phosphorus. In this process, phytoplankton and other microorganisms are rapidly produced leading to the deterioration of water quality which is detrimental to aquatic ecology [1–3].

Water body chemistry results mainly from the interplay between diverse hydrological, geochemical, and biological processes controlled by either natural or anthropogenic factors such as: lithology, climate, vegetation, relief, agricultural activities, and domestic or industrial discharge [4–7].

In this research, Lake Kivu which is a rift lake located in the western branch of the East African Rift System was considered (**Figure 1**). Like other lakes, Lake Kivu contains marine organisms (e.g. fishes) that should be environmentally protected through continuous monitoring of its water chemistry.

It is well known that the chemistry of water bodies varies with depth [8]. Numerous studies (e.g., [9–11]) were conducted to comprehend the chemistry of Lake Kivu while only focusing on surface chemistry; however, none of these studies ever made the connection between the vertical variation in chemistry and environmental pollution.

The water of East African rift lakes contains large amounts of dissolved gases such as carbon dioxide and methane, especially in Kivu Lake which is located between Rwanda and the Democratic Republic of Congo (DRC) (**Figure 1**). Lake Kivu is one of the largest carbon dioxide and methane gas reservoirs on earth [12, 13]. It was observed that the amount of CO2 and CH4 dissolved phase in Lake Kivu is 300 km3 and 55 km3 at standard temperature and pressure (gas volume at 0°C and 1 atm [14]. According to ref. [15], Methane is formed in three ways: (1) mantle-derived, (2) thermal maturation of organic matter, and (3) bacterial degradation of organic matter at the shallow depths. In the case of methane in Lake Kivu water column, the dominant methane-forming process is bacteria-mediated methanogenesis of CO2 which is originated from volcanic activities.

Other than those gases, Lake Kivu contains several other chemicals including silica, phosphate, iron, sulfide, and ammonia which vary with depth [8, 9, 16]. Lake Kivu water is stratified where the divide between mixolimnion and monomolimnion occurs at a depth of around ~65 m [17] and ~ 45 m [8], respectively.

Lake Kivu waters are drained by different fluid sources and/or biochemical processes controlling water chemistry (i.e., water-rock interactions, bacterial activity) that is not homogeneously distributed all over the entire lake [8, 18, 19]. Furthermore, Hategekimana et al. [16] studied the chemistry of Nyamyumba hot springs located

#### **Figure 1.**

*Location map of Rwanda: (a) a map of Africa for Rwanda localization; (b) an elevation map of Rwanda in meters. The study area is shown by a blue rectangle. DRC stands for the Democratic Republic of Congo.*

along the shores of Lake Kivu and interpreted that there is a contribution of these hot springs to the chemistry of Lake Kivu water.

In this chapter, we reviewed earlier research findings from Lake Kivu to identify the causes of its water chemistry while considering vertical chemistry variations and their corresponding environmental issues, particularly for aquatic and human life.

## **2. Geological, geochemical, and hydrogeological background of Lake Kivu**

The lake's surface area is 2370 km<sup>2</sup> , and its drainage basin is 4940 km2 excluding the lake [20]. The majority of the drainage basin is made up of a river-active region (4255 km2 ) that is dominated by humic ferralsols in the southwest, humic acrisols in the east, and haplic acrisols in the northwest and southeast [21].

Lake Kivu is one of the rift lakes located in the western branch of the East African Rift System. Different geodynamic processes, such as faulting and magmatism, influenced and contributed to the formation of the lake and various structures along Lake Kivu's margin (**Figure 1**).

The East African Rift System resulted from two mantle plumes beneath the Afar and Kenyan Plateau [22–24]. The tectonic uplift and an extension led to the creation of the East African Rift (EAR) [25], the best example of an active rift system. The plateaus are dynamically supported by the convective activity under the asthenosphere [26], providing heat transfer for partial melting of the lithospheric mantle. All of these parameters make the East Africa Rift System (EARS) a very good potential area for geothermal resources [27]. The western branch of the East African Rift System has a limited and localized volcanic product with a more diverse chemistry than the eastern branch.

The Kivu rift valley is composed of deep lacustrine basins and structural heights which are overlain by volcanic rocks [28] indicating the presence of a mantle plume beneath the lithosphere. The northern basin of Lake Kivu contains about 0.5 km of sediments which overlie a basement believed to be of crystalline rocks of Precambrian age [9].

Lake Kivu's deep waters are known to have high concentrations of carbon dioxide and methane. A trace amount of nitrogen is present at all depths, and the amount of dissolved oxygen decreases with depth. The pH of oxygenated waters is around 9, while that of anoxic waters is below 7.

Furthermore, the distribution of principal cations shows that salt content increases with water depth, and they are at a relatively uniform concentration level at a given depth in an independent geographical location [9].

## **3. Material and methods**

Seven water samples were collected from the surface to a depth of 390 meters, with at depths of (0 m, 40 m, 90 m, 240 m, 290 m, 340 m, 390 m) using Niskin bottles suspended on a calibrated cord in Lake Kivu near Gisenyi city (**Figure 1**), with the assistance of a Kilindi boat. Other 14 samples were collected at different locations from Hot spring sources to Lake Kivu for the comparison of the chemistry of Hot springs and Lake Kivu waters.

Conductivity, temperature, and depth (CTD) sonde data were also gathered. Utilizing Hatch kits, water samples were examined in the lab of the Lake Kivu Monitoring Program.

With increasing salinity, conductivity—a metric of water's capacity to conduct electricity—increases [18]. Using a CTD Sonde, the conductivity of water samples was assessed in seven different locations. Comparing the dissolved ions and factors facilitating the dissolution at various locations is made easier by measuring the conductivity at each location.

Using Hach test kits and procedures, the concentrations of sulfate, iron, ammonia, silica, and phosphate as well as the alkalinity of the water were determined in water samples.

The silico-molybdate method (silica, high range [0–75.0 mg/L]) was used to determine the silica content. The samples were warmed to room temperature before being analyzed to determine the silica concentration. The silica standard solution contained 50 mg/L of SiO2. Under acidic conditions, the sample's silica and phosphate reacted with the molybdate ion to form yellow silico-molybdic acid complexes and phosphormolybdic acid complexes. In order to dissolve the phosphate complexes, citric acid was added. The remaining yellow complex was measured to obtain the silica content.

Furthermore, a digital titrator was used to measure the alkalinity, or the water's ability to resist acidification. The sample bottles for phosphate analysis, in contrast to other chemicals, were first cleaned with a 1:1 hydrochloric acid solution and rinsed with deionized water. The mixing bottle was filled with the sample. One pillow of phenolphthalein indicator powder was added, then blended. Drops of a standard solution of sulfuric acid, 0.035 N, were added. After each drop, the solution was thoroughly blended to achieve colorlessness from pink. The alkalinity of phenolphthalein was calculated as CaCO3 by multiplying the number of drops until the color changed by 20. One pillow of bromocresol green-methyl red powder was added, and the mixture was stirred. Drops of a standard solution of sulfuric acid, 0.035 N, were added. After every drop, the solution was thoroughly mixed once more, and drops continued to be added until the color changed from green to pink. The total number of drops for the whole procedure was calculated and multiplied by 20 to obtain the total alkalinity (methyl orange) as CaCO3.

Using the method described above, a standard solution containing 500 mg/L of CaCO3 was used. Water samples were collected and stored in plastic containers that had been acid-cleaned before the iron concentration was measured. No acid was added because the water samples were analyzed right away. The analysis made use of the Ferro Ver method for iron (0–3.00 mg/L). By adding 100 mg/L of Fe to 100 mL of deionized water and diluting 1.00 mL of iron standard solution, 1.0 mg/L of iron standard solution was prepared. The test was then conducted using the AccuVac Ampuls method.

Phosphorus concentration was determined by adding 25 mL of sample to a 25 mL sample cell. A 1 mL calibrated dropper was used to add the molybdate reagent. The addition of 1 mL of the amino acid reagent solution came next. The reaction took 10 minutes to complete and the sample was thoroughly mixed. The sample was added to the sample cell in a volume of 25 mL. The timer beeped, and mg/L PO4 was shown. The cell holder was filled with the blank. The instrument cap was placed over the sample cell, and after pressing "zero," the cursor moved to the right and the reading of 0.0 mg/L PO4 appeared. The prepared sample was put into the cell holder, then the instrument cap was put on top of it. After selecting "read," the cursor shifted to the right and the sample's final concentration was shown. To determine the concentration of each sample, this was finished. Reactive (0–30.0 mg/L PO4 3) method was used for phosphorus analysis. A 50 mg/L as PO4 3 phosphate standard solution was pipetted into a 50 mL volumetric flask to create a 10.0 mg/L phosphate standard. Deionized

### *Characterization of Lake Kivu Water Chemistry and Its Environmental Impacts DOI: http://dx.doi.org/10.5772/intechopen.112625*

water was used to dilute the sample to the desired volume. The procedure was carried out as described above, and a concentration of 10 mg/L was obtained.

By adding 5 mL of the sample to two tubes, the concentration of ammonia was also calculated. The left opening of the color comparator box received one tube, and the second tube received the ammonia salicylate reagent powder pillow. The powder was shaken out of the tube completely. An ammonia cyanurate reagent powder pillow was added after a short while, shaken, and after 15 minutes, a green color appeared. In the color comparator box, which was held up in front of the light source, the second tube was placed. By rotating the color disc, color matching was discovered, and the outcome was displayed in the scale window. Ammonium ions (NH4 + ) and unionized ammonia (NH3) are the two different forms of ammonia that are found in water.

So, this method measures both NH4 + and NH3 as ammonia nitrogen (NH3–N). One mg/L NH3–N of nitrogen ammonia standard solution was used. The mg/L NH3 in the sample was calculated as follows: • mg/L NH3 = ((mg/L NH3–N × percent NH3 of water sample at a given temperature and pH) ÷ 100) × 1.2 [29].

To calculate the salinity of the water samples, a CDC401 conductivity probe was employed. The probe was then dried with a lint-free cloth after being rinsed with deionized water. The shroud was put in place. The sensor was fully inserted into the sample when the probe was inserted. Shaking the probe removed air bubbles. It was shaken, then stirred while the salinity was measured.

Furthermore, the Sulfa-Ver 4 method for sulfate (0–70 mg/L) was used to complete the sulfate analysis. The method was initially calibrated using a 50 mg/L sulfate standard solution. Pipetting 1 mL of a Pour Rite ampule standard for sulfate (2500 mg/L) into a 50 mL volumetric flask produced the standard solution. Deionized water was used to dilute the sample. In this procedure, barium sulfate precipitate is created when sulfate ions react with the metal in Sulfa-Ver 4, a sulfate reagent. The stabilizing agent in Sulfa-Ver 4 holds the suspended precipitates, and the turbidity formed is proportional to the sulfate concentration.

## **4. Results and discussion**

## **4.1 Lake Kivu water chemistry variation with depth**

Hategekimana et al. [8] concluded that Lake Kivu water chemistry varies significantly along the depth profile. Lake Kivu exhibits a unique vertical density stratification that is driven by dissolved gasses and the influx of saline groundwater. Except for anaerobic microbial processes, biologic activity only occurs in the mixoliminion (upper 60–65 m of the lake) [8, 17].

According to Hategekimana et al. [8], Lake Kivu water chemistry varies significantly along the depth profile.

Phosphorus concentration range from 0 to 3 mg/L in Lake Kivu. It shows an abrupt change at around the depth of 45 m (**Figure 2a**). This concentration also changes at 240 m deep to the constant value of 3 mg/L. According to ref. [30], phosphate concentration between 40 and 120 mg/L can lead to environmental pollution. The concentrations recorded in this study are below that range indicating that Lake Kivu water is less prone to pollution.

Like other chemicals, silica concentration also shows a constant value up to 45 m deep. In the deeper part, silica content increased downward up to the depth of 390 m

**Figure 2.**

*The variation of Lake Kivu water chemistry with depth (modified from [8]).*

(**Figure 2b**). The increase in silica concentration could be probably related to the sinking of dead diatoms [31].

Iron concentration in Lake Kivu water decreases with depth up to 90 m deep as shown in **Figure 2**. The concentration then increased downward up to the depth of 390 m (**Figure 2c**).

## *Characterization of Lake Kivu Water Chemistry and Its Environmental Impacts DOI: http://dx.doi.org/10.5772/intechopen.112625*

Sulfide and sulfate concentrations showed a decrease and increase respectively in the range from 0 to 45 m deep. This increase in sulfate concentration can be explained as the result of sulfide oxidation in an oxic environment. In contrast, the concentration of sulfate decreases in the region below 100 m. This reduction of sulfate increases the concentration of sulfide in Lake water (**Figure 2d** and **f**). This change in concentrations can be used to determine the boundary between oxic and anoxic zones in Lake Kivu which is estimated at 45 m deep also consistent with the boundary set by Roland et al. [32].

Up to 45 m from the water surface, the ammonia concentration is 0 mg/L. The concentration suddenly increased with depth up to 100 m. Ammonia concentration is constant up to 390 m deep (**Figure 2e**). The increase in ammonia could be probably related to the deposition of organic matter in the deeper part.

The alkalinity increases with depth (**Figure 2g**) indicating the ability of Lake Kivu water to withstand the acidity. The alkalinity in Lake Kivu is in the range recommended by WHO [16, 33].

The concentration of dissolved oxygen reduces with depth but is still above the critical level of 3 mg/L for fish (**Figure 3a**); [34]. The decrease in dissolved oxygen is the result of bacterial oxygen consumption during the decomposition of organic substances including from public sewage and agricultural farms [10, 34].

Conductivity also increases with depth (**Figure 3b**). The increase in conductivity in Lake Kivu is probably related to the increased salinity [16]. The pH in **Figure 3c** indicated a decrease from 10 at the surface and tends to be neutral which is better for swimming.

#### **4.2 The source of Lake Kivu water chemistry**

This research disclosed that Lake Kivu water chemistry is mostly derived from sewage water from resident houses, hospitals, runoff from farming activities, and water-rock interaction through the dissolution process [8, 16].

In fact, Lake Kivu is located in the vicinity of two densely populated cities; Gisenyi (Rwanda) and Goma (DRC). Therefore, the chemistry of Lake Kivu water could be associated with the urbanization in those two cities.

A significant amount of wastewater is disposed of without proper treatment as a result of urbanization. To increase agricultural yields, farming activities also need more fertilizers. In addition, rivers carry domestic sewage and rainwater from agricultural fields to Lake Kivu. As a result, chemicals like nitrogen and phosphorus are present in higher concentrations in water. According to Ref. [35], higher concentrations worsen the aquatic environment and impair lakes' functionality, causing eutrophication.

Additionally, it was discovered that because the water from Nyamyumba Hot Springs is directly discharged into Lake Kivu, it affects the chemistry of the Lake (**Figure 4**) [16].

The higher concentration of silica (9.2 mg/L) found closer to the shoreline is probably the result of an influx of sediment from weathered bedrock (**Figure 2b**), especially close to stream and river outlets. Due to the dissolution of diatoms below the photic zone and the precipitation of calcite after it has been dissolved in water, deeper waters have higher concentrations of silica than surface waters [16].

Dissolved oxygen levels show a decrease near the water's surface that may be caused by photosynthetic processes (**Figure 3a**).

#### **Figure 4.**

*The comparison of chemical concentrations in water from Lake Kivu and hot springs was adapted from [16].*

### *Characterization of Lake Kivu Water Chemistry and Its Environmental Impacts DOI: http://dx.doi.org/10.5772/intechopen.112625*

With the inflow of saline groundwater, the conductivity, which reflects the salinity of the water, is increasing downward (**Figure 3b**). Saline groundwater is most likely alkaline, and alkalinity rises in the monimolimnion most likely because of calcium carbonate precipitation in the upper levels of the water column and mixolimnion dissolution (**Figure 3b**). Due to phytoplankton deposition in deep waters, the concentration of phosphorus typically rises with depth as depicted in **Figure 1**.

**Figure 3** shows that as the age of deep waters increases, iron concentrations at a depth of about 100 m decrease. Due to the remineralization of iron, the concentration rises in the intermediate zone. After that, iron is taken out of the water and added to the sediments, where it cannot mix back in and cause replenishment. The main factor contributing to the increase in ammonia in the lake water may be the use of fertilizers, which cause runoff into waterways from farmlands (**Figure 2e**). Alkalinity was used to calculate the partial pressure of CO2, but it is currently difficult to evaluate how accurate this calculation was.

The CO2 flux calculation indicates that CO2 moves upward in the water column, with the exception of the deepest measurements where it is more likely to move downward from 340 to 390 m.

The data collected by Schmidt in February 2004 and June 2018 differ from one another. At greater depths, the change is typically significant.

The pH level of lake water rises as a result of higher algal and plant growth that is influenced by rising temperatures or excess nutrients from farmland runoff and wastewater streams. The pH drops downward as the temperature rises, and the presence of carbon dioxide increases acidity, which in turn causes the pH to drop.

The sulfide concentration suggests that phytoplankton numbers are declining, temperatures are rising [36], there is an increase in organic matter in the sediment [37], the sediments are iron-poor [38], and the water is deeper and has less oxygen. Due to the implementation of control measures, the concentration of sulfide decreased between 2004 and 2018 and was a result of the slower organic matter sedimentation rate.

Over time, the phosphate concentration is lowering. This is because of the managed runoff, measures taken to keep livestock out of water sources, and a manure management plan.

When a significant amount of wastewater from homes and hospitals is dumped directly into a lake, it adds chemicals to the lake's water body, like phosphate and nitrates. Additionally, the use of fertilizers causes agricultural runoff, which raises the phosphate concentration in water. According to ref. [39], phosphorus increases the productivity of plankton and aquatic plants, which in turn feed larger organisms like zooplankton, fish, humans, and other mammals. The aquatic life that consumes phytoplankton and zooplankton will be greatly impacted by the gradual decrease in phosphate concentration. Some organisms will vanish at a later time.

## **4.3 Environmental impacts**

According to this study, the concentration of the majority of chemicals in Lake Kivu water rises with depth. Aquatic life is impacted by the increased chemicals [8]. The increased pollutants in the water cause an overabundance of phytoplankton, which causes eutrophication. According to Ref. [8], when nitrogen and phosphorus levels rise in water, algae and other microorganisms grow erratically, which reduces the amount of oxygen in the water. This buildup of nutrients is essential for the eutrophication of Lake water. In order to prevent eutrophication in Lake Kivu, consistent monitoring should be considered.

The chemical concentration levels in Lake Kivu are lower than those in hot springs [16]. Because the chemical concentrations were below the WHO-recommended

ranges, they concluded that swimming in hot springs water was safe. As a result, swimming is also safe in Lake Kivu.

## **5. Conclusions**

In Lake Kivu, where water chemistry varies greatly with depth, the mixolimnion and monolimnion boundary was found at a depth of about 40 meters, which is 20 meters closer compared to the previous researches. Hospitals and residential wastewater both add nitrates and sulfates to Lake Kivu's water supply. Additionally, farmlands contribute to an increase in the concentration of phosphates in water through water runoff. Increased chemical concentrations encourage the growth of plankton and other marine organisms, which can cause eutrophication, the depletion of available oxygen, and adverse effects on aquatic life. In order to safeguard Lake Kivu's aquatic ecosystem, we advise the relevant organizations to continue monitoring the lake's chemical state.

## **Acknowledgements**

We wish to express our gratitude to the Geological Structures and Geo-Hazard Research Lab (GSGR), Department of Earth and Environmental Sciences, Pukyong National University, for supporting this research and We thank all members of the laboratory for their assistance with data analysis and interpretation.

## **Conflict of interest**

The authors declare no conflict of interest.

## **Author details**

Francois Hategekimana1,2 \*, Theophile Mugerwa1 , Digne Edmond Rwabuhungu Rwatangabo1 and Young-Seog Kim2

1 Departments of Geology, College of Science and Technology, University of Rwanda, Kigali, Rwanda

2 Geological Structures and Geo-Hazard Research Lab, Department of Earth and Environmental Sciences, Pukyong National University, Busan, Korea

\*Address all correspondence to: francoishate@pukyong.ac.kr

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Characterization of Lake Kivu Water Chemistry and Its Environmental Impacts DOI: http://dx.doi.org/10.5772/intechopen.112625*

## **References**

[1] Organization for Economic Co-Operation and Development (OECD). Eutrophication of waters: Monitoring, assessment and control. In: Final Report. OECD Cooperative Program on Monitoring of Inland Waters (Eutrophication Control, Environment Directorate). Paris: OECD; 1982

[2] Nixon SW. Eutrophication and the macroscope. In: Eutrophication in Coastal Ecosystems: Towards better understanding and management strategies Selected Papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20-23 June 2006, Nyborg, Denmark. Netherlands: Springer; 2009. pp. 5-19

[3] van Beusekom JE. Eutrophication. Handbook on Marine Environment Protection: Science, Impacts and Sustainable Management. 2018:429-445

[4] Karikari AY, Bernasko JK, Bosque EKA. Hamilton an assessment of water quality of Angaw River in southern – Eastern coastal plains of Ghana. West African Journal of Applied Ecology. 2007;**2**:77-87

[5] Li S, Gu S, Tan X, Zhang Q. Water quality in the upper Han River basin, China: The impacts of land use/ land cover in riparian buffer zone. Journal of Hazardous Materials. 2009;**165**:317-324. DOI: 10.1016/j. jhazmat.2008.09.123

[6] Viers J, Dupré B, Gaillardet J. Chemical composition of suspended sediments in World Rivers: New insights from a new database. Science Total Environment. 2009;**407**:853-868. DOI: 10.1016/j.scitotenv.2008.09.053

[7] Rezende-Filho AT, Valles V, Furian S, Oliveira CM, Ouardi J, Barbiero L. Impacts of lithological and anthropogenic factors affecting water chemistry in the Upper Paraguay River Basin. Journal of Environmental Quality. 2015;**44**(6):1832-1842

[8] Hategekimana F, Ndikuryayo JD, Habimana E, Mugerwa T, Christian K, Digne R. Lake Kivu water chemistry variation with depth over time, Northwestern Rwanda. Rwanda Journal of Engineering, Science, Technology and Environment. 2020;**3**(1):1-20

[9] Degens ET, von Herzen RP, Wong HK, Deuser WG, Jannasch HW. Lake Kivu: Structure, chemistry and biology of an East African rift lake. Geologische Rundschau. 1973;**62**:245-277

[10] Olapade OJ, Omitoyin BO. Anthropogenic pollution impact on physico-chemical characteristics of Lake Kivu, Rwanda. African Journal of Food, Agriculture, Nutrition and Development. 2012;**12**(5):6517-6536

[11] Ross KA, Gashugi E, Gafasi A, Wüest A, Schmid M. Characterisation of the subaquatic groundwater discharge that maintains the permanent stratification within Lake Kivu, East Africa. PloS One. 2015;**10**(3):e0121217

[12] Tietze K. 1978: Geophysikalische Untersuchung des Kivusees und seiner außergewöhnlichen Methangaslagerstätten.Schichtung, Dynamik und Gasgehalt des Seewassers. Kiel: Universität Kiel

[13] Halbwachs M, Tietze K, Lorke A, Mudaheranwa C. Investigations in Lake Kivu (East Central Africa) after the Nyiragongo eruption of January 2002,

specific study of the impact of the subwater lava inflow on the lake stability. European Community Humanitarian Office. 2002:1-56

[14] Schmid M, Halbwachs M, Wehrli B, Wüest A. Weak mixing in Lake Kivu: New insights indicate increasing risk of uncontrolled gas eruption. Geochemistry, Geophysics, Geosystems. 2005;**6**(7):1-11

[15] Selley RC. Elements of Petroleum Geology. Oxford: Gulf Professional Publishing; 1998

[16] Hategekimana F, Mugerwa T, Nsengiyumva C, Byiringiro FV, Rwatangabo DER. Geochemical characterization of Nyamyumba Hot Springs, Northwest Rwanda. Applied Chemistry. 2022;**2**:247-258. DOI: 10.3390/ appliedchem2040017

[17] Schmid M, Wüest A. Stratification, mixing and transport processes in Lake Kivu. Lake Kivu: Limnology and Biogeochemistry of a Tropical Great Lake; 2012. pp. 13-29

[18] Tassi F, Vaselli O, Montegrossi G, Huertas AD. Water and gas chemistry at Lake Kivu (DRC): Geochemical evidence of vertical and horizontal heterogeneities in a multi basin structure. Geochemistry, Geophysics, Geosystems. 2009;**2009**:10

[19] Gomaa MM. Salinity and water effect on electrical properties of fragile clayey sandstone. Applied Water Science. 2020;**10**:116

[20] Ballatore T. Lake Basins: Topography and Surface Water. Lake Basin Action Network. 2012. Available from: http:// www.lakebasin.org

[21] Muvundja FA, Wüest A, Isumbisho M, Kaningini MB, Pasche N, Rinta P, et al. Modelling Lake Kivu water level variations over the last seven decades. Limnologica. 2014;**47**:21-33

[22] Ebinger C. The active solid earth. In: EGU General Assembly Conference Abstracts. 2016. EPSC2016-5428

[23] Furman T, Bryce J, Rooney T, Hanan B, Yirgu G, Ayalew D. Heads and Tails: 30 Million years of the Afar plume. Vol. 259 No. 1. London: Geological Society Special Publications; 2006. pp. 95-119

[24] Rogers NW, Macdonald R, Fitton JG, George RWW, Smith M, Barreiro BA. Two mantle plumes beneath the East African rift system; Sr, Nd and Pb isotope evidence from Kenya Rift basalts. Earth and Planetary Science Letters. 2000;**176**:387-400

[25] Wood DA. Structure, Paleolimnology and Basin History of the East Kivu Graben, Lake Kivu, Rwanda. Syracuse, NY, USA: Syracuse University; 2014

[26] Ebinger C, Bechtel T, Forsyth D, Bowin C. Effective elastic plate thickness beneath the East African and Afar Plateaux, and dynamic compensation of the uplifts. Journal of Geophysical Research. 1989;**94**:2883-2901

[27] Bahati G, Pang Z, Ármannsson H, Isabirye EM, Kato V. Hydrology and reservoir characteristics of three geothermal systems in western Uganda. Geothermics. 2005;**34**:568-591

[28] Pouclet A, Bellon H, Bram K. The Cenozoic volcanism in the Kivu rift: Assessment of the tectonic setting, geochemistry, and geochronology of the volcanic activity in the South-Kivu and Virunga regions. Journal of African Earth Sciences. 2016;**121**:219-246

[29] Hach. Ammonia Nitrogen Test Kit. 2015. Available online: https://www.

*Characterization of Lake Kivu Water Chemistry and Its Environmental Impacts DOI: http://dx.doi.org/10.5772/intechopen.112625*

hach.com/p-nitrogen-ammonia-test-kitmodel-ni-sa/2428700.DOC326.98.00007 [Accessed: February 28, 2015]

[30] Ajani P, Lee R, Pritchard T, Krogh M. Phytoplankton dynamics at a long-term coastal station off Sydney, Australia. Journal of Coastal Research. 2001;**2001**:60-73

[31] Lewin JC. The dissolution of silica from diatom walls. Geochimica et Cosmochimica Acta. 1961;**21**(3-4):182-198

[32] Roland FA, Darchambeau F, Morana C, Crowe SA, Thamdrup B, Borges AV. Anaerobic methane oxidation in an East African great Lake (Lake Kivu). Biogeosciences Discussions. 2016;**2016**:1-27

[33] World Health Organisation. Guidelines for Drinking Water: World Health Organization Health Criteria and Other Supporting Information. Geneva: WHO; 1998. pp. 62-315

[34] Zdenka S, Lloyd R, Machova J, Vykusova E. Water Quality and Fish Health. Rome: FAO; 1993. p. 59

[35] Le C, Zha Y, Li Y, Sun D, Lu H, Yin B. Eutrophication of lake waters in China: Cost, causes, and control. Environmental Management. 2010;**45**:662-668

[36] Koch MS, Erskine JM. Sulfide as a phytotoxin to the tropical seagrass Thalassia testudinum: Interactions with light, salinity and temperature. Journal of Experimental Marine Biology and Ecology. 2001;**266**(1):81-95

[37] Govers LL, de Brouwer JH, Suykerbuyk W, Bouma TJ, Lamers LP, Smolders AJ, et al. Toxic effects of increased sediment nutrient and organic matter loading on the seagrass Zostera noltii. Aquatic Toxicology. 2014;**155**:253-260

[38] Marbà N, Duarte CM, Holmer M, Calleja ML, Álvarez E, Díaz-Almela E, et al. Sedimentary iron inputs stimulate seagrass (*Posidonia oceanica*) population growth in carbonate sediments. Estuarine, Coastal and Shelf Science. 2008;**76**(3):710-713

[39] Ricklefs RE, Schluter D. Species diversity: Regional and historical influences. In: Ricklefs RE, Schluter D, editors. Species Diversity in Ecological Communities. Chicago: University of Chicago Press; 1993. pp. 350-363

## **Chapter 12**

## Studies on *Xerophilic*, *Acidiphilic*, and *Alkaliphilic Fungi* in Wadi El-Natrun

*Hassan Abdel Motagly Abdel Mougod Gouda, Abdel-Aal Hassan Moubasher, Mady Ahmed Ismail and Nammat Abd el Gowad Hussein*

## **Abstract**

The present study is an unprecedented extensive survey of mycobiota of Wadi El-Natrun depression, Western Desert of Egypt, which is a hypersaline extreme environment. The study was confined to the eight main lakes of theWadi during six seasons in the years 2007/2009. In general, 159 species, in addition to four species varieties assigned to 50 genera, were recovered during the current investigation. The widest spectra of species were recorded in the genera *Aspergillus* (22 species +2 varieties), *Penicillium* (19), *Fusarium* (17), and *Acremonium* (8). The widest spectrum of species was recorded in El Zugm Lake (82 species) while the lowest was in Fasida (51). Also, the control medium contributed the widest spectrum of species (95 species) while 10% NaCl medium had the lowest (46 species), with the wider spectrum also being recorded in winter and spring seasons and the narrowest during summer. Total of 40 isolates of the most commonly encountered species from different sources, lakes, and isolation media were tested for their capabilities of producing cellulase, protease, lipase, phosphatase, xylanase, and pectinase enzymes. Most isolates had the capabilities of producing cellulase (96%), protease (86.8%), lipase (92.3%), and phosphatase (100%) but with different degrees; however, only 3 out of 20 isolates tested were xylanolytic (15%) and only one out of 38 was pectinolytic.

**Keywords:** Wadi El-Natrun, hypersaline, mycobiota, extreme environment, enzymes

## **1. Introduction**

The Wadi El-Natrun, one of the most important alkaline environments, is situated on the western side of the Nile Delta of Egypt and includes some water bodies characterized by high salinity. Wadi El-Natrun climate is dry, has low and very variable rainfall, dry summer, high evaporation, and low humidity. It contains eight principal lakes for a distance of about 30 km; from south to north: Fasida, Umm Risha, Rosetta, Abu Gubara, Hamra, El Zugm, Al Beida, Khadra, and Al Gaar, noting that Abu Gubara and Hamra form one lake in the summer [1]. Extreme environments are populated by groups of fungi that are specifically adapted to these particular

conditions and these are usually referred to as extremophilic fungi. Extremophiles fungi can be grouped according to the conditions in which they thrive into thermophiles and psychrophiles (which grow at the extremes of temperature ranges), acidophiles and alkaliphiles (extremes of pH), halophiles (high salt), barophiles or piezophiles (high pressures), and xerotolerant, which tolerate very low water activity [2, 3]. The active and stable nature of the microbial enzymes lead to their wide-spread use in various industries and applications [2].

## **1.1 Aim of the work**

The study was confined to the eight main lakes of the Wadi during six seasons in the years 2007/2009. The study comprised the following aspects:


## **2. Materials and methods**

## **2.1 A: Collection of samples**

Samples (reclaimed soil, salt crusts, mud, water, and air) were collected during January 2007 – May 2009, from eight lakes (Fasida, Umm-Risha, Rosetta, Hamra, El El Zugm, Al Beida, Khadra, and Al Gaar) of Wadi El-Natrun (depression) region, Egypt.

1.Soil samples were collected randomly from reclaimed soil around the lakes

Mud samples were collected at random from different sites inside and along the shore of lakes.

Salt crust samples were collected at random from mineral formation present along the shores of the Lake.

Water samples were collected in sterile bottles from different sites inside the lake by means sterile bottles.


**Figure 1.**

*Showing the reclaimed soil around Fasida Lake (1) and salt crusts of El El Zugm Lake (2).*

### **2.2 Chemical analysis of soil samples**

**pH value:** A pH meter (Orior Research Model GOHL Digital Ionalyzer) was used for the determination of soil pH. The electrode was immersed directly in the soil suspension with a ratio of 1:5 (w /v) [5].

**Organic matter content (OM %):** A semi-quantitative method was used for the determination of organic matter, which involves the heated destruction of all organic matter in the soil (Astem 2000). OM% is calculated as the difference between the initial and final sample weights divided by the initial sample weight times 100%.

**Total soluble salts (TSS):** The specific electrical conductance was measured in the soil extract using the conductance meter (YSI, model 35). The percentage TSS in the samples was estimated using this equation: % TSS in the dry sample = 0.064 EC extract ratio. The conversion factor to percentage salts (0.064) was fairly applied for solutions extracted from the soil [5].

**Sodium and potassium (Na+ & K<sup>+</sup> )**: Flame photometer method [5], using Carl Zeiss flame photometer, was used for the determination of Na<sup>+</sup> and K<sup>+</sup> cations.

**Carbonate and bicarbonate:** Total carbonate and bicarbonate were determined directly in the soil through hydrochloric acid digestion [4].

**Calcium and magnesium (Ca+2 & Mg+2):** The versene (disodium dihydrogen ethylene diamine tetraacetic acid) titration method as recommended [6] was employed for Ca+2 and Ca+2 + Mg+2 determinations.

**Chloride (Cl):** Soluble chloride was estimated by applying the silver nitrate titration method using potassium chromate as an indicator [4].

#### **2.3 Isolation of fungi**

**From soil, mud, and salt crusts:** The dilution plate method was used to enumerate different fungal species [7] and employed in this laboratory. At least five samples are taken at random from each place, and then the five or more samples from each replication were brought into one composite sample, which was mixed thoroughly several times.

**From the air:** Replicate plates of 9 cm diameter containing sterile agar media (five for each medium type) were exposed to the air for 15 minutes from January 2006–May 2007. The plates were sealed, brought back to the laboratory, then incubated at 28°C for 7–21 days, during which the developing fungi were identified and counted.

## 1.**Medium used for isolation of** *osmophilic* **and** *osmotolerant fungi*

*Czapek Dox agar* supplemented with 40% sucrose was used for isolation of osmophilic and osmotolerant fungi, from all sources investigated.

## 2.**Medium used for isolation of** *halophilic* **and** *halotolerant fungi*

Modified *Czapek Dox agar* medium (in which glucose, 10 g/l, replaced sucrose), supplemented with 10% sodium chloride, was used for isolation of halophilic and halotolerant fungi.

## 3.**Media used for isolation of** *acidiphilic* **and** *aciditolerant fungi*

Modified *Czapek Dox agar* media in which pH was adjusted at four or five using diluted HCl were used for isolation of *acidiphilic* and *aciditolerant fungi*.

## 4.**Media used for isolation of** *alkaliphilic* **and** *alkalitolerant fungi*

Modified *Czapek Dox agar* in which pH was adjusted at 10, 13 using NaOH were used for isolation of *alkaliphilic* and *alkalitolerant fungi*.

## **2.4 Identification of fungi**

The identification of fungal genera and species (purely morphologically based on macroscopic and microscopic features).

## **Enzymatic activities of fungal isolates**

Forty fungal isolates represented by ten species, commonly encountered from different sources at Wadi El-Natrun region, were screened for their abilities to produce six extracellular enzymes on solid media.

## **A: Cellulase production**

Cellulase production was tested on medium as described by [8].

## **B: Protease production**

The fungal proteolytic ability was tested using casein hydrolysis medium [9].

#### **C: Lipase production**

Lipolytic ability of fungal isolates was tested on the medium [10] with slight modification, in which tween 80 (Sorbitan polyoxyethylene monooleate) replaced tween 20.

## **D: Phosphatase production**

The ability of fungal isolates to produce phosphatase enzymes was detected using phosphatase medium [11].

#### **E: Pectinase production**

The method was carried out as described by Hankin et al. [12].

## **F: Xylanase production**

Modified *xylan agar* medium [13].

## **3. Results and discussion**

## **3.1 Chemistry of Wadi El Natrun**

## *3.1.1 Chemical analysis of soil samples collected from around Wadi El Natrun lakes*

From the collective data of soil chemical analysis from the eight lakes investigated, it is obvious that soil samples collected from around Al Gaar lake possessed the highest values of pH (9.05 0.6), moisture content (23.1 11.0), total soluble salts (30.5 16.8), potassium (0.3 0.1), carbonate (0.3 0.03), bicarbonate (0.5 0.03), and chloride (3.6 2.5) compared to those recorded from soil collected from the other 7 lakes of Wadi El-Natrun. On the other hand, other parameters showed their peaks in different lakes, for example, organic matter (2.0 2.4) in El Zugm Lake, calcium (0.2 9.7<sup>10</sup>–<sup>3</sup> ) in Hamra Lake, magnesium (0.04 0.2) in Al Beida, and sodium (11.1 8.4 mg/g) in Umm Risha (**Table 1**) [14].

## **3.2 Chemical analysis of mud samples collected from Wadi El-Natrun lakes**

From the collective data of mud chemical analysis from the eight lakes investigated, it is evident that mud samples collected from Hamra Lake showed the highest levels of pH (9.4 0.3), organic matter (0.7 0.7), sodium (38.3 17.9), carbonate (0.5 0.15), bicarbonate (0.76 0.7), magnesium (0.2 0.3), and chloride (16.4 11.2). On the other hand, other parameters showed their peaks in different lakes, for example, Moisture content (44.7 28.5), potassium (2.3 4.5) in El Zugm Lake, total soluble salts (47.7 26.2) in Fasida, and calcium (0.1) in Al Beida and Fasida (**Table 2**) [14].

## **3.3 Chemical analysis of salt crust samples collected from Wadi El-Natrun lakes**

From the collective data of chemical analysis of the salt crusts collected from the eight lakes investigated, it is obvious that salt samples showed the highest values of moisture content (25.5 19.9) and calcium (0.4 0.4) in El Zugm Lake, of total soluble salts (88.7 10.8), sodium (51.9 21.2), potassium (0.6 0.4) and chloride (20.6 10.4) in Al Gaar, and carbonate (0.5 0.3) and magnesium (0.4 0.02) in Al Beida Lake. On the other hand, other parameters showed their peaks in other lakes, for example, pH (9.8 0.43) in Umm Risha, organic matter (0.6 0.7) in Hamra, and bicarbonate (2.1 2.5) in Khadra (**Table 3**) [14].

## **3.4 Chemical analysis of water samples collected during spring 2007 from Wadi El-Natrun Lakes water**

Chemical analysis revealed that water samples collected from Wadi El-Natrun Lakes were highly alkaline, with pH ranging from 8.4–9.5 and of high levels of total soluble salts, chlorides, sodium, and potassium. Water collected from El-Zugm Lake showed the highest levels of organic matter, sodium, calcium, magnesium, and chlorides among the eight lakes investigated. On the other hand, some parameters showed their peak in other lakes, for example, pH (9.4) and total soluble salts (87%) in Fasida (**Table 4**) [15].

## **4. Fungi in Wadi El-Natrun lakes**

## **4.1 In soil around Wadi El-Natrun**

Soil samples collected from different lakes during different seasons harbored the highest number of genera and species 48 genera, 137 species, and four varieties. The widest spectrum of species was recorded on the control medium (69 species +2 varieties) and the lowest on 10% NaCl medium (36).


#### **Table 1.**

*Chemical analysis from soil samples collected from around Wadi El-Natrun lakes.*


> **Table 2.**

*Chemical analysis of mud samples collected from Wadi El-Natrun lakes.*


**Table 3.** *Chemicalanalysisfromsaltsamples*

 *collected from Wadi El-Natrun*

 *lakes.*


#### **Table 4.**

*Chemical analysis of water samples collected from Wadi El-Natrun lakes.*

The genera *Aspergillus*, *Fusarium, Penicillium,* and *Emericella* were the most dominant with high proportions of propagules being recorded on all isolation media; however, *Stachybotrys* was also common but was not encountered on 10% NaCl, *Eurotium* was common on 40% sucrose and 10% NaCl media and *Acremonium* was common on alkaline media only.

Of *Aspergillus, Aspergillus terreus* followed by *A. niger*, *Aspergillus flavus,* and *A. fumigatus* gave the highest counts and frequencies on all isolation media; however, some other aspergilli were dominant on both acidic and alkaline media (*A. sydowii* and *A. ustus*), on 10% NaCl (*A. carneus* and *A. sydowii*), on 40% sucrose (*A. sydowii*), while *A. ochraceus* was dominant on the control medium as well as the salt and alkaline media.

Other most commonly encountered species comprised *Emericella nidulans*, *E. quadrilineata*, *Fusarium solani*, *Penicillium puberulum*, and *Acremonium furcatum*. On the other hand, *F. subglutinans*, *Penicillium chrysogenum*, and *Stachybotrys chartarum* were absent in NaCl medium, and *Acremonium strictum* was absent in 40% sucrose agar medium only.

It is worth mentioning that six out of the seven *Acremonium* species recorded from soil were isolated on the alkaline media with more propagules than on the other five isolation media used, however, five species were recorded on acidic media, two on 10% NaCl, and only one on 40% sucrose. This implies that this fungus prefers alkaline media rather than other media.

1.The current results show that *Acremonium fusidioides*, *Acrophialophora fusispora*, *Aspergillus deflectus*, *Cladosporium oxysporum*, *Cochliobolus tuberculatus*, *Curvularia penniseti*, *Eurotium amstelodami*, *E. repens*, *Fusarium nygamai*, *Gliocladium solani*, *Humicola insolens*, *Monodictys castaneae*, and *Scopulariopsis brevicaulis* were isolated from soil on one or both acidic media but not on alkaline media.

Moreover, some species could be isolated on medium of pH 10 (*Acremonium blochii*, *Microdochium nivale*, *Fusarium lateritium*, *Penicillium variabile*, *Mucor*

*circinelloides*, *Penicillium verrucosum*, *Pseudoallescheria boydii*, *Scytalidium lignicola*, and *Trimmatostroma betulinum*) or pH 13 (*Aspergillus cremeus* and *Microascus trigonosporus*) or on both pHs (*A. hyalinulum*, *A. roseulum* and *Paecilomyces variotii*), however, these species were not isolated on both acidic media (adjusted at pH 5 and pH 4).

Some species were recorded only on NaCl medium namely *Cochliobolus monoceras*, *Scopulariopsis halophilica*, *S. carbonaria*, and *Ulocladium consortiale* or on 40% sucrose medium (*Aspergillus candidus* and *Gliocladium catenulatum*) (**Tables 5** and **6**) [14, 16].

## **4.2 In mud**

Mud samples collected from different lakes during different seasons contributed much narrow spectrum of genera and species (13 and 48) compared to that recorded from soil (48 and 137 + 4 varieties). The widest spectrum of species was recorded on 40% sucrose and medium adjusted at pH 10 (25 species), and the narrowest on 10% NaCl (3).

*Aspergillus* was the most dominant genus possessing the highest propagules (over 75% of the total CFUs) on all isolation media; however, *Penicillium* was also dominant on 40% sucrose, acidic, and alkaline media while *Fusarium* was dominant on 40% sucrose and alkaline media, *Emericella* and *Eurotium* on 40% sucrose and *Acremonium* on alkaline media only.

*Aspergillus* showed its peak in spring 2007 in Al Gaar on all isolation media except on 10% NaCl medium in Fasida Lake.

Of *Aspergillus, A. terreus* followed by *A. fumigatus, A. flavus,* and *A. niger* were the most common on all isolation media; however, some other *Aspergilli* were dominant on the control, acidic and alkaline media (*A. ochraceus*), on 40% sucrose (*A. candidus, A. sydowii*) and on alkaline media (*A. carbonarius*).


## **4.3 In salt crusts**

*Aspergillus* (54.6–86.1% of the total propagules) followed by Penicillium (3.6–6.8%) were the most dominant genera with the highest propagules on all isolation media,







#### **Table 5.**

*Summarized data of fungal taxa recorded from various substrates in different lakes of Wadi El-Natrun.*

however, both were not encountered on 10% NaCl. *Fusarium* and *Emericella* were common on two isolation media (pH 5 and 40% sucrose for *Emericella*, control and 40% sucrose for *Fusarium*) while *Acremonium* was common on alkaline media only.

Of *Aspergillus, A. flavus, A. niger, A. terreus,* and *A. fumigatus* were the most common on all isolation media, however, some other aspergilli were dominant on both acidic and alkaline media (*A. phoenicis*) or on 40% sucrose (*A. sydowii*).


## *Science of Lakes – Multidisciplinary Approach*



## *Science of Lakes – Multidisciplinary Approach*



### *Science of Lakes – Multidisciplinary Approach*


#### **Table 6.**

*Summarized data of fungal taxa recorded on different media Wadi El-Natrun from various substrates.*

Other most commonly encountered species comprised *F. solani* and *P. chrysogenum* on all media but not encountered on 10% NaCl. *P. puberulum* was dominant on all media except the control and 10% NaCl media.

It is worth mentioning that out of five *Acremonium* species (four identified and one unidentified) recorded from salt, four were isolated on alkaline media while only three on the control medium and one was on 40% sucrose medium. *Acremonium* contributed higher propagules on both alkaline media (7.1% and 38.4 of the total CFUs) than on other media.

Some fungal species were recorded on 40% sucrose agar only (*A. candidus*, *Emericella variecolor*, and *F. nivea*), on acidic media (*Aspergillus puniceus*, *Cochliobolus australiensis*, *Fusarium camptoceras*, *Paecilomyces lilacenus*, and *Penicillium crustosum*), or on alkaline media (yeasts, *Cladosporium sphaerospermum*, *P. variotii*, *Scopulariopsis sphaerospora*, and *A. hyalinulum*) but not on other isolation media (**Tables 5** and **6**) [17–19].

### **4.4 In water**

*Aspergillus* and *Acremonium* followed by *Penicillium* were the most dominant genera possessing the highest proportions of propagules on all isolation media except on 10% NaCl. On the other hand, only species of the genera *Scopulariopsis* and *Acremonium* were isolated on 10% NaCl medium.

*Aspergillus* showed its peak in Al Beida during winter 2007 on both acidic and alkaline media while in spring 2007 on control medium (from Khadra Lake) and on 40% sucrose (from El Zugm Lake).

Of *Aspergillus, A. terreus* followed by *A. flavus* and *A. niger* were the most common on all isolation media. On the other hand, *A. ochraceus* was dominant in acidic media only.

Other most commonly encountered species, *P. chrysogenum* and *P. puberulum* were encountered on all media but not on 10% NaCl medium.

Some species were isolated on one medium but not on the others: *S. halophilica* (on 10% NaCl), *E. quadrilineata* (on 40% sucrose), *Staphylotrichum coccosporum* (on medium adjusted at pH 4), and *A. hyalinulum* (on alkaline media) (**Tables 5** and **6**) [15].

### **4.5 In air**

Aeromycobiota were represented by 21genera and 35 species with the widest spectrum of species being recorded on 40% sucrose medium (28) and the lowest on 10% NaCl medium (18).

The dematiaceous hyphomyceteous genera *Cladosporium* and *Alternaria* were the most dominant followed by *Aspergillus* and possessed the highest number of propagules on all isolation media.

Cladosporium cladosporioides, *Alternaria tenuissima*, *A. alternata* followed by *A. flavus*, *A. niger*, and *A. terreus* were the most common in all isolation media.

Other most commonly encountered species were related to dematiaceous hyphomycetes and these are *C. oxysporum, Epicoccum nigrum, S. chartarum,* and *Ulocladium botrytis* on all isolation media. *Stemphylium botryosum* was also dominant in control and 40% sucrose media, but was not encountered in 10% NaCl medium (**Tables 5** and **6**) [17].

## **5. Enzymes produced by the most common fungi**

Total of 40 isolates of the most commonly encountered species from different sources, lakes, and isolation media were tested for their capabilities of producing cellulase, protease, lipase, phosphatase, xylanase, and pectinase enzymes. The following observations could be outlined:

Most isolates had the capabilities of producing cellulase (96%), protease (86.8%), lipase (92.3%), and phosphatase (100%) but with different degrees; however, only

three out of 20 isolates tested were xylanolytic (15%) and only one out of 38 was pectinolytic.

Total of 36 isolates showed high-producing abilities of either phosphatase (27 isolates), lipase (21), cellulase (11), protease (7) and xylanase (2) on different screening media (**Table 7**).

Some of these isolates were high producers for more than one enzyme, on one or more of the screening media.

## **5.1 Of the high cellulase producers**


## **5.2 Of the high protease producers some isolates showed this property on either**


## **5.3 Of the 21 highly lipase-producing strains, some provided this character on**



## **5.4 The high phosphatase production has been proved on one (or more) medium types**


(**Table 7**) [20, 21].



 **7.** *The highly producing isolates for cellulose, protease, lipase, phosphatase, and/or xylanase enzymes on different screening*

 *media.*

**Table**

## **6. Conclusions**

Survey of mycobiota of Wadi El-Natrun depression, western desert of Egypt gave in general, 159 species; in addition, four species varieties assigned to 50 genera were recovered during the current investigation. The widest spectra of species were recorded in the genera *Aspergillus* (22 species +2 varieties), *Penicillium* (19), *Fusarium* (17), and *Acremonium* (8). The widest spectrum of species was recorded in El Zugm Lake (82 species) while the lowest was in Fasida (51). Also, the control medium contributed the widest spectrum of species (95 species) while 10% NaCl medium had the lowest (46 species), with the wider spectrum also being recorded in winter and spring seasons and the narrowest during summer.

## **Author details**

Hassan Abdel Motagly Abdel Mougod Gouda<sup>1</sup> \*, Abdel-Aal Hassan Moubasher2,3, Mady Ahmed Ismail<sup>2</sup> and Nammat Abd el Gowad Hussein<sup>2</sup>

1 Plant Pathology Research Institute, Agricultural Research Center, Giza, Egypt

2 Department of Botany and Microbiology, Faculty of Science, Assiut University, Assiut, Egypt

3 Assiut University Mycological Centre (AUMC), Assiut University, Assiut, Egypt

\*Address all correspondence to: mycologist2010@yahoo.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

## **References**

[1] Zahran MA, Willis AJ. The Vegetation of Egypt. London: Chapman and Hall; 1992. p. 424

[2] Satyanarayana T, Raghukumar C, Shivaji S. Extremophilic microbes: Diversity and perspectives. Current Science. 2005;**89**:1-10

[3] Hendry P. Extremophiles: There's more to life environ. Chem. 2006;**3**:75-76

[4] Johnson LF, Curl EA. Methods for Research on the Ecology of Soil-Borne Plant Pathogens. Minneapolis, MN: Burgress Publishing Company; 1972

[5] Jachson ML. Soil Chemical Analysis. London: Constable and Co.; 1958

[6] Williams V, Twin S. Flame photometric method for sodium, potassium and calcium. In: Paech K, Tracev MV, editors. Modern Methods of Plant Analysis. Vol. V. Berlin: Springer-Verlag; 1960. pp. 3-5

[7] Schwarzenbach G, Biedermann, W.: Complexons. XAlkaline earchcomplexes of O, O-dihydroxy azo days. Helvetica Chimica Acta. 1948;**31**:678-687 (in German)

[8] Eggins H, Pugh PJF. Isolation of cellulose decomposing fungi from soil. Nature. 1962;**193**:94-95

[9] Paterson RRM, Bridge PD. Biochemical methods for filamentous fungi. In: IMI Technical Handbooks No. 1, Wallingford. UK: CAB International; 1994

[10] Ullman U, Blasins C. A simple medium for the detection of different lipolytic activity of microorganisms. Zentrabl Bakteriol Hyg II Abt A. 1974;**2**: 264-267

[11] Gochenaur SE. Fungi of a Long Island oak-birch forest II. Population dynamics and hydrolase patterns for the soil Penicillia. Mycologia. 1984;**76**:218-231

[12] Hankin L, Zucker M, Sands M. Improved solid medium for the detection and enumeration of pectolytic bacteria. Applied Microbiology. 1971;**22**:205-209

[13] Nakamura S, Wakabayashi K, Horikoshi K. Purification and some properties of an alkaline xylanase from akaliphilic bacillus sp. strain 41 M-1. Applied and Environmental Microbiology. 1993;**59**:2311-2316

[14] Gouda HAA. Studies on xerophilic, acidiphilic and alkaliphilic fungi in Wadi El-Natrun. [M.SC. thesis] Department of Botany, Faculty of Science, Assiut University, Assiut, Egypt. 2009. pp. 613

[15] Moubasher AH, Ismail MA, Hussein NA, Gouda AAH. Terrestrial fungi tolerating the hypersaline water of Wadi El-Natrun Lakes, Egypt. Journal of Basic & Applied Mycology (Egypt). 2013; **4**:47-58

[16] Moubasher AH, Ismail MA, Hussein NA, Gouda AH. Osmophilic/ osmotolerant and halophilic/halotolerant mycobiota of soil of Wadi El-Natrun region, Egypt. Journal of Basic & Applied Mycology (Egypt). 2015;**6**:27-42

[17] Gouda HA, Moubasher AH, Ismail MA, Hussein NA. Osmophilic/ osmotolerant and halophilic/halotolerant fungi from mud, salt crusts, and air collected from Wadi El-Natrun lakes. Journal of Multidisciplinary Sciences. 2020;**2**(2):30-40

[18] Gouda HA, Moubasher AH, Ismail MA, Hussein NA. Acidophilic and acidotolerant fungi in mud and salt

crusts collected from Wadi El- Natrun lakes. Part 1. Journal of Agriculture, Food and Environment. 2020;**1**(2):41-51

[19] Gouda HA, Moubasher AH, Ismail MA, Hussein NA. Alkaliphilic and alkalitolerant fungi in mud and salt crusts collected from Wadi El- Natrun lakes, part 2. Journal of Agriculture, Food and Environment. 2020;**1**(2):52-62

[20] Moubasher AH, Ismail MA, Hussein NA, Gouda AH. Enzyme producing capabilities of some extremophilic fungal strains isolated from different habitats of Wadi El-Natrun, Egypt part 1: Protease, lipase and phosphatase. European Journal of Biological Research. 2021;**6**(2):92-102

[21] Moubasher AH, Ismail MA, Hussein NA, Gouda AH. Enzyme producing capabilities of some extremophilic fungal strains isolated from different habitats of Wadi El-Natrun, Egypt part 2: Protease, lipase and phosphatase. European Journal of Biological Research. 2016;**6**(2):103-111

## *Edited by Ali A. Assani*

Lakes are among the most extensive freshwater aquatic ecosystems in the world. Their evolution results from the interactions of numerous natural and anthropogenic factors. This book includes 12 chapters and presents case studies on the impacts of changes and tectonic movements on the evolution of lake water levels (Section 1), the interactions between anthropogenic activities and the physicochemical characteristics of lakes (Section 2), and the limnological characteristics and their interactions with other components of the environment (Section 3).

## *J. Kevin Summers, Environmental Sciences Series Editor*

Published in London, UK © 2024 IntechOpen © Jian Fan / iStock

Science of Lakes - Multidisciplinary Approach

IntechOpen Series

Environmental Sciences, Volume 14

Science of Lakes

Multidisciplinary Approach

*Edited by Ali A. Assani*