A total of 30 samples were taken from 10 sites determined on the Kirmir Stream and the Süvari Stream in three different seasons (June 2022, October 2022, January 2023). In this study, 8853 black fly specimens belonging to eight species were identified from the 30 studying sites. The number of black fly individuals at each studying site is the sum of the number of individuals collected by both hand and D-frame net. Identified species and studying sites are given in Table 1. The numbers in parentheses of the studying sites in Table 1 represent the sampling season. According to this; “(1)” refers to June 2022, “(2)” refers to October 2022 and “(3)” refers to January 2023. The samples collected from Site KRM_8(1) could not be identified to the species level due to early instar. Therefore, there are no species present at this site in Table 1.
Table 1
List of Simuliidae species found in the studying sites
Studying sites | S. erythrocephalum | S. petricolum | S. angustitarse | S. bezzii | S. ornatum | S. trifasciatum | S. balcanicum | S. pseudequinum |
KMR_1(1) | | * | * | | * | | * | * |
KMR_1(2) | * | * | | * | * | | * | * |
KMR_1(3) | | | * | * | * | * | | * |
KMR_2(1) | | * | | | | | * | * |
KMR_2(2) | | * | * | * | | | * | * |
KMR_2(3) | | * | | * | * | * | * | * |
KMR_3(1) | | * | | | | | * | * |
KMR_3(2) | | * | | * | | | * | * |
KMR_3(3) | | * | * | * | * | * | | |
KMR_4(1) | | * | | | * | | * | * |
KMR_4(2) | * | * | * | | | | | |
KMR_4(3) | | * | | * | * | * | | |
KMR_5(1) | * | * | | | * | | * | * |
KMR_5(2) | | * | * | | | | * | * |
KMR_5(3) | | * | | * | * | * | | |
KMR_6(1) | | * | | | * | | * | * |
KMR_6(2) | | * | * | | | | * | * |
KMR_6(3) | | * | | * | * | * | * | |
KMR_7(1) | | * | | | | | * | * |
KMR_7(2) | | * | * | | | | | |
KMR_7(3) | | * | | * | * | * | * | * |
KMR_8(1) | | | | | | | | |
KMR_8(2) | | * | | | | | * | * |
KMR_8(3) | | | | * | * | * | | |
KMR_9(1) | | * | | | | | * | * |
KMR_9(2) | | * | | | | | | |
KMR_9(3) | | * | | * | * | * | | |
KMR_10(1) | | * | | | | | * | * |
KMR_10(2) | | * | | | | | * | * |
KMR_10(3) | | | | * | * | | | |
In 30 sampling sites, water temperature values ranged from 3.83 to 28.23°C. The concentrations of dissolved oxygen ranged from 4.74 to 13.10 mg/l. Values of electrical conductivity ranged from 428 to 923 mS/cm. pH values ranged from 7.27 to 9.37. The current velocity values ranged from 0.21 to 1.08 m/s (Fig. 2).
In the Redundancy Analysis (RDA), the total variance (inertia) in the species data was 1.030. The eigenvalues for axes 1–4 were 0.537, 0.030, 0.019, and 0.002 respectively. All variables explain 58% of the total species variability. The first two canonical axes accounted for 56.7% of the cumulative variance of the species data and 96.4% of the species-environment relationship (Monte Carlo perm. test, p-value: 0.002). The order of significance from highest to lowest of the environmental variables in RDA was water temperature, dissolved oxygen concentration, pH, current velocity, and electrical conductivity.
In the RDA diagram, S. bezzii, S. ornatum Meigen, 1818, and S. trifasciatum Curtis, 1839 were placed together, separately from the other five species (Fig. 3). These species have high numbers of individuals (3584, 1451, and 652 respectively) at sampling sites in January 2023 and they are close to these studying sites (Fig. 4). Simulium bezzii was the most abundant species (40.54%) in this study (Fig. 5). This species was not sampled in June 2022, but 3584 individuals were collected in January 2023 (Fig. 4). It was located opposite the arrow representing water temperature and dissolved oxygen concentration in the RDA diagram. Simulium bezzii has a wide range of tolerance to water temperature and dissolved oxygen concentration (Lopez Pena and Peydro 2020; Lopez Pena et al. 2020). While it can generally be found in streams with fast-flowing, it can also live in eutrophic waters with low dissolved oxygen concentrations and in degraded habitats. (Lechthaler and Car 2005; Kazancı and Ertunç 2010; Boudghane-Bendiouis et al. 2014).
Simulium ornatum and S. trifasciatum are among the most widely distributed black fly species in the Palearctic region (Lechthaler and Car, 2005; Adler 2022). They have a high tolerance to changes in environmental conditions (Seitz 1992; Feld et al. 2002; Lautenschlager and Kiel 2005; Bernotiene 2010; Lopez Pena et al. 2020). Simulium trifasciatum was recorded only at sampling sites in January 2023. These species (S. ornatum and S. trifasciatum) are frequently found on leaves of submerged macrophytes (Seitz 1992; Timm and Klopp 1993; Bernotiene 2010). Macrophytes and algal tufts were observed more at sampling sites in this period than in other periods. Scheder and Waringer (2002) reported that S. ornatum and S. trifasciatum have three generations per year and similar life cycles. It is known that these species overwinter as larvae (Sprangauskaite 1998; Bernotiene 2010). They were collected only in the larval stage in January 2023. It has also been reported that overwintering larvae are significantly bigger than summer-generation larvae (Post 1983; Zhang and Malmqvist 1997). The size of the larvae of the three species (S. bezzii, S. ornatum, and S. trifasciatum) collected at the studying sites in January 2023 was the biggest among all larvae collected throughout our study.
Simulium erythrocephalum and S. angustitarse were located near the center of the RDA diagram (Fig. 3). This means that environmental variables used in the RDA diagram do not influence the distribution of these species. Simulium erythrocephalum can be found in many different stream types such as small water courses, lake outlets, and lowland rivers, and it has a high tolerance to pollution and organic contamination (Lechthaler and Car 2005; Werner and Kampen 2012). In this study, the species with the fewest number is S. erythrocephalum with 7 individuals. This species is followed by the S. angustitarse with 64 individuals (Fig. 4). It has a wide tolerance range to environmental conditions (Lopez Pena and Peydro 2020). Like S. erythrocephalum, it can live in streams polluted by organic wastes (Rubtsov 1990). This species was found in similar numbers of individuals in June 2022, October 2022, and January 2023 (21, 29, and 14 respectively) (Fig. 4).
In this study, the most frequently found species were S. petricolum, S. balcanicum Enderlein, 1924, and S. pseudequinum (86.67%, 63.33%, and 63.33% respectively) (Fig. 5). These species were sampled from 26, 19, and 19 studying sites, respectively (Table 1). These three species were observed in all three periods, but the number of studying sites where these species were detected was higher in June 2022 and October 2022 than in January 2023 (Table 1). In the RDA diagram, S. petricolum, S. balcanicum, and S. pseudequinum were located near the studying sites in June 2022 and October 2022 (Fig. 3).
Simulium petricolum can tolerate a wide range of water temperatures and dissolved oxygen concentrations (Lechthaler and Car 2005; Lopez Pena et al. 2021). This species was found more frequently in the June 2022 (total 235 individuals) and October 2022 (total 287 individuals) seasons than in the January 2023 (total 87 individuals) season (Fig. 4). Simulium balcanicum and S. pseudequinum exist in small-sized lowland streams with low current velocity (Rubtsov 1990; Lechthaler and Car 2005). They can resist high water temperatures and survive in polluted and degraded aquatic environments (Lounaci et. al. 2000; Stangler and Halgos 2007; Cherairia et al. 2014). Simulium balcanicum and S. pseudequinum are represented with the highest number of individuals (306 and 1692 respectively) in June 2022 (Fig. 4). These two species are also the second and third most abundant species after S. bezzii in the study (Fig. 5).
According to the RDA diagram (Fig. 3), studying sites of June 22 and October 22 showed positive correlations with dissolved oxygen, electrical conductivity, water temperature, and current velocity while negative correlations with pH variable. Since the studying sites of June 2022 and October 2022 were at the beginning of summer and the end of summer, the water temperature was high. In the studying sites of January 2023, the water temperature value was measured low because of the winter season. Due to low seasonal rain and snowfall, the water level in the river bed was also low during this period. The low water level negatively affected the current velocity of the streams. Consequently, studying sites of January 2023 were located opposite the arrows representing water temperature and current velocity. Aquatic macrophytes and filamentous algae were observed densely at many studying sites in this sampling period. Their abundance can cause an increase in the pH value of the aquatic environment due to their high level of photosynthetic activity (Dodds 2003; Middelboe and Hansen 2007). Although photosynthetic activity increases the dissolved oxygen concentration, the decomposition of aquatic macrophytes and insufficient circulation caused by the low water level have a negative impact on the dissolved oxygen concentration. Most of the studying sites in January 2023 were located near the arrow representing the pH value, away from the arrow representing the dissolved oxygen variable in the RDA diagram (Fig. 3).
Since Kirmir Stream is surrounded by settlements and agricultural lands, organic and inorganic pollutants such as pesticides, domestic waste, and fertilizers entering the water from these areas deteriorate the water quality of the Kirmir Stream. Ammonium (NH4+) and nitrate (NO3-) ions carried into streams through rainfall and irrigation, acids formed as a result of the decomposition of organic waste from domestic and industrial facilities, and domestic cleaning products cause the pH value of the water to decrease and the electrical conductivity value to increase (Morrison et al. 2001; Wurtsbaugh et al. 2019; Saalidong et al. 2022). In addition, high-temperature values cause an increase in the concentration of salt and pollutants due to evaporation, which in turn causes an increase in electrical conductivity value. The effects of these substances, which reach the water through natural events or anthropogenic activities, on pH and electrical conductivity values were observed at the studying sites in June 2022 and October 2022. These sites were located near the arrow representing electrical conductivity value, opposite the arrow representing pH value in the RDA diagram (Fig. 3).
In this three-period study, the highest number of black fly individuals was found in January 2023 (6004), followed by June 2022 (2269), and the lowest number of individuals was found in October 2022 (580) (Fig. 4). Simulium pseudequinum was recorded as the species with the highest number of individuals in June 2022 (1692), followed by S. petricolum in October 2022 (287), and S. bezzii in January 2023 (3584) (Fig. 4). As a result of this study, it was determined that black fly densities and dominant species in the Kirmir Stream vary in summer, autumn, and winter seasons.