Environ Monit Assess (2014) 186:7631–7642 DOI 10.1007/s10661-014-3954-8
Water quality of Mediterranean coastal plains: conservation implications from the Akyatan Lagoon, Turkey Aysegul Demir Yetis & Zeliha Selek & Galip Seckin & Orkun I. Davutluoglu
Received: 21 August 2013 / Accepted: 22 July 2014 / Published online: 31 July 2014 # Springer International Publishing Switzerland 2014
Abstract The water quality of the Akyatan Lagoon was characterized using hydrochemical methodology. The lagoon is located on the Mediterranean coast and is the largest wetland ecosystem in Turkey. In addition, the lagoon is classified as a hyper-salinity wetland. Water samples were collected monthly between December 2007 and November 2008. Eleven stations within the lagoon were determined, and triplicate grab samples were obtained from each station to characterize water quality as follows: T °C, pH, total alkalinity (TAlk), dissolved oxygen (DO), total dissolved solids (TDS), salinity, electrical conductivity (EC), and main anions, including chloride (Cl−), nitrates (NO3−), and sulfate (SO42−). Results from selected stations indicated varying TDS, EC, salinity, and Cl− concentrations, from 20,892 to 175,824 mg/L, from 35.7 to 99.6 mS/cm, from 22.3 to 71.0 ppt, and from 14,819 to 44,198 mg Cl−/L, respectively. Data indicated that the spatial distribution of water quality parameters was significantly affected by freshwater input via the constructed drainage channels which collect water from a catchment area and discharge water into the lagoon as a point source, thus preventing drainage water to reach the lagoon as a nonpoint source.
A. Demir Yetis (*) Environmental Engineering Department, Bitlis Eren Üniversity, 13000 Bitlis, Turkey e-mail: [email protected] Z. Selek : G. Seckin : O. I. Davutluoglu Environmental Engineering Department, Cukurova University, 01330 Balcali, Adana, Turkey
Keywords Mediterranean lagoon . Water quality . Hyper-salinity . Seawater intrusion
Introduction Coastal lagoons are positioned between land and sea and are consequently the most productive marine ecosystems in the world. These ecosystems serve as nursery and feeding areas for many continental and marine species including vertebrate and invertebrate taxa (Lacerda and Goncalves 2001; Maanan et al. 2004; Figueroa et al. 2006; Viaroli et al. 2007). Due to the relatively shallow structure of most coastal lagoons, the ecosystems are highly sensitive to changes in biogeochemistry as a result of physical forces among land, sea, and atmosphere including winds, tides, and changes in the sea level (Beltrame and De Marco 2009; Chandra et al. 2010; Mabwoga et al. 2010). Therefore, lagoons have been characterized as complex ecosystems with a fragile equilibrium (Colombo and Lagoons 1977). Like most coastal lagoons, the Akyatan Lagoon also serves as an ecologically important habitat for several globally endangered species, such as marine turtles and water birds. In addition, Akyatan Lagoon has long been economically integral to the region; a large number of commercial species are caught with traditional barrier fish traps, seasonal fish migration occurs between the sea and lagoon, and there is inverse migration. The lagoon is located along bird migration routes, resulting in thousands of migrant birds of diverse numbers of species which are temporarily hosted at the lagoon.
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Furthermore, the lagoon exhibits suitable climatic conditions for many insect species to overwinter, when severe cold dominates the interior regions of the country. Various government and national agencies have recognized the paramount importance of Akyatan Lagoon in supporting wildlife. Legal environmental protection status by decree of the Turkish government was established, and the intergovernmental treaty of Ramsar also serves to protect the lagoon. However, dense urbanization is adjacent to the lagoon catchments, as well as increased agricultural and industrial activities. Previous studies of the Akyatan Lagoon have included assessing the status of endangered loggerhead turtle nesting activities (Godley et al. 2001; Canpolat 2004). Mingazova et al. (2008) evaluated the ecological state of two Mediterranean lagoons along the Turkish coast, one of which is the Akyatan Lagoon. Our research group previously addressed total metal content and metal speciation in Akyatan Lagoon sediments (Davutluoglu et al. 2010). As a further stage, the goal of this study was to determine the monthly and spatial changes in Akyatan Lagoon water quality for a period of 1 year.
Materials and methods General description of the study area Tuzla, Yumurtalık, Akyatan, and Agyatan Lagoons belong to substantial lagoon system that is only in the country. The Akyatan Lagoon is the biggest lagoon in the system. The lagoon has a surface area of 14.7 ha and is located between the coordinates of 36° 37′ 0″ N and 035° 16′ 0″ E on the shore of the Mediterranean Sea within the Karataş district of Adana City, Turkey. The lagoon study area and sampling stations are shown in Fig. 1, and the geographic positions of the stations are given in Table 1. The region exhibits a typical Mediterranean climate with warm to hot dry summers and mild, cool, and wet winters. The maximum and minimum temperatures are generally observed during January and August (on average, 5.4 and 34.4 °C, respectively). The maximum precipitation falls primarily in December, which averages about 125 kg/m2, and minimum precipitation is observed in August with 13.2 kg/m2 (DMI 2008). The lagoon has a relatively shallow average depth of 0.75 m. The lagoon receives freshwater from its catchments via rainfall, nonpoint underground water resources, and drainage channels,
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while seawater enters via the canal opening connected to the Mediterranean Sea. Following a tidal cycle, the lagoon exchanges water and sediments with the sea. The freshwater delivered by an extensive network of drainage channels nonuniformly controls the hyper-salinity of the lagoon and carries various pollutants from the catchment area. Agriculture is the primary land use in the region, where fertilizers are commonly applied to the major crops which include cereals, a variety of fruit, cotton, peanuts, and watermelon (Davutluoglu et al. 2011). The lagoon bottom sediments generally consist of clay and silt, in addition to sand, and the sediments are contaminated with some heavy metals and other pollutants (Davutluoglu et al. 2010). Analytical methods Grab water samples were collected from the surface using acid-cleaned 500-mL polyethylene bottles for a period of 12 months, from December 2007 through November 2008. Eleven stations with depths varying from 0.5 to 1 m were determined in the lagoon, and the samples were obtained once per month. A total of three samples were taken at a time from each specified location to get more statistically accurate results (statistical standard deviation fell within approximately 1–3 %). Samples obtained from each station were characterized in terms of water quality as follows: T °C, pH, total alkalinity (TAlk), dissolved oxygen (DO), total dissolved solids (TDS), salinity, electrical conductivity (EC), and main anions including chloride (Cl−), nitrates (NO3−), and sulfate (SO42−). EC and salinity measurements were performed on site using a portable conductivity meter (Thermo Scientific Orion3) as well as DO and T °C measured with a DO meter (YSI, model 55/ 12). A handheld pH meter (WTW 315I/SET) was used to measure pH right after sampling. Immediately after collection, the samples were chilled in an ice chest at about 1–4 °C with the help of ice packs. The remaining analyses were done within 6 h of sample collection. The remaining parameters were determined via standard methods (APHA 2005) applying the gravimetric method for TDS (Method 2540-D), argentometric method for TAlk and Cl− (Method 2320-B and Method 4500-B, respectively), and spectro-photometric method for SO42− and NO3− (Method 4110-B and Method 4500B, respectively). A Perkim-Elmer TU-1880 UV-VIS Spectrophotometer was used to measure SO42− and NO3−.
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Fig. 1 Akyatan Lagoon and sampling stations
Results and discussion Assessment of water quality spatial variation Results indicated a spatial variation in Akyatan Lagoon among the stations for the water quality parameters (Fig. 2). Lagoon water temperature was expected to play a significant role in water hydrodynamics and chemical and biological processes (Davis and Fitzgerald 2004). Lagoon water temperature exhibited from 7.0 to 33.8 °C temperature range during the course of the study (Table 2). The lowest temperature was observed in January at S-5 (7 °C), located toward the center of the lagoon, and the highest temperature at S-1 in September (33.8 °C), located near the west coast of the lagoon. Lagoon temperature is recognized as a significant factor impacting freshwater, in association with low TDS Table 1 Geographic positions of the sampling stations Station no.
Elevation (m)
Latitude (north)
Longitude (east)
1
0.70
36° 39′ 51″ N
35° 12′ 20″ E
2
0.50
36° 38′ 38″ N
35° 14′ 06″ E
3
0.67
36° 37′ 29″ N
35° 15′ 55″ E
4
0.44
36° 37′ 18″ N
35° 17′ 05″ E
5
0.65
36° 36′ 00″ N
35° 16′ 59″ E
6
0.90
36° 37′ 03″ N
35° 18′ 05″ E
7
0.50
36° 36′ 14″ N
35° 18′ 05″ E
8
0.64
36° 35′ 32″ N
35° 18′ 06″ E
9
0.67
36° 36′ 22″ N
35° 19′ 24″ E
10
0.83
36° 35′ 22″ N
35° 19′ 25″ E
11
0.78
36° 34′ 33″ N
35° 19′ 20″ E
mixing into hyper-saline lagoon water (Diamantopoulou et al. 2008). A slightly alkaline nature was determined throughout the lagoon, indicated by pH and TAlk levels. Spatial variation in pH was minimal, with the lowest pH observed at S-1 (7.82 in November 2008) and highest at S-5 (9.13 in July 2008). In general, pH values were higher nearest to the center of the lagoon. However, the stations closest to the drainage channels, DC-1 and DC2, and the channel opening to the sea (i.e., stations S-6 to S-11) showed varying pH values based on the kind of water the station received at the time of sampling. For example, the station might have received drainage discharge or seawater on the sampling date. A similar trend was observed for TAlk. The minimum value was observed at S-5 (96 mg CaCO3/L, August 2008) and the maximum at S-11 (344 mg CaCO3/L, October 2008). However, an overall annual assessment showed that the seawater alkalinity (TAlk) was slightly lower than that of the lagoon water (211 mg CaCO3/L), and the Talk levels for the drainage channels (364 mg CaCO3/L for DC-1 and 310 mg CaCO3/L for DC-2) were higher than those for the lagoon (Table 2). The main factors affecting pH and alkalinity were DC-1, DC-2, the channel opening to the sea, precipitation, and evaporation, particularly in shallow depths. Turkdogan-Aydinol et al. (2012) stated that seawater is affected by temperature pressure, photosynthesis, and respiration activity of microorganisms. Moreover, temperature-dependent respiration by aquatic organisms and solar irradiation-dependent photosynthetic activities are other components of the ecosystem affecting spatial variation in pH and alkalinity (Davis and Fitzgerald 2004).
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Fig. 2 Spatial distribution of each water quality parameter derived from annual mean values of each station (S-1–S-11)
The spatial distribution patterns of TDS, EC, salinity, and Cl− exhibited similarities. TDS levels showed considerable variation, with a range of 20,892–175,824 mg/ L during the study period. The lowest TDS was determined in May at S-11, close to the seawater mixing zones (i.e., DC-1 and DC-2). The highest TDS was observed in September (a dry month) at S-1, a station
located on the west end of the lagoon with an absence of a freshwater input as a point source. Chloride (Cl−) also demonstrated a spatial distribution similar to TDS, with the lowest value at S-11 (in May) and the highest value at S-3 (in September). On site, the highest EC and salinity observations S-3 were 162 mS/cm and 119.6 ppt, respectively (in September), and the lowest
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Table 2 Annual lagoon water quality basic statistics (12 months×11 parameters N=132) Parameter
Unit
Min
Median
Mean
Max
SD
CV
T
°C
7.00
23.10
22.60
33.80
8.41
0.37
pH
-
7.82
8.30
8.31
9.13
0.27
0.03
EC
(mS/cm)
28.37
53.10
60.26
162.00
22.68
0.38
Salinity
(ppt)
17.50
34.40
39.99
119.60
16.61
0.42
DO
(mg/L)
2.00
5.53
5.92
9.38
1.61
0.27
−
Cl
(mg/L)
10,511
21,524
25532.6
88,697
12,041
0.47
TDS
(mg/L)
20,892
45,510
52154.8
175,824
25,054
0.48
TAlk
(mgCaCO3/L)
94
256
252.79
442.00
51.01
0.20
SO42−
(mg/L)
165
202
202.92
253.00
19.16
0.09
NO3−
(mg/L)
0.44
2.25
2.28
5.51
0.95
0.42
EC and salinity levels were determined at S-11 as 28.37 mS/cm and 17.5 ppt, respectively (in May). Relative to lagoon water, EC levels in the DC-1 drainage channel, which play an important role in dissolved ion balance, were very low within a range of 0.65–12.7 mS/ cm and an annual mean of 3.8 mS/cm. Similar results were found for DC-2, with an EC level between 0.3 and 7.3 mS/cm and an annual mean of 2.1 mS/cm. DC-1 and DC-2 annual salinity levels were 8.3 to 5.3 ppt, respectively. Compared to stations closer to the west coast of the lagoon, all water quality parameters showed decreased values at stations closer to the drainage channel discharges, i.e., DC-1 and DC-2, which deliver freshwater into the lagoon. Furthermore, annual respective levels of TDS, Cl−, EC, and salinity at 44788 mg/L, 22,830 mg/L, 55.7 mS/cm, and 36.5 ppt for TDS, Cl−, EC, and salinity in seawater, respectively, serve to control salinity in the lagoon with relatively high levels through dilution. TDS concentration is influenced by surface water runoff from point and nonpoint sources (Shin et al. 2013). The spatial distribution of SO42−, based on annual mean values, did not significantly vary (P =0.002) throughout the lagoon, and observed concentrations ranged from 165 to 253 mg/L (Fig. 2). S-1 and S-2 exhibited the highest and S-9 and S-10 the lowest concentrations of SO42. Lower SO42− levels were observed toward the center of the lagoon, and DC-1 and DC-2 showed, respectively, 73 and 103 mg/L SO42, which flowed into the lagoon. The annual mean SO42− concentration of the seawater was 190 mg/L, slightly lower than that for the lagoon. NO 3 − concentration varied among stations (Fig. 2). Annual mean NO3− concentrations ranged from 1.5 to 3.0 mg/L. The highest concentrations
were observed in S-1, S-2, and S-5, well above 2.5 mg/L, while S-10 and S-11 showed the lowest concentrations. The S-11 and S-10 NO3− concentrations can be explained by 0.83 mg NO3−/L (annual mean) in seawater flow entering the lagoon. High NO3− concentration is suspected to be the result of fertilizer use on agricultural crops. All water drained from the adjacent areas (i.e., Karataş district) reaches a catchment which is discharged in the drainage channels and reaches the lagoon. For several decades, increased eutrophication is one of the leading environmental issues in coastal and estuarine waters and threats to the health of marine ecosystems (Zhou et al. 2014). Increasing of soluble nutrients affects the ecological characteristics of all species living in lagoons. Having small water quantity, shallow depths, and restricted water exchange, lagoons are sensitive to human impacts, freshwater, and nutrient inputs (Kharroubi et al. 2012). However, increased NO3− concentrations surrounding S-1, S-2, and S-5 are likely to be due to relatively stagnant water around the stations due to low turbulence while the drainage water with relatively lower NO3− concentrations coming from the adjacent areas (i.e., Karataş district) is discharged into the drainage channels eventually reaching the lagoon. This negatively affects especially S-6, S-7, S-9, and S-10. The major factors affecting spatial variation in the water quality parameters among the 11 stations were determined as follows: (i) the shallow structure of the Akyatan Lagoon, which increases the impacts of temperature and wind; (ii) seawater and freshwater resource content and water discharge points into the lagoon; and
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(iii) varying freshwater input and evaporation output during the wet and dry months. Assessment of monthly variation in water quality Variations in surface water parameters of the Akyatan Lagoon for the winter months (December, January, February), spring (March, April, May), summer (June, July, August), and autumn (September, October, November) are presented in Table 3. In addition, the monthly variation of water quality parameters based on the average of all stations is depicted in Fig. 3. The lagoon water temperature never fell below freezing, and the minimum observed temperature was 7.0 °C in January. The annual mean water temperature was 22.6 °C, and higher temperature values were observed during the summer and autumn months. In winter, DC-1 and DC-2 temperatures varied similarly to the lagoon. However, in summer and autumn, the temperatures of both channels were lower compared with the lagoon. Seawater exhibited a mean annual temperature of 22.3 °C, and in most months, particularly in summer and autumn, the seawater temperature was lower than that of the lagoon. The observed annual variation in Akyatan Lagoon temperature was consistent with a previous study by Dural (2004). The shallow lagoon structure plays an important role in poor temperature distribution in terms of thermal stratification and other water quality parameters. Variation in pH for winter, spring, summer, and autumn was 7.97–8.50, 7.92–8.65, 7.83–9.13, and 7.82– 8.97, respectively. Mean pH values were 8.29 in winter, 8.19 in spring, 8.41 in summer, and 8.36 in autumn. These values were slightly higher than those reported for other Mediterranean lagoons, particularly for summer and autumn (Table 4). DC-1 exhibited an increased pH value (8.55) relative to the lagoon in winter and a decreased value for the other seasons. DC-2 showed lower pH values than all other stations in the lagoon for the four seasons. TAlk content was stable and consistent with the pH levels indicated above. On average, seasonal mean TAlk concentrations were approximately 268, 277, 224, and 241 mg CaCO3/L for winter, spring, summer, and autumn, respectively. During the study period, TDS, Cl−, EC, and salinity values presented significant variation for each season (Table 3). Climatic conditions can markedly influence the seasonal variation in water quality. TDS reached a maximum value due to increased evaporation from high
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weather temperatures, which ranged between 25.6 and 34.4 °C during the June–November period. Another factor increasing the impact of evaporation was wind velocity, which was especially high during the spring months with a maximum of 85.7 km/h. Furthermore, summer and autumn precipitation was very low (3.16 kg/m2). Increased salinity was observed at both ends of the lagoon where evaporation was assumed to be higher than precipitation due to the increased shallowness, temperature, and wind conditions. Because the maximum TDS values (175,824 mg/L) were observed shortly after the first fall of precipitation in October, it is plausible that salt deposits dissolved back into the lagoon water and intermittently resulted in increased TDS values. The annual mean DC-1 and DC-2 TDS values were 2,474 and 6,884 mg/L, respectively. However, as a result of the typically intense agricultural irrigation during the summer period, lower TDS values were observed in the drainage channels (i.e., 400–870 mg/ L DC-1, 458–1,306 mg/L DC-2). Therefore, it is reasonable that relatively lower TDS values were observed at stations adjacent to the two drainage channels discharging into the lagoon. The preceding discussion points also support seasonal variation in EC, Cl−, and salinity in the drainage channels and lagoon. During the study period, TDS, EC, Cl−, and salinity values presented significant seasonal variation. The mean TDS concentrations were 51,045, 54,454, and 65,607 mg/L for winter, summer, and autumn seasons, respectively, whereas the spring results were notably lower at 38,736 mg/L. EC values varied monthly between 28.37 and 162 mS/cm; Cl− and salinity concentrations ranged between 10,511 and 88,697 mg/L and 17.5 and 119.6 ppt, respectively (Table 3). EC annual mean was 60.3 mS/cm with 95 % statistical confidence. In winter, EC values varied from 38.5 to 92.9 mS/cm, while Cl− and salinity concentrations ranged, respectively, from 17,517 to 43,047 mg/L and 24.5 to 65.9 ppt. In spring, results showed decreased EC values, from 28.4 to 69.0 mS/cm, and Cl− and salinity concentrations showed a similar decrease in spring, from 10,511 to 29,032 mg/L and 17.5 to 47.2 ppt, respectively. In summer, EC varied from 39.3 to 105.7 mS/cm, Cl− from 5,016 to 47,302 mg/L, and 25 to 75.2 ppt for salinity. EC values during autumn exhibited values between 33.8 and 162 mS/cm, consistent with previous seasons. However, determined results indicate that Cl− and salinity concentrations ranged between 13,565 to 88,697 mg/ L and 21 to 119.6 ppt, respectively. EC and salinity also
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Table 3 Seasonal variation in water quality for the Akyatan Lagoon Parameter
Unit
Min
Median
Mean
Max
SD
CV
Winter (December, January, February) T
°C
7.0
11.5
10.6
14.3
2.37
0.22
pH
-
7.97
8.32
8.29
8.50
0.17
0.02
EC
mS/cm
38.5
57.0
59.5
92.9
12.62
0.21
Salinity
ppt
24.5
37.7
39.66
65.90
9.70
0.24
DO
mg/L
5.67
8.32
8.10
9.38
0.94
0.12
Cl−
mg/L
17,517
22,524
24,695
43,047
5811.9
0.24
TDS
mg/L
34,392
48,620
51,045
76,422
9302.9
0.18
TAlk
mgCaCO3/L
206
263
267.97
322
24.50
0.09
SO42− NO3−
mg/L
178
209
207.33
248
19.19
0.09
mg/L
1.29
2.25
2.14
3.33
0.45
0.21
Spring (March, April, May) T
°C
18.7
22.1
22.8
27.2
2.27
0.10
pH
-
7.92
8.19
8.19
8.65
0.20
0.02
EC
mS/cm
28.37
47.80
48.11
69.00
7.57
0.16
Salinity
ppt
17.50
30.50
30.58
47.20
5.61
0.18
DO
mg/L
2.97
5.30
5.24
6.61
0.91
0.17
Cl−
mg/L
10,511
19,021
19,340
29,032
3498
0.18
TDS
mg/L
208,920
39,008
38,735
56,558
6858
0.18
TAlk
mgCaCO3/L
214
278
277
344
38.4
0.14
SO42−
mg/L
173.00
191.00
194.76
239.00
14.78
0.08
NO3−
mg/L
0.77
2.35
2.52
4.93
0.97
0.38
28.20
31.20
31.35
33.60
1.80
0.06
Summer (June, July, August) T
°C
pH
-
7.83
8.35
8.41
9.13
0.33
0.04
EC
mS/cm
39.30
58.40
62.80
105.70
17.52
0.28
Salinity
ppt
25.00
38.70
42.33
75.20
13.22
0.31
DO
mg/L
3.88
4.81
5.00
7.19
0.88
0.18
Cl−
mg/L
15,016
24,026
26,134
47,302
8,453
0.32
TDS
mg/L
31,468
49,038
54,454
98,384
17,603
0.32
TAlk
mgCaCO3/L
94
232
224
292
42.59
0.19
SO42−
mg/L
172
215
215
253
16.46
0.08
NO3−
mg/L
0.60
2.43
2.41
4.81
0.95
0.39 0.23
Autumn (September, October, November) T
°C
16.10
26.20
25.86
33.80
5.97
pH
-
7.82
8.38
8.36
8.97
0.30
0.04
EC
mS/cm
33.80
59.70
71.68
162.00
37.17
0.52
Salinity
ppt
21.00
38.95
48.14
119.60
26.64
0.55
DO
mg/L
2.00
5.51
5.29
7.40
1.17
0.22
−
Cl
mg/L
13,565
24,927
32,602
88,697
20,343
0.62
TDS
mg/L
25,846
49,364
65,606
175,824
43,379
0.66
TAlk
mgCaCO3/L
126
235
240
442
71.90
0.30
SO42−
mg/L
165
190
192
230
16.97
0.09
NO3−
mg/L
0.44
1.67
2.02
5.51
1.26
0.62
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Fig. 3 Monthly variation of water quality parameters derived from station averages (S-1–S-11)
varied over consecutive months depending on meteorological conditions (temperature, precipitation), seawater intrusion, turbulence, and drainage channel discharge. High EC and salinity levels were observed for December and July through November. During these months, EC and salinity were well over 60 mS/cm and
40 ppt, respectively. EC and salinity reached maximum values in August and September, with 75 and 88 mS/cm for EC and 51 and 59 ppt for salinity, respectively. Decreased precipitation and increased temperature, resulting in higher evaporation in August and September, were probably responsible for higher EC
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Table 4 Comparison of physicochemical characterizations of Mediterranean coastal lagoons Lagoon
Akyatan, Turkey (Present sudy) Ölüdeniz, Turkey (Tuncel and Tugrul 2007) Korissia, Greece (Diamantopoulou et al. 2008) Lesina, Italy (Roselli et al. 2009) Nador, Morocco (Ruiz et al. 2006) Ria Formosa, Portugal (Loureiro et al. 2006) Vistonis, Greece (Markou et al. 2007)
Concentrations T (°C)
pH
Salinity (ppt)
DO (mg/L)
SO42− (mg/L)
NO3− (mg/L)
7.0–33.8
7.82–9.1
17.5–119
2–9.38
165–253
0.44–5.51
25–25.5
8.3–8.4
38.7–39.2
6.78–7.61
–
0.028–0.23
13.5–26.2
8.0–8.6
15.6–>50
4.6–11.2
–
0.41–0.47
10.3–27.5
8.3–8.7
6.01–37.56
85.5–120*
–
–
–
7.95–8.7
38–39.5
–
605–1,584
–
23–24.7
–
36.4–37.0
7.1–8.3
–
0.25–0.60
6.4–28.6
8.1–8.9
0.6–12.9
4.2–8.5
–
0.022–0.124
EC, Cl− , TDS, and TAlk values were not evaluated in the other lagoons *
(% sat.)
and salinity. These results indicated lower EC and salinity values from January through July (i.e., below or equal to 60 mS/cm and 40 ppt, respectively); however, the lowest values were observed from March through May for both parameters. It should be noted that hypersalinity is the typical lagoon water condition and lower salinity values are the result of dilution from precipitation, drainage water, and seawater. The freshwater flowing to the lagoons causes to reduce the salinity of the lagoon water (Kharroubi et al. 2012). Anion concentration varied markedly depending on contaminant type and season. SO42− concentration did not show significant seasonal changes. The results showed that mean seasonal concentrations were similar, with approximately 207 mg/L in winter, 195 mg/L in spring, 216 mg/L in summer, and 193 mg/L in autumn. Monthly SO42− variation (Fig. 3) was similar to SO42− spatial distribution, and its concentration varied between 180 and 224 mg/L. A distinct trend in the spatial distribution and monthly variation of SO42− was not exhibited in the lagoon. This almost even distribution of SO42− is the result of rather cold seawater movement toward the lagoon from the bottom and dispersion and diffusion of SO42− throughout the lagoon. Concurrently, relatively warmer lagoon water is pushed upward. Unlike SO42−, NO3− concentrations showed significant variation. On average, NO3− concentrations were approximately 2.14, 2.52, 2.41, and 2.02 mg/L for
winter, spring, summer, and autumn, respectively. NO3− concentration is a strong indicator of the level of fertilizer used during the agricultural season as the drainage channels direct all water flow drained from the area to the lagoon. Monthly variation in NO3− concentration was also determined and is summarized in Fig. 3. May and June exhibited the highest NO3− concentration with values of 3.62 and 2.78 mg/L, respectively, and the lowest values were observed for April and October, with 1.65 and 1.42 mg/L, respectively. The nitrate content varied between 1.42 and 2.5 mg/L for the remaining months. The results of the present study were compared with data from six other Mediterranean lagoons, which are summarized in Table 4. These include lagoons from Turkey, Greece, Italy, Morocco, and Portugal, and the studies were conducted within the last 5 years. The pH range was similar to the other Mediterranean lagoons, but the Akyatan Lagoon had a slightly broader range between 7.82 and 9.13 when compared to pH levels of between 8 and 9 for the other lagoons. A comparison of salinity levels showed that the Akyatan and Korissia Lagoons demonstrated hyper-salinity well over values for the Mediterranean with approximately 35 ppt. DO levels indicated that saturation levels and even oversaturation were reached for some lagoons, such as Korissia and Lesino,
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Table 5 Spearman rank coefficients among lagoon water quality parameters Element
T
T
1
pH
0.19
EC
0.13
0.25
Salinity
0.14
0.25
0.996*
1
DO
−0.74**
0.09
0.04
0.04
1
−
pH
EC
Salinity
DO
Cl-
TDS
TAlk
SO42−
NO3−
1 1
Cl
0.12
0.28
0.98*
0.98*
0.05
1
TDS
0.09
0.28
0.957
0.958*
0.07
0.95*
TAlk
−0.18
−0.23
−010
−0.09
−0.05
−0.09
−0.09
1
SO42−
0.008
−0.08
0.31
−0.09
0.11
0.30
0.33
−0.19
1
NO3−
0.08
−0.18
0.29
0.29
−0.20
0.27
0.29
0.14
0.29
1
1
The significance of bold entries in Table 5 represented relatively better correlation Statistical significance *P
Water quality of Mediterranean coastal plains: conservation implications from the Akyatan Lagoon, Turkey Aysegul Demir Yetis & Zeliha Selek & Galip Seckin & Orkun I. Davutluoglu
Received: 21 August 2013 / Accepted: 22 July 2014 / Published online: 31 July 2014 # Springer International Publishing Switzerland 2014
Abstract The water quality of the Akyatan Lagoon was characterized using hydrochemical methodology. The lagoon is located on the Mediterranean coast and is the largest wetland ecosystem in Turkey. In addition, the lagoon is classified as a hyper-salinity wetland. Water samples were collected monthly between December 2007 and November 2008. Eleven stations within the lagoon were determined, and triplicate grab samples were obtained from each station to characterize water quality as follows: T °C, pH, total alkalinity (TAlk), dissolved oxygen (DO), total dissolved solids (TDS), salinity, electrical conductivity (EC), and main anions, including chloride (Cl−), nitrates (NO3−), and sulfate (SO42−). Results from selected stations indicated varying TDS, EC, salinity, and Cl− concentrations, from 20,892 to 175,824 mg/L, from 35.7 to 99.6 mS/cm, from 22.3 to 71.0 ppt, and from 14,819 to 44,198 mg Cl−/L, respectively. Data indicated that the spatial distribution of water quality parameters was significantly affected by freshwater input via the constructed drainage channels which collect water from a catchment area and discharge water into the lagoon as a point source, thus preventing drainage water to reach the lagoon as a nonpoint source.
A. Demir Yetis (*) Environmental Engineering Department, Bitlis Eren Üniversity, 13000 Bitlis, Turkey e-mail: [email protected] Z. Selek : G. Seckin : O. I. Davutluoglu Environmental Engineering Department, Cukurova University, 01330 Balcali, Adana, Turkey
Keywords Mediterranean lagoon . Water quality . Hyper-salinity . Seawater intrusion
Introduction Coastal lagoons are positioned between land and sea and are consequently the most productive marine ecosystems in the world. These ecosystems serve as nursery and feeding areas for many continental and marine species including vertebrate and invertebrate taxa (Lacerda and Goncalves 2001; Maanan et al. 2004; Figueroa et al. 2006; Viaroli et al. 2007). Due to the relatively shallow structure of most coastal lagoons, the ecosystems are highly sensitive to changes in biogeochemistry as a result of physical forces among land, sea, and atmosphere including winds, tides, and changes in the sea level (Beltrame and De Marco 2009; Chandra et al. 2010; Mabwoga et al. 2010). Therefore, lagoons have been characterized as complex ecosystems with a fragile equilibrium (Colombo and Lagoons 1977). Like most coastal lagoons, the Akyatan Lagoon also serves as an ecologically important habitat for several globally endangered species, such as marine turtles and water birds. In addition, Akyatan Lagoon has long been economically integral to the region; a large number of commercial species are caught with traditional barrier fish traps, seasonal fish migration occurs between the sea and lagoon, and there is inverse migration. The lagoon is located along bird migration routes, resulting in thousands of migrant birds of diverse numbers of species which are temporarily hosted at the lagoon.
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Furthermore, the lagoon exhibits suitable climatic conditions for many insect species to overwinter, when severe cold dominates the interior regions of the country. Various government and national agencies have recognized the paramount importance of Akyatan Lagoon in supporting wildlife. Legal environmental protection status by decree of the Turkish government was established, and the intergovernmental treaty of Ramsar also serves to protect the lagoon. However, dense urbanization is adjacent to the lagoon catchments, as well as increased agricultural and industrial activities. Previous studies of the Akyatan Lagoon have included assessing the status of endangered loggerhead turtle nesting activities (Godley et al. 2001; Canpolat 2004). Mingazova et al. (2008) evaluated the ecological state of two Mediterranean lagoons along the Turkish coast, one of which is the Akyatan Lagoon. Our research group previously addressed total metal content and metal speciation in Akyatan Lagoon sediments (Davutluoglu et al. 2010). As a further stage, the goal of this study was to determine the monthly and spatial changes in Akyatan Lagoon water quality for a period of 1 year.
Materials and methods General description of the study area Tuzla, Yumurtalık, Akyatan, and Agyatan Lagoons belong to substantial lagoon system that is only in the country. The Akyatan Lagoon is the biggest lagoon in the system. The lagoon has a surface area of 14.7 ha and is located between the coordinates of 36° 37′ 0″ N and 035° 16′ 0″ E on the shore of the Mediterranean Sea within the Karataş district of Adana City, Turkey. The lagoon study area and sampling stations are shown in Fig. 1, and the geographic positions of the stations are given in Table 1. The region exhibits a typical Mediterranean climate with warm to hot dry summers and mild, cool, and wet winters. The maximum and minimum temperatures are generally observed during January and August (on average, 5.4 and 34.4 °C, respectively). The maximum precipitation falls primarily in December, which averages about 125 kg/m2, and minimum precipitation is observed in August with 13.2 kg/m2 (DMI 2008). The lagoon has a relatively shallow average depth of 0.75 m. The lagoon receives freshwater from its catchments via rainfall, nonpoint underground water resources, and drainage channels,
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while seawater enters via the canal opening connected to the Mediterranean Sea. Following a tidal cycle, the lagoon exchanges water and sediments with the sea. The freshwater delivered by an extensive network of drainage channels nonuniformly controls the hyper-salinity of the lagoon and carries various pollutants from the catchment area. Agriculture is the primary land use in the region, where fertilizers are commonly applied to the major crops which include cereals, a variety of fruit, cotton, peanuts, and watermelon (Davutluoglu et al. 2011). The lagoon bottom sediments generally consist of clay and silt, in addition to sand, and the sediments are contaminated with some heavy metals and other pollutants (Davutluoglu et al. 2010). Analytical methods Grab water samples were collected from the surface using acid-cleaned 500-mL polyethylene bottles for a period of 12 months, from December 2007 through November 2008. Eleven stations with depths varying from 0.5 to 1 m were determined in the lagoon, and the samples were obtained once per month. A total of three samples were taken at a time from each specified location to get more statistically accurate results (statistical standard deviation fell within approximately 1–3 %). Samples obtained from each station were characterized in terms of water quality as follows: T °C, pH, total alkalinity (TAlk), dissolved oxygen (DO), total dissolved solids (TDS), salinity, electrical conductivity (EC), and main anions including chloride (Cl−), nitrates (NO3−), and sulfate (SO42−). EC and salinity measurements were performed on site using a portable conductivity meter (Thermo Scientific Orion3) as well as DO and T °C measured with a DO meter (YSI, model 55/ 12). A handheld pH meter (WTW 315I/SET) was used to measure pH right after sampling. Immediately after collection, the samples were chilled in an ice chest at about 1–4 °C with the help of ice packs. The remaining analyses were done within 6 h of sample collection. The remaining parameters were determined via standard methods (APHA 2005) applying the gravimetric method for TDS (Method 2540-D), argentometric method for TAlk and Cl− (Method 2320-B and Method 4500-B, respectively), and spectro-photometric method for SO42− and NO3− (Method 4110-B and Method 4500B, respectively). A Perkim-Elmer TU-1880 UV-VIS Spectrophotometer was used to measure SO42− and NO3−.
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Fig. 1 Akyatan Lagoon and sampling stations
Results and discussion Assessment of water quality spatial variation Results indicated a spatial variation in Akyatan Lagoon among the stations for the water quality parameters (Fig. 2). Lagoon water temperature was expected to play a significant role in water hydrodynamics and chemical and biological processes (Davis and Fitzgerald 2004). Lagoon water temperature exhibited from 7.0 to 33.8 °C temperature range during the course of the study (Table 2). The lowest temperature was observed in January at S-5 (7 °C), located toward the center of the lagoon, and the highest temperature at S-1 in September (33.8 °C), located near the west coast of the lagoon. Lagoon temperature is recognized as a significant factor impacting freshwater, in association with low TDS Table 1 Geographic positions of the sampling stations Station no.
Elevation (m)
Latitude (north)
Longitude (east)
1
0.70
36° 39′ 51″ N
35° 12′ 20″ E
2
0.50
36° 38′ 38″ N
35° 14′ 06″ E
3
0.67
36° 37′ 29″ N
35° 15′ 55″ E
4
0.44
36° 37′ 18″ N
35° 17′ 05″ E
5
0.65
36° 36′ 00″ N
35° 16′ 59″ E
6
0.90
36° 37′ 03″ N
35° 18′ 05″ E
7
0.50
36° 36′ 14″ N
35° 18′ 05″ E
8
0.64
36° 35′ 32″ N
35° 18′ 06″ E
9
0.67
36° 36′ 22″ N
35° 19′ 24″ E
10
0.83
36° 35′ 22″ N
35° 19′ 25″ E
11
0.78
36° 34′ 33″ N
35° 19′ 20″ E
mixing into hyper-saline lagoon water (Diamantopoulou et al. 2008). A slightly alkaline nature was determined throughout the lagoon, indicated by pH and TAlk levels. Spatial variation in pH was minimal, with the lowest pH observed at S-1 (7.82 in November 2008) and highest at S-5 (9.13 in July 2008). In general, pH values were higher nearest to the center of the lagoon. However, the stations closest to the drainage channels, DC-1 and DC2, and the channel opening to the sea (i.e., stations S-6 to S-11) showed varying pH values based on the kind of water the station received at the time of sampling. For example, the station might have received drainage discharge or seawater on the sampling date. A similar trend was observed for TAlk. The minimum value was observed at S-5 (96 mg CaCO3/L, August 2008) and the maximum at S-11 (344 mg CaCO3/L, October 2008). However, an overall annual assessment showed that the seawater alkalinity (TAlk) was slightly lower than that of the lagoon water (211 mg CaCO3/L), and the Talk levels for the drainage channels (364 mg CaCO3/L for DC-1 and 310 mg CaCO3/L for DC-2) were higher than those for the lagoon (Table 2). The main factors affecting pH and alkalinity were DC-1, DC-2, the channel opening to the sea, precipitation, and evaporation, particularly in shallow depths. Turkdogan-Aydinol et al. (2012) stated that seawater is affected by temperature pressure, photosynthesis, and respiration activity of microorganisms. Moreover, temperature-dependent respiration by aquatic organisms and solar irradiation-dependent photosynthetic activities are other components of the ecosystem affecting spatial variation in pH and alkalinity (Davis and Fitzgerald 2004).
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Fig. 2 Spatial distribution of each water quality parameter derived from annual mean values of each station (S-1–S-11)
The spatial distribution patterns of TDS, EC, salinity, and Cl− exhibited similarities. TDS levels showed considerable variation, with a range of 20,892–175,824 mg/ L during the study period. The lowest TDS was determined in May at S-11, close to the seawater mixing zones (i.e., DC-1 and DC-2). The highest TDS was observed in September (a dry month) at S-1, a station
located on the west end of the lagoon with an absence of a freshwater input as a point source. Chloride (Cl−) also demonstrated a spatial distribution similar to TDS, with the lowest value at S-11 (in May) and the highest value at S-3 (in September). On site, the highest EC and salinity observations S-3 were 162 mS/cm and 119.6 ppt, respectively (in September), and the lowest
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Table 2 Annual lagoon water quality basic statistics (12 months×11 parameters N=132) Parameter
Unit
Min
Median
Mean
Max
SD
CV
T
°C
7.00
23.10
22.60
33.80
8.41
0.37
pH
-
7.82
8.30
8.31
9.13
0.27
0.03
EC
(mS/cm)
28.37
53.10
60.26
162.00
22.68
0.38
Salinity
(ppt)
17.50
34.40
39.99
119.60
16.61
0.42
DO
(mg/L)
2.00
5.53
5.92
9.38
1.61
0.27
−
Cl
(mg/L)
10,511
21,524
25532.6
88,697
12,041
0.47
TDS
(mg/L)
20,892
45,510
52154.8
175,824
25,054
0.48
TAlk
(mgCaCO3/L)
94
256
252.79
442.00
51.01
0.20
SO42−
(mg/L)
165
202
202.92
253.00
19.16
0.09
NO3−
(mg/L)
0.44
2.25
2.28
5.51
0.95
0.42
EC and salinity levels were determined at S-11 as 28.37 mS/cm and 17.5 ppt, respectively (in May). Relative to lagoon water, EC levels in the DC-1 drainage channel, which play an important role in dissolved ion balance, were very low within a range of 0.65–12.7 mS/ cm and an annual mean of 3.8 mS/cm. Similar results were found for DC-2, with an EC level between 0.3 and 7.3 mS/cm and an annual mean of 2.1 mS/cm. DC-1 and DC-2 annual salinity levels were 8.3 to 5.3 ppt, respectively. Compared to stations closer to the west coast of the lagoon, all water quality parameters showed decreased values at stations closer to the drainage channel discharges, i.e., DC-1 and DC-2, which deliver freshwater into the lagoon. Furthermore, annual respective levels of TDS, Cl−, EC, and salinity at 44788 mg/L, 22,830 mg/L, 55.7 mS/cm, and 36.5 ppt for TDS, Cl−, EC, and salinity in seawater, respectively, serve to control salinity in the lagoon with relatively high levels through dilution. TDS concentration is influenced by surface water runoff from point and nonpoint sources (Shin et al. 2013). The spatial distribution of SO42−, based on annual mean values, did not significantly vary (P =0.002) throughout the lagoon, and observed concentrations ranged from 165 to 253 mg/L (Fig. 2). S-1 and S-2 exhibited the highest and S-9 and S-10 the lowest concentrations of SO42. Lower SO42− levels were observed toward the center of the lagoon, and DC-1 and DC-2 showed, respectively, 73 and 103 mg/L SO42, which flowed into the lagoon. The annual mean SO42− concentration of the seawater was 190 mg/L, slightly lower than that for the lagoon. NO 3 − concentration varied among stations (Fig. 2). Annual mean NO3− concentrations ranged from 1.5 to 3.0 mg/L. The highest concentrations
were observed in S-1, S-2, and S-5, well above 2.5 mg/L, while S-10 and S-11 showed the lowest concentrations. The S-11 and S-10 NO3− concentrations can be explained by 0.83 mg NO3−/L (annual mean) in seawater flow entering the lagoon. High NO3− concentration is suspected to be the result of fertilizer use on agricultural crops. All water drained from the adjacent areas (i.e., Karataş district) reaches a catchment which is discharged in the drainage channels and reaches the lagoon. For several decades, increased eutrophication is one of the leading environmental issues in coastal and estuarine waters and threats to the health of marine ecosystems (Zhou et al. 2014). Increasing of soluble nutrients affects the ecological characteristics of all species living in lagoons. Having small water quantity, shallow depths, and restricted water exchange, lagoons are sensitive to human impacts, freshwater, and nutrient inputs (Kharroubi et al. 2012). However, increased NO3− concentrations surrounding S-1, S-2, and S-5 are likely to be due to relatively stagnant water around the stations due to low turbulence while the drainage water with relatively lower NO3− concentrations coming from the adjacent areas (i.e., Karataş district) is discharged into the drainage channels eventually reaching the lagoon. This negatively affects especially S-6, S-7, S-9, and S-10. The major factors affecting spatial variation in the water quality parameters among the 11 stations were determined as follows: (i) the shallow structure of the Akyatan Lagoon, which increases the impacts of temperature and wind; (ii) seawater and freshwater resource content and water discharge points into the lagoon; and
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(iii) varying freshwater input and evaporation output during the wet and dry months. Assessment of monthly variation in water quality Variations in surface water parameters of the Akyatan Lagoon for the winter months (December, January, February), spring (March, April, May), summer (June, July, August), and autumn (September, October, November) are presented in Table 3. In addition, the monthly variation of water quality parameters based on the average of all stations is depicted in Fig. 3. The lagoon water temperature never fell below freezing, and the minimum observed temperature was 7.0 °C in January. The annual mean water temperature was 22.6 °C, and higher temperature values were observed during the summer and autumn months. In winter, DC-1 and DC-2 temperatures varied similarly to the lagoon. However, in summer and autumn, the temperatures of both channels were lower compared with the lagoon. Seawater exhibited a mean annual temperature of 22.3 °C, and in most months, particularly in summer and autumn, the seawater temperature was lower than that of the lagoon. The observed annual variation in Akyatan Lagoon temperature was consistent with a previous study by Dural (2004). The shallow lagoon structure plays an important role in poor temperature distribution in terms of thermal stratification and other water quality parameters. Variation in pH for winter, spring, summer, and autumn was 7.97–8.50, 7.92–8.65, 7.83–9.13, and 7.82– 8.97, respectively. Mean pH values were 8.29 in winter, 8.19 in spring, 8.41 in summer, and 8.36 in autumn. These values were slightly higher than those reported for other Mediterranean lagoons, particularly for summer and autumn (Table 4). DC-1 exhibited an increased pH value (8.55) relative to the lagoon in winter and a decreased value for the other seasons. DC-2 showed lower pH values than all other stations in the lagoon for the four seasons. TAlk content was stable and consistent with the pH levels indicated above. On average, seasonal mean TAlk concentrations were approximately 268, 277, 224, and 241 mg CaCO3/L for winter, spring, summer, and autumn, respectively. During the study period, TDS, Cl−, EC, and salinity values presented significant variation for each season (Table 3). Climatic conditions can markedly influence the seasonal variation in water quality. TDS reached a maximum value due to increased evaporation from high
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weather temperatures, which ranged between 25.6 and 34.4 °C during the June–November period. Another factor increasing the impact of evaporation was wind velocity, which was especially high during the spring months with a maximum of 85.7 km/h. Furthermore, summer and autumn precipitation was very low (3.16 kg/m2). Increased salinity was observed at both ends of the lagoon where evaporation was assumed to be higher than precipitation due to the increased shallowness, temperature, and wind conditions. Because the maximum TDS values (175,824 mg/L) were observed shortly after the first fall of precipitation in October, it is plausible that salt deposits dissolved back into the lagoon water and intermittently resulted in increased TDS values. The annual mean DC-1 and DC-2 TDS values were 2,474 and 6,884 mg/L, respectively. However, as a result of the typically intense agricultural irrigation during the summer period, lower TDS values were observed in the drainage channels (i.e., 400–870 mg/ L DC-1, 458–1,306 mg/L DC-2). Therefore, it is reasonable that relatively lower TDS values were observed at stations adjacent to the two drainage channels discharging into the lagoon. The preceding discussion points also support seasonal variation in EC, Cl−, and salinity in the drainage channels and lagoon. During the study period, TDS, EC, Cl−, and salinity values presented significant seasonal variation. The mean TDS concentrations were 51,045, 54,454, and 65,607 mg/L for winter, summer, and autumn seasons, respectively, whereas the spring results were notably lower at 38,736 mg/L. EC values varied monthly between 28.37 and 162 mS/cm; Cl− and salinity concentrations ranged between 10,511 and 88,697 mg/L and 17.5 and 119.6 ppt, respectively (Table 3). EC annual mean was 60.3 mS/cm with 95 % statistical confidence. In winter, EC values varied from 38.5 to 92.9 mS/cm, while Cl− and salinity concentrations ranged, respectively, from 17,517 to 43,047 mg/L and 24.5 to 65.9 ppt. In spring, results showed decreased EC values, from 28.4 to 69.0 mS/cm, and Cl− and salinity concentrations showed a similar decrease in spring, from 10,511 to 29,032 mg/L and 17.5 to 47.2 ppt, respectively. In summer, EC varied from 39.3 to 105.7 mS/cm, Cl− from 5,016 to 47,302 mg/L, and 25 to 75.2 ppt for salinity. EC values during autumn exhibited values between 33.8 and 162 mS/cm, consistent with previous seasons. However, determined results indicate that Cl− and salinity concentrations ranged between 13,565 to 88,697 mg/ L and 21 to 119.6 ppt, respectively. EC and salinity also
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Table 3 Seasonal variation in water quality for the Akyatan Lagoon Parameter
Unit
Min
Median
Mean
Max
SD
CV
Winter (December, January, February) T
°C
7.0
11.5
10.6
14.3
2.37
0.22
pH
-
7.97
8.32
8.29
8.50
0.17
0.02
EC
mS/cm
38.5
57.0
59.5
92.9
12.62
0.21
Salinity
ppt
24.5
37.7
39.66
65.90
9.70
0.24
DO
mg/L
5.67
8.32
8.10
9.38
0.94
0.12
Cl−
mg/L
17,517
22,524
24,695
43,047
5811.9
0.24
TDS
mg/L
34,392
48,620
51,045
76,422
9302.9
0.18
TAlk
mgCaCO3/L
206
263
267.97
322
24.50
0.09
SO42− NO3−
mg/L
178
209
207.33
248
19.19
0.09
mg/L
1.29
2.25
2.14
3.33
0.45
0.21
Spring (March, April, May) T
°C
18.7
22.1
22.8
27.2
2.27
0.10
pH
-
7.92
8.19
8.19
8.65
0.20
0.02
EC
mS/cm
28.37
47.80
48.11
69.00
7.57
0.16
Salinity
ppt
17.50
30.50
30.58
47.20
5.61
0.18
DO
mg/L
2.97
5.30
5.24
6.61
0.91
0.17
Cl−
mg/L
10,511
19,021
19,340
29,032
3498
0.18
TDS
mg/L
208,920
39,008
38,735
56,558
6858
0.18
TAlk
mgCaCO3/L
214
278
277
344
38.4
0.14
SO42−
mg/L
173.00
191.00
194.76
239.00
14.78
0.08
NO3−
mg/L
0.77
2.35
2.52
4.93
0.97
0.38
28.20
31.20
31.35
33.60
1.80
0.06
Summer (June, July, August) T
°C
pH
-
7.83
8.35
8.41
9.13
0.33
0.04
EC
mS/cm
39.30
58.40
62.80
105.70
17.52
0.28
Salinity
ppt
25.00
38.70
42.33
75.20
13.22
0.31
DO
mg/L
3.88
4.81
5.00
7.19
0.88
0.18
Cl−
mg/L
15,016
24,026
26,134
47,302
8,453
0.32
TDS
mg/L
31,468
49,038
54,454
98,384
17,603
0.32
TAlk
mgCaCO3/L
94
232
224
292
42.59
0.19
SO42−
mg/L
172
215
215
253
16.46
0.08
NO3−
mg/L
0.60
2.43
2.41
4.81
0.95
0.39 0.23
Autumn (September, October, November) T
°C
16.10
26.20
25.86
33.80
5.97
pH
-
7.82
8.38
8.36
8.97
0.30
0.04
EC
mS/cm
33.80
59.70
71.68
162.00
37.17
0.52
Salinity
ppt
21.00
38.95
48.14
119.60
26.64
0.55
DO
mg/L
2.00
5.51
5.29
7.40
1.17
0.22
−
Cl
mg/L
13,565
24,927
32,602
88,697
20,343
0.62
TDS
mg/L
25,846
49,364
65,606
175,824
43,379
0.66
TAlk
mgCaCO3/L
126
235
240
442
71.90
0.30
SO42−
mg/L
165
190
192
230
16.97
0.09
NO3−
mg/L
0.44
1.67
2.02
5.51
1.26
0.62
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Fig. 3 Monthly variation of water quality parameters derived from station averages (S-1–S-11)
varied over consecutive months depending on meteorological conditions (temperature, precipitation), seawater intrusion, turbulence, and drainage channel discharge. High EC and salinity levels were observed for December and July through November. During these months, EC and salinity were well over 60 mS/cm and
40 ppt, respectively. EC and salinity reached maximum values in August and September, with 75 and 88 mS/cm for EC and 51 and 59 ppt for salinity, respectively. Decreased precipitation and increased temperature, resulting in higher evaporation in August and September, were probably responsible for higher EC
Environ Monit Assess (2014) 186:7631–7642
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Table 4 Comparison of physicochemical characterizations of Mediterranean coastal lagoons Lagoon
Akyatan, Turkey (Present sudy) Ölüdeniz, Turkey (Tuncel and Tugrul 2007) Korissia, Greece (Diamantopoulou et al. 2008) Lesina, Italy (Roselli et al. 2009) Nador, Morocco (Ruiz et al. 2006) Ria Formosa, Portugal (Loureiro et al. 2006) Vistonis, Greece (Markou et al. 2007)
Concentrations T (°C)
pH
Salinity (ppt)
DO (mg/L)
SO42− (mg/L)
NO3− (mg/L)
7.0–33.8
7.82–9.1
17.5–119
2–9.38
165–253
0.44–5.51
25–25.5
8.3–8.4
38.7–39.2
6.78–7.61
–
0.028–0.23
13.5–26.2
8.0–8.6
15.6–>50
4.6–11.2
–
0.41–0.47
10.3–27.5
8.3–8.7
6.01–37.56
85.5–120*
–
–
–
7.95–8.7
38–39.5
–
605–1,584
–
23–24.7
–
36.4–37.0
7.1–8.3
–
0.25–0.60
6.4–28.6
8.1–8.9
0.6–12.9
4.2–8.5
–
0.022–0.124
EC, Cl− , TDS, and TAlk values were not evaluated in the other lagoons *
(% sat.)
and salinity. These results indicated lower EC and salinity values from January through July (i.e., below or equal to 60 mS/cm and 40 ppt, respectively); however, the lowest values were observed from March through May for both parameters. It should be noted that hypersalinity is the typical lagoon water condition and lower salinity values are the result of dilution from precipitation, drainage water, and seawater. The freshwater flowing to the lagoons causes to reduce the salinity of the lagoon water (Kharroubi et al. 2012). Anion concentration varied markedly depending on contaminant type and season. SO42− concentration did not show significant seasonal changes. The results showed that mean seasonal concentrations were similar, with approximately 207 mg/L in winter, 195 mg/L in spring, 216 mg/L in summer, and 193 mg/L in autumn. Monthly SO42− variation (Fig. 3) was similar to SO42− spatial distribution, and its concentration varied between 180 and 224 mg/L. A distinct trend in the spatial distribution and monthly variation of SO42− was not exhibited in the lagoon. This almost even distribution of SO42− is the result of rather cold seawater movement toward the lagoon from the bottom and dispersion and diffusion of SO42− throughout the lagoon. Concurrently, relatively warmer lagoon water is pushed upward. Unlike SO42−, NO3− concentrations showed significant variation. On average, NO3− concentrations were approximately 2.14, 2.52, 2.41, and 2.02 mg/L for
winter, spring, summer, and autumn, respectively. NO3− concentration is a strong indicator of the level of fertilizer used during the agricultural season as the drainage channels direct all water flow drained from the area to the lagoon. Monthly variation in NO3− concentration was also determined and is summarized in Fig. 3. May and June exhibited the highest NO3− concentration with values of 3.62 and 2.78 mg/L, respectively, and the lowest values were observed for April and October, with 1.65 and 1.42 mg/L, respectively. The nitrate content varied between 1.42 and 2.5 mg/L for the remaining months. The results of the present study were compared with data from six other Mediterranean lagoons, which are summarized in Table 4. These include lagoons from Turkey, Greece, Italy, Morocco, and Portugal, and the studies were conducted within the last 5 years. The pH range was similar to the other Mediterranean lagoons, but the Akyatan Lagoon had a slightly broader range between 7.82 and 9.13 when compared to pH levels of between 8 and 9 for the other lagoons. A comparison of salinity levels showed that the Akyatan and Korissia Lagoons demonstrated hyper-salinity well over values for the Mediterranean with approximately 35 ppt. DO levels indicated that saturation levels and even oversaturation were reached for some lagoons, such as Korissia and Lesino,
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Table 5 Spearman rank coefficients among lagoon water quality parameters Element
T
T
1
pH
0.19
EC
0.13
0.25
Salinity
0.14
0.25
0.996*
1
DO
−0.74**
0.09
0.04
0.04
1
−
pH
EC
Salinity
DO
Cl-
TDS
TAlk
SO42−
NO3−
1 1
Cl
0.12
0.28
0.98*
0.98*
0.05
1
TDS
0.09
0.28
0.957
0.958*
0.07
0.95*
TAlk
−0.18
−0.23
−010
−0.09
−0.05
−0.09
−0.09
1
SO42−
0.008
−0.08
0.31
−0.09
0.11
0.30
0.33
−0.19
1
NO3−
0.08
−0.18
0.29
0.29
−0.20
0.27
0.29
0.14
0.29
1
1
The significance of bold entries in Table 5 represented relatively better correlation Statistical significance *P
