Status of coastal water quality at Holbox Island ... - WIT Press

© 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email witpress@witpress.com Paper from: Coastal Environment, CA Brebbia (Editor). ISBN 1-85312-921-6

Status of coastal water quality at Holbox Island, QuintanaRoo State, Mexico Kim Chi Tranl, D. Valdes2, J. Herrera2, J. Euan2, I. MedinaGomez2 and N. Aranda-Cirero12 1School of Policy Studies, Kwansei Gakuin University, Japan 2 CINVESTA V-Merida, Yucatan, Mexico

Abstract Holbox Island, with its coastal lagoon, Yalahau Lagoon, is a relatively undisturbed ecosystem that is currently under threat from unplanned and intensive urban development. This paper reports the results of analysis to determine the temporal and spatial variations of standard physical and chemical parameters and to evaluate the relationships among these parameters. Water samples collected from 43 stations during the rainy season in August 1999 and August 2001 were analysed using standard methods, The results indicate that, in general, the area is relatively undisturbed by human influence. Water quality at stations in the proximity of boating and dumping activities shows higher degradation than at other stations within the lagoon. The opening of the canal in Santa Paola in August 2001 has helped increasing the current circulation in the lagoon, leading to the improvement of water quality of the lagoon. Results from the Data Flow Technique, obtained at different temporal seasons (August 2001and January 2002), corresponding to the rainy and “Nortes” (winter storm) seasons show the detailed profiles of the Yalahau Lagoon at various seasons. The higher spatial variability in the hydrology observed in August could be due the south region of the lagoon is mainly influenced by freshwater discharges; instead the northwest region shows a restricted water interchange. However, during January the north-winds show an influence in all the system favoring less spatial heterogeneity in its hydrology.

1 Introduction The study area includes the coastal zones of Holbox Island and the adjacent Yalahau Lagoon, which are in the Quintana Roo State, northeast of the Yucatan


332

Coastal Environment

Peninsula, Yalahau Lagoon is located between the fishing communities of Chiquila to the south and Holbox Island to the north, between the parallels 21026’ and 21036’ of North latitude and the meridians 87°08’ and 87°29’ West longitude [1], Yalahau Lagoon has been part of the Protected Area, “Yum Balam”, in the Municipality of Lazaro Cardenas since 1994 and no programme for development exists for the lagoon and its coastal ecosystems. The area is a rich nursery for sharks, turtles, fish and many other living marine resources. The whole region is of a karstic nature with no surface rivers; freshwater discharges are from underground sources that reach the surface through springs called “ojo de aqua” or “cenotes” [2]. Recent urban development, which is rapidly taking place in Holbox Island (essentially for the tourist industry), might affect the quality of the coastal water and the health of the ecosystem. As part of a larger, on-going study, this paper reports the results of analyses to determine the temporal and spatial variations of standard physical and chemical parameters, to evaluate the relationships among these parameters as well as their relationship to the development process taking place in the island. Data from the water samples collected and analysed in August 1999 and August 2001 will be reported. Results from the Data Flow Technique, obtained at different temporal seasons (August 2001 and February 2002), corresponding to the rainy and “Nortes” (winter storm) seasons show the detailed profiles of the Yalahau Lagoon at various seasons. These results provide an opportunity to determine whether the natural and development processes have impact on the conditions and health of coastal ecosystems around Holbox Island.

2 Material and methods In this study, two different sampling procedures and analyses were performed. 2.1 For water analyses In the first sampling procedure, water was sampled at separate stations along the coast of the Gulf of Mexico and of the lagoon (see Figure 1) in August 1999 and August 2001, corresponding to the rainy seasons. Sampling stations were established at 43 sites on the basis of reference points determined by the local fishing community [1]. Water samples were collected from the middle of the water column depth because no stratification occurs in the area, and were stored in plastic bottles. Water analyses were performed following standard methods reported elsewhere [3]. 2.2 For data flow technique 2.2.1 Sampling procedure and water analysis

In the second sampling procedure, used in the Data Flow Technique, samplings were carried out over two periods (August 2001 and January 2002), In each visit 40 stations were sampled (Fig.2), in situ, temperature, dissolved oxygen and


Coastal Envitwmnent

333

salinity were recorded with a multiprobe YSI-85: Water samples were collected at surface level and used for analysis of dissolved inorganic nutrients as nitrites (NO1), ni~ates (NO~), ammonium (lW&) soluble reactive phosphorus (SRP), soluble reactive silice (SRSi) and Chlorophyl-a (Chl-a), all them were performed following standard methods [4]. Latitude ——..

.

I

I

——

21wl--

~

Longitude

Figure 1: Sampling stations in Yalahau Lagoon for the water analyses.

2.2.2 Spatial analysis

In order to establish the spatial variability of the lagoon under different weather conditions, an instrument system for high-speed mapping of temperature, salinity, chlorophyll a and transparency called DataFlow@.[5]. This instrument is adapted flow-through sampling for the shallow coastal environment using a small boat, include a flexible sample scheme, and sensors interfaced with a datalogger to automate the measurement of multiple vwiables in a spatial context through GPS integrated. The continuous trip in each sampling can be observed in the Figure 2, more than 2000 data points of each variable were recorded for each period, The collected data were analyzed to estimate de Variability Index (VI), which produce an average percentage of change from nearest neighbor for each point in the transect.

where: Z = parameter, x = lat.; y = long.


334

Coastal Environment

2.2.3 Multivariate

analysis

The characterization included principal components analysis (PCA) and cluster analysis, in order to determine the water quality variables responsible of the hydrologic behavior of the lagoon, and in order to aggregate stations of similar influence to establish a zoniphication of the system respectively.

2L6

-8?,45

-et. 4

-d 35

-8+3

-oi25

-8t2

-af.15

-0}.1

Figure 2: Sampling stations for the DataFlow technique.

3 Results and discussion In general, the Yalahau Lagoon acts as an estuary in the rainy season because they receive freshwater (from the atmosphere and from the continent via freshwater springs) that is rich in nitrate and silicate, and poor in oxygen. At the sampling time in both years, there was not much rain although it was a rainy season and with the high temperature of August, evaporation was greater than precipitation, and as a result, the salinity was commonly above the marine values. The eastern zone of Yalahau lagoon showed the highest salinity, as observed at Stations 16, 19, 20 and 21, especially in August 1999, due to their geographic isolation which favours limited current circulation and high evaporation. When comparing the two samplings, the salinity of these stations in August 2001 is lower than that of August 1999, possibly due to the opening of the canal at Santa Paola (station 17), which leads to more current circulation and more exchange of water between the lagoon and the Gulf of Mexico. The cluster analysis from the Data Flow Technique grouped the 40 sampling sites of the Yalahau Lagoon into zones of similar influence and water quality characteristics (Hydrological Zones, HZ). In August 2001 the lagoon presented seven HZ (Fig. 3a) In the east of the lagoon can be observed three HZ, which


Coastal Ewiwntnent

335

present a salinity gradient. The HZ-I showed the lower salinity, according with the freshwater springs and runoff, and was called estuarine zone. The HZ-II, represents a transition zone and the HZ-III named hyper-salinity zone showed the highest salinity values, due to probably high residence time of water as a consequence of the inlet of the lagoon is located in the opposite site of these region, The HZ-IV and V are located near the Santa Teresa and Holbox towns respectively, suggesting the urban influence toward the coastal water quality, The HZ-VI is influenced for freshwater and urban activities from Chiquild town. The station at the mouth of the lagoon in southwest Holbox Island represents the “marine zone”, HZVII. In contrast, in January 2002, the lagoon presents six HZ (Fig. 3b). In this season a mayor influence of marine water was observed. The transition zone disappears while estuarine (HZ-I) and hypersalinity zones (HZ-II) are bigger. A HZ-III in the central north of the lagoon is present while the HZ-IV and HZ-V remain. The HZ-V (marine) is bigger and the influence of Chiquilfi town was diluted by the marine low-nutrients water that penetrates to lagoon during northwinds season as observed in other coastal system of the region [6]. The higher spatial variability in the hydrology observed in August could be due the south region of the lagoon is mainly influenced by freshwater discharges, instead the north-west region due show a restricted water interchange, the water column increase its temperature and salinity. However, during January the north winds show an influence in all the system favoring less spatial heterogeneity in its hydrology. Dissolved oxygen, an important indicator for water quality, was lower in August 1999 compared to August 2001 but there was no indication of excessive bacterial decay: average values of 3.5 ml 1“*(Table 1) and 6.05 ml 1-1(Table 2) for August 1999 and August 2001, respectively, are comparable to values reported for other coastal waters in the region. A low level of dissolved oxygen and 10w percentages of oxygen saturation were observed in August 1999 at Station 39, and are likely to be the result of the proximity of the village dump, which may deteriorate water quality through excessive bacterial decomposition of organic material from garbage, Dissolved oxygen levels were relatively 10w at Stations 1, 37 and 38, indicating the negative impact of human activities (such as boating, fish cleaning and picnicking) on the quality of coastal water [3]. In the August 2002 sampling, the dissolved oxygen levels at those stations were improved, possibly due to more current circulation during this period from the opening of the canal in Santa Paola. The lowest values for dissolved oxygen and for the percentage of oxygen saturation were recorded from the freshwater springs, as may be expected given that this water originates from underground. In the presence of oxygen, a portion of the ammonium is oxidized to nitrate, which is also an important nutrient for plants [7]. A predominance of reduced (ammonium and ammonia) over oxidized (nitrite and nitrate) forms was observed at all sites (Tables 1 and 2). In general, the concentration of ammonium in water in August 2001 (1.95 PM) has been improved compared to August 1999 (3.7 @l). This observation is similar to that for dissolved oxygen, possibly as a result of improved current circulation in the lagoon in August 2001. The more


336

Coastal Environment

Figure 3: Hydrological Zones (HZ) of Yalahau lagoon as a result of cluster analysis.

current circulation, the more dissolved oxygen and the less ammonium concentration is observed because ammonium is produced in more anoxic conditions [8]. Also as the current circulation is improved, ammonium gets exported to the sea. However, Stations 1, 38 and 39 had relatively high ammonium concentrations in both samplings, suggesting that, at these sites, ammonification of organic nitrogen is being carried out at elevated rates, as noted previously, human activities are concentrated in these stations. Phosphate concermations were also generally low (Tables 1 and 2). Nonetheless, samples from Stations 5 and 10 in August 1999 and from Station 35 in August 200 I showed relatively high phosphate concentrations, although not at levels which can induce eutrophication [7]. High silicate concentrations were


Coastal Environment

337

recorded from all stations with the average values for August 1999 and August 2001 were 49 and 42 pM, respectively, which are normal for this type of lagoon. Table 1: Physico-chemical data for water samples collected in August 1999. Station

Temp. “c

1 2

Salinity

Oxygen

Ammonium

Nitrite

Nitrate

Phosphate

Silicate

%0

ml l“’

pM

VM

pM

VM

pM

0.10 0.09

20.51 21.59

31.0 31.0

39.52 40.24

2.31 3.22

5.71 3,18

0.13 0.16

0.23 0,20

3

31.0

40.33

3.64

3,90

0.12

0.12

0.08

16.92

4

31.0

36.78

3.92

1.12

0.09

0.17

0.05

11.08

5

31.0

41.30

2.24

3.68

0.18

0.12

1.34

26.48

6

30.5

42,22

2.94

3.16

0.63

1.10

0.21

105,13

7

31.0

36.84

3.64

1,11

0.09

0.09

0.03

12.59

8

31.0

43.47

2.66

4.25

0.37

0.44

0.35

104.25 128.66

9

31.5

45.42

3.78

6,51

0.35

0.43

0.32

10

31.0

36.91

3.64

1.79

0.07

0.13

0.10

9.83

11

32.0

44.11

3.78

5.93

0.45

0.46

0.37

92.24 101.22

12

32,0

44,57

3.64

4,34

0.38

0,49

0.21

13

31.0

36.82

3.36

1.35

0.08

0.12

0.00

13.57

14

32.5

45.46

3.50

4,53

0.29

0.39

0,27

94.18

15

33.0

46.96

3.78

2,59

0.28

0.26

0.17

91.21

16

33.0

48.44

5.04

4,44

0.38

0.29

0.34

101.28

19

30.0

49.07

1.54

2,61

0.17

0.10

0.00

91.04

20

31.5

47.78

2.73

5,73

0.46

0.56

0.24

101.22

21

32,0

48.03

2.94

5.96

0.37

0.49

0.20

102.28

22

31.5

41,77

2.80

11,08

0.26

0.27

0.21

85.63

23

32.0

40.41

3.36

3.17

0.36

0.35

0,32

98.35

24

32.5

41.67

3.78

4.20

0.46

0.95

0.31

67,20

25

32.0

41.12

4.34

4,71

0.41

0.35

0.34

73.21

26

34.0

41,97

5.18

2.94

0.32

000

000

38.06

27

33.0

42,07

4.90

2.04

0.16

0.14

0.00

27.56

28

32.5

39.59

4.62

1.68

0,13

0,20

29

33.0

38.01

3.92

3.41

0.18

0.23

0.00

25.61

30

33.0

36.56

5.74

2,42

0.18

0.16

0.24

15.26

31

33.0

36.79

5.18

2,71

0,13

0,18

000

19.12

22.31

32

33.0

36.77

4.06

3.55

0.19

0,11

0.00

13,38

33

31.0

33.92

4.06

2.07

0.07

0,10

0.00

22.24

34

30,5

35.99

3.92

2.31

0.08

0.08

0.05

11.21

35

29.5

36.46

3.22

3.05

0.08

0.03

0.10

7.14

36

28.0

36.73

4.34

1.71

0.05

0.12

0.17

10.10

37

30,8

37.43

2.66

5.22

0.16

0.13

0.00

10.72

38

29.0

38.01

1,96

7.42

0.19

0.05

0.00

18,52

39

29,0

38.11

2.66

7.03

0.16

0.18

0.00

15,25

40

31.0

22.27

2.10

3.85

0.23

0,25

0.16

81.21


338

Coastal Environment 41

25.0

0.00

0.56

2.36

1.00

39.41

0.14

102.28

42

32.0

37.99

3.78

3.31

0.13

0.14

0.18

7.73

43

31.0

37.7’7

3.36

1.33

0.08

0.02

0.00

3.83

44

N,A.

0.00

N.A.

1.93

0.76

44.67

0.02

123.46

31.30 1.6

39.2 7.8

3.50 1

3.7 2.0

0.2 0.2

1.2 6.0

0.2 0.2

49.3 40.1

0.0 49.1

0.6

1.1

0.0

0.0

0.0

3.8

5.7

11,1

1,0

39.4

1.3

128.7

Averaze Std. &l.

Minimum 25.0 Maximum 34.0

Note: data are not provided for Stations 17 and 18 In the multivariate analysis of results obtained from the Data Flow Technique, in the rainy season (August 2001) the principal component analysis (PCA) identified four composite variables (hereafter called PCI, PC2, PCS,PC4;Table 3) that indicate four separate modes of variation in the data. PC I had high factor loadings for SRSi and pH and was therefore designated as the “freshwater” component. PC2 was composed of NH4+ and temperature and was called the “denitrification” component. PC3 was correlated with the salinity. SRP was the only variable include in PC4. The four principal components accounted for 75?40 of the total of the variance of the original variables. During “Nortes” season (January 2002) the PCA was similar and the four principal components were also identified. PC, was identified for N03- and SRSi and was designated as the “freshwater” component. PC2was composed Ch-a and temperature and was called the “phytoplankton” component. PC3 and PC4 were correlated with the salinity and SRP, respectively, The four principal components accounted for 70% of the total of the variance of the original variables, The PCA indicates that the variables, which determinate the PC 1 and PC2 change according to temporal season, however, the PC3 and PC4, remain similar. Table 2: Physico-chernical data for water samples collected in August 2001. Station Temp. Salinity Oxygen Ammonium Nitrite “c

~

Nitrate Phosphate Silicate

p

KM

PM

WM

PM

PM

38.24

6.67

1.79

0.06

0.15

006

8.63

%0

1 2

30.6 30.9

42.76

5.51

1,85

0.06

0.19

0.10

23.76

3

32

40.72

6.91

1.71

0.03

0.28

0.14

17,55

4

28,9

36.61

4.91

1.10

0.03

0.06

0.05

6.93

5

32.7

40,87

10.03

2.24

0.04

0.06

0.05

14.88 40.78

6

32.1

42.09

8.09

1.21

0.00

0.03

0,03

7

27.6

36.51

4.96

1.77

0.04

0.07

0.15

6.75

8

33

42.83

9.63

1.67

0,04

0.17

0.05

40.03 138.73

9

31.8

47.74

4.17

1,75

0.15

0.38

0.17

10

27.4

36.61

5.15

1.62

0.02

0.02

0.20

6.36

11

32,4

44.27

10.1

0,84

0.13

0.14

0.09

60.91

12

31

44.35

7.15

1.24

0.14

0.28

0.09

105.26

13

27.3

36.63

4.95

0.57

0.07

0.06

0.21

7.17


14 15 16 17

30.8

44.46

6.85

1.20

0.18

0,38

0.13

103.31

31.2

45.32

6.21

1.36

0,17

0.48

0.21

103.6

45,69

6.61

1.60

0.24

0.28

0.21

111.8

37.94

5.97

1,41

0.01

0.05

0.02

5.58

1.15

124.28

31.2 33.4

19

30.8

45,12

3.92

1.44

0.21

0.24

20

30.6

46.11

4,3

2.71

0.19

0.46

0.12

95.40

1.81

0,31

0.46

0.24

141.15 72.94

21

30.3

44,58

5.29

22

31,1

42.31

4.01

2.14

0.06

0.33

0.07

23

31.4

34.14

4,28

2,09

0.25

0.44

0.24

82.06

24

31.3

42.52

5.97

1,82

0.09

0.13

0.16

56.69

25

32.2

41.80

4.39

3.01

0.01

0.03

0.75

35.57

26

32.1

41,70

7,08

2.49

0.07

0.23

0.02

41.22

27

32.5

41.30

8.55

1,29

0.18

0.24

0.09

39.10

28

31.7

4 I .94

6.06

I .90

0.04

0.35

0.10

41.42

29

31.6

41,77

7.08

1.10

0.07

0,24

0.02

39.78

30

32.7

40.26

8.49

1,56

0.07

0.18

006

31.24

31

33.7

39.54

6.7

1.89

0.05

0.18

0.13

22,02

32

34.6

39.86

10.62

1.44

0.14

0,34

0.04

28.04

33

30.6

36.80

2,28

0.69

0.06

0.17

0.07

10.85

34

32.1

36.62

3

0.88

0.26

0.09

11.51

35

30.9

36.57

8.45

0.91

0.03

0.12

12.34

5.078

36

29.8

36.63

8.05

0.32

0.01

0.03

0.09

7.78

37

28.5

36.72

10.57

1.56

0.00

0.14

0.13

6.75

38

29.2

37.08

6.03

3.34

0.07

0.24

0.16

8.55

39

29.4

39.36

5.48

3.92

0.21

0.41

0.28

16.17

40

31.3

36.264

6.06

0.84

0.21

0.05

18,05

41

25.7

1.0

0,75

0.77

I ,05

38.09

0.34

102.28

42

30.1

41.19

4.5

1.14

0.02

0.06

0.14

25.99

43

29.6

38.60

4.04

1.44

0.00

I ,07

0.14

9.216

30.9

40.70

6.05

1.95

0.12

1.06

0.42

42.43

1.8

3.26

2.23

1.43

0.16

5.52

1,79

39,92

1.0 47,74

0.75 10.62

0.32 7.78

0.0 1.05

0.02 38.09

0,02 12.34

5.08 141.15

Averaze Std. tiV,

Minimum 25.7 Maximum 34.6

Note: data are not provided for Station 18 Table 3: Principal component analysis in August 2001, Yalahau Lagoon. Variance

Variable

PrincipalComponent Pcl

SRSi, pH

31%

PC2

NN+ , “C

27%

PC3

Psu

11%

Pcq

SRP

Total

I

6 variables

6% I

75%


340

Coastal Environment

Table 4: Principal component analysis in January 2002, Yalahau Lagoon. Principalcomponent Pcl PC2 PC3 PC4 Total

Variable NOj , SRSi Ch-a,

‘C

Psu SRP, 02 7 variables

Variance 34% 22% 9% 5% 70%

4 Concluding remarks These data show that the waters surrounding Holbox Island and particularly within Yalalau Lagoon are relatively unpolluted. When comparing the water quality of the two samplings, August 1999 and August 2001, that of the latter seems to be better, possibly thank to the opening of the canal in Santa Paola, leading to higher water circulation in the lagoon.

References [1] Jim4nez-Sabatini, T., Aguilar-Salazar, F., Martfnez-Aguilar, J., FigueroaPaz, R., & Aguilar-Cardozo, C., A fishing vision on Yalahau Lagoon in Holbox area, Quintanaroo State, Mexico. In: Publication of Federaci6n Regional de Sociedades Cooperatives de la Industria Pesquera del Estado de Quintana Roo and Instituto National de la Pesca, Mexico, 35 pp., 1998. [2] Capurro, F.L., Estado actual de las investigaciones sobre el uso de] ambiente costero. Proc. of the workshop Australia-Mkxico on Marine Sciences, ed. E.A.Chavez, Mexico, pp. 127-132, 1989. [3] Tran, K.C., Valdes, D., Euan, J., Real, & E., Gil, E., Status of water quality at Holbox Island, Quintana Roo State, Mexico. Aquatic Ecosystem Health and Management (accepted for publication, 2002). [4] Strickland, J., & Parsons, T. A practical handbook of seawater analysis. In: Bulletin 167 (second edition). Fisheries Research Board of Canada, Ottawa, 310pp, 1972. [5] Madden, C.J.& Day, J.Jr, An instrument system for high-speed mapping of chlorophyll a and physico-chemicai variables in surface waters. Estuaries, 15(3), pp. 421-427, 1992. [6] Herrera-Silveira, J.A,, Ramfrez, J.R,, & Zaldivar, A,J., Overview and characterization of the hydrology and primary producer communities of selected coastal lagoons of Yucathn, Mdxico. Aquatic Ecosystem Health and Management, 1, pp. 353-372, 1998. [7] Valdes, D. & Real, E,, Variation of vitrification rates in Chelem lagoon, Yucatan, Mexico. Indian Journal of Marine Sciences, 27, pp. 149-156, 1998. [8] Corredor, J,E, & Morel], J., Assessment of inorganic nitrogen fluxes across the sediment-water interface in a tropical lagoon. Estuarine Coastal and Shelf Science, 28, pp 339-345, 1989.