coastalwaterqualityassessmentintheyucatan peninsula...

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Ocean & Coastal Management 47 (2004) 625–639

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Coastal water quality assessment in the YucatanPeninsula: management implications

Jorge A. Herrera-Silveiraa,�, Francisco A. Cominb,Nancy Aranda-Cirerola, Luis Troccolic, Luis Capurroa

aMarine Resource Department, CINVESTAV-IPN Unidad Merida, Carretera Antigua a Progreso km.

6,97310 Merida Yucatan, C.P., MexicobInstituto Pirenaico de Ecologıa-CSIC, Zaragoza Spain

cUniversidad de Oriente, Venezuela

Abstract

The coastal zone of Yucatan Peninsula has been recognized as the most important

environment to the economic development of this region. Different projects have been

conducted in this area, including harbors, tourist, commercial, and aquaculture infrastructure,

among others. However, there is no information available on what are ‘‘normal’’

concentrations of dissolved inorganic nutrients (DIN) and chlorophyll-a (Chl-a) for these

regions. In order to establish the base-lines of selected water quality parameters four coastal

areas of the north of Yucatan Peninsula (SE, Mexico) a monitoring program has been

conducted since 1999 in four localities of the north of Yucatan which show differences on the

kind and intensity of anthropogenic impacts. The results show that Dzilam is the site with the

best water quality conditions and a conservation program must be implemented, while Sisal

and Progreso are the ports with the worst water quality and where different strategies must be

implemented, such as water management of the shrimp farm effluents through constructed

wetlands in Sisal, or water waste treatment and facilitation of water circulation in the Progreso

port. Other results from phytoplankton community and submerged aquatic vegetation

indicate that these components must be incorporated into water quality programs in order to

effectively identify the problems and monitor the success of management strategies. These

results can be used to understand the linkages between stressors from the activities and

see front matter r 2005 Elsevier Ltd. All rights reserved.

.ocecoaman.2004.12.005

nding author. Tel.: +5299 99 812960; fax: +5299 99 812334.

dress: [email protected] (J.A. Herrera-Silveira).

www.elsevier.com/locate/ocecoaman

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J.A. Herrera-Silveira et al. / Ocean & Coastal Management 47 (2004) 625–639626

attributes of the water quality. A joint state-federal and academic effort to improve the

conditions and increase the sustainability of the coastal zone is favored.

r 2005 Elsevier Ltd. All rights reserved.

1. Introduction

The Yucatan Peninsula (YP), with 1500 km of coast line, includes theMexican States of Campeche, Yucatan and Quintana Roo. It had a population of4 million in 2000 and an annual birth rate of 2.2%, which is greater than the nationalaverage of 1.7%. Its coastal zone is a region which provides enormous natural,economic, and public health benefits. This region includes the watersheds, shores,estuaries, coastal lagoons, bays and the exclusive economic zone (EEZ), whereimportant economic activities take place such as oil exploitation, fisheries, portoperation and tourism, all of which create environmental pressures that threaten thevery resources that make the coast desirable. These pressures include wetland loss,changes in water circulation, increased nutrient load, and release of toxic chemicalsand pathogens.From the above, it is clear that water quality is a major issue when dealing with

problems of human health, eutrophication, harmful algal blooms, fish kills, seagrassloss, coral reef destruction, and even marine mammal and seabird mortality.Therefore, it is of major importance to recognize the spatial and temporal

variability of the water characteristics in coastal aquatic ecosystems as a key point toestablish indicators of water quality which may be used for its management [1]. Inmany cases, region specific features, rather than a single common general rule,should be considered.It should be noted that the hydrographic basin of the YP shows some particular

features such as a karstic type of soil which favors rainwater infiltration to theaquifer, and an important web of groundwater discharge in the coastal zone throughsprings and non-point sources amounting 9 millionm3yr�1 km of coast [2]. Theregion does not have any rivers and has little to no topographic elevation.These general features of the entire coastal zone of the YP contrast with the

differences observed on the kind and intensity of the anthropogenic impacts as thefollowing sites.Progreso has the highest coastal population, with 50,000 residents and a similar

amount occupying the beach houses during tourist season (July–August). It has themost important port of the region, moving 120 ton day�1; however, due theshallowness of the area (o5m), it was necessary to build an 8 km seaway to reach adepth of 5–6m. About 70% of this structure prevents the east–west water flowmodifying the hydrodynamics of the zone. Sisal is a fisherman-town of less than 5000inhabitants, with shrimp-farms, in an area of 480 ha and still growing. Celestun, isanother fisherman-town (5000 inhabitants), where both fish-trawling in shallowareas (o2m depth) and growing local tourism are important activities. Finally,Dzilam is another fishery-town (o3,000 inhabitants) characterized by great amountsof groundwater discharge through coastal springs, more than 100 of which have been

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J.A. Herrera-Silveira et al. / Ocean & Coastal Management 47 (2004) 625–639 627

recorded in 3 km2. All the sites do not have wastewater treatment; houses, touristfacilities and fishery industries generally have septic tanks.Therefore, we assume that the water quality is affected in different levels related to

the kind and intensity of the anthropogenic impacts. The purpose of this study is toidentify the spatial and temporal heterogeneity of water characteristics in the YPusing non-conventional instrumentation and data analysis, and to discuss the valueof reference water quality characteristics and indexes for monitoring programs andtheir utility for management strategies.

2. Material and methods

Samples were taken along four lines parallel to the coast, with a total of 12 stationson a 4 km2 sampled area at each locality (Fig. 1). They were covered bimonthly fromSeptember 1999 to August 2001. At each station in situ measurements oftemperature, salinity, and dissolved oxygen were made using a YSI 85 multi-parameter sound. Water samples were collected with a 2.5 l Van Dorn bottle fornutrient and chlorophyll-a (Chl-a) analyses following standard methods [3,4].In order to establish reference conditions for water quality, information of the

water characteristics should cover different temporal and spatial scales.

2.1. Single variables

Each variable was analyzed through a non-parametric variance analysis using boxand whisker diagrams in order to evaluate differences between sites. The mean is

Fig. 1. Map of the Yucatan Peninsula showing the sampling sites.

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represented by a triangle and median by the horizontal line into the box, 25th and75th percentiles are top and bottom of the box, while the 5th and 95th are located onthe tips of the whiskers. The median notch is the 95% confidence interval of theestimate. When notches between boxes do not overlap, the medians are considered tobe significantly different.

2.2. Combined variables

In order to provide means of exploring the multivariate nature of the data set, anordination analysis (principal components analysis—PCA) was done to identify thekey variables with the greatest influence in the hydrological behavior of each site.

2.3. Spatial and temporal variability

Spatial variability of the lagoon under different weather conditions was measuredwith an instrument system for high-speed mapping of temperature, salinity,chlorophyll-a and transparency called DataFlows.[5]. This instrument is adaptedfor flow-through sampling of the shallow coastal environment using a small boatwith a flexible intake and equipped with sensors interfaced with a data-logger toautomate the measurement of multiple variables in a spatial context throughintegrated GPS. The continuous trip in each run can be observed in the Fig. 2; morethan 2000 data points of each variable were recorded for each period.The collected data were analyzed to estimate the variability index (VI), which

produced an average percentage of change of each variable from nearest neighborfor each point in the transect.

VI ¼ 1�1� Zx; y

Zx � 1; y � 1

��

��;

where Z ¼ parameter, x ¼ lat., y ¼ long.

2.3.1. Trophic status

The sampling sites of the YP are enriched with nutrients from natural and culturaldischarges; therefore, for the evaluation of water quality it was necessary to use anindex of trophic status. In this case the nutrient eutrophication index applied was

TI ¼C

C � log xþ log A;

where TI is the nutrient eutrophication index, C is the log of the total loading of agiven nutrient in an area and x is the total concentration of this nutrient at certainstation. The values generated provide a continuous assessment of water quality andgive a value to the degree of eutrophication. The significance of the nutrienteutrophication index is that a TI is higher than 5 indicates eutrophic waters; formesotrophic waters the TI ranges from 5 to 3, and for oligotrophic waters the TI islower than 3 [20]. This dimensionless index was designed to be specific for each

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DZ0

2

4

6

8

10

12

pH

DZ7

8

9

20

25

30

35

20

24

28

32

36

40

(A) (B)

(C) (D)

Tem

pera

ture

, ˚C

Salin

ity, p

su

SiteSite

SiteSite

Dis

sol.

Oxy

gen,

mg/

l

PR SI CE CESIPR

DZ DZPR SI CE CESIPR

7.5

8.5

Fig. 2. Box and whiskers plots of temperature, salinity dissolved oxygen and pH, for each sampling site.


nutrient, with application to various types of water, sensitive to stressful effects ofeutrophication and simple for gathering data and for calculation.In order to establish seasonal variability, comparison of the hydrographical

variables between sites and seasons was done with the heterogeneity index [6], whichresults from the sum of the Euclidian distances of each station (12) of each site (4)from the PCA biplot.To get a first approach of site classification as a function of water quality, cluster

analysis was done with the significant variables provided by PCA. This analysis wasdone using data agglomeration techniques applied to calculation of the squares oftheir Euclidean distances.

3. Results

3.1. Single variables

Variance analysis showed significant differences (po0.05) among the study areaswith respect to salinity, dissolved oxygen, pH, nitrate, nitrite, silicate and Chl-a. Thelowest and highest water temperatures were observed in Dzilam (21–33.8 1C)(Fig. 2A). The median salinity was comparatively lower in Dzilam than in the other

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Table 1

Median, lower and upper quartile of water quality variables for each study area (n ¼ 850)

Dzilam Progreso Sisal Celestun EC CNAa

Temperature 27 26.3 26.4 26.5 NAb

1C 25–29 24–28.6 25–28.4 24.8–28

Salinity 36 38.3 37.4 37.6 NA

Psu 34–37 37–39 36–38 36–38

Dissol. Oxygen 5.3 5.2 5.7 5.7 5

Mg/l 4–6 4.5–6 5.5–6.5 5–6.5

PH 8.3 8.3 8.2 8.2 NA

8.1–8.3 8.2–8.4 8.1–8.3 8.1–8.3

Nitrate 5.2 1.2 4.8 1.7 0.6

mmol/l 3.2–9.4 0.5–2 3.2–7 0.5–3.2

Nitrite 0.51 0.79 1.01 0.49 0.04

mmol/l 0.2–0.9 0.5–1 0.5–1.5 0.2–0.9

Ammonium 4.2 5.2 4.5 5.2 0.55

mmol/l 3–6 4–6 1.2–7.7 3.7–8.7

Phosphate 0.62 0.46 0.51 0.46 0.02

mmol/l 0.3–0.9 0.2–0.7 0.3–0.8 0.3–0.7

Silicate 8.8 4.3 7.1 7.5 NA

mmol/l 6–13 3–6 4–11 5–11

Chl-a 1.14 1.7 3.2 2.5 NA

Mg/m3 0.8–2 1–3 1.6–6 1.4–5

aEC-CNA: Ecological Criteria, Comision Nacional del Agua.bNA: not applicable.


sites (Table 1). Nevertheless, in Sisal the lowest values (20.5 psu) (Fig. 2B) registeredcorresponding to the effluent of a shrimp farm.Dissolved oxygen shows hypoxic (o2mg/l) levels in Dzilam, Progreso and Sisal;

however, the median values (Table 1) indicate general conditions of a welloxygenated water column in all sites. The pH is less variable in Progreso and wassignificantly lower in Sisal (Fig. 2D).Ammonium was higher in Sisal and Progreso, with most values above 3 mmol/l

(Fig. 3A). In Sisal, concentrations above 80 mmol/l were observed near the dischargeof the shrimp farm effluents, while in Progreso high values (430 mmol/l) wereregistered during the periods of major human occupation of the summer houses.Nitrate was significantly high (Po0.05) in Dzilam and Sisal (Fig. 3B). The highest

concentrations in Dzilam (450 mmol/l) correspond to areas around the groundwaterdischarges, while in Sisal high concentrations were observed near the effluent of theshrimp farm (4100 mmol/l)Nitrite was significantly higher (Po0.05) in Sisal and Progreso (Fig. 3C),

following the same pattern as ammonium with respect to sources and time.Phosphate median was significantly different among sites (Fig. 3D),

however, relevant values (45 mmol/l) were observed in Sisal in the shrimp farmeffluent area.Silicate was significantly higher (Po0.05) in Dzilam and Sisal (6.61 mM) (Fig. 3E).

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0

20

40

60

80

100

0

20

40

60

80

100

120

0

2

4

6

8

10

DZ0

1

2

3

4

5

6

0

20

40

60

80

100

0

30

60

90

(A) (B) (C)

(D) (E) (F)Site Site Site

Am

mon

ium

, µm

ol/l

Phos

phat

e, µ

mol

/l

Silic

ate.

µm

ol/l

Nitr

ate,

µm

ol/l

Nitr

ate,

µm

ol/l

Chl

-a, m

g/m

3

CESIPR DZ CESIPR DZ CESIPR

150

120

Fig. 3. Box and whiskers plots of ammonium, nitrate, nitrite, phosphate, silicate and chlorophyll-a for

each sampling site.


Chlorophyll-a was significantly higher (po0.05) in Sisal and Celestun.Minimum values were observed in Dzilam (o0.5–1.5mg/m3) and maximum in Sisal(4120mg/m3) (Fig. 3F) near the shrimp farm effluent.

3.2. Combined variables

Principal component analysis of the hydrological variables showed that 60% ofthe total variance is in the first three components for all study zones (Table 2). InDzilam, salinity, silicate, nitrate and dissolved oxygen have a significant correlationwith the first two components, suggesting association with groundwater discharges.Ammonium and Chl-a are correlated with the third component related aquaticproduction.With respect to Progreso, PCA showed nitrite, phosphate and ammonium related

to Component I, likely from eutrophication processes. Salinity and dissolved oxygenare related to Component II, meaning groundwater discharges, as the thirdcomponent correlates with silicate.In Sisal, salinity, Chl-a and silicate have a significant correlation with the first

Component while the second one is correlated with nitrate, ammonium andphosphate, indicating that the shrimp farm effluent is an important source ofvariation to the hydrological pattern.In the case of Celestun, PCA showed salinity and nitrate correlated to Component

I (groundwater discharges) while silicate and Chl-a are correlated with ComponentII, suggesting aquatic production.

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12

DRY

Het

erog

enei

ty in

dex

CELESTUNSISALPROGRESODZILAM

NORTES

SEASON

RAINY11.4

11.5

11.6

11.7

11.8

11.9

Fig. 4. Comparison of spatial and temporal variability from date of the DataFlow system: Exempla with

fluorescence.

Table 2

Percentage of total explained variance and critical variables of the three first components in study area

Site Component Explained variance Critic variables

Dzilam I 32 Salinity, nitrite, silicate

II 17 Nitrate, dissolved oxygen

III 12 Chl-a, ammonium

Progreso I 25 Phosphate, nitrite, ammonium

II 20 Dissolved oxygen, salinity

III 15 Silicate

Sisal I 45 Salinity, Chl-a, silicate

II 13 Nitrate, ammonium, phosphate

III 12 Nitrite, pH

Celestun I 27 Salinity, nitrate

II 24 Chl-a, silicate

III 11 Dissolved oxygen, pH


3.3. Spatial and temporal variability

The high resolution of the spatial data collected with the DataFlow system can beused to estimate the variability of each zone and comparison among sites andseasons for each variable (Fig. 4) or for all variables (Table 3).The major variability of salinity and temperature was observed in Dzilam where

the groundwater springs are abundant and where mean depth is lowest (2.3m).The long-term variability of each site was determined after the annual trends of

the trophic index (Fig 5). Dzilam showed a uniform oligotrophic behavior while theother sites showed a tendency to increase their trophic status. Progreso and Celestunchanged from oligotrophic to lightly mesotrophic in three years, while in Sisal themajor changes were from mesotrophic to almost eutrophic.

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Table 3

Total and individual Variability Index the data from DataFlow system

Variable site Salinity Temperature Transparency Fluorescence Total

Dzilam 0.86 0.72 0.53 0.64 2.75

Progreso 0.75 0.68 0.73 0.76 2.92

Sisal 0.78 0.68 0.82 0.87 3.15

Celestun 0.72 0.63 0.66 0.71 2.72

0

1

2

3

4

5

6

DZILAM CELESTUN PROGRESO SISAL

Dis

imila

rity

Fig. 5. Values of Trophic Index for each sampling site.

0

1

2

3

4

5

6

TR

OP

HIC

IND

EX

Dzilam Progreso Sisal Celestun

Oligotrophic

Mesotrophic

Eutrophic199920002001

SITES

Fig. 6. Heterogeneity Index calculated by each sampling site.


3.4. Classification of sites

The heterogeneity index from hydrographic variables showed seasonal changes.During the Nortes (northern winds) season, Celestun had the greatest heterogeneity,followed by Dzilam, while in Sisal and Progreso high heterogeneity happenedduring the dry and rainy seasons, respectively (Fig 6). In accordance with theirhydrographic similarities there are two groups in the dendrogram (Fig. 7A,B and C,D):

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(1) Dzilam and Celestun and Progreso and Sisal, however, as seen in the distance value,the sites of the second group are more similar between them.

4. Discussion

The studied coastal aquatic ecosystems of Yucatan showed a high spatialvariability of their water characteristics at small (meters) (Fig. 4, Table 3) andmedium (km) (Figs. 2 and 3) scales. The same high spatial variability was observed atshort (seasonal) (Fig. 6) and medium (interannual) (Fig. 5) temporal scales. This is acommon characteristic in many coastal zones [7] because of the ecological gradientsestablished as a consequence of the land-ocean energy exchanges, mixing of freshand marine waters, and human disturbances. As a consequence, quality criteria andmonitoring of the water characteristics of these coastal aquatic ecosystems should bedone covering their spatial and temporal variability.

Fig. 7. Classification analysis of the sampling sites.

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Fig. 7. (Continued)


The data from this study were analyzed according to EPA [8] recommendationsshowing strong differences between sites (Table 1), which indicates that water qualitycharacteristics are strongly dependent on landscape features, particularly thoserelated to human activities. As a consequence, specific criteria may be required fordifferent sites to establish quality criteria and monitoring programs. Table 1 alsoshows that the official water quality criteria used in Mexico [9] are inappropriate,because they are applied in general to waters in the Gulf of Mexico, Caribbean andPacific Seas, which have very different hydrographic and biogeochemical character-istics. Accepting the application of those common criteria for such different seasimplies that human activities must have similar qualitative and quantitative impactsin all of them. As an example, all localities studied should be labeled as ‘‘poor’’ forsupport of aquatic life since the average nitrate concentration observed during thisstudy is higher than the official designated value (0.06 mmol/l). The same is valid fornitrite, phosphate and ammonium. Again, reference criteria should be reviewedaccording to specific site characteristics and the monitoring and comparative

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program should be extended to cover the range of spatial and temporal datavariability observed.This approach has additional advantages for implementing management actions.

Figs. 2 and 3 show that temperature variability was higher in Dzilam, which is thecoastal zone with the highest number of springs and the shallowest zone [10]. Salinityvariability was high in Dzilam, Sisal, and Progreso and reached relatively low valuesin these three zones related to spring groundwater discharges, shrimp farm effluents,and non-point groundwater discharges, respectively (12).Salinity in Dzilam and Sisal was more variable, and reached the lowest values, the

first related to the groundwater discharge and the second to the shrimp farm effluent,while Progreso showed the highest median value, suggesting input from groundwaterseepage [11]The wide range of variation of dissolved oxygen indicates intense metabolic

activity in the water column; nevertheless, the hypoxic values observed in Dzilam,Progreso and Sisal suggest that they may be more vulnerable to increasing loading ofdissolved nutrients and organic matter [12].Ammonium, nitrite and phosphate were good indicators of anthropogenic

impacts. In Progreso the loading of nutrients comes from seepages [10,11] and arehigher during the summer season, which is the time with the major humanoccupation of the coast by local tourism. The highest concentrations of nutrients andChl-a in Sisal are related with the shrimp farm and harbor effluents. In Celestun,trawling fishing in shallow (o2m) areas induce water-sediment processes favoringhigh ammonium and Chl-a levels. Phytoplankton is dominated by benthicdiatoms. [13], suggesting resuspension as an important agent to the biogeochemistryof this site.Nitrate and silicate were higher in Dzilam and Sisal, the former from groundwater

discharges recognized as nitrate and silicate source [14], the latter from the shrimpfarm and harbor effluents. Shrimp ponds are fertilized with nitrates and silica tofavor the growth of diatoms, while in the harbor two springs fertilize the coastalarea.As part of a major project, phytoplankton and submerged aquatic

vegetation (SAV) have been recorded in some sites in order to incorporate biologicalindicators of water quality. As for phytoplankton, Progreso is dominated bydinoflagellates and has been reported harmful species as Dinophysis caudata,

Gymnodinium sanguıneum, Gambierdiscus toxicus, Prorocentrum mexicanum, Pro-

rocentrum mınimum, Heterocapsa circularisquama, Prorocentrum lima, and Pyrodi-

nium bahamense v. compressum, while in Dzilam diatoms dominate the community[10,13], this algal dominance changes is recognized as a primary symptom ofeutrophication [15].With respect to SAV, Dzilam is the site with highest coverage of seagrasses, with

Progreso and Sisal being the lowest. These two sites have been experiencing loss ofSAV and substitution of seagrasses by macroalgae [16]; these changes are recognizedas secondary symptoms of eutrophication [15]. In Celestun, trawling fishing’smechanical damage to SAV and increases water turbidity, both of which havenegative impacts to SAV growth.

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Incorporation of water quality biological indicators in a coastal zone managementprogram may seem expensive and time-consuming; however, their utility in evaluatethe consequences of eutrophication, chemical pollution, and impacts to humanhealth [17,18], as well as to evaluate the successes of the management strategies cannot be questioned.The analysis of each variable is the first step to determine the water quality of the

coastal zone; however, to optimize the value of this information in costal zonemanagement, it is necessary the repeat measurements over time and space and toconduct integral analysis in order to learn patterns and trends of water quality.Multivariate statistical techniques and indexes can be useful in order to capture thevariance of the original dataset and extract general patterns.In Dzilam, PCA results (Table 2) indicate that groundwater discharges and

resuspension are the most important process as to control water quality patterns.Spatial variability is also related to groundwater discharge and their generalcharacteristics, including the human activities, result in a oligotrophic condition withrespect to the other sites, suggesting that conservation strategies should be includedin a management coastal zone program of this area.In Progreso, the critical variables (Table 2) suggest that domestic sewage seepage

and changes in water movement by the harbor are the major factor affecting waterquality; its spatial variability and trophic status are reflected in phytoplankton andSAV communities. Therefore, a sewage treatment plant and improvement of theharbor water circulation should be the first step in a management strategy.In Sisal, it is clear that the shrimp farm effluent is responsible for the spatial

variability and temporal trophic changes, showing that mariculture is an activity thatmust be strictly regulated by local legislation. A new water pond management mustbe developed considering the wetlands use as waste treatment [19].In Celestun, critical variables, spatial variability and trophic status show a healthy

water body classified in the same group of Dzilam. However, some managementstrategies should be implemented to stop trawling fishing in shallow areas (o2m),improve the septic tanks systems in the tourist infrastructure, and promote the watercirculation in the fisherman port.It can be concluded that eutrophication is a major concern of the Yucatan

Peninsula coastal zone, and in accordance with the present economic development(e.g., ports, tourism) of the region, its impact on the water quality, biologicalintegrity, and human health could be enormous and could negatively affect anymanagement program.In conclusion, it is recommended that sustainable coastal zone management

include an efficient water quality program for each area or zone (reference values),incorporating measurements (physical, chemical and biological) of a group ofenvironmental variables in a space–time context. These measurements should beanalyzed following approaches to integrate the collected data (e.g., throughmultivariate statistics and indexes) in order to develop the capacity to determinelocalization and intensity of the problems and trends of management actions. Waterquality should be used as a reference point for the coastal zone managementprocedure.

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Acknowledgments

We thank the staff of the Primary Production Laboratory of CINVESTAV-IPNUnidad Merida, in special to J. Ramirez, A. Zaldivar, C. Alvarez, M. Aguayo,J. Trejo, C. Vallejo, I. Medina, M. Reyes and Z. Chi. This work was supported byCONACYT-32356-T and CONACYT G-34709-T.

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coastalwaterqualityassessmentintheyucatan peninsula...

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