Invasive mollusks Tarebia granifera Lamarck, 1822 and Corbicula fluminea Müller, 1774 in the Tuxpam and Tecolutla rivers, Mexico: spatial and seasonal distribution patternsAquatic Invasions (2009) Volume 4, Issue 3: 435-450 DOI 10.3391/ai.2009.4.3.2 © 2009 The Author(s) Journal compilation © 2009 REABIC (http://www.reabic.net) This is an Open Access article
435
Research article
Invasive mollusks Tarebia granifera Lamarck, 1822 and Corbicula fluminea Müller, 1774 in the Tuxpam and Tecolutla rivers, Mexico: spatial and seasonal distribution patterns
Eugenia López-López1*, J. Elías Sedeño-Díaz2, Perla Tapia Vega1 and Eloiza Oliveros1 1Laboratorio de Ictiología y Limnología, Escuela Nacional de Ciencias Biológicas. IPN. Prol. de Carpio y Plan de Ayala, Col. Sto. Tomás, 11340, México D.F. 2Coordinación del Programa Ambiental.IPN Edificio CFIE, Planta Baja, Av. Wilfrido Massieu esq. Av. Luis Enrique Erro, Unidad Profesional Adolfo López Mateos, Col. Zacatenco, 07738, México D.F. E-mail: eulopez@ipn.mx (ELL), jsedeno@ipn.mx (JESD) *Corresponding author
Received 16 April 2009; accepted in revised form 24 July 2009; published online 13 August 2009
Abstract
The Tuxpam and Tecolutla rivers in the Gulf of Mexico, are located in the Mesoamerican biodiversity hotspot and support different human activities: crude oil extraction, agriculture and livestock, that provoke environmental disturbances. Aquatic mollusks, physicochemical water characteristics and substrate type were examined along the main watercourse of these rivers during three periods of one year: the wet season, dry season, and during the northern winds season, when hurricanes are more frequent. In both rivers, physicochemical water characteristics, types of substratum and mollusk fauna demonstrated environmental gradients and differentiate two river zones: freshwater and estuarine. Differences were also found between the dry season, with higher inorganic salts content, and the wet and northern winds and hurricane seasons, when inorganic and organic nutrient inputs occurred. The mollusk fauna is composed of nine and eleven taxa in the Tecolutla and Tuxpam rivers, respectively. In both rivers, the introduced gastropod Tarebia granifera is the dominant species in the freshwater zone with regard to population density and the area it covers within the ecosystem, followed by the introduced bivalve Corbicula fluminea. Native mollusk species were confined to point-locations and attained very low densities. The gastropod Neritina virginea and the bivalve Brachidontes exustus were dominant in the estuarine zone of both rivers. Mollusk population densities declined during the wet, northern winds and hurricane seasons, while in the dry season both alien species reached higher densities, which could indicate that alien mollusks are removed by effect of climatic events. T. granifera and C. fluminea exhibit traits characteristic of invasive species and pose a risk to native mollusk biodiversity in these rivers.
Key words: invasive aquatic mollusks, tropical Mexican rivers, environmental degradation, biodiversity loss
Introduction
The Mexican rivers Tecolutla and Tuxpam drain into the Gulf of Mexico within the Meso- american biodiversity hotspot (Myers et al. 2000). Throughout much of the Mexican Gulf coast region human activities such as crude oil extraction, intensive agriculture, water extraction and inputs of untreated wastewater have degraded various aquatic ecosystems (Ortíz- Lozano et al. 2005). Lake (2000), states that several environmental disturbances have a negative impact on native species, through eradication or removal of sensitive species, and can create spaces available for colonization.
Other human activities including aquaculture, recreation, transport, and trade globalization intentionally or accidentally also contribute to the spread of invasive aquatic species (Cohen and Carlton 1998; Carlton and Geller 1993) that can use such available spaces. Invasive species are considered the second major cause of bio- diversity loss in the world (Vitousek et al. 1996; Leung et al. 2002) and their spread is one of the major problems in ecosystem conservation (Ruiz et al. 2000). Adverse effects of invasive species may take different forms: once they have achieved a wide distribution, these species produce global homogenization of the patterns of distribution, altering the once distinctive
E . López -López e t a l .
436
regional biota, and they may affect aquatic ecosystems through competitive exclusion of indigenous biota (Rahel 2000; Sousa et al. 2008). Some invasive species displace native species through direct competition, predation, intro- duction of diseases, changes in biological and geochemical cycles, and alteration of the trophic web, thus causing adverse effects in the invaded habitats (Davis et al. 2000; Mack and Lonsdale 2001; Sax et al. 2002).
In Mexico, the National System on Invasive Species established by the National Commission for the Understanding and Use of Biodiversity (CONABIO 2008) has preliminarily identified at least 1000 invasive species of plants, mollusks, crustaceans, insects, fishes, amphibians, reptiles, birds and mammals. These include 13 species of invading mollusks: 11 bivalves (four freshwater) and two gastropods (one freshwater). CONABIO (2008) states that these species affect the natural wealth of Mexico, deteriorate environmental conditions in ecosystems and may have negative consequences on human health, production and the economy and recognizes the urgent need for additional knowledge of the distribution of these species and their impact on native biota, and the need to identify high-risk biodiversity areas.
Mexico has been ranked as one of the five megadiversity countries in the world (Bezaury et al. 2000), however, knowledge of the diversity of certain groups within its territory is limited because large areas remain unstudied, especially in the case of freshwater mollusks (Naranjo 2003). Based on worldwide diversity estimates, Strong et al. (2008) recognize Mollusca with as many as 80,000-100,000 described species, as an extraordinarily diverse phylum, second in diversity only to arthropods. In Mexico, 16 families of freshwater mollusks have been recorded, representing five orders, four subclasses (Naranjo 2003) and 211 species (Contreras-Arquieta 2000). Furthermore, in a study of the continental gastropods of Mexico and Central America, Thompson (2008) found 168 aquatic operculate and 84 aquatic pulmonate species and emphasized that the mollusk fauna of Mexico is poorly studied. Thus, the number of continental mollusk species may exceed current records, particularly since two zoogeographic regions, Nearctic and Neotropical, each with its own characteristic fauna, converge in Mexican territory sharing a broad transition zone (Morrone and Márquez 2001). To the paucity of knowledge on the native freshwater mollusks of Mexico must be added the lack of information on
the distribution of species catalogued as invasive by CONABIO (2008). It is therefore essential for studies to focus on the impact of invasive species on the native biota and invaded habitats. This paper contributes to the understanding of patterns of distribution of native and introduced mollusk species in the Tuxpam and Tecolutla rivers, in the Mexican subtropics. The different forms taken by the invasion of two alien species in each of these rivers are explained and the risks these species pose are evaluated.
Study area
Tuxpam and Tecolutla rivers cross the Gulf of Mexico coastal plain in the northern part of the state of Veracruz (Figure 1). Both are perennial rivers with high discharges arising in the Eastern Sierra Madre (more specifically the Sierra Norte de Puebla) and flowing through a region of hot humid and sub-humid climate with abundant rainfall throughout the year, particularly in summer. Discharges of both rivers are affected by the impact of northern winds and hurricanes.
The Tecolutla drainage includes the major tributaries Necaxa, Tenango, Laxaxalpan, Zem- poala, Apulco and Chichicatzapa rivers within its total drainage area of 7,903 km2 to discharge a mean of 6,885 million m3, into the Gulf of Mexico at Barra de Tecolutla (CONAGUA 2007). The mean air annual temperature is 21- 26°C, total annual rainfall ranges from 1,200 to over 4,000 mm, and the rate of evaporation is 1,064-1,420 mm (Sanchez and De la Lanza 1996). The vegetation cover is semi-deciduous tropical forest, mangrove, halophytic vegetation and palm grove (Arriaga et al. 2002). Tecolutla River is listed by CONABIO (Arriaga et al. 2002) as a priority hydrologic region since it flows through an area of high biodiversity, and is catalogued as threatened because it supports diverse land uses (agriculture, livestock, fishing and tourism).
Tuxpam River watershed covers a surface area of 5,899 km2 and has a mean annual flow of 2,580 million m3 (CONAGUA 2007). Its princi- pal headwater known as Río Pantepec is joined by several tributaries before reaching the coastal plain named Tuxpam to discharge into the Gulf of Mexico at Barra de Tuxpam. Human activities in this basin include livestock, agriculture, fishing and industry. There is a power plant in Barra de Tuxpan, and a shipyard and the seaport of Tuxpam are located near the river’s mouth.
I nvas ive mo l lu sks i n r i ve r s o f t he Gu l f o f Mex ico
437
Figure 1. Location of study sites in the Tecolutla and Tuxpam rivers. Tx followed by a number indicates the number of the study site in the Tuxpam river. Tc followed by a number indicates the number of the study site in the Tecolutla river. Geographic coordinates are in Annex 1
Material and Methods
A total of 11 sites in the Tuxpam River (Tx) and nine in the Tecolutla River (Tc) were surveyed (Figure 1, Annex 1). Collection of aquatic mollusks was made during three different periods of the year: the wet season (August 2007 in Tc, September 2007 in Tx), the northern winds and hurricane season (December 2007 in Tc, January 2008 in Tx) and the dry season (March 2008 in Tc, April 2008 in Tx). Surveys covered the main water-courses of the basins including their upper, middle and lower reaches. Different collection methods were used depending on stream bed characteristics and presence/absence of aquatic vegetation (Wetzel and Likens 2000): collection
within 1-m2 quadrats, sieving of sediments, 1 m2- base Surber net, and collection among roots, stems and foliage in areas of the banks with aquatic vegetation. Specimens were fixed in 70% ethanol.
Environmental parameters were measured in situ at all study sites using a Quanta multi- parametric sonde: water temperature (°C), turbidity (NTU), salinity (PSU) dissolved oxygen (mg/L) and pH. A General Oceanic flow meter was used to record current velocity (m/sec) in transects across the sampled area, while altitude (masl) and geographic coordinates were determined with a Sport Trak Magellan GPS.
Two 500-mL samples of water from each site were transported in acid washed glass containers
E . López -López e t a l .
438
at 4°C to the laboratory in order to evaluate water quality parameters. Two sediment samples from each site were collected in 1000-mL flasks for subsequent sediment and organic matter analyses and for specimen collection.
Water samples were processed with a HACH DRL2500 spectrophotometer to determine total nitrogen (NT mg/L), nitrite (NO2 mg/L), nitrate (NO3 mg/L), ammonia (NH3 mg/L), sulfate (SO4 mg/L), orthophosphate (PO4 mg/L), total phosphorus (PT mg/L), color (Pt-Co units), hardness (CaCO3 mg/L), total suspended solids (TSS mg/L) and total dissolved solids (TDS g/L). APHA (1985) procedures were used to measure alkalinity (CaCO3 mg/L), chloride (Cl mg/L), biochemical oxygen demand (BOD5) and total and fecal coliforms (MPN/100 mL).
Sediment samples were dried at 60°C for 24 h and processed for analysis according to EPA (1986) procedures. The mesh size (mm) of sieves was: 4.76, 3.36, 2.38, 2, 1.68, 1.41, 0.841, 0.5, 0.42, 0.297, 0.25, 0.21, 0.177, 0.149 and 0.106. The variable φ (-Ln2 of the diameter of particle) was plotted against the cumulative weight of materials retained in each sieve in order to obtain the mean particle size and percentages of each soil texture according to the Wentworth scale. Organic matter was quantified using the Walkey and Black method (NOM-021-RECNAT 2000).
Separate sediment samples for specimen collection were sieved and examined with a Zeiss stereoscopic microscope. The specimens obtained were separated and fixed in 70% ethanol.
Importance value index (IVI) was determined according to Krebs (1989) for the whole river, taking into account the frequency of occurrence (proportion of times that a species occurs in all the samples taken) and relative abundances (proportion of specimens for each species in the total specimens collected) of all mollusk species for each river: IVI= %FO + relative Ab, where: %FO = Percent frequency of occurrence and relative Ab = Relative abundance.
Zones and environmental gradients along each river were visualized and characterized by principal component analysis (PCA) using a correlation matrix of the log transformed (x+1) values of physicochemical factors, water quality parameters, organic matter and mean sediment particle size at each of the sites during the three study seasons. Canonical correspondence analysis (CCA) was used to examine the correlation of mollusk species with habitat
conditions in each river, using a correlation matrix of the log (x+1) transformed values of in situ recorded factors, water quality, sediment analysis and organic matter, and a second matrix with the relative abundance of each mollusk species, transforming values to square roots. Statistical analyses were performed with XL- STAT v. 2008 software (XL-STAT 2008).
Results
Tecolutla River
PCA revealed an environmental gradient with spatial and seasonal variations. The ordination biplot (Figure 2) shows the first two axes which together accounted for 51.43% of the total variance (PC1: 34.21% and PC2: 17.22%). Three clusters of sites corresponding to each of the study seasons are apparent. In August (wet season) there are high levels of total coliforms, nutrients (nitrate, nitrite, orthophosphate, PT), suspended solids and turbidity. No marked spatial variations occurred in this month, but at sites Tc9 and Tc8 the highest content of coliforms and nutrients was recorded, while sites Tc1 to Tc6, located at higher altitudes above sea level, showed higher levels of orthophosphate, PT and turbidity. In December (the cold, northern winds season), there was a wider scatter of sites expressed as spatial variation in the biplot (Figure 2), as a result of the higher variation of measured parameters. Tc8 and Tc9, influenced by sea water, were highest in salinity, total dissolved solids, chloride and sulfate. Tc1 to Tc7, on the other hand, were characterized by higher flow velocity, pH, NT, color, and organic matter content as well as larger particle size. In March (dry season), the highest levels of hardness, alkalinity, BOD5, ammonia and dissolved oxygen were recorded. Spatial variations occurred in this season. Tc9 was found to be the most different site due to high salinity, total dissolved solids, sulfate and chloride, while at site Tc8, the highest content of ammonia was recorded. PCA differentiated the marine influence (estuarine zone Tc8 and Tc9 in December and March, Tc9 in August) from the freshwater zone (Tc1 to Tc7), and revealed the seasonal effect of torrential rains when the salinity was lower and almost all the river showed environmental homogeneity.
I nvas ive mo l lu sks i n r i ve r s o f t he Gu l f o f Mex ico
439
Figure 2. PCA biplot of Tecolutla River. Vectors represent environmental factors. Codes as in Annex 2. Numbers after Tc= indicate the number of study site and letters after number indicate month of study (Mar= March, Dec= December, Au= August)
Figure 3. PCA biplot of Tuxpam River. Vectors represent environmental factors. Codes as in Annex 2. Numbers after Tx= indicate the number of study site and letters after number indicate month of study (Apr= April, Jan= January, Sep= September)
E . López -López e t a l .
440
Tuxpam River
The first two PCA components accounted for 44.27% of the total variance (PC1: 27.43% and PC2: 16.84%). The biplot of these components (Figure 3) show the position of sites arrayed as environmental gradients. Tx8 to Tx11 in January and April and Tx11 in September were characte- rized by the highest levels of salinity, chloride, sulfate and total dissolved solids, making evident the reach with marine influence. In January (the cold, northern winds season), the upper reaches (Tx1 to Tx7) showed the highest flow velocity, alkalinity, dissolved oxygen and total coliforms values. In April (dry season), Tx1 to Tx6 were high in total coliforms and organic matter content, and Tx7 in BOD5, hardness, color, turbidity, NT and PT. In September (wet season), environmental conditions were uniform through- out the river. This season was characterized by peak of water temperatures and high nutrient (nitrite, nitrate, orthophosphate) and organic matter content. Only one site (Tx11) differed from the rest of the studied localities due to its marine influence (chloride, salinity, total dissolved solids), as well as the high levels of ammonia and NT. According to the results of PCA (Figure 3), the estuarine (Tx8 to Tx11) and freshwater (Tx1 to Tx7) zones were differentiated, as well as the seasonal dynamic of the system.
Mollusk species and patterns of distribution
Nine mollusk species were collected in the Tecolutla and 11 in the Tuxpam basins (Table 1). Three alien species occurred in both rivers: two gastropods (Tarebia granifera and Melanoides tuberculata) and one bivalve (Corbicula fluminea). The species collected showed marked differences in their pattern of distribution along the rivers.
Distribution of species in Tecolutla and Tuxpam rivers are shown in Table 2. In Tecolutla River, T. granifera and C. fluminea were widely distributed in the freshwater zone, from Tc1-8. M. tuberculata was found only in the upper reaches from Tc1-3. Haitia mexicana is present at Tc4 and Tc5. Brachidontes exustus and Neritina virginea are restricted to the lower reaches near the river mouth (Tc8). Species with a more limited distribution were Pomacea flagellata, in the upper reaches at Tc1, and Succinea sp. and Biomphalaria sp. in the upper
Table 1. List of aquatic mollusk species in Tecolutla (Tc) and Tuxpam (Tx) rivers (n-native, a-alien)
Aquatic mollusk species Status Tc Tx
Class Gastropoda Family Neritidae Neritina virginea Linnaeus, 1758 n x x Family Ellobiidae Melampus coffeus Linnaeus, 1758 n x Family Ampullaridae Pomacea flagellata (Say, 1827) n x x Family Thiaridae Melanoides tuberculatas (O.F.Müller, 1774) a x x
Tarebia granifera Lamarck, 1822 a x x Family Physidae Haitia mexicana (Philippi, 1841) n x x Family Ancylidae Hebetancylus excentricus (Morelet, 1851) n x
Family Planorbidae Biomphalaria sp. n x Micromenetus dilatatus Gould, 1841 n x
Family Succineidae Succinea sp. Drapanaurd, 1801 n x Class Bivalvia Family Ostreidae Ostrea palmula Carpenter, 1857 n x Family Mytilidae Brachidontes exustus (Linnaeus, 1758) n x x
Family Corbiculidae Corbicula fluminea (O.F. Müller, 1774) a x x
Total 9 11
reaches at Tc2. In the Tuxpam River T. granifera was the most widely distributed species in the freshwater zone, Tx1-6. C. fluminea was found at Tx2, Tx6 and Tx7. M. tuberculata occurred at Tx1-4 and Tx6. H. mexicana was present in the upper and middle reaches, Tx1-3, Tx5 and Tx6. N. virginea was found in the lower reaches only (Tx7-9). B. exustus occurred only at Tx9. Species with very limited distribution included P. flagellata (Tx3 only), Hebetancylus excentricus (Tx5 and Tx6), and Micromenetus dilatatus (Tx5 and Tx7). Melampus coffeus is known only from Tx9 and Ostrea palmula only Tx11 (Table 2).
I nvas ive mo l lu sks i n r i ve r s o f t he Gu l f o f Mex ico
441
Table 2. Records of mollusks species at study sites of Tecolutla (Tc) and Tuxpam (Tx) rivers during study period (for locations of study sites see Figure 1 and Annex 1)
Study sites
Ta re
bi a
gr an
ife ra
C or
bi cu
O st
re a
pa lm
ul a
Tc1 X X X X Tc2 X X X X X Tc3 X X X Tc4 X X X Tc5 X X X Tc6 X X Tc7 X X Tc8 X X Tc9 X X Tx1 X X X Tx2 X X X Tx3 X X X X Tx4 X X Tx5 X X X X Tx6 X X X X X Tx7 X X X Tx8 X Tx9 X X X Tx10 Tx11 X
Mollusk species showed marked variations in densities and dominance. In the Tecolutla River, T. granifera attained mean densities > 100 indivuals/m2. The species C. fluminea, N. virgi- nea, Haitia mexicana and Melanoides tubercu- lata had mean densities ranging from 1 to 100 individuals/m2. Brachidontes exustus, P. flage- llata, Succinea sp. and Biomphalaria sp. all had mean densities ≤1 individual/m2 (Figure 4). In the Tuxpam River, T. granifera and Brachi- dontes exustus reached mean densities of 100 to 1,000 individuals/m2. N. virginea, H. mexicana, C. fluminea, Micromenetus dilatatus and Melanoides tuberculata had mean densities of 10-100 individuals/m2 while mean values for Hebetancylus excentricus and P. flagellata ranged from 1 to 10 individuals/m2. Melampus coffeus and O. palmula had the lowest mean densities, with ≤ 1 individual/m2 (Figure 4).
Very marked spatial and seasonal variations occurred in mean densities of mollusk species. In the Tecolutla River, the lowest densities occurred in December and the highest in March (Figure 5a). In the freshwater zone, Tc5 and Tc7 had the highest densities in all three study seasons. Seasonal density changes produced a
Figure 4. Mean density of mollusk species in Tecolutla and Tuxpam rivers. The bar represents SD
shift in the species with the highest population densities in the upper reaches (Tc1 to Tc3): C. fluminea had the maximum values in August and March and Melanoides tuberculata in December (Figure 5b). In the middle reaches, in spite of seasonal variations, the species with the
E . López -López e t a l .
442
Figure 5. Absolute and relative density of the aquatic mollusk species in Tecolutla River
Figure 6. Absolute and relative density of the aquatic mollusk species in Tuxpam River
I nvas ive mo l lu sks i n r i ve r s o f t he Gu l f o f Mex ico
443
highest densities was T. granifera, while in the lower reaches N. virginea had the highest densities in all three seasons (Figure 5b).
In the Tuxpam River, the lowest densities occurred in January (Figure 6a) while peak values were attained in April. In the freshwater zone, Tx3 to Tx6 showed the highest densities. In spite of seasonal variations in population densities, there was no change in the higher ratios at which T. granifera was present in the freshwater zone and the species N. virginea and B. exustus in the estuarine zone (Figure 6b).
Importance value indicates that T. granifera is the dominant species in both rivers, with index values of 128 and 96 in the Tecolutla and Tuxpam rivers, respectively (Figures 7a and 7b). In the Tecolutla River, T. granifera, C. fluminea and M. tuberculata (all three non-native species), account for a cumulative index value of 179 out of a possible 200. Importance values below 7 were obtained for all other mollusk in this river (Figure 7a). In the Tuxpam River, T. granifera, two brackish species (N. virginea, B. exustus) and two freshwater species (C. fluminea, Haitia mexicana) have index values ranging from 10 to 26. Species with IVI< 10 include Micromenetus dilatatus, P. flagellata, Hebetancylus excentri- cus, Melanoides tuberculata and Melampus coffeus (Figure 7b).
Figure 7. Importance value index of mollusks a) Tecolutla River and b) Tuxpam River
Relation of environmental parameters, substratum characteristics and mollusk species
The first two components in the CCA of the Tecolutla River account for 81.30% of the explained variance (Axis 1: 64.93% and Axis 2: 16.37%). The biplots show the relations of mollusk species and sites, as well as water quality conditions and type of substratum. Three groups of species can be seen in the biplot in Figure 8a. The smallest one is formed by N. virginea and B. exustus, which reached their highest densities at Tc9 in December and March. Similarly, Figure 8b shows these species are closely correlated with high salinity, total dissolved solids, chloride, sulfate and hardness. In the upper left quadrant are T. granifera, Haitia mexicana and C. fluminea, which attained maximum densities in Tc4, Tc5, Tc6 to Tc7 in March and in Tc3 and Tc7 in August. In both seasons, these sites had the highest levels of coliforms, nitrite, nitrate, ammonia, BOD5, color, alkalinity, current velocity and water tempera- ture, with fine and very fine sandy substrata. On the right side of the biplot are P. flagellata, which is closely correlated with Tc1 in March, a site in the upper reaches with a substratum of gravel and very coarse sand; Melanoides tuberculata, related with Tc1 and Tc2 in August and with fine gravel and very fine sandy substrata; and Biomphalaria sp. and Succinea sp., occurring at Tc2 in March and related with fine gravel and coarse sandy substrata; seasons and conditions that are exactly opposite those of the first group of species. CCA showed species assemblages, their divergent patterns of distribution and most importantly their relation with habitat conditions.
In the CCA of Tuxpam River, the first two components accounted for 75.89% of the explained variance (Axis 1: 55.37% and Axis 2: 20.53%). Biplots show the species separated into two groups. The group on the right side includes B. exustus, Micromenetus dilatatus, Melampus coffeus and N. virginea. These species were present at Tc7, Tc8, Tc9, Tc10 and Tc11 in all study seasons (Figure 9a) and are related with high levels of total dissolved solids, salinity, chloride, ammonia, sulfate, NT, PT and BOD5, and very fine sandy and coarse to very fine silty substrata (Figure 9b). On the left side of the biplot are T. granifera, C. fluminea, Hebetancy- lus excentricus, Haitia mexicana, P. flagellata
E . López -López e t a l .
444
and Melanoides tuberculata. These species are distributed in the freshwater zone (Tx1-6) with high levels of nitrite, nitrate, orthophosphate, alkalinity, pH, turbidity, water temperature and coliforms, and also at higher altitudes where the substratum is predominantly coarser materials
such as pebbles, gravel and coarse to fine sand (Figures 9a and 9b). CCA identified two groups of mollusks with entirely different distributions as well as the relation of each group with contrasting environmental conditions and substrata.
Figure 8. Biplot of CCA of Tecolutla River. a) study sites and species and b) factors and species. Numbers after Tc indicate the number of study site, letters after number indicate month of study (Mar= March, Dec= December, Au= August). See Annex 2 for the code of abbreviations of environmental factors and species
I nvas ive mo l lu sks i n r i ve r s o f t he Gu l f o f Mex ico
445
Figure 9. Biplot of CCA of Tuxpam River. a) study sites and species and b) factors and species. Numbers after Tx indicate the number of study site, letters after number indicate month of study (Apr= April, Jan= January, Sep= September). See Annex 2 for the code of abbreviations of environmental factors and species
Discussion
Water quality characteristics indicate that the Tuxpam and Tecolutla rivers receive inputs of organic matter, nutrients (orthophosphate, nitrogenous compounds) and coliform bacteria. Both rivers are located in a region with several environmental disturbances by human activities
(Ortíz-Lozano et al. 2005), which contribute to the inputs of diverse compounds originating in wastewater discharges, leaching materials and basin runoff. Despite the nutrient and organic matter enrichment found by this study, the water of these rivers has been rated good and excellent by the CONAGUA (2007) monitoring network. This agency, however, uses only three parameters (BOD5, Chemical oxygen demand and total suspended solids) to rate water quality.
E . López -López e t a l .
446
Our results, on the other hand, indicate both rivers sustain nutrient enrichment, although they are less degraded than the Coatzacoalcos and Pánuco rivers which are also located in the Gulf of Mexico coast area (CONAGUA 2007).
The Tuxpam and Tecolutla rivers show important differences in the estuarine zone due to their morphology, freshwater discharges and seasonal variations. Mean annual flow is 2,580 million m3 in the former and 6,885 million m3 in the latter (CONAGUA 2007). As a result of these differences in stream flow, the estuarine zone is larger in the Tuxpam River than in the Tecolutla River. In our study PCA allowed identification of environmental gradients along each river that are associated with changes in altitude, flow velocity, dissolved solids, organic matter, nutrients and salinity, that differentiate two zones: freshwater and estuarine. The rivers undergo seasonal variations: during the dry season, peak levels of alkalinity and BOD5 occurred and sea front influence produced a marked increase in salinity in the estuarine zone. During the wet and the northerly wind seasons, and favored by the effect of hurricanes, both rivers showed a tendency to environmental homogeneity. Higher levels of nutrients (nitrate, nitrite, orthophosphate, PT) were present and the estuarine zone decreased in extent. Turbidity rose while salinity fell markedly. Studies showing the effect of seasonal rainfall and drought in watercourses in intertropical areas are scarce. Brodie and Mitchell (2005) found higher nutrient loads during rain episodes and in correlation with land use for agriculture in tropical river basins in Australia. Agriculture is a major land use in the Tuxpam and Tecolutla basins and, along with discharges from small human settlements near the river, may explain nutrient inputs, particularly during the wet season.
Mathooko and Mavuti (1992) state that hurricanes and rainy seasons not only alter the volume of stream flow, they also bring sediment loads and increase benthic organisms drift, which affect their population densities. In our study in both rivers density values were depleted during the months of rainy, northern winds and hurricanes seasons as opposed to the dry season when densities rose.
Aquatic mollusks of the Tuxpam and Tecolutla rivers showed strong dominance of two exotic species: T. granifera and C. fluminea. Only at one of nine Tecolutla study sites (Tc9) and in four of 11 Tuxpam study sites (Tx8 to
Tx11) were both absent. The only areas not colonized by these alien species were the estuarine zones of the rivers, where N. virginea and B. exustus were dominant. In both freshwater courses these alien species reached higher densities than others. Melanoides tuberculata, another non-native species, had a limited distribution in both rivers as well as lower densities than others.
Contreras-Arquieta (2000), Naranjo (2003) and Thompson (2008) state that knowledge of aquatic mollusks is in an initial stage in Mexico. In the Tuxpam and Tecolutla rivers there are no historical records of the native aquatic mollusks. The number of mollusk species found in our study in both rivers is low, compared to numbers in more extensively studied areas of Mexico, such as Cuatro Ciénegas, Coahuila with 13 species; (Contreras-Arquieta 1998) and El Edén, Quintana Roo with 11 species (Cózatl-Manzano and Naranjo-García 2007). Several authors (Davis et al. 2000; Mack and Lonsdale 2001; Sax et al. 2002; Sousa et al. 2008), mention that introduced species are able to displace native species through different mechanisms, including competitive exclusion, introduction of disease and even habitat change. In the case of the Tuxpam and Tecolutla rivers the absence of historical malacological fauna records prevents comparison of the native mollusk assemblages before and after the introduction of alien species.
The gastropod T. granifera is native to India, Southeast Asia, the Philippines, Japan and Hawaii (Abbot 1952). Its introduction to the United States has been documented by Karatayev et al. (2007), who point out that the aquarium trade recognizes its presence in Texas since 1935. In our study, the wide distribution of this species in the Tuxpam and Tecolutla rivers shows it has been able to establish and is very successful in freshwater zones of both rivers, although the date of its introduction remains unknown. In this respect, only Naranjo and Olivera-Carrasco (2007) record its occurrence in Lake Catemaco, Veracruz, in the south of the Gulf of Mexico. Karatayev et al. (2007) report that this species tolerates a wide range of temperatures (10 to 38°C). Water temperatures in the Tuxpam and Tecolutla rivers (18°C min to 30°C max) are well within this range.
Pointier and Jourdane (2000) stress the damage T. granifera has caused, including probable irreversible eradication of several native mollusks in Cuba (Pachychilus violaceus and various species of the genus Biomphalaria),
I nvas ive mo l lu sks i n r i ve r s o f t he Gu l f o f Mex ico
447
and endangerment of others (Hemisinus brevis and H. cubanianus). The extremely low densities of other mollusks in the Tuxpam and Tecolutla rivers are in agreement with statements by Karatayev et al. (2008) who suggested this is one of the major impacts of T. granifera on the indigenous mollusk fauna and is a preliminary stage in the eradication of native species. Pointier et al. (1998) found that the introduction of thiarids to eradicate schistosomiasis in Martinique island affected two species of Biomphalaria, but impacts were negligible on neritids. This is also in agreement with our findings in the Tuxpam and Tecolutla rivers since N. virginea is the dominant species in the estuarine zone where T. granifera has not become established. Pointier et al. (1998) state that the attributes of T. granifera favoring its rapid spread include parthenogenesis, extremely high densities, ability to support faster currents and dislodgement, and use of the entire stream bed. In our study the CCA indicates that T. granifera in the Tuxpam and Tecolutla rivers is able to establish in a wide variety of fine to coarse substrata under nutrient-rich conditions (particularly nitrogen) and with high BOD5. These capabilities make T. granifera a successful invasive species and provide an explanation for its pattern of distribution and extremely high densities in both rivers.
The bivalve C. fluminea is native to Asia (China, Korea and southeastern Russia) (McMahon 1999; Mouthon 2001) and colonizes both fresh and brackish waters (salinity <10 PSU) (Sousa et al. 2009). It was possibly introduced for the first time in North America before 1924 in British Columbia, Canada (Naranjo and Olivera-Carrasco 2007) and in 1938 to the US, most probably by Chinese immigrants who use this species as food (McMahon 1999). In Mexico it is known from the northern part of the country on both the Gulf and Pacific slopes. In the south its first record dates back to 1992 in Catemaco, Veracruz (Naranjo and Olivera-Carrasco 2007). In the Tecolutla and Tuxpam rivers, C. fluminea showed different patterns of distribution and abundance, ranking second and fourth in IVI, respectively. It had a more limited distribution in Tuxpam River than in Tecolutla River, and was found in the estuarine zone in the Tecolutla (at Tx7). Sousa et al. (2008) say the attributes of C. fluminea favoring its role as an invasive species include rapid growth, early sexual maturity, short lifespan, high fecundity and its
association with diverse human activities. However, Souza et al. (2008), also mention this species was adversely affected in sites with inputs of organic contaminants, while De la Hoz (2008) found it was adversely affected by drops in the water level. Likewise, Sousa et al. (2008) report C. fluminea is successful in environments without considerable water level fluctuations. In our study, the Tuxpam and Tecolutla rivers were found to receive nutrient and organic matter inputs and to fluctuate in water level as a result of floods and torrential flows due to rainfall of northern winds and hurricane seasons, as opposed to the dry season when flow decreases. These factors are perhaps responsible for the low densities and limited distribution of C. fluminea in these rivers, despite reports by other authors of its invasive capability (Mouthon 2001; Mouhton and Parghentanian 2004). Phelps (1994) states that C. fluminea may experience population declines after reaching the lag period of invasion. This species may therefore be undergoing a population decline since records of its presence in the state of Veracruz date back to 1992 (Naranjo and Olivera-Carrasco 2007). This, along with unfavorable abiotic factors, may explain the low densities and the relative limited distribution of this species in the Tuxpam and Tecolutla rivers. Type of substratum is another factor that has been examined in regard to the establishment of C. fluminea. It has been found primarily in fine to coarse sandy substrata (Cordeiro and MacWilliams 1999; Paunovi et al. 2007; Sousa et al. 2008), although De la Hoz (2008) reports its occurrence in a muddy substratum. In the Tuxpam and Tecolutla rivers it was present in substrata ranging from coarse sand to fine-grained sediment.
Negative impacts due to high densities of C. fluminea include biofouling (especially in power facilities), occlusion of small diameter pipelines, irrigation canals and domestic water supply systems. It is also able to alter the substratum and affect native species (Paunovi et al. 2007). There are no records of biofouling by this species in our study area, but a potential risk exists, particularly in the Tuxpam River in which C. fluminea has colonized the estuarine zone where a seaport and a power plant are located.
It has been reported that when T. granifera is introduced in places previously occupied by M. tuberculata, the former rapidly outnumbers the latter in terms of density (Pointier et al. 1998). Contreras-Arquieta et al. (1995) record presence of M. tuberculata in both the Tuxpam
E . López -López e t a l .
448
and Tecolutla rivers, but did not report T. granifera. Thus, it appears that in these rivers T. granifera is an alien species that may have recently established in these rivers that are experiencing changes in species invasion processes that are resulting in T. granifera being favored over the two other non-indigenous species. In agreement with Pointier et al. (1998) it appears from our study that T. granifera attains its higher population densities through competitive advantage.
In conclusion, this study lends further support to earlier evidence that T. granifera is a very successful alien species. It has become the dominant mollusk in both the Tuxpam and Tecolutla rivers. C. fluminea, is the other main component in the benthic freshwater zones of both rivers. Environmental conditions prevailing in the Tuxpam and Tecolutla rivers are suitable for T. granifera and C. fluminea species invaders, such as water temperature regimes, substratum availability and high levels of nutrients which increase food availability. Pronounced depletions in density during the rainy and northern winds and hurricanes seasons could indicate that the mollusks are removed by the current during stormy torrential floods. Tarebia granifera has capabilities for re- colonization after torrential rains and their populations respond quickly during the dry season when nutrients favor the food availability, and in such situations may be more successful than C. fluminea and M. tuberculata. All three alien species, however, constitute a serious threat to native aquatic mollusks, since they have become the dominant components of the malacological community in both these rivers, where native species have been localized to narrow habitats and occur in relatively low densities.
Acknowledgements
This research was financed by the Joint Fund of the National Science and Technology Council (CONACyT Mexico) and the Veracruz state government (Project 41750) as well as by the Research and Postgraduate Studies Secretariat (SIP) of the National Polytechnic Institute (IPN- Mexico). Authors thank the reviewers for their valuable comments to the manuscript and consequent suggestions that improve this paper.
References
Abbot RT (1952) A study of an intermediate snail host (Thiara granifera) of the oriental lung fluke (Paragonimus). Proceedings of the United States National Museum 102: 71-116
APHA (American Public Health Asociation) (1985) Standard methods: for the examination of water and wastewater. APHA, AWWA, WPCF, Washington, DC
Arriaga L, Aguilar V, Alcocer D (2002) Aguas continentales y diversidad biológica de México. Comisión Nacional para el Conocimiento y Uso de la Biodiversidad. México. http://www.conabio.gob.mx/conocimiento/regionalizacio n/doctos/hidrologicas.html (Accesed 18 November 2008)
Bezaury CJE, Waller R, Sotomayor L, Li X, Anderson S, Sayre R, Houseal B (2000) Conservation of biodiversity in Mexico: ecoregions, sites and conservation targets. The Nature Conservancy, Mexico Division, 122 p
Brodie JE, Mitchell AW (2005) Nutrients in Australian tropical rivers: changes with agricultural development and implications for receiving environments. Marine and Freshwater Research. Forum on sustainable Futures for Australia´s Tropical Rivers, Darwin, Australia 56:279- 302
Carlton JT, Geller JB (1993) Ecological roulette: the global transport of nonindigenous marine organisms. Science 261: 78-82 doi:10.1126/science.261.5117.78
Cohen AN, Carlton JT (1998) Accelerating invasion rate in a highly invaded estuary. Science 279: 555-558 doi:10.1126/science.279.5350.555
CONABIO (2008) Sistema de información sobre especies invasoras en México. Comisión Nacional para el Conocimiento y Uso de la Biodiversidad. http://www.co nabio.gob.mx/invasoras (Accessed 13 February 2009)
CONAGUA (2007) Estadísticas del agua en México. Secretaría de Medio Ambiente y Recursos Naturales. México DF. México 259 pp http://www.CONAGUA07/ Noticias/EAM_2007.zip (Accessed 10 January 2009)
Contreras-Arquieta A (1998) News records of the snail Melanoides tuberculata (Müller 1774) (Gastropoda: Thiaridae) in the Cuatro Cienegas Basin, and its distribution in the state of Coahuila, México. The Southwestern Naturalist 43(2): 243-286
Contreras-Arquieta A (2000) Bibliografía y lista taxonómica de las especies de moluscos dulceacuícolas en México. Mexicoa 2(1):40-53
Contreras-Arquieta A, Guajardo-Martínez G, Contreras- Balderas S (1995) Thiara (Melanoides) tuberculata (Müller 1774) (Gastropoda: Thiaridae), su probable impacto ecológico en México. Publicaciones Biológicas. FCB UANL, México 8(1):17-24
Cordeiro JR, MacWilliams S (1999) Ocurrence of the Asian clam Corbicula fluminea (Müller, 1774) (Bivalvia: Sphaeriacea: Corbiculidae) in Colorado. Veliger 42 (3): 278-280
Cózatl-Manzano R, Naranjo-García E (2007) First records of freshwater molluscs from the ecological reserve El Edén, Quintana Roo, Mexico. Revista Mexicana de Bio- diversidad 78:303-310
Davis MA, Grime JP, Thompson K (2000) Fluctuating resources in plant communities: a general theory of invasibility. Journal of Ecology 88: 528-534 doi:10.1046/j.1365-2745.2000.00473.x
De la Hoz AMV (2008) Primer registro en Colombia de Corbicula fluminea (Mollusca: Bivalvia: Corbiculidae), una especie invasora. Boletín de Investigaciones Marinas y Costeras 37(1): 197-202
449
Karatayev, AY, Padilla DK, Minchin D, Boltovskoy D, Burlakova LE (2007) Changes in global economies and trade: the potential spread of exotic freshwater bivalves. Biological Invasions 9:161-180 doi:10.1007/s10530- 006-9013-9
Karatayev AY, Burlakova LE, Karatayev YV, Padilla DK (2008) Introduction, distribution, spread, and impacts of exotic freshwater gastropods in Texas. Hydrobiologia 619: 181-194 doi:10.1007/s10750-008-9639-y
Krebs CJ (1989) Ecological methodology. Harper and Row Publishers, New York, 654 pp
Lake PS (2000) Disturbance, patchiness, and diversity in streams. Journal of the North American Benthological Society 19: 573-592 doi:10.2307/1468118
Leung B, Lodge DM, Finnoff D, Shogren JF, Lewis MA, Lamberti G (2002) An ounce of prevention or a pound of cure: Bioeconomic risk analysis of invasive species. Proceedings of the Royal Society of London 269: 2407- 2413 doi:10.1098/rspb.2002.2179
Mack RN, Lonsdale M (2001) Humans as global plant dispersers; getting more than we bargained for. Bioscience 51: 95-102 doi:10.1641/0006-3568(2001) 051[0095:HAGPDG]2.0.CO;2
Mathooko, JM, Mavuti KM (1992) Composition and seasonality of benthic invertebrates, and drift in the Naro Moru River, Kenya. Hydrobiologia 232: 47-56
McMahon RF (1999) Invasive characteristics of the freshwater bivalve Corbicula fluminea. In Claudi R, Leach J (eds). Nonindigenous Freshwater Organisms: Vectors, Biology and Impacts. Lewis Publishers, Boca Raton, pp 315-343
Morrone JJ, Márquez J (2001) Halffter's Mexican Transition Zone, beetle generalized tracks, and geographical homology. Journal of Biogeography 28: 635-650 doi:10.1046/j.1365-2699.2001.00571.x
Mouthon J (2001) Life cycle and populations dynamics of the Asian clam Corbicula fluminea (Bivalvia: Corbiculidae) in the Saone River at Lyon (France). Hydrobiologia 452: 109-119 doi:10.1023/A:1011980011889
Mouthon J, Parghentanian T (2004) Comparison of the life cycle and population dynamics of two Corbicula species, C. fluminea and C. fluminalis (Bivalvia: Corbiculidae) in two French canals. Archiv fuer Hydrobiologie 161: 267- 287 doi:10.1127/0003-9136/2004/0161-0267
Myers N, Mittermeier, RA, Mittermeier CG, da Fonseca GAB, Kent J (2000) Biodiversity hotspots for conservation priorities. Nature (403): 853-858 doi:10.1038/35002501
Naranjo GE (2003) Moluscos continentales de México: Dulceacuícolas. Revista de Biología Tropical 51 (3): 495-505
Naranjo E, Olivera-Carrasco MT (2007) Moluscos dulceacuícolas introducidos en México. In: Ríos-Jara, E, Esqueda-González MC, Galván-Villa CM (eds), Estudios sobre la Malacología y Conquiliología en México. Universidad de Guadalajara, México, pp 28-30
NOM-021-RECNAT-2002 Norma Oficial Mexicana (2000) Que establece las especificaciones de fertilidad, salinidad y clasificación de suelos. Estudios, muestreo y análisis. http://www.semarnat.gob.mx/leyesynormas/ Normas%20Oficiales%20Mexicanas%20vigentes/NOM- 021-RECNAT-2000.pdf (Accessed 17 February 2006)
Ortíz-Lozano L, Granados-Barba A, Solís-Weissa V, García- Salgado MA (2005) Environmental evaluation and development problems of the Mexican Coastal Zone. Ocean & Coastal Management 48: 161-176 doi:10.1016/ j.ocecoaman.2005.03.001
Paunovi M, Csányi B, Kneevi S, Simi V, Nenadi D, Jakovev-Todorovi D, Stojanovi B, Caki P (2007) Distribution of Asian clams Corbicula fluminea (Müller, 1774) and C. fluminalis (Müller, 1774) in Serbia. Aquatic Invasions 2: 99-106 doi:10.3391/ai.2007.2.2.3
Phelps HL (1994) The Asiatic clam (Corbicula fluminea) invasion and system-level ecological change in the Potomac River Estuary near Washington, D.C. Estuaries 17: 614-621 doi:10.2307/1352409
Pointier JP, Jourdane J (2000) Biological control of the snail hosts of schistosomiasis in areas of low transmission: the example of the Caribbean area. Acta Tropica 77: 53-60 doi:10.1016/S0001-706X(00)00123-6
Pointier JP, Samadi S, Jarne P, Delay B (1998) Introduction and spread of Thiara granifera (Lamarck, 1822) in Martinique, French West Indies. Biodiversity and Con- servation 7: 1277-1290 doi:10.1023/A:1008887531605
Rahel FJ (2000) Homogenization of fish faunas across the Unites States. Science 288: 854-856 doi:10.1126/ science.288.5467.854
Ruiz GM, Fofonoff PW, Carlton JT, Wonham MJ, Hines AH (2000) Invasion of coastal marine communities in North America: apparent patterns, processes, and biases. Annual Review of Ecology and Systematics 31: 481-531 doi:10.1146/annurev.ecolsys.31.1.481
Sanchez N, De la Lanza G (1996) The influence of regional climate in a lagoon in northeastern Mexico. Atmósfera 6:201-221
Sax DF, Gaines SD, Brown JH (2002) Species invasions exceed extinctions on islands worldwide: A comparative study of plants and birds. American Naturalist 160: 766- 783 doi:10.1086/343877
Sousa R, Rufino M., Gaspar M, Antunes C, Guilhermino L (2008) Abiotic impacts on spatial and temporal distribution of Corbicula fluminea (Müller, 1774) in the River Minho Estuary, Portugal. Aquatic Conservation- Marine and Freshwater Ecosystems 18: 98-110 doi:10.1002/aqc.838
Sousa R, Gutiérrez JL, Aldridge DC (2009) Non-indigenous invasive bivalves as ecosystem engineers. Biological Invasions doi:10.1007/s10530-009-9422-7
Strong EE, Gargominy O, Winston F, Ponder PB (2008) Global diversity of gastropods (Gastropoda; Mollusca) in freshwater. Hydrobiologia 595:149-166 doi:10.1007/ s10750-007-9012-6
Thompson FG (2008) An annotated checklist and bibliography of the land and freshwater snails of Mexico and Central America http://www.flmnh.ufl.edu/malaco logy/mexico-central_america_snail_checklist (Accessed 13 April 2009)
Vitousek PM, D’Antonio CM, Loope LL, Westbrooks R (1996) Biological invasions as global environmental change. American Scientist 84: 468-478 http://www.XLSTAT.com (Accessed 10 January 2009)
Wetzel RG, Likens GE (2000) Limnological Analyses. Springer-Verlag, NY, 429 pp
450
Annex 1 Geographic coordinates of study sites in Tuxpan and Tecolutla rivers
Geographic coordinates Study Site Location name
Latitude, N Longitude, W
Altitude, masl.
Tuxpam River Tx1 La Reforma 20°51.172' 97°53.029' 101 Tx 2 Úrsulo Galván 20°53.718' 97°47.268' 93 Tx 3 Rancho el Cieruelo 20°57.349' 97°46.472' 44 Tx 4 San Antonio 20°55.447' 97°42.795' 38 Tx 5 Chapopote Nuñez 20°55.601' 97°36.469' 23 Tx 6 Buena Vista 20°55.727' 97°40.797' 20 Tx 7 Tampiquillo 20°57.228' 97°31.699' 19 Tx 8 El Higueral 20°55.556' 97°29.629' 9 Tx 9 Quinta Las Puertas 20°54.963' 97°25.748' 5 Tx 10 Puente Tuxpan 20°56.842' 97°24.054' 3 Tx 11 Boca de la Laguna de Tampamachoco 20°58.007' 97°19.572' 0
Tecolutla River
Tc1 Entabladero 20°16.065' 97°33.475' 87 Tc 2 Arenal 20°15.907' 97°30.647' 70 Tc 3 El Chacal 20°13.223' 97°27.828' 71 Tc 4 Espinal 20°14.503' 97°23.893' 43 Tc 5 Paso de Valencia 20°16.170' 97°19.676' 11 Tc 6 Puente Remolino 20°23.817'' 97°14.169' 8 Tc 7 Ignacio Muñoz Zapotal 20°27.347' 97°11.791' 6 Tc 8 Puente Chalana 20°26.583' 97°07.479' 3 Tc 9 Tecolutla 20°28.492' 96°00.256' 0
Annex 2 Code of abbreviations: species, environmental factors and sediment type in the ACP and CCA biplots
Environmental abbreviations: Sediment abbreviations: Species abbreviations: Alc= alkalinity ag=coarse sand Be= Brachidontes exustus Alt= altitude am= medium sand Bsp= Biomphalaria sp. BOD= Biochemical oxygen demand gu= pebbles Cf= Corbicula fluminea Cl= chloride gr=gravel He= Hebetancylus excentricus Color= color ag= very coarse sand Hm= Haitia mexicana Ctot= total coliforms amf= very fine sand Mc= Melampus coffeus DO= dissolved oxygen lg= gross silt Md= Micromenetus dilatatus Dur= hardness lmf= very fine silt Mt= Melanoides tuberculatas NH3= ammonia lm= medium silt NV = Neritina virginia NO2= nitrites lf= fine silt Pc= Pomacea flagellata NO3= nitrates Ssp= Succinea sp. Ntot= total nitrogen Tg= Tarebia granifera om= organic matter OrtPO4= orthophosphate Pt= total phosphorus Sal= salinity SO4= sulfates TDS= total dissolved solids Tmp= medium size particle TSS= total suspended solids Turb= turbidity Twat= water temperature V curr= current velocity
<< /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /All /Binding /Left /CalGrayProfile (Dot Gain 20%) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (U.S. Web Coated \050SWOP\051 v2) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Warning /CompatibilityLevel 1.4 /CompressObjects /Tags /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages true /CreateJDFFile false /CreateJobTicket false /DefaultRenderingIntent /Default /DetectBlends true /DetectCurves 0.0000 /ColorConversionStrategy /LeaveColorUnchanged /DoThumbnails false /EmbedAllFonts true /EmbedOpenType false /ParseICCProfilesInComments true /EmbedJobOptions true /DSCReportingLevel 0 /EmitDSCWarnings false /EndPage -1 /ImageMemory 1048576 /LockDistillerParams false /MaxSubsetPct 100 /Optimize true /OPM 1 /ParseDSCComments true /ParseDSCCommentsForDocInfo true /PreserveCopyPage true /PreserveDICMYKValues true /PreserveEPSInfo true /PreserveFlatness true /PreserveHalftoneInfo false /PreserveOPIComments false /PreserveOverprintSettings true /StartPage 1 /SubsetFonts true /TransferFunctionInfo /Apply /UCRandBGInfo /Preserve /UsePrologue false /ColorSettingsFile () /AlwaysEmbed [ true ] /NeverEmbed [ true ] /AntiAliasColorImages false /CropColorImages true /ColorImageMinResolution 300 /ColorImageMinResolutionPolicy /OK /DownsampleColorImages true /ColorImageDownsampleType /Bicubic /ColorImageResolution 300 /ColorImageDepth -1 /ColorImageMinDownsampleDepth 1 /ColorImageDownsampleThreshold 1.50000 /EncodeColorImages true /ColorImageFilter /DCTEncode /AutoFilterColorImages true /ColorImageAutoFilterStrategy /JPEG /ColorACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /ColorImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000ColorACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000ColorImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 300 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /GrayImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000GrayACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000GrayImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 1200 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict << /K -1 >> /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False /Description << /CHS <FEFF4f7f75288fd94e9b8bbe5b9a521b5efa7684002000500044004600206587686353ef901a8fc7684c976262535370673a548c002000700072006f006f00660065007200208fdb884c9ad88d2891cf62535370300260a853ef4ee54f7f75280020004100630072006f0062006100740020548c002000410064006f00620065002000520065006100640065007200200035002e003000204ee553ca66f49ad87248672c676562535f00521b5efa768400200050004400460020658768633002> /CHT <FEFF4f7f752890194e9b8a2d7f6e5efa7acb7684002000410064006f006200650020005000440046002065874ef653ef5728684c9762537088686a5f548c002000700072006f006f00660065007200204e0a73725f979ad854c18cea7684521753706548679c300260a853ef4ee54f7f75280020004100630072006f0062006100740020548c002000410064006f00620065002000520065006100640065007200200035002e003000204ee553ca66f49ad87248672c4f86958b555f5df25efa7acb76840020005000440046002065874ef63002> /DAN <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> /DEU <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> /ESP <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> /FRA <FEFF005500740069006c006900730065007a00200063006500730020006f007000740069006f006e00730020006100660069006e00200064006500200063007200e900650072002000640065007300200064006f00630075006d0065006e00740073002000410064006f00620065002000500044004600200070006f007500720020006400650073002000e90070007200650075007600650073002000650074002000640065007300200069006d007000720065007300730069006f006e00730020006400650020006800610075007400650020007100750061006c0069007400e90020007300750072002000640065007300200069006d007000720069006d0061006e0074006500730020006400650020006200750072006500610075002e0020004c0065007300200064006f00630075006d0065006e00740073002000500044004600200063007200e900e90073002000700065007500760065006e0074002000ea0074007200650020006f007500760065007200740073002000640061006e00730020004100630072006f006200610074002c002000610069006e00730069002000710075002700410064006f00620065002000520065006100640065007200200035002e0030002000650074002000760065007200730069006f006e007300200075006c007400e90072006900650075007200650073002e> /ITA <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> /JPN <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> /KOR <FEFFc7740020c124c815c7440020c0acc6a9d558c5ec0020b370c2a4d06cd0d10020d504b9b0d1300020bc0f0020ad50c815ae30c5d0c11c0020ace0d488c9c8b85c0020c778c1c4d560002000410064006f0062006500200050004400460020bb38c11cb97c0020c791c131d569b2c8b2e4002e0020c774b807ac8c0020c791c131b41c00200050004400460020bb38c11cb2940020004100630072006f0062006100740020bc0f002000410064006f00620065002000520065006100640065007200200035002e00300020c774c0c1c5d0c11c0020c5f40020c2180020c788c2b5b2c8b2e4002e> /NLD (Gebruik deze instellingen om Adobe PDF-documenten te maken voor kwaliteitsafdrukken op desktopprinters en proofers. De gemaakte PDF-documenten kunnen worden geopend met Acrobat en Adobe Reader 5.0 en hoger.) /NOR <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> /PTB <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> /SUO <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> /SVE <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> /ENU (Use these settings to create Adobe PDF documents for quality printing on desktop printers and proofers. Created PDF documents can be opened with Acrobat and Adobe Reader 5.0 and later.) >> /Namespace [ (Adobe) (Common) (1.0) ] /OtherNamespaces [ << /AsReaderSpreads false /CropImagesToFrames true /ErrorControl /WarnAndContinue /FlattenerIgnoreSpreadOverrides false /IncludeGuidesGrids false /IncludeNonPrinting false /IncludeSlug false /Namespace [ (Adobe) (InDesign) (4.0) ] /OmitPlacedBitmaps false /OmitPlacedEPS false /OmitPlacedPDF false /SimulateOverprint /Legacy >> << /AddBleedMarks false /AddColorBars false /AddCropMarks false /AddPageInfo false /AddRegMarks false /ConvertColors /NoConversion /DestinationProfileName () /DestinationProfileSelector /NA /Downsample16BitImages true /FlattenerPreset << /PresetSelector /MediumResolution >> /FormElements false /GenerateStructure true /IncludeBookmarks false /IncludeHyperlinks false /IncludeInteractive false /IncludeLayers false /IncludeProfiles true /MultimediaHandling /UseObjectSettings /Namespace [ (Adobe) (CreativeSuite) (2.0) ] /PDFXOutputIntentProfileSelector /NA /PreserveEditing true /UntaggedCMYKHandling /LeaveUntagged /UntaggedRGBHandling /LeaveUntagged /UseDocumentBleed false >> ] >> setdistillerparams << /HWResolution [2400 2400] /PageSize [612.000 792.000] >> setpagedevice