key: cord-0009891-lyjxdgbw
authors: Sánchez‐Higueredo, Lorena Elisa; Ramos‐Leal, José Alfredo; Morán‐Ramírez, Janete; Moreno‐Casasola Barceló, Patricia; Rodríguez‐Robles, Ulises; Hernández Alarcón, María Elizabeth
title: Ecohydrogeochemical functioning of coastal freshwater herbaceous wetlands in the Protected Natural Area, Ciénaga del Fuerte (American tropics): Spatiotemporal behaviour
date: 2020-01-06
journal: Ecohydrology
DOI: 10.1002/eco.2173
sha: f4a29b82a5fa1f84c34a34e65dfdc7a09acf89c9
doc_id: 9891
cord_uid: lyjxdgbw

Coastal zones are characterized by the interactions between continents and oceans and, therefore, between fresh and salt surface and groundwater. The wetlands of coastal zones represent transitional ecosystems that are affected by these conditions, although little is known about the hydrogeochemistry of wetlands, especially coastal wetlands. In the present study, the hydrogeochemical characterization of coastal freshwater herbaceous wetlands in the Ciénaga del Fuerte Protected Natural Area in Veracruz, Mexico, in the American tropics was carried out per plant community. Four herbaceous wetlands (alligator flag, saw grass, cattail, and floodplain pasture) were monitored to understand the origin of the water feeding these ecosystems, the hydrogeochemical composition of groundwater, and the relationship between the groundwater and ecology of these ecosystems during dry and rainy seasons. The results indicate that Ciénaga del Fuerte is located in a regional discharge area and receives local recharge, so it is fed by both regional and local flows. The chemical composition varied temporally and spatially, creating unique conditions that determined the habitat occupied by the hydrophytic vegetation. The spatiotemporal behaviour of groundwater is one factor that, along with the hydroperiod, determines wetland dynamics and affects wetland biota (ecohydrogeochemistry). Generalist plant communities established in zones of local recharge, whereas other more specialized and/or plastic communities inhabited zones receiving regional flows with greater ion concentrations. This information forms the basis for establishing an appropriate scale (municipal, state, or larger regions) for the sustainable management of goods and services provided by the wetlands.

Coastal zones are highly dynamic and productive areas where the continents, oceans, and atmosphere interact. Diverse ecosystems are present in these zones, including beaches, dunes, and wetlands such as reefs, mangroves, floodplain forests, coastal lagoons, estuaries, and herbaceous wetlands (e.g., tulares, carrizales, and popales). Evidence of the dynamic nature of coastal zones includes erosion processes, which affect beaches and dunes, and meteorological phenomena, such as hurricanes and torrential rainfall, which affect extensive coastal areas.

Additionally, coastal zones serve as discharge areas for groundwater and surface water originating from the continent. However, coastal regions are also vulnerable to climate change and rising sea levels and phreatic levels as well as the marine intrusion and/or soil salinization (Spalding et al., 2014) . These factors can lead to the loss and/or migration of wetlands, habitat fragmentation, and the reduction or ecosystem services loss (Intergovernmental Panel on Climate Change, 2014; Nicholls & Cazenave, 2010) .

Wetlands, particularly coastal wetlands, are important ecosystems because of the large quantity and variety of ecosystem services that they provide to society (Costanza et al., 1997) . As transitional ecosystems between terrestrial and aquatic environments (Mitsch & Gosselink, 2015) , wetlands are strongly influenced by hydrology (Gusyev & Haitjema, 2011) . Additionally, wetlands are often located in discharge areas and therefore have an important contribution of groundwater (Winter, 1999) , which is crucial for nutrient transport and for wetland salinity (Jolly et al., 2008) . Both of them (nutrient and salinity) and water have ecological effects, influencing the presence or type of vegetation that establishes, for example (Morris, 1995) .

Finally, in coastal wetlands, all these factors should consider interactions with both groundwater and marine water too (Qu et al., 2017) .

Traditionally, ecological studies in wetlands have been carried out to characterize vegetation composition, biodiversity, water quality, and its effects on wetlands dynamics. Water studies in wetlands tend to be limited to surface water (Kors et al., 2012) and, occasionally, to interstitial water (water present at the root level, Weterbach et al., 2016) , without understanding the role of groundwater in wetlands, its chemical composition, or the hydrogeochemical processes influencing these ecosystems (Hunt, Krabbenhoft, & Anderson, 1997; Liu & Mou, 2016) . With respect to hydrogeochemical studies in coastal areas, this have been carried out to understand the water quality of aquifers for human use (Chidambaram et al., 2018; Lee & Song, 2007) and, more recently, to identify the causes of salinization (salt intrusion, geological processes, or anthropic contamination, Böhlke & Denver, 1995; Lee & Song, 2007; Bouzurra, Bouhlila, Elango, Slama, & Ouslati, 2017) . Some hydrogeochemical studies have been focused to understand dynamics between groundwater and surface water to reduce anthropic effects but without an ecological approximation (Ladouche & Weng, 2005) . Liu and Mou (2016) described some interactions between groundwater-surface water and wetlands and the necessity of a new approach to study this ecosystem. Few hydrogeochemical studies have been carried out in tropical coastal wetlands, so the hydrogeology of these ecosystems is largely unknown, including the origin and evolution of the water that feeds them (Hunt et al., 1997; Carol, Mas-Pla, & Kruse, 2013) . In a temperate climate (Scotland), Malcolm and Soulsby (2001) performed the hydrogeochemical characterization of a coastal aquifer associated with an interdunal wetland complex to understand its biodiversity and its capacity to maintain the quality of fresh water despite its location and land-use change. House and Sorensen (2015) characterized a riparian wetland in the United Kingdom using a model that incorporated temperature and botanical indicators (hydrophytes species present in sampling sites) in order to determine the dynamics between groundwater and surface water. In Latinamerica, Carol et al. (2013) characterized the wetlands in the Bay of Samboronbón, Argentina, with the objective of establishing criteria for the conservation of their water resources, and Yetter (2004) characterized the hydrogeochemistry, the origin, and the quantity of water that is feeding mangroves and herbaceous wetlands in the Ramsar Site La Mancha in Mexico.

Generally, these authors conclude that information is lacking on groundwater (quality and quantity), one of the main flows to wetlands, and that such information is crucial for the adequate management and conservation of these ecosystems and their goods and services, especially due to the population growth in coastal areas. It is estimated that 50% of the world population is living within 100 km of the coast (Small & Nicholls, 2003) and that 10% of the population in coastal areas is located at an elevation of lower than 10 masl (Spalding et al., 2014) . In the state of Veracruz, for example, 27% of the population lives less than 20 km from the coast (Mendoza-González, Martínez, Lithgow, Pérez-Maqueo, & Simonin, 2012) , which is a concern, considering that this Mexican state is one of the most vulnerable to climate change (Monterroso et al., 2014) and to rising sea levels, with reported increases of 1.9 mm year −1 (Zavala-Hidalgo, de Buen Kalman, Romero-Centeno, & Hernández Maguey, 2010) .

The present study presents a hydrogeochemical characterization of coastal freshwater herbaceous wetlands in the Protected Natural Area (PNA) Ciénaga del Fuerte (American tropics). The objective was to understand the hydrogeochemistry of the wetland in the Ciénaga del Fuerte PNA and the origin of the water feeding this wetland in addition to how these latter factors could influence the plant communities. Ultimately, this information would provide a basis for understanding the local and regional functioning of these wetlands.

Additionally, this key information is the first step for quantifying ecosystem services and for generating policies to conserve wetland ecosystems through sustainable management. 

The study area is located near the regional discharge area of the Western Sierra Madre (WSM). This latter mountain range is composed of numerous geological units of marine origin that are strongly folded F I G U R E 1 Location of the Ciénaga del Fuerte Protected Natural Area in the municipality of Tecolutla, Veracruz, Mexico, and monitoring sites location F I G U R E 2 Climatogram of the study area . Data from meteorological station no. 030153 in San Rafael, Veracruz, CONAGUA due to orogenic processes, forming cavities with differing degrees of competence (Moran-Ramírez et al., 2018) as well as regional fractures and faults, which increase the hydraulic conductivity of these mate- -Chapa, 1971; Heim, 1926) . Over this latter unit, the undifferentiated Tamaulipas Formation was deposited during the Middle Cretaceous. It is composed of lime mudstone and wackestone with some intercalations of shale and loam, with a thickness of 400 m (Stephenson, 1922) . The Agua Nueva Formation of the Upper Cretaceous covers this latter unit. It is formed by lime mudstone and wackestone with intercalations of shale, with a thickness of 127 m (Stephenson, 1922) . Over this latter for- F I G U R E 3 Geology of the study area and location of the regional geological section of the Western Sierra Madre (shown in Figure 4 ) in Tecolutla, Veracruz T A B L E 1 Soil properties in a popal-carrizal (Thalia geniculata and Cyperus giganteus) reported by Campos et al. (2011) Depth ( 

The sites with the greatest presence of hydrophytic species in Ciénaga del Fuerte were selected for monitoring. In total, four sites representative of each herbaceous wetland community were selected ( Figure 1 ): one popal, two tular-carrizal communities with different species composition located in distinct sites, and one floodplain pasture (this last site was previously a wetland, Figure 5 ).

In 

In the four monitoring sites, a total of 96 groundwater samples were taken directly from the piezometers in the rainy season (October 2016) and the dry season (April 2017), corresponding with four Samples × Transect × Site × Season (4 × 3 × 4 × 2 = 96 samples). The laboratory analyses were performed according to the methods established in Welch et al. (1996) and Apha (2005) . In each site, physical parameters (temperature, electric conductivity, Total Dissolved Solids (TDS), pH, salinity, dissolved oxygen, and oxidation-reduction potential (ORP)) were measured in situ using a YSI 556 © multiparametric probe. All groundwater samples were collected in high-F I G U R E 4 Regional transversal section of geological characteristics and groundwater flow from the Western Sierra Madre to the coastal plain of the Gulf of Mexico density polyethylene bottles for major ion analysis; prior to use, all bottles were triple washed with abundant deionized water.

The water samples for cation and metal analyses were immediately acidified after being taken with ultrapure nitric acid until reaching a pH < 2. All samples were conserved at 4 C. The principal ions were analysed in the Ecological Engineering and Wetland Biogeochemistry Laboratory (Laboratorio de Ingeniería Ecológica y Biogeoquímica de Humedales) of the Institute of Ecology using ion chromatography (Dionex Chromeleon ICS-1100). The anions were analysed using an eluent of 4.5-mM Na 3 CO 3 /0.8-mM NaHCO 3 in an Anion Self-Regenerating Suppressor (ASRS 300 2 mm) in Auto Suppression Recycle Mode at a flow rate of 0.25 ml min −1 , a temperature of 30 C, an applied current of 7 mA, and an injection volume of 5 μl.

The cations were analysed using an eluent of 20-mM methanesulfonic acid via suppressed conductivity detection in a Cation Self-Regenerating Suppressor (CSRS ® Ultra II, 2 mm) in Auto Suppression

Recycle Mode at a flow rate of 0.25 ml min −1 , an ambient temperature, an applied current of 15 mA, and an injection volume of 2.5 ml.

The alkalinity was quantified in situ by the titration method (Association of Official Analytical Chemists, 1980). All chemical analyses had an ionic balance lower than 10%, which was considered acceptable.

To characterize the dominant vegetation, in each quadrant, per cent cover and height of each species were monitored. Per cent cover was calculated using the Westhoff, and van deer Maarel (1978) coverabundance scale.

The resulting hydrogeochemical data were used to generate Piper diagrams to determine the water families and descriptive statistics and are presented in Table 2 ; Mifflin diagrams were used to define the flow systems; Gibbs diagrams helped to identify the influence of evaporation processes, water-rock interactions, and rainfall; and biplots were used to identify the occurrence of other processes such as ionic exchange, mixing, and the overall evolution of groundwater.

The first site is located near the centre of the PNA. It is a popal wetland dominated by T. geniculata (commonly known as alligator flag) and L. hexandra (southern cut grass) containing one to five species; it was labelled as Thalia (Figure 5a ). The second site is located near the outer limit of the PNA and is surrounded by agricultural fields. It is a Lippia nodiflora (tangle fogfruit) but contains one to 10 species of diverse introduced and native grasses; it was labelled as floodplain pasture (Figure 5d ).

In the Piper diagram (Figure 6 ), five main water types were identified:

40% of the samples corresponded with CaHCO 3 type (Type II), 20%

with NaCl type (Type I), 27% with NaCaHCO 3 type (Type III), 12%

with NaHCO 3 type (Type VI), and only one sample with CaMgCl type (Type IV).

The samples in the rainy season (October) were mainly distributed in Types II, III, and VI (CaHCO 3 , NaCaHCO 3 , and NaHCO 3 , respectively and Type VI (NaHCO 3 ). During the dry season, the Group 1 samples did not vary considerably with respect to the rainy season, but some samples did correspond with Type III (NaCaHCO 3 ), coinciding with the increased temperatures in this season. Meanwhile, Group 2 dif-fered the most between seasons. During the dry season, the large majority of its samples were Type 1 (NaCl). A few samples were Type

Type VI (NaHCO 3 ). Therefore, Group 2 is characterized by the presence of more evolved water samples.

The evolution of groundwater is related to its physicochemical content, due to the interaction of the medium through which it circulates.

It is also a function of residence time and distance travelled; in such a way, that recent infiltration waters have low concentrations of their physicochemical parameters, whereas more evolved waters have a higher concentration of these components (Tóth, 1999) . Therefore, groundwater will have less dissolved solids in the recharge zone.

These solids will increase as water circulates. This type of relationship was addressed by Mifflin (1968), which related the content of Na + K vs Cl + SO 4 with flow systems (small local, local, and regional) and was corroborated with tritium.

The SO 4 + Cl versus Na + K relationship in the Mifflin diagram Group 2 is associated with samples from the Thalia and Typha-Cladium sites. These samples tend to correspond with more evolved waters and regional flow. 

The local recharge sites (Group 1) are mostly stable with respect to ion concentrations, which are low in both seasons. In contrast, regional recharge sites (Group 2) show slightly diluted ion concentrations in the rainy season, so some water mixing processes likely occur during this season. These differences can be visualized on species distribution (Table 3) .

The groundwater samples from the floodplain pasture and Cladium-Typha-Cyperus (Group 1) showed characteristics of rainwater and varied little between seasons (rainy and dry). So the sites of this group are likely present in the local recharge area despite being located near the coastline and the outer border of the PNA (Figure 5b,d) .

The floodplain pasture is the site with the highest diversity of plant species because it has the lowest level of flooding, which favours the presence of both hydrophytic and terrestrial species. Also, it has lower ion concentrations, which create more favourable conditions for most species. This site experienced disturbance 20 years ago and is therefore regenerating and is subjected to the constant perturbation by grazing cattle. On the other hand, the Cladium-Typha-Cyperus site had the highest level of flooding of all sites, even in the dry season. Its dominant species was C. jamaicense, even though T. domingensis is reportedly one of the most tolerant species to flooding in terms of flood depth (Chen & Vaughan, 2014 ) and time exposed to flooding (Cronk & Fennessy, 2001) because it possesses several mechanisms that enable it to tolerate prolonged periods of flooding (Armstrong, Justin, Beckett, & Lythe, 1991; Colmer, 2003; Cronk & Fennessy, 2001; Voesenek & Bailey-Serres, 2015) . Interestingly, these adaptions can signify that low levels of flooding (−10 cm) are stressful for this species (unpublished results). Meanwhile, C. jamaicense is reportedly more sensitive to flooding (Newman, Grace, & Koebel, 1996) and to water with high phosphorus concentrations. For these reasons, it was displaced by T. domingensis in the Everglades as this environment transformed from oligotrophic to eutrophic (Davis, 1991) . In the present study, the dominance of C. jamaicense in the most flooded site may be due to its higher sensitivity to other factors that are not present as the major ion concentration.

Accordingly, C. jamaicense may take advantage of this opportunity niche despite the flood level favouring T. domingensis. Species present in Group 1

can be considered more generalist and are fed with water characteristics of rainwater and inhabit environments that are favourable for the establishment of a greater number of species and/or environments that may be considered oligotrophic.

Wetlands located in regional discharge zones

The sites of Group 2 (Thalia and Typha-Cladium) presented both flooded and saturated conditions. Based on the chemical composition of groundwater, these sites are fed by regional flows. sites because of its greater tolerance to the higher ion concentrations in regional discharge compared with C. jamaicense. Overall, greater plasticity is observed in the Group 2 species, which are mainly represented by T. geniculata and T. domingensis. These latter species occupy more specialized habitats compared with the Group 1 species (considered more generalist).

The Ciénaga del Fuerte PNA is a discharge area fed by groundwater from local and regional flows, indicating that some of the wetlands of the PNA are fed by water from regional flows whereas others are fed by local recharge or rainwater. This indicate that PNA Ciénaga del Fuerte requires management at the local level (municipality) as well as at the regional level, including federal entities and their municipalities with jurisdiction over regional recharge area in WSM. This information is an indication of the necessity to conserve and recover forested mountain zones in recharge of watersheds to secure the provision of freshwater to communities in lowlands and to maintain the environmental flow to wetlands and coastal wetlands.

The water chemistry of Ciénaga del Fuerte PNA is influenced by its location near the coastline and extensive citrus orchards. In fact, the area outlying the PNA is part of the most important region for the production of Valencian orange in the country (Sistema de Información Agroalimentaria y Pesquera, 2018). Accordingly, a large portion of the water samples were taken near the zone of saltwater intrusion and/or irrigation return, especially those in Group 2, so if salinization is due to irrigation return, strategies targeting the sustainable development and management of agriculture should be implemented to maintain the quantity and quality of water inflow (whether local or regional in origin) in Ciénaga del Fuerte. If salinization is due to salt intrusion, then it is even more important to maintain the quality and quantity of local and regional flows to minimize or stop it. Further studies are necessary to distinguish which of these latter two processes is most influential for the water chemistry of the PNA.

Currently, there are important efforts to restore the forest high up in the mountains. This work is giving accurate information about a necessity to take care of these recharge areas to conserve wetlands coast. 4 | CONCLUSIONS 1. The Ciénaga del Fuerte PNA is located in a regional discharge area and, based on the Mifflin hydrogeochemical diagram, it is mainly fed by local and regional flows.

2. Two groups of groundwater were identified in the Gibbs diagram.

Group 1 was associated with the floodplain pasture and Cladium-Typha-Cyperus sites, and Group 2 was associated with the Thalia and Typha-Cladium sites. The Group 1 samples had characteristics similar to those of local recharge or rainwater, whereas the Group 2 samples appeared to be more evolved or originate from regional flows.

3. The groundwater of Ciénaga del Fuerte was more influenced by silicate alteration than by carbonate dissolution. 9. The spatiotemporal behaviour of groundwater chemistry is one factor that, along with the hydroperiod, determines the dynamics and functioning of wetlands (eco-hydrogeoperiod).

10. The characterization and spatiotemporal behaviour of the hydrogeochemistry of wetlands are critical for understanding the origin of water feeding wetlands and the interaction between different water flows and wetland ecosystems and their dynamics. Ultimately, this information will provide a better understanding of the influence of water chemistry on the ecology of wetlands, over their floristic composition and to propose management plans including discharges areas (wetland zones) and recharges areas (upstream).

Vásquez for their help in the field work and Roberto Monroy for his help with maps.

We declare the data that support the findings of this study are available from the corresponding author upon reasonable request.

Lorena Elisa Sánchez-Higueredo https://orcid.org/0000-0002-6219-

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This study was funded by Consejo Nacional de Ciencia y Tecnología (CONACYT, Scholarship 391773) and the Instituto de Ecología A.C.(INECOL). We thank Guillermo Marín, Karina Osorio, and Víctor