water Article Páramo Lakes of Colombia: An Overview of Their Geographical Distribution and Physicochemical Characteristics Angela Zapata 1, *, Carlos A. Rivera-Rondón 1 , Daivan Valoyes 1 , Claudia L. Muñoz-López 1 , Marino Mejía-Rocha 2 and Jordi Catalan 3,4 1 Laboratorio de Limnología, Unidad de Ecología y Sistemática-UNESIS, Departamento de Biología, Pontificia Universidad Javeriana, Bogotá 110231, Colombia; crivera@javeriana.edu.co (C.A.R.-R.); dvaloyes@javeriana.edu.co (D.V.); cl.munoz@javeriana.edu.co (C.L.M.-L.) 2 Instituto de Salud Pública, Pontificia Universidad Javeriana, Bogotá 110231, Colombia; marino.mejia@javeriana.edu.co 3 CREAF, Universitat Autònoma de Barcelona Campus, Edifici C, E-08193 Cerdanyola del Vallès, Spain; j.catalan@creaf.uab.cat 4 CSIC, Universitat Autònoma de Barcelona Campus, E-08193 Barcelona, Spain * Correspondence: zapata-a@javeriana.edu.co Abstract: The páramo lakes, Colombia, situated in the neotropical region, are of great value both as natural heritage and as water source to the most populated areas of the Andes, but are threatened by expanding agriculture, livestock, mining, and landscape fragmentation. Nonetheless, a general  assessment of the lakes’ distribution and biogeochemical characteristics was lacking. We made a  complete inventory of the Colombian páramo lakes and characterized their morphometry and water Citation: Zapata, A.; Rivera-Rondón, chemistry based on a survey of 51 lakes in the Eastern Cordillera. There are 3250 lakes distributed C.A.; Valoyes, D.; Muñoz-López, C.L.; across 28 páramo complexes in Colombia, mainly located between 3600 and 4400 m a.s.l. The lakes Mejía-Rocha, M.; Catalan, J. Páramo are usually small (<10 ha) and shallow (<10 m). Most of them are slightly acidic (average pH~6), Lakes of Colombia: An Overview of with high nutrient (total phosphorus ~0.6 mg/L, total nitrogen ~1 mg/L) and total organic carbon Their Geographical Distribution and (~6 mg/L) concentrations and low oxygen (~3.5 mg/L) at the bottom. Water chemistry varies Physicochemical Characteristics. according to two main independent gradients related to watershed bedrock geology and trophic state. Water 2021, 13, 2175. https:// Global change pressures may be challenging the preservation of these unique ecosystems. Increasing doi.org/10.3390/w13162175 the protection of more lake watersheds should reduce these potential impacts by mitigating negative Academic Editors: Salvador synergies with local pressures. Sánchez-Carrillo, Martín Merino-Ibarra and Javier Alcocer-Durand Keywords: the Andes; conservation; global change; high mountain lakes; neotropics; trophic state; wetlands Received: 31 May 2021 Accepted: 20 July 2021 Published: 9 August 2021 1. Introduction Publisher’s Note: MDPI stays neutral The páramo aquatic ecosystems are a unique element of the planet’s natural heritage with regard to jurisdictional claims in and are socially crucial because they provide water to the most densely populated areas of published maps and institutional affil- the neotropical region of Colombia [1]. The páramo extends across high mountains from iations. Ecuador to Venezuela. In these areas, air temperature is relatively constant throughout the year and relative humidity high. These conditions have favored the formation of peat and a large number of wetlands and lakes. The páramo usually presents deep and organic- rich soils. In Colombia, the Andes branch into three mountain ranges in which there are Copyright: © 2021 by the authors. differentiated páramo complexes (Figure 1) above 3000 m altitude. The three mountain Licensee MDPI, Basel, Switzerland. ranges show different amounts of precipitation (1000–4500 mm) [2]. The largest area of This article is an open access article páramo ecosystems in Colombia (70%) is in the Eastern Cordillera followed by the Central distributed under the terms and Cordillera [3]. The Western Cordillera is much lower in altitude and, therefore, holds fewer conditions of the Creative Commons complexes. Tertiary and Quaternary sedimentary rocks characterize the Eastern Cordillera, Attribution (CC BY) license (https:// while the Central combines not only sedimentary material but also plutonic rocks and a creativecommons.org/licenses/by/ history of high volcanism [4]. Paramo vegetation is dominated by grasses (Festuca and 4.0/). Water 2021, 13, 2175. https://doi.org/10.3390/w13162175 https://www.mdpi.com/journal/water Water 2021, Water 13, 2175 2021, 13, x FOR PEER REVIEW 2 of 218 of 16 grasses (Festuca Calamagrostis andand spp.) Calamagrostis spp.)ofand rosette plants therosette plantsfamily Asteraceae of the Asteraceae familywhich (Espeletia spp.), (Espe‐are letia spp.), which are missing from the central and southern Andes [5]. Páramo missing from the central and southern Andes [5]. Páramo complexes are “sky islands” of complexes arenorthern the “sky islands” Andesofand the host northern Andes endemic and host endemic biodiversity biodiversity [6]. Despite [6]. Despite their their extraordinary natural extraordinary natural and societal relevance, there has and societal relevance, there has been limited research on Colombian páramoonlakes. been limited research Colom‐ bian páramo lakes. Figure 1. Distribution of páramo complexes in Colombia. Adapted from Instituto de Investigación Figure 1. Distribution de Recursos BiológicosofAlexander páramo complexes in Colombia. von Humboldt Adapted (2013, 2021). from The box Instituto shows de Investigación the distribution of dethe Recursos Biológicos lakes sampled Alexander for the physicalvon and Humboldt (2013, 2021). The box shows the distribution of the chemical study. lakes sampled for the physical and chemical study. Existing studies have primarily focused on descriptions of the aquatic biota and re‐ Existingwith lationships studies have primarily the environment e.g.,focused on descriptions [7–10]. Very of theanalyzed few studies have aquatic biota and re- functional lationships with aspects such the environment as primary e.g., production and [7–10]. Very trophic few food studies webs have [11–14]. analyzedextensive However, functional aspects surveyssuch as primary of the assessmentproduction and trophic of the general food webs limnological [11–14]. However, characteristics extensive of these lakes are surveys of the assessment of the general limnological characteristics of these lakes are missing. Such studies are required to develop a reference framework for conserving the natural heritage and evaluating global change pressures, including climate shift, atmo- Water 2021, 13, 2175 3 of 16 spheric pollution, and landscape fragmentation [15]. In the present study, we aim to cover the gap by making an inventory of the Colombian páramo lakes and characterizing the water chemistry based on a survey of lakes in the Eastern Cordillera. The Eastern Cordillera holds the greatest páramo extension in Colombia, although it is also the one with the highest human landscape transformation, between 49% and 74% in some areas during the last two centuries [3,16]. Potato crops and livestock are the two activities that historically had the greatest impact on the páramo ecosystems [17], resulting in a significant landscape fragmentation [3]. Compared to the temperate zone, the tropical high-mountain sustains more population, and, thus, some parts have been submitted to local human pressures for centuries. Páramo ecosystems store a significant amount of carbon in their vegetation and soils [18], offering two key services in the current climate change scenario; carbon sequestration and water regulation. Since they are sensitive to disturbances, an understanding of the natural variability of their aquatic ecosystems could have significant implications for land management decisions. The protection of páramo areas in Colombia is relatively recent, mostly occurring in the late 1970s. There are still many lakes outside protected areas and, even in them, many watersheds have had some degree of intervention in the last 50 years. Therefore, we considered lakes both in protected and non-protected areas in our survey and planned to discuss whether protection measures are sufficient at present and which are the main threats under ongoing global change [19]. On the other hand, this work provides a baseline of the physical and chemical characteristics of these high mountain lakes. This information, in addition to being a reference point for monitoring in the scenario of global change, will allow the identification of páramo complexes that deserve greater attention in the definition of management policies and ecosystems that have a high value for their conservation. 2. Methods 2.1. Distribution of Colombian High-Mountain Lakes The Colombian high-mountain lakes are clustered in isolated páramo complexes distributed across the mountain ranges and covering 2,900,000 km2 (Figure 1). Using available 30-m resolution digital maps [20–23], we extracted layers of páramo complexes, protected areas, and lakes and intersected them to obtain lake inventories and statistics for each páramo complex. ArcGIS® software by Esri (Redlands, CA, USA) was used to perform all cartographic spatial analyses. 2.2. Eastern Cordillera Sampling and Analyses The Eastern Cordillera extends between approximately 1◦ 050 and 8◦ 400 N and is predominantly tectonic in origin [24]. The lithology predominantly dates back to Creta- ceous and Eocene periods, consisting of sedimentary rocks of continental or transitional marine-continental origin, with some Jurassic plutonic rocks and Quaternary modeling at high altitudes [25]. We sampled 51 lakes at the Eastern Cordillera >0.3 ha and above 3000 m a.s.l., selected to cover variation across altitude, geology, protection level, and land use. The lake survey was performed during the drought period (between January and March 2017), when radiation is the highest, and the effect of dilution of ions and nutrients caused by rainfall is reduced. The selected lakes were mainly located in areas with current protection status (86%). There is no detailed information on land use in the lake basins, but field observations indicate that among the lakes with protection status, 35% present some type of current or very recent affectation (dams, introduced trout, presence of cattle, and vestiges of agriculture in the basin). Lake depth was measured using an acoustic probe and GPS in points evenly dis- tributed in each lake. A minimum of 30 points was measured in the smaller lakes (<1 ha) and at least 100 points in the larger ones. The lake bathymetry was obtained using kriging interpolation. Lake area was calculated from orthophoto maps and total volume by trape- zoidal integration of sections: 0.2-m layers for lakes with depth <2 m, 0.5-m for 5 m depth, and 1-m for the deepest lakes. Water 2021, 13, 2175 4 of 16 The transparency of the water was measured using the Secchi disk depth (SD) and a photic index calculated as the ratio between the photic zone depth (i.e., SD × 2.3) and the maximum depth (Zmax ). Vertical profiles of temperature and oxygen were performed, and surface water was sampled in the central area of the lake for chemical analyses of alkalinity, Ca2+ , Mg2+ , Mn2+ , Na+ , K+ , Cl− , total phosphorus (TP), SO4 2− , PO4 3− , total organic carbon (TOC), total Kjeldahl nitrogen (TKN), NH4 + , NO3 − , NO2 − , and SiO2 . Chemical analyses were performed following standard methods for the examination of water and wastewater [26]. The main environmental gradients were assessed by principal component analysis (PCA). The environmental variables were transformed using Log10 or square root. Temperature, altitude and pH were not transformed because they already had a central distribution. PCA is an ordination technique that arranges environmental variables and samples in a space with a reduced number of dimensions. The PCA allows analysis of environmental gradients, correlations between variables and the distribution of the samples with respect to the set of gradients of all the variables. The set of variables that has a greater weight in one of the dimensions (axes) can be interpreted together as a response to a latent factor. 3. Results 3.1. Distribution of Páramo Lakes The analysis of digital maps showed that there are 3250 lakes in 28 out of 36 Colombian páramo complexes (Table 1), with 71% in protected areas. The highest number occurs in the Eastern Cordillera (44%), 39.6% in the Central Cordillera, and 13.7% in the Sierra Nevada de Santa Marta. The highest density of lakes occurs in Los Nevados, Sierra Nevada de Santa Marta, Las Hermosas, and Pisba complexes 0.003, 0.0029, 0.0025, and 0.0025 lakes ha−1 , respectively). The lake’s altitude ranges from 3000 to 5100 m.a.s.l., showing a bimodal distribution, with a primary mode at 3700 m and a secondary at 4300 m (Figure 2). The highest mode cor- responds mainly to the Cocuy, Sierra Nevada de Santa Marta, and Los Nevados complexes. Lake area ranges between 0.005 and 217 ha (Figure 2). The distribution is unimodal, with the mode slightly lower than 1 ha. The largest lakes mainly occur in three páramo complexes, Chiles-Cumbal, Sotará, and Cocuy. 3.2. Characteristics of Eastern Cordillera Lakes The altitudinal distribution of the lakes surveyed in the Eastern Cordillera followed the primary mode of the whole set of páramo lakes (Figure 3), whereas the lake area showed a larger median (~2 ha), with centered distribution and a tail of a few large lakes (Table 2, Figure 3). There is no spatial pattern in the distribution of lakes according to altitude or area (Figure 4). Maximum depth was usually <10 m, only few lakes showed >20 m. Likewise, the mean depth was low (median < 2 m). Consequently, the lake volume was relatively small compared to the lake surface. Morphometry differences between páramo complexes were irrelevant, except in the Sumapaz complex, where the lakes were exceptionally shallow (Figure 4). Water 2021, 13, 2175 5 of 16 Table 1. Páramo complexes of Colombia and lake distribution. C: Cordillera. ID Sector Total Páramo Protected Protection under National Number Number of Lakes in Area Covered by Páramo Complex Area (ha) Fraction (%) Park System (%) of Lakes Protected Areas Lakes (ha) 1 Almorzadero Eastern C. 156,552 0.4 128 301 2 Altiplano Cundiboyacense Eastern C. 4657 4 3 Belmira Western C. 10,622 100 1 1 0.3 4 Cerro Plateado Western C. 17,070 17 5 Chiles-Cumbal Nariño-Putumayo 63,223 15 3 247 6 Chilí-Barragán Central C. 80,708 29 78 11 267 7 Chingaza Eastern C. 109,956 73 44 124 103 245 8 Citará Western C. 11,233 56 1 1 2 9 Cruz Verde-Sumapaz Eastern C. 333,420 52 42 324 220 1095 10 Doña Juana-Chimayoy Nariño-Putumayo 69,263 50 35 28 10 65 11 El Duende Western C. 4454 34 12 Farallones de Cali Western C. 4545 100 100 13 Frontino-Urrao Western C. 13,921 85 8 2 2 7 14 Guanacas-Puracé-Coconucos Central C. 137,677 23 23 81 39 285 15 Guantiva-La Rusia Eastern C. 119,750 45 3 92 88 139 16 Guerrero Eastern C. 42,325 75 71 51 65 17 Iguaque-Merchán Eastern C. 28,311 46 18 15 12 17 18 Santurbán-Berlín Eastern C. 142,608 35 207 92 290 19 La Cocha-Patascoy Nariño-Putumayo 145,539 35 4 50 28 179 20 Las Hermosas Central C. 208,011 64 55 526 429 1437 21 Los Nevados Central C. 146,027 49 39 438 395 373 22 Los Picachos Eastern C. 23,725 88 56 1 1 2 23 Miraflores Eastern C. 19,928 85 24 Nevado del Huila-Moras Central C. 150,538 78 77 149 96 465 25 Paramillo Western C. 6744 100 100 2 2 6 26 Perijá Eastern C. 29,727 81 1 0.1 27 Pisba Eastern C. 106,243 27 27 265 140 253 28 Rabanal y río Bogotá Eastern C. 24,650 66 3 3 7 29 Sierra Nevada de Santa Marta Sierra Nevada 151,021 95 95 445 445 1600 30 Sierra Nevada del Cocuy Eastern C. 271,033 65 65 78 47 576 31 Sonsón Central C. 8707 40 32 Sotará Central C. 80,929 38 31 15 12 146 33 Tamá Eastern C. 16,339 75 53 2 3 34 Tatamá Western C. 10,930 100 100 35 Tota-Bijagual-Mamapacha Eastern C. 151,498 47 120 73 208 36 Yariguíes Eastern C. 4252 99 96 Total 2,906,137 50.8 33.3 3250 2303 8281 Water 2021, 13, x FOR PEER REVIEW 7 of 18 Water 2021, 13, 2175 6 of 16 Lake area ranges between 0.005 and 217 ha (Figure 2). The distribution is unimodal, with the mode slightly lower than 1 ha. The largest lakes mainly occur in three páramo complexes, Chiles‐Cumbal, Sotará, and Cocuy. Figure2.2.Area Figure Areaand andaltitude altitudedistributions distributionsof ofthe theColombian Colombianpáramo páramolakes. lakes. 3.2. Characteristics of Eastern Water transparency wasCordillera LakesSD 3.5 m). However, the photic zone extended low (average to bottom The altitudinal distribution of theof in 65% of the lakes because the shallowness lakes (Table surveyed in the 2). The Eastern lakes located Cordillera in followed the northern zone of the survey (Pisba and Guantiva-Russia páramos) showed the primary mode of the whole set of páramo lakes (Figure 3), whereas the lake area the highest water showed transparency (Figure a larger median (~24).ha), with centered distribution and a tail of a few large lakes Surface water3).temperature ◦ C. The average temperature difference (Table 2, Figure There is nowas usually spatial <15 in pattern the distribution of lakes according to between ◦ to 4 ◦showed altitude surface or area and bottom (Figure was 1.2 C, depth 4). Maximum but in was the deepest usuallylakes, it reached <10 m, only fewuplakes C. The oxygen saturation was high at surface (>78%) but highly variable at bottom, >20 m. Likewise, the mean depth was low (median < 2 m). Consequently, the lake volume ranging from oversaturation to anoxia (Table 2). Water 2021, 13, 2175 7 of 16 Table 2. Summary of the morphometrical and chemical characteristics of 51 páramo lakes in the Eastern Cordillera of the Colombian Andes. Coefficient Variable Minimum Maximum Median Mean of Variation Altitude (m a.s.l.) 3014 3830 3612 3580 0.05 Area (ha) 0.3 104.8 2.5 6.3 2.45 Maximum length (m) 77 1781 245 343 0.82 Volume (×103 m3 ) 1.0 13,303 38.6 438.6 4.28 Zmax (m) 0.4 44.3 6.3 8.2 0.97 Zmean (m) 0.1 17.0 1.8 2.8 1.18 Secchi disk (m) 0.3 8.4 3.2 3.5 0.64 Photic index 0.29 2.35 1.63 1.39 0.49 Conductivity (µS/cm) 2.0 72.0 5.0 10.7 1.26 Surface temperature (◦ C) 9.4 18.8 12.1 12.5 0.15 Vertical temperature gradient (◦ C) 0 4.2 1 1.21 0.94 O2 at surface (mg/L) 5 8.2 6.52 6.72 0.10 O2 at bottom (mg/L) 0 6.9 4.08 3.49 0.73 O2 saturation at surface (%) 78 117.1 99.9 99.0 0.10 O2 saturation at bottom (%) 0 110.6 56.6 50.5 0.74 pH 4.7 8.0 6.1 6.1 0.16 Alkalinity (µeq/L CaCO3 ) 6 848 30 100 1.56 SO4 2− (mg/L) 0.003 44.1 0.003 1.322 4.67 Ca2+ (mg/L) 0.17 7.82 0.62 1.38 1.38 Mg2+ (mg/L) 0.04 1.11 0.16 0.26 0.97 Na+ (mg/L) 0.37 1.73 0.66 0.73 0.33 Mn2+ (mg/L) 0.00 0.09 0.01 0.02 0.88 K+ (mg/L) 0.03 0.86 0.12 0.14 0.94 Total Fe (mg/L) 0.04 2.20 0.21 0.32 1.09 Cl− (mg/L) 0.03 3.73 0.18 0.34 2.03 Total organic carbon (mg/L) 2.6 14.0 6.2 6.3 0.40 Total Kjeldahl nitrogen (mg/L) 0.70 1.40 0.98 1.01 0.17 NH4 + (mg/L) 0.28 0.84 0.42 0.51 0.36 NO3 − (mg/L) 0.001 0.179 0.007 0.016 1.83 Total phosphorus (mg/L) 0.02 2.05 0.40 0.55 0.79 PO4 3− (mg/L) 0.003 1.125 0.014 0.164 1.77 Si (mg/L) 0.13 3.75 1.20 1.37 0.62 Alkalinity was low in most lakes (<200 µeq/L), except in a few with values ~1 meq/L. The dominant cation was Ca2+ but with relatively low values (Table 2). Consequently, lake waters showed low buffering capacity, and pH was commonly well below 7, but with only a few cases of extremely low values (<5). Total organic carbon was generally relatively high (~6 mg/L), although it did not correlate significantly with water acidity. TOC did not show a spatial pattern (Figure 4). Nitrogen concentration was low. The largely dominant dissolved inorganic form was NH4 + (Table 2), usually accounting for more than 50% of the TKN. TP and PO4 3− concen- trations were high in most of the investigated complexes, indicating general mesotrophic and eutrophic conditions, with a few hypereutrophic exceptions. TP presented higher values in the páramos of the southern area sampled (Cruz Verde-Sumapaz and Chingaza). The PCA summarized two latent factors of similar contribution to the water char- acteristics (Figure 5). One of the factors related to bedrock geology, which provides the major water chemicals and buffering capacity (i.e., pH, alkalinity, Ca2+ , Mg2+ , and SO4 2− ). The second factor encompassed many variables defining the trophic state. Phosphorus variables showed the highest contribution to this factor. Variation in both factors was relatively high in every páramo complex. Lakes in Pisba and Guantiva-La Rusia were less productive and tended to hold softer waters; Tota-Rabanal, the hardest waters; and Sumapaz and Guerrero were he lakes of the highest trophic state. ues in the páramos of the southern area sampled (Cruz Verde‐Sumapaz and Chingaza). The PCA summarized two latent factors of similar contribution to the water charac‐ teristics (Figure 5). One of the factors related to bedrock geology, which provides the ma‐ jor water chemicals and buffering capacity (i.e., pH, alkalinity, Ca2+, Mg2+, and SO42−). The second factor encompassed many variables defining the trophic state. Phosphorus varia‐ Water 2021, 13, 2175 bles showed the highest contribution to this factor. Variation in both factors was relatively 8 of 16 high in every páramo complex. Lakes in Pisba and Guantiva‐La Rusia were less produc‐ tive and tended to hold softer waters; Tota‐Rabanal, the hardest waters; and Sumapaz and Guerrero were he lakes of the highest trophic state. Water 2021, 13, x FOR PEER REVIEW 10 of 18 Figure 3. Morphometry of the 51 lakes studied in the Eastern Cordillera of the Colombian Andes. Figure 3. Morphometry of the 51 lakes studied in the Eastern Cordillera of the Colombian Andes. Figure Figure4.4.Spatial Spatialvariation variationof of geographical, geomorphological, geographical, physical geomorphological, and chemical physical variables and chemical of variables of the the 51 lakes sampled. 51 lakes sampled. Water 2021, 13, 2175 9 of 16 Water 2021, 13, x FOR PEER REVIEW 11 of 18 Figure Figure 5. 5. Biplot Biplot of of the the principal principal component component analyses analyses of of selected selected environmental variables. The environmental variables. The upper upper figure presents the relationship between the environmental variables. The direction of the figure presents the relationship between the environmental variables. The direction of the arrows arrows indicates indicates the the direction direction of the gradient of the gradient and and the the position position of of samples samples with with the the highest highest values values of of each each variable. The closer the arrows, the more correlated are the environmental variables. The second variable. The closer the arrows, the more correlated are the environmental variables. The second figure shows the position of each lake with respect to the environmental variables. The colors of the figure shows the position of each lake with respect to the environmental variables. The colors of the lakes correspond to the different páramo complexes studied. lakes correspond to the different páramo complexes studied. Water 2021, 13, 2175 10 of 16 4. Discussion 4.1. Distribution of Páramo Lakes The altitudinal distribution of páramo lakes responds to the glacial modeling of the Andes of Colombia. During the last glacial maximum, glaciers reached 4300 m a.s.l. [27,28], whereas the formation of lake basins at lower altitudes can be traced back to older cold periods [29]. These dual erosive glacial phases could be the explanation for the bimodal lake distribution found. The páramo complexes, where glaciers still exist today, are the ones with lakes at the higher altitudes, suggesting a more recent basin formation. These lakes show small and silted basins. Nonetheless, there is no significant general relationship between altitude and lake number or size. The complexes of Las Hermosas, Sierra Nevada de Santa Marta, and Los Nevados are of greater interest from the conservation perspective because of the higher number of lakes than in other complexes and the large proportion with protection status. In contrast, a small number of lakes are part of protected areas in the complexes of Cruz Verde-Sumapaz, Santurbán, and Pisba. 4.2. Eastern Cordillera Lake Characteristics Generally, glacier modeling in temperate mountain regions has caused relatively deep basins compared to the lake area, in contrast to ice modeling in subarctic areas [30]. The average depth of lakes in the Pyrenees is around 15–20 m [31]. Lakes in the Andean equatorial region tend to show lower average depth, e.g., around 10 m in the Cajas massive in Southern Ecuador [32]. Existing information indicates that the lake aspect ratio for the Colombian Andes tends to be closer to subarctic lakes than those of the temperate zone [15]. Our survey confirms this tendency. The reason may be related to an erosive process in a more open high-mountain landscape than in other ranges with narrower valleys. Unlike most alpine high-mountain watersheds, the páramo is covered by dense shrubby vegetation [33]. High air humidity throughout most of the year and average temperature values between 3–13 ◦ C [34,35] promote extensive marsh vegetation around the lakes, which are limited by an extensive belt of terrestrial–aquatic transition zone [35]. Consequently, the organic matter load is potentially high, explaining the consistently high TOC values in the lakes studied [36,37]. This feature also makes the páramo lakes more similar to tundra lakes than temperate alpine lakes. The Secchi disk values indicated that the transparency of the studied lakes in the Eastern Cordillera is very low compared to that in the temperate zone [30,38] and mountain lakes from Southern Ecuador [37]. However, despite the low water transparency, the light penetration is sufficient for macrophyte and algal growth at the bottom of most of the lakes due to the shallowness. This fact has major implications for the ecosystem as it increases the lake’s primary productivity [39,40]. The investigated lakes showed pH values mainly in the acidic range, with low buffer capacity because of the low cation concentration [41]. TOC and pH were not correlated (r = 0.1, p = 0.5, n = 60), indicating a low contribution of organic acids to acidity, which was primarily related to the inorganic ionic balance. All in all, the high diversity in TOC concentration among lakes merits further investigation about the TOC specific nature and the process determining its levels. Total nitrogen and phosphorus levels were significantly higher than those reported for high-mountain lakes in other areas of the world [42,43]. Ammonium accumulation at levels above nitrate is particularly remarkable, which may point to some limitations for nitrification or a continuous flux from deep layers and sediments. This issue, and the nitrogen cycle as a whole, considering atmospheric deposition, watershed loadings, and fixation, deserve further research in these lakes [44]. The proportion of PO4 3− respective to TP fluctuates strongly but is remarkably high (>20%) in many lakes. This feature and the relatively high nitrogen levels points to a light limitation in some of these lakes. Thus, there is a significant relationship between the ratio PO4 3− /TP and the TOC (r = 0.32, p = 0.02, n = 51). In any case, TP is high, indicating Water 2021, 13, x FOR PEER REVIEW 13 of 18 Water 2021, 13, 2175 11 of 16 PO43–/TP and the TOC (r = 0.32, p = 0.02, n = 51). In any case, TP is high, indicating meso‐ trophic to eutrophic mesotrophic conditions, to eutrophic in contrast conditions, to to in contrast thethe usual usualoligotrophic oligotrophiccharacter characterofof high‐ high- mountain mountain lakes [10]. On the one hand, the relatively low oxygen values at the bottom may lakes [10]. On the one hand, the relatively low oxygen values at the bottom may facilitate phosphorusdiffusion facilitate phosphorus diffusionfrom fromrecycling recyclinginin thethe sediments sediments [45]. [45]. OnOnthethe other other hand, hand, the the shallowness shallowness of lakes of the the lakes fosters fosters the relevance the relevance of theoflittoral the littoral and bottom and bottom primaryprimary pro‐ producers ducers and theand the influence influence of thycoplankton of thycoplankton in openinwaters open waters [46,47]. [46,47]. Although Although the charac‐ the characteristics teristics pointed here refer to the páramo lakes of the pointed here refer to the páramo lakes of the Eastern Cordillera, there is no reasonno Eastern Cordillera, there is to reason expect to expect that they will not apply to the whole set of páramo that they will not apply to the whole set of páramo lakes in Colombia. lakes in Colombia. 4.3. Páramo Páramo Lakes in the Context of Global Change The main factors associated with global change that could affect the páramo lakes are the increase in air temperature, changes in the rainfall regime, changes in land use, and atmospheric transport atmospheric transport of pollutants. TheseThese processes processes have been widely documented in remote mountain mountainlakes lakes[48–50]. [48–50].The Thepotential potential impacts impactsof of these processes these range processes fromfrom range in-lake in‐ moderate lake changes moderate (e.g.,(e.g., changes water column water columnstability, oxygen stability, demand) oxygen to large demand) watershed to large and watershed external and loading external modifications loading modifications(e.g.,(e.g., water level,level, water organic loads, organic pollutant loads, accumulation), pollutant accumula‐ eventually leading to marked changes in communities and food webs (Figure tion), eventually leading to marked changes in communities and food webs (Figure 6). 6). Global Environmental Change Páramo lakes processes processes potentially impacted Thermal stratification and Increase in temperature hypoxia during the dry season Local rainfall variability Water level variability Changes in land use Atmospheric transport of pollutants Primary productivity Siltation Accumulation of pollutants Changes in food web Figure Figure 6. 6. Conceptual Conceptualsketch ofof sketch thethe potential effects potential of global effects change of global on páramo change lakeslakes on páramo (Arrows indi‐ (Arrows cate drivers (left) enhancement of the processes (right). indicate drivers (left) enhancement of the processes (right). Studies Studies have have projected projected an an increase increase in in air temperature of air temperature between 33 and of between and 44 ◦°C in the C in the Andes high mountains Andes high mountains[51],[51],resulting resultingininsome someofofthese these lakes lakes possibly possibly exceeding exceeding 20 20C°C ◦ dur‐ during ing periods periods of high of high radiation. radiation. HigherHigher temperatures temperatures will will accelerate accelerate organism organism metabolism metabolism and, and, consequently, biogeochemical processes. Respiration is more sensitive consequently, biogeochemical processes. Respiration is more sensitive than photosynthesis than photo‐ synthesis to temperature, to temperature, but higherbut higher may recycling recycling resultmay in aresult higherintrophic a higher trophic state of thestate lakesof[52]. the lakes [52]. Higher biomass and metabolism will increase oxygen Higher biomass and metabolism will increase oxygen demand [53], and warmer waters demand [53], and warmer waters and stronger and stronger stratification maystratification may limit limit the supply [54];the supply thus, [54]; thus, the lakes may the lakesmore become may similar to tropical lakes of lower altitudes [55]. Oxygen values in hypolimnion already tend to be low in the lakes studied, so an increase in hypoxia will enhance phosphorus Water 2021, 13, 2175 12 of 16 mobilization. Lakes that currently have the highest phosphorus values could experience significant water quality deterioration in the coming decades. This is the case of lakes near the main urban centers of Colombia. These systems, due to their proximity to the city of Bogotá, presented a history of high affectation during the last two centuries and, therefore, could have a low capacity to mitigate the impact of the increase in temperature. On the other hand, during the dry season all these effects can be enhanced by substantially increasing the metabolism of the lakes. Since our study is based on a sampling carried out during the dry period, the chemical composition of the lakes in future scenarios, with longer periods of drought, could be similar to the more enriched lakes that were observed. During the rainy season, dilution could reduce the concentration of nutrients, but could increase the contribution of organic matter from the basin. Climate change may also affect rainfall seasonality, with more extended and more frequent periods of drought expected [1]. Our results show that the lakes of the Eastern Cordillera are very shallow ecosystems, so that longer periods of drought will have a great impact. Even though there are a high number of small bodies of water, the shallow depth determines that the water storage capacity will be low. Aquatic plant communities, especially those that inhabit the terrestrial–aquatic transition and submerged macrophytes without rapid regeneration, will be quickly affected by these changes [56,57]. Most of the lakes studied showed a photic layer that reaches the sediment, so the reduction in depth could increase the role of algal productivity in the deeper lakes, while the shallower lakes could suffer a progressive invasion of littoral plants. More importantly, páramo peatlands may experience periods of high release of organic material to the lakes, enhancing lake metabolism and oxygen demand. The shifting conditions may last for long periods, and human land use in the watersheds may enhance the processes. The long-range transport of pollutants to these lakes, another component of global change, is largely unknown [15]. The lake watershed protection should reduce undesirable synergies between global change and local land use and provide better stewardship of any unavoidable shift produced by climate transitions [58]. 4.4. Páramo Lake Conservation The results of the lake chemical analyses did not show a pattern, from which it could be concluded that a low lake trophic state is related to protection status (Figure 7). Despite the imbalance in the number of lakes considered between conserved and non-conserved areas, the high variability and the high concentration of TP and TOC in lakes of some National Parks such as Chingaza and Sumapaz suggests that this result shows more the degree of affectation suffered by the different complexes than the current conservation status. The System of Protected Areas in Colombia is relatively recent. Páramo protection is mainly under the jurisdiction of the national park system (33%), and smaller areas are managed by municipal or private regional reserves (12%). The majority of the páramo ecosystems were declared protected in 1977 as part of the National Natural Parks System of Colombia (decree 2811–1974 of the Republic of Colombia, 1975). Many of these areas previously had agricultural, livestock, and mining activities. Currently, most of them still have some type of agricultural management with low impact, such as extensive livestock. Surveying the past is possible with paleolimnological techniques [59]. The study of lake sediments can evaluate the effectiveness of the watershed conservation status and define reference conditions to manage human land use and climate interaction (e.g., land erosion and siltation of the lakes). Strategic planning should also consider increasing the protected areas. Páramo ecosys- tems are a unique natural heritage for biodiversity. Fish introduction is one of the leading food web alterations in high-mountain lakes worldwide [60], including trout in the An- dean tropical lakes [61]. Protection should reduce trout spreading and other undesirable fish species. Furthermore, if climate change modifies water availability, hydrological in- terventions (e.g., building dams, diverting streams) could be a pressure that prevention and planning should anticipate. The results presented here constitute a baseline for the Water 2021, 13, x FOR PEER REVIEW 15 of 18 Water 2021, 13, 2175 13 of 16 interventions (e.g., building dams, diverting streams) could be a pressure that prevention and planning should anticipate. The results presented here constitute a baseline for the definition definitionof ofthe thetrophic trophicstatus statusofofthe thelakes lakesand andforfortheir theirmonitoring. monitoring.The Theshallow shallowdepth depth and andthe thehigh highcontent contentofoforganic organicmatter matterand andnutrients nutrientsofofmost mostecosystems ecosystemssuggest suggestthat thatthey they are ecosystems that require specific actions even in protected areas. The total are ecosystems that require specific actions even in protected areas. The total eliminationelimination of livestock, the control of the introduction of trout and the assessment of the real potential of livestock, the control of the introduction of trout and the assessment of the real potential of some lakeslakes of some to provide waterwater to provide to local to communities are actions local communities that should are actions be implemented that should be imple‐ urgently. The regular mented urgently. Themeasurement of the water regular measurement transparency, of the TP, TKN TP, water transparency, andTKNthe oxygen and the concentration in the hypolimnion oxygen concentration would allow in the hypolimnion a response would from these allow a response ecosystems from to these these ecosystems actions to theseduring actions the progression during of climateofchange. the progression climate change. Figure7.7.Boxplot Figure Boxplotofofthe thesecond secondprincipal components principal components (PCA (PCA2) showed in Figure 2) showed 5, grouping in Figure lakeslakes 5, grouping by by non‐protected non-protected (n = (n 7) =and 7) and protected protected areasareas (n = (n = 44). 44). DotsDots represent represent outliers. outliers. 5.5.Conclusions Conclusions The Thepáramo páramo lakes of Colombia lakes of Colombiaare arerelatively relativelysmall smallandand fairly fairly shallow shallow lakes lakes withwith lim‐ limnological characteristics (e.g., low buffering capacity, high organic content, high nological characteristics (e.g., low buffering capacity, high organic content, high nutrient nutrient concentration, concentration,and andlow lowoxygen) oxygen)thatthatmake makethem themextremely extremely sensitive to to sensitive local environmental local environmen‐ pressures in their tal pressures watersheds in their watershedsandandduring ongoing during ongoingclimate climatechange. change.It It becomes becomesan anurgent urgent matter matter to increase the protected area and focus future research on assessing whetherthe to increase the protected area and focus future research on assessing whether the current management of the watersheds is enough to guarantee a good ecological status current management of the watersheds is enough to guarantee a good ecological status and respond to challenging shifting global conditions. and respond to challenging shifting global conditions. Author Contributions: Conceptualization, C.A.R.-R., A.Z. and J.C.; methodology, A.Z., C.A.R.- Author Contributions: Conceptualization, C.A.R.‐R., A.Z. and J.C.; methodology, A.Z., C.A.R.‐R.; R.; D.V., C.L.M.-L. and M.M.-R.; data analysis: A.Z., C.A.R.-R.; D.V., C.L.M.-L., M.M.-R. and J.C.; D.V., C.L.M.‐L. and M.M.‐R.; data analysis: A.Z., C.A.R.‐R.; D.V., C.L.M.‐L., M.M.‐R. and J.C.; writ‐ writing—original draft preparation, A.Z., C.A.R.-R., D.V., C.L.M.-L. and M.M.-R.; writing—review ing—original draft preparation, A.Z., C.A.R.‐R., D.V., C.L.M.‐L. and M.M.‐R.; writing—review and and editing, A.Z., C.A.R.-R. and J.C. All authors have read and agreed to the published version of editing, A.Z., C.A.R.‐R. and J.C. All authors have read and agreed to the published version of the the manuscript. manuscript Funding: This study was funded by Ministerio de Ciencia, Tecnología e Innovación of Colombia (Col- Funding: This study was funded by Ministerio de Ciencia, Tecnología e Innovación of Colombia (Col‐ ciencias ciencias50000-050-2016) 50000‐050‐2016)and andPontificia PontificiaUniversidad UniversidadJaveriana Javeriana(IDPPTA (IDPPTA6789 6789and andID IDPPTA PPTA7066). 7066).C. C. Muñoz-López Muñoz‐López was supported by a PhD scholarship MinCiencias Colciencias‐Colfuturo (No.779 was supported by a PhD scholarship MinCiencias Colciencias-Colfuturo (No. 779 2017‐RegionesBoyacá). 2017-Regiones Boyacá). Institutional InstitutionalReview ReviewBoard Statement:Not BoardStatement: Notapplicable. applicable. Informed InformedConsent Statement:Not ConsentStatement: Notapplicable. applicable. Acknowledgments:Thanks Acknowledgments: ThankstotoParques ParquesNacionales NacionalesNaturales NaturalesdedeColombia Colombia(Resolución (ResoluciónNo. No.141-241016) 141‐241016) and and to the staff of the PNN Chingaza, PNN Sumapaz, SFF Guanentá Alto Río Fonce,SFF to the staff of the PNN Chingaza, PNN Sumapaz, SFF Guanentá Alto Río Fonce, SFFlguaque, lguaque, and andPNN PNNPisba, forfor Pisba, their invaluable their helphelp invaluable during the fieldwork. during Thanks the fieldwork. to theto Thanks project fieldwork the project team: fieldwork Y. Caleño, D. Castillo, M. Guerrero, J. Jimenez, and L. Garzón for their invaluable help exploring the mountains lakes. Water 2021, 13, 2175 14 of 16 Conflicts of Interest: The authors declare no conflict of interest. References 1. Herzog, S.; Martínez, R.; Jørgensen, P.; Tiessen, H. (Eds.) 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