An Index of Limnological Conditions for Urban Wetlands of Bogotã¡ City, Colombia
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Ecological Indicators 10 (2010) 848–856 Contents lists available at ScienceDirect Ecological Indicators journal homepage: www.elsevier.com/locate/ecolind An index of limnological conditions for urban wetlands of Bogota´ city, Colombia Gabriel Pinilla * Biology Department, National University of Colombia, Colombia ARTICLE INFO ABSTRACT Article history: The urban wetlands of Bogota´ are ecosystems of great importance, yet they are deteriorating. The state of Received 20 September 2009 deterioration must be evaluated in order to develop new methods of ecosystem monitoring and Received in revised form 5 January 2010 conservation. Here we describe the development of an index to assess the ecological health of five urban Accepted 17 January 2010 wetlands and one rural wetland from limnological data. The field phase of this study took place in November 2007 (rainy season) and February 2008 (dry season). Physical and chemical variables of the Keywords: wetland ecosystems (temperature, dissolved oxygen, pH, conductivity, hardness, chlorides, ammonia, Urban wetlands nitrites, nitrates, orthophosphates, and biological oxygen demand) were measured and samples of Multi-metric index phytoplankton, periphyton, macroinvertebrates, and aquatic plants (macrophytes) were collected. The Limnological condition Colombia indices developed (biotic indices of communities: BI, and limnological conditions index: LICOI) allow classification of wetlands into three categories: those that have ‘‘acceptable limnological conditions’’ (Meridor, Jaboque and Guaimaral), those with ‘‘regular limnological conditions’’ (Santa Marı´a del Lago, Juan Amarillo) and those with ‘‘poor limnological conditions’’ (Tibanica). None of the environments studied fit a potential fourth category of ‘‘best limnological conditions.’’ The LICOI is a management tool that can be used to assess changes in wetlands after positive actions (restoration, cleaning, hydraulic management), or negative impacts (depletion, alien species, pollution). It also could allow regular monitoring of wetland evolution and serve as a basis for the development of indices measuring the ecological status of other aquatic environments in Colombia. ß 2010 Elsevier Ltd. All rights reserved. 1. Introduction group (e.g., fish, Harris and Silveira, 1999; periphyton, Hill et al., 2003;macrophytes,Reiss, 2006; vascular plants, Miller et al., 2006; In the 1970s and 1980s, evaluation of global aquatic systems was diatoms, Lane and Brown, 2007; macroinvertebrates, Smith et al., based on individual information about each variable (e.g., physical, 2007). For the study of Colombian ecosystems, there is a chemical, or biological) measured in the body of water (Tolkamp and macroinvertebrate index, adapted from a European index (Rolda´n, Gardeniers, 1988). Later, in the 1990s, these variables were 2003), and some exercises to assign primary bioindication values for integrated, and indices of physicochemical quality (Kung et al., macroinvertebrate families (Riss et al., 2002a, 2002b). Riverine 1992; Dojlido et al., 1994; Van Helmond and Breukel, 1997)and diatoms were also used as bioindicators to assess the water quality biological integrity appeared (Jackon and Davis, 1994; Barbour et al., of Andean rivers (Dı´az and Rivera, 2004). However, there are no 1999; Barbour et al., 2000; Pinilla, 2000). More recently, develop- indices of limnological conditions for any aquatic ecosystems in ments of indices have included both abiotic and biological factors in Colombia that were developed integrating both physicochemical the same equation. To date, there are an appreciable number of such and biological indices. metrics. These indices vary from simple structures (e.g., indices of Most limnological indices that have been developed are ideal trophic classification and water-quality assessment, Vollenweider for use in temperate regions, and are not appropriate for assessing et al., 1998; Viaroli and Christian, 2003; Sa´nchez et al., 2007), to tropical ecosystems. Rivers are the best-studied ecosystems complex multi-metrics that take into account physical and internationally, and macroinvertebrates have the most metrics. biological factors (e.g., indices of lotic or lentic conditions, Schultz, There are few indices for wetlands and metrics for biological 2001; Hu et al., 2006; Brazner et al., 2007). Between these two groups such as bacteria, protozoa, and zooplankton have only extremes lie a variety of indices that focus on a particular biological recently been developed. The wetlands of Bogota´ are ecosystems of great importance, largely due to their myriad ecological and social functions. At * Corresponding author. Tel.: +57 1 3165000; fax: +57 1 3165310. present, there are eleven main wetlands in Bogota´ city: Capellanı´a E-mail addresses: [email protected], [email protected]. (18 Ha), La Vaca (40 Ha), Techo (3 Ha), Tibanica (10 Ha), El Burro 1470-160X/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecolind.2010.01.006 G. Pinilla / Ecological Indicators 10 (2010) 848–856 849 (31 Ha), Co´ rdoba (40 Ha), Jaboque (147 Ha) Guymaral-Torca where n is the number of chemical variables, N is the number of (73 Ha), La Conejera (60 Ha), Juan Amarillo or Tibabuyes (40 Ha), stations, and i represents the stations where the taxon was and Santa Maria del Lago (4 Ha) (Moreno et al., 2005). The first five collected. The biotic index (BI) of a given community is calculated of these, which have suffered the greatest deterioration, exist as: within the dry zone of the city (Herrera et al., 2004). In total, the Xn wetland area within the urban district is approximately 500 Ha. As ðTPVÞ mentioned, these aquatic environments are worsening (Van der BI ¼ i¼1 (3) Hammen et al., 2008) and improved methods for assessing their n ongoing deterioration are needed for purposes of monitoring and conservation. In this paper, an index of limnological conditions where n is the number of species or taxa in a community and TPV is (LICOI) is proposed for assessing the urban wetlands of Bogota´,to the pollution value of each taxon, i. serve as a tool for characterization and management of these The LICOI is calculated as the weighted sum of the BI of the ecosystems. various communities. The weighting factor was established based on the regressions obtained in the correlation coefficients. Thus, 2. Materials and methods the BIs of phytoplankton (BIP), periphytic diatoms (BID), and macrophytes (BIM) were each multiplied by 0.3 (because all of 2.1. Location of wetlands and sampling these BI obtained the highest correlation coefficients), and the BI of macroinvertebrates (BII, which has lower correlation coefficient) The wetlands studied belong to the Bogota´ River Basin. Based on was multiplied by 0.1 (the sum of the weights is 1). The BI values secondary information and preliminary assessment, five of these were converted to percentages (100% is the highest possible BI for wetlands with diverse degrees of preservation and deterioration each community) and subtracted from 100 to obtain estimates were selected for study (Guaimaral, Jaboque, Tibanica, Santa Marı´a directly proportional to the degree of conservation and the LICOI. del Lago, Juan Amarillo). A small rural wetland (Meridor 9.6 Ha, Thus, the LICOI is high for limnological systems in good condition municipality of Tenjo) was also included as a reference system due (well-preserved ecological functions) and low for limnological its low degree of human intervention. These wetlands are environments in poor condition (impaired ecological functions). The equation for calculating the LICOI is as follows: relatively close, with a difference of altitude not exceeding 125 m (2451–2576 masl). Each wetland was sampled twice, once LICOI ¼ 100 À %BIP 0:3 þ 100 À %BID 0:3 during the November 2007 rainy season and once during the February 2008 dry season. For each sample period, three sites in each wetland were selected to measure the following physical and þ 100 À %BII 0:1 þ 100 À %BIM 0:3 (4) chemical variables: Secchi transparency, temperature, dissolved oxygen, pH, conductivity, hardness, chlorides, ammonia, nitrites, where %BIP is the biotic index of phytoplankton, %BID is the biotic nitrates, orthophosphates, and biological oxygen demand (BOD5). index of periphytic diatoms, %BII is the biotic index of aquatic Communities of phytoplankton, periphytic diatoms, macroinver- macroinvertebrates, and %BIM is the biotic index of aquatic tebrates, and aquatic plants (macrophytes) were collected from the macrophytes, all expressed in percentages. same three sites for each wetland and assessed. In all cases, Four categories for the wetlands of Bogota´, based on %BI and standard methods proposed by APHA (1995), Wetzel and Likens LICOI values, were established using quartiles. In order to confirm (1991), and Rueda (2002) were followed. the significance of index calculations, correlations were identified between the environmental conditions, expressed as PI values, and 2.2. Development of Indices the BI and LICOI values. Similarly, regression graphs between indices and PI values were drawn, using the logarithmic equation, The pollution index (PI) was computed, integrating all Y = a log (X)+b. physicochemical variables, using the methodology proposed by Jiang and Shen (2005) and Jiang (2006). The variables described are 3. Results those for which Colombian law has established allowable limits for drinking water, and which have a direct relationship with the 3.1. Physical and chemical environment ecology