Introduction

Wetlands, especially in tropical ecosystems have received much attention in recent times because of the increased knowledge about their economic values and benefits, and also consequences of many anthropogenic activities. By definition “wetlands are wide ranging aquatic habitats including marsh, fen, peat land/ open water, flowing water (rivers and streams) or static (lakes and ponds), it could be fresh, brackish or salt water, artificial or natural, not exceeding 1-2 m depth” (Boon and Pringle, 2009). Wetland status is characterised by presence of macrophytes, chemical and ionic concentrations, organic matter in water, sediment deposition rate and water depth (Brown et al., 2009). The non-stratified photic zone enhances the growth of photosynthetic organisms particularly benthic and planktonic algae. Wetlands helps in mitigating global warming by aiding as carbon sink with the CO2 sequestration rate in water logged wetlands (2.23-3.71 metric tons/acre/year) being higher than forests (0.05-3.9) (Bernal and Mitsch, 2012). However, wetland economic services often borders between ecological function and destruction which makes it more fragile either due to natural (salinity, floods, etc.) or human disturbance (defecation, effluents, agricultural fields, eutrophication, etc.) (discussed in later part).

Merely 1.3% of earth surface is occupied by inland water bodies comprising wetlands, rivers and streams (Spellman, 2008). Recent conferences and wetland community meetings established policy and guidelines to protect wetland ecosystems across countries in Asia. However, continued changes in developing settlements since 1980’s reflects prolific new and very large urban populations and built-up regions. This not only influences wetland geomorphology but also the essential biodiversity components. With the increased population and followed urbanization, a decline in environmental quality and degradation of surrounding ecosystems amplified spontaneously. Major shift was noticed from predominantly rural to urban, wetlands to water tanks and recreation centres which also lead to climate variability, habitat fragmentation and critical loss threatening biodiversity and extinction (Adriaensen et al., 2003).
Wetlands in peninsular India are mostly formed by the formation of tributaries of large rivers and streams, man-made ancient lakes and ponds and formation of valleys, to be found in Western Ghats and Deccan plateau regions. Though some of these wetlands are considered as Ramsar sites, many of the other man-made wetlands are significant that uphold large population of migratory birds, amphibians, microbial flora and macro-invertebrates. Efficient monitoring of wetlands should include consideration of habitation, benthic biodiversity, sedimentation and flow rates and nutrients (forms of nitrogen and phosphorous) balance through sewage network diversion. Man-made wetlands located in urban centres are exposed to changes due to sewage inflow, over fishing, human destructions and seasonal changes. It is therefore very important to recognize geomorphological and biological features of each wetland for preservation and restoration from being destroyed.

Wetlands in Bangalore (spatial extent 190 sq.km.) located in Karnataka are well known for hundreds of man-made wetlands from centuries with rich flora and fauna. ~262 wetlands were constructed in 16th century to meet domestic and agricultural needs of the city which are now anthropogenic degraded and have been reduced to less than 80 and named as tanks (Lakshman Rau, 1986). A  sharp decline of 58% in Bangalore attributes to intense urbanization processes, evident from a 46% increase in built-up area from 1973 to 2007 (Ramachandra and Uttam Kumar, 2008). Mora than a decade studies from Ramachandra and Kiran,1999; Ramachandra et al., 2005; Ramachandra et al., 2013 showed that even though wetlands are studied, there has been a sustained effort to develop database with physical, chemical, morphological and biological conditions of wetlands. Few of the already restored wetlands showed failure to restore and maintain clean for not more than 3 years which needs immediate attention by government bodies. An attempt was made in the current study to carry out environmental auditing of Bangalore wetlands to understand the ecological status and recommend guidelines for biological restoration of wetlands. Some of the wetland features such as size, catchment area, depth, location, type of anthropogenic activities, eutrophication, etc. were recorded. 

 
Methods

45 wetlands with size ranged from 1.5 to 200 hectares, located within the Greater Bangalore were selected randomly. These wetlands are being used for various purposes (Irrigation, recreational and other activities).  Water samples from more than 4 locations in each wetland was selected so as to cover different sampling points and analysed for physical and chemical analysis. Location of sampling sites was based on the preliminary survey on sewage inflow and outflow sites along with non-point sources so as to provide representative sample for marked change in water quality. Details (including sketch maps) of the site location were compiled from the Survey of India topographical maps (1:50,000) that included geographical co-ordinates (Latitude, Longitude, altitude) and name of village/watershed. Local human disturbances at sampling sites such as road construction waste, solid waste disposal site, washing waste were collected during field visits. Three replicates of water samples were collected from inlets, outlets and other sites (such as center) to observe and to understand the water quality variations at the regional scale. Onsite variables like pH, electric conductivity (EC), salinity (SAL), total dissolved solids (TDS), water temperature (WT), air temperature (AT) and dissolved oxygen (DO) were measured using meters (Extech pH/conductivity EC500). The samples were carried to laboratory on the same day of sampling and stored at 4oC for further chemical analyses. Methods mentioned in American public health association (APHA, 2010) was followed for nitrates (N), inorganic phosphates/or phosphorous (P), total hardness (TH), calcium hardness (CaH), magnesium hardness (MgH), chlorides (CHL), alkalinity (ALK), chemical oxygen demand (COD), biological oxygen demand (BOD), sodium (Na) and Potassium (K).