Atmospheric Deposition of Nutrients Shifts Carbon Capture and Storage Trends in Freshwater Tropical Lakes in India

A connective organized framework for integrated water resource management is a critical challenge the human societies are facing both on regional and global scales. Recent studies have shown the need for operational connection among water resource managers, watershed managers and aquatic ecosystem managers (Lin, 2012). Despite apparent differences, these three management domains are scientifically and socially interdependent. Climate change regulation and ecosystem/habitat degradation have signaled growing constraints for managing ecosystem-human interface. Further, despite operational interdependence, the three main ecosystem domains; air, land and water are studied in relative isolation. Coupled with the biogeochemical cycles of nitrogen (N) and phosphorus (P), carbon (C) has become central to understand cross-domain ecosystem linkages and the effects of human perturbations therein. The concern for carbon enrichment of inland waters has focused on two major issues: the nutrient-driven increase in autochthonous C-pool leading to changes in water quality (Monteith et al., 2007; Pandey and Pandey, 2013); and, enhanced allochthonous C export and associated shifts in carbon balance of the water body (Cole et al., 2007; Buffam et al., 2011; Pandey and Pandey, 2013; Pandey et al., 2014). Regional scale studies have shown the potential role of hydrological transport for landscape C budget and have highlighted the importance of interaction of different landscape elements (Buffam et al., 2011). Sensitivity of surface waters, whether as a net C sink or source, and their vulnerability to changing atmospheric deposition chemistry differ at a range of temporal and spatial scales and may provide important cue for regional C budget. Studies on impact of atmospheric deposition of nutrients on lakes have been confined mainly to temperate and subarctic regions (Weyhenmeyer and Karlsson, 2009). To date, no data so for is available from Indian tropics addressing explicitly the human-induced changes in atmosphere-land-water transfer and subsequent influence on C balance of freshwater lakes. Recent studies have indicated that Indian surface waters are receiving increasingly high input of atmospherically deposited (AD) nutrients (Pandey and Pandey, 2009; 2013; Pandey et al., 2013; 2014). The AD-nutrients may alter ecosystem attributes via direct deposition to water surface and via deposition on land surface and subsequent modifications in the catchment (Whitall et al., 2003; Pandey, 2011). Air-driven nutrients delivered directly on water surfaces enhance phytoplankton blooming (Bergstrom et al., 2008) while atmospheric input in catchment may alter quality of organic matter and subsequent runoff reaching to waterways (Wedin and Tilman, 1996; Pandey, 2011). Changes in soil organic matter (SOM) solubility and the rate of microbial production or consumption of water soluble organic carbon (WSOC) from SOM in uppermost carbon rich soil horizon (Kalbitz et al., 2000) may be an important driver of DOC in receiving waters (Pandey and Pandey, 2013; Pandey et al., 2014).