Although inland water bodies occupy a small fraction of the earth’s surface, they play a major role in the global carbon (C) cycle1. The predominant terrestrial carbon input to most lakes and reservoirs is dissolved carbon (DC), followed by particulate carbon, and the proportion of inputs varies with lake location and hydrology2. The dominant form of aquatic carbon in some temperate regions, high northern latitudes and boreal forests in a carbonate terrain is dissolved inorganic carbon (DIC)3,4. In contrast, dissolved organic carbon (DOC) is the dominant form in humid tropical areas and in noncarbonate boreal forests2. Spatial DC measurements are useful for understanding carbon sources and cycling in aquatic systems, and it is dependent on an array of factors2,5,6, e.g., catchment soil and landscape, hydrology, trophic status and anthropogenic discharge6,7,8. In general, DC in aquatic systems mainly comes from decomposition of organic matter, i.e., plants in the catchment and algae and macrophytes within the water body, and the metabolic secretion of phytoplankton and microbes. However, inland waters in China, particularly those situated in the Northeast, East and South regions, are severely polluted with high nutrients concentration and eutrophic status, which also changes the concentration and constituent of DOC from algae6,9. In addition, anthropogenic discharge also provides a large volume of dissolved organic matter into lakes and reservoirs in these regions10,11.
Numerous investigations have been carried out to examine the variations in DC in inland waters5,12,13,14,15,16,17. However, investigations of DC patterns are imbalanced with respect to geography2,5. Lakes in Europe, particularly in Scandinavian countries where lakes are more abundant, have been intensively investigated12,18. Likewise, lakes in the USA, Canada and Japan have also been extensively examined for DC spatiotemporal variation19,20,21. Comparatively, fewer investigations have been undertaken to investigate DC variation for inland waters in China17.
Due to differences in climate across the country, and different land-use types surrounding water bodies, China contains a large number of inland water bodies which have a wide variation in water quality4,22,23,24. It was estimated that by 2002, China contained 85,288 reservoirs with a surface water area of 23,000 km2, and almost 2700 lakes (area >1 km2) with a total area of 81,414.6 km2 25,26, with saline lakes accounting for about half of the lake area27. Previous investigations have also indicated that DC concentration significantly differs between fresh water and saline water bodies16,28. The trophic status of inland water bodies in China ranges from oligotrophic to hypereutrophic. Previous investigations indicated that lakes with eutrophic status in various climatic regions may exert a strong impact on DC of inland waters6,9,20. Thus, a systematic examination of DC characteristics in inland water bodies in China is urgently needed.
The objective of this study is to describe a DC data set collected by field surveys undertaken in lakes and reservoirs across mainland China. Our investigation provides a record of DOC and DIC measurements in 288 lakes across five lake regions, and 141 large reservoirs spanning complex topography, landscape, hydrology, eutrophic status, and salinity. Finally, we discuss DC concentrations for lakes and reservoirs with respect to the impact of eutrophic status and a saline gradient in different lake regions in China. We also provide full details for data access.
Source: Ecology - nature.com
