Springshed Nutrient Loading, Transport and Transformations

A discussion of the effects of nutrients on springs biota and ecosystems of necessity requires an understanding of the manner and mechanism of nutrient delivery. Moreover, as evidence accumulates for particular consequences of nutrient and contaminant loading, understanding how those loads can be attenuated is crucial. This chapter focuses on nutrient loading to springsheds, with an emphasis on processes of transport and attenuation that are germane to their delivery to springs. It starts by describing the flowpaths and hydrogeology of Florida’s karst systems, with an emphasis on intrinsic vulnerabilities to nitrogen loading in particular. A discussion about land use and land cover change, and the sources of nutrient pollution, follows. Nitrogen loading is by far the most well studied spring contaminant, but examination of other changes that have occurred in springs, including changes in flow, dissolved oxygen, hardness and conductivity that have been documented within and across springs is informative. Attention is also set on the future of nutrient loading, including the potential saturation of phosphorus along subsurface flowpaths, with important implications for the timeline of nutrient load reduction. Finally, the state of our understanding of springsheds as closed systems of water and solutes is examined, with an emphasis on areas of uncertainty that are relevant questions for future research.