Assessing the relationship between rainfall and nutrient concentrations in the coastal Everglades

Printer-friendly version

The FCE LTER Legacies working group is focused on identifying the factors that affect the movement and location of the ecotone in the coastal Everglades. One of the ways to address such an objective is to test whether a relationship exists between nutrient concentrations and rainfall in the near-shore waters off of Florida Bay, Whitewater Bay, and the Ten Thousand Islands. A test of this relationship was conducted at seventy-five long-term monitoring sites located among the three regions. Rainfall data was gathered from the SFWMD DBHydro database while nutrient data was obtained from FIU’s SERC water quality monitoring site network. ArcGIS is used to interpolate rainfall surfaces for the study area. This allows for determining rainfall amounts for each of the water quality sites for the time period from 1991 through 2008. Once the rainfall and nutrient data is tabulated for each water quality site, cumulative sum plots are graphed showing nutrient concentrations versus monthly rainfall amounts. The cumulative sum plots are intended to illustrate possible thresholds of rainfall amounts that result in detectable changes in nutrient concentrations. Lastly, the cumulative sum plots are compared with each other in order to observe similarities and differences between sites that may correspond to potential geographic delineations. The results of these tests indicate that the rainfall thresholds vary among the various water quality sites across the three regions of the study area.