Predicting the Effects of Sea-Level Rise on the Ecology of Spring Creek in the Coastal Woodville Karst Plain of North Florida
Project Chief: Kim H. Haag
Cooperator: Florida Department of Environmental Protection, Florida Geological Survey (FGS)
Period of Project: October 2009 – September 2011
Problem Statement
Figure 1. Floating diatom sampler near a spring outflow along Spring Creek, FL.
The Woodville Karst Plain is an important coastal watershed for the environmental protection and resource conservation of northwest Florida. Human activities have altered the hydrologic system and caused nutrient enrichment, resulting in blooms of nuisance algae (hydrilla) and declines in the apple snail population and associated avian populations of limpkins, which feed on them. Future impacts to the ecosystem related to sea-level rise and salinity changes are also anticipated. To better manage this watershed, a comprehensive understanding of this complex system is needed. Previous research efforts have focused on the hydrogeological characterization of the watershed, and understanding the dynamics of groundwater and surface-water interactions. In order to achieve a more comprehensive understanding of the system, a multidisciplinary approach is needed, including an evaluation of biological conditions and the ecological impacts of human activities.
Diatoms (microscopic one-celled or colonial algae) are suitable indicator organisms to monitor for changes in salinity and nutrient concentrations because diatoms: 1) are found in all surface waters; 2) grow quickly; 3) are directly affected by measurable water-quality constituents; 4) are cost-effective to collect and analyze; and 5) have well documented tolerance ranges of salinity and nutrients for many species assemblages. Investigative results of diatom distribution and community assemblages, which can be correlated with the water quality and hydrologic data collected for regulatory purposes, can be used to refine and calibrate hydrologic models and to design expanded ecological investigations.
Objectives
1) Provide a preliminary analysis of diatom assemblages in Spring Creek
2) Evaluate the approach as a means for identifying ecological changes in the watershed as a result of human activities
Figure 2. Floating diatom sampler near USGS gage at the mouth of Spring Creek, FL.
Approach
Diatoms were collected at five sites along Spring Creek and at one reference site in a nearby freshwater pond from January to May 2011 using floating artificial substrate samplers to make a preliminary assessment of this taxonomic group as an indicator community for changes in salinity related to predicted sea-level rise. Data were collected near spring outflows (fig. 1) in coastal parts of the Woodville Karst Plain during a period when spring flows vary in response to regional rainfall. A total of 58 samples were collected during the 4-month period. Algal assemblages were identified, enumerated, and analyzed statistically.
Results
Hierarchial clustering and ordination of samples by multidimensional scaling indicated similarity among four groups of samples. The diatom assemblages sampled in Spring Creek were similar in February and March, a period when cumulative rainfall was higher and salinity was typically lower in Spring Creek. Diatom assemblages collected during April and May at the most upstream site in Spring Creek grouped together, and likewise assemblages sampled at the site with the greatest freshwater groundwater outflow grouped together. Diatom assemblages sampled at the midstream and downstream sites, and the USGS gage (fig. 2) were similar to each other during April and May. None of the diatom assemblages in Spring Creek were similar to the diatom assemblages collected at the freshwater reference site. Diatom assemblages have potential as an indicator community of ecosystem changes related to salinity in coastal regions of the Wakulla Karst Plain.
Information Products
A journal article will describe the preliminary assessment of diatoms as an indicator community in Spring Creek, Florida.
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U.S. Department of the Interior |
U.S. Geological Survey
