1. Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts
Presenter: Kirsten Lackstrom,
Carolinas Integrated Sciences & Assessments (CISA)
Co-Authors: Paul Conrads (USGS), Bryan McCloskey (USGS), Lauren Rouen (CISA)
98th American Meteorological Society Annual Meeting
January 8, 2018

2. What does drought look like…
… on the coast?
Source: Dan Tufford
Source: Ed Christopher
Source: USFS
Photo credits:
Flatwoods depression, Brunswick Co, NC, Dan Tufford
Fire at Pocosin Lakes Wildlife Refuge, NC, Ed Christopher
Ghost forest (SC) photo credit: Flying Ahead of Troubled Waters video, CISA,
Evans Road (NC) Fire photo credit: USFS
Source: CISA
Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts

3. Drought and coastal ecosystems
Salinity is a key stressor
Focus of the Coastal Carolinas Drought Early Warning System (DEWS)
“Can a unique index be developed to characterize coastal drought?”
Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts

4. Coastal Salinity Index (CSI)
Similar approach to the Standardized Precipitation Index (SPI)
Conrads and Darby (2017)
Indicates drought and wetter conditions over multiple time periods
1- to 24-months
Indicator of salinity changes and location of the freshwater-saltwater interface
Conrads, P.A. and L.S. Darby, 2017: Development of a Coastal Drought Index Using Salinity Data. Bull. Amer. Meteor. Soc., 98, 753–766,
Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts

5. Computation Calculated at 30 sites
Florida
South Carolina
R-package for consistent calculation created in 2017
Next step is testing
Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts

6. Salinity Data Sources Availability Frequency USGS NERRS
University research
State agencies
Availability
Earliest ongoing records begin in the 1980s
Frequency
15-minutes to monthly
Map shows 100+ sites that have a minimum of 10 years of data. Approximately 50 of those sites have 18 years of salinity data.
Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts

7. CSI Plot for St. Pierre Creek, Ashepoo-Combahee-Edisto (ACE) Basin, SC
The CSI values shown here (CW4) indicate that these were the wettest, long-term conditions experienced by this station over its history.
The arrow indicates a period when long-term CSI values indicate drought conditions, but short-term conditions were fresh, suggesting recovery from drought.
These were the driest conditions (CD4) experienced by this station over its history.
Coastal Salinity Index interval (months)
Period of record values and estuarine salinity ranges (in psu)
The overall site mean (approx. 28 psu), dark gray
A 12-month rolling average of salinity values, light blue
The 25th percentile (approx. 26 psu) and 75th percentile (approx. 32 psu) values, light gray
CSI Stacked Plots: the CSI characterizes changes from average conditions for the computational interval but does not provide information on actual salinity values at the site.
The color ramp indicates the Coastal Salinity Index value. A value of “normal" indicates historical median salinity amount, and positive and negative values represent increasingly fresh and saline conditions, respectively. The color ramp is relative to the period of record for each station, so a value of CD4 for this station may not be equivalent to a value of CD4 at a different station.
To provide information on the measured salinity at the site, the right Y-axis shows the mean, 25th and 75th percentiles values are shown period of record. For St. Pierre Creek, the mean value is 28 psu and the 25th and 75th percentiles are 26 and 32 psu, respectively
The right y-axis of the stacked CSI plot shows typical salinity classifications for tidal waters from oligohaline (between 0.5 and 5 psu) to euhaline (greater than 30 psu).
For St. Pierre Creek the mean salinity conditions are at the high salinity range of polyhaline systems.
CSI Plot for St. Pierre Creek, Ashepoo-Combahee-Edisto (ACE) Basin, SC

8. Estuarine Research Reserve Water Quality Stations
Low average salinity dampens CSI sensitivity to extreme floods FC MC SP BB
ACE Basin National
Estuarine Research Reserve
Water Quality Stations
High average salinity dampens CSI sensitivity to extreme drought
Source: Michael Childress, Clemson University

9. Dissemination
The Coastal EDEN webpage currently provides plots for South Florida sites
CSI values will become available on USGS ScienceBase site in 2018
Coastal EDEN presents real-time data for the oligihaline/mesohaline zone in the Southern Everglades. These coastal areas, or specifically the Coastal Oligohaline Wetlands Zone (sometimes referred to as "the coastal fringe" or the "zone of change"), are critical in evaluating the hydrologic and ecological responses to modifications of the water delivery system from restoration and future climate change. Hydrologic changes, either from flow alterations or climate change, will first be manifested along the coastal fringe. These areas experience tidal backwater conditions, and increases in flow and (or) sea-level rise may move this seaward or landward. Coastal areas will probably exhibit larger relative changes in hydroperiods as compared to inland areas.
This page allows you to display current hydrologic data for USGS-operated coastal stations in south Florida. These data are stored in the USGS National Water Information System (NWIS) database. To download current and historical data and data for other discontinued and non-real-time gages, go to South Florida Hydrology Data Download.

10. Applications: Coastal Carolinas DEWS
Quarterly working group meetings, began late 2016
Literature review to identify ecological response variables
CSI correlations with ecological response variables
User Guide
Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts

11. availability and timing
Freshwater
availability and timing
Estuarine conditions and resources
Adapted from Crausbay et al. (2017)
Reference: Crausbay, S.D., A.R. Ramirez, S.L. Carter, M.S. Cross, K.R. Hall, D.J. Bathke, J.L. Betancourt, S. Colt, A.E. Cravens, M.S. Dalton, J.B. Dunham, L.E. Hay, M.J. Hayes, J. McEvoy, C.A. McNutt, M.A. Moritz, K.H. Nislow, N. Raheem, and T. Sanford, 2017: Defining Ecological Drought for the Twenty-First Century. Bull. Amer. Meteor. Soc., 98, 2543–2550,
Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts

12. Blue crab response to drought
Reference: Michael Childress,
CoastalCarolina/Childress-UCAR-Subaward-Final-Report.pdf

13. Coastal Salinity Index
River Discharge
Coastal Salinity Index
Model Fit
r2 =
r2 =
0 Yr Lag
Annual CSI is a better fit, compared to annual river discharge.
Strongest correlation is with blue crab landings three years later.
This suggests that salinity impacts accrue across a generation of blue crabs.
r2 =
r2 =
1 Yr Lag
r2 =
r2 =
2 Yr Lag
r2 =
r2 =
3 Yr Lag
Source: Michael Childress, Clemson University

14. Other responses
A long term study of marsh vegetation in Savannah, GA (Wetzel & Kitchens, 2007) found shifts in marsh species composition as a result of a severe drought from 1998 to
Studies of Vibrio vulnificus rates in oysters have found a relationship between increased salinities (caused by drought) and reduced presence of this bacteria in oysters (Wetz et al., 2014; Froelich et al., 2012)
Spartina alterniflora photo credit: USDA-NRCS PLANTS Database,
Oyster photo credit: JamesDeMers;
References:
Froelich, B. A., T. C. Williams, R. T. Noble, and J. D. Oliver Apparent loss of Vibrio vulnificus from North Carolina oysters coincides with a drought-induced increase in salinity. Applied and Environmental Microbiology 78(11):
Wetz, J. J., A. D. Blackwood, J. S. Fries, Z. F. Williams, and R. T. Noble Quantification of Vibrio vulnificus in an estuarine environment: a multi-year analysis using QPCR. Estuaries and Coasts 37:
Wetzel, P. R. and W. M. Kitchens Vegetation change from chronic stress events: Detection of the effects of tide gate removal and long-term drought on a tidal marsh. Journal of Vegetation Science 18 (3):
Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts

15. Questions? USGS South Atlantic Water Science Center
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Carolinas Integrated Sciences & Assessments (CISA)
Contact Kirsten Lackstrom at
Coastal Salinity Index: Monitoring Drought on the Gulf and Atlantic Coasts