1. Applying GIS to Santa Cruz Island:
Density estimation of intertidal species
clients.alexandria.ucsb.edu
Carola Flores, Nic Galati, Jeff Overlock, and Heather Thakar Hucks

2. Research Background Specific Objectives
Ecological spatial variation within the intertidal zone on Santa Cruz Island can be interpreted on different scales:
Density of Species (number)
Abundance of Species (diversity)
Geographic Information Systems provide effective spatial tools for the analysis and visual representation of species density.
Main Objective
Develop a prototype GIS model to assist in the analysis of large quantities
of data collected by PISCO and SWAT
Specific Objectives
Map intertidal species density within two ecological sites (Fraser and Valley)
Evaluate potential intra-site spatial patterns of intertidal species density
Evaluate potential inter-site density variation
Look for potential causes and effects of the intertidal density variability

3. Valley
Fraser

4. Datasets Santa Cruz Island DEM Sea-Surface Temperature
Point Contact data
Non-mobile intertidal species
Classification table data
Quadrat data
Mobile intertidal species
Classification table data
Swath data
Sea star presence or absence
Santa Cruz Island DEM
Sea-Surface Temperature

5. Data Sources Data Management
Data provided in text files by Carol Blanchette, associated with the Coastal Biodiversity Surveys (CBS) on Santa Cruz Island, PISCO (UCSB), SWAT (UCSC)
30 meter DEM of Santa Cruz Island provided by Jeff Howarth
Raster of Sea Surface Temperature provided by Bernardo Broitman
Data Management
Excel was used to open text files
Deletion of data unnecessary for current analysis
Latitude and Longitude coordinates converted to UTM for thousands of points
Assignment of unique key for all points based on concatenation of X and Y locations
Data converted into DBASE IV format
DBF’s of Point Contact, Quadrat, and Swath Data for both Fraser and Valley sites, brought into ArcMap and converted into point shapefiles
Shapefiles projected to the same coordinate system as the Santa Cruz Island DEM
Species classification tables (in dbf format) brought into ArcMap and joined to shapefile attribute tables

6. Fraser Site 300 Swath Quadrat Point contact Valley Site 304 Swath
Frasier
Swath
Quadrat
Point contact

7. Problems with Data
Data size: Large datasets from 10 years of intertidal surveying were difficult
for data management
Sampling: Datasets from only two ecological sites of Santa Cruz Island were used, thus
results may not represent the density patterns of Santa Cruz’s intertidal species.
Uncertainty: Datasets contain fine-scale multiple measurements. Due to the complex
spatial distribution of species in the intertidal, to portray an accurate digital representation is
challenging.
Gremlins: We have very scientifically concluded that Excel is possessed. Odd
occurrences in the excel files required hours of work to restore the files to a usable condition.

8. Intra-site Elevation DEM
METHODS
Intra-site Elevation DEM
Created by Natural Neighbor Interpolation based on elevation data collected at each point contact location along the transects
High Intertidal Zone
Mid Intertidal Zone
Low Intertidal Zone

9. Species Density Estimation Map
Created for each data set within each site using Spatial Analyst Density Estimation
METHODS

10. Intra-Site Species Density
Created using Spatial Analyst Raster Calculator to combine the individual species density raster datasets, producing a single Intra-Site Species Density Map for each site
METHODS

11. Intra-Site Species Density & Elevation, Fraser
Meters
RESULTS

12. Comparison of Non-Mobile Species & Elevation
Meters
ANALYSIS
ANALYSIS

13. Comparison of Mobile Species & Elevation
Meters
ANALYSIS

14. Comparison of Starfish Density & Elevation
Meters
ANALYSIS

15. Comparison of Site Species Density & Elevation, Fraser
Meters
ANALYSIS

16. Intra-Site Species Density & Elevation, Valley
Meters
RESULTS

17. Comparison of Non-Mobile Species & Elevation
Meters
ANALYSIS

18. Comparison of Mobile Species & Elevation
Meters
ANALYSIS

19. Comparison of Starfish Density & Elevation
Meters
ANALYSIS

20. Comparison of Site Species Density & Elevation, Valley
Meters
ANALYSIS

21. Inter-site Comparison of Fraser & Valley Site Densities and Sea Surface Temperature
ANALYSIS

22. Conclusions
There are differences in density distribution of intertidal species
between the two sampled sites.
There is not a significant difference in the total count of intertidal species between the two sampled sites.
Differences in density distribution of intertidal species
between the two sampled sites could be a result of differences in
intertidal topography:
-An intertidal zone with relatively homogeneous surface
elevation is more likely to exhibit an even density
distribution of all species.
- An intertidal zone with a less homogeneous surface
elevation is more likely to exhibit a patchy density
distribution of all species.

23. Conclusions
Site
300 (Fraser)
304 (Valley)
SST (°Celsius) 13 17
Non-Mobile Species
3030
2916
Mobile Species
128
178
Sea stars 24
122
Total Species
3182
3216
Our analysis does not indicate that Sea Surface Temperature had a
measurable effect on the density distribution of intertidal species at
Fraser site or Valley site in 2002.
This unanticipated result may be attributed to:
-the narrow temporal scope of our analysis
(data set limited to 2002)
-the narrow spatial scope of our analysis
(data set limited to only two locations on Santa Cruz Island)

24. Applying GIS to Santa Cruz Island:
Density estimation of intertidal species
clients.alexandria.ucsb.edu
Acknowledgements: Carol Blanchette, Josh Bader, Bernardo Broitman, Jeff Howarth