Land Forcing and Coral Reefs: Terrestrial Runoff as a Factor in Coral Reef Distribution

1. Land Forcing and Coral Reefs: Terrestrial Runoff as a Factor in Coral Reef Distribution By: Casey J. McLaughlin University of Kansas And Casey C. Smith Swarthmore College

2. Introduction Coastal ecosystems such as coral reefs are increasingly in danger from non-local anthropogenic effects such as deforestation, land use, and pollution in inland river basins. These non-local pressures are channeled from a potentially large basinscale through freshwater discharge into the coastal zone. As a first estimate of a reef—to--runoff relationship, I examined global reef distributions as a function of total runoff within the same 30’ grid cell. The resulting correlation suggested that runoff inhibited reef occurrence when runoff was greater than 1010 m3/yr. Combining basin runoff and five additional variables (average sea surface temperature, minimum salinity, wave height, tidal range, Chlorphyll-A) selected to proxy the effect of runoff, increased predictive capabilities. The use of statistical representation of spatial and temporal variability allowed useful analytical comparisons of the environmental variables. Spatial and temporal statistics (standard deviations minimum/maximum months, ranges) were summarized for each variable into a standard 30’ spatial grid cell, providing a common framework for K-means clustering routine. Further classification of runoff-related stresses can then be made, for example, by adding modeled sediment discharge to refine the prediction of areas of reef stress from human activities. This information is important to understanding both paleo-environmental forcing of reefs and the potential effects of present and future human alterations to the hydrologic cycle.

3. www.epa.gov/Oceans and Coastal Protection Coral Reefs and Your Coastal Watershed.htm Objective • Investigate the relationship between terrigenous runoff and coral reef distribution • Integrate land and ocean based data sets to test coral reef distribution relative to fresh water discharge 1. Selection Criteria 2. Data Integration 3. Hypothesis Testing Craig Quirolo http://www.reefrelief.org

4. Defining the limits of coral reef distribution: Minimum Sea Surface Temperature Salinity Light Penetration Aragonite Saturation Nutrient Loads Conceptual tie-in: We consider sediment loads in addition to proxies for the other variables Scale: 1 degree grid system 1,000 reef locations 1-100 year time scale 1. Selection Criteria 2. Data Integration 3. Hypothesis Testing Environmental Limits to Coral Reef Development, Where Do We Draw the Line? Kleypas, Joan, McManus, John, and Meñez, Lambert American Zoologist, Vol. 39, No. 1 February 1999

5. Environmental variables used to investigate sediment--reef relationships in the context of distribution-limiting variables Spatial Limitations: Land Forcing: Annual Basin Discharge (log) Latitude: 30N to 30S Reefs: Coastal focus ~6600 records Grid Cell: 0.5 degrees System Interaction: Wave Height, Tidal Range, and Chlorophyll-A Ocean Influence: Average Sea Surface Temperature Minimum Salinity Location: ReefBase reef location inventory ~10,000 total records 1. Selection Criteria 2. Data Integration 3. Hypothesis Testing

6. Reefbase Reef Inventory

7. LOICZ and Hexacorallia database structure 1. Selection Criteria 2. Data Integration 3. Hypothesis Testing

8. Analysis Methods • K-means clustering (LOICZVIEW) of runoff, reef occurrence • and environmental variables • Visualization • Buffering and spatial querying using ArcView GIS 1. Selection Criteria 2. Data Integration 3. Hypothesis Testing

9. Statistical Analysis of reef occurrence in relation to log basin runoff Runoff Unsupervised runoff clustering with reef overlay Considered alone, runoff has a strong anti-correlation with reef distribution

10. Statistical Analysis of reef occurrence in relation to combined env. variables Unsupervised Unsupervised clustering of 6 env. variables with reef overlay Runoff does not dominate distribution

11. Statistical Analysis of reef occurrence in relation to log basin runoff Supervised Supervised by runoff: clustering of 6 env. variables with reef overlay High runoff values show strong control of reef distribution

12. Deviations 1. Selection Criteria 2. Data Integration 3. Hypothesis Testing

13. The Americas-- visualizing results: an example

14. Africa and Arabia

15. Austral-Asia

16. Buffering: an alternative test of reef--runoff relationships If Log runoff > 9.8, few reefs are within ~80 km (ocean and coastal)

17. Conclusions • Terrigenous runoff doesinfluence reef distribution --occurrence threshold roughly 9.6x106 meters3/year/0.5 degree coastal cell • Integration of data is both possible and useful • Spatial and temporal resolution are always problems --hypothesis to be tested must match the scale of the data and vice versa 1. Selection Criteria 2. Data Integration 3. Hypothesis Testing

18. http://www.reefbase.org/ Web References http://www.kgs.ukans.edu/Hexacoral/index.html http://www.reefbase.org http://www.nioz.nl/loicz/ http://www.palantir.swarthmore.edu/~maxwell/loicz/ Support: NSF OCE-00-03970, ‘Biogeoinformatics of the Hexacorallia’; IGBP-LOICZ; UNEP-GEF