University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School 4-4-2003 Count or Pointcount: Is Percent Octocoral Cover an Adequate Proxy for Octocoral Abundance? Matthew .J Lybolt University of South Florida Follow this and additional works at: https://scholarcommons.usf.edu/etd Part of the American Studies Commons Scholar Commons Citation Lybolt, Matthew J., "Count or Pointcount: Is Percent Octocoral Cover an Adequate Proxy for Octocoral Abundance?" (2003). Graduate Theses and Dissertations. https://scholarcommons.usf.edu/etd/1422 This Thesis is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. COUNT OR POINTCOUNT: IS PERCENT OCTOCORAL COVER AN ADEQUATE PROXY FOR OCTOCORAL ABUNDANCE? by MATTHEW J. LYBOLT A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Biological Oceanography College of Marine Science University of South Florida Major Professor: Pamela Hallock Muller, Ph.D. Walter C. Jaap, B.S. James W. Porter, Ph.D. George Yanev, Ph.D. Date of Approval: 4 April 2003 Keywords: Octocoral, Gorgonia ventalina, Florida Keys, Percent Cover, Hurricane Georges © Copyright 2003, Matthew Lybolt Acknowledgements I would like to thank and acknowledge my major professor Dr. Pamela Hallock Muller for valuable input and much appreciated latitude. With her guidance, my skill as a writer and my capacity as a scientist have improved greatly. I would like to thank my committee members Walter Jaap, Dr. James Porter and Dr. George Yanev for valuable input. I am especially indebted to Keith Hackett for serving as a sounding board and counseling a rookie through statistics. Thanks to the entire 2002 CRMP field team who helped me conduct the in situ surveys, MK Callahan, Jim Kidney, Walt Jaap, Jim Porter, Cecilia Torres, Katie Sutherland, and especially Selena Kupfner. Much appreciation goes to a talented collection of friends and family for reviewing the many generations of this manuscript: Dr. Stephen Freedman, Keith Hackett, Karen Hug, Chris Koelling, Dr. Vladimir Kosmynin, Mary Lou Lybolt, Dr. John Lybolt, and Diane Rosenberg. Finally, I must thank my parents, Karen, and my friends for supporting and tolerating me throughout this endeavor. TABLE OF CONTENTS LIST OF TABLES .............................................................................................................. iii LIST OF FIGURES ...............................................................................................................v ABSTRACT ....................................................................................................................... vi 1. INTRODUCTION ............................................................................................................1 INTRODUCTION TO OCTOCORALLIA OF THE CARIBBEAN ...........................2 Caribbean Octocoral Systematics ..................................................................2 Caribbean Octocoral Ecology........................................................................4 DESCRIPTION OF PRIMARY DATA SOURCE ......................................................7 METHODS APPLIED TO OCTOCORAL HABITAT CHARACTERIZATION.........9 SIGNIFICANCE .....................................................................................................10 2. METHODS ..................................................................................................................... 11 CRMP METHODS.................................................................................................. 11 STUDY METHODS ...............................................................................................12 Station Selection ..........................................................................................12 Year Selection ..............................................................................................14 In situ Octocoral Counts ..............................................................................14 Video-Derived Octocoral Counts .................................................................14 Comparison of In Situ and Video Counts......................................................15 Statistical Treatment of Video-Derived Abundance Data ..............................15 Statistical Treatments of Comparative Study of Video-Derived Abundance and Percent Cover .......................................................................................17 3. RESULTS .......................................................................................................................19 IN SITU VERSUS VIDEO DATA ...........................................................................19 VIDEO-DERIVED ABUNDANCE .........................................................................20 VIDEO-DERIVED ABUNDANCE VERSUS PERCENT COVER .........................34 4. DISCUSSION .................................................................................................................37 ASSESSMENT OF METHODS ..............................................................................37 Video-Derived Octocoral Counts .................................................................37 In Situ vs. Video-Derived Octocoral Counts .................................................37 Biases to data ..............................................................................................38 ECOLOGICAL RESULTS – ABUNDANCE...........................................................39 Study Results Compared to Other Octocoral Surveys in the Northern Caribbean....................................................................................................39 Assemblage In 1996 .....................................................................................41 Abundances in 1996 and 1998 .....................................................................41 Abundances in 1998 and 1999: Inferences about Hurricane Georges ...........42 Abundance comparing 1999 and 2002 .........................................................44 Overall changes, 1996 to 2002.....................................................................45 ABUNDANCE VS PERCENT COVER. .................................................................46 Video-Derived Abundance Correlation with Octocoral Percent Cover..........46 Abundance and Percent Cover Trend Correlation ........................................47 RECOMMENDATIONS .........................................................................................49 Further applications ....................................................................................49 Refining the study methods...........................................................................49 Altering the PointCount method for quantification of octocoral ...................51 5. CONCLUSIONS.............................................................................................................52 REFERENCES ...................................................................................................................53 APPENDICES ....................................................................................................................56 LIST OF TABLES Table 1. Key characteristics of selected stations. ...........................................................13 Table 2. Maximum and minimum Bray-Curtis similarity coefficients for video-derived abundance trials 1 and 2. .........................................................................................20 Table 3. Average octocoral density by habitat type and region. ......................................25 Table 4. p-values for two-tailed paired sample t-Test, testing the assumption that abun- dances are equal between 1996 and 1998. Shaded blocks indicate significant differ- ences (a=0.05).........................................................................................................28 Table 5. Summary of significant two-tailed paired sample t-Test results where abundance in 1996 ¹ 1998 at a=0.05, combined with relative magnitude of change from 1996 to 1998. .......................................................................................................................28 Table 6. p-values for two-tailed paired sample t-Test, testing the assumption that abun- dances are equal between 1998 and 1999. Shaded blocks indicate significant differ- ences (a=0.05).........................................................................................................29 Table 7. Summary of significant two-tailed paired sample t-Test results where abundance in 1998 ¹ 1999 at a=0.05, combined with relative magnitude of change from 1998 to 1999. .......................................................................................................................29 Table 8. p-values for two-tailed paired sample t-Test, testing the assumption that abun- dances are equal between 1999 and 2002. Shaded blocks indicate significant differ- ences (a=0.05).........................................................................................................30 Table 9. Summary of significant two-tailed paired sample t-Test results where abundance in 1999 ¹ 2002 at a=0.05, combined with relative magnitude of change from 1999 to 2002. .......................................................................................................................30