BOBLME-2011-Ecology-04
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BOBLME-2011-Ecology-04 The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. For bibliographic purposes, please reference this publication as: BOBLME (2011) Community-based tarball monitoring in the Maldives. BOBLME-2011-Ecology-04 Community-based tarball monitoring in the Maldives Brian G. Long February 2011 i List of Contents List of Contents .............................................................................................................ii List of Figures ...............................................................................................................v List of Tables ................................................................................................................vi 1. EXECUTIVE SUMMARY ................................................................................... 1-1 2. CONCLUSIONS AND RECOMMENDATIONS ................................................. 2-2 2.1 Survey Design Improvements ............................................................................... 2-2 2.1.1 When to sample tarballs .................................................................................... 2-2 2.1.2 Where to sample tarballs ................................................................................... 2-2 2.1.3 Distribution and abundance of tarballs ............................................................... 2-2 2.1.4 Standardized sampling protocol ......................................................................... 2-2 2.1.5 Maps of the island .............................................................................................. 2-3 2.1.6 Standardized data recording .............................................................................. 2-3 2.2 Data entry workbook .............................................................................................. 2-3 2.2.1 Raw data ............................................................................................................ 2-3 2.3 Database................................................................................................................ 2-3 2.4 Data analysis ......................................................................................................... 2-4 2.4.1 Geographically weighted regression versus Ordinary Least Squares ................ 2-4 2.4.2 Paired T-test ...................................................................................................... 2-4 2.4.3 Tarball size categories ....................................................................................... 2-4 2.5 Success of the monitoring program ....................................................................... 2-4 2.6 Key Outcomes ....................................................................................................... 2-4 2.6.1 Draft survey design ............................................................................................ 2-4 2.6.2 Participatory approach and dissemination of findings ........................................ 2-5 3. INTRODUCTION ............................................................................................... 3-5 3.1 Purpose of this study ............................................................................................. 3-6 4. LITERATURE REVIEW ..................................................................................... 4-6 4.1 Use of tarballs for monitoring oil pollution .............................................................. 4-6 4.2 Tarball formation .................................................................................................... 4-6 4.3 Tarball and oil spill cleanup and post-incident monitoring ..................................... 4-9 4.4 Chemical and physical characteristics of tarballs .................................................. 4-9 4.5 Toxicity of tarballs .................................................................................................. 4-9 4.6 Distribution and abundance of tarballs in the marine environment ....................... 4-9 4.7 Tarball and oil spill weathering ............................................................................ 4-10 4.7.1 Physical weathering ......................................................................................... 4-10 4.7.2 Chemical breakdown ....................................................................................... 4-11 4.8 Source of tarballs ................................................................................................. 4-11 4.8.1 Natural ............................................................................................................. 4-11 4.8.2 Anthropogenic .................................................................................................. 4-11 4.9 Methods for sampling tarballs .............................................................................. 4-12 4.10 Infamous marine oil spills .................................................................................... 4-12 4.11 Oil spill and tarball trajectory modelling ............................................................... 4-12 4.12 Tarballs monitoring databases ............................................................................ 4-12 4.13 Tarball and oil spill fingerprinting ......................................................................... 4-13 5. MATERIALS AND METHODS ........................................................................ 5-13 5.1 Data Sources ....................................................................................................... 5-13 ii 5.1.1 Geodatabase ................................................................................................... 5-13 5.1.2 GEBCO bathymetry data ................................................................................. 5-13 5.1.3 Winds and currents .......................................................................................... 5-13 5.1.4 Islands and reefs .............................................................................................. 5-13 5.1.5 Atoll apertures .................................................................................................. 5-14 5.1.6 Island names and positions ............................................................................. 5-14 5.1.7 Shipping lanes ................................................................................................. 5-14 5.1.8 School locations ............................................................................................... 5-14 5.2 Description of the study area ............................................................................... 5-14 5.2.1 Atolls, Islands and Reefs ................................................................................. 5-14 5.2.2 Atoll perimeter .................................................................................................. 5-20 5.2.3 Water depth ..................................................................................................... 5-25 5.2.4 Winds and surface currents ............................................................................. 5-27 5.2.5 Shipping routes ................................................................................................ 5-32 5.3 Tarball sampling methods .................................................................................... 5-34 5.4 Data analysis ....................................................................................................... 5-34 5.4.1 Spatial join island name point data to polygon data ......................................... 5-34 5.4.2 Perimeter of islands and reefs ......................................................................... 5-34 5.4.3 Digital Elevation Model .................................................................................... 5-34 5.4.4 Spatial modelling .............................................................................................. 5-34 5.4.5 Exploratory data analysis ................................................................................. 5-37 5.4.6 Change in abundance of tarballs over time ...................................................... 5-37 5.4.7 Ordinary Least Squares Regression ................................................................ 5-49 6. RESULTS ........................................................................................................ 6-50 6.1 Sampling effort ..................................................................................................... 6-50 6.2 Abundance and size of tarballs ........................................................................... 6-50 6.3 Abundance of tarballs in relation to exposure to shipping ................................... 6-51 6.4 Change in abundance of tarballs over time ......................................................... 6-53 6.4.1 2007 versus 2006 ...........................................................................................