technical supplement no.1 IAIAnd ~~Ioureo$ 'oundatton, Inc: 1718 P 8"tt6Ct, ttV'J., Suite Ti04 Wasfi.nit~n, j.),C, .NoH MARINE ENVIRONMENTS OF THE VIRGIN ISLANDS technical supplement no.1 prepared by ISLAND RESOURCES FOUNDATION for Government of the Virgin Islands of the United States VIRGIN ISLANDS PLANNING OFFICE COASTAL ZONE MANAGEMENT PROGRAM Cyril King GOVERNOR Thomas R. Blake DIRECTOR OF PLANNING August, 1977 The preparation of this report was financed in part through a Coastal Zone Management Program Development Grant as provided by Section 305 of the Coastal Zone Management Act of 1972, administered by the Office of Coastal Zone Management, National Oceanic and Atmospheric Administration. ISLAN'D RESOURCES F"OUNDATION P.O. BOX 4187, ST. THOMAS, U.S. VIRGIN ISLANDS 00801 • (809) 775-3225 April 8, 1976 Mr. Thomas R. Blake, Director of Planning V.I. Planning Office, Office of the Governor Government of the U.S. Virgin Islands Dear Mr. Blake: The Virgin Islands constitute a unique island system - a place of value, beauty, and inspiration, possessing a rich history, spectacular marine life, diverse coastlines and a salubrious climate. They also have a promising future as a habitat for resident faunal, floral, and human species, living in a balanced, natural beauty. There is, however, mounting evidence that the human component of our islands' population has, through oversight, uncontrolled expansion, and ill conceived actions, induced a broad spectrum of stresses that threaten the natural viability of the island system and could destroy what Alexander Pope referred to as "th e gen i us of the place." Th is process is especially apparent in the coastal zone of the Virgin Islands where competing human interests and dynamic components of natural ecosystems interface and interact. The present effort to develop a management plan for this critical zone of man-environment inter­ relationship offers the promise of minimizing environmental conflict, improving resource allocation decisions, preserving our insular heritage and restoring the intricate balance with natural systems. Our mission was to establish a point of departure in assessing the marine segment of the endangered coastal zone, reviewing what is known, preparing an inventory and classification of component subsystems and defining their inter-relationships. Lastly, we have sought to suggest preliminary guidelines for the planner who bears the ultimate responsibility for devising procedures and making t"ecommendations to our government on how to improve upon management of the coastal zone. This has been an exciting, awesome and inspiring project. Thank you for the opportunity to under­ take this study. I take great pleasure in submitting this report. We trust you will find it useful in the tasks which lie ahead. Sincerely yours, ,d~~·--'-~ Edward L. Towle, Ph.D. President COASTAL ZONE MANAGEMENT STAFF Darlan Brin, Assistant Director of Planning and Program Director Edward H. Lindelof, Project Coordinator Walter L. Stewart Steven L. Colman William F. Newbold, Jr. Marsha McLaughlin Roy E. Adams Katina Coulianos ISLAND RESOURCES PROJECT STAFF STAFF Edward L. Towle, Project Director David I. Grigg, Senior Biologist William E. Rainey, Ecologist CONSU L T ANTS Maynard Nichols, Oceanographer John McEachern, Resource Planner James A. Dobbin, Landscape Planner ACKNOWLEDGEMENTS The following people were helpful in identifying existing resource information: E.A. Bertrand David Olsen Lagoon Marina Virgin Islands Department of St. Thomas, Virgin Islands Conservation and Cultural Affairs John R. Clark Timothy B. Still The Conservation F ou ndation Virgin Islands Department of Washington, D.C. Conservation and Cultural Affairs Arthur E. Dammann Robert T eytaud Virgin Islands Department of Virgin Islands Department of Conservation and Cultural Affairs Conservation and Cultural Affairs Robert Dill Robert P. VanEepoel West Indies Laboratory Virgin Islands Department of St. Croix, Virgin Islands Conservation and Cultural Affairs Johnny Harms Werner Wernicke Lagoon Marina Virgin Islands Department of St. Thomas, Virgin Islands Conservation and Cultural Affairs Robert S. Mathes John A. Yntema Virgin Islands Department of Virgin Islands Department of Conservation and Cultural Affairs Conservation and Cultural Affairs Ervin H. Zube University of Massach usetts iv CONTENTS INTRODUCTION v SYNTHESIS - COASTAL ZONE 80 PLANNING GUIDELINES INVENTORY OF NATURAL RESOURCES 1 Regional Context 80 Oceanography and Climatology 1 Planning Concept: 80 Tides and Currents 1 Ecosystems Approach Waves and Swell 9 Water Quality 11 GUIDELINES FOR RESOURCE 81 Prevailing Winds 22 MANAGEMENT Storms and Hurricanes 24 Precipitation and 27 Vital Areas 81 Evaporation Areas of Environmental Concern 81 Geophysical Factors 29 Areas of Normal Concern 82 Bathymetry 29 Seismic Activity 31 Areas of Regional, National 82 and I nternational Concern Marine Ecology 33 Guidelines for Ecosystem 82 Fisheries 33 Management Other Coastal Wildlife 39 Coastal and Submarine 39 RECOMMENDATIONS FOR 88 Habitats FURTHER STUDY Beaches 44 SUMMARY 90 Rocky Shores 52 Salt Ponds 54 SELECTED BIBLIOGRAPHY 101 Mangroves 56 Coral Reefs 63 Sandy Bottoms 67 Grass Beds 68 Offshore Cays 70 Other Marine Resource 72 Elements Other Marine Resource 72 Elements ANAL YSIS OF BIOPHYSICAL 75 RELATIONSHIPS Classification of Coastal 75 Ecosystems Critical Areas 77 Areas of High Productivity 77 Areas Under Stress 78 IlninllP Arp;:J<; 79 FIGURES AND TABLES FIGURES 1. Predicted and observed tidal ranges in St. Thomas harbor, March - April, 1972 2 2. Variations in the character of the tide displayed in time-height curves 2 in Christiansted harbor, June 29- July 19,1971. 3. Annual prevailing currents in the Caribbean. 4 4. General current patterns on the island platforms. 4 5. Mean surface current, speed and direction for Christiansted harbor currents 6 and for littoral currents, August 1971. 6. Maximum bottom currents recorded at ten points in Can eel Bay, St. John. 6 7. Surface currents near Great St. James Island in August. 7 8. Water movement in Jersey Bay and Mangrove Lagoon, St. Thomas. 8 9. Average sea and swell conditions for Virgin Islands coasts. 10 10. August surface temperatures. 11. January surface temperatures. 13 12. Winter-Spring (December-April) inshore water temperatures, St. Croix. 14 13. Summer-Fall (J une-October) inshore water temperatures, St. Croix. 14 14. Winter-Spring (December-April) inshore water temperatures, St. John. 15 15. Summer-Fall (J une-October) inshore water temperatures, St. John. 15 16. Winter-Spring (December-April) inshore water temperatures, St. Thomas. 16 17 . Summer-Fall (J une-October) inshore water temperatures, St. Thomas. 16 18. Contours of equal salinities (isohalines) in Jersey Bay and Mangrove Lagoon. 18 19. Diurnal variation of dissolved oxygen, salinity, pH and temperature measured 20 at one foot depth in south Jersey Bay, St. Thomas, 1970. 20. Wind direction and speed frequency, central Caribbean, January-June. 22 21. Wind direction and speed frequency, central Caribbean, July-December. 23 22. Tropical cyclone frequencies: latitude 150 - 200 N. 25 23. Hurricane paths that have affected the Virgin Islands since 1876. 26 24. One hundred year frequency and standard project tidal flood stage hydrographs. 27 25. Bathymetry of Virgin Islands basins and plateaus. 29 26. Profiles of bottom topography across the Virgin Islands shelf south of 30 St. Thomas and St. John. 27. Distribution of Caribbean seismic and volcanic activity. 32 28. Coastal and submarine habitats, St. Croix 40-41 29. Coastal and submarine habitats, St. Thomas and St. John 42-43 30. Beach profile showing beach terminology and component parts in relation 45 to high and low water. C 31. High energy winter profile and moderate energy summer (beach) profile. 45 32. Summer and winter beach profile in relation to beach roc~. 47 33. Representation of sand transport in an enclosed bay. 47 34. Profile of a beach indicating physical zonation and characteristic organisms. 48 35. Typical rocky shoreline of eroded volcanic rock with boulder and rubble bottom. 53 36. Cross-section of a salt pond. 54 37. Salt River, St. Croix, showing drainage patterns and protective reefs. 56 38. Profile of a mangrove forest showing typical zonation and associated habitats. 58 39. Marine ecological zones of Jersey Bay and Mangrove Lagoon, St. Thomas. 59 40. Benthic communities of Salt River estuary. 60 41. Diagrammatic profile of an offshore reef system. 64 42. Profile of a sand-dominated bottom. 68 43. Typical shallow water sea grass bed. 68 44. Rocky shoreline and associated sea bottom. 74 45. Typical sand beach ecosystem showing relationship of component habitats. 76 46. Mangrove dominated ecosystem with lagoonal flats and protective reef. 77 47. Man-dominated bay ecosystem. 78 TABLES 1. Major element composition of sea water. 17 2. Occurrence of tropical storms and hurricanes within 240 nautical miles of 25 St. Croix. 3. Location of Virgin Islands salt ponds, excluding cays. 57 4. Partial list of birds from Jersey Bay mangrove lagoon including cays. 62 5. Inventory of offshore cays. 71 vii available for alternative uses. Protection not only Introduction maintains natural productivity and aesthetic values, but preserves use options for future generations. The coastal zone is an area that, far from separat­ ing land from sea, brings the two together in a The following compilation is intended as a first complex interaction of living and physical features. effort survey of Virgin Islands