Coral Reef Restoration Handbook - Chapter 14 potx

2073_C014.fm Page 257 Friday, April 7, 2006 5:09 PM 14 Restoration Outcomes of the Fortuna Reefer Grounding at Mona Island, Puerto Rico Andrew W Bruckner and Robin J Bruckner CONTENTS 14.1 14.2 14.3 Introduction 257 Initial Restoration .258 Approach to Evaluate Fragment Survivorship 260 14.3.1 Early Patterns of Fragment Survival 260 14.3.2 Midcourse Correction 261 14.3.3 Patterns of Survival and Recovery over Years 261 14.3.4 Causes of Mortality 262 14.3.5 Effects of Size, Orientation, and Attachment Site .262 14.3.6 Effect of Depth .264 14.4 Efficacy of the Restoration 267 14.5 Conclusions 268 Acknowledgments 268 References 269 14.1 INTRODUCTION On July 24, 1997, the M/V Fortuna Reefer ran aground on a fringing reef located off the southeast coast of Mona Island (18°02'N; 67°51'W), 65 km west of mainland Puerto Rico (Figure 14.1) The 326-foot freighter remained grounded for days within the island’s largest remaining Acropora palmata (elkhorn coral) stand Although the Fortuna Reefer was not carrying any cargo at the time of the grounding, some of the approximately 100,000 gallons of fuel oil and 33,000 gallons of marine diesel were removed to prevent a spill and lighten the vessel prior to removal Steel cables were attached between the stern of the Fortuna Reefer and two tugboats to stabilize and extract the vessel During removal, the extraction path did not follow the original collision path and the steel cables dragged across the reef surface, further expanding the area of injury The grounding and subsequent removal of the Fortuna Reefer impacted 6.8 acres of shallow fore reef habitat.1 The reef substrate was crushed and fractured along the inbound track of the vessel, with additional damage occurring while the ship remained grounded as a result of waves and swell that caused the hull to rise and fall and shift sideways (Figure 14.2C) Total coral destruction occurred along the inbound and outbound paths of the vessel, extending from the reef crest approximately 300 m seaward (2 to m depth) and up to 30 m in width Collateral injuries from the steel cables extended beyond the perimeter of the vessel tracks, to m depth Entire 257 © 2006 by Taylor & Francis Group, LLC 2073_C014.fm Page 258 Friday, April 7, 2006 5:09 PM 258 Coral Reef Restoration Handbook Puerto Rico Puerto Rico Mona 67°W 18°N Mona Island 20 m Contour FR Reef Crest FIGURE 14.1 Location of the Fortuna Reefer restoration site off the southeast coast of Mona Island, Puerto Rico colonies of A palmata, many that were several meters in diameter, were crushed or dislodged and fractured by the boat, and the cables sheared off hundreds of additional A palmata branches (Figure 14.2E) Brain corals (primarily Diploria strigosa) and other benthic organisms were also abraded, shattered, or detached from the reef 14.2 INITIAL RESTORATION A team of experts from the Commonwealth of Puerto Rico and the National Oceanic and Atmospheric Administration (NOAA) Damage Assessment and Restoration Program (DARP) conducted a natural resource damage assessment of the grounding site and determined that an emergency repair of damaged corals was warranted Coral fragments were scattered across the reef, and many had collected in sand channels The surge continued to shift and overturn fragments, abrading their coral tissue and minimizing the likelihood of reattachment (Figure 14.2D) Without intervention, a high percentage of fragments may have died due to sand scouring or been removed from the site during periods of high wave action; securing coral fragments was predicted to accelerate recovery of the injury to the reef.1 Under the Oil Pollution Act (OPA) of 1990, NOAA expedited a settlement with the responsible party amounting to U.S $1.25 million for primary and compensatory restoration, including $650,000 to conduct an emergency restoration of coral resources injured as a result of the incident.2 The objectives of the emergency restoration were to reestablish the structural relief of the coral reef community and reduce coral mortality by reattaching loose A palmata branches.1 Between September 24, 1997, and October 14, 1997, a team of 19 marine engineers and biologists stabilized 1857 A palmata coral fragments Stabilized coral ranged from 15 cm to 3.4 m in length; all detached fragments larger than m, 80% of the fragments between 0.5 and 1.0 m, © 2006 by Taylor & Francis Group, LLC 2073_C014.fm Page 259 Thursday, April 20, 2006 11:54 AM Restoration Outcomes of the Fortuna Reefer Grounding at Mona Island, Puerto Rico 259 FIGURE 14.2 (See color insert following p 240.) Impacts of the M/V Fortuna Reefer to shallow reefs A The ship grounded in the reef crest Steel cables were attached between the vessel and tugboats to facilitate removal Photo courtesy of the NOAA Restortation Center B Undamaged elkhorn coral thicket adjacent to the grounding C The condition of the substrate after removal of the vessel The reef substrate was crushed and fractured D Example of a fragment that landed in the sand and was being scoured and buried E Acropora palmata fragments sheared off by the cables Photo courtesy of Dr Jack Morelock F Example of a fragment attached to nails inserted into the reef substrate Blue scale bar is 15 cm G Example of a fragment oriented upright that was being attached to a dead skeleton Photo courtesy of Coastal Planning & Engineering, Inc H Example of a fragment that was reattached in 1997 and had overgrown the wire but was secured with additional wire during the midcourse correction in July 2000 Blue scale bar is 15 cm © 2006 by Taylor & Francis Group, LLC 2073_C014.fm Page 260 Friday, April 7, 2006 5:09 PM 260 Coral Reef Restoration Handbook and 50% of the fragments up to 0.5 m in length were restored Fragments were secured to the relict reef substrate (reef) or to dead, standing A palmata skeletons (skeleton) Fragments attached to skeletons were expected to exhibit enhanced survivorship associated with a reduction in scouring, improved water circulation, increased light exposure, and possibly a reduced exposure to pathogens and benthic predators To secure fragments to the reef, stainless steel wire was extended across each fragment and then wrapped around stainless steel nails that were cemented into holes drilled in the reef (Figure 14.2F) Plastic cable ties were used initially to secure fragments to skeletons, with subsequent stabilization using wire that was wrapped around the fragment and skeleton.2,3 Fragments were reattached either in an upright or downward position (with respect to their original orientation) such that the live, unbleached tissue faced upwards (Figure 14.2G) They were firmly anchored to withstand normal surge and wave action typical of shallow, exposed reef environments Due to the high wave exposure observed during the restoration effort, cement or epoxy was not used, as the amount of time required for these materials to harden was not feasible.1 14.3 APPROACH TO EVALUATE FRAGMENT SURVIVORSHIP Fragment survival and patterns of coral recovery were evaluated approximately years after the grounding, and in May and August 2000, 2001, and 2003 The initial survey involved an assessment of the number, size, and condition of fragments that remained attached, and the number of fragments that were broken loose and displaced or missing Detached fragments were estimated by: Tallying groupings of nails within the reef to which fragments were no longer attached Counting remnant wire on skeletons that was not associated with fragments Counting detached fragments with remnants of attached wire For each remaining fragment, measurements of the size (maximum length to nearest centimeter), orientation (up, down, or sideways with respect to their orientation prior to breakage), location of attachment (reef or skeleton), and condition (live or dead) were recorded Dead fragments were marked with numbered aluminum tags to avoid recounting these on subsequent surveys Live fragments were examined and evaluated for tissue growth over the wire, presence of protobranches, natural cementation (fusion) to the reef or skeleton, and growth onto the substrate or skeleton Estimates of remaining tissue and percent mortality were made from a planar perspective For each fragment, a 1-m bar (divided into 1-cm increments) was oriented along the center of the long axis of the fragment to measure length, tissue survivorship, and tissue loss Partial mortality was recorded as the percent loss of tissue from the upper surface of the reattached branches and does not include mortality to branch undersides All fragments were presumed to have 100% of their upper surface covered with tissue when first reattached in 1997 Causes of partial or total mortality were identified as disease (white-band disease [WBD] or other syndromes); growth abnormalities (e.g., neoplasia or hyperplasia); overgrowth by boring sponges (Cliona spp.); predation by snails (Coralliophila abbreviata), polychaete worms (Hermodice carunculata), or parrotfish (Sparisoma viride); macroalgal competition; or presence of three-spot damselfish (Stegastes planifrons) territories If a cause of mortality could not be determined, it was recorded as unknown 14.3.1 EARLY PATTERNS OF FRAGMENT SURVIVAL More than half (57%) of the fragments were alive years after the restoration effort, while the remainder had died (26%) or became detached and removed from the site (17%).4 Fragments secured to the reef had lower rates of early mortality (27%) and a higher rate of detachment due © 2006 by Taylor & Francis Group, LLC 2073_C014.fm Page 261 Friday, April 7, 2006 5:09 PM Restoration Outcomes of the Fortuna Reefer Grounding at Mona Island, Puerto Rico 261 to wire breakage (24%) than fragments attached to skeletons Surviving fragments had tissue covering a mean of 50% of the original upper branch surface, with 23% of the fragments exhibiting little (200 Size class (cm) FIGURE 14.4 Size and condition of remaining live fragments in August 2003 The bars illustrate the percent of fragments in each size class oriented upright (white bars) and oriented down (spotted bars) The diamonds refer to the mean percent partial tissue mortality for each size class Standard error is presented for partial mortality 14.3.4 CAUSES OF MORTALITY Some of the most important factors contributing to fragment mortality were overgrowth by the brown boring sponge Cliona spp., predation by corallivorous gastropods, diseases, algal competition, and abrasion from the wire (Figure 14.7) Over the 6-year study, 20% of all fragments were killed by Cliona spp., and 5% of the remaining live fragments were affected by this sponge in August 2003 (Figure 14.8C) The sponge was most abundant on those fragments attached to dead standing colonies, advancing from the skeleton to the fragment Many of these colonies were colonized by the sponge prior to the restoration effort, as evidenced by video documentation of the restoration Disease was observed throughout the site at a low prevalence until 2003, when an outbreak of WBD was recorded on both restored fragments and unrestored colonies within and outside of the grounding site (Figure 14.8E) In August 2003, 4% of the living fragments and 15% of the standing colonies were affected by WBD The wire used in the initial restoration effort often negatively affected fragments Tissue abrasion associated with wire and/or fragment movement during periods of surge was noted under and adjacent to the wire in 73% of the live fragments during initial surveys (Figure 14.8A) However, this was not always the case, as 22% of restored fragments had completely or partially overgrown the wire Conversely, the wire used during the midcourse correction (July 2000) did not appear to negatively affect fragment survivorship, as tissue overgrew the wire within 30 to 45 days Most wire breakage and fragment loss occurred prior to the midcourse correction (23%), with detachment of