Boulder Island Coral Survey Project Manaia Phase one - Final Report Thor Jensen & Annika Dose January 2018
Content 1. Coral genera and their abundance in the bays of Boulder Island...3 2. Reef maps...5 2.1 Bamboo Bay...5 2.2 Boulder and Eagle Bay...6 2.3 Sister Bay West...7 2.4 Moken Bay...8 3. Transect data...9 4. Restauration trial: recycled fish traps...14 5. State of the reef...15 6. Recommendations for restauration and monitoring efforts...15 2
1. Coral genera and their abundance in the bays of Boulder Island Tab.1. Coral genera found around Boulder Island. The abundance is an estimate based on impression during multiple dives and not based on counts or scientific method with 0= not present, 1= present (at least 1 colony), 2= common, 3= very common and 4= dominant. Genus Growth form Sister East 3 Sister West Bamboo Bay Boulder Bay Eagle Bay Moken Bay Acanthastrea 0 0 1 0 0 0 Acropora br 2 2 2 2 2 4 Acropora pl 2 2 2 2 2 3 Alveopora 0 1 2 1 1 2 Astreopora 0 0 0 1 1 1 Coscinarea 0 0 1 1 0 0 Coeloseris n.a. n.a. n.a. n.a. n.a. 1 Ctenactis 0 1 1 2 2 2 Cyphastrea 1 0 0 1 1 1 Diploastrea 2 3 2 3 3 2 Echinopora br 1 1 1 1 1 1 Echinopora pl 0 5 1 1 1 1 Echinophyllia 0 0 0 1 0 0 Favia 1 1 1 1 1 1 Favites 1 2 1 1 1 1 Fungia 0 1 2 2 2 3 Galaxea 3 2 3 2 2 2 Gardineroseris 0 1 0 1 1 0 Goniastrea 3 2 2 3 3 3 Goniopora 1 1 1 3 2 2 Heliopora 1 2 1 3 4 5 Herpolitha 0 1 0 1 1 1 Hydnophora br 0 0 0 0 0 3 Hydnophora ma 1 1 3 2 2 2 Leptastrea 0 1 1 1 2 1 Leptoria 2 1 2 2 2 2 Lobophyllia 1 1 1 1 1 3 Millepora 1 1 1 1 1 1 Montastrea 1 1 1 1 1 2 Montipora br 3 3 3 2 3 2 Montipora en 5 3 2 3 3 2 Montipora pl 5 3 4 4 4 2 Oulophyllia 1 0 0 1 0 1 Pachyseris 0 2 1 1 1 2 Pavona col 0 0 0 1 1 0 Pavona ma 1 2 2 2 2 2 Pectinia 0 0 0 0 0 1
Physogyra 0 1 1 2 2 3 Platygyra 3 3 2 3 3 2 Plerogyra 1 1 1 2 1 1 Pocillopora 3 2 2 2 3 2 Porites br 4 3 3 3 4 2 Porites ma 4 4 5 4 4 3 Porites pl 0 1 1 1 2 2 Psammocora br 0 0 1 1 0 0 Psammocora ma 1 1 1 1 1 1 Psammocora col 0 1 1 1 1 0 Stylophora 0 0 0 0 1 0 Symphyllia 2 2 2 2 2 2 Trachyphyllia 0 0 1 1 0 0 Tubastrea 0 2 1 1 1 1 Turbinaria 0 0 0 0 1 0 Star Polyp 1 4 0 0 0 0 Merolina 1 1 0 0 1 1 Sarcophyton 0 4 4 4 3 2 Magnificent anenome 2 4 1 1 1 1 Clavelina 0 0 2 2 2 1 Lithophyton or Sinularia 0 0 2 2 2 3 Mat Polyp (Favia type SC) 0 4 0 0 0 0 4
2. Reef maps 2.1 Bamboo Bay Fig.1. Reef map of Bamboo Bay 1. Rubble and sand. Every artificial reef structure that is high enough to provide protection from the sand to coral fragments would be above the water line at low tide. 2-6. Located on big boulders. 2.Big boulders. Medium coral abundance and diversity. Many corals with approx. 15 cm diameter. High fish abundance. 3. High abundance of small Galaxea colonies. 4. High abundance of encrusting Porites. 5. Field of soft corals. 6. Huge Porites with branching fan coral. 7. No Boulders. Sand and rubble. 8. Not much. Some Porites and Montipora. 9. Boulders with some corals (many of approximately 15 cm diameter). Less diverse than similar spots at Eagle Bay or Moken Bay. 10. Boulders with corals. Huge Porites with plates. High abundance of corallimorphs. 11. Mixed habitat. Sand, soft corals, rubble, branching and massive corals. High abundance of corallimorphs and sea urchins (Diadema). 12. Big Porites. Small patches of coral accumulations. 13. Boulders with a diverse mix of corals and corallimorphs. 14. Sand. 15. Mix of sand, rubble and small patches of coral. 16. Field of rubble covered in coralline algae (+turf algae). 17. Edge. Boulders with high diversity of corals. Anemones, Fungia and Ctenactis. 5
18. Boulders with very diverse coral cover. 19. High abundance of encrusting Porites and soft corals. 20. Sand. Could be a good spot for structures. Location of big broken net (the position of the broken net and wood is an estimate and might be slightly off) and Xenia colony. 21. Boulders. Rubble with some corals, soft corals and corallimorphs. 22. Shallow water. Covered in rocks that provide a complex habitat. Diverse coral cover. 2.2 Boulder and Eagle Bay Fig.2. Reef map of Boulder and Eagle Bay 1. Massive Porites, Diploastrea or Symphhyllia with associates. Little patches of dead acropora, rubble, sand, zooanthids and corallimorphs. 2. Boulders with mixed large polyp stony corals (Favia, Favites, Goniastrea, Diploastrea, ) 3. Porites, massive and branching. 4. Barge. 5. Mixed corals on rocks. 6. Montipora. 7. Dead acropora. 8. Montipora, Porites, Goniopora. 9. Sand. 10. Softcorals. 11. Intertidal patch reef. 12. Mix 13. Sandy intertidal fields of Porites (massive and branching), Goniastrea, Heliopora and many other small corals. 14. Intertidal reef with tide pools and mixed coral cover. 15. Heliopora. 16. Dead acropora. Potential restauration area. 17. Montipora. 6
2.3 Sister Bay West Fig.3. Reef map of Sister Bay West In general: More Softcoral and Echinopora than in other Bays. A lot of rubble held together by corraline algae (not in the intertidal zone). Many dead corals that are covered in only a few small corals (no new recruits). Restauration: This bay is not recommended for restauration efforts. There are no big clear spaces that could be used for structures. Big dead corals offer space to attach corals with epoxy but there are no fragments lying around that could be used. Snorkeling: Special sights are the big Echinopora colonies and the anemones, aside from these the bay is less interesting than other bays. 1. Anemones. 2. Rubble, high abundance of schooling fish. 3. Boulders. Big Diploastrea and Symphyllia. 4. Sand and rubble covered with algae. Fungia. 5. Softcorals. Tubastrea on underside of rocks. 6. Patches of light and dark blue anemones. 7. Rocks with few corals. 8. Tubastrea on the underside of rocks. 9. Huge patches of Echinopora. 10. Sand, rubble. 11. Accumulations of rubble. 12. Huge Porites. 7
13. Rocks with branching corals, Galaxea, Corallimorphs and anemones. 14. Rubble, Porites, leather coral. 15. Medium coral coverage on rocks. Pocillopora and massive corals. 16. Heliopora, cead and alive. 17. Mix of sand and bis coral skeletons.!8. Sand and rubble. 19. Patches pf Echinopora and a few big rocks. 20. Not much on rocks, mostly barnicles, small Porites colonies and corallimorphs. 21. Sand and rubble. Some Porites that are covered with tables of Acropora. 22. Some massive coral skeletons. Patches of leather coral. Mostly rubble and sand. 23. Sand. 2.4 Moken Bay. Fig.4. Reef map of Moken Bay Very good for snorkeling and diving. Points of interest for tourists 6,7,10,11 and cages. *Artificial reef structure: cages 1. Intertidal patch reef, many small massive corals. 2. Unexplored, but most likely similar to 1. 3. Huge fields of Heliopora. Big interconnected colonies with many anemones and echinoderms inside. 4. Small large poly stony corals (many recruits of approx 1-4 years). 5. Heliopora and Acropora. 6. Highly diverse field of Acropora. Different species and growth forms. 7. Sand patches. 8. Borders of sand patches extremely diverse. 9. Branching Hydnophora and large Lobophyllia colonies. 8
10. Massive Porites or Diploastrea colonies with many diverse small corals on or around them. 11. Acropora and small large polyp stony corals (many recruits 1-4 years). 12. Deeper patch reef. Areas of Plerogyra, Physogyra, Symphyllia, Lobophyllia,Echinopora, Diploastrea and Porites separated by sand. Gigh Fungiid diversity and abundance (Fungia, Herpolitha, Ctenactis, Polyphyllia). 3. Transect data To gather the transect data a wooden square of the size of one square meter and four crossbeams (creating 9 smaller squares) was used. It was deployed onto the reef at the respective starting point of the transcect and photographs were taken of the complete square as well as each small square and close-ups of coral colonies within the square. A 4m long rope with heavy corals attached to its end was used to measure the distance to the point at which the square would be positioned next. For all transect lines the direction was straight to the beach from the starting point. Pictures were analysed post dive and each identified coral colony was assigned a percentage of the covered area within the square (small square 11%, whole square 99%). Categories included were all coral genera according to table 1 of this report and zooanthids, corallimorphs, turf algae, coralline algae, sand, (hair algae, macro algae, rubble, encrusting sponge, solitary sponge, Lobophytum, Litophyton)(with those in brackets and uncommon coral genera not being included in the following graphs). Transect Line 1: Boulder Bay West Starting point: Anchor Depth: 10.2m Fig.5. Location of the first sample area of transect 1. 9
Transect Line 2: Boulder Bay Central Starting point: Concrete block (directly next to the block, north side); Depth: 12.5m Fig.6. Location of the first sample area of transect 2. Transect Line 3: Moken Bay Starting point: south of the big boulder at the east coast of the bay Fig.7. Location of the first sample area of transect 3. 10
Fig.8. Seafloor coverage at transect line 1 in Boulder Bay. Fig.9. Seafloor coverage at transect line 1 in Boulder Bay (additional data). 11
Fig.10. Seafloor coverage at transect line 2 in Boulder Bay. Fig.11. Seafloor coverage at transect line 2 in Boulder Bay (additional data). 12
Fig.12. Seafloor coverage at transect line 3 in Boulder Bay. Fig.13. Seafloor coverage at transect line 3 in Moken Bay (additional data). 13
4. Restauration trial: recycled fish traps The fish traps were collected from different beaches where they washed ashore. The plastic bottles and inner part of the trap were cut out and any additional rope was removed. The empty cages were deployed onto a large sand patch in Moken Bay and positioned only a few meters apart. Cages were filled with large rocks and boulders und remaining spaces were filled with rubble. Broken-off coral fragments that lay loose in the sand were collected and attached to the cages. After a couple of days fish were abundant around the structures and after a couple of weeks there were the first invertebrates to be found in and on the cages. Maintenance: It is recommended that future project participants check the cages for damage and rocks that might have fallen out. If necessary, the structures can be cleaned of algae with a brush. If any big free spaces occur within the cages it is recommended that these are filled with rubble so that bigger fish do not try the get into the cages as they might get caught in the net. If the cages prove to be successful more coral fragments can be attached and more cages can be added to the structure. Fig.14. Artificial reef structure made out of recycled fish traps. 14
5. State of the Reef Overall the reefs in all bays are currently in a very healthy state. There were barely any signs left of the last bleaching event and it seems that the reefs have fully recovered. Damage to the reefs that could still be seen stem from previous disturbances. These are circles of broken coral that were most likely caused by dynamite fishing and trenches in the reef that resemble a path made by a heavy anchor dragged over the reef. The latter is in most cases only visible because there are distinct lines of very small corals in the middle of a reef that is much older and consists of bigger coral colonies. It seems that these areas are reclaimed by corals and will leave no permanent damage. The scars left behind by dynamite fishing on the other hand are much clearer and while on some small parts of them there are some new recruits or the surrounding coral colonies spread into the area, big parts of them are still not restored. The last reports of dynamite fishing around the island date back to almost ten years, leading to the assumption that reef destruction caused by dynamite fishing is much more severe and takes the reef longer to recover. There are no signs of current dynamite fishing and reports that date back these activities to more 8 years ago are believable. 6. Recommendations for restauration and monitoring efforts As the reefs were in a very healthy state with clear signs of recovery (new striving recruits) in places where the reef had been damaged there is, at this point, no urgent need for restauration efforts. It is recommended that the data collection on the transect lines be repeated (with a methodology similar to the one used in this study) regularly to monitor possible changes in the state and health of the reefs. It is proposed that the monitoring is extended to the other bays of the island. This way a degradation of the reef can be detected early and restauration efforts can be started. For right know we recommend to focus on education. The many different restauration structures can be installed around the island so that they are visible to visitors whilst diving or snorkelling. Additionally, there should be written explanations of restauration techniques and their purpose available in the common area and ideally the English speaking staff would know a little about coral restauration too. The type of tourist that comes to Boulder Island is most likely appreciating nature and thus probably eager to learn more about reefs and what can be done to protect them. This is a great way to spread some knowledge while adding another aspect to the tourists stay on the island and thus enhancing their experience. 15