Oliver et al (2004) Monitoring bleaching

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sediment is a sign of mortality. Algae rapidly colonise dead coral surfaces, so if there is a thin film or haze of green, brown or yellow this is also a sure sign that the coral is dead rather than bleached Figure 5. For some fleshy corals you can detect the presence of live tissue by gently touching the coral surface. Bear in mind that bleached corals may ultimately die, and so dead colonies may be a final stage in the bleaching process. However dead colonies can also result from disease, sudden weather events (especially flooding), pollutants, and predation, so if your first observation is only of large numbers of recently dead corals, you may have to look for other evidence to determine if this has been caused by bleaching. Two common causes of non-bleaching related, recently dead corals can are crown-of-thorns starfish (COTS) and disease. The visually diagnostic features of areas affected by COTS and disease (Figure 6) are set out below. Mortality due to COTS • In low to moderate levels of infestation, COTS and other predators such as the snail Drupella, leave discrete patches of dead white skeleton (feeding scars) which can look like bleaching. Major outbreaks can leave quite large contiguous areas of dead white coral. • Often there is a combination of recent scars (completely white) and progressively older “dirty” scars with a coating of sediment or algae. • If you see any COTS in the area (look among and under corals), you should immediately suspect them as the cause of any apparent coral bleaching, especially if the white or dead coral is patchily distributed • COTS scars can also be distinguished from bleaching damage by the strong transition from dead to live tissue within an affected colony Mortality due to Disease • Disease usually starts at one point and slowly spreads across a colony leaving dead and progressively older “dirty” skeleton behind it. It can form circular patches or curved bands across a colony • The disease front is often a distinct band with a specific colour (black, red, white) • Spotty white patches can be found in diseased corals but this is not a feature of bleached corals Appearance of corals in a bleaching event • Colonies turn pale and bleach evenly over the whole colony or on the upper surfaces. Totally bleached colonies appear exceptionally clean and almost gleam underwater (Figure 7). When bleaching is moderate to severe and the water is fairly clear, whole reef surfaces appear white from above the surface and even from the air (Figure 8) • Partly bleached colonies appear very pale and there is usually a gradual change between the paler and the darker parts of the colony. The upper surfaces are often the first, and sometimes the only parts to bleach (Figure 9). • On very close inspection you can often see the transparent tentacles of living polyps when the colony is viewed from the side • There is never a distinct line between bleach and unbleached parts of a colony • In the early weeks and months of bleaching, colonies will remain bleached, or get even whiter over periods of days and weeks. On the other hand, colonies killed by COTS or disease will become covered in sediment and algae in just a few days • Healthy, fast growing corals (especially Acropora species) will often have pale or white growing margins or branch tips. This is a sign of active growth and should not be confused with bleaching. While bleaching can also affect the upper surfaces of a colony only, the loss of zooxanthellae will extend further down the branches beyond the growing tips. How do I measure or quantify coral bleaching? The most common way to quantify the level bleaching is first to determine the percentage of the reef surface which is covered by corals and soft corals, and then to record the percentage of this cover which is bleached. This can be accomplished by visually estimating the two measurements, or by using one of several techniques to accurately measure bottom cover (line or point measurements, direct area calculations from images). In areas where bleaching is well developed, and coral surfaces tend to be either normal (“unbleached”) or completely white (“bleached”), this method can yield results quickly 6
and easily, even if only part of some colonies is bleached. However in cases where bleaching is mild, or is just beginning to occur, many colonies may be paler than normal, rather than completely white. In these cases a second category of “pale” can be added to the previous “bleached” and “un-bleached” categories. Some care and experience is needed with this category, since healthy corals in some clear, well lit environments can normally be very pale, even though this same colouration would be indicative of significant stress in areas where corals are normally darker brown in colour. Even experts have been known to mistake healthy corals for bleached ones in areas they have not previously visited. If in doubt just use the bleached and unbleached categories. The most basic form of bleaching data consists of a visual estimate of the percentage of total living coral cover (hard and soft corals) which is bleached. This can be base on rapid surveys or casual observations during visits to a reef. More accurate and precise methods, and a more structured way to carry out surveys are discussed below, but at a minimum the percentage of bleaching should be categorized into one of 5 levels to form a bleaching index which can be compared consistently between locations anywhere in the world, and between different years (see Appendix 3, Table 8). The NOAA/ReefBase Bleaching Questionnaire ReefBase and NOAA have jointly developed an online and hard copy form which allows users to record their observations of coral bleaching, and to store them within the ReefBase database (www.reefbase.org/input/bleachingreport/index.asp). The bleaching questionnaire fulfils two important functions. First it provides basic information on the basic aspects of the bleaching event in a standard format which is stored on a global database so that the information can be shared with other research worldwide and used to investigate global bleaching patterns. Second it can be distributed to other people in your area to gain additional information of the distribution, severity and basic characteristics of the bleaching event without having to dedicates special resources to additional survey trips. The questionnaire in its basic form can be downloaded form the ReefBase website as an Word Document (rtf format) and either emailed or distributed in hard copy form to other reef users in the area. Further details can also be included on the web-based bleaching forms. It is important to follow up and collect questionnaires from users, rather than having them send their results to ReefBase. That way you can first examine the information in raw format and immediately follow up on any interesting results. It also enables you to check the questionnaires for any errors. The completed forms should then be sent to ReefBase. If you are in Australia, the Great Barrier Reef Marine Park Authority also has an online questionnaire that can be used. The summary ReefBase questionnaire is included in Appendix 4. What do I do if I see bleaching? The box below sets out a series of steps to follow if you sea bleaching. 1. Record your observation and fill out a NOAA/ReefBase Questionnaire (www.reefbase.org/input/bleachingreport/index.asp). 2. If bleaching is widespread or severe, send out a message on coral-list to advise others 3. If you cannot fill out most of the basic information in the questionnaire, consider returning to the site as soon as possible for a reconnaissance visit to get additional general information. Ask around and get other people who regularly visit the reef to indicate if they have seen bleaching and where. Get them to fill out a ReefBase/NOAA Questionnaire – or make a note of these observations yourself and send to them ReefBase 4. Ask yourself why you are interested in this event. If you are not interested in formally answering the above questions (or any others you can think of) then continue to record the basic information on the Questionnaire and send it to ReefBase. 5. If you want to formally answer questions similar to those in step 4, then you will need to design a monitoring program (see below). 6. If you decide to implement a monitoring program, choose the methods and sampling protocol that best suits the questions you wish to answer, and the resources you have available to you; or pick a scenario that come closest to your situation and either follow the protocol suggested there, or modify it to suit your situation 7. Take photographs to illustrate conditions that you see, and any unusually features. If using digital camera, try to use at least 3 megapixel. 8. Store your data in a safe place and then share it with others by publishing it yourself or sending summary data to ReefBase 7
Page 1 and 2: Draft A Global Protocol for Assessm
Page 3 and 4: Introduction Coral bleaching occurs
Page 5: This protocol is designed to assist
Page 9 and 10: which has very poor power to answer
Page 11 and 12: Monitoring for different scenarios
Page 13 and 14: Sites within a Location Locations w
Page 15 and 16: • The initially random selection
Page 17 and 18: Recommended Manta Tows The manta to
Page 19 and 20: Anchor damage: Pictures: Comments:
Page 21 and 22: Buddy: Vessel: Depth: Replicate: Be
Page 23 and 24: Colonies can be tagged using large
Page 25 and 26: Appendices Appendix 1. Data Forms S
Page 27 and 28: WWF Bleaching Monitoring Program Ti
Page 29 and 30: major effect not only on coral cove
Page 31 and 32: the event. Electronic salinity logg
Page 33 and 34: mainly for landscape/seascape conse
Page 35 and 36: Table 10. Benthic codes Level 1 Lev

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