Oliver et al (2004) Monitoring bleaching

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Timed Swim Belt Transect LIT (video or manual recording) Permanent Quadrats (photo) Tagged colonies Can reliably distinguish between unbleached corals a and dead corals, and low coral cover from high cover Allows large numbers of site to be visited in a short time Provide relatively precise estimates of bleaching and major benthic categories Allows accurate counts per unit area of uncommon entities (useful if accurate measurements of bleaching needed when only a few colonies are affected) Enables size estimates of coral colonies to be made rapidly Provides accurate measurements of all benthic categories Close range of observat ions provides the highest taxonomic resolution Allows individual colonies to be repeatedly assessed. Provides accurate measurements of colony size and area Repeated measurements of bleaching and mortality can be made on the same colony Recurrence of bleaching in individual colonies (and hence resilience development) can be tracked between bleaching events Samples for physiological, genetic and biochemical analysis can be taken from colonies with a known bleaching history Less precise than timed swims due to speed of travel and distance to coral Less precise than measured values from LIT or photo-quadrats Less effective than aerial surveys or manta tow of covering large areas (can miss small areas of bleaching since only a limited number of sites can be surveyed) Not useful for obtaining accurate measurements of benthic cover Covers a small area – many replicates needed to sample a large area Transects take longer to measure (manual) or longer to analyse (video) Quadrats take long time to analyse from photos. Small spatial coverage per sample Relocating colonies can be difficult and time-consuming Large numbers of colonies for several species are required to obtain useful population level estimates of bleaching and mortality Questionnaires The utility of questionnaires as a first step in documenting a bleaching event has already been discussed. Questionnaires can be considered to be a special form of broad-scale survey. They are useful if • A large area needs to be covered • The event has already occurred • Many people visit the area that you are interested in • You only need data on distribution, severity and gross taxonomic susceptibilities for bleaching • You do not have the resources to carryout dedicated survey trips • You do not need the data to be very precise (i.e. it will not be used to detect small difference in bleaching severity between sites or years) The ReefBase summary questionnaire is provided in appendix xx Broad-scale Synoptic surveys Since most bleaching studies involve at least some interest in the question of how extensive coral bleaching is, broad-scale surveys are an excellent way of getting an overview of where bleaching is and isn’t occurring over scales which are relevant to managers. It is strongly recommended that all programs should have a broad-scale component. Fine scale or colony level monitoring can then be nested with in these areas using the results of the broader survey to ensure that the local sites are not anomalous compared with the larger area. For details on each of these procedures see the references. Aerial Surveys Aerial surveys are particularly useful for covering very large areas (>100km) in cases where bleaching is severe over at least some areas and the water is clear. If carried out during low tide, with less than 1 meter covering the reef flat then it can be useful even in re latively turbid waters. Aerial surveys provides data of lower precision and accuracy compared to other broad-scale methods, and should be calibrated with timed swim data or LIT data. This method involve the use of a high-winged aircraft which is flown at about 500ft along the perimeter of a reef with one or two observers recording estimated percentage of coral bleaching. A similar approach could also be used to repeatedly monitor a specific area by making regular observations from a fixed point on a hill overlooking a fringing reef. Bleaching should be recorded using the categories in Appendix 3, Table 8. Further details can be found in Berkelmans and Oliver (2000). 16
Recommended Manta Tows The manta tow technique is best used where the variables being measured (coral cover and % bleaching in this case) are easily detectable at a distance, vary considerably and unpredictably over short distances, and where the frequency of occurrence of the measured phenomenon is very low. In areas with low visibility the method is not appropriate, and timed swims should be used. This method is well described in English et al. 1997, and involves an observer on snorkel or SCUBA being towed behind a small boat at a fixed speed. The observer uses a flat board at the end of a tow rope to manoeuvre in such a way as to ensure a clear view of the reef surface. At fixed intervals the tow is stopped so that the observer can communicate to a recording person on the boat the levels of key variables observed during the tow. The major points to be considered are: • Choose the tow path to cover as much of the area under investigation as possible • Use standard AIMS method (2 minute tows) • Record standard AIMS variables (especially total coral cover: Appendix 3; Table 7) • Record coral bleaching characteristics including: o % of all live coral bleached (use scale in Appendix 3; Table 8) o top 5 coral families or genera bleached in rank order A sample datasheet is provided in Appendix 1, and data tables are available in Microsoft Excel and Access formats from ReefBase. Further details can be found in English et al. (1997). Timed Swims Times swims provide greater accuracy since the observer can spend more time in a particular area and get closer to the substrate to ensure optimal visual resolution . However preliminary manta tow surveys of an area which has not previously been visited, and about which nothing is known can be useful in developing an understanding of where coral is best developed and how community type varies over the entire study area. Since the timed swim method has not received as much attention in survey manuals for coral reefs, we present here a basic description of the method. At each site a diver should enter the water using scuba or snorkelling gear and then swim slowly along the reef for a period of two minutes, keeping with in the prescribed depth zone. In general, a distance of no more than 30m should be covered. Height above the substrate should be about 2m, but this may be varied depending on the visibility (high in clear water; lower in murky water). Closer distances should be used to verify identifications and coral condition where needed. Where possible 2 depth zones should be recorded: shallow and deep. The shallow site should include the reef crest and upper slope (if the sample is on the reef edge) from about 1m to 4m in depth. The deep site should include the mid to lower reef slope from 5-10m. Actual depths will need to be varied according to the coral community. In turbid environments, or areas with poor reef development, these depths may be shallower, while in very clear conditions they may be deeper. In areas with very restricted reef development, only the shallow depth zone may be present. In general snorkelling gear can be used to asses the shallow station. However if necessary due to the depths involved, or poor visibility, scuba gear should be used. Deep sites should be assessed on SCUBA. A team of at least three people should be used. One person should act as a boatman and record station details. Another person can use snorkel to assess the shallow zone, while the third person prepares scuba gear. Two divers should then enter the water to conduct survey the deep site, with one diver acting as the primary observer. The person snorkelling in the shallow zone should also be the primary SCUBA observer in order to minimize variability in the observations caused by different observers. The issue of inter-observer differences is addressed in more detail below. The same primary observer should record all the variables in the data sheet at the end of each 2 minute period. There are three sets of information to be recorded: Station information; general coral and bleaching observations; and detailed information for selected coral groups. These are listed in Tables 2, and 3. These tables should form the basis of a database on bleaching observations. An Access database has been created to accompany this protocol, and can be downloaded from www.reefbase.org/bleachingdatabase. 17
Page 1 and 2: Draft A Global Protocol for Assessm
Page 3 and 4: Introduction Coral bleaching occurs
Page 5 and 6: This protocol is designed to assist
Page 7 and 8: and easily, even if only part of so
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: • The initially random selection
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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