Oliver et al (2004) Monitoring bleaching

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After onset of bleaching is observed (during peak of bleaching) • Carry out extensive manta tow and/or timed swims to determine the extent/severity/variability of bleaching. • Determine if exiting sites adequately represent the areas bleached. If not add additional sites to cover a range of levels of bleaching intensity • Carry out belt transects (or LIT if the bleaching is very frequent) to get accurate estimates of % of corals bleached at different levels of intensity • Record condition of all tagged corals. If there is not a reasonable number of bleached corals at each site (at least 10) then additional bleached corals should be tagged ant their condition recorded. There is a great deal of additional work that could be done on these tagged colonies (zooxanthellae counts and genetics, PAM fluorometry, reproductive studies). These might be carried out by interested researchers at major Universities without much additional cost other than collection time. Further monitoring during and after bleaching • Repeat synoptic surveys (manta tow or timed swims) at regular intervals. Suggested optimal regime would be at , 2 months, 6 months, 12 months and 24 months after initial bleaching. Full post-bleaching LIT surveys should be repeated once bleaching is not longer present and all corals have either died or recovered. If resources permit, further recovery LIT surveys using should be conducted annually or every two years. Sampling Design Considerations Deciding on the Spatial and Time Scale For simple logistical reasons it is important to decide on the total area over which you wish to monitor bleaching, and the overall time frame during which you will be monitoring. Given a fixed budget and resources, larger spatial and time scales will usually mean less frequent, and fewer (less closely spaced) samples. If you want to monitor a large area you will probably not be able to detect small scale differences in bleaching pattern, and if you want to monitor for an entire year or for 5 years, then you will probably be restricted to sampling at periods of 1-2 months and may not be able to detect the exact timing of bleaching onset, recovery or mortality. These trade-offs needs to be carefully considered, and choices should based on the specific issues which are important to you (as discussed in Step 1). Before selecting a specific survey method, sampling sites and sampling frequency, it is important to decide on the area over which you wish the program to be able to draw conclusions. Is the program supposed to describe bleaching impacts globally, for a particular country, a single reef, or a single site within a reef? Deciding on the number, location and frequency of surveys (samples) is one of the most important and difficult steps in a monitoring program. A clear understanding of the questions and the time a spatial scales in which they will be addressed is crucial to the design of an effective sampling strategy. Some general guidelines are provided below, however it is recommended that professional assistance is sought in designing and sampling program and associated statistical analysis, especially if substantial resources are to be invested in the monitoring. Site and Sample Selection A basic question which most monitoring programs will address is: what it the ext ent and severity of the bleaching? In most cases the area over which this question is being asked is very large (10’s to 100’s of kilometers or more), and thus sampling will need to cover as much of this area as possible, yet still obtain sufficient quantitative information on specific variables to examine differences in intensity and ecological impacts between sites. In such cases a nesting of sample locations and survey methods is recommended. For instance, manta tow surveys could be used to obtain estimates of bleaching over the entire area, while more detailed replicate line transects could be carried out at specific sites, nested within locations around the entire area. 12
Sites within a Location Locations within an area Replicate Transects within a Site In choosing sampling sites, all available information on where bleaching is likely to occur or is known to occur should be used, together with information on known distribution of reefs and coral community types. Thus a variety of sources should be used to identify areas of important coral reef development, and areas with differing physical influences on community structure such as sediments, exposure to waves, currents and urban pollution. The following sources should be used in developing background information on reefs, and physical influences prior to selecting any sites. o o o o o Satellite mapping Aerial photos Nautical charts Local knowledge Manta tow surveys The primary purpose of site selection is to ensure that samples adequately represent the general area of interest as outlined in the discussion of spatial scale (see above). This allows any conclusions based on these samples to be applied to the whole area. If you cannot adequately sample the whole area of interest, consider restricting the study to a smaller area, bearing in mind that you will not be able to draw conclusions regarding bleaching in any excluded areas. Because coral bleaching can occur over a wide geographic area and because it is known to vary from one place to another, it is important to record from as many different sites as possible. Sample sites should be selected within areas known to have well developed coral communities and should be more numerous in areas known to be highly variable (and thus less numerous in areas known to be very similar in both community type and physical environment). One way to allocate surveys would be to decide, on the basis of time, staff resources, logistics and funding, how many surveys it is feasible to conduct and then to allocate these evenly along the entire area to be sampled. This scheme should then be adjusted to cover areas known to be highly variable with a few extra samples, taken from those areas which are highly uniform. Another way would be to choose an inter-sample distance which is likely to capture the spatial variation in coral communities and bleaching, and to then apply this interval to the whole area. If this results in a program which is too expensive or time consuming, the number can be adjusted accordingly. Both of these methods assume that there is some prior knowledge of the area, which could come from existing surveys and an analysis 13
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: Monitoring for different scenarios
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

Oliver et al (2004) Monitoring bleaching

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