cc: jcole@geo.Arizona.EDU, sandy.tudhope@ed.ac.uk, k.briffa@uea.ac.uk, mhughes@ltrr.arizona.edu date: Fri, 11 May 2001 14:43:54 +0100 from: "Sandy Tudhope" subject: Re: comments? to: Keith Alverson Hi Keith et al., I've taken a quick look at the coral section, and have made some changes. I attach (and append below) a reworded version of the second coral paragraph (the one which starts "Unfortunately, many corals have been destroyed ....." in the first version). Specific comments include: 1. Worth pointing out that large corals (>100-200 years old) are relatively rare in most areas, and once the corals die, their skeletons are ofen rapidly removed by erosion, and the absolute chronology is lost. i.e., we can't simply find go and core 'dead' corals and expect to get the same results. 2. The issue about coral bleaching affecting the ability of corals to reproduce is a bit of a red herring in this context. We are more concerned with the potential death of the large living corals, rather than the fact that we may have fewer new coral recruits. 3. I've added a specific reference relating to the potential impact of global warming on corals and coral reefs. Hope this helps. Cheers, Sandy ______________ "Large living corals (>100-200 years old) suitable for climate reconstruction purposes are relatively rare in most reef areas of the world. Unfortunately, a significant number of these corals have been killed in recent years, and the outlook for many others may be bleak. ‘Local’ factors related to coastal development and population pressure (such as dredging for engineering works, dynamite fishing, siltation and pollution from coastal land- use changes) are taking their toll. However, perhaps more significant is the widespread mortality of corals due to coral ‘bleaching’ consequent on exceptional ‘warm’ climatic extremes. These extremes are often associated with El Niño events, and have been observed in all the world’s tropical oceans (Strong 1998). Coral ‘bleaching’ describes the loss of colour of reef building corals due to the expulsion of symbiotic algae (or loss of their photosynthetic pigments) from the coral tissue. The most common cause of coral bleaching is elevated sea surface temperature. Specifically, bleaching often occurs when local SSTs exceed their usual warm season maximum by >1-2 ºC for periods exceeding a few weeks. In some cases, other environmental factors such as low salinity or increased exposure to solar radiation are also implicated. Once bleached, the corals have lost a major source of their nutritional energy (which comes from their algal symbionts), have very limited ability to calcify, and, if the condition persists, the corals die. Major bleaching events associated with the 1982/83 and 1997/98 El Niño events caused mass mortality of corals in large areas of the equatorial Pacific, and western Indian Ocean. Even the corals that recover from bleaching may have reduced fecundity and reduced tolerance to future stress (Normile, 2000). The death of corals being used to reconstruct paleoclimate is not a theoretical problem – it is real. Once the corals die, the potential for climate reconstruction from the skeletons is severely reduced. The dead coral skeletons are prone to rapid physical and biological erosion, and the absolute chronology (a key factor in identifying leads and lags in the climate system) is lost. As one example, the Urvina Bay coral site in the Galapagos, the subject of several published investigations, was wiped out by the 1982/83 El Niño (T. Guilderson, personal communication). Some scientists predict a global demise of coral reefs within the next few decades due to global warming (e.g., Hoegh-Guldberg, 1999; Dawson et al, NOAA). An overview of areas thought to be susceptible to bleaching can be found at: psbsgil.nesdis.noaa.gov:8080/PSB/EPS/SST/clim&hot.html Hoegh-Guldberg, O. (1999). Climate change, coral bleaching and the future of the world's coral reefs. MARINE AND FRESHWATER RESEARCH, 50 (8): 839-866 1999). " __________________________________ Dr Sandy Tudhope Department of Geology & Geophysics, Edinburgh University, West Mains Road, Edinburgh EH9 3JW, Scotland, U.K. Tel: +44 131 650 8508 (direct) +44 131 650 4842 (Secretary) Fax: +44 131 668 3184 The following section of this message contains a file attachment prepared for transmission using the Internet MIME message format. If you are using Pegasus Mail, or any another MIME-compliant system, you should be able to save it or view it from within your mailer. If you cannot, please ask your system administrator for assistance. ---- File information ----------- File: bleaching.doc Date: 11 May 2001, 14:32 Size: 22528 bytes. Type: Unknown Attachment Converted: "c:\eudora\attach\bleaching.doc"