Stereotypical resting behavior of the sperm whale

by side. Conservation measures must thus work to ensure that on balance growth outpaces destruction, and that the natural ability of reefs to recover from disturbance ('resilience') is maintained. To date, marine protected areas have been the focus of most attention. Conspicuous successes include placing about one third of the Great Barrier Reef in no-take zones, and protection of the Northwest Hawaiian Islands. Marine protected areas do result in the rebound of most fish populations, and although documentation of the positive effects on corals is as yet more limited, there are promising signs. However, globally less than 2% of coral reefs are largely protected from fishing, and even these are often threatened by poor water quality. Moreover, localized protection alone cannot save reefs. In developing countries, traditional management schemes may be more effective given socioeconomic constraints, and management of reefs outside marine protected areas is also clearly critical, with improved land-use and protection of herbivores being top priorities. Techniques for restoring reefs are being developed, but they are necessarily small in scale and expensive, and will only work if the original causes of decline have ended. Given that even the best scenarios for reducing CO 2 emissions suggest substantial and rapid deterioration of the physical environment, improvement in local conditions coupled with action to reduce global threats are essential if reefs are to survive into the next century. Protecting and restoring these ecosystems are thus among today's biggest environmental challenges. Reefs are not only of scientific interest — they provide many ecosystem services and are critical components of the economies of many (mostly developing) countries — tourism, fisheries, and coastal protection being the most prominent. Success will depend on collaborations between natural and social scientists — we need to know not only what kills coral reefs, but also their economic value to people. balance between coral and microbial associates. Oceanography 20, 58–8. Hoegh-Guldberg, O. et al. (2007). The carbon crisis: coral reefs under rapid climate change and ocean acidification. Science, in press. Figure 3. A partly bleached coral. The coral is still alive, but the polyps in the bleached parts have lost their symbiotic algae. Photo courtesy of David Kline. Though very little is known about sleep in wild cetaceans, toothed cetaceans in captivity sleep with one side of their brain at a time []. Such uni-hemispheric sleep is thought to enable swimming, voluntary breathing, predator avoidance and/or social contact …