HKU Bulletin November 2006 (Vol. 8 No. 1)

8 9 Coral Colonies Farmed in Tanks Breeding innovation could reduce pressure on wild coral and restore damaged habitats. U niversity scientists have successfully bred coral in tanks, a development that could lead to the rehabilitation of degraded coral habitats and reduce pressures on the species by providing safe and steady supplies for research and the aquarium trade. Currently coral is harvested from the wild, which can quickly deplete colonies in relatively small habitats such as Hong Kong waters. It also limits the possibilities for carrying out multiple and repeat experiments on coral. Dr James True, Postdoctoral Fellow in the Department of Ecology and Biodiversity, has developed a system whereby coral harvested from the sea is attached to aragocrete, made from an aragonite sand which has a crystal form as coral skeletons, and kept in large outdoor tanks. Clean, recycled seawater is pumped through the tanks and light exposure is controlled. The corals are also given plankton to supplement their diet. Since the system was set up earl ier this year the 22 harvested coral fragments have thrived, defying common wisdom that coral is difficult to grow without the infrastructure available to large aquarium operators. “It’s always been said that coral is hard to keep, particularly in Hong Kong, because of water quality issues and the need for spectral lamps to help photosynthesis. Shops in Mongkok sell coral but maybe one in 10 can survive a year,” Dr True said. “I’m hoping to dispel that myth. We’re taking an unusual approach by combining fairly high-level science with low technology and energy use to achieve a minimum sustainable footprint, and we’re getting good results.” The parent colonies form coral in his tanks, propagate new coral clones that can be used in experiments. In one experiment Dr True has placed corals in two tanks, one filled with seawater that is filtered through toxic mud from Tolo Harbour and another filled with clean, fresh seawater. Some of the Tolo coral started to bleach after about four weeks, a sign they were having difficulty coping with the toxic environment. “One thing we want to find out is whether there are some genetic or physical limitations on coral forming reefs in Hong Kong. There are no reefs here but at this latitude you have reefs in a lot of other places in the world,” he said. “By exploring the best ways to grow and propagate coral under controlled Hong Kong conditions, we can gain significant insight into ways to rehabilitate or improve degraded habitats.” Dr True said his findings and success in breeding coral could be repeated in experiments elsewhere in the world, and he has already initiated a collaborative experiment with Thai researchers. Shopkeepers in Mongkok may also benefit by being able to secure a more reliable, ecologically safer source of coral for their customers. Paradox of Obesity New research shows that obesity is bad at any age. W e all know that being overweight is bad for our health. But what is surprising is that the theory only appears to apply to the young. Studies have shown that being fat poses no threat to the old. In fact, some researchers suggest that obesity is apparently protective in older people and that having a low Body Mass Index (BMI) may be associated with a shorter life expectancy. If you are confused by this data, then you are not alone. And with this in mind a team of researchers, in the University’s Li Ka Shing Faculty of Medicine, set out to explain this strange paradox and investigate its implications for healthcare in Hong Kong and Mainland China. Researchers from the Department of Community Medicine and School for Public Health teamed up with the government’s Elderly Health Services to conduct an innovative study to analyse the effect of BMI on mortality in older people. The idea was that BMI in older people might be an indicator of poor health and low fitness, in which case the relationship between BMI and mortality would vary with differing states of health. Chair of Community Medicine Professor Lam Tai Hing and his team traced 54,088 adults of age 65 and older, who enrolled in the 18 Elderly Health Centres, run by the Department of Health (Dr W.M. Chan), between July 1998 and December 2000. Research Assistant Professor Dr Mary School ing and Professor Gabriel Leung analysed the data by dividing the subjects into different health states, using an index of health problems including chronic illness, frailty, health service use, unintentional weight loss and smoking status. What the team found was that physical activity was usually protective but also that subjects with a higher BMI had a lower risk of death. However, these results changed substantially when each health status group was examined in turn. Obesity was then found to have a very different effect on each group. For those in the healthy group, who had never smoked and suffered no other health problems, being obese posed a 54 per cent higher risk of death, compared to people of normal weight. However, in the poor health group obese people had a 45 per cent lower risk of dying compared to people of normal weight. Dr Schooling concluded: “Research suggesting that being overweight is not a risk factor for mortality is biased. Fatness is always detrimental to health and increases the risk of death. But BMI may represent not only fatness in older people but also the severity of a disease and closeness to death. “This might mask the true relationship between fatness and mortality in older people, which cannot be understood without considering their underlying health state”. Dr Chan of the Department of Health emphasized: “On the other hand physical activity is beneficial to health and reduces the risk of death even for older people in poor health.” So in an older person BMI is difficult to interpret. Alternative body fat measurements such as waist circumference or waist- to-hip ratio may be more reliable, and some previous studies might be flawed, according to Professor Leung. In terms of public health, Professor Leung said, intervention to combat obesity at all ages is urgently needed. “Obesity could become an overwhelming problem in Hong Kong and Mainland China,” Professor Lam added. “So this research is of particular relevance to the Mainland with its rapidly ageing population. We have only a narrow window of opportunity in which to take action before the obesity epidemic spreads, and before the costs associated with obesity-induced illness overwhelm scarce healthcare resources.” The study’s results were published in the international medical journal Archives of Internal Medicine . RESEARCH