|
||||||||||||||
|
|
||||||||||||||
|
Soft Corals Shrug Off Poor Image Soft corals have never taken top billing on the world stage of coral
reef science.
Dr. Katharina Fabricius, a marine ecologist from Germany, has spent six years researching these animals in an effort to better understand their nutrition, population dynamics and community structures. Katharina, a scientist with the CRC Reef Research Centre Ltd in Townsville since 1995, is working in conjunction with Dr Terry Done and other scientists from the Australian Institute of Marine Science. "I am directing my current study to look at soft corals in the context of the whole reef community" she said. Some problems have previously prevented the scientific study of soft corals from becoming a major area of research. "Many of them can only be identified at the species level under a microscope and with only five taxonomic experts operating at this level worldwide field work becomes somewhat difficult" says Katharina. She has adopted a rather unconventional approach directing research to the broader genus level looking at larger questions of where soft corals fit into overall reef ecology. As soft corals may comprise anywhere between 5% and 80% of total reef cover there is obviously an important need to explore general relationships between these animals and reef ecosystems. In particular many aspects about their growth rates under varying environmental conditions are still to be established. While several soft coral species provide fast growing colonies, many others are likely to live for several decades - some more than a hundred years. "These corals are animals but they also contain algae (zooxanthellae) in their tissues therefore being somewhat reliant on light" says Katharina. However it has been demonstrated that many soft corals are very inefficient at photosynthesis. As the carbon gain through photosynthesis is quite low they largely depend on additional food intake with the main source being small algae suspended in the water. This discovery received considerable attention around the world as it had previously been assumed that these animals were in most ways quite similar to hard corals. Katharina is quite amused over the common categorisation of hard corals as the 'good guys' - the reef builders, and soft corals as the 'bad guys' - invaders of disturbed areas. As very little is known about the part these soft corals play in the ecology of reef systems this stereotype may have developed somewhat prematurely. "We now know they have an important role in reef ecology, contributing to diversity, providing food to some animals and comprising a vital part of reef trophodynamics where they filter particles from water into the reef system" says Katharina. She argues they also play a significant part in providing aesthetic experiences for divers and reef visitors, a role that is often undervalued. One example is the large, colourful 'fan corals' which regularly feature in magazines and tourist advertising to represent spectacular reef environment. Scientists have debated whether soft corals might retard or prevent recovery in disturbed reefs as their toxins can impede resettlement by other marine organisms. On mid and outer-shelf reefs damaged by Crown-of-thorns outbreaks, Katharina was able to show that soft corals do not change in abundance after hard corals have been removed. "The soft corals could not utilise the empty spaces left after the starfish outbreaks and the hard corals actually re-established much faster, at least in shallow waters" said Katharina. Soft corals also seem to be highly dependant on having favourable physical conditions before colonies will flourish. Population growth appears to be adversely affected by low water flow, high wave energy and steep slopes. Katharina is now directing her attention to near-shore reefs such as those around the Palm Island group where the relationship of soft corals to the reef ecosystem may be more influenced by human factors. "We are currently looking at connections between water quality and soft coral abundance" says Katharina. Terrestrial run off loaded with sediment, nutrients or effluent promotes phytoplankton blooms in coastal waters while salinity levels and turbidity further stresses the reef ecology. Hard corals may struggle to survive in an environment such as this and Katharina suspects that many soft corals may experience a selective advantage, possibly due to increased food availability or simply by being very persistent. Therefore a change in water quality caused by coastal run off could mean a takeover by soft coral colonies in certain near-shore reefs. Katharina's work will try and establish under what conditions this can occur and consequences for subsequent reef growth. Recently, soft corals have also been under attention from biochemists. Scientists, hoping to discover new chemical substances with properties suitable for pharmaceutical drugs, have collected marine organisms from around the world. Of those screened, soft corals have shown much promise for medical science. Katharina says because of this potential drug researchers "are crazy about soft corals". While not directly involved with this research, her work may soon be called upon if soft corals are to be cultivated for this purpose. "They may eventually be farmed and I can tell biochemists where soft corals grow best and what conditions they like" said Katharina. Katharina believes her work on "bentho-pelagic coupling" (the relationship between what is in the water and what grows on the reef) will help identify and provide direction for future research needs. While applied research is the mandate for the Cooperative Reef Research Centre, Katharina's work exploring relationships between major components of reef systems is a necessary first step before more specific areas of study can be undertaken. Groundbreaking studies such as this are helping us to better understand the overall reef setting before we begin to explore each individual part. It seems most likely that even the 'bad guys' have an important part to play in the overall reef ecology. By Michael Cuthill |
