First Proof That Chemicals from Seaweeds Damage Coral on Contact

Field studies have shown for the first time that several common species of seaweeds in both the Pacific and Caribbean Oceans can kill corals upon contact using chemical means.

While competition between seaweed and coral is just one of many factors affecting the decline of coral reefs worldwide, this chemical threat may provide a serious setback to efforts aimed at repopulating damaged reefs. Seaweeds are normally kept in check by herbivorous fish, but in many areas overfishing has reduced the populations of these plant-consumers, allowing seaweeds to overpopulate coral reefs.

A study documenting the chemical effects of seaweeds on corals was scheduled to be published May 10, 2010 in the early edition of the journal Proceedings of the National Academy of Sciences (PNAS). The research was supported by the National Institutes of Health, the National Science Foundation, and the Teasely Endowments at the Georgia Institute of Technology.

"Between 40 and 70 percent of the seaweeds we studied killed corals," said Mark Hay, a professor in the School of Biology at Georgia Tech. "We don't know how significant this is compared to other problems affecting coral, but we know this is a growing problem. For reefs that have been battered by human use or overfishing, the presence of seaweeds may prevent natural recovery from happening at all."

Coral reefs are declining worldwide, and scientists studying the problem had suspected that proliferation of seaweed was part of the cause -- perhaps by crowding out the coral or by damaging it physically.

Using racks of coral being transplanted as part of repopulation efforts, Hay and graduate student Douglas Rasher compared the fate of corals from two different species when they were placed next to different types of seaweed common around Fijian reefs in the Pacific -- and Panamanian reefs in Caribbean. They planted the seaweeds next to coral being transplanted -- and also placed plastic plants next to some of the coral to simulate the effects of shading and mechanical damage. Other coral in the racks had neither seaweeds nor plastic plants near them.

The researchers revisited the coral two days, 10 days and 20 days later. In as little as two days, corals in contact with some seaweed species bleached and died in areas of direct contact. In other cases, the effects took a full 20 days to appear -- or for some seaweed species, no damaging effects were noted during the 20-day period. Ultimately, as much as 70 percent of the seaweed species studied turned out to have harmful effects -- but only when they were in direct contact with the coral.

To confirm that chemical factors were responsible, Hay and Rasher extracted chemicals from the seaweeds -- and from only the surfaces of the seaweeds. They then applied both types of chemicals to corals by placing the chemicals into gel matrix bound to a strip of window screen, forming something similar to a gauze bandage and applying that directly to the corals. To a control group of corals, they applied the gel and screen without the seaweed chemicals.

The effects confirmed that chemicals from both the surface of certain seaweeds and extracts from those entire plants killed corals.

"In all cases where the coral had been harmed, the chemistry appeared to be responsible for it," said Hay. "The evolutionary reasons why the seaweeds have these compounds are not known. It may be that these compounds protect the seaweeds against microbial infection, or that they help compete with other seaweeds. But it's clear now that they also harm the corals, either by killing them or suppressing their growth."

The researchers studied coral of different species in the Pacific and Caribbean, matching them up against different species of seaweed common to their geographic areas. The coral species chosen -- Porites porites in Panama and Porites cylindrica in Fiji -- are among the hardiest of coral, suggesting that other species may be even more dramatically affected by the seaweed compounds.

In the Caribbean, five of the seven seaweeds studied caused bleaching of the coral, while in the Pacific, three of eight species studied caused the effect.

The harmful chemicals affect only coral in direct contact with the seaweed, suggesting the compounds are not soluble in water, Hay noted. The effects -- which were measured through photographic image analysis and Pulse-Amplitude-Modulated fluorometry -- also varied considerably, with certain seaweeds showing stronger impacts than others.

Conducted during 2008 and 2009, the study adds new information about the decline of reefs worldwide, and reinforces the importance of maintaining a healthy ecosystem that includes enough herbivorous fish to keep seaweed under control.

"Removing the herbivorous fishes really sets up a cascade of effects," said Hay, who holds the Harry and Linda Teasely Chair in the Georgia Tech School of Biology. "The more you fish, the more seaweeds there are. The more seaweeds there are, the more damage is done to the coral. The less coral there is, the fewer fish will be recruited to an area. If there are fewer fish, the seaweeds outgrow the coral. It's a downward death spiral that may be difficult to recover from."

In earlier research, Hay and other researchers demonstrated that keeping fish away from coral reefs fuels the growth of seaweeds, and that certain fish are responsible for eating specific seaweed species. That information could help guide fisheries management by encouraging protection of fish that control the most harmful seaweeds.

"The most damaging seaweed in our study is eaten voraciously by one species of fish, and no other species will touch it," Hay said. "Now that we know that seaweeds can kill coral through these chemical means, it is even more important to understand which herbivores control which seaweeds so we can consider additional protections for these critical fish species, even outside of normal marine protected areas."

Seaweed to Tackle Rising Tide of Obesity

Seaweed could hold the key to tackling obesity after it was found it reduces fat uptake by more than 75 per cent, new research has shown.

Now the team at Newcastle University are adding seaweed fibre to bread to see if they can develop foods that help you lose weight while you eat them.
A team of scientists led by Dr Iain Brownlee and Prof Jeff Pearson have found that dietary fibre in one of the world's largest commercially-used seaweed could reduce the amount of fat absorbed by the body by around 75 per cent.
The Newcastle University team found that Alginate -- a natural fibre found in sea kelp -- stops the body from absorbing fat better than most anti-obesity treatments currently available over the counter.
Using an artificial gut, they tested the effectiveness of more than 60 different natural fibres by measuring the amount of fat that was digested and absorbed with each treatment.
Presenting their findings at the American Chemical Society Spring meeting in San Francisco, Dr Brownlee said the next step was to recruit volunteers and study whether the effects they have modelled in the lab can be reproduced in real people, and whether such foods are truly acceptable in a normal diet.
"The aim of this study was to put these products to the test and our initial findings are that alginates significantly reduce fat digestion," explains Dr Brownlee.
"This suggests that if we can add the natural fibre to products commonly eaten daily -- such as bread, biscuits and yoghurts -- up to three quarters of the fat contained in that meal could simply pass through the body.
"We have already added the alginate to bread and initial taste tests have been extremely encouraging. Now the next step to to carry out clinical trials to find out how effective they are when eaten as part of a normal diet."
The research is part of a three year project being funded by the Biotechnology and Biological Sciences Research Council. It addresses the new regulations set out by the European Food Safety Authority that any health claims made on a food label should be substantiated by scientific evidence.
"There are countless claims about miracle cures for weight loss but only a few cases offer any sound scientific evidence to back up these claims," explains Dr Brownlee.
Alginates are already commonly used at a very low level in many foods as thickeners and stabilisers and when added to bread as part of a blind taste test, Dr Brownlee said the alginate bread actually scored higher for texture and richness than a standard white loaf.
"Obesity is an ever-growing problem and many people find it difficult to stick to diet and exercise plans in order to lose weight," explained Dr Brownlee.
"Alginates not only have great potential for weight management -- adding them to food also has the added advantage of boosting overall fibre content."
What is a dietary fibre?
Dietary fibre would be scientifically classified as a group of carbohydrates of plant origin that escape digestion by the human gut.
"Actually, there's still quite a lot of confusion about fibre," says Dr Brownlee. "I think most people would describe it as roughage -- the bit of your food that keeps you regular and is vital for a healthy gut.
"Both of these facts are true but the notion that all fibre is the same and that it simply goes through your system without having an effect is wrong."
Fibre is made up of a wide range of different molecules called polysaccharides and although it is not digested by the human gut, it both directly and indirectly affects a number of bodily processes.
Dr Brownlee adds: "These initial findings suggest alginates could offer a very real solution in the battle against obesity."

In The Turf War Against Seaweed, Coral Reefs More Resilient Than Expected

There's little doubt that coral reefs the world over face threats on many fronts: pollution, diseases, destructive fishing practices and warming oceans. But reefs appear to be more resistant to one potential menace – seaweed – than previously thought, according to new research by a team of marine scientists from the United States and Australia.Their study is the first global-scale analysis of thousands of surveys of individual reefs – in all, more than 3,500 examinations of about 1,800 reefs performed between 1996 and 2006. The study appears the June issue of the journal Ecology, which is published by the Ecological Society of America."Until now, many scientists have concluded that the world's coral reefs are being overrun by seaweed," said John Bruno of the University of North Carolina at Chapel Hill and lead author of the study. "Our findings show that's not the case. Seaweed have taken over and are dominating some reefs, but far fewer than assumed."The problem with too much seaweed, researchers say, is that it can smother the baby corals, reducing the ability of reefs to recover from other disturbances such as hurricanes and disease outbreaks. Over recent decades, there have been several dramatic examples of such shifts, with one of the most widely known and striking cases occurring in the Caribbean in the 1980s. Following a series of events that disturbed the marine environment (including two major hurricanes, a disease outbreak and the loss of a seaweed-grazing urchin), coral cover on several reefs in Jamaica plummeted from about 70 percent to less than 10 percent, and macroalgae became the dominant life form.So Bruno, along with colleagues Hugh Sweatman from the Australian Institute of Marine Science and William F. Precht, a Florida-based marine ecologist, set out to determine how bad and how widespread the problem of seaweed-dominated reefs really is.The team came up with a "phase-shift index" to determine the state of each reef. Pristine reefs where coral was still abundant had an index number of -2 to -3, while areas where macroalgae have overwhelmed reefs' surfaces were given an index ranking of between 3 and 5.They found that while there were moderate local increases in seaweed cover over the study period, only four percent of reefs worldwide were dominated by macroalgae – that is, more than 50 percent of a reef's surface was covered in seaweed. Researchers also found overall "phase shift severity" decreased in the Caribbean, did not change in the Florida Keys and the Indo-Pacific, and increased slightly on the Great Barrier Reef due to moderate coral loss."Overall, our results indicate that there is no general recent trend (i.e., post-1995) toward marcoralgal dominance," the researchers wrote."The results from this study question many of the prevailing paradigms that coral reef ecologists have developed over the past two decades," Precht said. "These findings will change the way we view and manage these fragile yet resilient ecosystems."Said Sweatman: "I hope this study leads to clearer definition of what coral-algal phase shifts are and broadens our perspective on the serious loss of corals in many parts of the world. Australian reefs have been relatively lucky so far, but there is no reason for complacency."The study team noted that while their analysis suggests the threat posed by macroalgae has been exaggerated, individual case studies such as the degradation of Jamaican reefs have been invaluable warnings of the consequences of subjecting reefs to multiple natural and manmade disturbances.The study was funded by the National Science Foundation, the Australian Institute of Marine Science and UNC-Chapel Hill.

Even Seaweeds Get Sunburned

It is red, it burns and itches: a sunburn on our skin. However, too much sun is not only bad for humans. Many plants react sensitively to an increased dose of ultraviolet radiation, too. Yet they are dependent on sunlight. With the help of pigments absorbing solar energy and light, plants produce their vitally important building blocks by means of photosynthesis.

However, this has its limits: too much sun means an over-abundance of energy and thus the destruction of the sensitive pigments. The result are black spots, pale leaves and rotten parts.
Since algae cannot apply sun lotion like we do, they develop their own strategies to protect from the sun: "A species of red algae, for instance, produces under increased ultraviolet radiation less red light-harvesting proteins, thus decreasing the absorption of radiation. The typical red colour of the alga fades and the plant gets white tips.," explains Prof. Dr. Christian Wiencke, marine biologist at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association. "The algae additionally produce substances which react similar to melanin in human skins: mycosporin amino acids (MAA)." Melanin absorbs ultraviolet radiation and thus protects the human skin – at the same time, it gives a natural suntan.
The ozone layer usually absorbs the major part of the hard and harmful solar ultraviolet radiation of short wavelength. However, because of stratospheric ozone depletion, these dangerous rays increasingly penetrate to the earth's surface and therefore also to the seawater.
Extensive biological experiments are presently conducted on this complex of problems at the German French Research Base AWIPEV on Spitsbergen. "We examine the harmful effects of ultraviolet radiation on algae and their protective mechanisms," says Wiencke. The ultraviolet radiation particularly harms the algae's photosynthesis and their hereditary material. These organisms usually react with a decreased rate of growth or a reduction of reproductive success.
The spores and germ cells of the algae which drift through the water as unicellular organisms are particularly sensitive. Even small ultraviolet doses are damaging and inhibit their germination. "Our investigations show that the distribution of certain species of brown algae is inhibited by the climate of ultraviolet radiation. The algae are displaced into deeper water layers if ultraviolet radiation increases."
The research conditions on Spitsbergen are optimal for Wiencke and his colleagues: "We want to observe the development of marine coastal ecosystems in the face of global climate change. Not only an increased ultraviolet radiation plays a decisive role, but also the water temperature which has been increased by the greenhouse effect. This increase in temperature can particularly be felt on Spitsbergen, in the Atlantic sector of the Arctic."
Adapted from materials provided by Helmholtz Association of German Research Centres.

Seaweed transformed into stem cell technology

Engineers at Rensselaer Polytechnic Institute have transformed a polymer found in common brown seaweed into a device that can support the growth and release of stem cells at the sight of a bodily injury or at the source of a disease।

The findings mark an important step in efforts to develop new medical therapies using stem cells.
“We have developed a scaffold for stem cell culture that can degrade in the body at a controlled rate,” said lead researcher Ravi Kane, professor of chemical and biological engineering. “With this level of control we can foster the growth of stem cells in the scaffold and direct how, when, and where we want them to be released in the body.”
Kane and his collaborators, which include the author of the paper and former Rensselaer graduate student Randolph Ashton, created the device from a material known as alginate. Alginate is a complex carbohydrate found naturally in brown seaweed. When mixed with calcium, alginate gels into a rigid, three-dimensional mesh.
The device could have wide-ranging potential for use in regenerative medicine, Kane explains. For example, the scaffolds could one day be used in the human body to release stem cells directly into injured tissue. Kane and his colleagues hope that the scaffold could eventually be used for medical therapies such as releasing healthy bone stem cells right at the site of a broken bone, or releasing neural stem cells in the brain where cells have been killed by diseases such as Alzheimer’s.
Kane and his team encapsulated healthy neural stem cells in the alginate mesh, producing a three-dimensional scaffold that degrades at a tunable, controlled rate। Once the scaffold is implanted in the body, the researchers use an enzyme called alginate lyase, which eats away at alginate, to release the stem cells. Alginate lyase is naturally produced in some marine animals and bacterial strains, but not in humans.

In order to control the degradation of the alginate scaffold, the researchers encapsulated varying amounts of alginate lyase into microscale beads, called microspheres. The microspheres containing the alginate lyase were then encapsulated into the larger alginate scaffolds along with the stem cells. As the microspheres degraded, the alginate lyase enzyme was released into the larger alginate scaffold and slowly began to eat away at its surface, releasing the healthy stem cells in a controlled fashion.
The microspheres also can be filled with more than just alginate lyase. “We can add drug molecules or proteins to the microspheres along with the alginate lyase that, when released into the larger alginate scaffold, could influence the fate of the encapsulated stem cells,” Kane said. “By adding these materials to the larger scaffold, we can direct the stem cells to become the type of mature, differentiated cell that we desire, such as a neuron. This will prove very valuable for applications of stem cells in regenerative medicine.”
The findings are detailed in the December 2007 edition of Biomaterials. Kane and Ashton were assisted in their research by Professor David V. Schaffer of the University of California at Berkeley; Akhilesh Banerjee, a Rensselaer graduate student; and Supriya Punyani, a Rensselaer postdoctoral associate.
The research was funded with a grant from New York state.
Adapted from materials provided by Rensselaer Polytechnic Institute

Hawaii biologists fight invasive seaweed

Biologists fighting invasive seaweeds taking over Hawaiian reefs are using native sea urchins and fish to help control the aggressive plants. "If people can raise herbivore (plant-eating) stocks quite substantially, I believe it will have a big impact," said coral reef ecologist Ivor Williams of the Hawaii Coral Reef Initiative and the state Division of Aquatic Resources. In tests of weed-infested reefs in Kaneohe Bay, the tactic has been successful and gives hope that the state's coral reefs might be able to battle the plants."We have not had enough urchins to test them out on a whole reef, but in every experiment on a smaller scale, we saw that urchins stop infestations of alien algae to begin with, or prevent the re-growth of existing alien algae," said Eric Conklin, who conducted some of the urchin experiments and is now marine science adviser for The Nature Conservancy's Hawaii Marine Program.One aspect of a larger project will be matching each invasive seaweed species to the creature that enjoys eating them most.Grazing fish, such as manini, for example, are fond of the acanthophora seaweed troubling West Maui. But the fish don't have a taste for Kaneohe Bay's kappaphycus weeds, which are instead a favorite of collector urchins.The noshing sea life are expected to add to an invasive seaweed removal program that includes the mechanical Super Sucker and its smaller progeny Super Sucker Junior."Using the urchins (and herbivorous fish) in conjunction with the Super Sucker, that carries us through the next few years," Conklin said.In order for the project to work, however, officials will need to contend with a certain voracious, two-legged predator. People eat collector urchins, which have been so overharvested they can't keep up with the seaweed.Scientists at the University of Hawaii hope to release large numbers of urchins to restore overfished urchin populations. But they are still learning how to raise the prickly sea creatures in captivity.In other coral reef news, the Bush administration has announced that it has submitted legislation to Congress to reauthorize the Coral Reef Conservation Act of 2000 and to add protections for coral reefs and improving marine debris removal.