The Smithsonian’s National Zoo has become the first in the zoo and aquarium community to use coral larvae settling techniques to successfully grow two species of anemones—an accomplishment that will provide the Zoo a unique opportunity to learn how anemones grow.
“We have many questions about how to care for these animals as they grow from larvae to adults,” said Mike Henley, an animal keeper at the Zoo’s Invertebrate Exhibit who applied the technique to the anemones after they had spawned. “The oceans are not an infinite resource and so anything that we can learn about the captive management of coral and anemones will go far in our ability to conserve them.”
The anemones—both of which are commonly called Tealia red anemones under the species of Urticina—spawned in late April and early May, just days apart. Hours after they spawned, Henley collected the eggs and sperm from the more than 2,000-gallon tank and put them together in smaller tanks to increase the chances of fertilization. After fertilization, the larvae settled and metamorphosed into a polyp. Henley put some of the developing larvae in a circular tank—called a kreisel—that automatically stirs the water to prevent the larvae from binding to one another, which would kill the animals. The kreisel is the same tank Henley and others use in the field in Puerto Rico to hold coral larvae. Other free-swimming larvae went into a regular tank with aeration and rocks to settle on. Now the Zoo has hundreds of thriving anemones behind the scenes, all smaller than the tip of a pencil.
“Sometimes we take the lessons we learn with animals in captivity and apply that to conserving them in the wild,” said Alan Peters, curator of the Zoo’s Invertebrate Exhibit. “But here we were able to apply what we’ve learned both in the field and from ex situ work and it is yielding some exciting results.”
While anemones and coral are both in the Anthozoa class of animals, they differ in a few notable ways. Anemones metamorphose into a single polyp, while coral will divide into a second polyp and a third and so on, to form a colony. In addition, anemones have a muscular foot they use to attach to rock, while stony corals make their own calcium carbonate rock that they live on. But both can sting and are carnivorous, feeding on crabs, shrimp, fish and zooplankton. More than 1,000 sea anemone species inhabit the world’s oceans at various depths, from the sandy seashore up to the surface. Visitors to the Zoo can see six different species of anemones, including cold and warm water anemones. Although anemones are not endangered, ocean habitats around the world are in decline as the result of pollution, runoff and sedimentation, climate change, acidification and poor fishing practices.
Henley will continue to observe the anemones to learn about their growth rate and the conditions that are necessary to rear these species in captivity, including the food, light and water temperature they require.
“In the past if the anemones spawned in the tank, it’d be a big headache,” said Henley. “You’d have to do frequent water changes because when the gametes—or reproductive cells—get too concentrated and deteriorate, it causes the water quality to crash. That’s the common experience among many of our zoo and aquarium colleagues. But this was different—so far it’s amounted to young anemones that we will continue to learn from for months, even years, to come.”
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Showing posts with label coral reef. Show all posts
Showing posts with label coral reef. Show all posts
Friday, August 27, 2010
Thursday, October 9, 2008
Diversity of Plant-Eating Fish May be Key to Coral Reef Recovery
For endangered coral reefs, not all plant-eating fish are created equal.
A report scheduled to be published this week in the early edition of the journal Proceedings of the National Academy of Sciences suggests that maintaining the proper balance of herbivorous fishes may be critical to restoring coral reefs, which are declining dramatically worldwide. The conclusion results from a long-term study that found significant recovery in sections of coral reefs on which fish of two complementary species were caged.
Coral reefs depend on fish to eat the seaweeds with which the corals compete, and without such cleaning, the reefs decline as corals are replaced by seaweeds. Different fish consume different seaweeds because of the differing chemical and physical properties of the plants.
“Of the many different fish that are part of coral ecosystems, there may be a small number of species that are really critical for keeping big seaweeds from over-growing and killing corals,” explained Mark Hay, the Harry and Linda Teasley Professor of Biology at the Georgia Institute of Technology. “Our study shows that in addition to having enough herbivores, coral ecosystems also need the right mix of species to overcome the different defensive tactics of the seaweeds.”
By knowing which fish are most critical to maintaining coral health, resource managers could focus on protecting and enhancing the highest-impact species. In situations where local peoples depend on fishing, they might better sustain the reefs on which they depend by harvesting only less critical species.
“This could offer one more approach to resource managers,” Hay added. “If ecosystems were managed for critical mixes of herbivorous species, we might see more rapid recovery of the reefs.”
Believed to be the first study to demonstrate the importance of herbivore diversity in enhancing the growth of coral reefs, the research was conducted at the National Undersea Research Center in Key Largo, Florida. It was supported by the National Oceanic and Atmospheric Administration, the National Science Foundation and the Teasley Endowment at Georgia Tech.
Working 60 feet below the surface near the underwater laboratory Aquarius, Hay and co-author Deron E. Burkpile – who is now at Florida International University in North Miami – constructed 32 cages on a coral reef. Each cage was about two meters square and one meter tall and was sealed so that larger fish could neither enter nor leave.
The number and type of fish placed into each four-square-meter cage varied. Some cages had two fish that were able to eat hard, calcified plants; some had two fish able to eat soft, but chemically-defended plants; some had one of both types, and some had no fish at all. The cages were observed for a period of ten months starting in November 2003, and the change in coral cover and seaweed growth was measured.
“For the cages in which we mixed the two species of herbivores, the fish were able to remove much more of the upright seaweeds, and the corals in those areas increased in cover by more than 20 percent during ten months,” Hay said. “That is a dramatic rate of increase for a Caribbean reef.”
Though the percentage growth was impressive, the actual growth in size of each coral was small, Hay noted. Prior to the experiment, the coral reef areas studied had just four to five percent coverage of live coral. After ten months, the corals caged with the two species showed six to seven percent coverage. Corals caged with just one type of fish or no fish lost as much as 30 percent of their cover during the time period.
Hay and Burkepile attempted to repeat their experiment with a different species of fish, but the underwater cages were wiped away by Hurricane Dennis in July 2005 after only seven months of study.
The researchers studied the effects of the redband parrotfish (Sparisoma aurofrenatum) and the ocean surgeonfish (Acanthurus bahianus) in the first experiment, and the redband parrotfish and princess parrotfish (Scarus taeniopterus) in the second. The two fish per cage was at the “high end” of fish density found on present-day Caribbean reefs, but historic densities might have been much higher before extensive fishing of the Caribbean, Hay said.
Just two decades ago, coral coverage in the Caribbean was commonly 40 to 60 percent. Scientists blame many factors – disease, overfishing, pollution, excessive nutrients and global climate change – for the rapid decline, which has also been seen to differing degrees among coral reefs worldwide.
“Some people would argue that coral reefs really don’t exist as functional ecosystems in the Caribbean anymore,” Hay said. “The best reefs we have today are poor cousins to what was only average 20 years ago.”
For the future, Hay would like to expand the experiments to study the effects of additional species, and repeat the studies in different areas, such as the Fiji Islands, where residents are concerned about sustainability of the coral reefs. Though dependent on local fish for their protein, he said the Fiji Islanders may be able to change their fishing habits if researchers can determine which fish must be protected to help the reefs.
“The data we are seeing in Fiji suggests that diversity may be even more important there than it was in the Caribbean,” he said. “There are a lot of different species doing a lot of very different things. These consumers are very important, and in areas where they are over-fished, the reefs are crashing.”
The study provides more proof of how important biodiversity can be to maintaining healthy ecosystems.
“Species diversity is critically important, but we are losing critical components of the Earth’s ecosystem at an alarming rate,” Hay said. “There has been little work on the role of diversity among consumers and the effect that has on communities. This study will help add to our knowledge in this critical area.”
-----
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A report scheduled to be published this week in the early edition of the journal Proceedings of the National Academy of Sciences suggests that maintaining the proper balance of herbivorous fishes may be critical to restoring coral reefs, which are declining dramatically worldwide. The conclusion results from a long-term study that found significant recovery in sections of coral reefs on which fish of two complementary species were caged.
Coral reefs depend on fish to eat the seaweeds with which the corals compete, and without such cleaning, the reefs decline as corals are replaced by seaweeds. Different fish consume different seaweeds because of the differing chemical and physical properties of the plants.
“Of the many different fish that are part of coral ecosystems, there may be a small number of species that are really critical for keeping big seaweeds from over-growing and killing corals,” explained Mark Hay, the Harry and Linda Teasley Professor of Biology at the Georgia Institute of Technology. “Our study shows that in addition to having enough herbivores, coral ecosystems also need the right mix of species to overcome the different defensive tactics of the seaweeds.”
By knowing which fish are most critical to maintaining coral health, resource managers could focus on protecting and enhancing the highest-impact species. In situations where local peoples depend on fishing, they might better sustain the reefs on which they depend by harvesting only less critical species.
“This could offer one more approach to resource managers,” Hay added. “If ecosystems were managed for critical mixes of herbivorous species, we might see more rapid recovery of the reefs.”
Believed to be the first study to demonstrate the importance of herbivore diversity in enhancing the growth of coral reefs, the research was conducted at the National Undersea Research Center in Key Largo, Florida. It was supported by the National Oceanic and Atmospheric Administration, the National Science Foundation and the Teasley Endowment at Georgia Tech.
Working 60 feet below the surface near the underwater laboratory Aquarius, Hay and co-author Deron E. Burkpile – who is now at Florida International University in North Miami – constructed 32 cages on a coral reef. Each cage was about two meters square and one meter tall and was sealed so that larger fish could neither enter nor leave.
The number and type of fish placed into each four-square-meter cage varied. Some cages had two fish that were able to eat hard, calcified plants; some had two fish able to eat soft, but chemically-defended plants; some had one of both types, and some had no fish at all. The cages were observed for a period of ten months starting in November 2003, and the change in coral cover and seaweed growth was measured.
“For the cages in which we mixed the two species of herbivores, the fish were able to remove much more of the upright seaweeds, and the corals in those areas increased in cover by more than 20 percent during ten months,” Hay said. “That is a dramatic rate of increase for a Caribbean reef.”
Though the percentage growth was impressive, the actual growth in size of each coral was small, Hay noted. Prior to the experiment, the coral reef areas studied had just four to five percent coverage of live coral. After ten months, the corals caged with the two species showed six to seven percent coverage. Corals caged with just one type of fish or no fish lost as much as 30 percent of their cover during the time period.
Hay and Burkepile attempted to repeat their experiment with a different species of fish, but the underwater cages were wiped away by Hurricane Dennis in July 2005 after only seven months of study.
The researchers studied the effects of the redband parrotfish (Sparisoma aurofrenatum) and the ocean surgeonfish (Acanthurus bahianus) in the first experiment, and the redband parrotfish and princess parrotfish (Scarus taeniopterus) in the second. The two fish per cage was at the “high end” of fish density found on present-day Caribbean reefs, but historic densities might have been much higher before extensive fishing of the Caribbean, Hay said.
Just two decades ago, coral coverage in the Caribbean was commonly 40 to 60 percent. Scientists blame many factors – disease, overfishing, pollution, excessive nutrients and global climate change – for the rapid decline, which has also been seen to differing degrees among coral reefs worldwide.
“Some people would argue that coral reefs really don’t exist as functional ecosystems in the Caribbean anymore,” Hay said. “The best reefs we have today are poor cousins to what was only average 20 years ago.”
For the future, Hay would like to expand the experiments to study the effects of additional species, and repeat the studies in different areas, such as the Fiji Islands, where residents are concerned about sustainability of the coral reefs. Though dependent on local fish for their protein, he said the Fiji Islanders may be able to change their fishing habits if researchers can determine which fish must be protected to help the reefs.
“The data we are seeing in Fiji suggests that diversity may be even more important there than it was in the Caribbean,” he said. “There are a lot of different species doing a lot of very different things. These consumers are very important, and in areas where they are over-fished, the reefs are crashing.”
The study provides more proof of how important biodiversity can be to maintaining healthy ecosystems.
“Species diversity is critically important, but we are losing critical components of the Earth’s ecosystem at an alarming rate,” Hay said. “There has been little work on the role of diversity among consumers and the effect that has on communities. This study will help add to our knowledge in this critical area.”
-----
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