Posts in category: Recent news

Baby corals find their way home in their first days as free-swimming larvae by listening to the noise of animals on the reef and actively swimming towards it, an international team of researchers working in the Caribbean has discovered.

These findings raise new concerns for the future of coral reefs as increasing human noise pollution in the world’s oceans is masking reef sounds.

Dr Steve Simpson, Senior Researcher in the University of Bristol’s School of Biological Sciences, discovered several years ago that baby reef fish use sound as a cue to find coral reefs, but was amazed when his Dutch collaborators in Curaçao working at Carmabi started finding that coral larvae – which must quickly find a safe place to land and establish a colony or they will die – can do the same thing.

The team designed a ‘choice chamber’ (a device that offers small invertebrates two or more contrasting conditions and allows them to move freely towards the one they prefer), put coral larvae into it and played them recordings of a coral reef. The results clearly showed that the flea-sized larvae were strongly attracted to the noise as they seek a suitable habitat.

Coral larvae look like tiny eggs covered in hairs, and come from the same group of animals (Cnidaria) that also includes sea anemones. How these simple creatures detect sound is unknown, but Dr Simpson said, “At close range sound stirs up water molecules, and this could waggle tiny hair cells on the surface of the larvae, providing vital directional information for baby corals.”

Corals aggregate to form vast reefs, which are now one of the most threatened ecosystems in the world. Due to global warming and ocean acidification, some experts have suggested coral reefs are now on death row. Understanding how these vulnerable animals complete their life-cycle is essential to ensure appropriate management.

Since corals, like fish, respond to reef sounds then the masking effects of human noise pollution in coral environments is of extra concern.

“Anthropogenic noise has increased dramatically in recent years, with small boats, shipping, drilling, pile driving and seismic testing now sometimes drowning out the natural sounds of fish and snapping shrimps,” Dr Simpson said.

This study was carried out by a team at the Camabi Foundation in Curaçao in the Dutch Antilles led by Dr Mark Vermeij, using larvae of the dominant Caribbean reef building coral Montastraea faveolata collected during the 2008 mass-spawning event.

The research is published in PLoS ONE and was funded through a fellowship to Dr Simpson by the Natural Environment Research Council (NERC, UK) and by the National Science Foundation and Scripps Institution of Oceanography (USA).

Download the paper by clicking this link.

Source: http://www.nerc.ac.uk/press/releases/2010/20-coral.asp

Work on sponges on Curacaoan reefs by Jasper de Goeij, a Carmabi associate scientist, has been highlighted in NATURE, one of world’s leading scientific journals. Below one finds the text of the article:

How the sponge stays slim: One species’ rapid cell shedding explains its huge carbon-catching capacity.

Published online Nature doi:10.1038/news.2009.1088

By: Matt Kaplan

Biologists have discovered how a reef-dwelling species of sponge can filter enormous amounts of carbon without growing in size.The sponge Halisarca caerulea can absorb up to two-thirds of its own weight in carbon each day by shedding cells at a rapid rate, according to research by Jasper De Goeij at the Royal Netherlands Institute for Sea Research in Texel, the Netherlands, and his colleagues. In a study published in the Journal of Experimental Biology The team proposes that this fast turnover may be a tactic for coping with the toxins and pathogens that are frequently encountered by the filter-feeders in their environment.

H. caerulea is found on tropical reefs in the waters of the Caribbean, and feeds by filtering carbon-rich organic matter from the water. Earlier work by De Goeij had shown that the sponges could absorb prodigious amounts of carbon yet didn’t seem to grow in size. “We calculated that a sponge should double in biomass every three days, but found that H. caerulea hardly grows at all,” says De Goeij.
Absorbing science

To find out why, De Goeij and his colleagues collected growing sponges and stained them continuously with a chemical that labels actively dividing cells. The team cut samples from the sponge bodies at different time points up to 10 hours after the first exposure and analysed them for signs of the labelling agent.

They found that certain cells that pump and filter water in the sponge divided very quickly — once every five hours or so1. But adding a second chemical to search for dead cells revealed only a few in the chambers, which left them with a puzzle: the sponge wasn’t growing, but the cells didn’t seem to be dying off. Each day, H. caerulea absorbs up to two-thirds of its weight in carbon.

De Goeij was stumped until he gave a presentation on the sponge’s impressive cell division to a group of cancer researchers. They immediately recognized the rapid division behaviour as being very similar to that of the human gastrointestinal tract. Cells in the epithelium of the colon are replaced every 12–24 hours by rapid proliferation and then shedding. “Once we looked at the sponge tissue with the human colon in mind, we found massive amounts of shedding,” says De Goeij.

Other marine biologists are surprised by the find. “Nobody has looked at cell sloughing in sponges like this before,” says Malcolm Hill, a marine ecologist who specializes in sponge evolution at the University of Richmond in Virginia.

De Goeij and his colleagues suggest that the rapid growth and shedding of the cells may be an evolutionary response to the harsh conditions in which H. caerulea grows. To survive in the nutrient-sparse Caribbean Sea, the sponge must filter vast quantities of water, which is likely to increase its exposure to toxins and pathogens. Rapid shedding might prevent such problematic materials from building up and damaging the filtering system, De Goeij says.

“Now that we know this, we need to look at other sponges to see whether this is a general phenomenon or just an idiosyncrasy of this particular species,” says molecular palaeobiologist Gert Wörheide of Ludwig-Maximilians-University in Munich.

Hill believes that sponge biology could reveal useful information that is relevant to human diseases. “If this proves to be more than just the behaviour of one odd species, then studying the ways that sponges control cell growth could provide insight into controlling abnormal cell growth like cancer,” he says.

References De Goeij, J. M. et al. J. Exp. Biol. 212, 3892-3900 (2009).

This map shows the distribution of lionfish that were either observed or captured along  the south-western shore of Curacao around November 2009 (the map below was later added to show the rapid spread of this fish once it established itself and shows the distriution of observed lionfish. at the beginning of 2010. Note that lionfish have spread outside the visualized area and that the second picture only aims to show the increase in lionfish sightings in this area).  Unconfirmed reports also mentioned lionfish to be present at Eastpoint, but all confirmed observations come from the western site of the island. The majority of sightings come from dive operators which probably explains the clustering of sightings in the Westpunt and Habitat areas. All lionfish concern small individuals measuring between 4-6 cm except for one individual observed at the dive site “Radio City” which measured 15 cm in length.  Reports keep coming in now on almost a daily basis and local Governmental Organizations (VOMIL, LVV) and Carmabi currently work together to put together a strategy to (1) study the effects of lionfish on the reef systems of Curacao and (2) develop effective management scenario’s if necessary. We kindly request all persons that observe a lionfish to report their sightings to either Paul Hoetjes or Mark Vermeij .

In the last several years, members of Dr. Mark Hixon’s lab working at the NURP Caribbean Marine Research Center at Lee Stocking Island (LSI), a field station at the southwestern end of Exuma Sound, Bahamas, have documented increasingly frequent sightings of lionfish. These findings have provided an unprecedented opportunity to study the ecological interactions of lionfish with Caribbean coral reef fish communities from the very beginning of the invasion.

PhD student Mark Albins of Hixon’s team devised a controlled experiment testing the effects of lionfish on native fish communities by documenting the recruitment of newly settled reef fishes on 20 patch reefs near LSI: 10 reefs with a lionfish and 10 reefs without. Fish censuses were conducted at one week intervals for five weeks. Recruitment was significantly lower on lionfish reefs than on control reefs at the end of the experiment. On one occasion, a lionfish was observed consuming 20 small wrasses during a 30 minute period.

It was not unusual to observe lionfish consuming prey up to 2/3 of its own length. Results of the experiment show that lionfish significantly reduce the net recruitment of coral reef fishes by an estimated 80%. The huge reduction in recruitment is due to predation and may eventually result in substantial, negative ecosystem-wide consequences. It is also important to note that lionfish have the potential to act synergistically with other existing stressors, such as climate change, overfishing, and pollution, making this invasion of particular concern for the future of Atlantic coral reefs.

While complete eradication does not seem realistic, affected nations are encouraged to initiate targeted lionfish control efforts as soon as possible, including targeted fisheries (lionfish flesh is tasty and cooking denatures the spine venom). Efforts to reduce densities of lionfish at key locations may help to lessen their ecological impacts. Recovering and maintaining healthy populations of potential native predators of lionfish, such as large grouper and sharks, may also help reduce the deleterious effects of these voracious invasive predators.

Source: NOAA Research