CORAL REPRODUCTION RESEARCH

A flow-through filtration system set up on the top deck of the M/V Fling. The canopy shelters the bins from direct sunlight. Photo: Drinnen/FGBNMS

Principle Investigator:

Sarah Davies
Masters Student, Marine Biology
University of Calgary
Alberta, Canada
swdavies@ucalgary.ca

Research Focus:

Herbivore Effects on Coral Recruitment

Summary:

Sarah Davies is a graduate student under Dr. Peter Vize at the University of Calgary. Her work is focused on how herbivores affect the settlement of coral larvae on the reef. This is known as coral recruitment. Sarah's hypothesis is that the presence of herbivores should increase recruitment by decreasing algae and thus creating more suitable places for coral to settle.

Underwater platform constructed of wire mesh with 9 white bins on top. This structure is located in an open sand flat at West Flower Garden Bank near buoy #5. Photo: Drinnen/FGBNMS

To test this hypothesis, Sarah designed a large underwater platform and system of bins that could hold recruitment tiles and herbivores. This platform was first built on land in Austin, TX, then taken apart and transported in pieces out to the sanctuary. A crew of divers spent several days in June 2007 reconstructing this platform underwater in one of the open sand flats at West Flower Garden Bank, near buoy #5.

The main concern for this stucture was its ability to remain intact and in place during strong storms, such as hurricanes, so that it wouldn't damage the surrounding reef. In fact, the platform was put to a test by Hurricane Dean passing through the southern Gulf of Mexico in August 2007. 13-29 foot waves managed to dislodge three large blue bins from the platform by breaking the 500-pound cable ties anchoring them in place. The nine smaller white bins remained in place.

12 ceramic tiles were placed in each bin to provide a settling surface for coral larvae. The bins were covered with wire mesh to keep in the intended herbivores and keep out any extras. Photo: Drinnen/FGBNMS

The original platform set up consisted of 12 study bins (3 large blue bins and 9 smaller white bins). The affects of Hurricane Dean reduced this to just the 9 white bins. Inside each bin, Sarah placed 12 ceramic recruitment tiles in all different orientations. Some were placed in vertical positions while others were laid horizontally. Some had their smooth surface exposed while others had their rough surface face up.

Four bins (1 blue and 3 white) were assigned to each test group. One set contained Diadema sea urchins, one set contained small marine snails, and one contained no herbivores at all (the control set). Each bin was then covered with wire mesh to keep the desired herbivores in and any others out. It took Sarah several tries to settle on an appropriate size mesh (.25 inch) that wouldn't foul with algae and interfere with the experiment.

During the coral spawning cruise in September 2007, Sarah took updated photos of each bin and each recruitment tile. In the process, she observed that brooders (coral recruits) had already settled on some of the tiles. She also noted that they seemed to prefer the grooved (rough) side of the tiles over the smooth side. Further study of these photos will enable her to compare tiles from the different treatments (urchin, snail, and control).

Coral spawn in buckets on board the M/V Fling. One bucket contains spawn from Diploria strigosa and the other from Montastraea franksi. Photo: Drinnen/FGBNMS

Sarah Davies rinsing coral spawn in two plastic vials. Floating nearby is one of the plastic bottles, complete with fishing float, that will be filled with spawn and suspended over the underwater platform. Photo: Drinnen/FGBNMS

To facilitate coral recruitment in the area of the experiement, Sarah also collected coral spawn. She then rinsed the spawn and poured them into plastice bottles which were then supsended over the bins. Holes in the bottom of each bottle enabled the settling spawn to drop down to the platform below.

Bottles full of coral spawn suspended over the recruitment platform. Photo: Drinnen/FGBNMS

Sarah will continue to monitor her experiment as often as she can return to the sanctuary. She also has her own coral-farmer web site where you can keep up with her most recent activity on this project.

In the meantime, sanctuary staff keep an eye on things each time they are in the vicinity.

To learn more about what Sarah and other students at the University of Calgary are doing, you can visit the Vize Lab web page.

Other Coral Reproduction Studies at the Flower Garden Banks National Marine Sanctuary:

Peter Vize
Dan Hilton