Restoring Finger Coral

We’ve been very busy lately working on our coral restoration experiment, as well as several other projects. Time to finally talk about the coral restoration experiment, since I actually have photos of what we’re doing.

Bleached Pocillopora head surrounded by dead reef

Most of the patch reefs near Sand Island have very little to no coral cover, but we can tell that the rubble and dead coral used to be primarily Porites compressa, known as finger coral in Hawaii. As recently as the 1970s, people reported seeing large Porites compressa reefs there. We’re not sure exactly why these reefs have so little live coral, but it may be related to sewage outflows or dredging in that area. Reefs farther out in the center of the atoll, however, have huge stands of finger coral. The Papahanaumokuakea Marine National Monument, which manages all the Northwestern Hawaiian Islands, has prioritized restoring these degraded patch reefs near Sand Island.

Huge stand of of finger coral

My labmate Wendy Cover, who will be Dr. Cover within a year, designed and applied for funding and permits to conduct a coral restoration experiment which involves transplanting “fingers” of Porites compressa to these nearshore patch reefs. Wendy’s hypothesis is that Porites compressa would survive at these nearshore patch reefs, but they aren’t receiving recruitment (i.e., babies), so restoration by transplanting would be effective. 

First, we explored the nearshore patch reefs (“transplant sites”) and the patch reefs with Porites compressa (“source sites”) and selected transplant and source sites. Second, we cleared small areas of algae and labeled them with metal tags (which hopefully the fish won’t eat, unlike our plastic eartags!). Third, we collected fingers of Porites compressa at the source site, transported them in coolers to the transplant sites, and glued them down using epoxy. 

Now we’re going back to both transplant and source sites to take photos and measurements, survey for benthic cover (algae, coral, etc.) and urchins, and deploy coral recruitment tiles.

Wendy selects transplants

Wendy & Anne glue down transplants

Anne leaves today, so I'll have to make another post soon on the amazing dive we did yesterday and other things we've been observing, like coral bleaching of a few species and a spawning party of saddle wrasses!

Projects Galore!

We've been working on a variety of projects while the volunteers were here and since they left.  Here's a short snapshot of them:

• Collecting short cores to determine what's building the reef in various places (e.g., corals, coralline algae, etc.).  We've collected 4-inch or so cores at 2 different sites using a pneumatic drill and scuba tanks.  Each tank lasts about 5 minutes, so the main effort is carrying tanks to the site and on the reef crest!  Here’s a photo of Anne and Don coring on the reef crest at Reef Hotel.

• Sediment coring to determine how sediment production and distribution has changed through time.  Originally, we were going to use a gas-powered hydraulic pump powering a vibra-corer designed by Anne’s undergraduate mentor Dennis Hubbard, but instead we tried a pneumatic vibrator powered by scuba tanks.  Unfortunately, it’s not as powerful, so it’s difficult to use in water deeper than waist-deep and doesn’t collect cores as long as we had hoped.

• Deploying a video camera to observe life on the reef when we’re not there.  We plan to use the video camera to answer questions such as: how much do urchins move around and how much of the day do pearl oysters spend
  feeding?
  
  Unfortunately, the video camera is very complicated, so we’ve had problems convincing it to work!

• Deploying temperature loggers to record water temperature right next to corals every 15 minutes for a year or more.  We already had 9 deployed around the atoll and are deploying 6 more this year.  Here is a photo of Anne deploying stakes to which we attach the temperature logger.

• Measuring depth of the sand below the Cargo and Fuel Piers to determine how the shoreline changes year-to-year.  Our volunteers for the past three years have made this time-consuming endeavor possible and provided a lot of interesting information.  At left is a photo of volunteer Seiji measuring the depth using a transect tape with a weight at the end.

• Collecting sea urchins and sea stars to help identify their skeletal fragments in the sediment.  We collected this very cool fine-spined urchin Leptodiadema purpurem during a sediment collection dive.

Now, in addition to continuing this projects, we're putting much of our effort into an experiment studying the feasibility of coral restoration on the reefs near the main island (Sand Island), which is a high priority for the Papahanaumokuakea Marine National Monument.  More on this project in the next blog post!