This month, the National Aquarium in Baltimore opened a new permanent exhibit, Blacktip Reef. Based on the Indo-Pacific reefs found across a large swath of oceans, the exhibit is the largest of its kind in the world.
How did you get into this exciting line of work?
Jack Cover: I’ve been with the aquarium over 25 years. I’m originally from Baltimore, then travelled around for different jobs, but came back to this area.
For a while I specialized in reptiles and amphibians, which is neat because we do have a sea turtle in the exhibit. But I’ve always had a connection to the Chesapeake Bay and to water in all ecosystems.
What makes Indo-Pacific reefs special?
Think of the Great Barrier Reef as basically a mountain ridge near the sea’s surface, and the live coral grows on top of that ridge. Coral is a colonial animal; stony coral is made up of pockets for individual polyps, which deposit limestone as they grow, on top of their ancestors. It may look like a bunch of rocks, but it is a living animal, closely related to jellyfish and sea anemones. If a piece of the reef breaks off, it can repair itself.
The polyps catch zooplankton and are also solar powered, since they have algae that live with them and produce food for them. The coral structure provides lots of shelter and hiding places for lots of other animals.
A coral reef is like a city of the ocean, like New York City, with lots of physical structure and lots of diversity. Small creatures hide in the coral at night, where larger predators can’t get to them. Apex predators hang around.
What animals do you have in Blacktip Reef?
We’ll have 20 blacktip reef sharks. It’s an iconic species for shallow water and a beautiful animal, with fins that look like they have been dipped in black ink. They form social groups and hunt in a cooperative manner. We want to get away from this whole Jaws, scary image of a shark.
sharks that are bottom dwellers that blend in with the habitat, and we have zebra sharks. We have rays that will eventually reach a size of six to seven feet (1.8 to 2.1 meters) from wingtip to wingtip. The reticulated whiptail ray has incredible colors.
We also have schools of unicorn fish, tangs, wrasse, diamond fish, angelfish, oriental sweet lips…some really colorful fishes.
How did you “train” the reef sharks?
We do some training of the sharks before they go into the exhibit, to cue them in that it’s feeding time. It’s kind of like having 20 dogs: you better have bowls in different parts of the room or there will be a feeding frenzy.
So we have four feeding stations, with targets that tell them when it’s time for food. So the low guys on the totem pole all get fed, because there is a hierarchy. Many of them have individual personalities.
The target is a colored hexagonal plate. They learn that when they see the plate come out food is coming, so they should line up. The key to keeping sharks with prey animals is keeping their tummies full. We make it easier for them to get fed than chase small fish.
Does the exhibit have live coral?
There is no live coral in this exhibit. We have it in other exhibits, but it requires a tremendous amount of bright light. We would need the equivalent of the lights at a nearby ballpark. The front of the exhibit would have to have a filter on it, like a sunglass, or it would be too bright. It would take hundreds of years for corals to grow to the major structures that we have. And they are somewhat fragile, if a 500-pound (227-kilogram) sea turtle bumped into it, it would break.
As a conservation organization, we wouldn’t want to harvest live coral from the wild. But what we created functions like real coral in that it provides structure and places to hide. When a predator comes it is like a high school bully walking down the hallway, they give them space.
How was the faux coral recreated?
We wanted to faithfully recreate reef species, so as you go deeper the coral species change. The exhibit is divided into microhabitats, such as a cave, which has more sponges and corals that live in lower light.
So the first thing we did was make a clay scale model of the space. We did 3-D printing of the pipes, to put in all the infrastructure. We had to make sure we had room and checked all the sightlines. Then we took photos of real habitat, to recreate it down to the last detail.
Then we took Styrofoam and carved it into the general shape, with nooks and crannies. Then we laid fiberglass cloth on that, like building a boat, and put different resins on it to give it a rough form. The foam was taken away to make it hollow, so we could run plumbing through it. We then added a texture coat of polyester resin.
All the materials have to be completely inert and harmless to aquatic animals. These structures also have to be strong enough so if the tank was drained it could hold the weight of a sea turtle.
We mixed in different types of sand and painted it. Once we had the basic structure, we made various species of coral: table, brain, staghorn, branching, and so on. We took real coral skeletons and made molds. We then put on a silicon rubber, for what we called the glove mold, because once that hardens it comes off like a glove. We poured in urethane to make the model.
The next part is where it gets a bit complicated. You could paint it red so it matches an image of the real thing, but when you place it six feet down it looks brown, because water blocks different wavelengths of light differently. It blocks red first. So we did color correction so it looks the right color at the right depth. Then we got them oriented so they look as they do in the wild.
The end product looks like you are actually on the Great Barrier Reef.
How long did it take to make the exhibit?
We did this on a pretty quick timeframe; we started a year and a half ago with the concept.
Where did the animals come from?
Calypso is a female green sea turtle, which is a pan-tropical species. She was found on a beach with netting wrapped around one flipper. It got infected and had to be removed. She’s a poster child for marine debris.