Saltcorner: Article: In the Lagoon of Sharks

The Oceanographic Museum is located on the 'rock' of Monaco, and its southern façade overlooks the Mediterranean. The brainchild of Prince Albert I, a pioneer of oceanography, it was conceived to house the scientific collections he had accumulated. Today it's both an oceanographic museum and a world class public aquarium dedicated to living exhibits from all the seas of the world.

The latest addition to this splendid collection is a captive, full-size coral reef housed in a massive tank and called the Lagoon of the Sharks. It features a coral reef, open on one side over a living tropical lagoon ecosystem and on the other side onto the deep water territory of big predatory sharks and rays. The aquarium is, in fact, two separate tanks divided by a sheet of thick clear acrylic, designed to appear like a fault in the reef, opening a passage allowing you to see these two worlds interacting.

This awesome exhibit rises two storeys high and 10m long x 9m wide (33' x 30'). It holds 400,000 l. and houses a living coral reef teeming with a diverse number of invertebrates, small and large fishes and lurking bands of big predators.

The design of the tank was conceived in the early 1990s, but the actual building and setting up of the exhibit took less than a year and opened to the public for the first time during the Fifth International Congress of Public Aquariums held at the Museum in November 2000. All the corals and many of the fish were bred and raised in closed circuit systems on the premises. This was a real achievement in terms of aquaculture and a triumph for the aquarium's coral farming and fish breeding research team.

The exhibit's totally natural coral landscape presented some difficulties. The water quality for the living corals could have been seriously affected by high levels of pollutants caused by the large predators, and this was the main reason for dividing the tank. Water from each side of the exhibit doesn't mix - both systems are separately filtered by plenum-style filtration beds in each tank, with additional sand filters on the large predator side. To ensure the best conditions in both systems, there is an hourly 1% water change with fresh, natural seawater.

Interestingly, despite nitrate levels still being quite high in the large predator tank, anemones, complete with Clownfishes and soft corals, thrive in the upper shallows of the 6m (20') deep tank and a small number of Banggai cardinalfish, which were accidentally introduced to the tank during the maturing process, have reproduced and formed quite large colonies.

# Total dimensions: 10 x 9m (33' x 30')

# Total volume: 450m3 - 400,000 l. capacity

# Global weight of tank: 600 tonnes

Radiating out from each side of the Lagoon of the Sharks are the two main halls of the aquarium - on the east side, the temperate zone encompassing the Mediterranean Sea and nearby Atlantic Ocean, and on the west side, the Tropical zone.

A whole variety of habitat and environment-themed tanks allows over 100 species of Mediterranean and Atlantic fish and a similar number of inverts to be displayed in near-to-perfect conditions. Many of the longest-living residents are found in this area, including a Brown moray, Gymnothorax unicolor, introduced in 1968 as an adult.

The tropical displays feature subjects from the Indian and Pacific Oceans, Red Sea and the Caribbean. The aquarium's worldwide reputation rests firmly on its highly successful live coral exhibits which thrive thanks to the Microcean water purification process (plenum filtration) perfected by Professor Jean Jaubert of Nice University. This not only allows corals to survive in closed aquarium systems but complete reef environments, including all of the flora and fauna found on a natural reef.

The result is a magnificent series of tropical reef exhibits, some including complete reconstructed reefs of living coral containing collections of over 70 different species and a wide range of other reef life forms.

The Tropical Hall features room-sized reef tanks along with smaller exhibits which display shoals of Banggai cardinalfish and other species resulting from the aquarium's captive breeding programme.

The success of many of the tanks in the temperate exhibits relies on semi-closed or open circuit filtration with permanent water renewal using seawater extracted directly from the sea below the museum.

The tropical tanks, on the other hand, operate on a totally closed-circuit basis. The tropical exhibits are separately managed using a computerised system developed to monitor the water parameters of each tank and its technical equipment and report any problems to the staff.

It's the combination of Jaubert's Microcean water purification methodology and the dedication and expertise of the staff of the aquarium, though, that has allowed the culture of reef building corals to be mastered on such a large scale inside closed circuit aquaria for the first time. A lot of the expertise has come from laboratory culture of corals using them as biological models to study aspects such as the mechanisms of clarification and photosynthesis of their symbiotic algae. These studies have been extended by using the live reefs kept in the aquaria to provide valuable information on the operation of coral ecosystems.

This means the aquarium has become an exceptional research and observation tool, enabling new ways of improving the techniques of maintaining coral reef systems to be explored.

Fitting a 400,000 l. aquarium into an existing building wasn't easy, especially as the museum is positioned directly on a cliff and is more than a century old.

A two-storey deep gallery had to be excavated from the bedrock of the cliff to make room for the exhibit and its biological filters. Slots had to be cut into the floor in the public entrance to allow the five huge acrylic panels, forming the viewing windows into the tanks, to be lowered into position at the site of the aquarium below. Two of these 35cm (14") thick acrylic panels were chemically fused together on site to form the main transparent 9m long x 6m (30' x 20') high viewing area.

Large numbers of fishes were brought in from other aquariums all over the world to supplement those bred on site. The aquarium's 'coral farm' propagated hundreds of colonies representing more than 70 species of corals. Then followed the task of introducing this large variety of reef life into the exhibit, and this lasted several months.

There's a real reef passage. On one side on the coral lagoon, there's a living coral reef teeming with brightly-coloured fish, corals and other delicate inverts. On the other side, there's a deeper, exposed outer reef populated by large fish and lurking bands of big predators.

* A 5.7m long x 2.75m high (19' x 9') window on the upper viewing platform allows visitors to see the near surface activities of lagoon dwellers at the highest part of a coral reef. It is also possible to see at close quarters some of the tanks' life support technologies, like high intensity lighting and circulation systems.

* The first of three viewing locations on the lower level provides a panoramic view of the deep reef environment with its spectacular display of large cruising fish and sleek predators.

* A 3m x 3m (10' x 10') panel allows you to view fauna living in the shelter of the rocks, with sharks and other predators cruising close by.

* A 7.5m long x 3m (25' x 10') panel allows a vision of the reef's teeming life; in the background, sharks can be admired from the deep reef beyond.

In the aquarium's research laboratory, over 30 species of fishes and inverts are bred and raised in captive conditions. Snipefish, Macrorhamphosus scolopax, (which gets its name from its long beak-shaped mouth), Clownfish and Banggai cardinals, were obviously no problem to breed, judging by the numbers I saw on my tour. In fact, the cardinals, which are mouth brooders, had reached 800 within six months of the first successful spawning. According to Pierre Giles, Deputy head of the aquarium at the museum, the success is largely down to good husbandry, which encourages the fish to come into breeding condition, coupled with advanced techniques employed to culture planktonic foods for the young.

The coral farm was very impressive, consisting of rows of shallow plastic laboratory trays, 2m x 1m x 20cm deep (6' 8" x 3' 3" x 8") used for initiating the growth of small ramifying coral fragments. Much larger tanks are used for growing out cuttings and building up large colonies from colony fragments.

At the initiating stage, small hard coral fragments are laid out loosely in the bottom of the trays on lengths of perforated plastic, while soft coral cuttings are protected from each other in short sections of plastic tube. Filtered water is circulated continuously through these trays and each is illuminated by metal halide lighting.

The grow-out tanks are also well-illuminated and have lengths of plastic tube criss-crossed above the water level to allow hard coral cuttings and coral colonies to be suspended in the water using nylon fishing line. This method allows the full potential of these quite large tanks to be used while permitting easy access to each individual coral. Pierre said that fast-growing hard corals like Acropora species can easily grow 10cm (4") a year and cover the plastic supports to which they are attached. All the live corals for the Lagoon of the Sharks exhibit were cultured and reared in the coral farm in just over a year.

This article appeared in the May/2002 issue of Practical Fishkeeping and is presented here with the permission of Practical Fishkeeping and its author, Les Holliday.

In the Lagoon of Sharks

Authored by: Les Holliday