Advances in Coral Husbandry in Public Aquariums. Public Aquarium Husbandry Series, vol. 2. R.J. Leewis and M. Janse (eds.), pp. 239-250 © 2008 Burgers’ Zoo, Arnhem, the Netherlands. Chapter 26 The Coral Reef Exhibit at Reef HQ Aquarium, Townsville, Australia: Technical operations and water quality SÉVERINE THOMA S 1,3 AND SHELLEY L. AN T HONY 2,3 1 Université Européenne de Bretagne Université de Brest / CNRS, Institut Universitaire Européen de la Mer Place Nicolas Copernic, 29280 Plouzane, France [email protected] 2 School of Marine and Tropical Biology, James Cook University Townsville, Queensland 4811, Australia [email protected] 3 Reef HQ Aquarium, Great Barrier Reef Marine Park Authority 2-68 Flinders St.- PO Box 1379, Townsville, Queensland 4810, Australia ABSTRACT Reef HQ Aquarium, previously named the Great Barrier Reef Aquarium, houses the world’s largest living coral reef aquarium system, called the Coral Reef Exhibit (CRE). Over 20 years of CRE operation, water management has evolved significantly to improve the overall health of the tank. This chapter describes the present mode of technical operation of the CRE with a focus on water quality and compares with previous experiences. An increase in coral survival since current methods are in place indicates that a shift from occasional water exchanges using a priori ultra-clean oceanic water to regular exchanges with ‘less pure’ estuarine water has been largely beneficial to the CRE. Reduced mechanical filtration and increased general and localized flow have also contributed to a healthier system, which is very tolerant to large natural variations in some water quality parameters. INTRODUCTION The Coral Reef Exhibit (CRE) at Reef HQ Chapter 9). Aquarium in Townsville, Australia, is a 2.8-million The objective of this chapter is to review the liter living coral reef mesocosm designed to history of changes in CRE operations, and replicate an inshore reef on land (Eager and to provide detailed information about the Peterson, 1988). Built in 1987, and located in “hardware” side of operations, including water the coastal tropics in Townsville near the middle supply, filtration, illumination, circulation and of the Great Barrier Reef (Figure 1), Reef HQ water quality. It also includes a brief summary had several natural advantages to accomplish of the practices that have been applied to CRE this, including a tropical climate, open access maintenance during the first 20 years (some no to sunlight, and ready coral availability. longer in use) in order to provide a background Nevertheless, building the largest living coral to current practices, a history of water quality reef aquarium in the world included numerous parameters and the techniques in place to technical challenges at the time, and, although control these parameters, and a summary of advances in coral husbandry have been made what works best for the system. around the world in terms of coral husbandry in the last two or three decades, challenges still remain 20 years later. Ongoing improvements TECHNICAL OPeratiONS IN THE CRE in water quality and filtration methods, as well as altered collection and husbandry techniques, The CRE is a semi-rectangular tank (35 meters have led to vastly increased long-term survival length by 17 meters width and 4.5 meters rates for most coral species (reviewed in depth) that holds over 2.5 million L of seawater 239 S. THOMA S & S. AN T HONY 142 144 146 148 150 120 130 140 150 AUSTRALIA -12 -12 -40 -30 -20 -10 -40 -30 -20 -10 120 130 140 150 -14 -14 -16 -16 CAIRNS GREAT BARRIER REEF QUEENSLAND PALM ISLANDS -18 -18 TOWNSVILLE -20 Kilometers -20 300 142 144 146 148 150 Figure 1: Map of the Great Barrier Reef and location of the Reef HQ Aquarium in Townsville in relation to the coast of Australia. Figure 2: Photograph dating pre-2002 of the Coral Reef Exhibit showing its design and the surrounding Reef HQ Aquarium rooftop as seen from above. Note: the Algal Turf Farm – (square grids visible next to the tank at the top of the picture) is no longer in place. 240 CHAP T ER 26: THE CORAL REEF EXHIBI T A T REEF HQ AQ UARIUM : TE C HNI C AL OPERA T ION S AND WA T ER Q UALI T Y and 700 tons of live rock and corals and a on season and budget limitations. The Oceanic coarse carbonate sand substrate of varying Water period corresponds to a period of very depths (20 - 100 cm) (Figure 2). It is connected low coral survival, discussed in later sections. to a separate tank of approximately 700,000 L volume that serves as an intake, holding, and Water analysis testing container for new seawater when both Before introduction into the CRE, samples tanks are isolated, as well as a circulating and of the seawater barged into Reef HQ were chilling vessel in summer when both tanks are analyzed to ensure the seawater was within in line. As a result, the CRE volume varies from acceptable limits for inorganic nitrogen and 2.5 to 3.2 million L and is considered to be 2.8 salinity. Samples were also subjected to a million L on average when circulating. visual test for clarity, and a smell test for volatile The CRE is fully open to the elements at all contaminants, such as oil. On one occasion, times and exists in a climate marked by two the delivered seawater was contaminated with main seasons: dry and cool to warm between diesel fuel and was rejected, and an additional May and September, and warmer to very hot small number of deliveries were rejected due to between October and April. The rainy season not meeting salinity or clarity specifications. usually spans from late December until the end of March, with an average yearly rainfall Filtration in Townsville of 500 mm. Finally, Townsville is During the Oceanic Water period, filtration was located in a cyclone-susceptible region most carried out by three large sand filters (20 µm grain likely to occur during the summer monsoon. size) of 2000 liters each, as well as by an Algal Over its 20 years of existence, operation and Turf Farm (ATF) (Adey and Loveland, 1981), water treatment of the CRE can be divided into located on the roof of the aquarium (visible in two stages: pre-2002, when tank exchange Figure 2, top center). The ATF consisted of 70 water was sourced from off-shore ocean shallow PVC trays approximately 2 m in length waters, and post 2002 where estuarine water and 1 m in width covered with a 1 mm screen is used. These two periods will be referred to in mesh to serve as an algae substrate. The this paper as the “Oceanic Water period” and trays were exposed to sunlight plus additional the “Estuarine Water period” respectively, and overhead growing lamps that were operated at correspond to significant changes in filtration night and during cloudy periods. CRE water was methods. As a consequence of these changes, circulated through attached pipes and poured coral health and survival have also shown onto the trays via 20 L tipping buckets that significant improvements in the later period, as filled and then tipped atca. 30-second intervals discussed in Chapter 9. (depending on flow rate adjustments). Algal masses (Enteromorpha spp.) growing on the mesh absorbed excess inorganic nutrients THE OCEANIC Water PERIOD (PRE-2002) from the CRE water, and provided oxygen and stable pH levels. By manually removing the Water source and exchange algae from the trays, these inorganic nutrients For the first 15 years (between 1987 and 2002), were removed from the CRE. However, this the CRE was a completely closed system, and method required intensive labor and eventually new seawater for the exhibit was supplied became obsolete during the Estuarine Water exclusively by barge. The water was sourced period. offshore where water depth exceeds 20 m, near the mid-shelf Palm Islands Group. This Water circulation approach was chosen to ensure clean water For the first 15 years, water movement was for the tank, as inshore waters surrounding created partly by the return of the sand filters, Townsville were thought to carry too much and partly by a wave machine driven by sediment, nutrients, and possibly heavy metals compressed air (still in use today). The wave and other toxins or contaminants from the machine operates by compressing air inside nearby rail yards and shipping channel located four chambers blocked by a concrete slab on directly across from the Aquarium. the top, by the tank wall or separating walls on A single barge load contained approximately 4 sides, and by the tank water at the bottom. 300,000 L, or around 1/10 of the total CRE The four chambers are spread over the entire system, and exchange only occurred at a width of the tank. At regular intervals, and after maximum of one load per month, depending air is compressed, flaps inside the chambers 241 S. THOMA S & S. AN T HONY open to the atmosphere, rapidly releasing the batch intake system was devised. compressed air, thereby sucking the tank water The process begins with isolation of the 700,000 upwards. When the water level drops again by L holding tank from the CRE, and dumping of gravity, a wave is created and propagates over the contained seawater into the higher-nutrient the entire length of the tank. The system allows “Predator Tank” for water exchange in that for an offset in the compression frequency in system. Water is then pumped into the holding each chamber, which can cause turbulence tank on the incoming tide from the tidal creek and interfere with water motion.