About SeaSim, the National Sea Simulator

Australian Institute of Marine Science, Embargoed

Media background information, 1 August 2013

What is SeaSim?

SeaSim is a research aquarium. It comprises a seawater processing plant, several controlled environment rooms, and open plan spaces for large tanks and long-term experiments.

In short, it brings together a reliable, consistent supply of high quality seawater with the technology to enable precise control over environmental factors, such as temperature, light, acidity, salinity, sedimentation and contaminants.

SeaSim is an international facility. Researchers from around the world can apply to use it. Up to 50 per cent of its capacity is available for projects outside of those initiated by the Australian Institute of Marine Science (AIMS).

SeaSim technologies

SeaSim integrates technology developed in the industrial process sector—used to control and manipulate seawater and ambient conditions—with aquarium technologies of plant and animal husbandry.

It enables experimental research not previously possible, for instance, the long-term impact of pollutants on coral ecosystems.

The developers of SeaSim visited more than 40 aquariums around the world, such as at the Monaco Scientific Research Centre, Monterey Bay Aquarium Research Institute and the Scripps Institution in San Diego, to determine best-practice in providing and managing marine research aquarium environments.

Then they consulted with developers of emerging technology in other fields to incorporate ideas, such as carbon dioxide injection from the carbonated drinks industry, into the creation of a unique research aquarium.

SeaSim was designed and put together by AIMS staff members and engineers from Meinhardt & Oceanis and Flanagans, and architects from Cox Rayner & Tippett Schrock.

As a single integrated research hub, SeaSim provides the capacity to:

  1. undertake large experiments involving many different factors requiring sophisticated control—such as multi-generational studies of the impact of climate change on coral;
  2. undertake long-duration experiments involving many organisms—particularly corals, sponges and seagrasses—in large-scale tanks with precise control over seawater and ambient conditions; and
  3. acquire knowledge rapidly by developing and using model marine organisms, with a focus on corals and coral reproduction.

SeaSim’s technical features include:

Parameter

Performance

Technology used

Core technology ‘borrowed’ from

Temperature ±0.1°C Plate heat exchanger Engine coolant systems
Salinity ±2 parts per thousand (ppt) Reverse osmosis Desalination – then using the resultant brine to maintain coastal salinity in areas where it declines during the tropical wet season, killing the local coral.
Filtration <0.04 micronparticle size Pressurised laminar flow ultrafiltration Industrial-scale wastewater technology used in recycling reticulated public water.
Pressure control ±0.05 bar Electrical, hydraulic and pneumatic actuators Control engineering
Flow control ±3% Variable speed drive pumps, pneumatic actuators Industrial processing plants
Lighting To replicate the Sun’s spectrum Energy efficient light emitting diodes (LED) and light emitting plasmas (LEP) Energy efficient lighting technologies allowing simulation of full Sun spectrum indoors
Dissolvedcarbon dioxide (CO2) ±1 parts per million (ppm) CO2 injection membrane cartridge, infrared gas analysers Carbonated drinks industries, gas analysers
Integration Fully automated Supervisory control and data acquisition (SCADA) Industrial engineering control systems

SeaSim was developed by AIMS Project Manager Mr David Crute and Principal Research Scientist Dr Mike Hall with support from engineering companies Meinhardt & Oceanis and Flanagans and Cox Rayner & Tippett Schrock Architects.

What will SeaSim do?

Here are several key issues to be addressed by SeaSim:

  • Climate change – Increasing atmospheric carbon dioxide is driving two major changes in the world’s oceans: warming and acidification. SeaSim will enable assessment of the impacts of both these influences on a wide range of marine species as well as exploration of the capacity of these species to withstand or adapt to future climate.

Regions within the world’s oceans warm at different rates that vary with cycles such as El Niño and the Indian Ocean Dipole. The same is true of the rates at which atmospheric CO2 diffuses into the oceans making them more acidic. These variables also change daily and seasonally.

In addition, forecasting ecosystem impacts is fraught with uncertainty because each animal and plant species possesses different tolerances.

A whole-of-ecosystem understanding requires experiments with numerous species, their different life history stages and under numerous scenarios.

So there is a desperate need for experimental systems like SeaSim—able to house multiple species for long duration, while at the same time manipulating variables such as temperature and pH in a realistic manner.

With the sophisticated control systems and instrumentation of SeaSim, adding daily and seasonal variations to environmental variables becomes possible, vastly improving scientific outputs.

  • Pest management and intervention – Marine pests such as the crown-of-thorns starfish (COTS) are a major cause of coral cover loss across the Great Barrier Reef (GBR). Experiments conducted in SeaSim will provide insights into pest life cycles and will highlight potential vulnerabilities which can be exploited as part of management strategies.

Answering critical questions about COTS early life history and the factors which influence its survival, and hence the likelihood of outbreaks, has been stymied by a lack of high-level experimental facilities. SeaSim will provide the infrastructure to enable these questions to be studied.

  • Sediment and pollution – Development activities can greatly impact on the quality of water entering valuable marine ecosystems such as the GBR—for example, through the introduction of sediment from dredging and erosion, or of chemicals associated with farming, industrial and urban activity. SeaSim will allow exploration of the sensitivity of marine organisms to these influences and an assessment of their prospects for recovery.

Specialised control systems with complex dosing, well-defined water movement, and sophisticated sensors for turbidity and sediments are required to probe these questions.

  • Innovative seawater technologies – Realistic experiments to do with ocean environments require sophisticated technologies to replicate sunlight, manipulate water conditions and reproduce natural water flow. Such technologies will be developed, refined and deployed in SeaSim to underpin long-term and highly sensitive experimentation.
  • Model Organisms and Collections – Access to model organisms has transformed medicine and bioscience. Marine science is only now beginning to build a critical mass of available model species. SeaSim will be home to several such cultures, the first being corals.

Due to limitations in present experimental facilities most studies conducted to predict response of corals to climate change have used only a single generation and relatively short exposure periods. The new facilities associated with SeaSim will enable long-term, multigenerational studies allowing world-first research to assess the ability of corals to adapt to future climate.

Controlling the crown-of-thorns starfish

Eighteen arms, over 600 ovaries per female, more than 100 to 500 million eggs a year, hundreds of 4 cm spines tipped with toxins: a mummy crown-of-thorns is like something from Alien and it presents a clear and present danger to the Great Barrier Reef (GBR).

Crown-of-thorns starfish (COTS) are natural predators of the GBR, and are important in influencing the dynamics of the ecosystem.

Periodically the population of starfish booms and destroys large areas of reef.

Australian Institute of Marine Science (AIMS) data collected over 27 years shows that the GBR has lost about half its coral cover.

COTS is responsible for 42% of this damage, and it is the only threat we can seriously do anything about in the short term.

SeaSim will play a pivotal role in this, not only assisting researchers to understand the starfish life history and behaviour at a more sophisticated level, but also acting as an effective test-bed for any likely solutions to the COTS problem that emerge.

COTS have a wide Indo-Pacific distribution, from the Red Sea to the west coast of Central America. They feed on live coral, preferring hard corals, and possess few natural predators.

The starfish can grow very rapidly and have an ability to produce huge number of larvae under the right conditions.

COTS are infamous in Australia because they undergo massive population explosions or outbreaks, in which they move in waves along the GBR consuming masses of coral as they go. SeaSim will also be used to study what triggers these outbreaks.

One theory is that it has something to do with the increase in nutrients released into the GBR from land runoff during flooding.

Scientists are working on ways to control COTS without harming other organisms on the GBR.

The most recent suggestions focus on the susceptibility of the pest to disease.

Such control mechanisms may also involve using the starfish’s capacity for chemical communication to manage its behaviour, for example, creating aggregations of individuals to make infection easier and more efficient.

Profile

Adult COTS are disc-shaped and may have up to 21 arms, so they do not generally display the five-fold symmetry characteristic of many starfish.

They can grow to 80 cm across and come in a variety of colours, which vary from region to region, although dull grey-green is typical in Australian waters. COTS have excellent natural defences.

Their upper sides are covered in the spines from which they get their name and which contain a potent toxin. The animal rapidly curls itself into an impregnable ball if its vulnerable underbelly becomes exposed.

Feeding

The carnivorous COTS is slow moving and has an exclusive diet of living coral. It climbs onto its prey before extruding its stomach out through its mouth to cover an area comparable to its own diameter.

Coral tissue is then liquefied by digestive enzymes that are secreted from the stomach, allowing the COTS to absorb a nutrient-rich meal.

A single COTS can consume up to 10 square metres of living coral a year. Feeding rates vary with changing temperature but a study in the central GBR observed large adults consuming as much as 480 square centimetres a day in summer.

Although COTS prefer branching and table-shaped corals, they are able to eat virtually any coral on the reef, and will resort to feeding on soft corals if hard corals become scarce.

Predators

Only a handful of species have been recorded feeding on adult COTS, probably because the starfish presents a difficult prey target for many would-be predators. Among reef fish there are reports of pufferfish, triggerfish and the humphead wrasse eating COTS, but these large species are relatively rare on most coral reefs.

The large triton sea-snail is known to be an effective predator of COTS, but again this species is not usually abundant.

Juvenile COTS may be preyed on by some marine invertebrates, including shrimp, crabs and polychaete worms, and may also be targets for small generalist-feeding reef fish.

Data from the GBR has shown lower numbers of COTS on reefs in marine protected areas (MPAs).

This may be explained by high disappearance rates of juvenile COTS on these reefs, which in turn may result from increased predator abundance as MPAs create conditions for more natural, balanced food-chains.

Outbreaks

In ecological terms outbreaks are defined as situations where the density of an organism exceeds the level that available resources can sustain.

The first recorded outbreak of COTS on the GBR was at Green Island (near Cairns) in 1962. Since then there has been a severe outbreak every 13 to 14 years, with the last major outbreak in the late 1990s.

These outbreaks appear to begin in the northern GBR, and at their peak may cause upwards of 90% loss of coral cover on individual reefs as the wave of COTS outbreaks moves southward.

Control

Attempts to control COTS populations directly have so far largely been unsuccessful. Left unchecked, the outbreaking populations ultimately starve to death as they consume all available food sources.

Cutting up the starfish is not effective, as COTS are able to withstand severe damage and will eventually regrow missing arms.

But echinoderms—such as starfishes, sea urchins, sea cucumbers—are highly susceptible to disease, and despite their formidable defences, COTS are not exempt.

One theory suggests that disease spreads rapidly through a dense population of COTS, as the proximity of individuals to each other speeds up the transmission process, ultimately putting a swift end to the outbreak.

So the latest direction in COTS control is based on this susceptibility to disease. Scientists have been experimenting with injecting thiosulfate-citrate-bile-sucrose agar (TCBS) into COTS individuals.

This chemical has been shown to induce disease in the creature. In 2011, a research team published the first report of successful induction of transmissible disease in COTS using TCBS, and documented that no new pathogens were introduced into the marine environment as a result.

If this process can safely speed up the predisposition of COTS populations to disease, it may potentially have an important role to play in limiting outbreaks of this voracious starfish.

Another idea for speeding up the infection process is to use the starfish’s own communication system.

At present, we don’t know a lot about the behaviour of COTS, but we do know that the senses of smell and touch dominate their perception of the world around them.

Hence, they perceive and respond to chemical signals. And, like many other invertebrates, they use chemical communication—pheromones, attractants and repellents—to find food and mates, and as alarm and warning systems.

Insect biologists have long made use of such communication systems to collect specimens, monitor populations and control pests.

COTS, in particular, have a capacity to form high density aggregations, most likely based on chemical signalling.

They also seem to release alarm pheromones to warn of predators. So, it becomes possible on the one hand to gather COTS together to trap or infect them, and on the other to push them away from areas which need to be protected.

Such control methods could be made very specific to COTS, affecting no other species. And SeaSim would provide an ideal experimental apparatus for acquiring the necessary understanding of starfish sensory systems, and testing the application of chemical communications as a means of pest control.