Wakatobi’s constantly monitored reef water quality
To protect the coral reefs that Wakatobi goes to great length to protect, the resort installed a coral reef health early warning system in fall 2009. Called the Rainbow Sensor Program, arrays of sensors have been installed at two popular dive sites ‘The Zoo’ and ‘Roma’.
The first data sent from the scientists in Los Angeles show the water at ‘Roma’ to be unusually free of organic components that are often the result of human sewage.
What this says is that Wakatobi’s policies of working with the local residents to protect their coral reefs from over fishing and human contaminants are working. Wakatobi’s reefs remain pristine, an unusual result for reefs that are visited by modern dive resorts.
"Both the Wakatobi Resort management AND the local population should be proud of this accomplishment."
- Tom Reynolds,
Rainbow Sensor Program Manager (www.rainbowsensor.com)
The Rainbow Sensor
The Rainbow Sensor works by comparing how the reef’s water attenuates the light.
As the diver knows, water removes the sunlight unevenly, removing first the red, then orange, yellow, blue, green and so on. What most divers don’t know is that attenuation in the blue wavelength is increased by the presence of organic material.
In normal, clear seawater the green attenuation is greater than the blue attenuation. However, with the coral reefs near locations with significant human population, human waste adds organic components to the seawater. The result is that the blue attenuation is actually greater than the green attenuation, sometimes by a significant amount. When that occurs, alarm bells should sound. The reef is at risk for an algal bloom that will stifle coral growth and degrade coral health.
At ‘Roma’ however, the blue attenuation is clearly less than the green attenuation, indicating water quality unpolluted by human waste. The site routinely exhibits diver visibility in excess of 30 meters using the Rainbow Sensor Program visibility measurement process. This is a significant and difficult accomplishment for reef management.
The top graph shows the light attenuation in the white (all wavelengths), green and blue region. A larger K means more attenuation. The K in the blue region is inversely proportional to the optical depth, a scientific term that relates very closely with what divers call visibility
The Rainbow Sensor (U.S. Patent8,368,891) measures the organic content of seawater. If the organic content becomes excessive, which is usually due to sewage from human habitation, the sewage acts as a fertilizer causing excessive alge growth. It is the unfortunate consequence of most diving locations that human habitation increases, and water quality suffers.
Fortunately, this is not the case at Wakatobi. Instrumentation is strategically placed as an early warning system that will register excessive organic content from human settlements invading the dive zones. The dive site known as The Zoo, displayed here, is actually quite close to a village. However, the results of both instrumentation and personal inspection since 2009 indicate that the dive sites are clear of human waste and invasive algae. The expected normal range would be between plus .02 and .04, and except for a coral spawn in September 2012, the organic index was well below normal.
The Rainbow Sensor, developed by Tom Reynolds and Burt Jones, measures organic content by comparing the decrease of light that occurs as it passes through seawater. In pure seawater the green light decreases more than the blue yeilding a negative organic index. However, as organic content increases the blue decrease becomes greater than the green, resulting in a positive organic index.
