(29-09-08) We have travelled to the heart of Indonesia, Sulawesi, and there we dive in one of the active volcanoes of the "Ring of Fire", a strange world full of contrasts, where we see changing landscapes and places which conditions of life are difficult.

   After a few days of tourism in Jakarta and Manado, we arrived at Celebes Sea, which bathes with its crystal waters Sangihe Island, in north of Sulawesi. It is the end of the so-called Ring of Fire, the chain of islands of volcanic origin that starts in the Indo-Pacific and traverses across Indonesia.

   There are very few submarine volcanoes as the Banua Wuhu discovered, in relation to that on the surface of the Earth. Around 1.500 terrestrial volcanoes have been documented throughout the history, while many scientists say that beneath the surface of the seas could be hundreds of thousands.

   From the last century, about two hundred submerged volcanoes have been discovered. The only two decades of knowledge of phenomena such as hydrothermal currents or vents have given way to a new stage of research and more exhaustive knowledge of the oceans and their depths. It is a world we know very little about and a lot of assumptions are done, such as those ensuring that the submarine volcanoes are the origin of life on Earth.

    We are going to dive into one of the active submarine volcanoes in Indonesia, the Banua Wuhu, near Manhengetang Island. In 1835 the summit was an island that rose 90 meters above the surface, but successive eruptions and earthquakes made that in 1935 the volcano sinks into the sea. Now, the crater is submerged five meters and the slopes down to the abyss.

MANY SPECIES AT THE BEGINNING OF THE DIVE

    Some submarine volcanoes are biologically productive areas that are habitat for a multitude of corals, sponges and a wide variety of animal species. Starting the dive in the south of the summit of the volcano, in the opposite direction to clockwise, a prairie of coral welcomes us to a scenario where the green brown sulphurous remains coming from inside the volcano bring out.

    The dark bottom, product of volcanic sediments, is in contrast to the explosion of life that lurks in every corner. Here they live the host anemone and clown fish, along with elephant ear sponges and black ascidians, while the soft coral provides shelter for black sea slugs.

    And above them all, a huge green humphead parrotfish were swimming while feeding on coral tissues that crushed with its powerful teeth. Here there are parrot fish that are twenty meters long and, according to some scientists, the life expectancy of this species is about 30 years.

SLOPES GO DOWN TO 400 METERS

    As we dive around the volcano, whose slopes descend to 400 meters deep, the landscape changes and we see shoals of different species struggling to feed on the nutrients that the rich walls of volcano provide. We see, along with many other typical species of reef fish, grey triggerfish, surgeon fish, damselfishes and yellow angel fishes.

    After the various eruptions and earthquakes that have shaken the Banua Wuhu, the sediments and rocks the volcano has expelled from their entrails have gradually shaped the volcano's slopes. Over the slopes colonies of different species of coral live with all sizes and shapes gorgonians and spongefishes.

    But the barrel sponges are the protagonists of the landscape in this area of the volcano. We meet them as we dive to the Earth, and they look like artistic sculptures that decorate a big stage. Some of them are half a meter in diameter, and many shelter opportunistic species that take refuge in their interior.

    Barrel sponges provide a hiding place for the smallest and more timid fishes, the indolent globe fishes that look at us from the inside, and also for larger guests like a huge grouper that pleasantly contemplates the intense life in the aquarium around it.

    When we leave the barrel sponge formations behind, the landscape continues changing, and is no longer such a variety of species of large size. From the grey rocks some varieties of sponges are born. They are surprisingly hard when touching, such as chimney sponges. The green thin layer that covers them is algae and nutrients that are eaten by small damsel fishes, butterfly fish, grey triggerfishes and colourful chromis.

TABLE CORAL IN A GIANT FOREST OF ANEMONES AND SPONGES

    Midway, and as in a viewpoint over the abyss, we meet all kinds of sea anemones, corals and sponges that compete for the best place, dominated by a huge and striking example of table coral. This species is characterized by its trays, whose laminated platforms can reach three meters in diameter. Corals are fast growing and probably the least slow to regenerate.

    As we move forward the landscape continues to evolve, this time more clearly. The grey and yellow bottom and the layers of loose volcanic rock indicate a significant change in the environment.

    Now, temperature has noticeable increased. We started the dive with the water to 26ºC and our thermometer shows that we are a 30ºC. Animal life is limited, big fishes have disappeared, and there are only some long-nosed emperors and some smaller fishes like the copperband butterflyfish, angelfishes and Pseudanthias.

    The eastern side of the volcano clearly shows the telluric forces that have shaped the rocks and the rubbles of black stone announce that we are approaching the crater of the Banua Wuhu. A few meters forward, we are around the throat, in the platform of the crater, from where gas bubbles that come from the interior of the volcano arise.

IT IS LIKE A CRATER ON MARS, SUBMERGED IN BOLING WATER

    A thin layer of algae and sulphurous sediments cover the huge debris the volcano ejected in its last eruption. The landscape around us is spectacular due to its colour and the wild it seems. It is like a crater on the planet Mars submerged in a sea of boiling water.

    While we realised that the noise of gas bubbles is mixed with that of our breathing, we wonder how small shoals of damselfishes that are pecking the food on the rocks can survive in such hostile environment. It is an environment full of toxic gas bubbles, where the oxygen in water decreases by 30 percent, the salinity triples, the pH of water soars and temperature rises to 34ºC.

    Into the bubbles and rocked by the movements of the waves (we are 5 m. deep), it is time to wonder when this volcano will show its anger again. But, when that happens, we will know for sure that it is happening exactly where we are diving...

Texto y fotos: Jorge Keller, con información de
la Embajada de Indonesia en España, archivo BV, insideindonesia.org