Several months ago a deep reef from French Polynesia made the news as something completely new because we didn’t know about the existence of these deeper reefs. Nevertheless it’s a good thing that corals are in the news, and people start to show more interest in them.
Last month during a North Sulawesi Reef Survey we were fortunate enough to survey such a reef and the extent of these underwater world wonder is truly mind blowing. Even if few shapes dominate these habitats, the diversity of species right in the middle of the coral triangle is really amazing.
A very unique habitat
The dive sites we found were truly mesmerizing. Located in a sheltered, turbid large bay, it was an infinite expanse of rolling hills, dominated by thin foliate corals and speckled with truly unique ‘cherry’ species such as Nemenzophyllia turbida in the middle. The 75 minutes of Diving bliss we enjoyed on this particular spot was way too short, and can’t wait to go back there.
The shallow part:
When we descended upon that reef, the first thing we encountered while going down below the very shallow rubble field, is a dense thick forest of Acropora teres, Acropora abrolhosensis, Acropora horrida, Acropora exquisita, Acropora halmaherae… We already know, it’s going to be a good dive!
The deeper foliate part:
Once we pass the 15 m (45 ft) mark, the dense Acropora forest is replaced by deep water corals, dominated by foliate species such as Pachyseris speciosa as far as we eyes can see.
Pachyseris speciosa is the dominant species, growing depending on the depth in slightly different rose size and shape. Getting wider, flatter and spaced out as we go down.
But Pachyseris speciosa is not the only foliate species. A full spectrum of other species produce huge laminar colonies competing with each other. Mycedium robokaki is one of them.
Other species of foliate species, include Oxypora lacera, Echinopora lamellosa and Echinopora pacificus but unlike French Polynesia deep reefs, Porites rus is nowhere to be seen since it is unable to compete with the many other species more adapted to this environment. But some smaller colonies of laminar Montipora are present.
Still some interesting Acropora:
As usual, Acropora are always the center of our attention, especially in the deeper area. We were surprised to be gratified with some large fields of Acropora carduus, Acropora echinata, and Acropora navini. They were very discrete, positioned next to this large roses, and it took time and close up observation, to notice it wasn’t rubble fields, but perfectly healthy Acropora beds. They were often in the transition zone between the thick branching Acropora forest and the laminar coral fields.
Speckled Coral Cherries:
Among the laminar corals, we were greeted with some truly amazing and rare corals, such as Nemenzophyllia turbida in the deeper part, 30 m (90ft).
This quite rare and really underrated corals is a beautiful sight under water. The flattened bubble are really a unique feature to this species. The colonies were quite big, easily over 2 m wide. We didn’t have time to really spend some time and try to observe the associated fauna, we have another reason to get back there!
Another quite interesting find we found was a huge colony of Euphyllia glabrescens. Not a very common coral, but really hard to find in descent size. It looks like in shallow water the branching structure becomes weak, and they never reach large size. While in deeper water, even if the colony is not really homogenous, it’s still of an impressive size. With different polyps belonging to the same colony sticking out of the substrate.
A very close relative was also present at 30m (90ft): Fimbriaphyllia ancora.
Large colonies of another common LPS coral was also present: Goniopora sp
Even some large fields of soft corals: Sarcophyton sp, were present, few Sinularia… the full set of the coral family was striving in this reef.
Plenty of food for a striving reef!
After waking up from this daydream, the only question coming to our mind is how is it possible? And the only answer is food! North Sulawesi lays at the entrance of the Indonesian ‘flow through’, where the Pacific empties itself into the Indian Ocean, getting through the Indonesian archipelago and this bay is right at the entrance of it. This reef within the bay is where the back eddy is created and where the food is dropped on the reef, directly within the mouths of these hungry corals!
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