2015 Expedition: First exploration of Carondelet Seamount in PIPA

Aquarium researchers and staff are on expedition to the remote Phoenix Islands Protected Area (PIPA) to study the natural history of the islands, surrounding reefs and connecting open water ecosystems. Research on the 2015 expedition will directly inform the management and maintenance of this world-renowned MPA. Today's post comes from the expedition's chief scientist in the field Dr. Sangeeta Mangubhai.

The Carondelet seamount sits in over 5000 meters of water, 65 miles southeast of Nikumaroro Atoll. Scientists from the New England Aquarium have attempted to dive this seamount three times, and each time we have been beaten back by large waves pounding on the top of the seamount. This time I made two special requests to the ocean navigation Gilbertese goddess Nei Manganibuka. Firstly, that she keep each and every diver safe while in the Phoenix Islands. And secondly, that she send us calm seas for the journey home so that we could safely dive and document the marine life on Carondelet seamount.

We all set our alarms at 6 a.m. and got up in the dark—tired and bleary-eyed. Remember, at this point we have been working 24 days straight. As the sun rose everyone was hanging off the top deck straining to find the seamount. I got my wish for calm seas, but that meant that there were no waves breaking on the seamount to let us know its actual location. Captain Jens from the Hanse Explorer had two different GPS coordinates for the site from two different maps, and neither was correct. My heart sank. This was looking for a needle in a very big haystack!

As the sun rose further, we saw a patch of pale blue about 800 meters ahead of us. Around this blue, waves were peaking, and ahead of us a school of fish starting jumping out of the water. We had found the seamount!

Descending to the seamount | Photo: Craig Cook

We dropped in on the top of the seamount, which is about 6 meters below the ocean surface, and headed straight down to 18 meters. The reefs reminded me instantly of some of the smaller islands in the Phoenix group. The coral community was dominated by massive and submassive colonies of Faviids and Porites species. Pounded by the ocean on all sides, the corals don’t grow very high, and almost hug the surface of the seamount. The diversity was not particularly high, with only 13 genera of coral recorded during our two dives. As we headed into the shallows, the coral cover decreased, though there were hundreds of small branching Acropora coral recruits scattered on the top of the seamount.

Old fishing line | Photo: Craig Cook

Professor Stuart Sandin, who did a rapid assessment of the fish diversity on Carondelet seamount, said the fish life was similar to what he has recorded on this trip throughout the Phoenix Islands group. He documented at least 150 species of fish over two dives. White tip sharks cruised around the shallows and slopes, and an aggregation of grey reef sharks kept to deeper water. However, the shark life was much lower than expected, suggesting the seamount may have experienced shark fishing sometime in its history. We found evidence of old fishing line on the seamount, strangling corals, trailing down the slopes.

As we head now back to Apia, Samoa, I cannot help think about how vulnerable remote seamounts are in the Pacific, and how much the management is lagging around these important habitats. Thanks to the efforts of the Kiribati government, the seamounts in the Phoenix Islands Protected Area are fully protected. They truly are a wonderful gift to humanity.

— Sangeeta

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