The Snow Fields of Christmas Atoll

The Hanse Explorer has arrived at Christmas Island, the last of the six to be visited on this expedition.Christmas is home to the largest human population of any of the Line Islands. Among the four islands surveyed in 2005, the reefs near the villages also had the largest population of pathogenic microbes, the smallest amount of coral cover, the fewest top predators, the lowest CHI. A more complete survey around the island is planned this time, but now the remaining work will be done from a dive charter boat. Everything has been offloaded from the Hanse Explorerso that it can proceed on to Tahiti.In a couple of days, once again the tons of equipment will be carefully packed for shipment with the extra challenge that now there are also the biological samples to be kept frozen all the way home.

by Forest Rohwer, head researcher on the Microbe Team

A hypersaline pond on Christmas Atoll. Photograph by Forest Rohwer.

My five-year-old daughter, Willow, had asked me, “Dad, are there Christmas trees on Christmas Atoll?” Yesterday, Stuart and I got the chance to go looking around the island to answer this important ecological question.

The trip started at 5:30 am when we delivered the doctor, diving safety officer, and one of the scientists to shore so they could catch a plane back to Honolulu. Due to a miscommunication, we were about two hours late. They made a mad dash to the plane just minutes before it took off. In the meantime, Stuart and I sat on the beach and idly tossed pebbles of dead coral at an innocent tree for about two and a half hours. Eventually, our contact/driver returned. Our people had made it on board the plane, but two of the coolers filled with precious samples did not. We loaded the coolers back into the Zodiac and started off to ferry them back to the ship. As we went through the lagoon channel, we were met by 3 meter waves breaking off our bow due to a big swell that had kicked up. That alone wouldn’t have been so bad, but when combined with the strong current rushing out from the lagoon it put us in a seriously bad position. Another small boat just ahead of us got caught in the surf and was pushed roughly back onto shore. Stuart managed to get us over the waves and into blue water. We had both aged a couple of years in about three minutes.

After dropping the coolers off at the ship, we headed back to the island. The waves were much easier to manage as we surfed back in. After tying up the boat, we spent the next two hours being driven between Kiribati immigration, customs, and the loading dock. After much confusion, phoning of bosses, and reading of official papers, it was established that the best thing to do was to clear the ship…the next day. From the customs office we proceeded to the dive charter that we will be using for our research work the rest of the time on Christmas. Here we sat for another two hours and tossed coral pebbles at other pieces of coral.

Finally, we found a car to rent and headed off to explore the island. Our goal was to find the hypersaline ponds that are at the northern end of the lagoon. About a quarter of the total area of Christmas Atoll is covered by such ponds and lakes, some merely brackish and others quite saline. These ponds are recharged occasionally with fresh water by torrential rains associated with El Niño events. As the water evaporate out of them again during the dry periods, the salinity increases to the point that eventually only salt-tolerant microbes and milkfish live there. The milkfish are considered some of the best food on the island. They grow to a meter or two in length and have long been raised by traditional aquaculture methods throughout Southeast Asia and on some Pacific islands. But we were after the microbes. The ponds look like Christmas: red on the bottom, green water, and white snow covering the shores. It looks like a winter wonderland in the tropics. The “snow” is actually crystallized salt, and the “snowballs” blowing down the beach are frothed polysaccharides and proteins. Most of the exotic colors come from the microbes. We gathered samples for analysis back in San Diego.

From the salt ponds, we headed south an hour’s drive to the coast. On this part of the island, the tidal flats were crawling with crabs, flat worms, brittle stars, etc. There were also spectacular fossil corals, part of an ancient reef. Walking around here, we could see how the reef was structured. This was just one more reminder of how amazing Christmas Atoll really is. Though only about 27 miles long and 16 miles wide in the wide half, in our five hours of driving we didn’t even come close to seeing most of it. Geologically it is an atoll made completely of coral and other calcifying organisms. The coral extends down and down into the depths, and dwarfs everything constructed here above the water by man.

After driving back to town, we dropped off the car and walked back to the Zodiac. As we headed out of the lagoon, the waves started to break off our bow again. Common sense trumped machismo. We returned to shore. As we walked back into town to find a hotel, we saw a courtyard with palm trees decorated with Christmas lights. So, yes, Willow, there are Christmas trees and even “snowballs” on Christmas Atoll.