Home Once Again

This post completes the blog for the 2010 Line Islands Expedition. We invite you to dip into the 45 earlier posts available in the blog archive. There you can follow the Fish, Benthic, and Microbe Teams as they visit the coral reefs at six of the Northern Line Islands, collecting data, samples, and adventures at each.

by Stuart Sandin, head researcher on the Fish Team

After spending the past four weeks surveying six of the Line Islands, our research teams have all made it home safely. Beyond personal health and safety, I am happy to report that we have successfully transported all of our data and samples back to our home institutions. And as a final bonus for our team members from the US, we returned in time to join family and friends for Thanksgiving. All in all, I would call this a successful trip.


Following our first visit to the Line Islands in 2005, our group spent countless hours trying to make sense of our observations. We had found that on intact coral reefs, the biomass of predatory fish can exceed that of their prey. How can a coral reef exist with so many predatory fish harassing their smaller compatriots? We had found that healthier coral reefs have much less seaweed but no increase in the biomass of the fish and other herbivores. Why does the same biomass of algae-eating herbivores control the seaweed effectively on intact reefs, but not on more impacted ecosystems? We had found that microbial concentrations were closely related to the abundance of seaweed on the reef. Are microbes thriving in the water chemistry created by the seaweed, or is the microbial ecology controlled by the geography and oceanography of the island? In this season of thanks and retrospection, my thoughts have returned to these questions, seeking to now incorporate our recent observations into our ecological understanding of coral reefs.


Battle Zones

by Katie Barott, member of the Microbe Team

Life on the reef is a constant battle for survival. For corals, the struggle begins as soon as the coral larva attaches itself to something on the bottom and starts to establish some space for itself. No space on the bottom is unoccupied. Every location is colonized by some kind of organism, be it corals, algae, sponges, or clams.

Corals are superb fighters. They fend off encroaching corals by stinging them with their tentacles and by ejecting their stomachs to digest them. These coral-coral battle zones are easy to spot; when two different corals meet, there's often a cleared band between the two where they've killed each other off. The same tactics are put to use to fight off invading algae. On healthy reefs, corals can maintain their territory, often beating back and even killing various types of algae. On degraded reefs, the tables are turned. Here the algae are the superior competitors with their own arsenal of weapons including chemical poisons and introducing bacteria that make the coral sick. Sometimes they directly overgrow and smother the coral.

On this expedition, we've been quantifying the interactions between corals and algae, documenting how many types of algae the corals are battling and who is winning at each of the atolls. On some of the human-impacted reefs, there are so few corals and so much algae that our surveys take only ~10 minutes each instead of the usual 45. At the more pristine sites we've seen beautiful reefs dominated by so many corals that our hands cramp up before we can write down all of the different coral species and the numbers of algal interactions. Although the algae don't dominate here, they are still present, lurking in the crevices and along the edges of the coral colonies. Even on a healthy reef the corals have to continually stand their ground against the algae, but on these reefs the corals are winning.

Christmas Corals

by Forest Rohwer, head researcher on the Microbe Team

In 2005, we surveyed the reefs along the western and southwestern sides of Christmas Atoll. There were lots of microbes and algae, the coral was mostly dead, and big fish were almost non-existence. This was particularly striking when compared to nearby reefs such as Kingman. Since 2005, our working group has been back to Christmas five times extending our survey around the entire island. Coral cover is very high as soon as you get away from the population centers. The south side in particular has some amazing reefs. But the reefs around London (the main population center located on the western side of the island) and extending around the northwest corner are dead with massive algal blooms, lots of microbes, and only small fish.

So what is causing these dead reefs? The debate takes many forms. There are the naysayers that argue what we are observing is only the natural variation. There is no real evidence supporting this stance. The places in the Line Islands where we observe trashed reefs are always either next to human population centers or are where humans have had a strong effect (e.g., the black reefs associated with shipwrecks on Kingman, Fanning, and Millennium). Some people argue that the upwelling of nutrients around Christmas causes the reef death there. However, upwelling does not have such an effect at the other Line Islands; similar zones on Jarvis, Starbuck, and Kingman support some of the most spectacular coral reefs anywhere. Furthermore, paleontological studies show that the now dead reefs on Christmas died only recently.

Christmas Is Delayed This Year

by Forest Rohwer, head researcher on the Microbe Team

The wrap-up of an expedition is always hectic. This is doubly true for the current trip because we needed to switch from a ship-board operation to a land-based one. This meant that two days were spent packing up everything on the ship and moving it on shore. First, the equipment had to be sorted into three groups: (1) things that we did not need for our remaining days on Christmas and that could thus be packed into a container; (2) heavy things that we needed on Christmas and that will be shipped home later on a cargo flight; and (3) light equipment that we need on Christmas that we can take back on the charter plane with us, i.e., effectively just data and samples. All of the sorted items had to be packed securely on pallets and lifted by crane off the Hanse Explorer. Then we all pitched in and moved the items we needed to the dive shop or our hotels. My room, for example, is now the water chemistry lab. We were doing well until we hit an unexpected delay yesterday.

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

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.

What's on TV Tonight?

by Nichole Price, member of the Benthic Team

Each night brings a different hit television program for us to watch on our big screen TV—the swirling waters on all sides illuminated by the faint glow of the deck lights of the Hanse Explorer. Each night the story line is the same: the large apex predators consume the smaller bait fish that, in turn, feed on the plankton attracted by our lights. The mesmerizing aspect of this never-ending night-time feeding frenzy is that the cast of characters changes at each island, and with them the feeding behavior spotlighted.

At Kingman Reef, we tuned in to 'Shark TV' for a show featuring the water literally boiling as the lurking gray reef sharks suddenly attacked flying fish en masse. At Fanning and Washington Islands, we switched channels to the more playful 'dolphin TV.' Here the bottlenose and spinner dolphins played with their food, pushing and nosing the squid that were flashing bright red and looking like underwater Rudolphs. Because the ocean is so deep just offshore of Jarvis, there we saw more pelagic species, including dozens of yellowfin tuna zipping through the water and breaking the surface to snag impossibly small fish. Tempting though it was, we refrained from throwing hooks into the water to catch those 50+ lb packages of fresh ahi. Jarvis is part of the newly formed US marine national monument, and these fish are protected. It was just as satisfying to watch 'tuna TV' and see predation in action, a rare event on most inhabited islands!

Some Like it Acidic—We Hope

by Nichole Price, member of the Benthic Team

 It is widely realized that the health and sustainability of coral reefs are under constant assault from a variety of human activities including overfishing and pollution, as well as from the rising sea surface temperatures due to human-driven climate change. But there is another threat, one recognized more recently and thus less widely known, that concerns scientists and policy makers alike: ocean acidification. This oceanographic process is driven by the release of excess carbon dioxide (CO2) into the atmosphere, a byproduct of our burning fossil fuels. As the carbon dioxide mixes with the ocean surface waters, the seawater chemistry changes in such a way that the carbonate needed by seaweeds and animals to form shells or external skeletons is less available. As a result, these organisms may find it harder to grow and their structures may be weaker. Essentially, the drop in pH (a unit of measure for acidity) is giving the reefs osteoporosis; the coral and algal skeletons that form the reef structure are expected to become more brittle and porous, and may even dissolve as conditions worsen. And worsen they will, as the excess carbon dioxide we have already sent into the atmosphere continues to move into the oceans.

On this brief cruise we cannot document the increasing acidity, as this process is happening over time periods measured in decades. Instead  our goal is to record the natural daily and seasonal variation in pH on a reef to help us establish the acid tolerances of the reef organisms. The pH rises during the day as the photosynthesizing algae take up CO2 from the water, falls again at night as all the organisms on the reef continue to respire, releasing CO2. What are the highs and lows that corals and seaweeds experience every day? What groups of species do we find clustered in the areas of the reef that experience naturally low pH? These will likely be best able to withstand the increasing acidity that lies ahead.

The Tent Brigade

by Jen Smith, head researcher on the Benthic Team

Prior to setting out on this expedition, I really had no idea how the Benthic Team was going to accomplish the goal we had set: performing three separate experiments at each island given no more than four days each. It seemed impossible. Now, after our fourth island, we have settled into a very efficient groove, our procedures have been streamlined.

On day one at a new island, our first task is to set up the seaweed (algae) growth experiments known as the DAWGS and described earlier here. Our goal is to measure the rate of growth of some common species. Because we have such a limited amount of time at each island—three days really isn't long enough—we need to get these experiments up and running as quickly as possible. Usually Jill and Gareth attach the small protective cages to the bottom while Nichole and I carefully secure our measured algae samples inside the cages with plastic clothespins. The cages are used to protect our samples from hungry herbivores. Then just prior to leaving an island we retrieve the cages with their samples and we measure the change in size of the algae.

A Few Sharky Places

by Jill Harris, member of the Benthic Team

We pulled up to our dive site at Jarvis this morning and, like every other morning, Gareth jumped into the water to set the anchor. This time, however, his head popped back up: “Hey, it’s pretty sharky down here.”

Everyone talks about how many sharks there are at Kingman Reef, one of the first stops of this trip. It's time that Jarvis should be given its rightful place in the shark rankings. The reef here is, indeed, pretty sharky. It is also very fishy: schools of big jacks, clouds of colorful anthias, and bright angelfish hiding behind coral heads. And it is coral-ly, if I can coin that word. Essentially every surface available on the bottom is covered in living, multicolored coral.

One reason Jarvis, Kingman, and Palmyra are so different from all the other reefs we are visiting, as well as from most reefs around the world, is that these three islands are all protected areas. All three are owned by the US and lie within the newly-created Pacific Remote Islands Marine National Monument, a 86,000 square mile reserve in the mid-Pacific. Within its boundaries, all fishing is banned within 50 miles of the shore. Access to the islands themselves is strictly controlled by the US Fish and Wildlife Service, thus providing a refuge for the countless seabirds sitting and nesting here. Except for occasional visits from scientists to study the reefs and curious looks from passing sailors, these places remain essentially apart from all human activities.

Go Away!

by Forest Rohwer, head researcher on the Microbe team

We've been setting out cameras to monitor the reef at night. This morning we went to get the cameras set out last night on the reef here at Jarvis Island. Two of us dropped into the water and were immediately surrounded by a school of 53 sharks. Their backs were hunched as they made rapid runs back and forth. They were saying "Go away!" I got right back out of the water—the first time ever because of sharks.

We then took the boat much closer to the reef, dropped immediately down to the bottom, and then stayed low while we retrieved all of the camaras. About 20-30 sharks followed us the whole time.

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