As I write these lines, we are flying on a small plane bound to Honolulu. Our expedition to Kingman is finished. Most of our team is sleeping, reading, or listening to music in the only introvert environment of the last three weeks. The silence of the return flight contrasts with our excitement three weeks ago, when we were filled with anticipation. Today we are filled with experience and memories.

We just came back from our third dive. The sea was so flat that, if it hadn't been for little Isla Maxima, we would never have known we were on an atoll. The breakers were absent. All we could see was a spectrum of blues, the sky merging with the sea.

We were especially happy today. We have finished all of our data collecting, accomplishing more than we expected at the beginning of the expedition.

Last night was rocky; the Searcher swung with the swell all night long. That made us especially eager to jump in the water and dive a hundred feet below the surface, where the swell is barely discernible. We are tired after eighteen full days of diving, and waking up in the morning is increasingly difficult; but there is something that keeps us going. It is the realization that we cannot waste a minute in this unique atoll. Laziness and idleness are alien words here, and we don't have enough hours to dive as much as we would like. The mere thought of meeting the sharks again, or hovering over a coral infinity, triggers our adrenaline.

The Kingman reef ecosystem is a complex living machine composed of many thousands of species, which are linked by relationships of different natures. Some organisms, such as corals, create habitat for others; others, such as sea cucumbers, work as garbage cleaners processing debris. But nothing characterizes better the struggle for existence than the relationship between predator and prey. Predation is a rather unfair relationship in which there is always a winner-and a loser. So engrained is it in our perception of nature, that students of linkages between species in an ecosystem have consistently worked on food webs and often ignored most other kinds of relationships.

Yesterday I wrote in my journal about how easy it is to get accustomed to something extraordinary.

A room warden at the Prado Museum will probably not be as excited at the sight of a masterpiece by Velazquez as a tourist will. Likewise, after 10 days of diving at Kingman we appear to be used to seeing sharks, dozens of large red snappers, and healthy corals on every dive. We have seen between five and 24 sharks on every single dive. It would take years of diving in the Caribbean to see as many sharks–without feeding, of course.

First, a healthy reef is not healthy everywhere. In the same way that a falling giant tree will create a clearing in the jungle and start a competition among younger trees to reach the sky, a coral reef will have patches of death that will become alive in due time.
    This morning we dove at a site near La Paloma pass, the only significant channel connecting the lagoon and the fore reef on the southern side of Kingman. Ten meters below our boat, the bottom was covered with coral rubble. A few hundred meters west or east, the corals are healthy and form a thick forest. But this patch is a reminder that there are greater forces operating in the world, and that even remote reefs cannot escape from them.
    Kingman was impacted by a Pacific-wide warming event in 1997-8, called El Niño. The surface waters became too warm for too long, many corals bleached, and some of these died. Corals died, but they recovered in most of the atoll. Why did they not recover at the site we visited this morning? Probably because this site is immediately west of La Paloma.
    The lagoon breathes with the tides, inhaling clean water from the central Pacific on the flow tide, and exhaling water filled with sediment from the lagoon on the ebb tide. The outgoing water from the lagoon is pushed westwards by the surface waves, which are in turn created by the trade winds, blowing mostly from east to west. This might have inhibited the recovery of the corals to date. However, the good news is that the rubble is scattered with thousands of small corals.
    Replenishment may take a while, but it is on its way. Paraphrasing Inspector Clouseau, everything nature does is carefully planned—or at least until we started to mess things up. Second, unlike what many people believe, sharks have not evolved for 300 million years with the sole mission of devouring every single human that sets a fin in the ocean. I mentioned earlier that sometimes sharks get quite close to us. Today, however, we could not get them close enough.
    The usual protocol consists of us jumping in the water, a dozen sharks coming to check us out, and then losing interest and leaving. They may come back during the dive, or especially when we climb back to the boat; they appear particularly bold at dusk. However, they never made any attempt to check if we taste good.
    This is what a healthy coral reef is supposed to be: abundant predators that have no particular interest in strange creatures with one large eye and two tails, and who produce noisy bubbles. The rest is all fantasy for cheap reality shows that appear to have replaced good natural history.

The goal of our expedition is manifold, but it could be condensed into two main goals. First, we aim at describing a healthy coral atoll in its entirety or, more humbly, within the limits of our expertise and physiological limits. That is, we will survey the reef ecosystem from viruses to sharks, from the shallow giant clam beds in the lagoon to the fore reef 20 meters deep.
    To undertake such an ambitious task we have a four-person fish team, a two-person coral and algal team, and a two-person microbial team. The fish team is composed of Ed DeMartini, Alan Friedlander, Stuart Sandin, and myself. We dive three times a day and identify, count, and estimate the size of all fishes within two meters on either side of 25 meter-long lines, or belt transects. We carry out three such transects per dive, and expect to encounter more than 200 species of reef fishes in our surveys. Using the data collected in the field we will estimate the number of grams of each fish species per Meter Square, or biomass. Fish biomass is the single best indicator of fishing pressure, and since Kingman is unfished and protected, it should have one of the greatest fish biomasses in the tropics.
    Jim Maragos and Jen Smith constitute our coral and algal team. They dive twice in the morning. Jen takes dozens of photos of the bottom using a small digital camera attached to a frame made of PVC pipes - a “quadpod”- that allows her to always photograph the same surface in order to obtain comparable samples. She will then spend hundreds of hours in front of her computer, calculating what percentage of the bottom is covered by different species of algae and corals. Meanwhile, Jim Maragos identifies all coral species in situ, and measures the size of coral colonies, including the smallest ones that are indicative of replenishment of the population. A coral reef is a reef made of coral, thus we expect Kingman to be overwhelmingly composed of live coral, and scarce seaweed.
    The microbial team is composed of Linda Wegley and Mark Hatay. They dive in the morning and collect water samples in hard plastic bottles the size of poster tubes. They will then count the number of microbes that inhabit every milliliter of seawater around the atoll, and determine how fast bacteria reproduce. The rate of bacterial growth is a good indicator of how “clean” the ecosystem is.
    In addition, Christian MacDonald, our diving safety officer, supervises our diving operation and ensures that we conduct our daily activities safely. In other words, he makes sure all of us return to the Searcher every day. That is no small task.
    As I mentioned yesterday, our goal is not conducting scientific studies for the sake of science, but to obtain a rigorous description of a healthy coral atoll so that we can use it as baseline for coral reef conservation.
    Our second aim is to make the public aware of what we find, and to show them why it matters. To achieve this goal we have one of the best underwater photographers in the world, Brian Skerry, who is shooting for a story that will appear in National Geographic magazine. Brian typically takes a boat and an assistant, and goes diving for four or five straight hours. He then comes back to the boat with amazing photos, although he never seems totally happy, and goes back to the same place to make a yet – incredibly - better shot.
    Finally, our young videographer, Tyler Rowe, is shooting with a high-definition video camera in an underwater housing. He will produce short videos for what I call a communication experiment: a scientific expedition seen through the eyes of a teenager. We wish more young people were attracted by natural history, and hope these videos will help recruit some of them.
    The crew of the Searcher is a terrific team that deserves a full daily dispatch...

What’s the world of the reef predators at Kingman like? What’s a place like where most of the fish biomass is at the top?
    In 2005 Ed DeMartini, Alan Friedlander, Stuart Sandin, and I conducted surveys of reef fishes at ten sites along the eastern and southern sides of Kingman. At each site we laid lines on the bottom and identified, counted, and visually estimated the size of all fishes within two meters (6.6 feet) on either side of the lines. We call these belt transects, of which a team of two conducted three per site. On each transect, two of us surveyed a surface of 200 square meters (2,153 square feet). We can later use the relationship between length and weight for every species and calculate the weight of reef fishes within a determined surface, or biomass. This is a standard method for estimating the abundance and biomass of reef fishes, and researchers in tropical and temperate seas use it frequently.
    Our 2005 study yielded a surprising result. Unlike most coral reefs that had been studied previously, top predators accounted for 85 percent of the total fish biomass on the fore reef of Kingman. To better grasp this biological implausibility, imagine the African plains with five pounds of lions per pound of wildebeest and zebra.
    The great abundance of predators has effects that propagate across the food chain, and we could witness some of these effects yesterday and today. In human-dominated reefs, where large predators have been fished out, the water column above the reef is filled with small fishes only a few inches in length, which eat some of the smallest inhabitants of the reef, the plankton. In Kingman, sharks and red snappers dominate the water column; the rest of the fishes keep a low profile. So low is their profile that they seldom venture a few inches above the bottom.
    Similar behavior has been observed at Yellowstone National Park after the reintroduction of wolves. Deer do not venture as much as before in the open meadows, and they spend more time watching for wolves. Their grazing impact on the forest is, therefore, greatly reduced. But we still do not know how the putative reduced activity of the smaller fishes affects the functioning of the Kingman reef ecosystem.
    When we were counting fishes yesterday before dusk, a dozen gray reef sharks came to inspect us and swam too close for our comfort. The landscape of fear also has an impact on us. In order to accomplish our scientific goals, we should ignore the sharks and focus. However, it is difficult to ignore such formidable animals while they swim effortlessly through the water. Whatever we do, we will also keep a low profile.

“If it’s not a hurricane, it’s a tsunami,” said fish expert Alan Friedlander on the diving deck of the MV Searcher. We could not help but laugh out loud. We had arrived at Kingman, but were now threatened with a tsunami alert.
    We left Palmyra Atoll shortly after eight this morning under a hot sun already high in the pale blue sky. Brown boobies and sooty terns followed the Searcher like surfers enjoying a slow, never-breaking wave. Outside the lagoon, bottlenose dolphins greeted us with their jumps and smiling faces. We were on our way to our dream.
    On most nautical charts, Kingman Reef is off a couple of miles, so locating it is not straightforward, despite the satellite positioning systems that are available to us. Kingman is not a typical atoll, since it does not have any emerging land except for two small islands made of coral rubble. Hence radar is not very useful either, especially on rough days when waves are tall as the islands.
    From space, Kingman looks like a boomerang pointing east. The seas around it are usually rough, and ships tend to avoid it. However, we had great weather and Jon Littenberg, the captain of the Searcher, negotiated a deep channel on the western side of the atoll and anchored at the easternmost point of the lagoon.
    Everything seemed perfect. Then the tsunami alert came through the satellite weather alert system. Brian Skerry, with a grin, added: “And we should expect locust for tomorrow...”

    We woke up to a calm sea in our sheltered lagoon. There were no features to be seen outside, except the ripples on the ocean and the two low islands in the distance, bleached by centuries of unforgiving tropical sun. We ate a continental breakfast served in the comfort of the galley of the Searcher, and spoke softly, as though we were afraid to disturb a holy place.
    After breakfast, the crew of the Searcher deployed the three small boats, and we prepared for our first dive. We left shortly after nine o’clock, heading to La Paloma pass, the only channel in this part of the atoll that is navigable by small boats, which allows us to move quickly between the Searcher and the southern side of Kingman. The sea was so calm that it was not easy to distinguish the pass from the reef crest.
    Finally, after a year of preparation, we dove on the fore reef of Kingman. We were anxious about what we would find underwater, but our fears disappeared as soon as we jumped in the water. We found a reef as healthy as that we surveyed in 2005, a clean reef with large staghorn and table corals, and virtually no seaweed; a reef with sharks and large snappers, the top predators on this reef.
    Tyler Rowe, our 18 year-old videographer and expedition rookie, remarked after his first dive: “There is nothing but blue on the surface, but down there it’s a world apart.” Nothing can describe Kingman better.
    Tomorrow I will describe what a world of predators is like.