Thursday, June 12, 2014

A rush to beat El Niño to the equator

It's official! The National Science Foundation has just funded our small team of scientists to document the effects of the coming El Niño event on coral reefs at Kiritimati Island, a remote atoll located in the central equatorial Pacific. During El Niño events, the waters surrounding these island warm by as much as five degrees Fahrenheit, causing appreciable thermal stress to the island's corals.

I've been waiting for an opportunity to witness an El Niño at Kiritimati first-hand since 1997, when as a 1st year graduate student I found myself at Kiritimati during the peak of the 1997-98 El Niño event - the largest event of the last century, by some metrics. The reef that I saw bore clear signs of thermal stress in the form of bleached coral colonies, many of which had been further compromised by boring clams and other invertebrates.

Since then, I've made a number of visits to Kiritimati in support of my climate research, which uses geochemical signals in living and so-called "fossil" coral skeletons to reconstruct El Niño events over the last 7,000 years. Last year, while diving in search of large coral colonies to drill for the Showtime documentary "Years of Living Dangerously", I noted that the corals had largely recovered - 15 years after the 1997/98 El Niño. We still have a very hard time finding a core that doesn't have a disturbance of some sort across the 1997/98 horizon (now covered by roughly a foot of additional coral growth). What happened to this reef during the El Niño? How bad did it get? Who were the survivors? And why?

Dr. Julia Baum
So when a combination of Pacific Ocean
Dr. Ruth Gates
conditions provided the first hazy view of a developing El Niño (see my post here), I called two renowned coral ecologists. One, Dr. Ruth Gates, is a colleague at my academic home-away-from-home, the University of Hawaii, where I'm on sabbatical. She recently won the Paul G. Allen Ocean Challenge to design corals that are more resilient to climate change. The second scientist is someone whose name I'd seen scrawled on dozens of storage crates on Kiritimati for the last 5 years, but had never met - Dr. Julia Baum, from University of Victoria. Dr. Baum has been conducting surveys and collecting samples of fish and corals at Kiritimati for years, aiming to evaluate the impact of anthropogenic stressors on this remote reef ecosystem. At the same time, an effort to document the physical oceanographic effects of the El Niño on nearby Palmyra Island was just taking shape, led by U. Hawaii postdoc Dr. Samantha Stevenson, with Dr. Mark Merrifield (UH) and Dr. Brian Powell (UH) as part of that team. We decided to join forces and design an integrated science plan that took advantage of the synergies among our team member's core expertise.

It didn't take long for us to realize we were posed to conduct ground-breaking research investigating the oceanographic and coral reef impacts of an ephemeral but global-scale climatic extreme - the 2014/2015 El Niño event. Now the only question was how to obtain funds to get down to the equator *before* the warming accelerates, sometime this summer. In mid-May, roughly one month after our initial conversations, we submitted two NSF 'RAPID' proposals - one to the Biology directorate, and one to the Geoscience directorate - which have now been funded. These precious and timely funds will allow us to visit Kiritimati and Palmyra in mid-August to conduct pre-event surveys of reef health, as well as install an array of environmental monitoring devices. We are scheduled to visit again in January 2015, close to the peak of the El Niño warming, and then again in May, 2015 as the warming dissipates.

Science-wise, we will be focused on characterizing the physical, geochemical, and ecological changes that occur at these islands over the course of the El Niño. For my part, I'll be collecting seawater temperature, salinity, and oxygen isotopes across the event, which I will use to compare to the oxygen isotopic record of the event as recorded in coral cores that I drill next year. Dr. Baum and her team will be conducting detailed ecological surveys and collecting samples of coral tissue for genomics analyses in Dr. Gates' lab. I am never sure which species of coral I core (they all look fairly similar), let alone the genetic makeup of the algal symbionts that inhabit individual coral colonies. I am betting that such information will yield important new insights about how to interpret the trove of paleoclimate records that I've amassed from Kiritimiti corals. For the ecologists' part, they are excited to have detailed information about environmental conditions at their far-flung survey sights - conditions that may explain why some reefs fare better or worse through this natural climate extreme. The physical oceanographers will deploy a dense array of current meters as well as CTDs to log ocean temperature and salinity. The observed time series will be compared to the output from an isotope-equippped ocean model that Dr. Stevenson has been developing, as well as the resulting isotopic time series from corals that span the event.

In the long run, our study will provide a snapshot of how the remote coral reefs on Kiritimati were reshaped by the 2014-15 El Niño, and isolate some of the key factors in determining the resilience of these valuable coral reef ecosystems to such natural temperature extremes. Given that natural climate extremes occur on top of a baseline of steady anthropogenic warming, results from such short-term studies may hold the key to understanding the long-term impacts of climate change on reef ecosystems.


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