We wrapped up our last night of sampling doing some night measurements of bleached and pigmented colonies of Porites compressa. We were at a land-based site thankfully (!) but it was still unnerving having the instrumentation precariously situated on a rock wall with crashing waves below. Here is Tong operating the instrument and taking notes of the sampling times by flashlight, while Colleen is wading below holding the instrument (keeping it from falling into the ocean) and Amy snorkeling in the water holding the tubing at the coral surfaces (while waves are crashing over her!). Despite the craziness, we obtained beautiful nighttime superoxide measurements from the corals! What a way to end the trip! 

We have had a busy few days (hence the lack of updates). During this time, we've hit our stride and optimized the instrumentation for making in situ superoxide measurements. Despite a few hiccups here and there, we have had remarkable success in making these measurements! The data are better than we had expected or even hoped for! We have measured superoxide concentrations from both bleached and pigmented colonies of five different coral species, Porites compressa, Porites lobata, Montipora capitata, Pocillopora damicornis, and Fungia scutaria, from five different reefs. The depth of corals has ranged from less than a foot to up to 5 feet. We have a lot of data modeling ahead of us!

An assortment of coral species included in our analysis. Species shown here include P. compressa (top left), F. scutaria (center), and a bleached M. capitata (bottom center).

The majority of the M. capitata colonies that we have seen are severely bleached, as illustrated by the colony to the left.

The bleaching event and our research gains press attention

Yesterday Amy and Colleen were asked to participate in a media event about the coral bleaching event that was hosted by Hawaii's Department of Land and Natural Resources (DLNR)  We spoke to reporters about our work examining production of superoxide, the main oxygen radical thought responsible for bleaching, from the corals.  Our message to the  press included our gratitude to the DLNR and the scientists at the Hawaii Institute of Marine Biology for the logistical support and for involving us in a much larger frame of research surrounding the bleaching event.  We also explained why superoxide is so important to measure in conjunction to this bleaching event, the difficulties in measuring superoxide (it's lifespan is only a couple minutes!), and how our research may help scientists uncover the mechanisms involved in the disassociation between the corals and their algal symbionts. 

Measuring superoxide from corals in Kaneohe Bay

"Can this be my office everyday?"

Today was our first day out on Kaneohe Bay conducting superoxide measurements on bleaching and non-bleaching corals.  We packed up our gear, loaded it on the boat and headed out into the beautiful bay.  We settled on a site and Colleen and Tong got to work setting up the instrument while Laura and Amy scouted out potential corals.  Although in theory everything should work just as well as yesterday, we were all a bit jittery about all of the unknowns, including waves, a moving boat, and the occasional shark cruising by (well, at least those of us in the water had that on our mind).  Our jitters soon evaporated as the data starting rolling in and we were detecting superoxide from corals!  We had a very successful day, and measured superoxide fluxes from many corals on two separate reefs.

Amy Apprill

Measuring superoxide on shallow coral reefs.

Successful testing of equipment...and then a rainstorm!

Our team consisting of Woods Hole Oceanographic Institution scientists Colleen Hansel, Amy Apprill, post-doc Tong Zhang and graduate student Laura Weber arrived in Oahu, Hawaii.  We are staying at the Hawaii Institute of Marine Biology (HIMB), part of the University of Hawaii, located on Coconut Island.  Today we were warmly welcomed by the scientists, and learned of the enormous amount of research and effort by HIMB and other local scientists on the bleaching event.  

 

The first superoxide measurements on
corals (and actually ever for marine waters!)

Today we needed to test out our equipment and approach before we packed up everything and took it out on the boat.  We found some corals residing off the Point Lab at HIMB that were shallow enough for us to measure. Fortunately, we were able to get measurements on a few corals before the rain hit.  We didn’t have time to move the gear before a rainstorm approached, so we held trash bags over it while we weathered the storm and dreamed of developing a waterproof instrument.

Amy Apprill

Introducing the mystery.........

We are conducting our research on the corals bleaching in Kaneohe Bay, Oahu.

Corals are bleaching. Right now, in majestic Hawaii and throughout the northwestern Hawaiian Islands. Depending on the severity of bleaching, the corals may not recover. Coral bleaching is the loss of symbiotic algae that reside within the tissues of the coral. Elevated surface seawater temperature is to blame – at least in part. In actuality, it is an accomplice to the crime. Elevated temperature leads to the formation of the chemical weapon responsible for coral bleaching – superoxide – a reactive chemical that is an oxygen radical. High levels of this chemical lead to expulsion of the algae and subsequent bleaching and can initiate cell death of the coral host. But, who is wielding this weapon? And, why?

We have a long list of suspects – the coral host, the symbiotic algae Symbiodinium, or the other coral-hosted bacteria. The evidence thus far has pointed to Symbiodinium as the perpetrator. And in fact, coral bleaching is attributed to overproduction of superoxide by Symbiodinium in response to light and temperature stress. But, has Symbiodinium received a fair trial? To date, the evidence against Symbiodinium has been indirect. There are no actual measurements of superoxide production from corals or the algae during the bleaching process and the source of and triggers for superoxide formation are not actually clear.

We hope to unravel this mystery – at least in part – by conducting the first field-based (in situ) superoxide measurements from bleaching and non-bleaching corals during the natural bleaching event occurring in Kaneohe Bay, Oahu. But collecting this evidence is tricky. Superoxide only has a lifetime of a few minutes. It’s hard to catch. There are no instruments that we can put in the water to measure it. But, we may have a way – by setting up a boat-based laboratory with an optimized detector system. By doing so, we hope to obtain clues as to whom is making superoxide, how this varies with coral species, and how superoxide links to coral bleaching. Is Symbiodinium truly to blame? The jury’s still out…

Colleen Hansel