The Briny Deep - a post by Kristie Cobb Hacke

Yesterday morning on a tour of the bridge of the Steward Johnson following the deployment of the submersible, we had the opportunity to chat with some of the sub crew and a pilot. During our chat they were sharing stories of other dives. One in particular was incredibly interesting to me because it continues the idea of worlds within worlds (the sneeze theory). Craig Caddigan was mentioning that he piloted the submersible to a location in the Gulf of Mexico that contained an “underwater lake.” The lake was a dense brine pool, made up of water with an incredibly high density due to salinity and found at over 2000 feet depth. Craig described landing the sub on the lack and bouncing along the surface and creating ripples. The brine area has its own waves and “beach”, in this case surrounded by a 10’ ring of mussels. The mussels use methane as their primary food source. The submersible was unable to descend into the brine lake because it was too dense, but they did take along some tools that could sample the contents.

A brine pool in the Gulf of Mexico

What is amazing to me is that this brine sea is contained within the ocean. Do the animals that live around this area know that they are living in a sea within a larger ocean? When I sit on the beach am I merely sitting on the edge of a pool within someone else’s greater ocean. Am I at risk of being someone else’s sample? These big thinking questions are what keep me going but the scientists aboard the Abrolhos are focused on the small things that make up the ocean. Right now they are collecting small coral samples, sediment, rock, fish and other items. During the cruise other members of the HBOI staff have been creating maps so that the scientists can use them for future trips or they can clearly note the location of sample and sediment collections. The CTD collected water at the same locations where the submersible was deployed, so that bacteria and viruses can be measured and identified in the water column. The hope is that each of these small pieces can create a larger overall understanding of the structure and biology of the Abrolhos reef.

There it is again!

That awesome feeling when you discover a species you never knew existed!  I just wrote about this in my last post, but it happened again today when I came across this video (cap tip to @support4oceans on Twitter) of Stygiomedusa, a giant jellyfish, seen for the first time in the Gulf of Mexico.  There’s not much to say because Mark Benfield from LSU says it all, but just consider that this thing has a bell the size of a beach umbrella and tentacles as long as a school bus!

Dancing with a Giant - the reprise

You might remember an earlier post about Dancing with a Giant, in which I was pretty emotional about an amazing swim I had just done with a whale shark in Mexico.  Well I can now share the video of that animal.  There’s a good bit at around 0:50 where you can see right into his mouth, and see the filter pads they use for sieving their planktonic food from the water. In this case, he’s filtering fish eggs, which you can’t see because they are too small and are also transparent; thats good for us though, because it gives us a nice clear view.  Without further ado then, here he is, MXA-181:

Dancing with a Giant

A lot of people think science is soulless, sterile or austere in its objectivity; there’s a prevalent stereotype of the scientist as a lab nerd in a white coat, out of touch with the “real world” and with the more emotive aspects of life. That couldn’t be further from the truth, of course. Most scientists I know – me included - are motivated precisely by a profound wonder and amazement for the natural world around them; its usually why they get into science in the first place. When biologists go into the field, they often end up reconnecting with those feelings, established during their formative years, and end up resorting to a sort of childish state of pure joy over whatever biological phenomenon that they happen to be studying. I just had such an experience, one that was so extraordinary that it may well have changed the way I think about biology forever.

As part of the research program at Georgia Aquarium, we are in Mexico to study the biology of whale sharks, which gather annually in the coastal waters of Quintana Roo, from Isla Mujeres north and west to Isla Holbox. Its bliss just to be out on the water again (its been a while), admiring the everchanging seascape, marveling at the myriad forms of life that make their home in the ocean, and reminding yourself that the endless stream of doom and gloom news about “the environment” isn’t really the full picture. Flying fish skip from wave crest to wave crest, pursued by sinister-looking frigate birds that swoop in to grab them on the wing, while turtles lazily periscope their heads above the surface to spy on pods of spotted dolphins that race around as if there were somewhere important that they really needed to be.

In due time, we found our objective, a group of whale sharks feeding at the surface, attended by a flotilla of ecotourist boats. Each of our team had a chance to swim alongside these spectacular behemoths as they were cruising effortlessly among the boats and patches of food, at speeds that exhausted a mere human to match.  We also photographed many of them for an identification database.  Then we took some time to gather data on the physical and chemical properties of the water, during which the ecotour boats petered away, returning their cargo of tourists to their respective all-inclusives in time for lunch and leaving us with the whale sharks mostly to ourselves. They continued to feed, constantly inhaling bathtubs of plankton from the surface tension, their gills flapping loosely on the rejected water current like flags in a gentle breeze.

It was at this point that I got in the water a second time. Rafael, our captain and colleague from Project Domino, had put us on a large animal that was feeding below the surface in a more vertical pose than their normal surface “ram filtering” style. This more upright type of feeding, which they use when food is especially dense, sees their tail sink down towards the bottom and cease its rhythmic swinging and, hanging suspended like this, the animal begins to actively suck in enormous gulps of water. In this state I was able to approach the animal much more closely, a large male, and to see how each pulse of that fantastic mouth was pulling in not only water but tiny silver vortices of air down from the surface, such was the force of suction. He was suspended like this for what seemed like an eternity, but was realistically perhaps 15 or 20 minutes, during which he continued to feed and appeared completely indifferent to my presence. I was able to swim over every part of his massive frame and inspect every detail, from his tremendous girth to the creamy white belly distended with food, and from the remoras that pestered his every fin to the tiny copepod parasites grazing across his skin like herds of hoofstock might roam a savannah.  His body was home to a veritable community of hangers-on. I watched his eye roll carelessly over me while he continued to inhale vast amounts of water and plankton, all of which disappeared into that cavernous mouth with its 20 jet-black filtering pads. We continued to dance together like this – or rather I danced around him - close enough that I could have reached out to touch him at any point, until with a tiny shake of his head and a hefty sweep of his tail he was done with the meal and headed off in search of another patch to vacuum, leaving me breathless from a cocktail equal parts exertion and exhilaration.

Back on the boat I did my best to relay to the others what I had just experienced. Despite apparently talking “a mile a minute”, I struggled to find the right words, but they were probably unnecessary anyway. Certainly everyone who had been in the water with the animals that day had experienced many of the same feelings, and I am sure they were writ large on my face (in big black and white spotted letters!). In swimming with this one particular animal, I experienced a profound connection with a truly spectacular natural phenomenon, one that will provide ample motivation to continue the search for a better understanding of the nature of such things, for long into the future.  These are the moments that launch and tie together a career in biology, and that was the best one I have ever had.

Could it be? The END?

CNN is reporting that the new device put on the wellhead of the BP oil rig Deepwater Horizon appears to have stopped the leak and is holding under the pressure, at least for now.  Lets all cross fingers that this marks the end of major leaking into the Gulf of Mexico.

Fieldwork here we come!

Things will probably get a little irregular around here over the next couple of weeks.  I'm part of a group of Aquarium folks leaving for Mexico tomorrow to participate in the Whale Shark Festival on Isla Mujeres, just near Cancun, followed by some intensive field work with colleague Rafael de la Parra, who you may remember from previous posts.  We'll be tagging animals, photographing their spot patterns for the ECOCEAN project (their spots are like fingerprints!), collecting plankton samples and sampling the chemistry of the water to look for differences where they are feeding and where they are not.  I'll try to post some stuff as we go along, even if its only a picture or a video here and there (there wont be much time for writing, unless the weather closes us out)

All of this is part of our partnership called Project Domino, which aims to understand and protect whale sharks in Mexican waters.  Its bigger than that, however, because many of those same animals travel from the Yucatan to the Caribbean, the West Atlantic and the Gulf of Mexico; sharks dont pay attention to sovereign borders.  Obviously concerns are running high for any animals that travel into the GoM, due to the Deepwater Horizon disaster.  Keep your fingers crossed that those animals avoid the affected area and that this latest attempt to cap the wellhead is successful.

Whale shark news roundup

Photo: Bruce Carlson/Marj Awai

There’s a heck of a lot going on in the world of whale sharks right now, so I thought a news roundup was in order.

Blogger GrrlScientist has a nice blog post up about whale sharks right now, over at Scientist Interrupted

Sad news about a whale shark that was trapped in fishing nets in Pakistan and died. I have no idea what the scientist is talking about when he describes them as “inefficient swimmers”; as far as we know they are paragons of efficiency. I also have my suspicions about whether this animal was actually dead when it was brought back to shore. In a different story about the same event, it described the animal as being alive when the fisherman found it, tail-looped it and dragged it back to the beach, and how its illegal to fish for them, but legal to use them as you like if they die accidentally, hmmm....  Without witnesses, I guess we'll never know.

Our collaborator Bob Hueter from the Shark Research Lab at Mote Marine Laboratory is following an animal dubbed Sara in the Gulf of Mexico, who has been affixed with a real-time satellite tag. So far she is avoiding the worst affected area of the BP oil spill, which is a relief. Follow her movements here.

Unfortunately, other whale sharks don’t appear to be avoiding the pollution. NOAA scientists last week observed whale sharks among ribbons of surface oil, not 4 miles from the Deepwater Horizon wellhead. If whale sharks are unable to avoid the oil, it’s a potential disaster because the anatomy of their gills and filter-feeding apparatus are superbly susceptible to fouling, as I discussed in a recent blog post.

One of my projects is getting a bit of press this week. Georgia Aquarium has entered into a collaboration with the Core Sequencing Facility at Emory University to start sequencing the genome of the whale shark. It’s a huge job, but the lab at Emory, led by Dr. Tim Read, are up to the task! They’re using Roche 454 pyrosequencers to generate a survey sequence right now, from DNA we isolated in the lab at the aquarium. Its exciting stuff and was picked up on the AP wire. Read an example here, or just google “whale shark genome emory”

University of Southern Mississippi research Eric Hoffmayer was lucky enough to observe an aggregation of about 100 whale sharks off the coast of Louisiana last week, accompanied by legendary marine explorer and Nat Geo guru Sylvia Earle.  Eric has been working with that population for some time, but as far as I know thats the most he's ever seen in one place.  Lets hope they are animals avoiding the oil spill.

And, finally, the 3rd annual Whale Shark Festival is scheduled to get underway in Isla Mujeres, Mexico, next Friday the 16th.  I'll be there with other scientists including Bob Hueter and Rafael de la Parra, talking publically about whale sharks in the Gulf and the other amazing marine biology of the Yucatan.  There's also going to be a film festival and cultural activities highlighting Quintana Roo.  Did you know that "shark" is one of the only English words with a Yucatec Indian origin?  Its comes from the Mayan "Xoc".  Hope you can join us!

Implications of the first sighting of whale sharks in the gulf oil slick

I recently experienced a moment of genuine dread regarding the oil spill in the Gulf of Mexico, and it was neither a familiar nor comfortable feeling. What is it that invoked such a powerful feeling after a disaster that has been underway for the last 80-odd days, now? Something that struck a little close to home, of course: the first direct impact to whale sharks. You may have seen this story coming across the wires over the past two days about NOAA scientists who, while on an aerial survey of the impacted area, observed 3 whale sharks swimming among ribbons of surface oil, not 4 miles from the epicenter of the Deepwater Horizon spill. This observation has serious implications; let me explain.

Whale sharks are widely-ranging tropical migratory sharks that are unusual among their more toothy relatives in that they eat plankton. Two of the adaptations they use to pursue this lifestyle – surface filter feeding and an exquisite sense of smell – make them especially susceptible to the impacts of the oil spill. I had all but convinced myself (perhaps wishfully thinking) that whale sharks would be able to sense the altered chemistry of the affected water bodies and avoid the area. It now seems that this is not the case; the observation by the NOAA scientists suggest that either whale sharks cannot tell the difference between polluted and unpolluted water, or they can tell the difference but do not alter their behaviour in such a way as to avoid the ribbons and plumes. As USM researcher Eric Hoffmayer states in the article, this is the realization of the worst fears of whale shark scientists, and I count myself among those.

How can it be that whale sharks are unable to tell the difference if their sense of smell is so good? One simple explanation is that the olfactory abilities may be extremely selective. Scientists don’t know exactly what sort of chemicals whale sharks are homing in on when they seek out patches of food in the ocean – indeed, addressing this question is one of the goals of this year’s whale shark research program at Georgia Aquarium – but we have some good candidate molecules. If the whale shark sense of smell is highly tuned to these compounds and relatively insensitive to other families of chemicals, like hydrocarbons (oil and gas), then it’s certainly possible that whale sharks simply cannot detect the problem.

That’s when the second adaptation, surface filter feeding, becomes a liability for whale sharks trying to negotiate the deadly emulsions and surface slicks in the Gulf. To fully appreciate why this is such a problem, we need to look a little more closely at the filtration apparatus whale sharks use to feed.

Like most plankton-feeding fishes, whale sharks use filters in the mouth/gill cavity to sift food particles from the water (see the exellent illustration by Emily Damstra at right). And like most plankton-feeding fishes, these filters develop from structures associated with the gills and gill rakers (cartilaginous rods that come off the leading edge of the gills and protect the gills from fouling and shape the current of water across the breathing surface). Where whale sharks differ radically from other planktivores like, say, anchovies, is that they do not have feathery interlocking gill rakers that serve to filter the plankton but can be disengaged from each other to allow bulk water flow out through the gill opening. Rather, their filters are so derived and so heavily branched that they form a single continuous pad that occupies the space between gill arches; it looks a lot like a black scouring pad. The gill arches cannot be disengaged from each other; thus, anything that goes in the mouth must be small enough to pass through the filters (less than 2mm, or about 1/12th of an inch), or it must be swallowed, or be spat back out through the mouth (something they are surprisingly good at!). In a paper currently in the review process, comparative anatomist Phil Motta from USF is describing the full functional anatomy of these structures; he took the photo of the filter pad surface shown hereabouts based on material samples from Georgia Aquarium.

The implication here is that oil that finds its way into the mouth, if it is not to be swallowed or to foul the filters, must be continually spat back. OK, I hear you say, perhaps if the whale sharks avoid feeding, there won’t be a problem. If only it were that easy. Whale sharks do not only use their mouths for feeding, they use them for breathing. They need to be passing water continually across the filters and thence across the gills, in order to keep the body supplied with oxygen. For the whale shark swimming in oil-affected waters, therefore, the animal’s breathing needs and the susceptibility of their feeding filters to fouling are in complete opposition.

If whale sharks are swimming into oil-polluted waters and fouling their filters with oil, what does that mean? In my best estimation, it means that the oil spill represents an extremely serious threat to whale shark health. I am by no means the first person to suggest this. Nature identified whale sharks as one of the 5 species most likely to be affected by the oil spill, and other scientists like Bob Hueter from Mote Marine Laboratory have also highlighted the risks. The true toll that the spill exacts on the Gulf of Mexico whale shark population will not be known for some time, but the thought of dead or dying whale sharks sinking silently into the depths (dead sharks generally sink, not float) is yet more motivation to put an end to the spill and to undertake immediate and extensive research and conservation programs to assess the damage and plan a road to recovery for the whale sharks – and all the other affected wildlife – in the Gulf of Mexico.

Two videos from our recent Mexico sojourn

Below are two short videos showing some of what we got up to on a recent lightning fast trip to Mexico, footage that our AV folks spliced together from a FLIP camera I took along.  We had heard word of whale sharks gathering at one of our research sites, so I threw together a quick trip and Jeff Reid, the Aquarium's DSO, and I went down to scope it out.  It wasn't hard science this time; mostly a reconnaissance boat survey and an aerial survey, and getting to grips with the logistics for the big trips that will happen later this summer (more about those in future posts).  But at least they give a sense of what its like down there.  Next time I will try to hold the camera a bit more steady, but in the meantime - enjoy.

When acute gives way to chronic, Deep concerns for the Gulf set in

Just five days before the Deepwater Horizon oil rig exploded in the Gulf of Mexico, I wrote a piece for this blog about a different oil spill in Australia, when a Chinese coal ship called the Shen Neng1 ran aground in Queensland and spilled thousands of gallons of fuel oil onto a section of the Great Barrier Reef.  The gist of that post was that, horrible though they may be, there's no great cause to worry about acute events like that, because many marine ecosystems show remarkable resilience in the face of singular disturbance events.  About a week later when the BP spill started, therefore, I had confidence that the well would swiftly be capped, the oil would dissipate, Gulf life would return to normal and folks would all move onto the next media-hyped panic-fest.  But, as the days have dragged into weeks and the weeks are now dragging into two months and counting, and as the estimates rise of the amount of oil that continues to leak, and as successive attempts to cap the thing have failed, that confidence that the Gulf can recover to the same state it was in before the spill has started to get ever more shaky.

Now, I like to be a positive person; I try to see the upsides in most situations and not get caught up in negativity, which I consider one of the greatest and most utterly pointless malignancies of modern society.  But, following the coverage in the mainstream news and on excellent blogs such as DeepSeaNews and Observations of a Nerd and thinking about the problem in terms of ecological processes, it seems to me that we may well have passed a tipping point and that the ecosystems of the water column, benthic (bottom) habitat and coastal marshes may never return to their former states, even if they could stop the flow right now.  This principle has been elegantly captured by the "rolling ball" analogy, wherein an ecosystem has, by virtue of its structure and complexity, a sort of "potential energy" like a ball on a hill and that, if disturbed hard enough, you can start cascades that see the system diverge - the ball rolling down hill - until it settles in a new organisation - a dip in the hillside.  The important point is that getting the ball back up the hill to the former state is next to impossible, or at least requires inordinate amounts of energy and a thorough knowledge of the organising principles, which we lack.

What does all that mean for the Gulf, though? If a Spartina marsh isn't, then what is it?  What happens in the water column?  On the bottom?  That's where research comes in, and I was encouraged to read on the NSF website and by conversations I had with NSF and NOAA Fisheries Service program officers yesterday that they have spent all available money on rapid response grants, most recently an NSF multi-institutional cruise coordinated by UGA to study microbial responses in the water column.  Its not enough though, and the slowness of the peer review-based funding systems we have just can't meet the needs of a crisis of this magnitude fast enough, once the rapid response fund is tapped out.  It really needs executive intervention: if the White House can propose a Wall Street or Auto industry bail-out, why not a rapid response research and rehabilitation fund?  We can bill BP later!

Where is this all headed, and what should we expect to see in a "new" and different ecological regime in the Gulf of Mexico?  No-one can be certain at this point, but a hall-mark of such reorganisations is loss of diversity, and in any worldview, that is something to be lamented.  Lets hope it doesn't come to that, but at this point any concerns you may have that the damage to the gulf is irreparable could be forgiven, which is more than I can say for those responsible for this mess.

Testing, testing...

I'm posting this video I took of a whale shark in Mexico, to test the embedding of YouTube videos in Blogger posts.

The water is ALIVE!

Its easy to get discouraged about the plight of marine ecosystems and the future of all those incredible marine species that we love so much. This is especially so of late, with all the bad news about the oil spill in the northern Gulf of Mexico and the impacts that it may well have on several habitats. Consider this post, then, as your good news story for the week. I am here to tell you that there is still amazing stuff to see in the ocean. Incredible stuff. Stuff that will blow your mind. I can tell you this with supreme confidence, because for the last two days, that’s exactly what I have been seeing. As part of the research program at Georgia Aquarium, I am with colleagues in Quintana Roo, Mexico, studying whale sharks and other species that live in the azure waters of the Yucatan peninsula. Jeff Reid, who is the aquarium’s dive safety officer, is here and our main colleague in Mexico is Rafael de la Parra of Project Domino, who has been working on whale sharks and other marine species in the area for many years. This is a remarkable part of the world, with a lot of great terrestrial activities (can you say Cenotes, anyone? No? How about Mayan ruins?), exceeded only by the marine life, which is truly spectacular.

Yesterday Jeff and Raffa and I spent the day boating around the northeastern tip of the Yucatan along with videographer Jeronimo. Now, when you’re on a boat, you can only see a small strip of ocean either side of the vessel, and yet over the course of the day we saw lots of mobula (devil rays), turtles, flying fish, manta rays, spotted dolphins and whale sharks. We snorkeled alongside some of these animals and, in the case of whale sharks and mantas, took samples of their food for later analysis. They dine on the rich plankton soup of this tropical upwelling area, much of which consisted of fish eggs, which hints at other fish species – yet unseen – taking advantage of the plankton to start their next generation by spawning in the surface waters. Snorkeling next to a whale shark in the natural setting was a special thrill; I’ve been lucky enough to work with the animals in the collection at Georgia Aquarium since 2006, but this was my first encounter with them in the wild. Except for the slightly different “faces” (we do get to know our animals pretty well) and the parasitic copepods visible on the fins of the wild animal, it could have easily been the very same sharks Jeff and I have been working with in Atlanta.

Today, Jeff and Raffa and I joined Lilia (from the Mexican department of protected areas CONANP) and pilot Diego for an aerial survey of the waters around the northeastern tip of the Yucatan. In contrast to the boat, you can’t get in the water from a plane (its not advisable anyway), but you can see a whole lot more at once and cover a much greater area in a relatively shorter time. From the air, lots of sharks, cownosed rays, manta, dolphins, fish schools and whale sharks were all visible, and I am told that flamingos and manatees can be seen at other times too. The manta rays, which numbered in the hundreds, were especially impressive and included at least two species (see my post about taxonomy of mantas). The sheer number of cownosed rays, called chuchas in the local slang, was staggering (muchas chuchas, if you will). They formed huge schools that looked for all the world like the rafts of sargassum weed that accumulate on the wind-lines at the water’s surface offshore. Many of the turtles and mobula seemed to be in the mood for love; most turtles were in pairs (or a pair being followed by other hopeful males), whereas the mobula followed each other in lazy tandems, their wingtips breaking the surface with every stroke. Whale sharks were also there – lots of them – with their attendant flotilla of tourist boats and tiny orange specks of snorkelers in life-vests, doing their best (and largely failing) to keep up with the gentle giants.

When you have experiences such as those I have shared with my colleagues over the last two days, you are reminded why we do this stuff in the first place. Its not just for the papers, or the salary or the glory of new discovery (yeah, right!), its for those moments working with animals when you and a colleague become friends because you shared an experience of the oceans that most folks will never have. We should seek to share and recreate those moments with everyone we can, whether its in an aquarium or on the open ocean. I am pretty sure that if we could all do that, then public empathy for the plight of the oceans would skyrocket, and many of the threats that face them would be addressed quick smart.

Oill spills and Tar balls – know thine enemy

One of the more intriguing aspects of oil spills, including the DeepWater Horizon spill currently unfolding in the Gulf of Mexico (DeepSeaNews has covered it well), is the formation of tar balls.  These are globby blobs of bitumen-like material that are found on the sea floor or washed up on beaches after a spill. There's a few theories about how they form, but the general concept is that as the more volatile parts of the oil mixture evapourate, the mixture becomes thicker, heavier and stickier, until eventually the blob becomes heavier than seawater and sinks. On the bottom, the sticky blob incorporates sediment and its ball-like shape is reinforced by the rolling actions of currents or surf, in much the same way as you roll cookie dough into balls before putting them on the baking tray (mmmmmm….cookies….ahem). Sometimes this process makes for a grainy crust on the outside and a soft center, a bit like a Ferrero Rocher (mmmmm....chocolate....why do my analogies always involve food?).  There’s some other theories of formation that concern flocculation (oil sticking to clay) and emulsion (oil and water making a mousse of sorts - again with the food), but the prevailing idea seems to be that of smaller blobs of weathered oil coalescing and incorporating sediment. The net results is a gooey mess that is characteristically hard to remove if it sticks to you (or an animal), pongs of petroleum and is generally unpleasant.  The photo at left from NOAA's image library shows a tarball on a beach in California

Other than their B-grade horror movie nature (The Blob – aiieeeeee!) and the formation process above, I confess not knowing much about tar balls, so I went to the literature to see what’s out there. The answer: not much. A Web of Science search for “(tar ball) or tarball” 1945-2010 gets you precisely 26 hits. Now that is interesting! I would have thought that there would be far more, given the attention that is focused on oil spills when they happen. Much of the research has focused on chemical fingerprinting to identify where a given tar ball originated. In other words, the presence and absence of certain chemicals in a tar ball can tell you what sort of oil the ball formed from, and pretty accurately too. This has allowed some other studies that have shown that you have to be careful about blaming all the tar balls on a beach on one spill; there’s often a pretty good background level of tar balls from previous spills and even natural sources of oily substances. This is especially so for really small tar balls in the mm size range.

So what’s the long-term prognosis on tar balls in the environment? It doesn’t look like that question has been thoroughly answered yet.  Clearly they persist long after many more obvious signs of oil are gone.  Its tempting to think that they may be largely inert, especially those that form a good crust on the outside that reduces stickiness and prevents chemical interactions with the outside. But really, it seems like there’s a lot more work that needs to be done to understand these curious byproducts of oil spill accidents.

Post your eyewitness accounts of the Gulf oil spill here

I think we'd all love to hear from people who live on or near the gulf coast and may have observations or stories to tell about their experiences of the oil spill.