From the darkness emerges a boot. An old leather, steel-toed, work boot. It shouldn’t be there resting on the seafloor nearly two kilometers deep. I’m speachless. Even knowin this was going to be one of the toughest dives of my career, I’m still not prepared.

Seven years prior in 2010, Marla Valentine and Mark Benfield were the first scientist to visit the deep-sea floor after the Deepwater Horizon accident. On 20 April 2010, and continuing for 87 days, approximately 4 million barrels spilled from the Macondo Wellhead making it the largest accidental marine oil spill in history. Just months after the oil spill, Valentine and Benfield conducted video observations with a remotely operated vehicle (ROV) of the deep-sea impact. Overall, they found a deep-sea floor ravaged by the spill. Much of the diversity was lost and the seafloor littered with the carcasses of pyrosomes, salps, sea cucumbers, sea pens, and glass sponges.

Researchers continued to find severe impacts on deep-sea life. The numerical declines were staggering within the first few months; forams (↓80–93%), copepods (↓64%), meiofauna (↓38%), macrofauna (↓54%) and megafauna (↓40%). One year later, the impacts on diversity were still evident and correlated with increases in total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAH), and barium in deep-sea sediments. In 2014, PAH was still 15.5 and TPH 11.4 times higher in the impact zone versus the non-impact zone, and the impact zones still exhibited depressed diversity. Continued research on corals found the majority of colonies still had not recovered by 2017. However, studies examining the impacts of the DWH oil spill on most deep-sea life ended in 2014.

This gap in knowledge on the lingering impacts of one of the largest oil spills of all time is why I sit here in this cold, dark, ROV control room staring at a work boot in the abyss. A year prior, I had reached out to Mark Benfield about replicating his ROV methods and locations. I am here seven years after his study beginning to replicate his first video transect.

Within minutes of reaching the seafloor with the ROV, every scientist on the vessel staring at monitors showing live video from remote seafloor knew something was wrong. As Mark Benfield, Clif Nunnally, and I report in a new open-access article, the deep sea was not recovering at the impact site.  The seafloor was unrecognizable from the healthy habitats in the deep Gulf of Mexico, marred by wreckage, physical upheaval and sediments covered in black, oily marine snow.

Near the wreckage and wellhead, many of the animals characteristic of other areas of the deep Gulf of Mexico, including sea cucumbers, Giant Isopods, glass sponges, and whip corals, were absent.  What we observed was a homogenous wasteland, in great contrast to the rich heterogeneity of life seen in a healthy deep sea.

Conspicuously absent were the sessile animals that typically cling to any type of hard structure in an otherwise soft, muddy habitat.  Hard substrate in the deep sea is a valuable commodity but at the Deepwater Horizon site metal and other hard substrates were devoid of typically deep-sea colonizers.

The seafloor at impact site was characterized by high numbers of shrimps and crabs.  Crabs showed clearly visible physical abnormalities and sluggish behavior compared to the healthy crabs we had observed elsewhere.  We believe these crustaceans are drawn to the site because degrading hydrocarbons serve as luring sexual hormone mimics. Once these crustaceans reach the site they may become too unhealthy to leave much like those prehistoric mammals and the Le Brea tarpits.

The ROV dive began with a boot belonging to one of the workers on the Deepwater Horizon rig. The dive ended at the wellhead, now capped with a memorial to those workers who lost their lives. A dive bookended with reminders of the human tragedy of the oil spill. The narrative that unfolded between these was an environmental catastrophe. In an ecosystem that measures longevity in centuries and millennia the impact of 4 million barrels of oil continues to constitutes a crisis of epic proportions.

Valentine, Marla M., and Mark C. Benfield. “Characterization of epibenthic and demersal megafauna at Mississippi Canyon 252 shortly after the Deepwater Horizon Oil Spill.” Marine Pollution Bulletin 77.1-2 (2013): 196-209.

McClain, Craig R., Clifton Nunnally, and Mark C. Benfield. “Persistent and substantial impacts of the Deepwater Horizon oil spill on deep-sea megafauna.” Royal Society Open Science 6.8 (2019): 191164.

The post The lingering and extreme impacts of the Deepwater Horizon oil spill on the deep sea first appeared on Deep Sea News.

These bada$$ carbons are “isotopes”, sort of like fraternal twins (or triplets/quadruplets) where one is blazing their own path.  One of the twins is your regular Joe Shmoe who follows the rules and does everything by the book.  These are the ones shown in the periodic table.  The other twin in each set has the same number of protons as its boring twin, but it doesn’t follow the rules about how many neutrons they are supposed to have. They’re greedy little thieves. So, they are technically the same element, but they end up weighing different.  For instance, Carbon-13 has his regular six protons like its brother, but it has a whopping seven neutrons because it just haaaad to go and be extra cool. 

Almost every element has some number of isotopes/twins, except weird ones like Thulium and Holmium – but who even are those guys? Now, the wrong-number-of-neutrons outlaw twin can either be “stable” or “unstable”.  It’s like the difference between the cool guy in class and the guy who is so “cool” that he ends up expelled from school.  The stable ones are functional in society – in this case meaning they occur in nature without a problem.  The unstable ones are completely dysfunctional and over time try to turn back into their more stable twins by shedding neutrons.  It’s kind of like they just went too neutron-crazy, got a little wild, and now they’re all bloated and not having a good time. 

Knowing about these different carbons is important because stable isotopes can help reveal food webs.  Naturally occurring carbon consists of both the normal carbon and its bad boy twin.  We have a method that allows us to measure the ratio between the outlaw and the normal (we call this ratio the isotopic ratio). By measuring the carbon isotopic ratio of an animal, we can answer questions like what did this animal eat, what level consumer are they, and even what kind of eater are they (suspension feeder, predator, etc). This is especially important in my work because I want to understand how carbon from land makes it into the deep-sea food web. When I drop a big hunk of land carbon in the form of an alligator or a wood log (wood fall), I first measure the ratio of good boy to bad boy carbon in that particular hunk of food.  I also collect samples of the sediments around where I drop the food and measure the ratio of carbons in that sample too.  Then, after letting the food stay on the bottom of the ocean for a while, I can take animals directly off of it and take similar animals far away from the it.  When I measure the ratio of carbons in these animals, I can compare them to the ratio of the two food sources I measured and can understand which food source the animals are using.

The reason this all works is because of the saying “you are what you eat.”  Turns out that is actually true!  We know how much the good boy to bad boy carbon ratio should change from a food item to its consumer. This is especially helpful as we begin moving up the food web, because we can start to see who is eating whom – and this is something not yet well understood in the deep sea.

The post You are what you eat! Using bad boy carbons to understand food webs first appeared on Deep Sea News.

Leaving alone on the seafloor is the lonely painted frogfish, Antennarius pictus. Males and females only come together for the dirty deed but quickly become intolerant of each other.  If the female stays too close, the male will eat the female…which in the whole evolutionary passing the genes to the next generation scenario seems like an idiotic move.  Besides this minimal contact, that could end in eating mate, the painted frogfish prefers the lonely life.

The painted frogfish goest through ridiculous lengths to be avoided by other.  Individuals can extent extend and retract individual parts of their globular body.  The skin itself is covered with warty protuberances and lots of little eye spots that look like the holes, ostia, in sponges.  Over weeks, a frogfish can also change the color and pattern of it skin.  A part of its camouflage regiment the fish will also allow algae to grow on it.  All this to look like a lump of sponge on the seafloor.

Despite this derpy-sponge like appearance, the frogfish is actually a master predator.  When an unsuspecting prey swims close, because who in the hell can see the painted frogfish, the frogfish will flick a lure.  The lure, which occurs at the end of the elongated first dorsal spine, is even modified to look like a tiny fish.

The post These are a few of my favorite species: Painted Frogfish first appeared on Deep Sea News.

The preliminary results go something like the picture above. To be clear, it is important to do controlled, well-designed experiments to understand how trawling affects benthic communities and to disentangle confounding factors. I think this is what the Nature Conservancy and its collaborators are doing. But, it is also important to emphasize the preliminary nature of the study. You see, this study is underway and has not been published nor subjected to peer review for that matter. Readers have no way to evaluate the study design, methodology or interpretation of the data. The only materials and methods, and results, are found in the short New Scientist article:

“The team wanted to know how often trawlers can rake over a section of muddy sea floor before habitats can no longer recover. Records held by the National Marine Fisheries Service show parts of the continental shelf can be trawled between zero and 10 times a year. So last year, to mimic low-intensity trawling, four plots were hit twice. This October, they were each trawled five times, mimicking a high-intensity trawl. The Beagle took pictures immediately after each event, as well as six and 12 months after the first trawl.

Early signs indicate that marine life survived, even thrived, after last year’s trawls. Since then, the Beagle has spotted sharks, flatfish and thick schools of squid that dove, kamikaze-style, into its red laser lights. Donna Kline, a fish ecologist at California State University in Monterey Bay, thinks that far from destroying a habitat, the trawl may have created a new one by etching grooves into the flat bottom.”

Extrapolation

When results are given out to the media that have not undergone peer review, there is an ever-increasing chance that they will be taken out of context. Of course, this happens all the time to published, peer-reviewed results. The situation is made worse though when the community cannot take into account a wide variety of what the public might think are mere details, but the philosophical underpinnings of which are greatly important to accepting any data that come out the experiment. One site, a business blog at stuff.co.nz, immediately latched onto the findings from the New Scientist article with the provocative headline: “Bottom Trawling Is Good”. While unfounded and having a high probability of being flat out wrong, it makes for a good discussion point.

The study in question examines one bay in California, that was previously trawled, but not in the last 10 years. Do the results extrapolate out to a generality of muddy deep-sea bottoms? The mounting evidence from a variety of areas around the world say no (see Google Scholar for over 21,000 references to “Bottom trawling effects”), but this study is supposed to be controlled, whereas previous studies were not designed to specifically test how trawling affects seafloor communities. In other words, the data that exists right now is circumstantial, but very well done given the circumstances. Trawled areas are compared to non-trawled areas and diversity and community metrics are calculated. This type of science is common, and valid, but remains as documentation of patterns, not necessarily as an explicit, controlled test of a hypothesis. Again, to reiterate we do not know anything about the study and it is only half-way its 5 year duration.

Not a Fairy Tale Ending

What the press will do with a story like this is run away with it because creates tension, challenges previously held ideas, and has the ironic backing of a conservation organization. There are lots of details annoyingly missing from the New Scientist article. They hint that Nature Conservancy is seeking to create a sustainable fisheries model using this research. Well, it would sure be nice to hear more about that and might give context to the OMG TEH TRAWLING IS AWSUM!!1! LULZ!!! claim. They saw that “marine life survived, even thrived”, there is more to the deep-sea than fish and sharks. I have a hard time seeing how precious, long-lived corals and sponges – 2 extensive habitat-forming species – can survive a trawl by definition. While trawling creates a new habitat, i.e. a wasteland, this doesn’t mean habitat heterogeneity will result in more species. One species’ new niche was another’s previously optimal habitat.

What this story does affirm is that extraordinary, and contradictory, claims require great evidence. Published a study midway with inconclusive results in the popular press is irresponsible on the part of the researchers and may end up hurting their causes. Stakeholders may accept these results at current value and choose to let these preliminary findings guide their decisions about trawling. Fishing lobbies may latch onto the Trawling Is Good mantra and make things even worse for the industry for those juicy, seductive short-term gains.

Furthermore, it diminishes the intelligence of the readership. People aren’t stupid. Its one thing I’ve learned interacting with non-scientists (usually at the pub) is that common sense is still alive and well in the general population. Just read the comments to the business blog’s piece. The audience struck back furiously and quickly. Its great to challenge our mores in science, we are all trained as skeptics, but it requires a certain depth and evidence to be successful. Like any good fairy tale, there is a lesson to be learned, irresponsible reporting only goes as far as you can toss a 5000 year old piece of rare deep-sea coral.

The post From the Editor’s Desk: Benefits of Bottom Trawling and Other Assorted Fairy Tales first appeared on Deep Sea News.

Enter the sieve. It is a marine biologists best friend, saving hours of sorting and enabling quantification of fauna. In fact you can get these miracle  workers at McMaster-Carr for a mere $40-50. You take good care of these puppies and they will last several graduate student’s lifetimes! I prefer the 500 micron mesh size myself, but usually on top of the 64. You see, those damn limpets (Scheißeschnecke!!) always foul things up. I mean, there are ALOT of little limpets in vent ecosystems. Govenar et al. 2002 found up to nearly 100,000 of these bastards per square meter in tubeworm clumps at the Juan de Fuca Ridge. Sorting tens of thousands of limpets can be quite drearisome and on the occasion you find something that is to be classified as no a limpet is a moment of silent (or not so silent) joy. Stacking different size sieves has been a strategy that I have partaken in extensively in my career of bean counting.

The sieve size I use at the bottom though is the most important. It is my cut off. I am essentially saying I will ignore anything which exists that can fall through this size hole. Though I would ideally like to have this be as low as possible, usually around 64 micron – the cutoff size for meiofauna, I am often limited by what size my colleagues have used in past studies. This is important because my results need to be compared to theirs if I want to understand general patterns in species compositions and community structure. But a new study, building upon a slightly older one, reminds us that instead, interpretations might be limited by sieve size.

Gage and colleagues published an important methodological paper in 2002 describing the influence of sieve size on characterizing a deep sea community. The graph to the left is from their paper and clearly shows the biomass, numbers of individuals and numbers of species significantly increasing for 2 independent box-core samples. About 20 more species were recovered by winnowing down from 500 micron to 250 micron mesh. Twenty species is no laughing matter. That can mean the difference between a significant treatment effect or “meh, nothing here”.

In a recent paper published in Marine Biology Research, Pavithran and colleagues took it a step further and asked if it mattered what type of animal was being shaken down the gauntlet. Using a replicated transect of box-cores in the Indian Ocean they looked at the effect a 200 micron difference in mesh size (between 500 and 300 microns) had in characterizing 7 very different animal groups: nematodes, polychaete worms, tanaids, a type of copepods, isopods, bivalves and nemertines (a worm-like animal).

The authors found the greatest difference in biomass occurred with the polychaetes, up to 90% reduction using the 500 micron mesh, followed by 78% reduction of nematode biomass. But a reduction in biomass doesn’t necessarily translate to a reduction in species present on the larger mesh size. After all, it could be smaller individuals of one or two major species retained on the smaller mesh. Unfortunately in this case it did translate, quick significantly too. The smaller mesh retained 66 species, while the larger mesh only 40. Additionally, there were nearly twice as many individuals on the smaller mesh sieve. This actually translates to a loss of 43% of the species, just from simple methodology choices alone!

What does this mean for interpretation though? As I mentioned above, one of the important things in designing a study is make sure your work will be comparable to the work of others. But if other researchers have been missing a certain size fraction of the animal community, should you ignore it too? Meiobenthologists would respond sharply with a very vocal NO! In fact, they would argue that the majority of deep-sea studies are just plain wrong and misleading at best since traditionally, they have ignored a potentially important component of the deep-sea benthos. Some of the world’s best nutrient recyclers are in that under 200 micron size class. So perhaps interpretations are in general limited, especially if you want to make grandiose claims about general principles or ecosystem functioning. But the data gleaned is still important nonetheless. My concern is that there is likely a size class of deep sea animals between 64 and 250 microns that have remained undiscovered in the several decades of experimental deep-sea ecology because we didn’t sieve down enough! Potentially 40-50% of deep sea macrofauna could have been thrown overboard during the last 50 years!

Gage, J., Hughes, D., & Gonzalez Vecino, J. (2002). Sieve size influence in estimating biomass, abundance and diversity in samples of deep-sea macrobenthos Marine Ecology Progress Series, 225, 97-107 DOI: 10.3354/meps225097

Breea Govenar, Derk C. Bergquist, Istvan A. Urcyuo, James T. Eckner, & Charles R. Fisher (2002). Three Ridgeia piscesae assemblages from a single Juan de Fuca sulphide edifice: structurally different and functionally similar Cahiers Biologie Marine , 43, 247-252

Pavithran, S., Ingole, B., Nanajkar, M., & Goltekar, R. (2009). Importance of sieve size in deep-sea macrobenthic studies Marine Biology Research, 5 (4), 391-398 DOI: 10.1080/17451000802441285

The post (Sieve) Size Matters first appeared on Deep Sea News.

Send that data right over.  The absolute coolest gadget to hit deep-sea science is is the Benthic Rover, the deep-sea equivalent of the Spirit and Opportunity.  The Benthic Rover, the brain child of deep-sea biologist Ken Smith, and brought to life by engineers at the Monterey Bay Aquarium Research Institute, is approximately of small compact car.  The rover slowly creeps (3 feet per minute to minimize kicking up sediment) across the seafloor taking photographs of the animals and sediment in its path. Every three to five meters it stops and makes a series of measurements on the community respiration (i.e. oxygen consumption) of organisms living in the seafloor sediment. The rover is also totally tricked out with an optical sensor that can scan the seafloor to measure how much food has arrived recently from the surface water. Why? To try to understand of how deep-sea organisms acquire enough food to survive…a favorite question of mine as well. In the words of the press release

Most life in the deep sea feeds on particles of organic debris, known as marine snow, which drift slowly down from the sunlit surface layers of the ocean. But even after decades of research, marine biologists have not been able to figure out how the small amount of nutrition in marine snow can support the large numbers of organisms that live on and in seafloor sediment.

A series of foam packs make the 3,000 pound vehicle semi-bouyant at just 100 lbs in seawater, to prevent the rover from sinking in the soft oozy mud that dominates the abyssal plains. Tank-like treads keep the vehicle moving across the sediment and custom-made titanium pressure spheres house the computer and electronic needed to drive the vehicle.  Best yet the bad boy is programmable.  Here’s your mission, come back to me when you have some data!

However, during this summer the Benthic rover was tethered to newly created Monterey Accelerated Research System (MARS), an underwater observatory that provide power and data link to the vehicle. “Hooking up the Rover to the observatory opened up a whole new world of interactivity. Usually when we deploy the Rover, we have little or no communication with the vehicle. We drop it overboard, cross our fingers, and hope that it works.” In this case, however, the observatory connection allowed MBARI researchers to fine tune the Rover’s performance and view its data, videos, and still images in real time. Sherman recalls, “One weekend I was at home, with my laptop on the kitchen table, controlling the vehicle and watching the live video from 900 meters below the surface of Monterey Bay. It was amazing!”

An now for the rover in action!

The post Benthic Rover, Benthic Rover first appeared on Deep Sea News.

A new study in Nature Geoscience finds that domoic acid can make it to the deep.  Sediment traps set at 500m and 800m below the ocean surface off southern California. “The sinking particles contain over five times the United States federal limit of domoic acid.” The peaks coincided lagged only by a few days behind peaks in surface concentration implying that transport of domoic acids was immediate.  Previous work found that for both organisms in the continental shelf and throughout the water column domoic acid is pervasive.  This study suggests that domic acid concentrations in deep-sea organisms could also be considerable.

Add this to another way anthropogenic disturbance is reaching into the deep.

[googlemap lat=”34.1890858311724″ lng=”-120.003662109375″ width=”300px” height=”300px” zoom=”7″ type=”G_SATELLITE_MAP”]Santa Barbara Basin[/googlemap]

Sekula-Wood, E., Schnetzer, A., Benitez-Nelson, C., Anderson, C., Berelson, W., Brzezinski, M., Burns, J., Caron, D., Cetinic, I., Ferry, J., Fitzpatrick, E., Jones, B., Miller, P., Morton, S., Schaffner, R., Siegel, D., & Thunell, R. (2009). Rapid downward transport of the neurotoxin domoic acid in coastal waters Nature Geoscience DOI: 10.1038/ngeo472

The post Nerve Toxins In The Deep first appeared on Deep Sea News.