What is living at 4100 m depth on the seafloor of the Clarion Clipperton Zone? In previous posts, several organisms that are part of the macrofauna and megafauna have been described. But, are they the only ones living there?
Very surprising benthic foraminiferal animals live in the Clarion Clipperton Zone (CCZ). Usually when speaking about foraminifera, we think about very very small organisms (less than 300 µm). However, large foraminifera, more than 2 cm, inhabit this environment. Foraminifera are only one single cell, which makes them very remarkable. This unique cell is protected by a test (or a shell). The test can be made by the agglutination of particles found in the sediment (sediment grains, coccolithophores, diatoms, etc.). Other species make a calcareous or an organic test. The giant foraminifera of CCZ have a large variety of morphology and size: chains of small balls, small trees, domes, and some others have a leaf or fan shape. These foraminifera are living on the sediment or attached to a support.
Xenophyophores – giant Foraminifera
During the HyBis video dives, we were able to observe them in their natural environment. These foraminifera are, in fact, very abundant in the CCZ. We also collected some specimens with the megacorer or boxcorer. In fact, these organisms are not very well known: how can one single cell be more than 2 cm? How they live and how long? …. Trying to answer some of these questions, DNA analysis will be performed. This analysis could give some further ideas of what these organisms really are. Some other collected material will go to the Discovery Collections where they will be morphologically described.
Some get caught on traps, a few in cores, and others are small enough to be sucked into water bottles… For the biggest creatures however, we reserve the “rock star treatment”; we record HD videos and photos from their day to day life! Different angles, different postures, whilst they are eating, trying to hide, or even when they are looking for a mate… Our cameras could be flying above them at any time.
Lizardfish
Modern underwater technology allows for the generation of deep-sea fauna studies based on high resolution imagery transects. There’s basically 2 types of image recording devises: the ones we remotely operate from the ship using a high voltage cable, and those automated with a pre-planned mission (AUV). On board of the JC120 we have one of each; Hybis, and the Autosub6000. Thanks to the extraordinary work of the 2 teams of engineers managing these devises, so far, during this expedition we have been able to collect about 45 hours of video, and more than half a million pictures from the seafloor…!
Anemone
Despite for some this could sound like a “Big Brother” type of study, where nothing escapes from our sight, it is actually far from that. In fact, we still do know very little about the megafauna that lives in the deep sea, especially in the CCFZ area. It is a simple scale issue; only the CCFZ abyssal plain covers an area as wide as Europe, and with 100,000 pictures we do “only” cover a length of about 40km. However, the amount of information we obtain even from the shortest transects is huge. Like pieces of a puzzle, in almost every picture we analyse we get to discover something new. Frame by frame, our job from now on is to reveal the secrets of the largest creatures living in this mysterious environment.
The cruise is almost over after a few weeks devoted to exploring the deep-sea of the Clarion-Clipperton Zone looking for marine invertebrates. Some days ago we were watching a live video using HyBIS, our Towed Remotely-Operated Vehicle during the cruise, and I was mentally comparing these communities with the ones I am more used to, shallow-water communities from the Mediterranean and Southern Ocean. When compared to shallow-water communities, deep-sea communities are usually low-diversity and low-density either for megafauna (large organisms seen by the naked eye) as well as for macrofauna (generally microscopic). The latter have been actually our main focus for this cruise and the main reason why microscopes have been our ‘best friends’ on board. We collected these organisms mainly from two different substrates: one the one hand, from our beloved manganese nodules (mainly sessile fauna, being sponges the most represented group, besides, of course, the omnipresent forams…), which we biologists, always willing to give names to things, call epifauna (fauna living on top of a substrate); on the other hand, from our also esteemed sticky mud (mainly mobile fauna, being crustaceans and polychaete worms –the apple of my eye– the most common groups we found here), which we biologists again name after a particular word, infauna (fauna living inside a substrate, mud in this case).
Me with one of my ‘best friends’ on board: our microscope. Yes, I know, I need to have my hair cut… urgently. Uno de mis ‘mejores amigos’ a bordo (mi lupa binocular) y yo. Sí, ya lo sé, necesito un corte de pelo urgentemente (Pavo real, pavo real, viva la revolución…).
I have to admit that we, James and I, are both very happy with the results obtained so far. It has sometimes been a highly demanding work, with endless hours in the cold room (I could not get rid of the cold temperatures I was used to after working in Antarctica, even after moving to the Central Pacific) non-stop slicing and sieving mud, but I honestly believe the reward has been great. Not only because of the scientific outputs we expect to obtain after the future analysis of our samples. The extra reward we are taking with us is the huge help, involvement and friendship that our colleagues (including crew, of course) have generously given to us. Thank you guys! Without all of you it would not have been possible!
Some pictures below to illustrate a few examples of the fauna we have collected so far:
Sponge commonly found in association with manganese nodules (example of epifaunal organism). Esponja comúmente asociada a los nódulos de manganeso (ejemplo de organismo de la epifauna). Sergi Taboada & James Bell (NHM London)Polychaete worm inhabiting the mud (infaunal example). Notice the mud filling its guts from which it gets nutrition. Gusano poliqueto que habita el barro (ejemplo de organismo de la infauna). Fijaros en el detalle de sus intestinos llenos de barro del que obtiene su alimento. Sergi Taboada & James Bell (NHM London)Another polychaete worm inhabiting the mud (infaunal example). Otro gusano poliqueto que encontramos en el barro (ejemplo de organismo de la infauna). Sergi Taboada & James Bell (NHM London)Sipunculan worm inhabiting the mud (infaunal example). Gusano sipuncúlido que encontramos en el barro (ejemplo de organismo de la infauna). Sergi Taboada & James Bell (NHM London)
-Sergi Taboada, member of the Natural History Museum of London team
‘Macrofauneando’
La campaña llega a su fin. Han sido unas semanas intensas que hemos empleado en explorar y conocer mejor los invertebrados marinos que habitan las aguas profundas de la Clarion-Clipperton Zone. Hace tan solo unos días, mientras disfrutábamos de imágenes de vídeo en directo de las comunidades de estos fondos gracias al HyBIS, el Vehículo Remolcado Operado Remotamente que hemos utilizado durante la campaña, pensaba en lo diferente que son estas comunidades respecto a las que yo mejor conozco de aguas más someras del Mediterráneo y la Antártida. A diferencia de éstas últimas, las comunidades de aguas profundas que hemos estudiado en esta zona se caracterizan por tener una diversidad y densidad de organismos muy baja, tanto para los organismos pertenecientes a la megafauna (organismos grandes que se pueden observar a simple vista) así como para los organismos del grupo de la macrofauna (organismos que no se ven a simple vista). Estos últimos han sido nuestro principal objetivo durante la campaña y la principal razón por la que la lupa binocular ha sido nuestra ‘mejor amiga’ a bordo. Mayormente, hemos recolectado estos organismos de dos substratos diferentes: por un lado, de nuestro amados nódulos de manganeso (principalmente organismos sésiles, siendo, como no, las esponjas el grupo mejor representado, aparte claro está de los omnipresentes foraminíferos), a los que los biólogos, muy dados a poner nombrecitos a todo, llamamos epifauna (organismos que viven encima de un substrato); y por otro lado nuestro no menos estimado y querido barro pegajoso que nunca faltó a la cita (sobretodo fauna móvil, siendo los crustáceos y los gusanos poliquetos –la niña de mis ojos- los grupos más comunes que encontramos aquí), para los que de nuevo los biólogos tenemos un nombre, infauna (fauna que vive en el interior de un substrato, barro en este caso).
Tengo que reconocer que James y yo estamos muy contentos con los resultados de la campaña que hemos cosechado hasta ahora. Ha sido muchas veces un trabajo muy duro, incluyendo interminables horas en el laboratorio frío (ni siquiera en el Pacífico Centro me he podido quitar de encima el tener que trabajar a temperaturas bajas como en la Antártida) cortando y filtrando barro como si no hubiera un mañana, pero reconozco que la recompensa ha sido muy grande. Y no solo porque los resultados científicos que esperamos obtener son prometedores. La recompensa extra que nos llevamos es la enorme ayuda, el compromiso y la amistad que tan generosamente nos han prestado nuestros colegas (incluyendo aquí a la tripulación, por supuesto). ¡Millón de gracias, companys! ¡Sin vosotros no hubiera sido posible!
Arriba os dejo algunas fotos para ilustraros con ejemplos algunos de los organismos que hemos encontrado hasta ahora.
-Sergi Taboada, miembro del equipo del Museo de Historia Natural de Londres
Reading all these previous posts explaining fabulously what we are doing and how we manage to put mud everywhere on the ship, I thought, have we really explained why we are doing such a mission (apart from the pleasure of sieving buckets after buckets and holding cores in a cold room)? We try to evaluate the impact on the ecosystem of mining the seabed. But do we really have an idea of what the mining activity will look like in such an environment? To have a better idea of what mining nodules might produce, let’s get back to the fundamentals. Nodules constitute more or less spherical concretions of Fe and Mn oxides accumulating base metals like copper, nickel, cobalt and other strategic metals like tantalum, lithium, vanadium and the rare earth elements. These elements are strategic, even crucial for our advanced society as they get into the production of most of our wiring, batteries (lithium), touch screen technologies and renewable energies like magnets used in wind turbines. So nodules present economic concentrations up to 2 weight % cumulated base metals. Doesn’t seem much to you? Well imagine a bathtub full of nodules; this bathtub actually represents approximately 40 kg of these precious metals, interesting isn’t it? Now another important characteristic to consider in the exploitation of such ore is that nodules occur mostly at the water-sediment interface and thus constitute a two-dimensional deposit. So considering a lot of variables like the actual market price of metals, nodule density on the sea-floor and mining operational costs, it is estimated that the dredging of an area ranging from 50 to 85 km² per year is necessary to make the operation worth it. I know the Pacific is quite a big ocean, but how will such a fragile and poorly known ecosystem react to this activity? Well, this is the “why” behind the “what” of our mission there, along all the other discoveries we are doing here.
Sidescan sonar is an acoustic tool which allows us to image the surface of the seabed (a swath on either side of the instrument) by analysing the strength of the return signal. It’s the acoustic equivalent of a radar image: a hard seabed will provide a strong return while soft mud will have a much weaker return. If we get closer to the seabed (for example when using an AUV), a higher frequency signal can be used and this allows us to pick up smaller features on the seabed such as holes, rocky outcrops or other unknown objects …
When objects are above the seafloor, the side nearest the vehicle is imaged, but the far side remains in the shadows. This shade is sometimes more useful to provide an idea of the actual profile and help identify what the object might actually be. If you have any ideas for the following images, let us know.
Strange shapes found in high resolution sidescan images of the seabed. Altitude 3m, scale bars representing 10m, high backscatter in light brown and low backscatter in black.
We’re well over half-way on this cruise by now, and the scientific operations are in full swing. Numerous cores full of mud have come on deck, we’ve sampled the water column, towed the HyBIS vehicle over the seabed and sent the Autosub on its data-gathering missions. But how do we actually know where our samples come from, or where to send the deep-water vehicles to? This is where the technique of seafloor mapping comes in.
As it is impossible to look through 4000 m of seawater, we make use of sound to detect the water depth, seafloor topography and seafloor hardness. We have a range of echosounders available to us that we use for different tasks. There is the shipboard multibeam echosounder, which measures depth in a strip across the ship’s track. So as we move forward, we gradually create a map, strip by strip (see below). The intensity of the echo gives us an idea of the hardness of the seabed (rock vs. mud, for example).
A similar system, but then of smaller size, is also mounted on the AUV. Getting closer to the seabed with Autosub means we can make maps of finer resolution (similar to moving closer to an object when taking a picture allows you to get more detail). Autosub cannot cover the same amount of ground as the ship, though, so we use it to get fine details of specific areas of the seabed that are of particular interest, and then we ‘nest’ these fine-scale maps within the more broadscale maps made by the ship.
Creating these seabed maps instantaneously provides the scientific community (here on board, but also beyond) with some of the necessary information to develop new insights about seafloor formation and evolution processes, and about the distribution of benthic life. It also gives us a real feeling of exploration, picturing parts of the ocean floor that have never been mapped before!
The tropical Pacific is one of the least productive areas of any ocean. Sedimentation rate to the seafloor 4km below us is barely measurable, in the order of a few millimetres per 1000 years (influenced a bit by topography). Our trawl, and a few hours of video have revealed lots of shark teeth on or in the mud on the seafloor. This might be unremarkable, after all sharks lose their teeth all the time…but many of these teeth are huge…
Megalodon tooth
These huge teeth are between 3 and 16 million years old, and yet they are just sitting there, on the seafloor as though they’d dropped yesterday. This really illustrates how low the supply of sediment is to the seafloor and how difficult it must be to make a living for the animals that we’re finding.
These teeth come from a species of shark called Carcharodon megalodon. It was similar to the well-known Great White Shark of today (Carcharodon carcharius) but could grow to around 18m long, ate whales and could weigh as much as 50 tons. Since sharks have a skeleton mostly made of cartilage, fossils of other bones are quite rare so it’s difficult to know exactly how big Megalodon might have been. Taking information from modern sharks, it’s estimated that a Megalodon would have had 250 – 300 teeth in a mouth 2 metres wide!
Well, after all of these interesting posts about marine biology, I think it is time for the geochemistry team to show up a little bit of our work!
We know that nodules form in the surface of the sediment, which is the reason why we take surface sediment and column water samples from megacore, boxcore or CTD . However, this is not all: nodules also get buried, and then the geochemical processes occurring below the sediment surface influence them too, modifying their final composition! These processes are what we call diagenesis, and are mostly influenced by the porewater chemistry.
In this context, one of the most useful tools to get to the bottom (literally) of it is the collection of samples from the gravity core. In this way, we can obtain deeper sediment and porewater samples from the sediment layer (our cores are 3m long, at full recovery). The advantage of the collection of these samples with respect to those that we extract from the megacores will be that they will be less likely influenced by overlying water column processes, and thus will give us that essential information that we need about deep-sediment chemical processes.
The gravity corer on its way to the seabed
The process of recovery needs the active collaboration of all the members of the team. Once the 3-meter core is on deck, we let it to lie down horizontally and progressively split it into 50 cm sections, starting from the bottom, so it is easier to manipulate. During this process we measure, label and describe each section, and rapidly store them into the cold room (+4°C). Once there, they will need to rest for approximately 10 hours in order to homogenise their temperatures and measure their oxygen content.
A recovered core tube
After this, we will drill holes throughout each section, place them into the nitrogen-filled glovebox and extract pore water using rhizones and syringes(quite a funny process after you get used to it). This porewater will be divided, stored in different ways and later analysed for alkalinity, metals, anions, nutrients and organic and incorganic carbon content. After this, we drill larger holes and extract what we call a solid phase subsample: a small bit of the sediment. We will measure pH and then freeze them to study on land in different ways (porosity, organic matter content, metals…). Finally, the core sections will be vacuum-sealed in plastic sealed, and stored in the cold room.
The information extracted from these samples will be used together with that from the surface in order to elaborate a more complete overview of the geochemical history of nodule formation.
The Deep Ocean has always attracted me with its mysteries and treasures hidden in the eternal darkness. And now we are in the “Fort Knox” of the Pacific Ocean! It is a vast area confined between two transform faults called Clarion and Clipperton. But jewels here are not kept in a safe, they are scattered on the ocean-floor. I am talking about ferro-manganese nodules. The value of these dark spheres, with a diameter of just several centimeters, is related to a high content of ore elements.
The James Cook cruise brought together biologists and geochemists looking for living and mineral riches of the Clarion-Clipperton fracture zone. With every Hybis photographic dive each of us is expecting different miracles: biologists – oasis of micro- and macro fauna; geochemists – oasis of big (even huge!) nodules.
Yesterday the Ocean gave us an amazing gift – a trawl full of samples! Of course, it would be impossible without help of our professional engineers, technicians, crew and new bathymetry data. And now, when the catch is in the Deck Lab, you can clearly identify who is who! If you see people passionately looking for a shark tooth (Megalodon?), shrimps and sponges than you have a deal with life scientists. If you see someone carefully observing each nodule, choosing perfect forms, shapes and structure, than you have found me. What is a main interest for me as an organic geochemist? I am keen to find answer the questions: Where does the organic matter come from? What are the actual roles of organic matter in the formation, mobilisation or accumulation elements in the obtained Fe-Mn nodules? Organic compounds can react with metals through a variety of redox and other processes, and may influence physicochemical properties important to mineralisation (e.g., pH; mineral solubilities, precipitation temperatures, rock porosity).
Half of the cruise is left, and I feel that many more discoveries are yet to come!
One of the goals of RRS James Cook cruise 120 is to sample and describe the communities of animals living on the seafloor of this seabed mining reserve area. There are several ways you can approach this for deep-sea biology: to sample large animals living on the sea surface (called megafauna) we use photographic techniques and trawls. When it comes to the animals that are too fragile for trawling, too small to see in videos, or live beneath the sediment surface, we take samples of sediment and sieve them until we are left with the animals.
A small white hexactinellid sponge, living on the surface of a nodule
We hope to understand how animal communities connect with other areas by taking samples for DNA analyses. Two important things to know about a reserve area are; a) are animals that live in threatened areas also found in the reserve area? and b) how well linked are the communities in each area? By sequencing DNA samples from this cruise and others from areas that will be mined, we hope to understand how closely linked the communities are and help assess how effective the reserve area is likely to be at preserving the biodiversity of the area as a whole.
An amphipod (Crustacea: Peracarida, possibly Eurythenes sp.) we found in our amphipod trap
To get the very best DNA samples, we have to act quickly. As soon as the cores of sediment are on the deck, we bundle them into the cold room and sieve them in cold seawater. We have to chill seawater especially for this since the surface temperature here is around 27˚C and quickly destroys animals that are used to 2˚C. Once we’ve sieved them, we can leave them in a fridge for a little while until we’re ready to take some mug shots, some of which are featured here (taken by me and Sergio Taboada). The best preservative for DNA is ethanol, but unfortunately this isn’t so great for preserving the animals shape and appearance, particularly colour. To get round this preservation effect, we take photos of the animals under a microscope before they get dropped in the alcohol. Formalin is a much better preservative for animals but it destroys DNA so that’s no good.
Another kind of peracarid crustacean (called a Tanaid), this time from a sediment core
Combining the photos and DNA analyses is also incredibly useful for making a species catalogue of the area that can then be used to help other scientists working in other areas of this vast, and largely unexplored, part of the world.
RRS James Cook 120 Blog 