Faults, Vents, and Seeps Logbook
Leg 5, Day 4: Learning from the mud
March 29, 2012
What can you learn from a dead, single-celled organism buried in deep-sea mud? Almost everything!
Today we had two remotely operated vehicle (ROV) dives in the same general area as yesterday. We wanted to explore and sample farther along the fault so we can continue to verify the autonomous underwater vehicle (AUV) mapping data collected by our colleagues on the R/V Zephyr. We collected three largely different rock types that do not match across the fault. It is very difficult to determine rock types from the AUV’s very high-resolution bathymetric data. Therefore, it was critical to sample rocks and mud to determine how the material changes across the fault. Our findings today indeed helped us verify fault location and movement.
We have quite a few collaborators joining us on this leg of the expedition. Juan Carlos Herguera and Mary McGann are interested in organisms called foraminifera—"forams" for short. Forams are among the most common marine plankton species. They typically produce a shell made of calcium carbonate (CaCO3) and can range in size from tenths of a millimeter to a few centimeters. The two scientists are busy finding living forams in the push core samples, which Mary is classifying according to their morphology.
One of their goals is to characterize the species composition of these organisms that have adapted to the deep seafloor conditions in the Gulf of California. Here, forams have to balance the very high amount of food raining from the surface ocean and the very low oxygen concentrations at these depths. Juan Carlos and Mary will also send specimens out to a lab for DNA fingerprinting, so they can later use the DNA information to characterize foram communities in other oxygen minimum regions, and to understand how these organisms cope with these extreme conditions.
This is particularly interesting as the oxygen minimum zone has been observed to be expanding, consistent with ocean acidification. These population studies will provide us with a baseline to help determine whether forams are also expanding into shallower depths along with the oxygen minimum. To our knowledge, this would be the first DNA fingerprinting study on benthic forams in the Gulf of California or in the Northeast Pacific.
In addition to studying forams’ coping strategies in extreme conditions, Juan Carlos and Mary want to be able to use fossilized forams in the geologic record to reconstruct past environmental conditions. The Gulf of California is a large natural laboratory where diverse oceanographic and marine geological processes intersect. Geologic records can tell us about the ocean’s past experiments under different climate regimes.
One of the many interesting experiments occurs in the surface waters of the gulf. Seawater temperatures are highly variable in the northern part of the gulf on a seasonal basis, however, they vary little in the south. Due to this difference, which affects the way nutrients and chemicals are taken up by sediments and by forams, we would expect to see different communities from north to south which are adapted to these varying conditions.
Even more interesting, when forams are growing their shells out of calcium carbonate crystals—usually in a matter of days or weeks—they are using mostly the carbon dissolved in seawater along with tiny fractions of other metals dissolved in the seawater. Researchers have unraveled that more often than not these elements are absorbed into their shells in proportions that depend on the environmental conditions when they grew. This means that if we can measure their enrichments precisely, we can decipher how to read them in terms of temperature, salinity, nutrients, and oxygen concentrations at the time the forams were growing their shells. Since they are often preserved in the geological record, we have the fascinating opportunity to reconstruct those important variables for the past history of the ocean. Before we do that, we have to observe how accurate these foraminiferal sensors are in the present ocean. Later, we’ll talk more on what they tell us on the past.
—Susan von Thun, Juan Carlos Herguera, and Mary McGann
See below for a Spanish translation of today's log, courtesy of Juan Carlos Herguera
Diario de campaña, etapa 5:
¿Que podemos aprender de un organismo unicelular enterrado en el lodo del fondo del mar? Pues un montón!
Hoy seguimos en dos inmersiones al vehículo operado remotamente (VOR) básicamente en la misma área que estuvimos ayer. Queríamos explorar y muestrear a lo largo de la gran fractura de la que hablábamos ayer para continuar con la verificación de la cartografía realizada por nuestros colegas a bordo del barco R/V Zephyr. Colectamos tres diferentes tipos de rocas que no concordaban a través de la fractura. Es muy difícil determinar que tipos de rocas vamos a encontrar a partir de los datos de batimetría de alta resolución producidos por el Vehículo Autónomo Submarino (VAS, en inglés AUV), y por eso necesitamos ir a muestrear estas rocas y lodos para determinar como cambian estos materiales a lo largo de la fractura. Las muestras que tomamos hoy nos ayudaron a verificar no solo la localización de la fractura sino también su movimiento.
Tenemos con nosotros abordo a varios colaboradores en esta expedición que vamos a ir presentando a lo largo de la campaña. Mary McGann y Juan Carlos Herguera están interesados en unos organismos que conocemos cómo foraminíferos, que son una de las especies más comunes en el la superficie del océano como en el fondo del mar. Estos organismos producen típicamente un caparazón con carbonato de calcio (CaCO3), en otras palabras hacen su casita portable de ladrillos de calcita, cuyo tamaño puede variar entre unas decimas de 1 mm a unos pocos centímetros. Ambos están bien ocupados buscando foraminíferos vivos en los núcleos cortos que extraemos del fondo. Uno de sus objetivos es caracterizar la composición de las especies de este grupo de organismos que se han adaptado a las condiciones del fondo del Golfo de California donde viven en un fino balance entre la comida sobreabundante que les llega desde la superficie y las muy bajas concentraciones de oxígeno a estas profundidades entre 400 a 1500 m. Los foraminíferos bénticos que están recogiendo de los sedimentos los piensan enviar mas tarde a un laboratorio para obtener sus huellas digitales inscritas en su ADN. Esta información puede resultar de gran ayuda para caracterizar las comunidades de foraminíferos bénticos en regiones de bajas concentraciones de oxígeno para comprender como pueden sobrevivir estos organismos en estos ambientes hostiles para la vida de los organismos oxigénicos, prácticamente la mayoría de los que conocemos. Estas observaciones nos van a proporcionar con una línea base para determinar si estos foraminíferos bénticos, adaptados a estas bajas concentraciones de oxígeno disuelto en el agua, están expandiéndose a profundidades mas someras que nos permita cuantificar el avance de esta agua pobres en oxígeno hacia la superficie del océano. Fenómeno que se está empezando a discutir activamente entre oceanógrafos y que tiene profundas consecuencias sobre la ecología de los mares costeros y sus pesquerías. Por oro lado este sería el primer estudio que conocemos para conocer las huellas digitales del ADN en foraminíferos bénticos en el Golfo de California.
Los intereses de Mary y Juan Carlos en la ecología de los foraminíferos bénticos y pláncticos se extienden al registro geológico ya que quieren utilizar esta información para reconstruir las condiciones ambientales en el pasado que nos ayuden a entender los experimentos que el océano realizó bajo condiciones climáticas diferentes al actual.
El Golfo de California es un gran laboratorio natural donde se intersectan una gran diversidad de procesos oceanográficos y geológicos, que abarcan desde la atmósfera a la superficie del mar, el océano profundo, al piso oceánico a las calderas de roca fundida que lo alimentan. Uno de los muchos experimentos interesantes lo podemos observar en la superficie del mar a lo largo del Golfo de California en un transecto desde al alto Golfo hasta la boca es la variabilidad en las temperaturas superficiales del mar. Éstas son mas extremas en el alto Golfo y en la región de las grandes islas entre el invierno y el verano que en el bajo Golfo. Estas variaciones en las temperaturas son sintomáticas de diferentes procesos de enriquecimiento de nutrientes en la superficie, los que favorecen distintos tipos de comunidades de fito y zooplancton, el pasto marino y sus pastoreadores. Esta variedad esperaríamos verla reflejada en diferentes abundancias relativas de foraminíferos pláncticos.
Pero aún mas interesante es que durante el período que estos organismos están construyendo su caparazón a partir de cristales de carbonato de calcio, proceso que generalmente dura entre unos días a unas pocas semanas, estos organismos utilizan el carbono inorgánico disuelto en el agua junto con pequeñas cantidades de otros elementos disueltos en concentraciones muy bajas. Los trabajos de mucha gente han puesto en evidencia como las relaciones isotópicas de carbono y oxígeno de la calcita y la de estos elementos menores se encuentran en los cristales de calcita de sus caparazones en proporciones que dependen de las condiciones ambientales en las que construyeron estos organismos sus caparazones. Esto significa que si medimos muy precisamente estas relaciones isotópicas y las pequeñas concentraciones de metales podemos comenzar a descifrarlas como si fueran termómetros, salinómetros, sensores de oxígeno, o nutrientes de las condiciones pasadas del océano. Como estos caparazones se encuentran generalmente preservados en el registro geológico esto nos abre las puertas a la fascinante oportunidad de reconstruir estas importantes variables oceánicas para entender la historia de los océanos. Como con cualquier termómetro o sensor tenemos que conocer cuál es su precisión, por lo que campañas como esta son una gran oportunidad para poder llevar estos tipos de calibraciones a cabo. En otro momento hablaremos sobre lo que nos cuentan del pasado del océano.
R/V Western Flyer
The R/V Western Flyer is a small water-plane area twin hull (SWATH) oceanographic research vessel measuring 35.6 meters long and 16.2 meters wide. It was designed and constructed for MBARI to serve as the support vessel for ROV operations. Her missions include the Monterey Bay as well as extended cruises to Hawaii, Gulf of California and the Pacific Northwest.
ROV Doc Ricketts is MBARI's next generation ROV. The system breaks new ground in providing an integrated unmanned submersible research platform, with many powerful features providing efficient, reliable and precise sampling and data collection in a wide range of missions.
MBARI's heat-flow probe is mounted on the side of the ROV Doc Ricketts inside the vertical stainless steel box. This both protects the delicate probe and provide the track so that the probe can be inserted into the sediment along a totally straight path. The probe contains five high precision platinum sensors which are used to measure the vertical temperature gradient in the sediments. This gradient along with some knowledge of the heat capacity of the sediment allows scientists to calculate the rate of heat loss from the sediments into the ocean.In situ gas sampler
These are devices that are used to collect and sample gaseous gases bubbling out of seafloor vents. The way they work is by having small pressure vials (like tiny scuba tanks) from which the air is pumped out with a vacuum pump on the surface and sealed with the valve. On the bottom gases are captured underneath an overturned funnel so that a large gas headspace is developed. Then the value on the pressure vial is opened, gas is sucked into the vial, and the vial's value is re-closed. This way a sample of the gas at the high seafloor pressures is recovered.In situ ultraviolet spectrophotometer (ISUS)
The ISUS is a sensor used to measure concentrations of dissolved chemicals directly from their Ultraviolet Absorption Spectrum. A variety of chemicals absorb light in the UV and each of these chemicals has a unique absorption spectrum. We can determine the concentration of these chemicals directly, with no chemical manipulation, by measuring the absorption spectrum of seawater in the UV and then deconvolving the spectra to yield the concentration of each component. ISUS has been used to determine nitrate concentrations while deployed on CTD/Rosette profilers, undulating towed vehicles such as a SeaSoar or SeaSciences Acrobat, and on deep-sea moorings. It has also been used to measure sulfide flux from cold seeps in Monterey Bay while deployed on the ROV Ventana.
A push-core looks like a clear plastic tube with a rubber handle on one end. Just as its name implies, the push core is pushed down into loose sediment using the ROV's manipulator arm. As the sediment fills up the core, water exits out the top through one-way valves. When the core is pulled up again, these valves close, which (most of the time) keeps the sediment from sliding out of the core tube. When we bring these cores back to the surface, we typically look for living animals and organic material in the sediments.
Vibracoring is a common technique used to obtain samples from water-saturated sediment. These corers work by attaching a motor that induces high frequency vibrations in the core liner that in turn liquefies the sediment directly around the core cutter, enabling it to pass through the sediment with little resistance.Gravity corer
Device lowered off the ship to the seafloor on a wire which consists of a long tube that extends below a moderately heavy weight. When the device encounters the bottom, the weight forces the tube into the sediments. When it is pulled out of the bottom the tube will contain a sediment sample (i.e., core) of the upper layers of the ocean floor.
R/V Western Flyer
ROV Doc Ricketts
Leg 5 Research Team
Charlie Paull has been a marine geologist and geochemical stratigrapher at MBARI since January 1999. The central theme of Charlie's work involves investigating the fluxes of fluids and gases through continental margins. Over the past decade his primary focus has been gas hydrate research on the Blake Ridge gas hydrate field on the continental rise off of southeastern North America. Assessing the global distribution of gas hydrate and interstitial gas is a continuing interest as well as the development of new techniques to detect the presence of gas hydrate in marine sediments. Charlie's other ongoing work is focused on the geology associated with seafloor seepage sites, including investigating the deposits associated with chemosynthetic communities, determining the processes that occur at the methane-sulfate boundary, and understanding the origin of pockmarks and other potential seafloor fluid venting sites.
Ken's research interests are focused on the development of new analytical methods for chemicals in seawater and application of these tools to studies of chemical cycling throughout the ocean. Over the past 15 years, Ken's Chemical Sensor Program at MBARI has developed a variety of sensors and analyzers that operate in situ to depths of 4,000 meters. These instruments have been used to study processes ranging from the distribution of sulfide in deep-sea hydrothermal vent systems, to nitrate in coastal ponds surrounded by intensive agricultural activities.
Krystle Anderson is a research technician working for Charlie Paull in the Continental Margins Lab. Krystle's background is primarily in the acquisition and processing of seafloor mapping data. She came from the California State University, Monterey Bay Seafloor Mapping Lab where she obtained her data processing and Geographic Information System (GIS) skills. Krystle spends a majority of her time processing and creating high-resolution maps of multibeam data collected from the mapping AUV. The high-resolution maps Krystle helps create will then be used to aid navigation for the ROV to explore particular areas of interest. On this expedition Krystle will assist with running the GIS system, and processing and cataloguing sediment samples and vibracores. This is Krystle's second research expedition with MBARI and she is very excited to be involved in this expedition.
Roberto is a geochemist by training. His interests lie at the intersection of marine geology and sediment and water chemistry. During cruises Roberto operates a custom-built, portable chemistry lab that includes a complete set of analytical platforms for measurements of fluids and gases. On this expedition, Roberto will be responsible for analytical measurements of pore water chemistry on samples taken from sediment cores. He will also be in charge of collecting gas samples emanating from fluid vents and performing hydrocarbon analyses on dissolved gases collected from pore waters, from gas vents and from seawater.
Eve Lundsten works with Charlie Paull in the Continental Margins Lab. Eve's background is in hydrology but she uses her technical and mapping skills to help understand the processes that create the morphology we see on the seafloor. The Continental Margins Lab uses high-resolution, AUV-collected bathymetric maps to help direct research to the precise location of interest on the seafloor where samples can be collected for further analysis. Eve's responsibilities on this cruise include running the GIS mapping system, assisting with the processing of vibracores, and push cores collected on ROV dives, and documentation of the many samples collected during this leg of the cruise. Eve is very excited to participate in this cruise and is looking forward to many exciting discoveries.
Shannon is a molecular ecologist. This means she uses genetics to solve mysteries about how invertebrates like worms, snails, mussels and clams, who live at hydrothermal vents, cold seeps, wood, and whale falls move around in the deep sea. These environments act like islands in the ocean because most of the animals that inhabit these environments depend on chemosynthetic bacteria for food. The reducing environments provide mineral-rich water that feed the bacteria, creating an abundance of life. On the cruise, Shannon will be responsible for collecting, identifying, and dissecting invertebrates as well as filtering water to study their larvae.
Susan von Thun
Susan works in the video lab at MBARI, where she is a senior research technician. Her primary role at MBARI is to help manage and annotate the remotely operated vehicle (ROV) video archive. Observations about the biology, geology, and equipment in ROV videos are logged using software designed by MBARI engineers called the Video Annotation and Reference System (VARS). On this expedition, Susan will use VARS to annotate and document video coming back to the ship from ROV Doc Ricketts. As one of the few biologists on this leg of the expedition, Susan will be busy identifying and processing biological samples.
Teresa has worked as a Logistics Specialist in the Division of Marine Operations at MBARI for 12 years. She has spent much of the past year planning and preparing for this expedition, including obtaining scientific permits from the Mexican government, scheduling the science missions and port stops, arranging for services during port stops, and arranging visas for the scientists. During this expedition Teresa will help process samples collected with the ROV, assist in the ROV control room with video tapes and frame grabs, and other science tasks. Teresa is very excited to sail as a member of the science team and will no doubt learn a lot from both marine operations and science perspectives.
Brian specializes in sedimentary processes and stratigraphy, integrating insights gleaned from seafloor rock and sediment samples with information from remote-mapping products, such as close-up photographs of the seafloor, high-resolution bathymetric maps, and seismic-reflection profiles. His recent studies have focused on how sediment moves from the land to the deep sea, processes controlling submarine landslides, saltwater intrusion into coastal aquifer systems, marine pollution, seafloor habitats, and the Cenozoic history of the Arctic Ocean.
Juan Carlos Herguera
Juan Carlos is interested in the history of past oceans, how changes in climate and ocean circulation contribute to the ecology and biogeochemical cycling sustained by coastal environments in the California Current and the Gulf of California regions. During this cruise he will be involved in sampling benthic foraminifera to help characterize their genomic information, and, through their stable isotopic and metal compositions, to understand how these geochemical markers reflect their ambient conditions. He will further use planktonic foraminifera for dating the deep-sea cores with radiocarbon techniques, which hold important clues on the tectonic rupturing rhythm along the boundary between the North American and Pacific plates. He is fascinated by these new observation windows opened up by the ROV deployed from the Western Flyer, making possible the discovery of new vent environments along these fractured boundaries and the chemosynthetic oasis sustained by these leaky enclaves that connect the deep ocean with the lower crust and mantle dynamics.
Mary's interests focus on using microbiota (primarily foraminifera but also pollen) to investigate marine sediment transport, geohazards (faulting, landslides and paleotsunamis), climate change, and the pathways and impact of invasive species introductions using sediment records and molecular analysis techniques. She also uses foraminifera in biomonitoring marine pollution sites and carbon-14 chronostratigraphy—the study of the age of rock layers in relation to time.
Luis Arturo Terán Ortega
As a member of the Mexican Geological Survey (SGM), Luis has conducted extensive geological research and prospective surveying mining studies focused on detecting resources with potential economic value. In 2007, the Mexican government commissioned the Mexican Geological Survey to conduct prospective efforts over the entire Mexican territory and adjacent sea to identify potential energy resources such as gas, coal, uranium, and other strategic minerals. Luis is the Manager of Regional Exploration of SGM and his prospective studies encompass Sonora, the Gulf of California, the Baja California peninsula, and the territorial Sea in the Pacific Ocean. This is his first experience on a research cruise and he hopes to gain a better understanding of the richness of the Gulf of California environment from a geologic, biologic, and mineral resources perspective. Luis is very eager to learn from and collaborate with his peers from MBARI.