Research

This study will collect temperature measurements in seafloor sediments offshore Washington and Oregon, and map the distribution of those sediments, to understand the controls on temperatures in the system and improve estimates of subduction zone temperatures. The results of this research have direct societal benefit, by informing earthquake hazard estimates. In addition, the proposed project will enhance education at New Mexico Tech, a STEM-focused Hispanic-serving institution. Two graduate students will be trained in geophysics and hydrogeology. Results of the project will be incorporated into ?using data in the classroom? efforts, improving hands-on experience in undergraduate courses.

The Southeast Fishery-Independent Survey carries out fishery-independent surveys of reef-associated fish species in the US South Atlantic. The survey uses baited chevron traps outfitted with video cameras to index reef fish abundance, and CTD casts to determine environmental conditions. Survey data is combined with data from SCDNR to better manage fish species in the region.

Due to the anomalous behavior of fresh water, which below 3.98C has a negative thermal expansion coefficient, convection occurs when the surface of a mid- to high latitude freshwater lake is heated in the spring. This implies that convection can be driven by shortwave radiation in the absence of wind on calm, sunny days. Observations over the last several years in Lake Superior, made as part of unrelated fieldwork, have provided an opportunity to start to explore the dynamics of this convective process from a number of different platforms, including moored and glider-based observations. Observations show parcels of water being warmed at the surface and transported to the bottom (O(200m)) on the order of hours, and suggest short (O(10m)) horizontal scales for convective chimneys, providing real challenges for observations and models alike. This project will combine observations, numerical modeling, and analytical work to determine and understand the spatial and temporal scales of the instability process. Lakes at mid-to high latitudes can spend a significant portion of the year in this state, during which these dynamics will dominate circulation and mixing. From a fundamental fluid dynamics perspective, this phenomenon provides an opportunity to study buoyancy-driven convection in the absence of other forcing mechanisms such as surface waves and wind-driven currents, in contrast to most significant examples of oceanic convection. This process may have significant impacts on primary productivity, since the strong convection, spanning the water column, will make it impossible for primary producers to maintain their position in the euphotic zone. In addition, parcels of water are being transported from the surface of the lake to the bottom on timescales of hours, and may have significant impacts to lake sediment biogeochemistry. A graduate student will be supported at each of the three institutions involved. An interactive one dimensional mixing model will be developed for classroom use, similar to tools already developed by one of the PIs. This work will foster collaboration between limnologists and oceanographers. The centerpiece of the field work will consist of a "horizontal mooring" equipped with fast thermistors as well as ADCPs capable of measuring vertical velocities, and an auxiliary mooring to measure surface heat fluxes. Glider transects and velocity microstructure surveys will be taken during both calm and windy conditions. Modeling will consist of an exploration of parameter space using direct numerical simulation and large eddy simulations. Analytical methods will be used to constrain the parameter space. Unlike well-studied Rayleigh-Benard convection, the process is driven by injection of Available Potential Energy directly into the bulk of the fluid. The researchers intend to study not just the turbulent properties of the phenomenon, as in most of the existing literature, but also approach it from the novel perspective of an instability problem.

Thousands of natural gas seeps have been discovered as streams of bubbles rising up from the seafloor just offshore from coastlines around the world. Extensive fields of seeps, largely releasing the same methane gas that we use to heat our homes, have recently been found about a hundred miles east of North Carolina?s Cape Hatteras at water depths as shallow as 300 feet. It is estimated that at least tens of thousands of these hydrocarbon-rich seeps occur on continental margins around the world. The seeps, usually seen as large rising plumes by sonar systems on research ships, inject huge, but poorly quantified, amounts of methane into overlying waters as they rise through the water column. A primary question is how much of the methane, a potent greenhouse gas, actually reaches the atmosphere. This question is the subject of much current research funded by several Federal research agencies including the National Science Foundation and the Department of Energy. Oceanographers believe that the methane (and other gases included in the bubble streams such as ethane and propane) are either transported away by ocean currents or consumed by microorganisms specially adapted to live with hydrocarbons as their main carbon source. This proposal seeks to determine the importance of microbial consumption in controlling methane distributions in the deep ocean and how the consumption rates depend on concentrations of methane, oxygen and other chemicals, as well as in situ pressures and temperatures. Previous studies in laboratories aboard research ship using samples returned to the surface suggest that microbial consumption of methane from the seeps may lag for a week after its injection into the water column and thus that physical dispersion by currents may dominate deepwater methane dynamics through dilution. However, other measurements suggest that there is no lag before aggressive microbial oxidation of injected methane begins. We have proposed to conduct in situ measurements of microbial methane consumption and related microbial community structure in bottom waters at several coastal and continental margin sites off the North Carolina coast and the northern Gulf of Mexico, where numerous natural seeps have also been observed. We will use new technologies developed after the release of massive quantities of methane during the Deepwater Horizon disaster in the Gulf. The sites offer varying concentrations of methane and other chemical and physical conditions such as oxygen concentrations and temperature that will allow us to test specific hypotheses about the role of microbial processes. Through performing the experiments with instruments right on the seafloor next to the seeps we can remove much of the uncertainty surrounding previous shipboard measurements. We will use newly developed seafloor landers equipped with advanced laser methane sensors that are capable of multi-week measurements while assaying dissolved oxygen, dissolved inorganic nitrogen and the microbial community for the presence of methane-consuming methanotrophs and their activity using advanced genomics techniques that can reveal the nature of methanotrophic responses to ambient methane concentrations. Successful collection of in situ methane consumption rate data and associated microbial community changes should prove important for modeling ocean methane dynamics over a range of oceanographic conditions including seep-enriched bottom waters and bottom waters impacted by accidental hydrocarbon releases. Graduate and undergraduate students supported by the project will gain critical skills in laboratory and field settings and will also benefit from frequent interactions with established researchers from diverse fields. Team members will participate in hands-on undergraduate education and training through developing individualized research projects leading to honors theses, presentations at national meetings and excellent graduate school placements. Graduate and undergraduates will also participate in K-12 science outreach efforts that help to attract and inform the next generation of oceanographers. The team will work with the University of North Carolina Morehead Planetarium and Science Center and participate directly in the North Carolina Science Festival. Through media contacts made from TED talks, exciting results will be broadly disseminated to the public. The project will have immediate relevance for understanding microbially mediated responses to hydrocarbon inputs from accidental releases along the Southeast Atlantic margin where oil and gas exploration are a constant topic of state and national policy discussions. Hundreds of recently discovered gas seeps along the continental margin offshore of Cape Hatteras, North Carolina plus thousands in the northern Gulf of Mexico, inject huge amounts of dissolved methane into overlying shelf and slope waters through dissolution of rising bubble plumes. The fate of the methane is largely controlled by a balance between microbial oxidation and advective transport away from seep sources. The efficacy of microbial oxidation likely depends on concentrations of methane, oxygen and ambient dissolved inorganic nitrogen (DIN), as well as in situ pressures and temperatures. Recent shipboard aerobic methane oxidation rate (AMOR) measurements suggest that microbial consumption of seep methane may lag for a week and thus physical dispersion could dominate deepwater methane dynamics through dilution. However, methane stable carbon isotopic measurements in bottom waters suggest that there is no lag before aggressive oxidation of injected methane begins. We propose to conduct in situ measurements of AMOR while simultaneously investigating its microbial drivers at representative North Carolina and Gulf of Mexico continental margin sites featuring numerous active bubble seeps. These sites offer varying concentrations of methane and DIN; performing the experiments in situ will remove much of the uncertainty of shipboard rates. We will conduct the measurements utilizing newly developed benthic lander systems equipped with advanced laser methane sensors that are capable of multi-week AMOR measurements while assaying dissolved oxygen, DIN and the microbial community for the presence of methanotrophs (through metagenomes) and their activity (through metatranscriptomes) that can reveal the nature of methanotrophic responses to ambient methane concentrations. The project will test key hypotheses about deep-sea methane dynamics including determining if there are significant lags in microbial responses after exposure to elevated methane concentrations, determining the relationships of AMOR to methane and DIN concentrations and investigating the response times and magnitude of methanotrophs to spatial and temporal variability in methane concentration. Successful collection of in situ AMOR and associated microbial community data will prove important for modeling ocean methane dynamics over a range of oceanographic conditions including seep-enriched bottom waters and accidental hydrocarbon releases. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

The Coastal Land Air-Sea Interaction (CLASI) experiments describes a full scale experimental effort by deploying multiple air-sea interaction spar (ASIS) buoys in conjunction with other nearshore buoys and land-based tower to measure the air-sea interaction exchange in the coastal ocean from the land dunes to the beach to the surf zone and over the inner shelf into shallow water. The full experiment plan was developed by the CLASI team and includes previous results from the CLASI Pilot Experiment and lessons learned as well as shortcomings missed during the Pilot experiment. The goal is to deploy, operate and recover the five existing ASIS buoys and build three additional ASIS buoys to accommodate specialized measurements (EM/qT) in support electromagnetic ducting in the coastal region. These buoys constitute the core asset of the CLASI plan since they together with the shallower version I-SPAR buoys can measure directly the air-sea fluxes and turbulence both on the atmospheric and oceanic side of the air-water interface. From this unique set of observations, we propose to develop coast-aware parameterizations of air-sea coupling. In addition, we will operate two X-band radar systems on the land near the coast to continuously record the coastal wave climate and dynamics as well as wind speed and direction.

Recent storminess combined with decreasing extent and duration of sea ice in the Bering Sea has significantly affected Alaska’s Arctic coastline, substantially disrupting communities, threatening commerce including commercial fishing, and posing new challenges to our military and vital marine transportation systems. Unfortunately, our knowledge of past storminess is limited to the last few decades, so we know little about past variability in extreme storms. This hinders our ability to diagnose the causes of changes in storminess and to plan for and address future storm impacts. With this project we will provide comprehensive storm data sets for the central Aleutian Islands that span the last two millennia, providing important context to current and future storm climates. A research cruise along Alaska’s Aleutian Islands will allow us to access remote fjords and collect a series of sediment cores and environmental measurements that have the potential to decipher the history of ancient storm events impacting the area. These storm reconstructions will improve our understanding of how intense storminess has changed in the Bering Sea and allow examination of the regional environmental factors that enhance or inhibit storm activity. The lessons learned from this research will be useful to the scientific community, planners, and local decision makers and will improve preparedness and resilience to future storm activity and coastal hazards. Because the modern instrumental record of storminess in the Bering Sea is limited, we know little about the variability of intense storminess prior to the last few decades. To address this gap in knowledge we will develop reconstructions of extreme storms over the last few millennia from coarse-grained event beds in deep coastal basins along the north coast of the Aleutians. Using sedimentological, geophysical and numerical modeling techniques, coupled with local instrumentation (wave, current, pressure sensors), and the collection of local oral and written storm narratives we will; 1) develop reconstructions of coarse-grained event beds over several millennia, 2) measure real-time storm-related coastal processes to determine thresholds for event bed deposition and provide National Weather Service data for real-time storm and flood impact forecasting, 3) engage with local communities to develop a chronology of historical storm affects, and 4) differentiate other mechanisms of event bed deposition and develop a record of relative sea-level change and potentially great earthquakes and tsunamis. This research is tightly coupled with a field- and lab-based education plan focused on building coastal science literacy to support informed decision-making. Extreme storms endanger Alaskan Native coastal communities already at risk from increased flooding and erosion and threaten critical infrastructure and access to subsistence resources. A collaboration with the Qawalangin Tribe of Unalaska will serve to build synergy between scientists, local stakeholders, and community residents. Tribal participation in the planning and carrying out of research activities, the production of a professional outreach video/photo blog, and design of a portable educational exhibit and accompanying curriculum materials will provide many opportunities for meaningful engagement and the promotion of STEM fields to under-represented groups. The research will also incorporate undergraduate and graduate students with targeted efforts to increase the representation of Alaska Natives, women, minorities, and people with disabilities in STEM fields. We will widely present to the public and scientific audiences through multiple media and at professional conferences and publications.

Thousands of natural gas seeps have been discovered as streams of bubbles rising up from the seafloor just offshore from coastlines around the world. Extensive fields of seeps, largely releasing the same methane gas that we use to heat our homes, have recently been found about a hundred miles east of North Carolina?s Cape Hatteras at water depths as shallow as 300 feet. It is estimated that at least tens of thousands of these hydrocarbon-rich seeps occur on continental margins around the world. The seeps, usually seen as large rising plumes by sonar systems on research ships, inject huge, but poorly quantified, amounts of methane into overlying waters as they rise through the water column. A primary question is how much of the methane, a potent greenhouse gas, actually reaches the atmosphere. This question is the subject of much current research funded by several Federal research agencies including the National Science Foundation and the Department of Energy. Oceanographers believe that the methane (and other gases included in the bubble streams such as ethane and propane) are either transported away by ocean currents or consumed by microorganisms specially adapted to live with hydrocarbons as their main carbon source. This proposal seeks to determine the importance of microbial consumption in controlling methane distributions in the deep ocean and how the consumption rates depend on concentrations of methane, oxygen and other chemicals, as well as in situ pressures and temperatures. Previous studies in laboratories aboard research ship using samples returned to the surface suggest that microbial consumption of methane from the seeps may lag for a week after its injection into the water column and thus that physical dispersion by currents may dominate deepwater methane dynamics through dilution. However, other measurements suggest that there is no lag before aggressive microbial oxidation of injected methane begins. We have proposed to conduct in situ measurements of microbial methane consumption and related microbial community structure in bottom waters at several coastal and continental margin sites off the North Carolina coast and the northern Gulf of Mexico, where numerous natural seeps have also been observed. We will use new technologies developed after the release of massive quantities of methane during the Deepwater Horizon disaster in the Gulf. The sites offer varying concentrations of methane and other chemical and physical conditions such as oxygen concentrations and temperature that will allow us to test specific hypotheses about the role of microbial processes. Through performing the experiments with instruments right on the seafloor next to the seeps we can remove much of the uncertainty surrounding previous shipboard measurements. We will use newly developed seafloor landers equipped with advanced laser methane sensors that are capable of multi-week measurements while assaying dissolved oxygen, dissolved inorganic nitrogen and the microbial community for the presence of methane-consuming methanotrophs and their activity using advanced genomics techniques that can reveal the nature of methanotrophic responses to ambient methane concentrations. Successful collection of in situ methane consumption rate data and associated microbial community changes should prove important for modeling ocean methane dynamics over a range of oceanographic conditions including seep-enriched bottom waters and bottom waters impacted by accidental hydrocarbon releases. Graduate and undergraduate students supported by the project will gain critical skills in laboratory and field settings and will also benefit from frequent interactions with established researchers from diverse fields. Team members will participate in hands-on undergraduate education and training through developing individualized research projects leading to honors theses, presentations at national meetings and excellent graduate school placements. Graduate and undergraduates will also participate in K-12 science outreach efforts that help to attract and inform the next generation of oceanographers. The team will work with the University of North Carolina Morehead Planetarium and Science Center and participate directly in the North Carolina Science Festival. Through media contacts made from TED talks, exciting results will be broadly disseminated to the public. The project will have immediate relevance for understanding microbially mediated responses to hydrocarbon inputs from accidental releases along the Southeast Atlantic margin where oil and gas exploration are a constant topic of state and national policy discussions. Hundreds of recently discovered gas seeps along the continental margin offshore of Cape Hatteras, North Carolina plus thousands in the northern Gulf of Mexico, inject huge amounts of dissolved methane into overlying shelf and slope waters through dissolution of rising bubble plumes. The fate of the methane is largely controlled by a balance between microbial oxidation and advective transport away from seep sources. The efficacy of microbial oxidation likely depends on concentrations of methane, oxygen and ambient dissolved inorganic nitrogen (DIN), as well as in situ pressures and temperatures. Recent shipboard aerobic methane oxidation rate (AMOR) measurements suggest that microbial consumption of seep methane may lag for a week and thus physical dispersion could dominate deepwater methane dynamics through dilution. However, methane stable carbon isotopic measurements in bottom waters suggest that there is no lag before aggressive oxidation of injected methane begins. We propose to conduct in situ measurements of AMOR while simultaneously investigating its microbial drivers at representative North Carolina and Gulf of Mexico continental margin sites featuring numerous active bubble seeps. These sites offer varying concentrations of methane and DIN; performing the experiments in situ will remove much of the uncertainty of shipboard rates. We will conduct the measurements utilizing newly developed benthic lander systems equipped with advanced laser methane sensors that are capable of multi-week AMOR measurements while assaying dissolved oxygen, DIN and the microbial community for the presence of methanotrophs (through metagenomes) and their activity (through metatranscriptomes) that can reveal the nature of methanotrophic responses to ambient methane concentrations. The project will test key hypotheses about deep-sea methane dynamics including determining if there are significant lags in microbial responses after exposure to elevated methane concentrations, determining the relationships of AMOR to methane and DIN concentrations and investigating the response times and magnitude of methanotrophs to spatial and temporal variability in methane concentration. Successful collection of in situ AMOR and associated microbial community data will prove important for modeling ocean methane dynamics over a range of oceanographic conditions including seep-enriched bottom waters and accidental hydrocarbon releases. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Systematic long-term (greater than a few decades in length) time-series observations of aquatic and terrestrial environments have led to a more comprehensive understanding of the natural ecosystem variability and have enabled an assessment of human impacts on ecosystem dynamics. Because of their ability to store and transport large amounts of heat and to absorb carbon dioxide from the atmosphere, the world's oceans play a critical role in modulating environmental conditions for the sustained well-being of both land-based and marine organisms including humans. Despite their recognized scientific and societal importance, long-term records of key ocean processes are rare. In 1988, two ocean time-series programs were established: one in the North Atlantic near Bermuda and the other, the Hawaii Ocean Time-series (HOT) program, near Hawaii. For the past three decades, teams of scientists based at the University of Hawaii have made critical measurements of the 'state of our sea.' These long-term observations have established a baseline against which future states can be compared. The ship-based HOT program complements other diverse ocean observation programs including remote-sensing via satellites, moored buoys, profiling floats, and autonomous underwater vehicles. All HOT program data are publicly available and are frequently used by researchers and policy makers around the world.

The northwest Atlantic is renowned for productive fisheries that depend upon a complex food web of planktonic organisms that provide them energy. In these waters -- as in coastal waters around the globe -- human activities, environmental variability, and decadal-scale change intersect to have diverse effects on the planktonic food web. It is crucial to understand the structure of this web, how it functions, and how it responds to seasonal environmental change, in order to respond appropriately to long-term trends that are accelerating in this region. Our understanding, however, has been limited by a lack of systematic and detailed measurements over a sufficient length of time so that we can observe the responses of these webs to environmental perturbations and uncover the underlying causes and implications. The Northeast US Shelf (NES) Long-Term Ecological Research (LTER) project will provide such observations, analyze them with a variety of models, and improve our ability to predict how planktonic food webs change through space and time, and how those changes impact the productivity of higher trophic levels including commercially important fish. In addition, the NES-LTER project will have multifaceted broader impacts, including collaboration with the National Oceanic and Atmospheric Administration's (NOAA), Northeast Fisheries Science Center to support multispecies, ecosystem-based management on the NES. The project includes an education plan that will provide opportunities to a broad range of learners and a far-reaching public outreach component will be developed through NOAA's international Science-On-a-Sphere network. While patterns of ecosystem change over seasons to decades have already been documented in this region, the key mechanisms linking changes in the physical environment, planktonic food webs, and higher trophic levels remain poorly understood. For this reason, predictive capability is limited and management strategies are largely reactive. To address these needs, the NES-LTER strategy combines observations that provide regional-scale context, process cruises along a high gradient cross-shelf transect, high-frequency time series at inner- and outer-shelf locations, coupled biological-physical food web models, and targeted population models. The research plan is guided by an overarching science question: How is long-term environmental change impacting the pelagic NES ecosystem and, in particular, affecting the relationship between compositional (e.g., species diversity and size structure) and aggregate (e.g., rates of primary production, and transfer of energy to important forage fish species) variability? By capitalizing on high levels of seasonal and interannual variability in the NES, the research will study short-term responses to change in the environment to a) characterize low and high export food webs, b) understand the linkages and transfer of energy from the phytoplankton to pelagic fish, and c) identify the mechanisms that underlie shifts between high and low export communities. Ultimately, mechanistic knowledge will be scaled up to understand and predict the impacts and feedbacks associated with trends in decadal-scale forcing in the ecosystem.

Convective forces deep below Earth?s surface cause tectonic plates (continents and seafloor) to slowly move at many centimeters (several inches) each year. In places, the plate boundaries must slide past one another to accommodate this motion. Sometimes this occurs smoothly, but sometimes the plate edges are stuck together by friction and don't slide at all until enough stress builds to the point where the plates slip past each other suddenly in an earthquake. Over the past two decades, a different form of tectonic boundary slip has been studied in which built up stress is relaxed episodically, as in an earthquake, but at a much slower rate taking days, weeks, months, or even years to gradually slip. These events are called "slow slip events" or "slow earthquakes." Because the motions are gradual they do not generate seismic shaking (as normal earthquakes do), making them far less dangerous. However, slow slip events occurring near areas that are frictionally stuck may trigger large earthquakes, a phenomenon that requires further study. This study focuses on searching for slow slip events in the offshore, shallow part of the Cascadia subduction zone, which lies offshore the western United States stretching from northern California to north of the Canadian border. Here an oceanic tectonic plate is colliding with North America, producing very large destructive earthquakes and tsunamis every few hundred years. The lack of seismic shaking associated with slow slip events makes these events difficult to detect, especially offshore. On land they are evident in precise, continuous GPS records which show plate motions of several centimeters that start and stop over a few weeks. Such motions are much more difficult to observe on the seafloor because GPS signals do not penetrate sea water. Consequently alternative methods must be devised to detect offshore slow slip events. This research project will record very precisely the lengths of optical fibers stretched across the seafloor near the Oregon coast. If a slow slip event occurs in the region near the optical fibers, the associated optical length change will be recorded by a battery powered laser system at the end of each optical fiber. Studying such events offshore will help to build models of their influence on the timing and location of great earthquakes, and may lead to future advances in earthquake forecasting. The project supports the training of a student. Widespread deployments of GPS sensors in the past decade have helped identify Slow Slip Events (SSEs), especially near subduction zone faults in Cascadia, Costa Rica, Japan, and New Zealand. Understanding SSEs presents an opportunity to gain new insights into the mechanism governing locking and unlocking of subduction zone and other faults, and may be important in assessing the hazard levels presented from potential great earthquakes and tsunami. In particular, SSEs occurring at the downdip limit of the strongly locked zone may pose a risk of triggering large earthquake ruptures. It is therefore critical to search for SSEs occurring at the base of the locked zone, which in Cascadia (as in most subduction zones) lies offshore. In this study, two orthogonal optical fiber strainmeters will be installed on the seafloor above the Cascadia subduction zone to detect offshore SSEs. A recent study of the cumulative effect of SSEs in Cascadia using onshore GPS data indicates possible offshore slow slip at the base of the locked zone which is hypothesized to occur simultaneously with onshore SSEs. However, the detection of this slip using onshore GPS is very weak. Confirming the presence or absence of offshore slow slip in Cascadia is important for understanding the potential role of SSEs in influencing the timing and location of the next great earthquake. While GPS networks have sufficient sensitivity to map the location of SSEs onshore, they do not cover that portion of the crust under the oceans, nor are they able to distinguish the timing of sub-events because of the need for averaging over daily periods. In contrast, optical fiber strainmeters can be deployed offshore and have their best signal to noise ratio at shorter periods, complementing onshore GPS both in location and frequency band. Because SSEs evolve in complex patterns indicative of propagating stress fronts, it is important to resolve, both in scale and time, the deformation signals in order to understand more fully the evolution of the rupture plane. In conjunction with GPS, the availability of highly sensitive and stable strainmeters offshore will enable such characterizations. The measurements in this study will be timed with an expected onshore SSE to capture the hypothesized offshore slip, testing this model and others that address the extent of an offshore locked zone. In addition to the detection of SSEs, a number of other studies will become feasible following the deployment of this offshore strainmeter, including investigation of strain from traveling seismic waves and tidal observations for inferring local Earth structure. In addition, the work will advance the technology of optical fiber sensors and likely find applications in other disciplines

We will deploy seafloor geodetic transponders offshore the Oregon coast within about 100 miles of Newport.

We are extending the time series of seafloor benchmarks at three sites on the accretionary prism in the Cascadia subduction zone offshore Oregon using the GNSS-Acoustic method. These seafloor sites were established in the past five years with varying numbers of surveys on each, yielding initial estimates of plate velocities at three of four sites along the margin. Three surveys will be performed with a GNSS-Acoustic-equipped Wave Glider in our two-year project. The Wave Glider approach greatly reduces the survey cost compared to that undertaken with a research vessel. As the uncertainty in a time series slope decreases linearly with the total duration or the data set and as the square-root of the number of samples, it is critical to maintain these time series to be able to reduce the uncertainties in local seafloor velocities. This will allow us to better distinguish among different models of plate locking. In addition to undertaking the geodetic surveys, we will explore means to improve the data processing through algorithms designed to mitigate biases from the acoustic velocity structure of the water column and by capitalizing on multi-GNSS data. Finally, we will perform a modeling exercise to estimate the amount of kinematic locking at the trench using elastic boundary element models, with the goal to identify if plate locking varies along strike and correlates with structurals features in the outer accretionary prism.

The northern Gulf of Mexico is the second largest human-caused area of bottom-water dissolved oxygen less than 2 milligrams per liter in the world's coastal ocean. It is located primarily west of the Mississippi River, which drains 41% of the contiguous 48 United States. Besides the freshwater and sediments delivered to the northern Gulf of Mexico via the Mississippi River delta, there are also dissolved inorganic nutrients (Nitrogen and Phosphorus) and organic and inorganic suspended particles. The nutrient levels of N have risen since the mid-1950s to a level that is three times that of the last mid-century. The area of low oxygen has become larger, and the low values are more severe than they were historically. In fact, palaeoindicators dating back to the 1800s indicate that widespread low oxygen conditions did not exist historically and the low dissolved oxygen conditions worsened since the 1950s and accelerated in the 1970s coincident with the nitrogen load from the Mississippi River. Our research group has been documenting the area of low oxygen, and its areal extent since 1985. These cruises collect physical, hydrographic, sedimentological, chemical and biological data in the process of outlining the bottom area of the bottom-water low oxygen. The size of the bottom-water area of low oxygen is a benchmark for the Federal/State Mississippi River/Gulf of Mexico Hypoxia Task Force to measure progress toward an environmental goal of 2,500 kilometers square of bottom area by 2035. The reduction is size is relatled to the necessary reduction in nitrogen and phosphorus loads to the Gulf from the Mississippi River watershed. States participating in the Hypoxia Task Force have developed and attempted to reach goals for mitigation of excess nutrients, primarily from agricultural landscape, but also from cities, and atmospheric deposition.

The northern Gulf of Mexico is the second largest human-caused area of bottom-water dissolved oxygen less than 2 milligrams per liter in the world's coastal ocean. It is located primarily west of the Mississippi River, which drains 41% of the contiguous 48 United States. Besides the freshwater and sediments delivered to the northern Gulf of Mexico via the Mississippi River delta, there are also dissolved inorganic nutrients (Nitrogen and Phosphorus) and organic and inorganic suspended particles. The nutrient levels of N have risen since the mid-1950s to a level that is three times that of the last mid-century. The area of low oxygen has become larger, and the low values are more severe than they were historically. In fact, palaeoindicators dating back to the 1800s indicate that widespread low oxygen conditions did not exist historically and the low dissolved oxygen conditions worsened since the 1950s and accelerated in the 1970s coincident with the nitrogen load from the Mississippi River. Our research group has been documenting the area of low oxygen, and its areal extent since 1985. These cruises collect physical, hydrographic, sedimentological, chemical and biological data in the process of outlining the bottom area of the bottom-water low oxygen. The size of the bottom-water area of low oxygen is a benchmark for the Federal/State Mississippi River/Gulf of Mexico Hypoxia Task Force to measure progress toward an environmental goal of 2,500 kilometers square of bottom area by 2035. The reduction is size is relatled to the necessary reduction in nitrogen and phosphorus loads to the Gulf from the Mississippi River watershed. States participating in the Hypoxia Task Force have developed and attempted to reach goals for mitigation of excess nutrients, primarily from agricultural landscape, but also from cities, and atmospheric deposition.

Climate change research requires knowledge of the temperature of the ocean right at the surface to estimate the transfer of heat between the air and the water. This temperature, known as the skin temperature, can be up to a half degree Celsius (about one degree Fahrenheit) cooler than the temperature immediately below, known as the sub-skin temperature. In practice, models rather than measurements of the skin temperature are used since current technology to measure the skin temperature is expensive and complicated. This technology uses a non-contact sensor known as an infrared radiometer that remotely measures the thermal radiation coming from the ocean. The skin temperature model needs a measure of the temperature just below the surface (known as the sub-skin temperature) in order to accurately predict the skin temperature. When a ship is used, the sub-skin temperature can be measured by towing a thermometer along the surface. In the future, measurements will be made from drones, where towing a thermometer is impractical. This research will use technology improvements and insight from new research to develop an instrument that can measure both the skin and sub-skin temperature from drones, as well as from buoys. Current models for the cool skin effect provide adequate skin temperature accuracy for ocean surface fluxes required for climate research. However, this level of performance is achieved only when the cool skin model is initialized with a contact measurement of very near surface temperature using a towed sensor known as a sea snake. The advent of reliable unmanned surface vehicles (USVs) has fostered a growing community consensus for the need to make accurate flux measurements autonomously. Since deployment of a sea snake from USVs is impractical, an alternative means of obtaining very near surface temperature (sub-skin) and/or the skin temperature itself is required to ensure the necessary flux accuracy. Recent results indicates that accurate infrared (IR) measurements of skin temperature from USVs should now be practical. Furthermore, these results show that combining an IR camera with a calibrated radiometer system can provide the sub-skin temperature remotely. This project will develop and test IRISS (InfraRed In situ Skin and Subskin), an innovative IR-based sensor system to remotely and simultaneously measure skin and sub-skin temperature under all weather conditions for routine deployment on USVs and buoys. IRISS will be compact, low-power, and cost effective by exploiting the increased stability of commercially-available sensors and will provide measurements with accuracy comparable to current systems. The project will include side-by-side comparisons with an existing ship-based system for each intended platform. Widespread use on USVs and buoys will greatly increase the number and coverage of skin and sub-skin temperature measurements. The resulting improvements to models for the cool skin and near surface temperature stratification will enhance topical oceanographic research such as gas transfer, address current operational forecast priorities, and improve satellite SST algorithm development.

Our intent is to characterize the benthos and benthic fluxes at four shelf sites off central Oregon and four sites off southern Washington during summertime. We will deploy moored landers that support eddy covariance sensors, collect hydraulically-damped frame-supported gravity cores for core incubation, collect box cores for macrofauna enumeration, and perform CTD/rosette casts for water column characterizations. A drop camera system may also be deployed.

Part 1: A significant shortage of United States geoscientists is predicted by 2022. Recruitment and training of a diverse workforce of geologists and related scientists is critical for national health, prosperity, welfare and defense. However, recruitment of underrepresented minorities into geosciences faces many obstacles. This project employs novel high-impact educational practices to increase the number and diversity of geoscience majors entering the geoscience career pipeline and trains K-12 teachers to inspire their students? interest in geosciences. Underrepresented students and pre-service teachers will engage in innovative marine geoscience experiences, mentoring programs, and courses using exciting technologies, career opportunity exposure, and hands-on learning. This project will target and recruit underrepresented students into geoscience majors at a private liberal arts university and a Minority (Hispanic-Serving) Institution that has a high percentage of rural, low-income, first-generation students who have very little exposure to marine science. We will evaluate the impact of engaging exposure to oceanography on the recruitment and retention of geoscience students and the preparation of K-12 teachers. Under the mentorship of research scientists, students will conduct authentic research, advancing our understanding of marine resources and environmental changes on the Pacific margin of the U.S. Part 2: The proposed project is an inter-institutional, co- and extra-curricular, participatory field-based oceanographic research program in collaboration with Scripps Institution of Oceanography (SIO) to train and inspire diverse students to pursue careers in the geosciences. This program will integrate students from a private urban coastal campus (University of San Diego; USD) with generally rural, minority, low-income students from a minority-serving public inland campus, California State Univ., Bakersfield (CSUB), with established ?geoscience career pipelines? to bring high-school students into geoscience majors and place graduates with geoscience employers. We intend to examine the idea that a multifaceted approach including integrated marine science experiences in the lab, at sea and in the classroom can enhance recruitment and retention of students in the geosciences. This project builds on a successful program of shipboard education/research developed by USD and Rathburn.

A US-led international effort, Overturning in the Subpolar North Atlantic Program (OSNAP), has provided a continuous record of the full-water column, trans-basin fluxes of heat, mass, and freshwater in the subpolar North Atlantic since 2014, in partnership with the UK, Netherlands, Canada and Germany. Results from the first four years of OSNAP observations have challenged the current understanding of overturning circulation in the subpolar North Atlantic. This grant provides funding for an additional four years of observations in order to deliver to the community a ten-year time series of the meridional overturning, heat and freshwater fluxes in the subpolar basin. Variations in these quantities have been invoked to explain changes in a wide range of physical, chemical and biological parameters in the North Atlantic, Nordic Seas, and Arctic Ocean. Thus, by quantifying Atlantic meridional overturning variability and understanding its drivers, OSNAP is providing a critical first step towards addressing societally-relevant, interdisciplinary questions concerning the melting of Greenland ice and Arctic sea-ice, heat content in the Arctic Ocean, climate of the Nordic Seas, and anthropogenic carbon storage.

These cruises utilize funding provided by the University of Minnesota. Chief Scientists will be completing seed research cruises or using their ship time to take graduate and undergraduate students on the research vessel Blue Heron.

Marine plankton form the base of most ocean food webs that support valuable fisheries. This highly diverse and complex community is composed of organisms that drift with ocean currents. Planktonic organisms remain understudied: they are difficult to sample given that their sizes span more than six orders of magnitude from less than one micron to meters. Yet, understanding how these communities will respond to climate change, and ultimately how these responses affect valuable fisheries, and therefore food security, is critical. Because many ecological and physiological processes are dictated by relative size, the theory of size spectra (i.e., the relationship between size and organism abundance as it drives ecosystem properties such as food webs) provides a valuable framework for forecasting climate change impacts on marine ecosystems. A deeper understanding of the scope and nature of variability in size spectra under contrasting environmental conditions is needed. The dynamic, highly productive northern California Current off Oregon and Washington in summer and winter seasons produce a patchwork of oceanographic conditions including those associated with hypoxia and ocean acidification. This study is sampling the plankton communities in this region to investigate how gradients of temperature, nutrients, dissolved oxygen, and pH conditions impact size spectra. The coupling of in situ plankton imagery and morphometric data allows quantifying scales of variation in plankton size spectra as well as testing predictions of how changes in environmental conditions (notably, temperature, nutrients, O 2 , pH) correlate with shifts in size spectra and revealing functional consequences to the food web. Plankton size spectra are being compared across environmental conditions by sampling in a habitat with steep environmental gradients and during two contrasting seasons. Planktonic organisms spanning 10 orders of magnitude in biomass are sampled using two complementary high-resolution imaging systems: the In Situ Ichthyoplankton Imaging System (ISIIS) and the Laser In-Situ Scattering and Transmissometry (LISST) particle imager. High-throughput image analysis software is used to generate size distributions together with taxonomic classification. Depth-discrete meso-zooplankton samples are collected in parallel to examine community shifts in carbon and for the calibration of length-to-carbon conversions based on images for use in normalized biomass size spectra. These plankton collections are also being analyzed for diet and reproductive status of gelatinous zooplankton, and diet and daily growth rate of representative larval fishes. These two groups have been historically understudied yet play central roles in ecosystem function. These data are adding to the understanding of how these important organisms at the base of the marine food web are affected by environmental conditions, and how they affect plankton size spectra. This study is foundational to the understanding of marine ecosystems within the context of climate change.

This research is one component of three interdependent and collaborative research efforts that together have an overarching primary goal of significantly improving the prediction of SONAR signal excess and its uncertainty for a required duration (e.g., 72 hours) for a given operational area. The primary long-term goal of this specific component (APL-Ocean Physics) is to improve the predictive modeling of hydrographic features that control acoustic transmission of mid-range frequencies. This three year effort will parallel and integrate with the proposed APL-Acoustics and NRL work. This effort will heavily leverage ongoing UW modeling efforts (LiveOcean), a host of ongoing observational assets on the Washington shelf, and existing ocean measurement tools. Our specific program objectives are to: 1) quantify the space and time scales of the acoustic ducts. 2) identify the mechanisms controlling the formation and evolution of these ducts. 3) apply new knowledge to improve key processes and inputs in models to more accurately reproduce and predict these ducts. 4) provide comprehensive field observations to ground truth models and provide critical environmental data for the acoustics field experiment, allowing detailed acoustic modeling. 5) via modeling investigate these phenomena in other operationally-significant regions.

Through this cruise aboard R/V Endeavor we aim to gather preliminary data in support of a collaborative National Science Foundation proposal that leverages the established North East Shelf Long Term Ecological Research site(NES-LTER), and leverage this historical data set to investigate marine food web structure and the flow of energy. Specifically, we will conduct combined growth and grazing experiments of different size classes of zooplankton (micro- and microzooplankton, < 200 µm and >200 µm, respectively) to uncover their relative grazing pressure on primary production, the occurrence of trophic cascades, and the potential for carbon export to higher trophic levels including forage fish. Our rate measurements will be paired with ship board characterization of particles with a particle size analyzer (Coulter Counter), flowcytometry, and FlowCam (an image-based plankton analyzer). At each station, water column variables including temperature, salinity, PAR will be measured in depth profiles. Discrete water samples for concentrations of nutrients and chlorophyll a will be captured with the CTD. In addition, MOCNESS tows will be done for the collection of larger zooplankton and water will be collected with the Niskins for incubation experiments using deck-board incubators. The methods and protocols are established and have been utilized on the R/V Endeavor. Thus, we think this is a straightforward cruise with a high likelihood of success. The results would enable us to seek follow on funding and ship time for work in the region on planktonic food webs that are fundamental to the ecological services provided. Importantly, these food webs are subject to to-date little known climate forcings and thus in urgent need of investigation.

he physical properties of the ocean from the surface layers to the abyssal water masses are changing in concert with natural and anthropogenically influenced physical forcing and sustained observations of the ocean are critically important to establish these rates of change. One of the longest open-ocean hydrographic stations in the world is maintained at the Hydrostation S site (formerly known as the Panulirus site) located about 25 km southeast of Bermuda in the North Atlantic Ocean. This repeat biweekly hydrographic observations was initiated by Henry Stommel and co-workers in 1954. Now, in its seventh decade, it continues to be recognized as one of the most important sustained ocean time-series and provides an invaluable metric for the long-term state of the North Atlantic subtropical gyre in relation to the meridional overturning circulation, western boundary transport, and gyre recirculation. For example, the upper ocean warming trend has strengthened (about 0.8° C since the 1970's) while the deep Labrador Sea has cooled by a few tenths of a degree. The signature of deoxygenation has been observed at Hydrostation S in the upper ocean (about 7 micro-moles/kg/decade decrease in dissolved oxygen) as well as an intensification and expansion of the oxygen minimum zone. These changes suggest that the North Atlantic subtropical gyre is experiencing deoxygenation as in the Pacific Ocean as a result of increased upper ocean stratification and reduced solubility of oxygen in warmer waters. The Hydrostation S program and its data set are managed as a service to the ocean community, being openly distributed and used as a resource in understanding processes and patterns of variability in the ocean, as well as for education, mentorship and outreach activities. The Hydrostation S project will contribute to the research and training of six research specialists and research technicians at BIOS and contribute to the research projects of at least three Ph.D. students through on-going educational partnership with Princeton University and the University of Southampton in the U.K. The one-day Hydrostation S research cruises are an ideal platform for testing new sensors and for providing hand-on training to undergraduate students enrolled in summer programs. The Hydrostation S project is designed to address the overarching hypothesis that the physical properties of the upper-ocean to deep-ocean are changing in concert with natural and anthropogenically influenced physical forcing. Sustained observations of the ocean, such as those from Hydrostation S, remain critically important to establish rates of change to provide quantitative empirical data for myriad regional and global ocean synthesis and modeling of ocean processes and future ocean change. The major objective of Hydrostation S into the seventh decade is to continue the frequent water column sampling of temperature, salinity, and dissolved oxygen (and indirectly, sampling of important ocean carbon time?series) of the North Atlantic subtropical gyre. Such work is complementary to other sustained observations such as the Bermuda Atlantic Time-series Study (BATS) and Ocean Flux Program (OFP). As for the past five years, two CTD profiles will be conducted to better capture the deep-water variability while maintaining all the previous discrete depths. The first CTD cast will profile to full ocean depth (3,200-3,500 m) while the second CTD cast will profile from the surface to 500 m to allow for biogeochemical instrumentation not rated for full ocean depth and to support ancillary studies of ocean physics, biological processes and biogeochemistry. A secondary objective will be to build upon the collaborative comparison of physical data collected as part of two autonomous sensor projects. In the latter stages of the project, as ocean glider deployment becomes more sustainable and reliable, collaborative and comparative efforts will be used to test the capability of ocean gliders to provide data of sufficient quality to detect long-term oceanic change in a "virtual" mooring time-series mode. The robust and highly accurate Hydrostation S data will be used to test the capability of emerging technologies over the next five to ten years.

Long-term observations over several decades are a powerful tool for investigating ocean physics, biology, and chemistry, and the response of the oceans to environmental change. The Bermuda Atlantic Time-Series Study, known as BATS, has been running continuously since 1988. The research goals of the BATS program are: (1) to improve our understanding of the time-varying components of the ocean carbon cycle and the cycles of related nutrient elements such as nitrogen, phosphorus, and silicon; and, (2) to identify the relevant physical, chemical and ecosystem properties responsible for this variability. In addition, the BATS program has strong and diverse broader impacts, contributing to the field of ocean sciences by providing high quality ocean observations and data for seagoing scientists and modelers, and a framework through which researchers can conceive and test hypotheses. This award will support the operations of the BATS program for five more years. The primary BATS research themes are as follows: (1) Quantify the role of ocean-atmosphere coupling and climate variability on air-sea exchange of CO2, and carbon export to the ocean interior; (2) Document trends and the controls on the interannual to decadal scale variability in carbon and nutrient cycles to their coupling in the surface and deep ocean via the Redfield Ratio paradigm; (3) Quantify the response of planktonic community structure and function, and impact on biogeochemical cycles to variability in surface fluxes and dynamical processes; (4) Facilitate development, calibration and validation of next generation oceanographic sensors, tools and technologies; and, (5) Generate a dataset that can be utilized by empiricists, modelers and students. This research integrates ocean physics, chemistry and biology into a framework for understanding oceanic processes and ocean change in the North Atlantic subtropical gyre. The existing 29 years of BATS data provide robust constraints on seasonal and interannual variability, the response of the Sargasso Sea ecosystem to natural climate variability, and signal detection of potential ocean changes. This project would extend the BATS program through years 31-35 to address a series of ten interlinked questions through integrated research approaches and a multitude of collaborative efforts. In addition to the themes above, and embedded into the ten questions and approaches, the BATS team will focus on, for example, coupling of particle production and biogeochemistry; revisiting the complexities of the biological carbon pump; oxygen decline; and changes in the hydrography, physics, ocean carbon cycle and biogeochemistry of the Sargasso Sea. The highest quality data observation and collection will be maintained and used to address these questions. Importantly, a wide range of collaborations at the BATS site, spanning the physical and biogeochemical disciplines, will aid these broad goals. Strong links to community stakeholders, and close collaboration (including methods intercomparisons and personnel exchanges) with the Hawaii Ocean Time-series are proposed. This work will extend the research findings of the project into educational and training opportunities within and beyond the oceanographic community, including training and mentorship of both undergraduate and graduate students.

The purpose of this collaborative project is to advance understanding of the role of marine planktonic animals (or zooplankton) in the biological pump, or transport of carbon from surface to deeper ocean waters. This movement of carbon from surface to deep ocean water can ultimately affect carbon dioxide in the atmosphere, with implications for global climate. Many marine zooplankton, including species of copepods and krill, play a direct role in the biological pump both because they are abundant and because they can migrate from surface waters at night, where they feed, to depths of more than 500 m at night. At the same time, some organisms called flux feeders will remain at depth and do not migrate. Instead, they rely on particles produced by other zooplankton feeding in surface waters. In this project, the investigators are focusing on populations of flux feeders in the deeper ocean waters of the Sargasso Sea. They are leveraging an ongoing long-term research program, conducting field collections using specialized nets and particle traps, as well lab experiments, as a way to understand how these organisms modify the particles around them. This project is supporting a postdoctoral scientist and providing research experiences for undergraduates at two institutions. An education specialist is creating lesson plans for an award-winning Ask-A-Biologist website, designed for public and K-12 audiences. Images of zooplankton will be disseminated to the public and scientific community via EcoTaxa (a web platform devoted to plankton biodiversity, with images and taxonomic annotation) and physical samples will be archived as part of a teaching library. The oceanic biological carbon pump refers to the export of dissolved and particulate organic carbon to the deep ocean, and it is a significant driver of atmospheric carbon uptake by the oceans. Evidence from long-term research carried out at the Bermuda Atlantic Time-series Study (BATS) site suggests that the spectrum of particles collected by gel-traps below the euphotic zone changes drastically below 150 m, which is attributed to resident populations of zooplankton that feed on vertically migrating zooplankton as well as sinking particles. The goals of this study are to investigate the role of different zooplankton taxa on both particle aggregate formation and in particle transformation, and to compare and characterize the particles generated by the zooplankton communities with those collected by particle traps. The investigators are combining field collections with experiments onboard ship and in environmental chambers. They are collecting samples over two years, with three cruises a year to capture distinct seasons. They are assessing high-resolution vertical distribution of zooplankton in the upper 600 m using Multiple Opening-Closing Net and Environmental Sensing System (MOCNESS) tows during day- and night-time, to distinguish diel vertical migrators from resident populations and to quantify contributions to particulate organic carbon flux via fecal pellet production. On each cruise, sinking particles are being collected using gel trap tubes attached to the particle traps deployed monthly at BATS. In addition, roller tank experiments are determining how individual zooplankton mediate aggregate formation. Particle types and fecal pellets are being characterized using image analysis and DNA-based analysis of microbial communities. Finally, ongoing data collection from the long-term BATS program is providing invaluable environmental context and will ensure results from this study contribute to ongoing community efforts to observe and predict the fate of carbon in our global system.

The Great Lakes hold about 20% of the freshwater on Earth and have been increasingly impacted by human activities in recent decades. Lake Erie suffers from large, annually recurring, toxic cyanobacterial blooms in summer, whereas Lake Superior experiences smaller, localized cyanobacterial blooms after storm events. Cyanobacterial blooms have harmful ecological, human health, and economic implications. These blooms are a global phenomenon, observed in lakes and oceans, and can lead to low oxygen conditions and the production of toxins, both of which can be harmful for ecosystems. Understanding how different types of cyanobacteria influence nutrient cycling remains a major knowledge gap. This project aims to provide a deeper understanding of the long-term state of the Great Lakes ecosystem. The research approach combines new and established methods. Project results and implications will be shared with local and regional water interests in partnership with the Pittsburgh Collaboratory for Water Research, Education, and Outreach, the Great Lakes Commission Harmful Algal Blooms Collaborative, and the Lake Erie Area Research Network. Education is a central part of this project and training opportunities target next generation of scientists, including postdoctoral, graduate, and undergraduate students. The students and postdoc will receive state-of-the-art training in the rapidly developing fields of biogeochemistry and geomicrobiology, while working with an interdisciplinary team of scientists.

Systematic long-term (greater than a few decades in length) time-series observations of aquatic and terrestrial environments have led to a more comprehensive understanding of the natural ecosystem variability and have enabled an assessment of human impacts on ecosystem dynamics. Because of their ability to store and transport large amounts of heat and to absorb carbon dioxide from the atmosphere, the world's oceans play a critical role in modulating environmental conditions for the sustained well-being of both land-based and marine organisms including humans. Despite their recognized scientific and societal importance, long-term records of key ocean processes are rare. In 1988, two ocean time-series programs were established: one in the North Atlantic near Bermuda and the other, the Hawaii Ocean Time-series (HOT) program, near Hawaii. For the past three decades, teams of scientists based at the University of Hawaii have made critical measurements of the 'state of our sea.' These long-term observations have established a baseline against which future states can be compared. The ship-based HOT program complements other diverse ocean observation programs including remote-sensing via satellites, moored buoys, profiling floats, and autonomous underwater vehicles. All HOT program data are publicly available and are frequently used by researchers and policy makers around the world.

Microorganisms are the ancestral forms of life on our planet and have been instrumental in shaping all of Earth?s environments into what they are today. In the ocean, microbial prokaryotes and eukaryotes form the foundation of marine food webs through their activity and interactions. Single-celled microbial eukaryotes (or protists) are some of the most important species on the planet, yet our understanding of how their activities influence and regulate the ocean ecosystem is poorly constrained. At deep-sea hydrothermal vents in particular, our understanding of microbial food web dynamics is incomplete without including the role of microbial eukaryotes. This project provides quantification of phagotrophic protistan grazing on the microbial communities inhabiting the highly productive diffuse vent mixing zone at hydrothermal vents, where the vent fluid-seawater interface promotes an increase in biological activity compared to the surrounding deep seawater. The results are contributing novel insights into the diversity and metabolic activities of the microbial eukaryotic community at vent fluid-seawater interfaces, establish the extent to which microbial eukaryotes impact primary production in the deep ocean by quantifying predation pressure, and estimate the amount of carbon transferred from primary producers to larger organisms.