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OC26 (R/V Oceanus Site 26) is one of three primary sites selected for study by the Ecosystem Impact of Oil and Gas Inputs to the Gulf (ECOGIG) consortium to determine the impacts of natural seepage versus large pulse inputs of hydrocarbons into the Gulf of Mexico (GOM) and to chart the long-term effects and mechanisms of ecosystem recovery from the Deep Water Horizon Oil Spill in 2010. OC26 is located on the western slope of the Gloria Dome, about five kilometers south-east of the Macondo wellhead. In 2011, the site was visited by the NOAA research vessel Okeanos Explorer. During this cruise, several natural oil/gas plumes originating from the seabed were identified. In order to establish precise locations for these naturally occurring sources of hydrocarbons and to inform biogeochemical and biological studies of the water-column, the seafloor, and the shallow subseafloor in the wake of the Deep Water Horizon spill, we conducted several Autonomous Underwater Vehicle (AUV) surveys. The surveys were designed to include swath bathymetry, chirp sub-bottom profiles, and seafloor still photos to augment the Okeanos Explorer and the 2012 ECOGIG Falkor multibeam bathymetric and water column data. These AUV high resolution datasets were collected to provide in-depth geophysical analyses of seafloor morphology and to link, where possible, morphological features to the subsurface structure and plumbing system at this site where natural seepage possibly intersects hydrocarbon inputs from the spill. The site exhibits many morphological seafloor features: depressions, elongated erosional structures, dome-shaped mud volcanoes/mounds, fault traces, and round pockmarks. Seabed photos show the presence of gas hydrate outcrops and benthic communities in the vicinity of maximum seafloor backscatter intensities and many of the morphological features. Subsurface profiles show gas-related anomalies (blanking and acoustic wipeout) where pockmarks, mud volcanoes/mounds and depressions are located. In addition to the discovery of novel seafloor features, these studies provide definitive links between seafloor seeps and particular morphologies and communities, contributing to the fundamental understanding of seeps in the deep sea.

Bottom nepheloid layers (BNLs) in the deep sea transport and remobilize considerable amounts of particulate matter, enhancing microbial cycling of organic matter in cold, deep water environments. We measured bacterial abundance, bacterial protein production, and activities of hydrolytic enzymes within and above a BNL that formed in the deep Mississippi Canyon, northern Gulf of Mexico, shortly after Hurricane Isaac had passed over the study area in late August 2012. The BNL was detected via beam attenuation in CTD casts over an area of at least 3.5 km 2 , extending up to 200 m above the seafloor at a water depth of ~1500 m. A large fraction of the suspended matter in the BNL consisted of resuspended sediments, as indicated by high levels of lithogenic material collected in near-bottom sediment traps shortly before the start of our sampling campaign. Observations of suspended particle abundance and sizes throughout the water column, using a combined camera-CTD system (marine snow camera, MSC), revealed the presence of macroaggregates (>1 mm in diameter) within the BNL, indicating resuspension of canyon sediments. A distinct bacterial response to enhanced particle concentrations within the BNL was evident from the observation that the highest enzymatic activities (peptidase, β-glucosidase) and protein production ( 3 H-leucine incorporation) were found within the most particle rich sections of the BNL. To investigate the effects of enhanced particle concentrations on bacterial activities in deep BNLs more directly, we conducted laboratory experiments with roller bottles filled with bottom water and amended with experimentally resuspended sediments from the study area. Macroaggregates formed within 1 day from resuspended sediments; by day 4 of the incubation bacterial cell numbers in treatments with resuspended sediments were more than twice as high as in those lacking sediment suspensions. Cell-specific enzymatic activities were also generally higher in the sediment-amended compared to the unamended treatments. The broader range and higher activities of polysaccharide hydrolases in the presence of resuspended sediments compared to the unamended water reflected enzymatic capabilities typical for benthic bacteria. Our data suggest that the formation of BNLs in the deep Gulf of Mexico can lead to transport of sedimentary organic matter into bottom waters, stimulating bacterial food web interactions. Such storm-induced resuspension may represent a possible mechanism for the redistribution of sedimented oil-fallout from the Deepwater Horizon spill in 2010.

The Ross Sea continental shelf is dominated by the seasonal appearance of a large phytoplankton bloom. This bloom is regularly dominated by diatoms and the haptophyte Phaeocystis antarctica, and significant nutrient (nitrogen and silicon) reductions within the water column occur during the growing season (early November to late February). Diatoms mediate silicic acid removal, whereas both taxa remove nitrate. Dissolved and particulate nitrogen and silica concentrations were collected from a series of cruises to the southern Ross Sea over 3 years. Simple, one-dimensional nutrient budgets were generated for nitrogen and silica, and estimates of vertical flux were derived from these budgets. Substantial variations among years are observed to occur in seasonal community production, assemblage composition, Si:N uptake ratios, and export, and standard deviations are equal to ∼30% of the mean. During 2003–2004 a large Phaeocystis antarctica bloom occurred in December, and was followed by a bloom of diatoms. This secondary bloom was equal in magnitude to that of the initial P. antarctica bloom. In contrast, no secondary bloom was observed in 2001–2002. Continuous fluorescence measurements suggested that the spatial–temporal mosaic of phytoplankton dynamics in the Ross Sea is far more complex than previously thought. We hypothesize that variations occur between years not only in terms of both magnitude and composition of the bloom, but also in the controlling mechanisms.

To understand marine biogeochemical cycles, it is critical to quantitatively balance organic matter transformations within the euphotic zone. Such an assessment for nitrogen is difficult because of lateral advection, uncertainties in individual measurements, the complexity of elemental transformations (including nitrification and denitrification), and the difficulty of collecting data on appropriate space and time scales. Two cruises were conducted to the southern Ross Sea, Antarctica, to understand the time-varying fluxes of nitrogen into its various pools. From these data a balanced inventory was constructed. Nitrate removal in the upper 200 m was balanced by particulate and dissolved organic nitrogen production, ammonification, and vertical flux. In austral spring nearly all (92%) of the new production remained as particulate nitrogen, but this percentage decreased markedly (52%) by mid-summer, when nitrogen regeneration, PN flux, and DON production were 23, 13 and 12% of net production, respectively. The organic matter budget in this coastal Antarctic site is dominated by particle transformations.

Applying improved processing techniques to increasingly high resolution data can produce extremely high resolution results that reveal features invisible on standard resolution images. Increasing demand for resources from the deep sea demands imaging the seabed in ever-more remote areas with increased accuracy. For economic, safety, and legal reasons, lessors of offshore real estate survey the seafloor and shallow sub-seafloor prior to conducting seafloor operations. A standard geohazards survey includes multibeam bathymetry, side-scan sonar and CHIRP subbottom profiling and will yield useful data at 5-25 m (16-82 ft) resolution. However, higher resolution surveys are now possible and, though more time-consuming (and costly), yield potentially critical information not visible in coarser resolution surveys: morphologic features, structure, biota, etc. Recovering such information has become increasingly important for reasons that include 1) identification of natural seafloor features (i.e., fault traces, protected seafloor communities, seeps, mud volcanoes); 2) selection/elimination of target locations; 3) identification of unnatural features (shipwrecks, instruments, pipelines); 4) siting structures on the seafloor; and 5) instrument location/recovery. Using coarser resolution surveying for regional studies, then focusing higher resolution surveys on areas of particular interest, and applying meticulous processing of acoustic data, our team has produced 1 m (3 ft) resolution seafloor images that have enabled us to identify a host of small-scale features not routinely imaged at coarser resolutions. Here we present significant results including small-scale morphologic features associated with seeps, instrument locations, and benthic fauna habitat in the Gulf of Mexico.

The large marine snow formation event observed in oil-contaminated surface waters of the Gulf of Mexico (GoM) after the Deepwater Horizon accident possibly played a key role in the fate of the surface oil. We characterized the unusually large and mucus-rich marine snow that formed and conducted roller table experiments to investigate their formation mechanisms. Once marine snow lost its buoyancy, its sinking velocity, porosity and excess density were then similar to those of diatom or miscellaneous aggregates. The hydrated density of the component particles of the marine snow from the GoM was remarkably variable, suggesting a wide variety of component types. Our experiments suggest that the marine snow appearing at the surface after the oil spill was formed through the interaction of three mechanisms: (1) production of mucous webs through the activities of bacterial oil-degraders associated with the floating oil layer; (2) production of oily particulate matter through interactions of oil components with suspended matter and their coagulation; and (3) coagulation of phytoplankton with oil droplets incorporated into aggregates. Marine snow formed in some, but not all, experiments with water from the subsurface plume of dissolved hydrocarbons, emphasizing the complexity of the conditions leading to the formation of marine snow in oil-contaminated seawater at depth.

Seasonal patterns in hydrography, oxygen, nutrients, particulate carbon and nitrogen and pigments were measured on monthly cruises at the Bermuda Atlantic Time-series Study site, 80 km southeast of Bermuda. Between October 1988 and September 1990, the annual cycle was defined by the creation of 160–230 m-deep mixed layers in February of each year and a transition to strong thermal stratification in summer and fall. The 230 m mixed layer in February 1989 resulted in mixed-layer nitrate concentrations of 0.5–1.0 μmole kg−1, carbon fixation rates over 800 mg C m−2 day−1, and a phytoplankton bloom with chlorophyll concentrations over 0.4 mg m−3. Chlorophyll a, particulate organic matter, inorganic nutrients and primary production had returned to prebloom levels the following month with the exception of a chlorophyll maximum layer at 100 m. Particle fluxes at 150 m in February 1989 reached 56 mg C m−2 day−1 and 11 mg N m−2 day−1 (0.77 mmole N m−2 day−1). Estimates of new production during the bloom period calculated from changes in oxygen and nitrate profiles ranged from 100 to 240 mmoles N m−2, significantly higher than the sediment trap fluxes and approaching the measured total production rates. In spring of 1990, mixed layer depths did not exceed 160 m, nitrate was rarely detectable in the upper euphotic zone, chlorophyll a concentrations were similar to 1989, and particulate organic matter concentrations were lower. The period of elevated biomass lasted for 3 months in 1990, and phytoplankton pigment composition varied between cruises. The average rates of primary production and particle flux were higher in 1990 than those measured in the spring of 1989, despite the differences in mixed layer depth. Throughout both years, NO3 : PO4 ratios in the upper thermocline exceeded Redfield ratios. The maintenance of this pattern requires a net uptake of PO4 between 150 and 250 m, a depth range usually associated with net remineralization. The exact mechanism that maintains elevated PO4 uptake and its implication for the nutrient supply to the euphotic zone remain unknown.

The Gulf of Mexico Hydrates Research Consortium (GOM-HRC) was established in 1999 to assemble leaders in gas hydrates research that shared the need for a way to conduct investigations of gas hydrates and their stability zone in the Gulf of Mexico in situ on a more-or-less continuous basis. The primary objective of the group is to design and emplace a remote monitoring station or sea floor observatory (SFO) on the sea floor in the northern Gulf of Mexico, in an area where gas hydrates are known to be present at, or just below, the sea floor and to discover the configuration and composition of the subsurface pathways or 'plumbing' through which fluids migrate into and out of the hydrate stability zone (HSZ) to the sediment-water interface. Monitoring changes in this zone and linking them to coincident and perhaps consequent events at the seafloor and within the water column is the eventual goal of the Consortium. This mission includes investigations of the physical, chemical and biological components of the gas hydrate stability zone - the sea-floor/sediment-water interface, the near-sea-floor water column, and the shallow subsurface sediments. The eventual goal is to monitor changes in the hydrate stability zone over time. Establishment of the Consortium succeeded in fulfilling the critical need to coordinate activities, avoid redundancies and communicate effectively among those involved in gas hydrates research. Complementary expertise, both scientific and technical, has been assembled to promote innovative methods and construct necessary instrumentation. Following extensive investigation into candidate sites, Mississippi Canyon 118 (MC118) was chosen by consensus of the Consortium at their fall, 2004, meeting as the site most likely to satisfy all criteria established by the group. Much of the preliminary work preceding the establishment of the site - sensor development and testing, geophysical surveys, and laboratory studies - has been reported in agency documents including the Final Technical Report to DOE covering Cooperative Agreement DEFC26-00NT40920 and Semiannual Progress Reports for this award, DE-FC26-02NT41628. Initial components of the observatory, a probe that collects pore-fluid samples and another that records sea floor temperatures, were deployed in MC118 in May of 2005. Follow-up deployments, planned for fall 2005, had to be postponed due to the catastrophic effects of Hurricane Katrina (and later, Rita) on the Gulf Coast. SFO completion, now anticipated for 2009-10, has, therefore, been delayed. Although delays caused scheduling and deployment difficulties, many sensors and instruments were completed during this period. Software has been written that will accommodate the data that the station retrieves, when it begins to be delivered. In addition, new seismic data processing software has been written to treat the peculiar data to be received by the vertical line array (VLA) and additional software has been developed that will address the horizontal line array (HLA) data. These packages have been tested on data from the test deployments of the VLA and on data from other, similar, areas of the Gulf (in the case of the HLA software). During the life of this Cooperative Agreement (CA), the CMRET conducted many cruises. Early in the program these were executed primarily to survey potential sites and test sensors and equipment being developed for the SFO. When MC118 was established as the observatory site, subsequent cruises focused on this location. Beginning in 2005 and continuing to the present, 13 research cruises to MC118 have been conducted by the Consortium. During September, 2006, the Consortium was able to secure 8 days aboard the R/V Seward Johnson with submersible Johnson SeaLink, a critical chapter in the life of the Observatory project as important documentation, tests, recoveries and deployments were accomplished during this trip (log appended). Consortium members have participated materially in a number of additional cruises including several of the NIUST autonomous underwater vehicle (AUV), Eagle Ray. Activities reports summarize cruise activities, including objectives, how they were met or not met, and challenges. Deployment cruises are scheduled for 2009 that are designed to complete installation of the major observatory components.

A Consortium, designed to assemble leaders in gas hydrates research, has been established at the University of Mississippi's Center for Marine Resources and Environmental Technology, CMRET. The primary objective of the group is to design and emplace a remote monitoring station on the sea floor in the northern Gulf of Mexico by the year 2005, in an area where gas hydrates are known to be present at, or just below, the sea floor. This mission necessitates assembling a station that will monitor physical and chemical parameters of the sea water and sea floor sediments on a more-or-less continuous basis over an extended period of time. Development of the station allows for the possibility of expanding its capabilities to include biological monitoring, as a means of assessing environmental health. Establishment of the Consortium has succeeded in fulfilling the critical need to coordinate activities, avoid redundancies and communicate effectively among researchers in this relatively new research arena. Complementary expertise, both scientific and technical, has been assembled to promote innovative research methods and construct necessary instrumentation. Noteworthy achievements six months into the extended life of this cooperative agreement include: (1) Progress on the vertical line array (VLA) of sensors: Analysis and repair attempts of the VLA used in the deep water deployment during October 2003 have been completed; Definition of an interface protocol for the VLA DATS to the SFO has been established; Design modifications to allow integration of the VLA to the SFO have been made; Experience gained in the deployments of the first VLA is being applied to the design of the next VLAs; One of the two planned new VLAs being modified to serve as an Oceanographic Line Array (OLA). (2) Progress on the Sea Floor Probe: The decision to replace the Sea Floor Probe technology with the borehole emplacement of a geophysical array was reversed due to the 1300m water depth at the JIP selected borehole site. The SFP concept has been revisited as a deployment technique for the subsea floor array; The SFP has been redesigned to include gravity driven emplacement of an array up to 10m into the shallow subsurface of the sea floor. (3) Progress on the Acoustic Systems for Monitoring Gas Hydrates: Video recordings of bubbles emitted from a seep in Mississippi Canyon have been analyzed for effects of currents and temperature changes; Several acoustic monitoring system concepts have been evaluated for their appropriateness to MC118, i.e., on the deep sea floor; A mock-up system was built but was rejected as too impractical for deployment on the sea floor. (4) Progress on the Electromagnetic Bubble Detector and Counter: The initial Inductive Conductivity Cell has been constructed from components acquired during the previous reporting period; Laboratory tests involving measuring bubble volume as a component of conductivity have been performed; The laboratory tests were performed in a closed system, under controlled conditions; the relationship between voltage and bubble volume appears to be linear. (5) Progress on the Mid-Infrared Sensor for Continuous Methane Monitoring: Designs and construction schematics for all electronic mounting pieces and an electronics system baseplate were finalized after extensive modeling to facilitate the successful fabrication and implementation of electronic components into the deep-sea, glass instrument housing; Construction schematics and fabrication of an electronics system baseplate have been completed with successful integration of all currently fabricated electronic mounting pieces; Modeling and design of an optics platform complementary to the constructed electronics platform for successful incorporation into ''sphereIR'' has commenced; A second generation chemometric data evaluation software package for evaluating complex spectra including corrections for baseline drifts and spectral anomalies resulting from matrix substances has been developed and will be incorporated into an optimized ''deepSniff'' program upon completion of initial systems tests of the ''sphereIR''; Continuation of spectroscopic investigations of the highly permeable polymer, poly(trimethylsilyl)propyne (PTMSP), as a potential sensing membrane for methane have continued and will continue in the following project period.; High-pressure multireflection ATR measurements simulating deep-sea conditions for evaluating environmental impact on the sensor system and multivariate data analysis continue. (6) Progress on the Seismo-acoustic Characterization of Sea Floor Properties and Processes at the Hydrate Monitoring Station: Work has continued on developing the electronic part of the acoustic logging system designed for investigating fine-scale temporal changes in sea floor acoustic reflection responses at the Gas Hydrate Monitoring Station; The hardware has been built and extensively tested.

Conducting Antarctic research is challenging. Not only is the environment difficult, given low temperatures, high winds, and ice cover, but also the availability of sampling platforms is limited. The U.S. National Science Foundation has only two vessels that can routinely operate in ice-covered waters, the research vessel/icebreaker N.B. Palmer and the Antarctic research support vessel L.M. Gould. The restricted availability of vessels makes research operations difficult to schedule, especially during austral spring and summer. Traditional sampling methods (those confined to ships and moorings) have provided insights into distributions and processes in the Southern Ocean, but new research questions require new sampling means.