Ecological insights into abyssal bentho-pelagic fish at 4000 m depth using a multi-beam echosounder on a remotely operated vehicle

Ecological and behavioral data on mobile, low density, benthopelagic animals is difficult to collect in the abyssal environment. However, these species occupy an important position in the abyssal food chain. At-depth ROV-mounted echosounder studies provide a powerful tool to gather in-situ information on abyssal benthopelagic assemblages and discern their distribution, behavior and habitat associations. This study presents a new perspective on mobile benthopelagic assemblages at the long-term study site, Station M (∼4000 m), using a Seabat T20-S MBES mounted on the ROV Doc Ricketts. The targets (∼45 m off the seafloor) are believed to be the abyssal grenadier of the species Coryphaenoides armatus or C. yaquinae, species known to dominate the mobile benthopelagic fauna at Station M. The swimming behavior of the targets indicated little evidence of avoidance or attraction to the slowly moving ROV and demonstrates the effectiveness of this platform to collect data on benthopelagic fish. The information on targets in close (<1 m) association with the seafloor from the MBES corresponded well to target densities recorded by the video transects. However, in addition the MBES resolved the distribution of targets up to 45 m above the seafloor. Target density had a small peak close to the seafloor (<1 m) but increased in density with height above the seafloor, exceeding the maximum near-bottom density by ∼50 times. ROV-mounted MBES surveys can effectively provide data on the distribution and behavior of benthopelagic fish and further understanding of the pelagic-benthic links in the abyssal deep-sea.acceptedVersio

Value of early postoperative epicardial programmed ventricular stimulation studies after surgery for ventricular tachyarrhythmias

The value of early postoperative epicardial programmed ventricular stimulation studies after electrophysiologically-directed surgery for ventricular tachyarrhythmia was assessed in 34 patients who underwent epicardial stimulation within 7 to 30 days (mean 9.8) of surgery and were followed up for at least 6 months. The antiarrhythmic operation performed was an endocardial ventriculotomy (full encircling or limited), an endocardial resection, a wall resection or a combination of these procedures. All these interventions were directed by intraoperative mapping during sinus rhythm. Temporary epicardial wire electrodes left at the time of surgery rather than endocardial catheter electrodes were used to perform the pacing. The stimulation protocol included the introduction of up to three ventricular extrastimuli and incremental burst ventricular pacing performed at twice diastolic threshold (9.2 ± 5.8 mA for the right ventricle and 6.0 ± 3.5 mA for the left ventricle). A study was considered positive when ventricular tachycardia, defined as 10 or more consecutive ventricular beats, was induced by any pacing modality.Nineteen patients (Group I) had a negative study: after stimulation of both ventricles in 15 patients and of the left ventricle only in 4. Fifteen patients (Group II) had a positive study: after stimulation of the right ventricle in nine patients and of the left ventricle in six. The two groups were comparable with respect to preoperative clinical status, surgical procedures performed and postoperative ejection fraction. No arrhythmic events were observed in Group I during a mean follow-up period of 19.5 months (range 4 to 37), whereas seven arrhythmic events (47% incidence) occurred (p = 0.0008) in Group II during a mean follow-up period of 17.7 months (range 5 to 39). These arrhythmic events were sudden death (five patients) and sustained ventricular tachycardia (two patients).It is concluded that temporary epicardially-placed electrodes can be used satisfactorily to perform programmed ventricular stimulation studies in the postoperative period, thereby avoiding the cardiac catheterizations otherwise necessary to perform these studies. In addition, the protocol used in this report of epicardial programmed ventricular stimulation early after surgery for ventricular tachyarrhythmia predicts a good outcome if the study is negative and identifies patients at a high risk for future arrhythmic events when positive

Development and deployment of a precision underwater positioning system for in situ laser Raman spectroscopy in the deep ocean

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 52 (2005): 2376-2389, doi:10.1016/j.dsr.2005.09.002.The field of ocean geochemistry has recently been expanded to include in situ laser Raman spectroscopic measurements in the deep ocean. While this technique has proved to be successful for transparent targets, such as fluids and gases, difficulty exists in using deep submergence vehicle manipulators to position and control the very small laser spot with respect to opaque samples of interest, such as many rocks, minerals, bacterial mats, and seafloor gas hydrates. We have developed, tested, and successfully deployed by remotely operated vehicle (ROV) a precision underwater positioner (PUP) which provides the stability and precision movement required to perform spectroscopic measurements using the Deep Ocean In Situ Spectrometer (DORISS) instrument on opaque targets in the deep ocean for geochemical research. The positioner is also adaptable to other sensors, such as electrodes, which require precise control and positioning on the seafloor. PUP is capable of translating the DORISS optical head with a precision of 0.1 mm in three dimensions over a range of at least 15 cm, at depths up to 4000 m, and under the normal range of oceanic conditions (T, P, current velocity). The positioner is controlled, and spectra are obtained, in real time via Ethernet by scientists aboard the surface vessel. This capability has allowed us to acquire high quality Raman spectra of targets such as rocks, shells, and gas hydrates on the seafloor, including the ability to scan the laser spot across a rock surface in sub-millimeter increments to identify the constituent mineral grains. These developments have greatly enhanced the ability to obtain in situ Raman spectra on the seafloor from an enormous range of specimens.Funding was provided by a grant to MBARI from the David and Lucile Packard Foundation

Ecological insights into abyssal bentho-pelagic fish at 4000 m depth using a multi-beam echosounder on a remotely operated vehicle

Ecological and behavioral data on mobile, low density, benthopelagic animals is difficult to collect in the abyssal environment. However, these species occupy an important position in the abyssal food chain. At-depth ROV-mounted echosounder studies provide a powerful tool to gather in-situ information on abyssal benthopelagic assemblages and discern their distribution, behavior and habitat associations. This study presents a new perspective on mobile benthopelagic assemblages at the long-term study site, Station M (∼4000 m), using a Seabat T20-S MBES mounted on the ROV Doc Ricketts. The targets (∼45 m off the seafloor) are believed to be the abyssal grenadier of the species Coryphaenoides armatus or C. yaquinae, species known to dominate the mobile benthopelagic fauna at Station M. The swimming behavior of the targets indicated little evidence of avoidance or attraction to the slowly moving ROV and demonstrates the effectiveness of this platform to collect data on benthopelagic fish. The information on targets in close (<1 m) association with the seafloor from the MBES corresponded well to target densities recorded by the video transects. However, in addition the MBES resolved the distribution of targets up to 45 m above the seafloor. Target density had a small peak close to the seafloor (<1 m) but increased in density with height above the seafloor, exceeding the maximum near-bottom density by ∼50 times. ROV-mounted MBES surveys can effectively provide data on the distribution and behavior of benthopelagic fish and further understanding of the pelagic-benthic links in the abyssal deep-sea

An evaluation of deep-sea benthic megafauna length measurements obtained with laser and stereo camera methods

The 25 year time-series collected at Station M, ~4000 m on the Monterey Deep-sea Fan, has substantially improved understanding of the role of the deep-ocean benthic environment in the global carbon cycle. However, the role of deep-ocean benthic megafauna in carbon bioturbation, remineralization and sequestration is relatively unknown. It is important to gather both accurate and precise measurements of megafaunal community abundance, size distribution and biomass to further define their role in deep-sea carbon cycling and possible sequestration. This study describes initial results from a stereo camera system attached to a remotely operated vehicle and analyzed using the EventMeasure photogrammetric measurement software to estimate the density, length and biomass of 10 species of mobile epibenthic megafauna. Stereo length estimates were compared to those from a single video camera system equipped with sizing lasers and analyzed using the Monterey Bay Aquarium Research Institute’s Video Annotation and Reference System. Both camera systems and software were capable of high measurement accuracy and precision (&lt;±1 mm measurement error and precision). However, the oblique angle of the single video camera caused the spatial scale of the image perspective to change with distance from the camera, resulting in error when measurements were not parallel or vertical to two horizontal-oriented scaling lasers. Analysis showed that the stereo system recorded longer lengths and higher biomass estimates than the single video camera system for the majority of the 10 megafauna species studied. The stereo image analysis process took substantially longer than the video analysis and the value of the EventMeasure software tool would be improved with developments in analysis automation. The stereo system is less influenced by object orientation and height, and is potentially a useful tool to be mounted on an autonomous underwater vehicle and for measuring deep-sea pelagic animals where the use of lasers is not feasible

Influence of disturbance on sedimentary carbon stocks in a temperate seabed

Shelf sea sediments are natural, long-term carbon sinks that may be managed for Blue Carbon (BC) storage to offset greenhouse gas emissions and contribute to nations ‘Net Zero’ ambitions. The Isle of Man in the Irish Sea has territorial waters equivalent to approximately 85% of its total jurisdiction, and significant potential for BC offsetting through seabed management. The Island’s Government is developing a comprehensive BC management plan to maximise carbon sequestration and restore seabed biodiversity and wider ecosystem services. We determined the effects of disturbance on sedimentary carbon stocks and accumulation rates in the western territorial sea, a region of mud-dominated sediment with elevated disturbance from Nephrops norvegicus bioturbation and bottom-contact fishing activities. Sediment cores were collected from approximately 5 to 12 nautical miles off the west coast of the Isle of Man, at depths from 60 m to 120 m. The cores were sectioned and analysed using: elemental analysis and isotope ratio mass spectrometry to quantify organic and inorganic carbon stocks; and gamma-ray spectrometry and alpha spectrometry to identify and quantify radionuclides of Cs-137, Pb-210, Am-241 and Po-210 to determine sedimentation rates. Complete sediment cores were scanned using X-ray to generate radiographs and laminographs, to determine internal core structure and identify N. norvegicus burrows. The results show that organic/inorganic carbon and sedimentation rates in offshore sediments vary over time and space. Analysis is ongoing to ascertain if these variations are related to disturbance of the sedimentary system, using indicators of fishing intensities and N. norvegicus bioturbation. Results of this analysis will be presented to elucidate the effects of disturbance on sedimentary carbon stocks and accumulation