Doing research in Antarctica presents some extra challenges that normal lab work does not. This problem is especially acute during Austral winter, but even during the summer months, having a set of "eyes" on the Antarctic seafloor 24-7 will significantly enhance research on the organisms that live there.
Enter the ROMEO project. The name stands for "Remotely Operable Underwater Micro-environmental Observatory", and the goal is to develop a tool for observing small organisms like foraminiferans in their natural environment, all year round. This project is supported by the National Science Foundation (OPP 0216043, PI Samuel S. Bowser, Co-PI Tony Hansen.)
Progress report, 2003 calendar year
Progress report, 2004 calendar year
Progress Report for 2003 Calendar Year
Our project seeks to develop a remotely operable underwater micro-environmental observatory (“ROMEO”). The primary objectives over the past year were (1) to select a camera with macro capabilities, (2) build an underwater enclosure, and (3) test communications via the Internet to a remote operator at a home institution. We also aimed to measure underwater light levels so that we can build appropriate illuminators to provide photosynthetically-equivalent irradiation during the dark winter months, thus enabling studies of the importance of algal photoproduction in foraminiferal dynamics. A final aim was to characterize the site selected for placement of the datalink from the underwater instrument package to a shore-based communications station. This will enable scientific observations to be conducted year-round without the challenges, risks and expenses of attempting diving operations in the Antarctic winter.
Instrument development: The initial ROMEO instrument (“Alpha”) has been constructed (Fig. 1) and was field-tested in November 2003. The unit currently comprises a steerable web camera, image storage hardware, and battery module.
Fig. 1: A schematic of the ROMEO housing with battery
pack (left) and photograph of the camera and undercarriage (right).
Camera resolution: A resolution test of the camera is shown in Fig. 2.
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| Fig 2. Resolution test of the ROMEO camera. A carabiner gate was photographed on the surface using a Zeiss stereomicroscope, and then imaged on the seafloor by the ROMEO camera (inset) |
We compared light micrographs of the machined features on a carabiner gate with images of the same carabiner obtained by the ROMEO camera while submerged. From these comparative studies, we conservatively estimate that the camera is capable of at least 500 μm resolution using the limited ambient light (see comments on light levels, below) and no auxiliary lenses. We rate this as excellent camera performance. A major goal of the next stage of development will be the introduction of an illumination system, and the testing of accessory lenses (e.g., a 10x diopter).
Underwater light levels: There was considerable snow
cover at Explorers Cove during the testing period, and the multi-year
ice contained substantial amounts of wind-blown sediment. As a result,
ambient light levels were low -- so low, in fact, that divers required
the use of lights, which is quite unusual at this locality.
Quantifying summer light levels at Explorers Cove (and elsewhere in McMurdo
Sound) is critical to our project for several reasons. First, with accurate
irradiance measurements, we can select appropriate detectors for our camera.
An equally important consideration is the selection of appropriate artificial
lighting. One additional goal of our project is to experimentally simulate
summer light levels during the austral winter, thus damping primary production
seasonality; we will monitor the resulting response of meio- and megafauna
within experimentally illuminated vs. control (ambient light) and experimentally
shaded plots. To begin characterizing ambient light levels, we measured
the photosynthetic photon flux fluence rate (PPFFR) using a Li-cor 193SA
Spherical Quantum Sensor. Subsurface PAR irradiance values were approximately
four orders of magnitude lower than surface values. At the primary site,
surface PAR ranged from 1375 to 1491 μmol s-1m-2,
while the concomitant seafloor (23 meters depth) value was 0.1492 μmol
s-1m-2.
At an alternate site, surface values ranged from 1328 to 1492 μmol
s-1m-2,
whereas seafloor value (27 meter depth) was 0.2054 μmol s-1m-2.
Continuous measurements are currently being made in front of McMurdo Station,
where qualitatively similar situations exist (snow-covered, multi-year
ice). We will record PPFFR for the entire summer season next year in final
preparation for the subsequent year-long study.
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| Fig 3. Views of the seafloor at Explorers Cove, in near proximity to the ROMEO instrument. Several live scallops (Adamussium colbecki) and an associated desmosponge (Homaxinella balfourensis) are seen. Note small scale topographic features and differential texture (esp. the patchy distribution of coarse sand) of sediment. Inset: Even at the far range of the camera (estimated to be ~600 feet), numerous scallops, bryozoans, and fan worm tubes are discernable. |
General instrument performance: Despite low ambient
light levels, the originally-equipped ROMEO camera performed well. An
overview of the seafloor is given in Figure 3, which shows dozens of scallops
(Adamussium colbecki) extending to the horizon. The instrument will therefore
be able to accomplish one major project goal, namely to determine the
rate at which scallops vent, which in turn will yield important insight
into bioturbation and resuspension of organic matter in the Cove.
With respect to the primary goal of this project, our most significant
accomplishment was the successful imaging of foraminfera in situ. In figure
4, Cibicides refulgens, a smaller calcareous foraminiferan, is
seen adorning the upper valve of
Adamussium colbecki. This epizoic foraminifer employs two major
trophic modes: grazing algae (diatoms) off the valve surface, and parasitically
by boring through the pecten's shell to aquire nutrients from the extrapallial
fluid. The ability to image Cibicides directly will permit us
to study in situ motility, reproductive events, recruitment, and growth.
(Comparable information will be gleaned for other epibionts, such as the
turbellid polychaete Leaena.) Also seen in this figure are examples
of arborescent epibionts, some of which are identified as members of the
notodendrodid foraminifera. Such "tree forams" are a major target
for our studies, because they are conspicuous members of the basal radiation
of foraminifera we estimate to have occurred >800 MA (see Pawlowski,
J., Holzmann, M., Berney, C., Fahrni, J., Gooday, A.J., Cedhagen, T.,
Habura, A., Bowser, S.S., Evolution of early Foraminifera. Proceedings
of the National Academy of Sciences, USA 100:11494-11498, 2003). Our initial
lipid biomarker studies of such notodendrodids indicate that they may
be carnivors. Direct observation of carnivory in situ, and determination
of its rate of occurrence in these species, will greatly improve our interpretation
of Neoproterozoic ecosystems.
Fig. 4. Detail of foraminiferans associated with scallop
valves, as revealed by ROMEO's camera.
Datalink placement: A final (and perhaps most important) accomplishment was the characterization of the moat ice, transition, and ice foot at the "Ice Cliff" site along the northwest shore of Explorers Cove. This is where the conduit containing power and optical data cables will be placed, thus linking the ROMEO instrument package to the on-shore data transmission station. Figure 5 is a schematic of our findings. Most significantly, we found an approximately 12-18 inch layer of silt-laden ice approximately 8 ft. below the moat ice surface. This “dirty ice” layer poses significant problems for the placement of the conduit, especially using approaches that employ ice melting.
Fig. 5. Characterization of moat ice and ice foot at the ROMEO study site (not drawn to scale). A layer of fine silt was detected at various depths (in inches) along the moat ice. At point "A" near the transition zone, e.g., drilling revealed this layer to begin at 126" (10.5 feet), followed by clean ice within the ice foot. Similar conditions were encountered moving toward shore to point "E," whereafter coarser sand (with grain size distributions similar to the shore sand) subtended the moat ice. Distance between points is 15 ft.
For example, our initial plan was to deploy the conduit late in the season after the moat has melted, laying the conduit along the moat sediment and using heat tape wrapping to melt the conduit through the ice foot. In our characterization work this season, however, this sediment layer was found to absorb much of the heat that was generated by a robust “Hotsie”-based ice melting coil (Figure 6). Based on this experience, it is clear that a heat-tape-wrapped conduit would not cut through this layer. We strongly recommend that ICDS help develop and/or execute a plan for drilling through this “dirty ice” layer to deploy the conduit. Several alternative solutions have been discussed with Michael Gerasimoff (ICDS Mechanical Engineer) and RPSC staff.
Fig. 6. “Hotsie” hole melted at “Point A” in Figure 5. The hot finger ripped through 10+ ft of moat ice within 12 hrs, but stalled upon reaching the silt/ice layer (seen as the dark mass at the bottom of the melthole). Two days of subsequent attempts to melt through this relatively thin layer failed, despite the fact that drilling easily penetrated it. A Boy Scout is shown toiling to remove the sediment/meltwater slurry from the melthole.
Progress Report for 2004 Calendar Year
Summary
In the first year of the project (2003/2004 field season), the ROMEO camera was tested underwater for imaging resolution and low-light-level operation. In this second year of the project (2004/2005 field season), a 1-inch diameter, stainless steel conduit was installed from the shore to the underwater ROMEO site to house primary and backup fiber-optic and power cables. This conduit reduces the danger of cable breakage due to movement of the sea ice. ROMEO was placed on the seafloor at a water depth of approximately 75 feet, in an area populated by scallops harboring epibiotic foraminifera. For optical testing, a ‘target’ scallop was tethered to a PVC frame directly beneath the camera. This scallop was imaged from early November 2004 to late January 2005, whereupon the ROMEO unit was retrieved and serviced, its images were downloaded, and a new tethered scallop was deployed. Our plan is to leave it in place until October 2005 to acquire time-lapse images of the interaction of foraminifera with scallop hosts. During the third year of the project (2005/2006 field season) we will connect the ‘land’ terminal of the cable via a radio link to McMurdo, established by RPSC, allowing remote uploading of data and camera re-targeting (if required) via the Internet. During this final phase of testing, various test objects will be deployed near ROMEO and monitored over-winter.
2004/2005 New Harbor Logistics
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| Leak testing ROMEO through a dive hole at McMurdo. |
Two camera units and connecting cables were shipped to McMurdo for this
season’s work. All equipment arrived safely and on time. We fabricated
a 500-foot shore-to-seafloor link, consisting of two parallel fiber-optic
cables and a 5-conductor electrical cable. We also brought two 500-foot
spools of fiber-optic cable for additional trials. The dome enclosure
was tested for leak integrity by immersion to 100 feet depth from a dive
hole at McMurdo (left).
The conduit was constructed at New Harbor by cutting a 75-foot long trench
into the sea ice to a depth of approximately 5 feet, starting at the shoreline.
In the vertical wall at the end of this trench, a conduit of 1-inch stainless-steel
pipe was drilled down at an angle of approximately 20º by hot water,
using equipment
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| Conduit installation at Ice Cliff site, Explorers Cove. Mount Coleman is in the background. |
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| A diver feeds cable through conduit penetrating the Explorers Cove ice cliff. |
Upon installation, the cable was tested for end-to-end integrity. The camera was then attached and lowered to the sea floor. Divers used an airlift bag to relocate ROMEO approximately 80 feet east of the dive hole, at a water depth of approximately 75 feet. At the surface, a live ‘target’ scallop was tethered to a PVC frame using fishing line and was then lowered to the seafloor. The specimen frame was positioned directly under the camera anchored in the sediment. The Adamussium was illuminated by LED lamps powered from a 12-volt lead acid battery situated on shore; the ROMEO camera was powered by onboard batteries. Even under conditions of very low light, the camera aperture could be held open for a sufficiently long integrating time to obtain low-speed live video and monochrome still pictures (below, left). With illumination provided by the LED lamps, color images were obtained (below, right).
Initial findings
The ROMEO camera was programmed to record 3888 images (totaling approximately 815 MB) from 16 pre-selected areas of the dorsal Adamussium valve. These areas included several high-magnification views of a juvenile Adamussium and numerous Cibicides refulgens living parasitically on the scallop. The camera was then directed to enter hibernation mode for 6 hours, after which time the system repeated this cycle. In total, sequences were obtained from 11/10/04 to 01/02/05. As a test of the power cabling and battery, the LED lamps were left "on" during this period, with the camera set for aperture priority. Approximately 14 days into the experiment, a sea star (Diplasterias brucei) attacked the scallop and consumed it (Figs. C-I, below). The juvenile scallop (arrowhead, B) was detached and presumably consumed as well. The rigors of this attack resulted in gross repositioning of the scallop (cf. B, H, below), so that the initial higher-magnification image fields of Cibicides were no longer within the field of view. Such unanticipated occurrences highlight the absolute requirement for remote accessibility and operation of the camera via the internet. Once the unit is connected to the internet, weekly uploading of the image data will allow us to fine-tune the camera targeting, or conduct mid-course corrections as required.
Despite the sea star attack, we were able to recover approximately two weeks worth of time-lapse images revealing new aspects of the biology and microhabitat of foraminifera inhabiting the scallop's back. An example is illustrated below. Three of several specimens (labeled 1, 2, and 3) are seen at t = 0, 4, and 10 days. A scar on the scallop shell (*) serves as a fixed point for comparison. To date, our analysis of 50 Cibicides shows that these species are sedentary parasites. No reproductive events have been observed. Interestingly, movement of the sea star arms across the scallop surface did not result in removal of any Cibicides. We anticipate that an entire season of such imaging data will reveal significant new information regarding the life habits of Adamussium and its epibionts.
Time-lapse sequence showing a high-magnification view of the dorsal surface of the scallop Adamussium colbecki. Three specimens of the foraminiferan Cibicides refulgens remain essentially motionless during the 10-day period. A scar on the scallop shell (*) serves as a stationary reference mark. Frame 1 was taken on 11/16/04 at 00:39:21:00, frame 2 on 11/20/04 at 18:41:06:00, and frame 3 on 11/26/04 at 12:41:55:00.
Additional activities:
Dr. Jack Harris (Russell Sage College, Troy, NY) is conducting sabbatical
studies in Bowser’s lab during the 2004/5 academic year. During
the past two field seasons, we have retrieved micro settling arrays (fancy
name for glass slides taped to a stake) that were deployed for 3 months,
1 year, and 2 years in an attempt to assess biofouling rates and its impact
on remotely deployed sensing equipment. These slides were prepared for
scanning electron microscopy by Dr. Harris and analyzed using a LEO 1550VP
SEM. This analysis reveals that the level of biofouling experienced at
our Explorers Cove study site is comparable to that reported from bathyal
deep sea stations elsewhere. His results will be presented at the East
Coast Protistology Meeting in Virginia this June. The findings are currently
being incorporated into a manuscript for the Journal of Marine Science
and Environment, Part C: Proceedings of the Institute of Marine Engineering,
Science and Technology.
For Environmental Impact Data and GPS Coordinates for the conduit installation,
click here.
‘Winter Battery Test’
In field season 2005/2006, the system will be left in place at New Harbor over the winter. The submerged camera unit will operate from on-board batteries. The shore unit will comprise a fiber-optic cable terminator, a data recorder, and a radio link to McMurdo. This radio transmitter will consume substantial power when active.
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| Winter battery test at the Crary Lab in McMurdo. |
Initially, NSF/RPSC had the impression that we would require a winter-capable power system to be provided through the SIP process; and that we would require substantial electrical capacity, such that a wind generator or other large system would have to be erected. After discussion, we dispelled this requirement by developing a system employing power management to reduce the power demand to a matter of microamps while the system is ‘sleeping’, and ‘waking’ to full current draw for only a fraction of an hour per day. This power requirement can be met by simply installing low-temperature-rated gel-cell batteries of sufficient capacity. The plan is to bury the batteries in a shallow hole in the sand, to protect them from the lowest mid-winter air temperature and provide a thermal buffer in the soil.
To test the concept, we shipped two batteries (each 12 volts, 300 A-h) for the 2003 season and installed them in a hole dug outside the Crary Lab loading door ‘D’. The batteries were placed on heavy-gauge plastic sheet to protect against release to the soil in case of freezing and bursting. They were connected to a small continuous load with voltmeter displays. The Crary Lab winter-over Science Technician sent us the voltage readings by e-mail once every 2 weeks. The results showed that these batteries had sufficient capacity to sustain the planned load for one year of operation.
COMMS testing: In late January, RPSC staff confirmed earlier tests for the placement of the comms antenna.
