August 8-14, 2024
Setting Up the Osmo at Southern Hydrate Ridge
As part of our ongoing research at Southern Hydrate Ridge, I teamed up with Nikola Jensen and Andrew Paley to set up an osmotic sampler (osmo) that will play a crucial role in my senior thesis on seep environmental benthic megafauna. The osmo is designed to measure fluid chemistry over long periods, providing valuable data on the hydrothermal and methane seep environments that influence the ecosystems we are studying. Understanding fluid chemistry is vital, as it impacts, and is impacted by, reactions in hydrothermal chimneys, seep sediments, and the biota that thrive in these extreme environments.
The osmo we set up is a sophisticated instrument designed to draw in hydrothermal- and methane seep-derived fluids into small capillary-like tubing over the course of a year. These uncabled samplers are deployed in key locations, such as the diffuse flow site near the Mushroom black smoker chimney and Einstein’s Grotto at Southern Hydrate Ridge. After a year, the samplers are recovered by a remotely operated vehicle (ROV), and the fluids collected in the tubing are analyzed onshore to understand the temporal evolution of fluid chemistry. This data is particularly useful for assessing the impact of seismic events on fluid flow in these environments.
The osmo sampler we worked on contains four acrylic tubes filled with hundreds of meters of coiled tubing, each serving a specific purpose. The coils include a large sample coil, a short sample coil, a bonus sample coil, and an acid coil. The small sample and acid coils are about 150 meters long and hold around 170 mL, while the large sample coil is 300 meters long with a volume of approximately 340 mL. The system also includes a small and a large salt-based osmotic pump.
Osmosis, the movement of water through a semi-permeable membrane from a region of low solute concentration to a region of high solute concentration, drives the sampling process. However, osmosis cannot occur through air, making it critical to ensure that no air enters the system. To achieve this, we backfilled the tubing with Milli-Q water during assembly to maintain the effectiveness of the osmotic filters.
The acid coil, unlike the other coils filled with Milli-Q water, is filled with an acid tracer composed of HCl and dysprosium. Dysprosium is incredibly rare in nature, so its presence can be safely assumed as an indicator of the tracer and not part of the sample. This coil is particularly important for detecting and analyzing changes in fluid chemistry.
The first connection Nikola and I made was between the inner coil of the large sample coil and the outer end of the small sample coil. We carefully cut the tubes to the appropriate length, placed headless nuts on either tube, wrapped Teflon tape in the opposite direction of the threading to ensure a secure grip, and screwed green ferrules onto the tubes to create a tight connection (see Fig. 1). During these connections, we backfilled the tubing with a 22g needle and syringe filled with Milli-Q water to ensure no air was trapped inside.
Next, we fed the outer end of the large sample coil, the outer bonus coil, and the inner acid coil through the body of a probe that will be placed deep into the silt and mud sediment at Southern Hydrate Ridge. Although most of this assembly involved basic piping and tubing, the probe tip was a specialized component. It contains four pore openings designed to obtain fluid samples while mixing in the acid tracer and keeping a bonus sample for less high-resolution data (see Fig. 2 for the ROV manipulatable probe). We then threaded a strand of green PEEK tubing, known for its chemical resistance and ability to withstand temperatures up to 260°C and a pH of 2, through the probe tip into the probe body.
We did not connect the seawater side of the small osmotic pump to the outer side of the acid coil yet, as this would start the pump adding acid. Since we have a limited quantity of the tracer on board, this step must wait until just before deployment during Leg 2 at SHR.
Finally, Andrew showed us how to secure the thin tubing running from the osmo to the probe, ensuring that it wouldn’t be damaged by crabs, rocks, or other potential hazards. To protect the tubing and provide stress relief, we placed the small tubes into a Tygon tubing sleeve, then covered them with a protective, abrasive-resistant, and highly visible orange tubing (see Fig. 3). We also zip-tied this orange cover and added hose clamps on either end and a yale grip on the osmo side to further secure the assembly.
I’m incredibly grateful for Andrew’s preparation and thorough explanations throughout the process. He walked us through each step with patience, ensuring we understood the importance of every detail. In fact, he assigned us to write a blog saying that the osmo changed our lives.
While that may be a bit (very large) of an exaggeration, I’m genuinely thankful that I now have a solid understanding of how this critical instrument works. The data this osmo will collect is vital for understanding the dynamic processes at work in hydrothermal and methane seep environments, providing insights that will hopefully inform my senior thesis and contribute to our broader understanding of these extreme ecosystems.
August 10, 2024
During last night’s dive at the Slope Base site, I observed a particularly intriguing benthic ctenophore attached to a junction box at 2900 m water depth. Ctenophore or comb jellies are some of my favorite animals as, they are one of the most likely candidates for being the first animal to evolve on Earth sometime during the Neoproterozoic, even out dating Ediacaran fauna. Most of these animals are pelagic or free swimming and drift through the water column picking up food along the way. What is so interesting about this particular specimen in comparison to all of the other Ctenophores that we saw on Jason’s descent was the fact that it was attached to the seafloor or benthic. This is rare in its own right; however it is especially rare to see a benthic Ctenophore at depth and at this latitude.
A similar specimen first caught my attention during the 2023 VISIONS cruise, and its reappearance in our latest dive suggests that it may represent an undocumented or rarely observed species. The consistent sightings at this site, coupled with its distinctive morphological features, led me to investigate its potential classification.
The only documented image resembling this ctenophore comes from an ROV dive taken on NOAA’s 2016 deep water voyage aboard the Okeanos Explorer, which surveyed from Guam to Saipan in the Northern Mariana Islands. This image (First figure) was also classified as an unidentified ctenophore and shares several morphological similarities with both years images. Based on these observations, I hypothesize that this species belongs to the order Platyctenida and the family Coeloplanidae.
Several key morphological characteristics support this hypothesis. The ctenophore displays a dorso-ventrally flattened body with secondary bilateral symmetry, terminating in two distinct lobes—a body plan typical of Platyctenida, which are adapted for a benthic lifestyle. Additionally, the absence of ctene rows, a feature found in most other ctenophores, aligns this specimen with Platyctenida. The presence of two tentilla-bearing tentacles, extending from pores beneath the dorsal surface, and containing collocytes for prey capture, further supports its classification within the family Coeloplanidae.
One particularly interesting aspect of this ctenophore is its attachment method. It uses a modified structure (either pharynx or gut diverticulum), functioning similarly to a mollusk’s foot, to anchor itself to the substrate or in our case a J-box. This epibiont attachment style is characteristic of some members of the genus Coeloplana within the family Coeloplanidae. Moreover, most members of the order Platyctenida are ectosymbiotic and epibionts of various marine organisms such as crinoids, octocorals, and anemones. This symbiotic behavior is consistent with the observed ctenophore’s attachment to the junction boxes at the Slope Base site. And as the aforementioned fauna can be commonly found at slope base, this may give insight into its natural host for attachment.
Geographically, most species within the order Platyctenida are concentrated around warm tropical islands in the Indo-Pacific region in shallow water. A few species are known as coral-based epibionts in Florida and Hawaii, but there is almost no documentation of Platyctenida along the West Coast. This lack of records makes the repeated sightings at the Slope Base site particularly noteworthy and suggests that this region may host previously undocumented species.
Although many species within Coeloplana are cryptically colored, one tropical species, Coeloplana meteoris, exhibits both similar coloration and morphologically analogous structures to the specimen observed at the Slope Base site. The combination of these morphological traits and the attachment style strongly suggests that the observed ctenophore is a member of the family Coeloplanidae. This raises more questions however as most Coeloplana meteoris have only been documented in the indopacific or Arabian-Persian gulf.
Given the rarity of such sightings, the recurrent observation of this ctenophore at the Slope Base site is significant. It raises important questions about the distribution, ecology, and taxonomy of this organism. To confirm its classification and better understand its role within the benthic ecosystem, further investigation aboard future cruises would be a really cool step into better understanding the creature.
In conclusion, the ctenophore I observed at the Slope Base site appears to be an undocumented or rarely observed species within the order Platyctenida, possibly belonging to the family Coeloplanidae. Continued observation and documentation of such organisms are crucial for advancing our understanding of deep-sea biodiversity and the complex ecological interactions that occur in these extreme environments.
August 8-9, 2024
Today marks an ambitious first 24-hour period aboard the R/V Atlantis as we embarked on a series of three dives at the Oregon Offshore Site, approximately 42.1 nautical miles from Newport. The primary mission involved swapping out platforms on the Shallow Profiler Mooring located around 200 meters below the surface.
Our day began early with a sense of anticipation. After a hearty breakfast, the team gathered in the Main Lab for a series of safety drills, both on the ship and on deck, to prepare for an abandon-ship scenario. After the drills, I spent time labeling bottles with scannable barcodes for nutrient analysis and helped the RCA crew tie down lab equipment as the ship got underway.
I missed the first dive due to tying down equipment, but I was able to catch the second. The second dive for the Jason crew commenced shortly after 14:00. As Jason descended into the depths, the water column was mostly calm except for a few interruptions from floating jellies and euphausiids. The goal was to take a new science pod down to a shallow profiling mooring. After descending around 200 meters with the science pod attached, Jason swapped out the old biofouled platform with a new pod. During this dive, the profiling wire was inspected, revealing some minor degradation and splitting on the cable, but nothing too major. After recovery of the old science pod back on deck, I was able to inspect the biofouling crinoids that settled on the instruments.
Afterward, I went to my 20:00 to 24:00 watch and logged events in the Jason van. The dive I was watch-standing for had a similar objective as the first couple and also resulted in a science pod replacement. My watch only caught the end portion of the dive and the start of another but was still somewhat eventful.
As my watch in the van ended, I switched over to setting up the CTD rosettes and helping the wet lab set up materials and protocols for Niskin sample analysis. For instrument verification, CTD casts regularly go down to around 220 meters, collecting water samples along the profile to serve as ground truths for the moored profiler’s streamed instrument data. After everything was set up, we transited 500 meters up-current from the instrument site we were verifying (currents were sensed by the ship’s ADCP). We then proceeded to cast the CTD off the starboard side of the ship. After checking that the bottles were cocked correctly and the CTD was ready for deployment, Alex Rose and I suited up in work vests and steel-toed boots to guide the CTD and keep it level by pulling on a large rope attached to the deck with a bowline knot as the winch operator brought it up and over the vessel’s railing. This brought us well into the night, ending with me falling asleep around 3:00 AM.
The next morning started off early at 7:00 AM with me and Nikola Jensen helping lab technician Andrew Paley troubleshoot a tube-based instrument called a CAT. Unfortunately, during shipment or storage, the housing for the unit cracked, causing the pump to be knocked out of place and potentially introducing air into the delicate system. We attempted to push a syringe full of Milli-Q water through the main coils, but to no avail. I’m excited to continue my work today and look forward to the rest of the trip!