From Aggregations to Individuals: Exploring Migrating Deep-Sea Scattering Layers Through Multiscale-Multimode Technologies in the Gulf of Mexico

From Aggregations to Individuals: Exploring Migrating Deep-Sea Scattering Layers Through Multiscale-Multimode Technologies in the Gulf of Mexico

Image Gallery

This page contains photos associated with the From Aggregations to Individuals: Exploring Migrating Deep-Sea Scattering Layers Through Multiscale-Multimode Technologies in the Gulf of Mexico expedition. Click on any image to view a larger version and for additional information.

Figure 1. National Geographic Society Driftcam (left panel) and Teledyne Webb Research Slocum Glider (right panel) with echosounder housing protruding from the bottom of the glider.

Driftcam and Slocum Glider

National Geographic Society Driftcam and Teledyne Webb Research Slocum Glider.

Figure 2. Map illustrating the deployments of both the Driftcams and Slocum Glider in the Gulf of Mexico from July 27-31, 2021. Labels “SC” and “SG” represent the start of Driftcam and Glider deployment, respectively. “EC” and “EG” represent the end of deployment for Driftcam and Glider, respectively.

Driftcam and Slocum Glider Deployments

Map illustrating the deployments of both the Driftcams and Slocum Glider.

Figure 3. Multifrequency echosounder system aboard the R/V Point Sur with four frequencies (18, 38, 70, 120 kHz) installed (left panel). Ascending (center panel) and descending (right panel) phase of the diel vertical migration of the sound scattering layer observed from 0000 to about 1300 UTC on July 29, 2021. The scattering layer can be seen rising from 500 meters (1,640 feet) in depth to 100 meters (328 feet) in depth, and then back down again. The bright horizontal line at 400 meters (1,312 feet) in the right panel is the reflection from the CTD rosette that was also operating an autonomous echosounder at depth with two different frequencies (38 and 200 kHz).

Multifrequency Echosounder System

Multifrequency echosounder system aboard the R/V Point Sur.

Figure 4. Left panel: Satellite surface Chlorophyll a concentration overlaid with a web-based oceanographic model showing surface current vectors (larger arrows indicate stronger currents). Chlorophyll a is a measure of the pigment concentration generated from phytoplankton, which indicates how much primary production is taking place in the water and is a sign of how nutrient rich the water is. High levels of Chlorophyll a in offshore waters indicates a strong freshwater outflow from rivers into the ocean and strong southeast currents act to move that freshwater offshore. The pink circle near 28.8N and 87.2W was the initial sampling location of the thick fresher surface layers. Right panel: Surface current vectors measured from the ship’s acoustic Doppler current profiler (ADCP) with surface water temperature (vector color) indicating the speed (vector size) and direction (vector angle) of water movement. Both the oceanographic model output (left) and ADCP surface currents confirm transport of Mississippi freshwater offshore and to the southeast.

Surface Chlorophyll and Current Vectors

Satellite surface Chlorophyll aand ADCP surface currents.

Temperature and Salinity Profile

Water column profile of temperature and salinity.

Figure 6. A “pseudogram,” a coarse echogram generated by the glider, highlights the scattering layer that the glider encountered between 50-80 meters (164-262 feet) depth. Green corresponds to stronger sound scattering, grey areas indicate the part of the water column where the glider did not detect any scattering during its descent. When the glider surfaces, it transmits this “pseudogram” via satellite to researchers to help determine where the scattering layers are. At the end of a mission the glider is retrieved and the high-resolution raw data can be downloaded.

“Pseudogram” - a coarse echogram generated by the glider.

Dive profile of a simultaneous deployment with two Driftcams.

Figure 8. Echogram from the Glider’s Simrad EK80 Wide Band Transceiver “Mini” echosounder from 1700 to 2200 UTC on July 29, 2021 (upper panel). There is a prominent scattering layer at 50 meters (164 feet), and a faint layer at 250 meters (820 feet). The white, dashed box indicates a zoomed in view (lower panel) of the echogram at 2200 UTC on July 29. As the glider approaches the scattering layers, the layer appearance changes from a fuzzy cloud with a mix of organisms (left side of the lower right panel) to individual organisms and scatters discernable as dots and traces, which allow for closer examination of individual acoustic target strengths (right side of lower right panel). For all dives, the echosounder was configured to collect data to a 50 meter (164 foot) range.

Echogram from the Glider’s Simrad EK80 Wide Band Transceiver “Mini” echosounder.

Figure 9. Organisms detected with the Driftcam within a sound scattering layer between 70-100 meters (230-328 feet). (A) pomfret, Brama caribbea; (B) solitary salp, Salpa spp.; (C) alcypoid polychaete worm, Vanadis spp.; (D and E) ; squid, family Ommastrephidae (F) lights from second Driftcam.

Organisms detected with the Driftcam within a sound scattering layer.

Video segments illustrating the targeted organisms identified in Figure 9 above, in the sound scattering layer between 70-100 meters (230-328 feet). In the segments from which Figures 9B-9D were pulled, the small moving particles are likely amphipods that are outside of the focal range of the camera.

Targeted Organisms

Video segments illustrating the targeted organisms.

Mission personnel on board R/V Point Sur.

Mission Personnel

Mission personnel on board R/V Point Sur.

The glider team deploys the glider using the ship’s overhead crane.

Crane Deployment

The glider team deploys the glider using the ship’s overhead crane.

A member of the glider team helps a member of the Driftcam team move the Driftcam after it was retrieved from sea.

Glider team and Driftcam team members move the Driftcam after retrieval.

Members of the science team are transfixed as they watch video from the National Geographic Society’s Driftcam, taken from 70 meters (230 feet) depth.

The science team watches a video from the Driftcam.

The glider team and ship’s crew work to transfer the glider from the R/V Point Sur to a small boat for deployment.

Glider Transfer

Transferring the glider to a small boat for deployment.

The glider team on the small boat deploying the glider.

The glider team on the small boat deploying the glider.

Underwater view of the glider, after deployment.

Underwater view of the glider, after deployment.

A member of the glider team, John Horne, keeps an eye on the glider’s position in the distance. Meanwhile, other glider team field personnel are in the small boat, en route to retrieve the glider.

Glider Position

John Horne keeps an eye on the glider’s position in the distance.

National Geographic and Second Star Robotics team members deploying the Driftcam “Dory.”

Deploying the Driftcam “Dory.”

Map of the ship’s location in the Gulf of Mexico. The yellow points are labeled with locations of interest, including location pings from Driftcam “Dory” at 4 a.m. and 6 a.m., and its projected location, based on the two previous points, at 9:45 a.m. (yellow point in the center of the screen).

Map of the ship’s location in the Gulf of Mexico.

National Geographic and Second Star Robotics team members communicating with Driftcam “Dory” near the bow of the R/V Point Sur.

Comminucating with “Dory”

Team members communicating with “Dory” near the bow of the R/V Point Sur.

Our National Geographic and Second Star Robotics team members on the small boat to retrieve Driftcam “Dory.” Dory can be seen in the distance, affixed with a bright orange and reflective flag.

Retrieving “Dory”

Team members on the small boat retrieving Driftcam “Dory.”

The Teledyne Webb Slocum glider, nicknamed “Stella,” houses the acoustic echosounder and the acoustic brain, which allows for onboard data processing to produce “Echometric” values (a suite of statistical metrics that characterize the distribution of biomass through the water column).

The Teledyne Webb Slocum glider, nicknamed “Stella.”

An Odroid XU4 computer mounted on top of the Kongsberg Simrad WBT mini echosounder. The computer receives data from the echosounder, computes “Echometric” values (a suite of statistical metrics that characterize the distribution of biomass through the water column), and sends them to the glider science computer for transmission to an iridium satellite when the glider surfaces.

An Odroid XU4 computer mounted on top of the mini echosounder.

Screenshot of the glider mission control software showing individually colored plots of “Echometric” values through two dives. The x-axis represents time and the y-axes represent scales for each metric plotted. The echosounder collects data during dive descents, so values are shown until the end of one dive and then the plots jump to the start of the next dive. In the figure the first descent occurs during the first quarter of the graph. The second dive starts after the ascent and is located in the final quarter of the graph.

Mission Control

Screenshot of the glider mission control software.

The transducer pod holds the four frequencies (18 kHz, 38 kHz, 70 kHz, and 120 kHz) of transducers, seen here as orange circles, that are used to sense mesopelagic communities from the ocean surface.

The transducer pod holds the four frequencies of transducers.

This laptop, showing three echograms, is hooked up to the four transceivers (black boxes on the right hand side of the photo). Each transceiver is hooked up to its respective transducer, which is housed in the transducer pod pole-mounted to the ship. Together, the transceivers and transducers make up the echosounder.

Echosounder Laptop

This laptop, showing three echograms, is hooked up to four transceivers.

Image from an echogram showing backscatter from the water column from the surface (at the top of the image) to 1,000 meters (bottom of the image) over time (from left to right on the image). Higher backscatter is shown in green, to yellow and red. Lower levels are in blue and black. The pattern of vertical migration is reflected in the undulating pattern in the high backscatter.

Image from an echogram showing backscatter from the water column.

The National Geographic Society Driftcam is an untethered mid-water imaging system, built to collect detailed information about ocean animals via high-resolution video, at depths as deep as 700 meters (2,297 feet).

The Second Star Robotics and National Geographic team working on the Driftcam.

Camera Closeup

A closeup of the cameras enclosed within the glass sphere of the Driftcam.

Driftcam Diagram

Driftcam Diagram

Labeled diagram of the Driftcam.

Driftcam Test

The Driftcam being tested at the Neutral Buoyancy Research Facility at the University of Maryland.

Echogram

Echogram illustrating the ascending and descending phases of the diel migrations through the water column.

Driftcam Prototype

Driftcam Prototype

Driftcam prototype developed by National Geographic Society configured with high-resolution low-light cameras.

Slocum Glider

Slocum glider with integrated Simrad EK80 Wide Band Transceiver (WBT) Mini echosounder.

Acoustic Backscatter Data

Acoustic Backscatter Data

Acoustic backscatter data at 18kHz (top) and 38 kHz (bottom) shows the vertical and horizontal distribution of biological scatterers.