Perth Canyon and Gascoyne May 2023
Unlocking the Secrets of the Abyss
In May 2023, after nearly a month at sea, our team returned to The University of Western Australia and washed the Indian Ocean spray from what was left of our gear in the workshop. We will get to what is not left, shortly. The start of 2023 was wildly busy for the Minderoo-UWA Deep-Sea Research Centre, but it seems appropriate to reflect on this inaugural voyage to the deep abyssal plains in Australia’s network of marine parks.
Project Overview
In collaboration with the Minderoo, WA Museum, and Parks Australia through the Our "Marine Park Grants" the team of research was led by Dr Todd Bond on the Project's maiden voyage to explore and monitor the deepest marine parks off our mainland.
This work has three ambitious components:
1. Explore, describe, and understand what animals live in Australia’s deep sea beyond 1000 m
2. Understand how deep-sea animals are connected among different locations, and
3. Continuously monitor two different abyssal plains in 4000-5000 m water depth and located 1000 km apart for 18 months.
The project is based at two deep-sea locations in Australian Marine Parks offshore Western Australia - the Perth Canyon Marine Park which encapsulates the Perth Abyssal Plain and the Gascoyne Marine Park comprising the Cuvier Abyssal Plain. These marine parks are part of the extensive Australian Marine Parks network within Commonwealth waters of which more than 56% is deeper than 3000 m. Although these parks cover a lot of deep sea, our knowledge of these deep-sea ecosystems is very limited, and there is no ongoing monitoring. Until now.
Custom-Built Obervatories: A World-First
The primary objective of our recent voyage was to deploy two custom-built, long-term, deep-sea observatories. These observatories were designed and built specifically for this project and are the first of their kind in the world. Using these observatories, we aim to understand how the oceanographic conditions impact the amount and composition of “marine snow” falling to the deep sea and if this changes the abundance and composition of animals living on and moving around the seafloor.
Image credit Giacomo Dorlando
The Gear
Each observatory consists of a stainless steel frame which sits on the seafloor and is held in place with steel ballast. The frame itself holds a time-lapse camera and light,battery, an array of oceanographic sensors, and an acoustic release connected to steel ballast that it can release on command. The camera has a hibernation switch that allows for long-term deployments. It is programmed to capture an image every 12 hours, offering us a unique glimpse into the ever-changing seafloor on the abyssal plain. The array of oceanographic sensors includes a conductivity cell, temperature probe, depth sensor, oxygen probe, and acoustic current sensor measuring both direction and strength. These sensors will help us understand the complex relationship between oceanographic conditions and benthic organisms filmed using the camera.
To complement data collected at the seafloor, we incorporated a sediment trap positioned 300 m above the observatory frame. This equipment funnels falling material into a collection bottle containing a preservative, effectively halting degradation. The bottle is within a carousel system, with a new, empty bottle replacing the full one every two weeks. Placing the sediment trap above the seafloor minimizes the collection of material resuspended from the seafloor, ensuring a more accurate representation of the organic and inorganic matter falling through the water column and reaching the seafloor.
Image credit Giacomo Dorlando
Time-lapse Camera
- SubC Imaging Rayfin Mk2 Benthic 6000 m 4k camera
- SubC Imaging Aquorea Mk3 LED strobe
- 1TB internal storage
- SubC Imaging hibernation expansion board
- Custom titanium battery housing with 50.4V 69AH LI-ION battery with BMS
Seaguard Platform
- Seaguard basic platform 6000 m with colour LCD touch screen
- Aanderaa Z-pulse doppler current sensor 6000 m
- Aanderaa conductivity sensor 0-7.5S/M + temperature 6000 m
- Aanderaa fast response temperature 6000 m
- Aanderaa pressure sensor + temperature 6000 m
- Aanderaa fast response oxygen optode MKII DW 6000 m
- Internal lithium batteries 7V 35 AH x2
Sediment Trap
- McLanes 13x bottle sediment trap
- Titanium frame
- Electronic stepper motor and controller in titanium housing 6000m
Obserservatory frame and rigging
- MFT Fabrication 316 stainless steel custom frame
- CRP Marine floats 6000 m
- iXblue OCEANO 2500S Universal acoustic release 6000 m
- 8 mm Superspeed line
- Blueline tapered bearing thrust swivel 1T
Image credit Giacomo Dorlando
From Delay to Deployment
As the build on each observatory began, it became evident that the supply of deep-sea components had not improved “post-COVID”. After significant time delays with critical components, months of planning and building came down to a few critical components delivered the day we planned to set sail. Unfortunately, the weather off Perth was very poor (4+m swell and 30+knots of wind). This meant our research vessel, Adrianus remained tied up at Fremantle Fishing Boat Harbour which gave us a few extra days to finalise gear.
After more than a week of waiting, a small weather window opened off Perth with only one night of vessel charter remaining. The research team mobilised on Adrianus for dinner in the harbour, went to bed, and woke up 20 nautical miles offshore, transiting in 25 knots of wind and a 2 m swell - far from ideal weather. Adrianus finally reached the deployment site in 4300 m water depth by the afternoon, and the favourable weather forecast began taking shape. Finally, it seemed realistic that we could deploy the observatory.
Observatory Installation: Navigating Deep Waters
Each observatory consists of three major components connected using 350 m of line. Deploying such a long line of gear is complex and the reason we require fair weather. We started with the top float and flag and began laying out the line connected to the top of the sediment trap whilst the vessel moves forward. After carefully lowering the sediment trap into the sea, we fed out 300 m of line between the sediment trap and main frame. Once all the line, floats, and sediment trap were in the water under tow, we lifted the main frame using the vessel’s A-frame. The main frame was connected to the A-frame with a quick-release hook and as soon as it reaches the waterline, we released the hook and the system descended into the abyss dragging the floats and sediment trap down with it.
Although the primary focus of this voyage was to deploy each observatory, we planned to utilise our time offshore to undertake additional research using a set of three baited landers. The weather allowed for one night at sea, so we deployed three landers that same evening.
Baited lander Deployment Beyond 4000m
Landers are soaked overnight, collecting information for approximately six hours. The landers in the Minderoo-UWA Deep-Sea Research Centre are fitted with video cameras, lights, the same oceanographic sensors as the observatories (CTD, oxygen probes, and current sensors), and a variety of traps. The traps primarily target decapods, amphipods, and fish and allow us to collect animals and investigate connectivity between deep-sea environments while also discovering new species.
We have deployed baited landers to 1000 m in the Perth Canyon Marine Park before, but never beyond 4000 m. The depth of each lander is calculated using RBR sensors which measure hydrostatic pressure. However, these data, like all data collected using landers, are only available when the lander is retrieved.
In this instance, our landers landed on the seafloor at 4302 m, 4507 m, and 4633 m. Each video showed pale fluffy sediment and the bait attracted several large grenadiers. Each trap yielded a small haul of amphipods and included a large charismatic deep orange Eurythenes sp. These specimens and videos provide a short glimpse into the life of organisms beyond 4000 m, but the data collected using the observatories will provide greater information. Including what organisms might be feeding on and if that supply of food changes throughout the year.
Image credit Giacomo Dorlando
Journey to Gascoyne Marine Reserve
With the Perth Canyon observatory safely on the seafloor, we returned to Fremantle for a crew change, turnaround of gear, and resupply before steaming north to Gascoyne Marine Park. The journey to Gascoyne was over 1200 km or 650 nautical miles and took four days. Thankfully, the weather was on our side, and we had light winds and swell for the entire journey. The weather continued in our favour and the 7-day forecast off Exmouth lived up to our expectations of Magic May.
The continental shelf and marine park are a lot larger at Gascoyne and it is one of a few Commonwealth Marine Parks that go from State waters to the edge of Australia’s exclusive economic zone (220 nautical miles). The Park is huge, and it took more than 12 hours to steam from our first set of landers at 1000 m to the site where we planned to deploy the second observatory.
We rely on existing bathymetric data to know the depth where we plan to deploy each observatory. At Gascoyne, we aimed for 5100 m but will not know the exact depth until we retrieve the system and download the data. Our observatories will collect data over the course of at least 18 months, thanks to our collaboration with Parks Australia, but require a service every 6-9 months. Servicing involves downloading data from the time-lapse camera and oceanographic sensors, charging batteries, and replacing the bottles in the sediment trap. The only way to do this is to communicate with the acoustic release on the main frame and release the ballast to float the entire system to the surface.
Observatory Servicing in Gascoyne: Servicing Plans
The Magic May forecast was accurate. We deployed the observatory and worked for five days straight deploying landers each evening, soaking them overnight, and recovering them each morning. As the charter came to an end, we successfully deployed the observatory and completed 15 lander deployments, of which 12 were deeper than 4000 m.
We filmed snailfish (Liparidae), robust assfish (Bassozetus sp.), deep-sea prawns (Cerataspis monstrosus), and even sea cucumbers launching themselves off the seafloor. Many of these species have not been filmed in Australian waters before, and some may be new to science.
The snailfish were of particular interest to us. Our team has filmed snailfish all over the world (including the deepest fish ever and the deepest fish offshore mainland Australia), but the three we filmed in 1000 m at GMR were particularly interesting. On first pass, they appear to belong to the genus Careproctus, which translates to butt-face. Not endearing.
Post Expedition Analysis and Future Plans
Now back in the office, the research team will analyse the lander video footage, plot and assess the CTD and current sensor data, and plan for the next voyage to service the long-term observatories, due to occur in September, October, and November. All the biological specimens will be catalogued, and those of interest will undergo molecular analyses to determine their identity but also to understand where they fit in the global populations of deep-sea organisms.
Finally, Australia is now monitoring its deep sea.
