When Alessandra Walsh returned to dry land, she struggled to sleep without being rocked.
She'd become used to being lulled by the Atlantic Ocean after working 12-hour shifts aboard the Tom Crean, Ireland's national research vessel.
It was part of a routine she adopted for 13 days this past July, working as a researcher on the MOSAIC (Multi-disciplinary Ocean Sensing for Adaptive International Conservation) project. The initiative brings together 11 partner institutions from across Ireland, Northern Ireland, Scotland and Canada, including Western University.
The voyage took Walsh to the Rockall Trough, a deep ocean basin northwest of Ireland and Scotland. As a PhD candidate studying marine predator-prey interactions, she is supervised by Western biology professors Paul Mensink and Yolanda Morbey, along with Jonathan Houghton of Queen's University Belfast. She'll be part of the MOSAIC project for the next four years, as the group works to create a cross-border, interregional, multi-sensor marine biological observation network to gather data on endangered and declining species and their ecological environments.
Growing up in Hong Kong, Walsh has a lifelong love of the ocean. Working with grey seals while pursuing her master's at Oxford University was formative, driving her to pursue "science that makes a difference."
"I'm quite motivated to help encourage policy shifts to protect ocean environments through science, and I believe the MOSAIC project is an opportunity to effect that change," Walsh said.
Generating evidence to inform fisheries management
Walsh is excited to be part of a global effort aimed at generating data-driven action plans and decision-making tools to bolster ongoing monitoring activities and help strike the fine balance between conservation efforts and fisheries management.
MOSAIC's mission lends itself well to her doctoral research investigating how climate change will affect deep offshore marine ecosystems in the North Atlantic. By studying highly mobile pelagic (open ocean) predators, such as porbeagle and basking sharks, and their prey, she hopes to contribute to a better understanding of how these ecosystems respond and adapt to environmental change.
Climate change is raising ocean temperatures, altering spawning and feeding cycles in coastal and deep-water systems. That, in turn, affects the movement of pelagic predators.
"As we run out of coastal species to fish, we're pushing fishing trawlers out farther and farther to fish deeper," Walsh said. "From a sustainability perspective, I think it's important to get ahead of that trend and any changes in fisheries regulations, using published data to inform the decisions on how fishing is managed in the deep ocean - particularly in places where we still know so little about how these ecosystems function."
Studying deep pelagic communities
During her summer research post, Walsh woke by 5 a.m., ready to relieve those on the night shift by 6 a.m.
Until 6 p.m., she worked alongside the other researchers and an operations crew, gaining hands-on experience on a team that acted much like a "cohesive military unit."
"You adapt and settle into routine really quickly," Walsh said.
Throughout their journey, the team made 25 different stops, going through the same process each time. The first step involved lowering a CTD (Conductivity, Temperature and Depth) sensor unit, containing about two dozen bottles that snap shut at staggered depths, to pull up water samples for environmental DNA and RNA testing, which reveals what species are living at specific water levels.
A bongo net followed, skimming the surface for plankton. Then, a multi-net trawl was lowered, spending up to five hours hauling in small fish and other prey species from as deep as 1,400 metres.
Species samples included an anglerfish (think black sea devil who tricks Dory in Pixar's Finding Nemo) and a variety of squid. When the gear came back up, Walsh worked fast to help process the haul. This included measuring fish, taking tissue samples for stable isotope analysis (which shows where an animal has been and what it has been eating) and preserving samples for species identification.
"We had no idea what some of these creatures were," Walsh said. "People with a lot more knowledge of smaller species than I have will study that under microscopes to catalogue the sheer number and diversity. But I came away with knowledge of the more common fish species that I hadn't been familiar with, so it was a nice, sharp learning curve for me.
A bright idea: Testing to verify bioluminescence
Walsh also took advantage of her time on the boat to test a potential strategy to track deep-sea prey.
Tags already attached to big predators such as basking sharks carry light meters, normally used to estimate the animal's location, based on sunrise and sunset patterns. Building on promising earlier research, she and Mensink wondered whether those same light meters could be directly calibrated to detect bioluminescence from deep-water prey hundreds of meters below the surface - since roughly 75 per cent of matter in the deep ocean glows. If successful, the satellite tags could reveal not only where pelagic predators move, but also how prey layers shift through the water column over time as the climate changes - helping researchers better understand and predict how entire marine ecosystems are responding.
To test if the tags' readings could be validated as actual bioluminescence, Walsh tracked down and borrowed a specialized sensor from researchers in France, mounting it on one of the trawl nets alongside two standard tag models.
Having sent the sensors back to France to be read, she now awaits the results.
"If it works, we will have years and years' worth of active data showing where the tagged predators were encountering prey, not just where they were swimming," she said.
With the MOSAIC crew's next journey in mind, Walsh also mocked up a map for a proposed new survey, which would include high-traffic corridors for basking sharks, porbeagle sharks and leatherback turtles.
"Being able to sample from those densely used areas would be quite valuable for my analysis," she said.
Feeling at one with the sea
As Walsh wrapped her long days, she often headed to the vessel's crow's nest, where she'd spot whales and dolphins. Nightly visits from guillemots, deep-diving coastal seabirds, were also part of the routine.
"They'd show up like clockwork, without fail every night around 6:20," Walsh said. "They'd start diving and congregating in large numbers around the boat."
Walsh believes more people would be motivated to protect oceans if they could experience them firsthand.
"There's an incredible calm when you look out on the ocean and it just goes on for miles and miles," she said. "You feel at one with the tradition of going out to sea."
She said reading the historical accounts of people sailing across the Atlantic for the first time is something you can't fully grasp "until you're out there, seeing absolutely nothing."
"That used to be part of people's lives. They'd bank on nothingness and go anyway. The courage that took - now we have GPS, you'd have to try hard to get lost.
"Being out there for days, you appreciate how vast and powerful the ocean is. The sheer expanse is amazing."
