Professor James Bell gets ready to lay some tiles on the loch floor, with the hope that sponges will grow on them. Photo: Claire Concannon
Lying prone over the edge of the jetty Gabi Wood lifts a small grey tile from a metal cage into a bucket of water. Tied to the tile is a small piece of bright yellow marine sponge - Cliona celata. After a few weeks of healing after being snipped from a 'donor sponge', it's ready to go to its new home.
It's not going far, but this could be an important step in helping sponge communities to recover in Ireland's oldest and most renowned marine reserve.
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Loch Oighinn / Lough Hyne in West Cork, Ireland, is a sea inlet fed from the Atlantic. Photo: Claire Concannon
Gabi is a PhD researcher at Victoria University of Wellington, but she has skipped the past three New Zealand winters, swapping them for long Irish summer days in southwest Cork, at a place called Lough Hyne / Loch Oighinn.
Lough Hyne could come straight from a tale of Irish myths and legends: a small sea inlet surrounded by trees and fields, itself encircling Castle Island - the crumbling remains of the island's namesake long covered in green.
At one end, beside the narrow winding road, kids splash and kayaks launch. At the other, accessible only by boat, a small white laboratory is tucked amongst some bracken and ferns. Beside it a narrow, shallow strip of water, called the Rapids, connects the loch to the Atlantic Ocean, and sets up its unique tidal regime.
Lough Hyne became Europe's first marine reserve in 1981, but research into its diverse array of habitats - home to more than 1800 species - had begun long before that. Over time, labs have been built along the shore to allow researchers to stay and complete detailed marine ecology studies.
Maintained by University College Cork, the Renouf Lab - named for zoologist Louis Renouf - has been Gabi's home while she's been researching here, focused on one big question: what happened to the sponges here?
The narrow rapids connect Lough Hyne to the Atlantic Ocean and are responsible for it's unique tidal regime. Photo: Claire Concannon
It was a question first asked by Gabi's supervisor, Professor James Bell, in 2016. In the late 1990s and early 2000s, while still a doctoral candidate at University College Cork, James studied the sponge communities found on subtidal cliffs dotted around the loch.
Sponges grow where seaweed can't, on seabeds and sub-surface cliff faces that would otherwise be bare, so they are important habitats for other critters, and may also be important for providing food. Their own diet includes phytoplankton and bacteria - so they're good for keeping balance in ecosystems.
After completing his PhD, James took up a role at Victoria University of Wellington, continuing his sponge research. During a 2016 sponge conference in Galway, he was excited to show his New Zealand students the amazing sponge-clad cliffs of Lough Hyne, but there was a surprise in store - many of the sponges had disappeared.
Subsequent conversations with Ireland's National Parks and Wildlife Service and researchers at University College Cork set the scene for James to return to Lough Hyne with a mystery to solve: what the extent of the disappearance was, and why the sponges had gone in the first place.
When not diving, Gabi and Kea run temperature and metabolism experiments in one of the lab's workrooms. Photo: Claire Concannon
Testing the usual suspects
James and his team have run many experiments in the years since to investigate what could have caused this loss, but a clear answer so far eludes them.
In the lab, the sponges have proven resilient to all sorts of changes: warming, addition of nitrogenous fertiliser, lack of oxygen. Gabi did the experimental work on the nitrogenous fertiliser, using sponge species from both Lough Hyne and New Zealand. Now she's investigating what the sponges are eating in the loch.
One remaining suspect, yet to be tested, is hydrogen sulfide. It's on the list because of a phenomenon that sometimes occurs in the summer, where the water settles into layers by temperature, setting up a low-oxygen condition at the bottom of the lake where certain bacteria that produce hydrogen sulfide can thrive.
James is frustrated by the lack of clear answers over the sponges' disappearance, but over time they've begun to see recovery of some of the sponges in certain areas.
Gabi Wood records dive details from Professor James Bell and Kea Witting after a Lough Hyne dive. Photo: Claire Concannon
The pattern of return
By using pins in the seafloor to lay quadrats, they've amassed a large collection of images taken in the exact same place, twice a year at eight different sites. As part of her PhD research at Victoria University Wellington, Kea Witting will analyse these pictures to investigate the pattern of sponge community recovery. Is it always the same species that show up first? What moves in after those early colonisers?
While the sponges in Ireland are not the same species as those in New Zealand, they share similarities, and likely play equivalent roles within their respective ecosystems. Kea is hoping what she learns in Lough Hyne will contribute to the broader knowledge about these types of sponge communities and ecosystems. The long-term dataset they have is a huge advantage, but so too are the unique diving conditions to be found in the loch. Accessing these kinds of sponges normally requires deep dives in challenging coastal areas. Lough Hyne is calm and easy to access.
This year the team has a new question - can they give the returning sponges a helping hand?
They're trialling a few methods. They've shifted large rocks with sponges on themfrom one area to another. Pieces cut from 'donor sponges' should continue to grow into a new sponge when moved on the tiles to their new homes. Windchime-style arrangements of tiles tied together with wire are also being left out in recovering areas, in the hope that sponges will grow on them naturally, and then easily moved elsewhere.
One experiment involves moving sponges from one area of the loch to the other. They are settled onto small tiles first. Photo: Claire Concannon
It's all early days but they're hoping the various trials will have broader applications, James says. "The techniques that we develop here at the loch will be useful to anybody doing restoration of sponges anywhere in the world". He's not aware of such restoration being attempted before, and he hopes that New Zealand will never be in a position where it is needed. In the meantime, some of the experiments at Lough Hyne have led to new insights about sponge species in both Ireland and New Zealand.
The opportunities for his students have also been invaluable, James says. "The really cool thing about this project as well is it's a real-life applied science question. A lot of things we do are academic in nature, but there's a real-world outcome to try and understand what's happened at a marine reserve and then try and support it not happening again."
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