California scientists are growing young bull kelp in laboratory tanks before placing it back into coastal waters where underwater forests have largely disappeared.
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forests → grow → waters
At Bodega Marine Laboratory, researchers have developed cultures containing as many as 74,000 kelp spores per millilitre, creating a steady supply for restoration work.
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researchers → develop → work
The effort is aimed at rebuilding parts of Northern California’s kelp forests, which have been badly damaged by warming seas, the loss of sea-star predators and the resulting spread of purple sea urchins.
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which → aim → urchins
The first young plants are now being moved from controlled laboratory conditions to the ocean.
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plants → move → ocean
How the kelp restoration reached 74,000 spores per millilitre
The restoration centres on bull kelp, a large brown algae that once formed extensive underwater forests along Northern California.
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that → reach → California
Courthouse News Service reported that bull kelp can grow as much as a foot a day and reach nearly 100 feet in height, despite living for only about a year.
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kelp → report → year
Its decline became especially severe after 2014, when unusually warm ocean conditions coincided with major ecological changes.
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conditions → become → changes
As Courthouse News Service explained, purple sea urchins multiplied while a disease devastated sea stars that normally helped keep urchin numbers under control.
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that → explain → control
The result was a rapid shift from kelp-covered reefs to areas dominated by hungry urchins.
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result → cover → urchins
Scientists at UC Davis Bodega Marine Laboratory now collect reproductive material from healthy adult bull kelp and carefully raise it through its early stages.
NOAA explained in its 2024 account that the spores are nurtured under controlled seawater and sunlight conditions before being encouraged to settle on special twine.
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spores → collect → twine
The scale of the lab work has increased considerably.
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scale → increase → work
The Greater Farallones Association reported that its Kelp Restoration Team had cultivated bull kelp cultures reaching 74,000 spores per millilitre in tanks at Bodega Marine Laboratory.
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Team → report → Laboratory
The team used that material to inoculate 100 metres of restoration twine with juvenile bull kelp.
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team → use → kelp
It then successfully placed 54 metres of the twine at Fort Ross Cove.
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It → place → Cove
Just weeks later, divers recorded young bull kelp growing on the restoration structures and on the nearby seafloor.
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kelp → record → seafloor
The Greater Farallones Association also reported that 199 juvenile bull kelp, measuring between 3 and 120 centimetres, were prepared during the summer for placement on ARKEV restoration units at Stillwater Cove.
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kelp → report → Cove
This marked the first time that the technique had been tested there.
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technique → mark → time
Julieta Gómez, a kelp restoration specialist with the Greater Farallones Association holds up a juvenile kelp specimen at the UC Davis Marine Laboratory.
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Gómez → hold → Laboratory
Image Credit: Carly Nairn/Courthouse News
What happens to the kelp before it reaches the sea
The young plants require careful attention because the lab is replacing several parts of their natural environment.
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lab → happen → environment
Bay Nature reported that researchers grow tiny kelp beneath lights before gradually moving them through different stages of development.
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researchers → report → development
At around 3 months old, young plants can be prepared for outplanting.
Courthouse News Service described how researchers move the growing kelp from small lab containers into larger vessels as they develop.
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they → prepare → vessels
Light levels must be adjusted as the plants grow, while seawater conditions also have to be managed carefully.
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conditions → adjust → ?
Once mature, the kelp produces reproductive patches called sori, allowing researchers to collect another generation of spores.
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researchers → produce → spores
This makes the laboratory more than a nursery for individual plants.
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laboratory → make → plants
It can also serve as a source of reproductive material that can be used repeatedly in restoration work.
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that → serve → work
Scientists are also removing sea urchins
Growing kelp is only one part of the challenge because young plants are being returned to an environment where they can quickly be eaten.
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they → remove → environment
NOAA noted that restoration teams are working with fishers and commercial urchin divers to reduce purple sea urchin numbers around planting sites.
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teams → note → sites
Bay Nature described the situation as a difficult cycle.
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Nature → describe → cycle
After the loss of predators and the decline of kelp, purple urchins spread across the rocky seafloor and continued feeding on any kelp that managed to appear.
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that → spread → kelp
This can make an urchin-dominated reef remarkably difficult to turn back into a kelp forest.
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reef → make → forest
The Greater Farallones Association said its restoration programme has already removed more than 190,000 pounds of purple sea urchins from restoration sites.
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programme → say → sites
The aim is to give newly planted kelp enough room to survive and eventually reproduce.
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aim → give → room
What could happen if the young forests survive
The hope is not simply to keep a collection of planted kelp alive.
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hope → happen → kelp
Researchers want the young forests to produce their own spores and gradually establish patches that can expand naturally.
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that → want → patches
Researchers have also tested several ways of placing young kelp in the ocean, including lines attached to the seafloor, small stones carrying kelp and bags containing spores.
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Researchers → test → spores
A related California Sea Grant project has explored another approach called Green Gravel.
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project → explore → approach
In that work, young kelp spores were grown on small pieces of gravel that could potentially be spread from a boat, reducing the need for divers to place every piece individually.
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divers → grow → piece
California Sea Grant reported that researchers were also testing terracotta tiles that could be fixed to reefs and monitored more easily.
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that → report → reefs
Can laboratory kelp overcome the wider problem
The Greater Farallones Association’s latest results offer an encouraging sign.
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results → overcome → sign
Young bull kelp has already been observed growing after lab-raised material was returned to the ocean.
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material → observe → ocean
…and 3 more, not listed.
The Aporia
