Reviving Giants Of The Invisible Forest
How an endangered Tasmanian kelp forest is helping scientists uncover the secrets to reforesting the ocean
By CSIRO
In partnership with Institute for Marine and Antarctic Studies and The Nature Conservancy
Giant kelp under heat stress by Stefan AndrewsOriginal Source: @ocean_imaging
An ocean forest in danger
As climate changes, and the ocean grows warmer, the seas around Australia's island of Tasmania are experiencing a devastating loss.
Towering forests of Giant Kelp once thrived in shallow waters surrounding the island...
Giant Kelp with fish by Stefan AndrewsOriginal Source: @ocean_imaging
But they have declined by 95% - and these majestic forests are still disappearing.
Giant Kelp by Stefan AndrewsOriginal Source: @ocean_imaging
A giant species
Giant Kelp (Macrocystis pyrifera) grows in cold, shallow seas around the world - growing taller than 50 meters! It anchors to the sea floor and its long, leaf-like blades grow toward the sunlight at the sea surface...
... buoyed by gas bladders at the base of each blade.
On Bellerive Beach (2023) by Matt MarrisonCSIRO
A giant among seaweed
Seaweeds are macroalgae but are similar in nature to plants. The three different groups of seaweeds – brown, red, and green – are named for the pigments they use to absorb sunlight at different ocean depths.
Giant Kelp is a brown seaweed.
Urchin barrens and diver by Stefan AndrewsOriginal Source: @ocean_imaging
A changing climate
Climate change is threatening the few remaining strongholds of Giant Kelp in Tasmania, bringing warmer, nutrient poor waters to the island. Giant Kelp is very sensitive to warmer water and vulnerable to attack by a sudden imbalance of sea urchins.
Weedy Sea Dragon (Phyllopteryx taeniolatus) by Stefan AndrewsOriginal Source: @ocean_imaging
No trees, no forest
Giant Kelp in the ocean are just like trees on land. Their forests are home to diverse and unique sea creatures - from seahorses and nudibranchs, to sea lions and baby fish.
Tasmania’s Giant Kelp forests are an endangered marine community. But there is hope...
Giant Kelp cuttings (2023) by Matt MarrisonCSIRO
A cycle of hope
Underneath its leaf-like blades, Giant Kelp produce zoospores, which settle on the sea floor and mature into gametophytes, the microscopic life stage of Giant Kelp. Divers take cuttings of the blades to grow gametophytes in their labs.
Let's take a look.
Giant Kelp gametophytes (2024) by Andrea WildOriginal Source: Institute for Marine and Antarctic Studies, University of Tasmania
A biobank to save the species
Under red light at 4 degrees Celsius, Giant Kelp gametophytes remain in stasis, i.e. a state of balance. Giant Kelp gametophtes can be stored in a biobank - which is just like a seed bank.
Giant Kelp biobank (2024) by Andrea WildOriginal Source: Institute for Marine and Antarctic Studies, University of Tasmania
Can you believe these glowing red vials are helping to save an entire ecosystem?
Microscopic Giant Kelp growing in multiwell plates (2023) by Eileeen LeeCSIRO
Cells for scientific study
At slightly warmer temperatures of 12 to 15 degrees Celsius, gametophytes will produce more cells for study. Here, blue light allows sperm from male gametophytes to fertilise egg cells from female gametophytes, forming baby Giant Kelp.
A male Giant Kelp gametophyte (centre) surrounded by Giant Kelp babies, under the microscope (2023) by Eileen LeeCSIRO
Under the microscope
Giant Kelp gametophytes are microscopic. Here, baby Giant Kelp are beginning to grow on female gametophytes surrounding a male.
Working with Giant Kelp (2023) by Matt MarrisonCSIRO
Understanding Giant Kelp genetics
Some strains of Giant Kelp are naturally more tolerant of warmer waters. Scientists are working to understand the complex genetics reasons behind this. They're also comparing the genetic differences between remnant forests of Giant Kelp around Tasmania.
Giant Kelp gametophytes (2023) by Matt MarrisonCSIRO
A chain of babies
Selected from the biobank are strains of Giant Kelp that are tolerant of warmer waters. Like growing plants in a nursery, Giant Kelp babies are grown in the lab until they are ready to be planted on lengths of string in the ocean.
Giant Kelp by Stefan AndrewsOriginal Source: @ocean_imaging
Planting a garden
During the first trial, tiny babies of Giant Kelp, less than one millimeter long, were planted in the ocean at sites off Tasmania's south-east coast. One year later, these babies were 12 meters tall!
Thin Giant Kelp by Stefan AndrewsOriginal Source: @ocean_imaging
Planting a forest
In 2022, Giant Kelp babies were planted in an area of reef in southeast Tasmania measuring 7,000 square meters. The result is a Giant Kelp forest - a new home for the sea creatures that live in this once vast habitat.
Giant kelp from the sky by Stefan AndrewsOriginal Source: @ocean_imaging
Restoring an ecosystem
By breeding Giant Kelp that is tolerant of warmer water and replanting it in the ocean, we hope to restore the entire marine community around Tasmania.
Anusuya Willis with Giant Kelp (2023) by Andrew WilsonOriginal Source: Google
Science and grassroots actions are important for addressing climate change - empowering individuals to forge a resilient environment for the future.
Story by Andrea Wild
The Tasmanian Giant Kelp Restoration Project is a partnership between The Nature Conservancy (TNC), the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS), Natural Resource Management South (NRM South) and CSIRO.
This TNC-managed project requires many levels of coordination and cooperation. Using a variety of sources TNC identifies sites most suitable for Giant Kelp restoration. IMAS grows Giant Kelp strains from remnant populations with the best chance of success for the site. CSIRO uses population genetics to ensure diversity and increase thermal tolerance traits to future-proof restored forests.
This Giant Kelp is then grown in the lab at IMAS for about six weeks before TNC and IMAS plant the Giant Kelp at the restoration sites using a proven technique developed by IMAS to attach the juvenile Giant Kelp to the seafloor. TNC, NRM South, and IMAS are using this experience to develop a nationwide roadmap to recovery for Giant Kelp forests.
