Context: Climate change is altering marine habitats such as kelp forests.

Underwater Arctic forests are expanding thanks to global warming.

What are Kelps? How do they survive underwater?

Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera.

Kelps have adapted to the severe conditions. These cool water species have special strategies to survive freezing temperatures and long periods of darkness, and even grow under sea ice.

In regions with cold, nutrient-rich water, they can attain some of the highest rates of primary production of any natural ecosystem on Earth.

Significance of kelps:

• Kelps function underwater in the same way trees do on land.
• They create habitat and modify the physical environment by shading light and softening waves.
• The underwater forests that kelps create are used by many animals for shelter and food.
• More than 350 different species – up to 100,000 small invertebrates – can live on a single kelp plant, and many fish, birds and mammals depend on the whole forest.
• Kelp forests also help protect coastlines by decreasing the power of waves during storms and reducing coastal erosion. 
• Kelp forests throughout the world play an important role in coastal economies, supporting a broad range of tourism, recreational and commercial activities.
• Kelp is a coveted food source in many countries, full of potassium, iron, calcium, fibre and iodine.
• In the Arctic, Inuit traditionally use kelp as food and wild harvest numerous species.

How climate change is leading to expansion of Kelps?

Genetic evidence reveals that most kelps reinvaded the Arctic from the Atlantic Ocean quite recently(approximately 8,000 years ago, following the last Ice Age). As a result, most kelps in the Arctic are living in waters colder than their optimal temperature. Ocean warming will also move conditions closer to temperatures of maximum growth, and could increase the productivity of these habitats.

As waters warm and sea ice retreats, more light will reach the seafloor, which will benefit marine plants. Researchers predict a northern shift of kelp forests as ice retreats.

Concerns:

Other changes are happening in the Arctic that complicate this picture. In Canada, Alaska, Greenland, Norway and Siberia, permafrost soils that have been frozen for thousands of years are receding by half a metre per year. Thawing permafrost and crumbling Arctic coasts are dumping sediments into coastal waters at alarming rates, which blocks light and could limit plant growth.

The run-off from melting glaciers will also lower salinity and increase turbidity, which impacts young kelp.