The science behind GEcoKelp
What are kelp forests?
Kelp, large brown macroalgae primarily of the Order Laminariales, are found in temperate and subpolar regions and extend along almost one third of the world’s coastlines. Here they form forests that represent the largest marine biome on the planet, covering approximately 2 million square kilometers (5x more than coral reefs). These forests are among the most diverse and productive marine ecosystems on Earth, providing habitat for a vast array of marine species and ecosystem goods and services (e.g. carbon sequestration, fisheries) worth billions of dollars annually.
Threats to kelp forests
Despite their importance, kelp forests are at risk of degradation and decline as a result of climate change (e.g. ocean warming and marine heatwaves) and human activities (e.g. over-fishing, pollution). Globally, more than 50% of ecoregions with kelp forests have seen declines over the last five decades. Understanding how these stressors influence kelp forests ecosystems is vital to provide science-based management strategies to protect, preserve and restore these key ecosystems and their associated goods and services for the future.
Stressor: Coastal Darkening
Coastal darkening refers to the phenomenon where coastal waters become less clear and more shaded due to an increase in organic matter, pollutants, and sediments, often driven by human activities like deforestation, agriculture, and urban runoff. This reduction in light can impact marine ecosystems, particularly kelp forests that rely on sunlight for photosynthesis. As coastal waters darken, kelp forests receive less light making it harder for them to survive and grow meaning they could be taken over by species that are less dependent on light, such as seaweed turfs.
Norwegian kelp forests
Kelp forests are a dominant marine habitat along the coast of Norway, extending from the Arctic to temperate regions. This gradient provides a unique natural laboratory to test the influence of climate change and human activities (e.g. fish farming) on kelp forests, particularly the commercially important sugar kelp (Saccharina latissima) and the ecologically important Tangle/Cuvie (Laminaria hyperborea). For example, recent research has linked declines in sugar kelp and shifts to turf seascapes over the last two decades in southern Norway to increases in the frequency and intensity of marine heatwaves.
Stressor: Ocean Warming & Marine Heatwaves
The most harmful effects of climate change in the oceans are warming waters and marine heatwaves. Nearly all oceans have seen rising temperatures and periods of extreme heat over the last 50 years. These rapid changes can stress on marine life, both directly through heat exposure and indirectly by affecting ecological processes such as grazing and competition. Kelp, thrive in cooler waters and generally respond negatively to warmer waters, particularly in areas towards the warm edge of their distribution.
Stressor: Rise of turf algae
In areas where kelp forests are being degraded and/or lost due to rising ocean temperatures, they can be replaced by dense mats of small, fast-growing turf seaweeds that smother the reef and trap sediments. Unlike kelp forests, these seaweed turfs offer little in the way of three-dimensional structure and dramatically altering the underwater landscape. The thick layer of sediment they accumulate makes it nearly impossible for new kelp to recruit and prevents kelp forests from regrowing and allowing turfs to dominate the area.
Seascape Genomics
Genetic variation is the central pillar of evolution. It holds information about past demographic changes and provides the means for individuals to adapt to environmental changes. Understanding variation in genetic diversity, structure and gene flow across a species' distribution is essential for developing effective conservation strategies. Recent use of genomic tools has allowed a insight at kelp’s adaptive potential by identifying loci under selection to local environments and predicting kelp’s genomic vulnerability to climate change. The increasing availability of kelp reference genomes is unlocking new powerful pathways for assessing adaptation and translating genomic results into management and conservation practices.
Life cycle
Kelp has biphasic life cycle, where sexual reproduction between male and female microscopic gametophytes leads to the formation of new kelp sporophytes. Despite playing a critical role in the persistence of kelp forests, many fundamental questions regarding kelp microscopic life stages remain. Scientists have used gametophytes to grow kelp under controlled conditions and study the effects of environmental changes on kelp physiology. Today, the use of gametophytes combined with population genomics approaches offers new ways to study adaptation, while also offering a way to preserve natural genetic diversity, both in wild and cultivated kelp.