Underwater forests are an immensely important ecosystem: they support biodiversity, improve water quality and sequester carbon. Despite their significance for marine life and the fight against climate change, the loss of kelp forests from coastlines worldwide has captured much less of the spotlight on deforestation.
This is why since 2020 we have been working with SeaForester to restore kelp forests in Portugal where large areas of kelp have disappeared. So far, reversing this trend has been difficult. One of the challenges is that restoration efforts tend to require extensive diving which quickly becomes costly and time-consuming.
However, we have renewed optimism through a new technique called “green gravel” that tackles this challenge making large-scale marine reforestation possible. It involves growing kelp attached to pebbles in a lab before deploying them at suitable locations in the ocean without the need for divers. For this project, we are building a kelp nursery that will allow us to test this method on a larger scale.
Results of our first kelp restoration trial
Our ultimate goal is to make large scale restoration of kelp forests a reality in Portugal and our first step in this direction was the kelp restoration trial we started with SeaForester in Cascais in November 2020. We deployed spores from healthy kelp populations into 3 sites. The results so far suggest that this spore bag technique will not work in this area, possibly because of the presence of turf algae that outcompete the kelp for rock surface. Although we were disappointed with the result, the information we got out of the project is valuable and is already helping guide our next steps.
A new technique and successful trials
Green gravel is a kelp restoration technique that was recently developed by the Norwegian Institute for Marine Research (IMR). It involves seeding pebbles with kelp in a lab, allowing the kelp to grow under optimal conditions and only then deploying them in the ocean. The potential is huge because this technique can overcome many of the challenges facing current kelp restoration methods.
Since pebbles can just be dropped from a boat, large areas could be restored without the need for more costly and time-consuming scuba diving work. What’s more, since the kelp is already attached to a substrate (the pebbles) it may grow well even if the underlying reef is degraded and covered in turf algae. The technique worked well in turf-covered reefs in Norway so we hope it will also be useful in addressing this problem in the areas in Cascais where releasing kelps spores is not proving to be enough to bring the kelp back.
The method is now being trialled in more than 10 locations across the world in a collaborative effort coordinated through the Green Gravel Action Group. In Portugal, the SeaForester team, including researchers from the Marine and Environmental Sciences Centre - Politécnico de Leiria, have successfully used the technique in small scale trials. Individuals of the golden kelp, Laminaria Ochroleuca, have been successfully deployed on the ocean floor and have grown well over several months. This is very encouraging and means that we are ready for the next step!
Scaling things up
Given the success of the initial trials in Peniche and the great potential of green gravel as a marine reforestation technique, we decided to scale things up. With the support of our Mossy Earth members as well as Not Just Travel, Get Set Hire, Unifrog and WSL Pure, we managed to get the funds needed to build a kelp nursery that will greatly increase the green gravel production capacity in Portugal.
This amounts to a total of 80 boxes which we are mounting in a shelf system which allows each of them to maintain about 200 to 400 pebbles under optimal conditions for the kelp to grow in the lab. Each box is illuminated by an LED light that switches on and off to simulate night and day cycles. Water flows through the boxes and is filtered and cooled so that it is kept suitable for kelp growth.
Once it is built, the goal is to have the kelp nursery running year-round with a new batch of kelp pebbles being ready to deploy every 2 to 3 months. Each cycle begins by spraying the pebbles with microscopic immature life stages of the kelp which attach to the pebbles and start growing. To avoid the need to collect this starting material from wild populations every time we are also building a lab setup that allows us to keep a seedstock available year-round. This is a modified fridge contraption that allows the feedstock to be kept at the necessary light and temperature conditions. This makes it much faster and cost-efficient to start each production cycle because it is no longer necessary to find and collect material from wild kelp populations every time.
Altogether this will allow the green gravel technique to be tested at a much larger scale in Portugal!
Learn more about the context behind this project
Disappearing seaweed forests
The world’s shallow coastal areas, where sunlight penetrates, are the cradles of the ocean. Here seaweed forests grow supporting a rich and diverse assemblage of marine fauna and flora by providing highly productive three-dimensional habitats. In addition to reducing the loss of biodiversity in oceans, kelp forests also provide ecosystem services by reversing acidification, an important part of climate change mitigation.
Unfortunately, European seaweed forests are disappearing at an alarming rate. Although we lack the data to figure out the actual causes for this decline, these are likely to be important drivers in many areas:
- Water pollution
- Climate change affecting water temperatures
- A build-up of sediment as a result of both human and natural causes
- Increases in herbivory rates due to overfishing and its impact on coastal ecological communities
- Increased storm intensity
Pioneering seaweed restoration work in Europe
Unlike land-based deforestation which has received a lot of attention, the loss of marine forests tends to go mostly unnoticed. This may be due to the fact that the underwater world is out of sight for most of us and its deterioration is therefore not as obvious. As result, there are still very few seaweed restoration projects in Europe and there is a great need to develop greater know-how in this area. This is where our partnership with SeaForester comes in to restore these 'forgotten forests'. SeaForester is an initiative that aims to reverse the alarming disappearance of seaweed forests in the world in order to safeguard the oceans’ vital role of carbon sequestration, maintaining fish stocks and securing the planet’s wellbeing. By joining forces with them in Portugal, we aim to make the large-scale restoration of kelp forests a reality here.
Sources & further reading
- “Green gravel: a novel restoration tool to combat kelp forest decline. ” - Fredriksen, S., Filbee-Dexter, K., Norderhaug, K.M. et al., 2020
- “Ecosystem Engineers, Keystone Species” - de Visser S., Thébault E., de Ruiter P 2012