Institute of Marine Research Norway - Lillehaven

Restoration Project

Institute of Marine Research Norway - Lillehaven

Restoration Objective:

This study developed and tested 'green gravel' with the aim of improving kelp forest restoration techniques. Restoring reefs using green gravel requires little investment and provides potential pathways to propagate resistant genotypes that could ‘future proof’ vulnerable kelp forests to future stress.

Site Selection Criteria:

The selected site was located in a semi-protected area with patchy kelp (2–20% canopy cover) and turf-dominated reefs and mainly coarse sedimentary substrate.

Cause Of Decline:

Kelp forests are declining globally and are increasingly being replaced by degraded turf reefs. These transformations are linked to effects of human activities such as ocean warming and eutrophication.

Key Reasons For Decline:


Scientific Paper

Green gravel: a novel restoration tool to combat kelp forests decline

M. A. Coleman, S. Fredriksen, K. Filbee-Dexter, K.M. Norderhaug, H. Steen, T. Bodvin, F. Moy, T. Wernberg
Scientific Reports.

Site Observations:

Observation Date

15th Jan 2019 – 15th May 2019

Action Summary:

Small rocks were seeded with kelp propagules (Saccharina latissima) and reared in the laboratory until 2–3cm (2.5 months), before out-planting to the field. The gravel was dispersed in three ways; by throwing it off the boat, placing it on the substrate or placing it in trays on the substrate. A second experiment was carried out where green gravel was deployed in habitats dominated by bare rock and turf, to compare success.

Lessons Learned:

Green gravel successfully grew kelps, and growth, length and survival were similar amongst deployment methods.

Project Outcomes:

Out-planted kelp had high survival and growth over 9 months, even when dropped from the surface. At 85 days after out-planting, 60% of the gravel in trays and 53% of the gravel in open plots retained kelp, and between 85 and 203 days 100% of the gravel retained kelp. Kelp growth and length was similar between treatments. In the turf/bare rock experiment, after 4 months, 18.5% (± 7.1 SD) of gravel held a kelp plant that was attached to the underlying rock or turf. There was no difference in attachment success on turf or bare rock.

Key Reasons For Decline:


Area of Restoration (Ha)


Indicator Data:


Ending Value:

Starting Value:

Percent Survival

Cost Year:2020
Cost Currency:USD
Total Cost:67,500