The structure, resilience and restoration of kelp forests

  • Hannah Earp

Student thesis: Doctoral ThesisDoctor of Philosophy


Kelp forests are among the most dynamic, diverse, and productive ecosystems on Earth, where they modify local environmental conditions, facilitating the development of species rich communities. However, in many areas, kelp forests have been degraded and/or lost as a result of multiple stressors that often interact. Consequently, interest in restoring kelp forests is increasing. Here, I investigated spatiotemporal variation in and the drivers of understorey macrofloral and macrofaunal assemblages within Laminaria hyperborea forests across four regions along the north and west coasts of the UK, spanning 9° latitude and encompassing a mean sea surface temperature (SST) gradient of ~2.5°C. I showed that understorey assemblages represent an important component of UK kelp forests and that they are shaped by complex interactions between SST, wave exposure and habitat structure. I also explored temporal variation in the structure of L. hyperborea forests and their understorey assemblages along the northeast coast of the UK over the 2021/22 northeast Atlantic storm season. I found that these systems appeared to exhibit a degree of resilience to storm impacts, but that there were significant changes in the cover and composition of the kelp forests and the structure of understorey assemblages following the storm season and suggest continuous monitoring of these kelp forests to better understand temporal variability and trajectories of recovery. Regarding restoration, I investigated the success of marine forest restoration through a systematic review and meta-analysis, finding that restoration positively influences the abundance and morphology of target species. I also identified a lack of monitoring of environmental variables, limited comparisons across species, techniques and environmental contexts, and little information regarding restoration impacts on associated assemblages. I then tested the applicability of a novel kelp restoration tool, ‘green gravel’, seeded with Saccharina latissima, on wave-exposed shores along the northeast coast of the UK. I found that larger rocks were more likely to be retained than smaller rocks, and that seeded kelp were able to survive and grow in a comparable manner to naturally occurring sporophytes, however all rocks were lost from the restoration sites eight months after outplanting. As such I provide important insights for developing this technique. Overall, my thesis provides a greater understanding of
the structure, variability and drivers of UK kelp forests and their associated understorey assemblages, as well as insights into the emerging field of kelp forest restoration.
Date of Award2023
Original languageEnglish
Awarding Institution
  • Aberystwyth University
SupervisorPaul Shaw (Supervisor)

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