The ecological structure of Laminaria hyperborea kelp forests along the North Sea coast of the United Kingdom

Abstract

While kelp forests play a crucial role in coastal ecosystems, providing habitat, supporting biodiversity, and contributing to carbon sequestration, their response to environmental perturbations, such as pollution, is not well understood. This thesis investigated the structure and ecological function of Laminaria hyperborea kelp forests along the understudied UK North Sea coastline, with a focus on the impacts of historic coal mine waste on kelp growth, productivity, and associated biodiversity (including microbiome). Field surveys were conducted to assess the structural characteristics and carbon standing stock of kelp forests in northeast England and southeast Scotland. The results indicate significant variation in kelp forest structure across depth gradients and small spatial scales. Kelp density, biomass, and length decreased with depth, while carbon standing stock varied across sites, highlighting the influence of local environmental factors. This work provides a baseline for kelp forests in understudied regions of the UK’s North Sea and gives evidence to suggest they are structured and function similarly to L hyperborea forests at similar latitudes. To investigate the effects of coal mine waste on kelp forests ecosystems, comparative studies were conducted between polluted and non-polluted sites. The results show that kelp forests affected by historic coal mine waste have largely recovered, with growth patterns and carbon contributions similar to unpolluted sites. However, holdfast-associated fauna exhibited reduced abundance and diversity in polluted areas. Whilst this was predominantly an effect of habitat volume, it suggests that there could be lingering ecological impacts that may be affecting broader ecosystem dynamics. Additionally, examination of the effects of historic pollution on the kelp microbiome showed that while bacterial taxa adapted to polluted sites were more abundant, the overall diversity, structure, and abundance of surface microbiomes were similar between polluted and non-polluted kelp forests. This research advances understanding of both natural and pollution-driven variability in L. hyperborea forests, demonstrating that while the structural recovery of kelp forests impacted by mining activities has been successful, biodiversity in some areas remains compromised. These findings underscore the resilience of kelp ecosystems but also highlight the ongoing need for conservation and management to protect these valuable habitats from historic and future environmental stressors.