Coastal climate resilience: exploring the value of geodiverse and biodiverse hotspots
The degree of ecological change imposed by climate change on marine species and habitats is of increasing concern (Halpern et al., 2008), and the Intergovernmental Panel on Climate Change (IPCC 2021) warns that limiting global warming to 1.5°C is looking increasingly unachievable. For intertidal and near-coast species, the concomitant increased air and sea temperatures have broad deleterious effects. However, the problems are exacerbated when the suite of co-occurring stressors of increased storminess, sea level rise and urbanisation are considered. These latter will result in a continued proliferation of coastal protection. Such structures have significantly lower biodiversity than equivalent natural habitats. A greater understanding of geodiversity-biodiversity interactions could be used to mitigate climate change risks for marine species, and to increase resilience in intertidal/shallow coast species through enhanced design of appropriate coastal engineering structures.
The novelty of this PhD would be the coupling of both rock material and rock mass properties to assess the combined benefits of geodiversity-biodiversity interactions for improving the climate resilience of marine ecological communities. Creation of a biodiversity ‘risk assessment’ tool is proposed – identifying places at high risk of climate-related stress and those at lower risk, which could become biodiversity climate refugia. The information would underpin design guidelines for eco-engineering practitioners.
This project will address four key research gaps:
1. Managing thermal stress through geodiversity-biodiversity interactions A: rock material and rock mass
Thermal variability of rocky shore systems, driven by wind speed, the tidal cycle, micro-topography, air temperature and solar radiation, can cause body temperatures to fluctuate by >20°C within a few hours and differ significantly between individuals only centimetres apart (Denny et al. 2011, Helmuth et al. 2011). The role of thermal stress has been explored in field-based experimental studies by manipulating temperatures (e.g shading; transplanting individuals across intertidal heights; direct application of heaters), or via thermal properties of differing artificial substrates (colour, material type). What has been less studied is how rock material properties can buffer/mitigate risks of desiccation/thermal stress (e.g. light coloured porous rocks) or increase these risks (e.g. dark rocks with low porosity). To date eco-engineering research has not directly explored links between climate change pressures on organisms (e.g. thermal stress/desiccation risk at low tide) and the types of materials used in experimental studies or operational applications. Similarly, rocky shore geology and geomorphology create topographic complexity on natural rocky shores – creating habitat niches for other species, which is often thermally more sheltered/moister. What is unknown is how these habitat niches provide climate refugia, and how the combination of rock material and rock mass features can create climate resilient biodiversity hotspots in nature, and how we can eco-engineer structures to better mimic this. A combination of field and lab experiments would be designed to test for differences in (i) body temp (ii) survivorship (iii) in situ micro-humidity (iv) growth or fecundity.
2. Reducing thermal stress for ecology via microbial geodiversity-biodiversity interactions
Marine microbial communities are known to greatly differ on different rock materials, and in some porous, calcium-rich materials like limestone, the microorganisms alter the rock materials. In as little as 8-months in a temperate region, cyanobacteria can bore into rock, increasing the porosity and water holding capacity of the rock masses. This has benefits for intertidal species as the rocks retain more moisture through the tidal cycle, reducing risks of thermal pressures. These interactions are poorly studied globally and the benefits they can provide in certain rock materials for intertidal ecology are weakly understood. Novel microcosm studies will be developed to trace active microbial communities as they interact with different rock substrates, acting as biogeomorphic ecosystem engineers gradually creating habitat refugia in some rock types but not others. This will provide information on the most effective microbial-rock interactions, and it will help to inform on the best eco-engineering approaches to consider.
3. Protecting ecology and assets with thermal blankets – what are the risks and benefits?
Organisms, like seaweeds, are known to act as thermal blankets helping to reduce thermal stresses for other species at low tide. They have also been shown to reduce the erosion of rock materials in laboratory experiments. Asset deterioration is a major climate change risk to hard coastal structures – and costs to repair structures is expected to increase 5-8X! What is poorly known is the biotic-microbial-rock interactions operating underneath these thermal blankets, and also how we can eco-engineer structures to encourage thermal blanket species. A suite of multidisciplinary methodologies will be developed to investigate the impact of thermal blankets. Microscopy, mescocosms and field analyses will be combined to test a variety of thermal blankets, and to explore the conditions that enhance the rate of blanket development and the efficiency of these covers.
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Natural Rocky Shore,Rock biotic interactions,Thermal blankets