| dc.description.abstract | The intertidal zone is a thermally complex and physiologically stressful environment. Mytilid mussels are ecologically and commercially important species, however, many intertidal populations live close to their upper thermal limits. The observed rise in seawater and air temperature and the increase in frequency and duration of heatwave events, as a result of climate change, is leading to mass mortality of intertidal mussel populations globally. Changes to climate are being observed in the UK, data analysed here found that the sea surface temperature during winter of 2020 was up to 2.9 °C warmer compared to the long term mean, between 1980 and 1999. Therefore, this study examines the impacts of climate change on the physiology and biogeography of UK Mytilus spp. and considers the indirect effects resulting from the response of their common predator, Nucella lapillus.
Analysis undertaken here on the Marine Biological Association’s Marine Biodiversity and Climate Change project reveals changes in the abundance of 20 populations of Mytilus spp. and 17 populations of Nucella lapillus has been observed around the UK coastline in the last two decades. The majority of the changes observed are declines in species abundance and were mostly located in the south west of England and northern Wales.
Correlative analysis with monthly mean seawater and air temperature was performed but did not reveal significant causal links between changes in climate with the observed abundance change. Therefore, biomimetic body temperature data was analysed to examine the intricate and individual interaction between organisms and their environment. When exposed to the same seawater and air temperatures UK mussels populations in the high shore experience body temperatures up to 12 °C warmer than mussels in the low shore and mussels attached to open rock surfaces experience body temperatures up to 19 °C warmer than those attached in under-hang, shaded, locations. Additionally, the analysis has shown that UK intertidal mussels attached to open rock surfaces are routinely experiencing temperatures above their thermally stressful threshold, defined in this study as 29 °C, for up to 9 hours in one day. However, further monitoring of intertidal populations and research distinguishing whether acute extreme temperature exposure or chronic low levels of thermal stress is needed to determine what is driving these population level effects observed in UK shores.
Analysis on data from observational fieldwork undertaken at 4 intertidal zones in the south-west of England demonstrates that the abundance and morphology of Nucella lapillus differs on a localised basis, influenced by local environmental variables and species composition.
This thesis demonstrates the complexity of the interactions between species and their environment in the intertidal zone and highlights to importance for future research to incorporate body temperature measurements in their analysis and to consider the indirect effects of species interactions on the physiological and biogeographic response of intertidal mytilid mussels to climate change. | en_GB |
