Coastal marine environments are important ecological, economic and social areas providing valuable services such as coastal protection, areas of recreation and tourism, fishing, climate regulation, biotic materials and biofuels. Marine renewable energy developments in the coastal environment are becoming a key objective for many countries globally. Assessing and monitoring the impacts of these developments on features, such as coastal biodiversity, becomes a difficult prospect in these environments due to the complexity of marine process at the locations in which these developments are targeted. This thesis explores the main challenges faced when assessing biodiversity in dynamic coastal environments, in particular those susceptible to high levels of turbidity. Various underwater camera techniques were trialled in reduced visibility environments including baited remote underwater video (BRUV), drop-down video and hydroacoustic methods. This research successfully refined BRUV guidelines in the North-East Atlantic region and identified key methodological and environmental factors influencing data collected BRUV deployments. Key findings included mackerel as the recommended bait type in this region and highlighting the importance of collecting consistent metadata when using these methods. In areas of high turbidity, clear liquid optical chambers (CLOCs) were successfully used to enhance the quality of information gathered using underwater cameras when monitoring benthic fauna and fish assemblages. CLOCs were applied to both conventional BRUV camera systems and benthic drop-down camera systems. Improvements included image quality, species and habitat level identification, and taxonomic richness. Evaluations of the ARIS 3000 imaging sonar and its capability of visualising distinguishing identifying features in low visibility environments for motile fauna showed mixed results with morphologically distinct species such as elasmobranchs much clearer in the footage compared to individuals belonging to finfish families. A combined approach of optical and hydroacoustic camera methods may be most suitable for adequately assessing coastal biodiversity in low visibility environments
