Despite the obvious importance of marcoalgae in oligotrophic seas as primary producers their role in sustaining biodiversity and secondary production has thus far only received limited attention. Most research effort to date has been concentrated on shallow water species, in particular sea grasses, while other algae communities in deeper waters (50-100 metres), that are equally widespread but morphologically and chemically very different, have received far less attention. As a consequence little information exist about these habitats, their productivity, biodiversity of associated benthic fauna and how energy is transferred from the algae to higher trophic levels such as fish. The few descriptive studies of these habitats that do exist do, however, indicate a strong link between algae beds and an abundant and diverse fish fauna. A key aim of the ecosystem approach to fisheries management is to identify, conserve and restore habitats critical to fish in order to regenerate and sustain fish populations. Thus knowledge of habitat – fish associations as well as the mechanistic link between them will be an important component towards implementing this approach. Within this fellowship application it is proposed to study the demersal community and food-web structure of three algal model systems, one shallow water system (Cystoseira) and two deep water (Osmundaria - Phyllophora and Peyssonnalia) systems that have a widespread occurrence in the Mediterranean by adopting a multidisciplinary approach, combining traditional benthic community ecology with stable isotope techniques and field as well as laboratory experiments. Furthermore, food-web modelling approaches will be adopted to integrate these results into a wider ecological framework. The expected outcome of the proposal is to increase our understanding of the ecology of macroalgae habitats in the Mediterranean and the role they play in sustaining fish production.