Abstract

Biodiversity is referring to the variety and variability of life, and encompassing ecologic, functional, and genetic diversity, among others. Despite the long history of research in Antarctica, little is known about the functional role that species have in the ecosystem and less about the intrinsic processes that occur within organisms that form habitats. These habitatforming organisms (e.g., seaweeds, ascidians, sponges) are able to modify the primary substrate for an abundant and diverse associated fauna, that may feed directly (e.g., herbivores on macroalgae) or indirectly (e.g., filter-feeders on ascidians or sponges). Some organisms take advantage of the irregularities of the bio-habitat to use them as permanent (sessile) or transient (mobile) shelter against predators. Interestingly, biogenic substrates can be used as homogeneous habitats, where the boundaries of the community are defined by the boundaries of the substrate itself. Therefore, these bio-habitats allow studying intrinsic community processes that could be responsible for the complexity at a local scale. Elucidating these key components and processes that shape community structure, is essential to assess the resilience of ecosystems against physical disturbances mediated by man and/or climate change. For this, food webs provide a simplified and useful model of how energy flows through these systems and how consumer-resource relationships structure the architecture of these ecosystems. Antarctic environments are recognized by high species richness, where suspension- and deposit-feeders dominate benthic habitats. However, the functional roles, the inter-specific interactions, and the distribution of traits remain unknown. Our research proposal is focused on the role of trophic interactions in the structure and dynamics of communities associated with biogenic substrates in Antarctic benthic ecosystems, and how relationships of size between producers and consumers determine the complexity of these food webs. This research program includes three approaches, each providing a unique source of information complementary to the others: i) stable isotopes to infer how energy flows within and between trophic levels; ii) DNA barcoding to accurately identify the inter-specific relationships between trophic levels; and iii) distribution of body size to assess its role as determinant of the intra- and inter-level community complexity. Together, provide a detailed, robust, and integrated research program to understand the functioning and structure of benthic food webs associated with biogenic substrates.