Ecological Dynamics of Methane-Seep Foundation Species: Succession, Disturbance Response and Niche Stability

Deep-sea methane seeps host unique biological communities driven by chemosynthetic primary production, and are essential to both local and global functioning. Foundation species at these sites play a critical role in structuring seep ecosystems by providing habitat complexity and refugia for associated fauna. Despite their ecological importance, however, the successional dynamics of these communities, and their responses to environmental disturbance, remain poorly understood. This thesis investigates the abiotic niche requirements, successional patterns and resilience of foundation species communities at methane seeps along the Pacific Costa Rican Margin to enhance our understanding of the factors shaping these ecosystems. In Chapter 2, abiotic niches and inferred successional patterns of foundation species at the Mound 12 methane seep are assessed using photo-transect data coupled with maximum entropy (MaxEnt) modeling. Results support a successional framework in which bacterial mats and vesicomyid clams act as early colonizers, followed by bathymodiolin mussels and serpulids as intermediate successors, and vestimentiferan tubeworms and corals as late-successional stages. These findings provide empirical support for previously hypothesized succession stages and improve our understanding of how foundation species establish and persist through time. In Chapter 3, the potential impact of a magnitude 6.5 earthquake on the Mound 12 seep community is examined, using pre- and post-earthquake spatial mapping and MaxEnt modeling to track shifts in species distributions. Results reveal substantial changes in seepage activity, with vesicomyid clams displaying a notable capacity for migration in response to altered seepage patterns. This provides the first direct evidence of such movement in a methane-seep ecosystem, shedding light on potential pioneer species and the resilience of these communities to natural disturbances. In Chapter 4, the scope of this research is expanded to assess how seep community composition and abiotic niches vary across multiple sites along the Pacific Costa Rican Margin. By testing the transferability of MaxEnt models trained on Mound 12, varying degrees of niche stability were identified across sites, with Parrita seep and Jaco scar exhibiting strong similarity to Mound 12, while Mound 11 and Quepos slide show distinct community patterns driven by differences in seepage flow rates and oxygen conditions. These findings highlight the role of local environmental conditions in shaping seep communities and suggest that some sites may represent different stages of succession. Together, these studies provide new insights into the ecological processes governing methane-seep communities, demonstrating the importance of abiotic factors in structuring these systems and shaping their responses to disturbance. By improving our ability to predict how these ecosystems change over time, this research informs conservation strategies aimed at protecting methane-seep habitats from anthropogenic threats, such as hydrocarbon extraction and bottom trawling, which could substantially alter community dynamics.