Private links to watch again previous seminars can be given upon request, if authorized by the speakers, at early_career@dsbsoc.org.
19 May 2026 – Deep-sea coral reefs ecology and biodiversity
Beatriz Mejía-Mercado (Florida State University Coastal and Marine Laboratory)
From Basins to Seamounts: A Hierarchical Framework for Deep-Sea Community Structure.
Abstract: Deep-sea communities are often described in terms of biodiversity patterns, yet the processes structuring these assemblages across spatial scales remain incompletely understood. In this talk, I synthesize my research on how deep-sea communities are organized across basin and seamount systems. My work began in the Gulf of California, where ROV-based exploration revealed how geological complexity shapes biological patterns across deep basins. Subsequent analyses of benthic megafaunal assemblages across depth gradients showed strong structuring along environmental gradients, particularly under low-oxygen conditions. I then extended this research to seamount systems in the Northwestern Hawaiian Islands. At Necker Island and Pioneer Bank, assemblages varied with depth and seamount side, highlighting strong within-feature heterogeneity, and were further shaped by environmental and habitat variables such as dissolved oxygen, substrate composition, and rugosity, indicating that no single driver explains community organization. Across multiple seamounts, assemblages differed at similar depths, demonstrating that horizontal variation is a fundamental component of community structure. More recently, I have examined how observation itself shapes these patterns. Comparisons between AUV and HOV surveys show that each platform samples different components of the community, influencing biodiversity estimates and assemblage structure. At finer scales, habitat-forming corals further influence assemblages through fish associations,increasing local density and diversity. Together, these results led me to view deep-sea communities as a hierarchical, observation-aware system structured by interacting processes across scales, from basin gradients to seamount heterogeneity and habitat interactions, while also shaped by how we observe them. This perspective supports emerging imagery-based approaches for identifying Vulnerable Marine Ecosystems and highlights the need for consistent criteria for biodiversity assessment and conservation.
Manuja Hendawitharana (University of Barcelona)
Exploring the Hidden Biodiversity of Deep-Sea Vertical Reefs in the Galápagos.
Abstract: Vertical cliff habitats in the deep sea represent structurally complex environments that support diverse communities. These steep and often overhanging surfaces provide unique ecological niches shaped by depth, substrate composition, and hydrodynamic conditions. This study aims to unravel the drivers for biodiversity in the deep waters by focusing on a first description of vertical wall megafaunal communities in the Galápagos. This study characterizes megafaunal assemblages along vertical walls within the Galápagos Marine Reserve (GMR), using high-resolution ROV video transects collected aboard the R/V Falkor (too) during a 2023 expedition. A total of 123 morphospecies were identified across 1,332 m² of vertical habitat surveyed at five sites spanning depths from 400 to 700 meters. Multivariate analyses, including NMDS and cluster analysis, revealed that depth, substrate type, and geo-location interact at fine spatial scales to shape community structure. Beta diversity was primarily driven by species turnover, rather than nestedness, indicating the presence of discrete faunal assemblages across different bathymetric zones. Importantly, 31 Vulnerable Marine Ecosystem (VME) indicator taxa were recorded. These findings underscore the ecological importance of deep vertical habitats and highlight the need to integrate them into spatial planning and conservation frameworks, particularly in the GMR, where artisanal fishing is ongoing.
