Macrofauna of soft sediments associated with cold seeps from the offshore Sinú basin, Colombian Caribbean

Cold seeps in the offshore Sinú Basin, Colombian Caribbean, sustain macrofaunal communities in soft sediments, driven by chemosynthetic energy from methane and sulfide. This study investigated macroinfaunal assemblages at 19 stations within a seepage field off the Gulf of Morrosquillo, at depths of 47–166 m. Sampling utilized a Box Corer and ROV assessments, with stations categorized by seepage signal intensity (High, Medium, Low, Blank) and sediment type (Mud, Sandy Mud, Muddy Sand, Sand). A total of 1414 individuals from 115 taxa across four phyla (Annelida, Arthropoda, Mollusca, Echinodermata) were recorded, with Annelida (33 %) and Crustacea (39 %) dominating. Key families, including Ampeliscidae (9.3 %), Syllidae (5.1 %), and Maldanidae (4.5 %), exhibited patchy distributions influenced by sediment grain size and geological features such as mud volcanoes and faults. Ecological indices revealed high richness (Margalef: 5.8), diversity (Shannon-Weaver: 4.1), and uniformity (Pielou: 0.9), indicating a resilient ecosystem. Cluster and ordination analyses identified two main station groups based on mud content (Group 1: 93–99 %; Group 2: 40–55 %), with significant dissimilarities driven by families like Syllidae and Caridea (ANOSIM R = 0.849, p = 0.1 %). BIO-ENV analysis highlighted mud percentage as the primary environmental driver (Rho = 0.747), with salinity, temperature, and depth as secondary factors. Methane concentration showed a moderate influence (Rho = 0.517). These findings underscore the role of sediment texture and local geomorphology in structuring macrofaunal communities, with implications for understanding cold seep biodiversity in the Caribbean.