BENTHIC FORAMINIFERAL ASSEMBLAGES IN KARST SUBTERRANEAN ESTUARIES OF THE YUCATAN PENINSULA, MEXICO

Formed by the mixing of precipitation, saline groundwater, and oceanic water, karst subterranean estuaries (KSEs) are environments with interesting fauna and biogeochemical processes. The mixing of water masses within KSEs creates two distinct haloclines, a characteristic that often causes steep biogeochemical gradients. This provides a unique opportunity to study the ecology and diversity of organisms inhabiting a range of physico-chemical gradients (e.g., oxygen, salinity, light). Within the Yucatan Peninsula, Mexico, over 1,000 kilometers of coastal caves have been explored. Initial research in these systems focused on fauna within the water column, primarily stygobitic (cave-adapted) crustaceans. Very little is known about the role of the benthos in KSEs, including benthic meiofauna (organisms between 45µm-1mm in size). Within this group are benthic foraminifera, microbial eukaryotes that often dominate benthic meiofaunal communities, being nearly ubiquitous in marine settings and capable of inhabiting varied “extreme” environments (e.g., hydrothermal vents, methane seeps, anoxia). Benthic foraminifera are well-known environmental indicators that have been used in environmental reconstructions within select KSEs, yet very little is known about the diversity of their living assemblages. Results from surface sediment samples collected from several coastal caves in the Yucatan Peninsula and Cozumel Island will be presented. The fluorogenic probe CellHunt Orange was used to determine metabolically active foraminiferal assemblages. This research aims to create a baseline for benthic foraminiferal biodiversity in Yucatan/Cozumel KSEs, helping to inform paleoclimate studies. This work is part of a larger project assessing the drivers of benthic meiofaunal diversity and their role in ecosystem functioning. Funded by NSF OCE 2136377 and 2136322.