Characterizing the Ecosystem Function and Biodiversity in the Anchialine Caves of the Caribbean Coast of the Yucatan Peninsula and Marine Caves of Belize

Abstract

Coastal subterranean estuaries are characterized by vertically stratified groundwater. Fauna inhabiting this ecosystem have high endemism rates, and is mainly composed by stygobionts (i.e., cave adapted species). Most species described from these ecosystems are based on morphology. However, almost no information is available on the microbial community, despite its important role in biogeochemical processes. Macrofaunal and microbial diversity are identified in this study using COI and 16S rRNA genes, respectively. The impact of climate change on subterranean estuaries is poorly known, although negative impacts due to temperature changes and precipitation have been documented. Subsequently, this study analyzes the influence of precipitation over the temperature of aquatic caves and their fauna on anchialine caves with direct connection with the ocean, and the resilience of this ecosystem in the Yucatan Peninsula and Cozumel Island. Lastly, this study identifies ecological patterns of the macrofaunal and sediment microbial communities from two adjacent subterranean estuaries. Molecular identification with COI revealed cryptic species of Antromysis, Metacirolana, Tulumella, Typhlatya, Stygiomysis and Xibalbanus. The remipede Xibalbanus cokei is recognized as a junior synonymy of X. tulumensis. Syntopic species of Typhlatya (five species), Xibalbanus (two species), and Stygiomysis (two species) were identified. The study of the effects of precipitation on the subterranean estuary determines that temperature of aquatic caves decreases 0.0068°C per mm of accumulated precipitation over four days. This means that the temperature has decreased 2.8°C due to precipitation at least 32 times in the last 70 years in Felipe Carrillo Puerto, Quintana Roo, Mexico. Changes in the macrofaunal community structure due to a mortality event in 2015 caused by heavy precipitation were not detected, while changes in the species densities occurred on marine species but not on stygobionts; thus, the anchialine fauna was resilient to this event. Analysis of the microbial sediment community concludes that they are homogenous in the subterranean estuary of Cozumel Island and the Yucatan Peninsula. A greater understanding of the link between external and internal environmental parameters of the subterranean estuary, and a better knowledge of the community structure, allow us to understand the implications of climate change and human impacts, allowing better management and conservation plans.