The Shifting Tide: Investigating If Tropical Micro-Tidal Zones Act as Diverse Ecotones with Small-Scale Spatial Diversity Analysis of Ophiuroidea and Echinoidea

Abstract

Introduction: Biodiversity is not static, and regions with high levels of temporal and spatial variation or ecotones, may be critical for maintaining high biodiversity. The micro-tidal zone or transition from marine to terrestrial environments is a region with high levels of temporal and spatial variation. Ophiuroidea and Echinoidea have physiological and behavioural adaptions which allow them to be abundant in the micro-tidal zone. There is little research on the diversity of Ophiuroidea and Echinoidea on small spatial and temporal scales within the micro-tidal zone. Methods: This study aims to determine the possibility of a micro-tidal zone acting as an ecotone through analysis of Ophiuroidea and Echinoidea spatial and temporal diversity. Ecological Data was collected along two transects in the micro-tidal zone of Half Moon Caye, Belize. Shannon diversity indices were calculated and used for conditional probabilities to assess biodiversity at various regions in the zone. Statistical analysis was done with the Kruskal-Wallis Test, linear regression, and Chi-square analysis. Results: Evidence suggests that A. punctulata differs from all other species in the distance from high tide, this corresponds to the high conditional probability close to shore compared to other species. A relationship was found between the distance from high tide and both abundance and species richness. O. appressa and E. lucunter abundance was determined to be dependent of the time of day, but this was independent for all other species. Discussion: Patterns in biodiversity suggest that the outer region of the micro-tidal zone has a higher species richness due to overlap with species adapted to deeper locations. Furthermore, there is evidence which suggests there may be differences throughout shallower portions of the micro-tidal zone, but further analysis needs to be done with consideration of the physical conditions in this region. In addition to spatial differences, there were differences seen depending on the time of day which may suggest that some species move out of the intertidal zone at night. Conclusion: This study indicates how the tropical micro-tidal zone may be a critical region acting as an ecotone, providing habitat for a wide range of species on different spatial and temporal scales.