Through the eyes of a turtle: Linking behavior of green turtles (Chelonia mydas) to seagrass habitats as an indicator for seagrass ecosystem condition.

Seagrass meadows are an important marine habitat providing numerous vital ecosystem services, however, alterations in abundance of megafauna species can lead to imbalances in the seagrass ecosystem. Therefore, this research investigates whether the behaviour of green turtles can be linked to seagrass habitat conditions, and how the perceived risk associated with the presence of predators influence these dynamics, providing a novel perspective on trophic dynamics in seagrass ecosystems. Unlike previous studies that focused solely on turtle behavior, predator and turtle interactions, or seagrass health, this research integrated spatial, behavioural, and ecological data to explore their interdependence. A multi-scale approach was used, consisting of unmanned aerial vehicle (UAV) and in-water surveys, baited remote underwater video systems (BRUVS), Fastloc-GPS transmitters and turtle-borne camera tags. This study found that a landscape of fear was present at the three study sites (Half Sound, Savannah Sound South and Savannah Sound North), which influenced green turtle vigilance and spatial distribution behaviours. In particular, green turtles tended to stay in shallower waters performing shallow dives and exhibited modified surfacing behaviours and consistent scanning. Through behaviour-habitat analysis, strong associations between grazing behaviour and grazing patch habitats, resting including the novel burying behaviour and pioneer seagrass habitats, and no specific behaviours associated with long (ungrazed) T. testudinum habitats were found. Non-invasive measurements of seagrass features, in particular leaf narrowing, agreed with the conclusions inferred from the links between green turtle behaviours and seagrass habitats - that seagrass meadows at these sites were in good condition. This research demonstrates how combining spatial and behavioural ecology can be used to gain a deeper understanding of the dynamics in seagrass ecosystems, highlighting the importance of these trophic interactions within complex ecosystems such as seagrass habitats. The findings of this research provides valuable insight for designing effective policies and management strategies, including the necessity of predator conservation in maintaining ecosystem balance.