Seascape connectivity modeling predicts hotspots of fish-derived nutrient provisioning to restored coral reefs

Abstract

Coastal habitat quality and quantity have been significantly eroded by stressors operating and interacting across the land-sea interface, prompting a recent proliferation in coastal restoration programs worldwide. These initiatives often recognize connectivity as a critical driver of ecosystem functioning, yet most do not include connectivity as a spatially explicit, quantitative criterion during the planning process. Here, we demonstrate the use of spatial graph models to quantify potential functional connectivity for 2 multi-habitat-utilizing reef fish species known to transport nutrients from nearshore mangrove and seagrass nurseries to oligotrophic offshore reefs. Applying the method across sites considered by a multi-million dollar coral restoration program in the Florida Keys, USA, revealed locations where out-planted corals are likely to benefit most from enhanced functional connectivity in the form of nutrient provisioning and other consumer-driven processes. Opportunities for positive fish-coral interactions varied between fish species, owing to selective patterns of habitat use, highlighting the need for species-specific connectivity assessments, even within a trophic guild. Connectivity estimates for candidate restoration sites were influenced more strongly by habitat composition (which influences fish foraging and shelter resources) than by proximity to potential mangrove and seagrass nurseries, emphasizing the importance of considering both seascape composition and configuration in restoration design. Ecologically and economically effective restoration strategies are urgently required to curb rapid declines in coral reef architectural complexity, ecological function, and resilience. Our study illustrates the utility of spatial graphs as a data- and resource-efficient technique for quantifying and communicating complex ecological connectivity information in service of such efforts.