Seascape connectivity shapes fish functional diversity, ecosystem functioning and resilience in subtropical coral reefs

Abstract

Animals support a diversity of ecological processes that are linked to the stability, condition and resilience of ecosystems. This means that metrics indexing the diversity of a food web should be linked to the delivery of these ecological processes; yet, how diversity relates to ecological functioning remains unclear in many ecosystems. Coral reefs are reliant on multiple processes to maintain resilience and support ecosystem services, yet are at risk globally from sedimentation, overfishing and climate change. We quantified how seascape connectivity and reef context shape the functional diversity of fish and two ecological processes across subtropical coral reefs in Moreton Bay in eastern Australia. We used baited and unbaited remote underwater video stations and a series of functional assays to determine how the functional composition of a food web and processes correlate with the seascape across 50 reef sites. Fish functional richness was driven by the distance to the estuary and nearby habitats. Communities were more functionally balanced in protected areas and more divergent on reefs with higher coral cover adjacent to mangroves. Ecological processes were driven by the distance to the estuary, critically highlighting no relationship with fish functional diversity. We also show that ecosystem functioning was greatest when distances to the estuary were greater than 25 km, resulting in more diverse and higher trophic level fish. Understanding the rate and distribution of ecological processes closely linked with ecological resilience and how these relationships are impacted by biodiversity and environmental attributes is key for optimising reef conservation and management.

Bibliographic Information