Damselfishes alleviate the impacts of sediments on host corals.

T J Chase,M Y Hein,M S Pratchett,M J Mcwilliam,M O Hoogenboom,S B Tebbett

doi:10.1098/rsos.192074

T J Chase, M Y Hein + Show 4 more

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https://doi.org/10.1098/rsos.192074

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Abstract

Mutualisms play a critical role in ecological communities; however, the importance and prevalence of mutualistic associations can be modified by external stressors. On coral reefs, elevated sediment deposition can be a major stressor reducing the health of corals and reef resilience. Here, we investigated the influence of severe sedimentation on the mutualistic relationship between small damselfishes (Pomacentrus moluccensis and Dascyllus aruanus) and their coral host (Pocillopora damicornis). In an aquarium experiment, corals were exposed to sedimentation rates of approximately 100 mg cm−2 d−1, with and without fishes present, to test whether: (i) fishes influence the accumulation of sediments on coral hosts, and (ii) fishes moderate partial colony mortality and/or coral tissue condition. Colonies with fishes accumulated much less sediment compared with colonies without fishes, and this effect was strongest for colonies with D. aruanus (fivefold less sediment than controls) as opposed to P. moluccensis (twofold less sediment than controls). Colonies with symbiont fishes also had up to 10-fold less sediment-induced partial mortality, as well as higher chlorophyll and protein concentrations. These results demonstrate that fish mutualisms vary in the strength of their benefits, and indicate that some mutualistic or facilitative interactions might become more important for species health and resilience at high-stress levels.

Highlights

Positive species interactions play a critical role in community assembly, species coexistence and ecosystem function [1,2,3]
Sediment treatment colonies of P. damicornis hosting D. aruanus exhibited the lowest levels of accumulated sediment, which was twofold less than sediment treatment colonies hosting P. moluccensis, and nearly fivefold less than vacant sediment treatment colonies
This study demonstrates that the presence of coral-dwelling fishes reduces accumulation of sediment on host corals during high sedimentation conditions, and thereby moderates the localized tissue damage caused by sediments

Summary

Introduction

Positive species interactions play a critical role in community assembly, species coexistence and ecosystem function [1,2,3]. Corals) to looser associations whereby certain taxa derive benefit from others in close proximity (e.g. 2 plants–pollinators, and clownfish–sea anemones), both forming critical components of community interaction networks [2]. Many positive interactions arise from the ability of species to modify the local environment through nutrient enrichment or habitat modification, and ameliorate stress for the benefit of their neighbours [4]. Studies from a range of systems demonstrate that the role of positive interactions increases under high-stress conditions [5,6,7], and interaction networks may shift to a ‘survival mode’ with a greater reliance on mutualism and facilitation. A major challenge, is to understand how positive interactions are likely to fare in the face of global environmental change, and how they might help communities deal with these stressors

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