Atoll-scale patterns in coral reef community structure: Human signatures on Ulithi Atoll, Micronesia.

Nicole L Crane,Kristin Precoda,Peter Nelson,John Rulmal,Michelle Paddack,Avigdor Abelson,Giacomo Bernardi,Heather M Patterson

doi:10.1371/journal.pone.0177083

Abstract

The dynamic relationship between reefs and the people who utilize them at a subsistence level is poorly understood. This paper characterizes atoll-scale patterns in shallow coral reef habitat and fish community structure, and correlates these with environmental characteristics and anthropogenic factors, critical to conservation efforts for the reefs and the people who depend on them. Hierarchical clustering analyses by site for benthic composition and fish community resulted in the same 3 major clusters: cluster 1–oceanic (close proximity to deep water) and uninhabited (low human impact); cluster 2–oceanic and inhabited (high human impact); and cluster 3–lagoonal (facing the inside of the lagoon) and inhabited (highest human impact). Distance from village, reef exposure to deep water and human population size had the greatest effect in predicting the fish and benthic community structure. Our study demonstrates a strong association between benthic and fish community structure and human use across the Ulithi Atoll (Yap State, Federated States of Micronesia) and confirms a pattern observed by local people that an ‘opportunistic’ scleractinian coral (Montipora sp.) is associated with more highly impacted reefs. Our findings suggest that small human populations (subsistence fishing) can nevertheless have considerable ecological impacts on reefs due, in part, to changes in fishing practices rather than overfishing per se, as well as larger global trends. Findings from this work can assist in building local capacity to manage reef resources across an atoll-wide scale, and illustrates the importance of anthropogenic impact even in small communities.

Highlights

Our study demonstrates a strong association between benthic and fish community structure and human use across the Ulithi Atoll (Yap State, Federated States of Micronesia) and confirms a pattern observed by local people that an ‘opportunistic’ scleractinian coral (Montipora sp.) is associated with more highly impacted reefs
It has been more than a decade since large-scale and long-term studies began to empirically document the global deterioration of coral reef communities from processes such as largescale bleaching, overfishing, high nutrient loads, crown-of-thorns starfish (COTs) invasions, and other perturbations [1]
Human use of coral reefs has profound effects on reef community structure, and, in combination, these factors can drive observable patterns in coral reef assemblages over a variety of spatial scales [7,9]

Summary

Introduction

It has been more than a decade since large-scale and long-term studies began to empirically document the global deterioration of coral reef communities from processes such as largescale bleaching, overfishing, high nutrient loads, crown-of-thorns starfish (COTs) invasions, and other perturbations [1]. Coral reef assemblages vary across large geographic scales, as well as in response to more localized oceanographic factors including currents, salinity, temperature, exposure, and access to biotic recruitment pools [2,15]. Few studies have characterized coral reefs across atoll-wide scales in regions where human populations are small but extractive activities have been prevalent for thousands of years (but see [4,16,17]).

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Conclusion