Ocean Transport Pathways to a World Heritage Fringing Coral Reef: Ningaloo Reef, Western Australia.

Jiangtao Xu,Nicole L Jones,Ryan J Lowe,Gregory N Ivey,Zhenlin Zhang,Stuart Humphries

doi:10.1371/journal.pone.0145822

Jiangtao Xu, Nicole L Jones + Show 4 more

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https://doi.org/10.1371/journal.pone.0145822

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Abstract

A Lagrangian particle tracking model driven by a regional ocean circulation model was used to investigate the seasonally varying connectivity patterns within the shelf circulation surrounding the 300 km long Ningaloo Reef in Western Australia (WA) during 2009–2010. Forward-in-time simulations revealed that surface water was transported equatorward and offshore in summer due to the upwelling-favorable winds. In winter, however, water was transported polewards down the WA coast due to the seasonally strong Leeuwin Current. Using backward-in-time simulations, the subsurface transport pathways revealed two main source regions of shelf water reaching Ningaloo Reef: (1) a year-round source to the northeast in the upper 100 m of water column; and (2) during the summer, an additional source offshore and to the west of Ningaloo in depths between ~30 and ~150 m. Transient wind-driven coastal upwelling, onshore geostrophic transport and stirring by offshore eddies were identified as the important mechanisms influencing the source water origins. The identification of these highly time-dependent transport pathways and source water locations is an essential step towards quantifying how key material (e.g., nutrients, larvae, contaminants, etc.) is exchanged between Ningaloo Reef and the surrounding shelf ocean, and how this is mechanistically coupled to the complex ocean dynamics in this region.

Highlights

Ningaloo Reef in Western Australia (WA) is the world’s largest fringing coral reef system and a United Nations World Heritage site that supports a wide range of habitats and a high diversity of marine organisms (Fig 1)
Using particle tracking driven by a regional ocean circulation model, this study focuses on identifying the key source regions of water that is advected both to and from Ningaloo Reef during different seasonal periods, including how various hydrodynamic mechanisms contribute to the observed transport
The present study focused on assessing how the transport pathways to/from Ningaloo Reef varied in different seasonal periods during 2009–2010, and while inter-annual variability in the regional ocean dynamics could modify these pathways on a year-by-year basis, we still expect these pathways to be generally representative of the longer-term seasonal variability that occurs in the region

Summary

Introduction

Ningaloo Reef in Western Australia (WA) is the world’s largest fringing coral reef system and a United Nations World Heritage site that supports a wide range of habitats and a high diversity of marine organisms (Fig 1). The ocean circulation surrounding Ningaloo Reef regulates how material (e.g., nutrients, larvae, etc.) and heat are exchanged between the reef and ocean, which in turn shapes the ecology of this reef system. Understanding the detailed transport pathways, including identifying the primary source and sink regions of the coastal water that exchanges with Ningaloo Reef, can help address many critical questions, such as: How. PLOS ONE | DOI:10.1371/journal.pone.0145822. Research Council Centre of Excellence for Coral Reef Studies (CE140100020). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

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