Identification of coral spawn source areas around Sekisei Lagoon for recovery and poleward habitat migration by using a particle-tracking model

Satoshi Mitarai,Yusuke Uchiyama,Motohiko Kashima,Sachika Odani,Yuki Kamidaira,Naoya Takeda

doi:10.1038/s41598-021-86167-5

Abstract

A massive coral bleaching event occurred in 2016 in the interior of Japan’s largest coral lagoon, the Sekisei Lagoon, located in the Kuroshio upstream region in southwestern Japan. Recovery of the coral lagoon will require the influx of coral spawn and larvae; therefore, it is important to identify and conserve source sites. A surface-particle-tracking simulation of coral spawn and larvae was used to identify source areas of coral spawn outside of the Sekisei Lagoon for potential recovery of the interior lagoon. The northern coastal zone of Iriomote Island, including Hatoma Island, was identified as a major source area. Hatoma Island was also identified as a key source for the Kuroshio downstream region and for aiding the poleward migration of coral habitat under ongoing global climate change, making it one of the most important source areas in the Nansei Archipelago.

Highlights

Corals are an integral part of the coral reef ecosystem and are a major tourism resource in the Nansei Archipelago, a string of islands in southwestern Japan located between Kyushu and Taiwan (Fig. 1)
Coral reefs regenerate through the influx of coral spawn and larvae especially from upstream regions; this means that the recovery of corals in the Sekisei Lagoon is a necessary first step toward the recovery of the entire Nansei Archipelago and for aiding poleward migrations of coral habitat under the influence of ongoing global climate change
We used submesoscale eddy-resolving synoptic ocean models based on the Regional Oceanic Modeling System (ROMS) in a double-nested configuration coupled with a 3-D Lagrangian particle-tracking model embedded in the Japan Coastal Ocean Predictability Experiment 2 (JCOPE2)[4]

Summary

Introduction

Corals are an integral part of the coral reef ecosystem and are a major tourism resource in the Nansei Archipelago, a string of islands in southwestern Japan located between Kyushu and Taiwan (Fig. 1). The lagoon is thought to help maintain coral reef ecosystems across the entire archipelago by supplying coral spawn and larvae to downstream sites (i.e., relatively northern regions of the archipelago). Corals in this lagoon were impacted considerably by a massive bleaching event in 2016, some 18 years after the 1998 event that hit Okinawa Island. Our current study aims to identify major source areas for (1) the interior Sekisei Lagoon, and (2) the entire Kuroshio downstream region, (and for aiding the poleward coral habitat migration) by using 3-D Lagrangian particle-tracking s imulations[4]. ROMS-L1 1 Jan 2005–2 Nov 2015 768 × 768 (× 32 Layers) 3 km 240 s QuikSCAT-ECMWF (daily, until 31 Dec 2007) JMA GPV-GSM (daily, 1 Jan 2008 and later) NOAA COADS (monthly climatology) JCOPE2 (20-days averaged) Monthly climatology[11] JCOPE2 (daily) JCOPE2 (10-days averaged) Not Used SIO SRTM30_Plus

Methods

Results

Conclusion