Effects of tourism-derived sewage on coral reefs: Isotopic assessments identify effective bioindicators

Last modified: 
December 13, 2019 - 12:35pm
Type: Journal Article
Year of publication: 2019
Date published: 11/2019
Authors: Liam Lachs, Nur Johari, Dung Le, Che Safuan, Nicolas Duprey, Kentaro Tanaka, Tan Hong, Nicolas Ory, Zainudin Bachok, David Baker, Marc Kochzius, Kotaro Shirai
Journal title: Marine Pollution Bulletin
Volume: 148
Pages: 85 - 96
ISSN: 0025326X

Pulau Redang and Pulau Tioman have experienced huge tourism growth over the last two decades, but minimal sewage treatment may threaten the resilience of their coral reefs. This study uses stable isotope techniques to identify suitable bioindicators of sewage nutrients (δ15N) at these islands by measuring macroalgae (Lobophora spp.), gastropods (Drupella spp.), scleractinian coral (Acropora spp.), and leather coral (Sinularia spp.). At tourist hubs using seepage septic tank systems, enrichment of Acropora δ15N (Redang, +0.7‰) and Sinularia δ15N (Tioman, +0.4‰) compared to pristine background levels indicate enhanced sewage nutrient discharge. Carbon isotopes and survey data suggest that sedimentation did not confound these δ15N trends. Potential damaging effects of sewage discharge on the coral reef communities at both islands are highlighted by strong correlations between Acropora δ15N and regional variation in coral reef community structure, and exclusive occurrence of degraded reefs at regions of high sewage influence.

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