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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 (δ 15 N) 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 δ 15 N (Redang, +0.7‰) and Sinularia δ 15 N (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 δ 15 N trends. Potential damaging effects of sewage discharge on the coral reef communities at both islands are highlighted by strong correlations between Acropora δ 15 N and regional variation in coral reef community structure, and exclusive occurrence of degraded reefs at regions of high sewage influence., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

We investigated the potential of coral skeleton δ 15 N (CS-δ 15 N) records for tracking anthropogenic-N sources in coral reef ecosystems. We produced a 56yr-long CS-δ 15 N record (1958-2014) from a reef flat in Guam that has been exposed to varying 1) levels of sewage treatment 2) population density, and 3) land use. Increasing population density (from <30 to 300ind·km -2 ) and land use changes in the watershed resulted in a ~1‰ enrichment of the CS-δ 15 N record until a sewage treatment plant (STP) started operation in 1975. Then, CS-δ 15 N stabilized, despite continued population density and land use changes. Based on population and other considerations, a continued increase in the sewage footprint might have been expected over this time. The stability of CS-δ 15 N, either contradicts this expectation, or indicates that the impacts on the outer reef at the coring site were buffered by the mixing of reef water with the open ocean., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Nitrogen isotopes are widely used to study the trophic position of animals in modern food webs; however, their application in the fossil record is severely limited by degradation of organic material during fossilization. In this study, we show that the nitrogen isotope composition of organic matter preserved in mammalian tooth enamel (δ15Nenamel) records diet and trophic position. The δ15Nenamel of modern African mammals shows a 3.7‰ increase between herbivores and carnivores as expected from trophic enrichment, and there is a strong positive correlation between δ15Nenamel and δ15Nbone-collagen values from the same individuals. Additionally, δ15Nenamel values of Late Pleistocene fossil teeth preserve diet and trophic level information, despite complete diagenetic loss of collagen in the same specimens. We demonstrate that δ15Nenamel represents a powerful geochemical proxy for diet that is applicable to fossils and can help delineate major dietary transitions in ancient vertebrate lineages. Enamel-bound nitrogen isotopes in modern and fossil mammal teeth preserve dietary and trophic level information. This novel geochemical archive can be used to reconstruct trophic niche in ancient ecosystems. [ABSTRACT FROM AUTHOR]

The article presents the trophic strategy and bleaching resistance in reef-building corals. Topics include the trophic niches of different coral species and demonstrated that their nutrition varied considerably, the some species highly dependent on their photosynthetic algal symbionts and others able to feed on plankton to meet energetic requirements, and the use of this tool are necessary when it is applied to other scientific questions and symbiotic organisms.

Nitrogen isotope ratios (δ15N) are a well-established tool for investigating the dietary and trophic behavior of animals in terrestrial and marine food webs. To date, δ15N values in fossils have primarily been measured in collagen extracted from bone or dentin, which is susceptible to degradation and rarely preserved in deep time (>100,000 years). In contrast, tooth enamel organic matter is protected from diagenetic alteration by the mineral structure of hydroxyapatite and thus is often preserved over geological time. However, due to the low nitrogen content (<0.01 %) of enamel, the measurement of its nitrogen isotopic composition has been prevented by the analytical limitations of traditional methods. Here, we present a novel application of the oxidation-denitrification method that allows measurement of δ15N values in tooth enamel (δ15N enamel). This method involves the oxidation of nitrogen in enamel-bound organic matter to nitrate followed by bacterial conversion of nitrate to N 2 O, and requires ≥100 times less nitrogen than traditional approaches. To demonstrate that δ15N enamel values record diet and trophic behavior, we conducted a controlled feeding experiment with rats and guinea pigs (n = 37). We determined that nitrogen concentration in tooth enamel (x̄ = 5.0 ± 1.0 nmol/mg) is sufficient for δ15N enamel analyses with ≥5 mg untreated enamel powder. The nitrogen isotope composition of enamel reflects diet with an enrichment (Δ15N enamel-diet) of ca. 2–4‰. δ15N enamel values differ significantly between dietary groups and clearly record a shift from pre-experimental to experimental diet. The small sample size required (≤5 mg) by this method permits analyses of sample size-limited, diagenetically robust tooth enamel, and, as such it represents a promising new dietary proxy for reconstructing food webs and investigating the trophic ecology of extant and extinct taxa. • Nitrogen isotope analysis of ≤5 mg enamel with 'oxidation-denitrifier' method. • Nitrogen isotopes in tooth enamel record dietary and trophic behavior. • Tooth enamel is enriched in 15N relative to diet by ca. 2 to 4 ‰. • Plant- and meat-based diets are clearly distinguishable in enamel δ15N. • Nitrogen isotopes can also be measured in fossil tooth enamel. [ABSTRACT FROM AUTHOR]