Scleractinian coral (Cnidaria, Hexacorallia, Scleractinia) diversity of the Mersing Islands, Peninsular Malaysia

We present a comprehensive checklist of scleractinian (hard) corals for the Mersing Islands, Malaysia based on surveys conducted at 24 reefs across protected and unprotected marine areas. A total of 261 species of corals from 16 families and one incertae sedis (Pachyseris spp.) were recorded, along with ten records that are new for the east coast of Peninsular Malaysia. Compared against the IUCN Red List, 46.7% of coral species found in the Mersing Islands were of Least Concern (LC), 29.5% as Near Threatened (NT) and 16.4% Vulnerable (V). Only one recorded species, Pectinia maxima (Moll & Best, 1984), was listed as Endangered (EN). Baseline species diversity data are essential for the monitoring and management of marine biodiversity, especially within marine protected areas. With both protected and unprotected coral reef areas in the vicinity of the widely scattered Mersing Islands, the diversity and distribution of coral species can be used as the basis for area-based conservation and management strategies. The diversity and abundance of scleractinian corals of each island or area should be surveyed periodically to ensure the appropriate level of protection is afforded to retain scleractinian biodiversity in this region

Simultaneous analysis of Ba and Sr to Ca ratios in scleractinian corals by inductively coupled plasma optical emissions spectrometry

Chemical analyses of coral skeletons are useful for reconstructing past ocean conditions. Simultaneous measurements of Ba and Sr to Ca ratios in coral samples have predominantly been achieved by inductively coupled plasma mass spectrometry (ICP-MS). We demonstrate a method that expands the application of the inductively coupled plasma optical emissions spectrometry (ICP-OES) technique to precisely analyze Ba, Sr, and Ca simultaneously. Analytical drift and matrix interferences at a range of Ba/Ca ratios (3–10 μmols/mol) were explored to determine the efficacy of standardized corrections. Minor disparity in drift and matrix interferences between standards of varying Ba/Ca ratios indicate that standardized corrections can be applied. Comparative analysis between ICP-OES and an established ICP-MS technique in a Singapore coral and international coral standard JCp-1 were utilized to validate the proposed ICP-OES technique. ICP-MS and ICP-OES techniques showed a consistent offset, which was correctible with the use of an internal lab standard and resulted in only minor differences between techniques. ICP-OES showed comparable accuracy and precision to the ICP-MS, as evaluated by analysis of JCp-1 which averaged values within one standard deviation of established concentrations (accurate to within 0.38 μmol Ba/mol Ca and 0.014 mmol Sr/mol Ca). We have demonstrated a sufficiently precise and accurate method for simultaneous analysis of Ba and Sr to Ca ratios in coral samples on an ICP-OES system. Expanding the application of ICP-OES in coral geochemical analysis provides a lower cost alternative to ICP-MS, while maintaining a high sample throughput.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Published versio

Skeletal Growth Rates in <i>Porites lutea</i> Corals from Pulau Tinggi, Malaysia

Skeletal records of massive Porites lutea corals sampled from reefs around Malaysia have previously shown average decadal declines in growth rates associated with sea warming. However, there was a variability in growth declines between sites that warrant the need for investigations into more site-specific variations. This study analyzed decade-long (December 2004–November 2014) annual growth records (annual linear extension rate, skeletal bulk density, calcification rate) reconstructed from five massive P. lutea colonies from Pulau Tinggi, Malaysia. Significant non-linear changes in inter-annual trends of linear extension and calcification rates were found, with notable decreases that corresponded to the 2010 El Niño thermal stress episode and a pan-tropical mass coral bleaching event. Coral linear extension and calcification were observed to return to pre-2010 rates by 2012, suggesting the post-stress recovery of P. lutea corals at the study site within 2 years. Although no long-term declines in linear extension and calcification rates were detected, a linear decrease in annual skeletal bulk density by ≈9.5% over the 10-year study period was found. This suggests that although coral calcification rates are retained, the skeletal integrity of P. lutea corals may be compromised with potential implications for the strength of the overall reef carbonate framework. The correlation of coral calcification rates with sea surface temperature also demonstrated site-specific thermal threshold at 29 °C, which is comparable to the regional thermal threshold previously found for the Thai-Malay Peninsula

Skeletal Growth Rates in Porites lutea Corals from Pulau Tinggi, Malaysia

Skeletal records of massive Porites lutea corals sampled from reefs around Malaysia have previously shown average decadal declines in growth rates associated with sea warming. However, there was a variability in growth declines between sites that warrant the need for investigations into more site-specific variations. This study analyzed decade-long (December 2004&ndash;November 2014) annual growth records (annual linear extension rate, skeletal bulk density, calcification rate) reconstructed from five massive P. lutea colonies from Pulau Tinggi, Malaysia. Significant non-linear changes in inter-annual trends of linear extension and calcification rates were found, with notable decreases that corresponded to the 2010 El Ni&ntilde;o thermal stress episode and a pan-tropical mass coral bleaching event. Coral linear extension and calcification were observed to return to pre-2010 rates by 2012, suggesting the post-stress recovery of P. lutea corals at the study site within 2 years. Although no long-term declines in linear extension and calcification rates were detected, a linear decrease in annual skeletal bulk density by &asymp;9.5% over the 10-year study period was found. This suggests that although coral calcification rates are retained, the skeletal integrity of P. lutea corals may be compromised with potential implications for the strength of the overall reef carbonate framework. The correlation of coral calcification rates with sea surface temperature also demonstrated site-specific thermal threshold at 29 &deg;C, which is comparable to the regional thermal threshold previously found for the Thai-Malay Peninsula

An assessment of P speciation and P:Ca proxy calibration in coral cores from Singapore and Bali

10.1016/j.gca.2019.09.024Geochimica et Cosmochimica Acta267113-12

Host age is not a consistent predictor of coral-associated microbial diversity

Scientific Report

An update of the Pb isotope inventory in post leaded-petrol Singapore environments

Pb is a trace metal that tracks anthropogenic pollution in natural environments. Despite recent leaded petrol phase out around Southeast Asia, the region's growth has resulted in continued exposure of Pb from a variety of sources. In this study, sources of Pb into Singapore, a highly urbanised city-state situated in the central axis of Southeast Asia, are investigated using isotopic ratios and concentrations. We compiled data from our previous analyses of aerosols, incineration fly ash and sediments, with new data from analyses of soil from gas stations, water from runoff and round-island coastal seawater to obtain a spatio-temporal overview of sources of Pb into the Singapore environment. Using 206Pb/207Pb ratio, we identified three main Pb source origins: natural Pb (1.215 ± 0.001), historic/remnant leaded petrol (1.123 ± 0.013), and present-day industrial and incinerated waste (1.148 ± 0.005). Deep reservoir sediments bore larger traces of Pb from leaded petrol, but present-day runoff waters and coastal seawater were a mix of industrial and natural sources with somewhat variable concentrations. We found temporal variability in Pb isotopic ratio in aerosols indicating alternating transboundary Pb sources to Singapore that correspond to seasonal changes in monsoon winds. By contrast, seasonal monsoon circulation did not significantly influence isotopic ratios of coastal seawater Pb. Instead, seawater Pb was driven more by location differences, suggesting stronger local-scale drivers of Pb such as point sources, water flushing, and isotope exchange. The combination of multiple historic and current sources of Pb shown in this study highlights the need for continued monitoring of Pb in Southeast Asia, especially in light of emerging industries and potential large sources of Pb such as coal combustion.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Accepted versio

Environmental Calibration of Coral Luminescence as a Proxy for Terrigenous Dissolved Organic Carbon Concentration in Tropical Coastal Oceans

The riverine flux of terrigenous dissolved organic matter (tDOM) to the ocean is a significant contributor to the global carbon cycle. In response to anthropogenic drivers the flux is expected to increase. This may impact the availability of sunlight in coastal ecosystems, and the seawater carbonate system and coastal CO2 fluxes. Despite its significance, there are few long-term and high-resolution time series of tDOM parameters. Corals incorporate fluorescent tDOM molecules from the chromophoric dissolved organic matter (CDOM) pool in their skeletons. The resulting coral skeletal luminescence variability has traditionally been used to reconstruct hydroclimate variation. Here, we use two replicate coral cores and concurrent in-situ biogeochemical data from the Sunda Shelf Sea in Southeast Asia, where peatlands supply high tDOM inputs, to show that variability in coral luminescence green-to-blue ratios (coral G/B) can be used to quantitatively reconstruct terrigenous dissolved organic carbon (tDOC) concentration. Moreover, coral G/B can be used to reconstruct the CDOM absorption spectrum from 230 to 550 nm, and the specific ultraviolet absorbance at 254 nm (SUVA(254)) of the DOM pool. Comparison to a core from Borneo shows that there may be site-specific offsets in the G/B-CDOM absorption relationship, but that the slope of the relationship is very similar, validating the robustness of the proxy. By demonstrating that corals can be used to estimate past changes in coastal tDOC and CDOM, we establish a method to study drivers of land-ocean tDOM fluxes and their ecological consequences in tropical coastal seas over decadal to centennial time scales.ISSN:1525-202

Sub-annual fluorescence measurements of coral skeleton : relationship between skeletal luminescence and terrestrial humic-like substances

Some massive coral core slices reveal luminescent bands under ultraviolet light, which have been attributed to terrestrial humic acids in the skeleton. Coral luminescence has therefore been used to reconstruct past climate and hydrological variability. However, it has remained unresolved how closely coral luminescence at sub-annual resolution is related to terrestrial humic acid concentrations. This study presents a solution-based fluorescence method to quantify terrestrial humic substances in less than 4 mg of coral powder. The results show that in corals from Malaysia and Singapore, the luminescence green-to-blue ratio is correlated with skeletal concentrations of terrestrial humic substances (R2 > 0.40, p  0.6) and large downcore variability (range of ≥ 0.05), the green-to-blue ratio is strongly linked to variation in terrestrial humic substances. Coral cores therefore have the potential to reconstruct past variation in terrigenous dissolved organic carbon fluxes.Ministry of Education (MOE)National Research Foundation (NRF)Published versionFunding was provided by an Academic Research Fund Tier 1 grant from the Singapore Ministry of Education to P.M. (Grant RG123/18), by the National Research Foundation Singapore through an International Collaborative Fellowship for the Commonwealth to N.K. (Grant NRF-CSC-ICFC2017-01), by the National Research Foundation Singapore under the Marine Science Research and Development Programme to J.T.I.T. and N.F.G. (Project MSRDP-03), and from the Ministry of Education Malaysia through Grant FRGS/2/2013/STWN04/UMT/03/1 to J.N.L