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Tropical shallow-water habitats represent the marine environments with the greatest biodiversity; however, these habitats are the most vulnerable to climate warming. Corals, seagrasses, and macroalgae play a crucial role in the structure, functions, and processes of the coastal ecosystems. Understanding their growth and physiological responses to elevated temperature and interspecific sensitivity is a necessary step to predict the fate of future coastal community. Six species representatives, including Pocillopora acuta, Porites lutea, Halophila ovalis, Thalassia hemprichii, Padina boryana, and Ulva intestinalis, collected from Phuket, Thailand, were subjected to stress manipulation for 5 days. Corals were tested at 27, 29.5, 32, and 34.5°C, while seagrasses and macroalgae were tested at 27, 32, 37, and 42°C. After the stress period, the species were allowed to recover for 5 days at 27°C for corals and 32°C for seagrasses and macroalgae. Non-destructive evaluation of photosynthetic parameters (Fv/Fm, Fv/F0, ϕPSII and rapid light curves) was carried out on days 0, 3, 5, 6, 8, and 10. Chlorophyll contents and growth rates were quantified at the end of stress, and recovery periods. An integrated biomarker response (IBR) approach was adopted to integrate the candidate responses (Fv/Fm, chlorophyll content, and growth rate) and quantify the overall temperature effects. Elevated temperatures were found to affect photosynthesis, chlorophyll content, and growth rates of all species. Lethal effects were detected at 34.5°C in corals, whereas adverse but recoverable effects were detected at 32°C. Seagrasses and macroalgae displayed a rapid decline in photosynthesis and lethal effects at 42°C. In some species, sublethal stress manifested as slower growth and lower chlorophyll content at 37°C, while photosynthesis remained unaffected. Among all, T. hemprichii displayed the highest thermotolerance. IBR provided evidence that elevated temperature affected the overall performance of all tested species, depending on temperature level. Our findings show a sensitivity that differs among important groups of tropical marine organisms inhabiting the same shallow-water environments and highlights the importance of integrating biomarkers across biological levels to assess their vulnerability to climate warming.

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Mangrove sediment and mangrove plant Soneratia caseolaris in Songkhla Lake, Thailand have been increasingly threatened by trace metal pollution. Mangroves receive trace metal pollution from upstream areas and the sea. However, little is known about the mangrove plant's capacity to uptake and store trace metals. In this study, the concentrations of As, Cd, Pb and Zn in mangrove plant parts (leaf, root, and bark) of Sonneratia caseolaris and sediments were determined. Sediment and plant samples were digested using total metal concentration procedure and ICPMS techniques. It was found that the maximum values of total concentrations of As in mangrove sediments were classified as heavily polluted according to USEPA. The highest concentrations of As and Zn were found to be in bark whereas Cd and Pb in the root. The fractions of all the metals were measured using BCR techniques and their results revealed that the bioavailability fraction was greater than the residual fraction. The order of the amounts of trace metals present in the fractions was as follows; As: Oxidizable > Reducible > Residual > Exchangeable and the order of Cd: Exchangeable > Reducible > Oxidizable > Residual. Both BCF and TF values showed limited accumulation of these elements in their aboveground parts and thus presented a low food chain hazard except at Phawong and U-Taphao canals.

The aim of this work was to determine the concentration of trace elements (Zn, As, Cd and Pb) in mangrove sediments using the European community bureau of reference (BCR) sequential extraction method. The sampling was conducted in August 2016 at 8 stations of Songkhla Lake in southern Thailand. Trace element concentrations were determined using the inductively coupled plasma mass spectrophotometer (ICPMS). Zn (37.20-64.42%) and Cd (63.44-77.50%) were found dominant in the acid-soluble fraction (F1). Pb (62.01-89.48%) was detected dominantly in reducible fraction (F2). As (49.92-73.45%) was found dominant in F2 (at stations 2, 4, 6, and 8) and in oxidizable fraction (F3) with the concentrations of 48.71-68.02% (at stations 1, 3, 5, and 7). All trace elements (Zn, As, Cd, and Pb) were bound to the bioavailable fractions (first three fractions) and were low in residual fraction (F4). Calculation of ecological risk assessment of Cd revealed that the individual concentration factor (ICF) >6, the global concentration factor (GCF) >24 and the risk assessment code (RAC) >50% in all stations were classified as high concentration and very high risk for aquatic organisms.