Moritz Müller

The impact of disturbed peatlands on river outgassing in Southeast Asia

River outgassing has proven to be an integral part of the carbon cycle. In Southeast Asia, river outgassing quantities are uncertain due to lack of measured data. Here we investigate six rivers in Indonesia and Malaysia, during five expeditions. CO2 fluxes from Southeast Asian rivers amount to 66.9±15.7 Tg C per year, of which Indonesia releases 53.9±12.4 Tg C per year. Malaysian rivers emit 6.2±1.6 Tg C per year. These moderate values show that Southeast Asia is not the river outgassing hotspot as would be expected from the carbon-enriched peat soils. This is due to the relatively short residence time of dissolved organic carbon (DOC) in the river, as the peatlands, being the primary source of DOC, are located near the coast. Limitation of bacterial production, due to low pH, oxygen depletion or the refractory nature of DOC, potentially also contributes to moderate CO2 fluxes as this decelerates decomposition.

Heavy Metal Resistant Endophytic Fungi Isolated from Nypa fruticans in Kuching Wetland National Park

Heavy metal pollution is an environmental issue globally and the aim of this study was to isolate endophytic fungi from mangrove wetlands of Sarawak to assess and test their ability to grow in the presence of various heavy metals (copper (Cu), zinc (Zn), lead (Pb), and chromium (Cr)). Samples of Nypa fruticans were collected from Kuching Wetland National Park (KWNP) for subsequent endophyte isolation. Ninety-three (93) isolates were obtained and assessed and the most resistant isolates (growing at concentrations up to 1000 ppm) were identified using fungal primers ITS 1 and ITS 4. All of the endophytic fungi were identified to be closely related to Pestalotiopsis sp. and this is to our knowledge the first study reporting the ability of Pestalotiopsis sp. to grow at high concentrations of copper, lead, zinc and chromium. Our results highlight the potential of using endophytic fungi for the treatment of heavy metal pollution, for example as biosorbents.

Biogeochemical controls on microbial diversity in seafloor sulphidic sediments

The ultimate fate of hydrothermal sulphides on the seafloor depends on the nature and rate of abiotic and microbially catalysed reactions where sulphide minerals are exposed to oxic seawater. This study combines organic and inorganic geochemical with microbiological measurements across a suboxic transition zone of highly altered sulphidic sediments from the Trans-Atlantic Geotransverse hydrothermal field to characterize the reaction products and microbial communities present. There is distinct biogeochemical zonation apparent within the sediment sequence from oxic surface layers through a suboxic transition zone into the sulphide material. The microbial communities in the sediment differ significantly between the biogeochemical horizons sampled, with the identified microbes inferred to be associated with Fe and S redox cycling. In particular, Marinobacter species, organisms associated with circumneutral Fe oxidation, are dominant in a sulphide lens present in the lower core. The dominance of Marinobacter-related sequences within the relict sulphide lens implies that these organisms play an important role in the alteration of sulphides at the seafloor once active venting has ceased.

The Potential Roles of Bacterial Communities in Coral Defence: A Case Study at Talang-Talang Reef

Complex microbial communities are known to exert significant influence over coral reef ecosystems. The Talang- Satang National Park is situated off the coast of Sematan and is one of the most diverse ecosystems found off-Sarawak. Interestingly, the Talang-talang reef thrives at above-average temperatures of 28- 30°C throughout the year. Through isolation and identification (16S rRNA) of native microbes from the coral, the surface mucus layer (SML), as well as the surrounding sediment and waters, we were able to determine the species composition and abundance of the culturable bacteria in the coral reef ecosystem. Isolates found attached to the coral are related mostly to Vibrio spp., presumably attached to the mucus from the water column and surrounding sediment. Pathogenic Vibrio spp. and Bacillus spp. were dominant amongst the isolates from the water column and sediment, while known coral pathogens responsible for coral bleaching, Vibrio coralliilyticus and Vibrio shiloi, were isolated from the coral SML and sediment samples respectively. Coral SML isolates were found to be closely related to known nitrogen fixers and antibiotic producers with tolerance towards elevated temperatures and heavy metal contamination, offering a possible explanation why the local corals are able to thrive in higher than usual temperatures. This specialized microbiota may be important for protecting the corals from pathogens by occupying entry niches and/or through the production of secondary metabolites such as antibiotics. The communities from the coral SML were tested against each other at 28, 30 and 32°C, and were also assessed for the presence of type I modular polyketides synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes which are both involved in the production of antibiotic compounds. The bacterial community from the SML exhibited antimicrobial properties under normal temperatures while pathogenic strains appeared toxic at elevated temperatures and our results highlight the role of the coral SML bacterial community in the coral’s defence.

An Electrochemical Study of the Influence of Marinobacter aquaeolei on the Alteration of Hydrothermal Chalcopyrite (CuFeS2) and Pyrite (FeS2) under Circumneutral Conditions

Pyrite and chalcopyrite are the two most abundant sulphides observed in seafloor hydrothermal systems. The alteration of sulphides is primarily controlled by reactions on the mineral surfaces and Fe(II)-oxidizing bacteria closely related to Marinobacter aquaeolei are thought to play a major role in iron oxidation under circumneutral conditions. We assessed the influence of M. aquaeolei on the electroactivity of FeS2 and CuFeS2 minerals under circumneutral conditions. Samples for the experiments were obtained from the Trans-Atlantic Geotraverse (TAG) hydrothermal mound (field), 26 °N on the Mid-Atlantic Ridge and Ireland (CuFeS2)]. The experimental approach relied on voltammetry and scanning electrochemical microscopy (SECM). The tip-substrate voltammetry mode of SECM was found to be particularly suitable to probe the major redox processes of those minerals and permitted an assessment of the microorganisms influence on these processes. M. aquaeolei was found to enhance FeS2 and CuFeS2 oxidation, particularly under suboxic conditions. M. aquaeolei also significantly enhances Fe dissolution under oxic circumneutral conditions but suppresses the dissolution of most other elements compared to abiotic conditions. Under abiotic conditions the surfaces of the minerals are rapidly passivated when oxygen is available; while addition of M. aquaeolei significantly hinders the passivation of chalcopyrite, no passivation of the pyrite surface is observed. This study demonstrates the ability of Marinobacter aquaeolei to enhance oxidation of FeS2 and CuFeS2 under circumneutral conditions and supports the involvement of Marinobacter species in weathering reactions on the seafloor and the control of the ultimate fate of sulphide deposits.

Biosorption of copper by endophytic fungi isolated from Nepenthes ampullaria

Copper (Cu) tolerance was observed by endophytic fungi isolated from the carnivorous plant Nepenthes ampullaria (collected at an anthropogenically affected site, Kuching city; and a pristine site; Heart of Borneo). The fungal isolates, capable of tolerating Cu up to 1000 ppm (11 isolates in total), were identified through molecular method [internal transcribed spacer 4+5 (ITS4+5); ITS1+NL4; β‐tubulin region using Bt2a + Bt2b], and all of them grouped with Diaporthe, Nigrospora, and Xylaria. A Cu biosorption study was then carried out using live and dead biomass of the 11 fungal isolates. The highest biosorption capacity of using live biomass was achieved by fungal isolates Xylaria sp. NA40 (73·26 ± 1·61 mg Cu per g biomass) and Diaporthe sp. NA41 (72·65 ± 2·23 mg Cu per g biomass), NA27 (59·81 ± 1·15 mg Cu per g biomass) and NA28 (56·85 ± 4·23 mg Cu per g biomass). The fungal isolate Diaporthe sp. NA41 also achieved the highest biosorption capacity of 59·33 ± 0·15 mg g−1 using dead biomass. The living biomass possessed a better biosorption capacity than the dead biomass (P < 0·05) and the roadside fungal strains showed higher Cu biosorption capacities using live biomass compared to the jungle fungal strains (P < 0·05).

Impact of peatlands on carbon dioxide (CO 2 ) emissions from the Rajang River and Estuary, Malaysia

1 Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany 5 2 Leibniz Center for Tropical Marine Research, Fahrenheitstr. 6, 28359 Bremen, Germany 3 Institute of Geology, University of Hamburg, Bundesstr. 55, 20146 Hamburg, Germany 4 Swinburne University of Technology, Faculty of Engineering, Computing and Science, Jalan Simpang Tiga, 93350 Kuching, Sarawak, Malaysia 5 Centre for Coastal Biogeochemistry, School of Environment, Science and Engineering, Southern Cross University, Lismore 10 NSW 2480, Australia

Role of bacterial communities in coral’s defence against a causative agent of coral bleaching: Vibrio coralliilyticus

Aims: Different studies have shown that members of the Vibrio such as Vibrio coralliilyticus and Vibrio shiloi are opportunistic pathogens which can cause coral lysis. The aims of this study were to assess whether this results of the virulence of V. coralliilyticus are transmittable to Acropora hyacinthus and Porites lobata, and what role the microbiome of the corals plays during exposure to V. coralliilyticus. Methodology and results: In laboratory-based experiments, we examined the impact of V. coralliilyticus (ATCC BAA450) to the microbiome of Acropora hyacinthus and Porites lobata. A. hyacinthus and P. lobata were exposed to ampicillin, V. coralliilyticus, and a combination of both. Results indicate a resistance of A. hyacinthus to V. coralliilyticus through the microbiome and underpin the importance of the microbiome for the coral’s health. Conclusion, significance and impact study: Further studies are needed to identify the bacteria responsible for the coral resistance and could in future lead to the development of a probiotic treatment or prevention of bleaching for sensitive corals.