Laboratory capacity for the analysis of Soil Organic Matter in Pacific Island Region and the Blue Carbon Initiative

Dr Vincent Lal1, Dr. Katy Soapi2, Dr.  Isoa Korovulavula3

1University of The South Pacific, The Institute Of Applied Sciences, Suva, Fiji, 2University of the South Pacific, Suva, Fiji, 3University of the South Pacific, Suva, Fiji

The Institute of Applied Sciences Analytical Laboratory at the University of the South Pacific (USP) is an accredited laboratory that serves USP 12 member countries in the Pacific Island Region (PIR). The analysis of Organic Carbon in soil and sediment samples are performed using the Walkley and Black method using 1 g of soil. A key difficulty is that the Walkley-Black method may result in low test results for certain soils with organic matter greater than 6%. However, the method performs well with soil or sediment samples with low organic matter. To further develop testing capacity for measuring Organic Carbon for ongoing Initiative on Blue Carbon, there is a need to adopt measurement techniques with direct sample introduction such as the CHN analyser by loss of ignition. Additionally, there is a need to build capacity in the laboratory so that technicians in the laboratories in the Pacific Island Region are able to  achieve accreditation for the testing of Organic Carbon. Taking part in soil proficiency testing offered by ASPAC could assist in improvements in quality control. This will ensure quality data is produced in the Pacific Island Region laboratories and can be useful for development of Policies in the Region on initiatives like the Blue Carbon.


The crucial role of organic carbon availability in driving geochemical cycles in wetland and floodplain soils

A/Prof. Luke Mosley1, Prof. Rob Fitzpatrick1, Dr Angelika Kolbl2,3, Ms Emily Leyden1, Prof. Petra Marchner4

1Acid Sulfate Soils Centre, School of Biological Sciences, University Of Adelaide, Adelaide, Australia, 2Chair of Soil Science, Technical University of Munich, Freising, Germany, 3Soil Science, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany, 4School of Agriculture, Food and Wine, University of Adelaide, Adelaide, Australia

Many of the key geochemical cycles in wetland and floodplain soils (e.g. sulfate reduction, denitrification, methanogenesis) are driven or influenced by organic matter. Microbes play a central role in many of the geochemical reactions using organic carbon as an energy source. The bioavailability of the organic carbon to microbes, rather than its total concentration, is hence of central importance. We review and synthesise findings from several studies to show that the availability of organic carbon in many hydric soils controls geochemical reactions. Particular focus is placed on organic carbon availability in acid sulfate soils, as these can create severe and sustained acidification and metal release impacts following drainage/drought. In our long term field site in the Lower River Murray (South Australia), soils have not recovered from severe acidification (pH<4) over 10 years after the drought ended. Soil organic carbon concentrations are moderate (1-2% C) in the acidified soil layers but microbial reduction reactions are very limited. In contrast, when we add available organic carbon in the laboratory the soils can recover within weeks, but only if the pH is first adjusted to above 5. This suggests toxicity by low pH or high metal (e.g. Al3+) concentrations limiting microbial activity. Solid state 13C NMR studies have revealed that, compared to the native soil organic matter, soils with fresh organic matter addition are characterized by high proportions of O/N-alkyl C, which is readily decomposed compared to other components. The concentration of terminal electron acceptors (e.g. nitrate) may also influence microbial reduction reactions. While organic carbon availability limitations can be overcome by addition of organic materials, practical difficulties may be present in amending deep soil layers in wetland soils. The potential for enhanced greenhouse gas release following soil amendment also needs consideration.

Biography: A/Prof. Luke Mosley leads a biogeochemical research group at the Waite Campus, University of Adelaide. Assessment of the role of organic carbon availability and dynamics in influencing geochemical cycles in inland and coastal wetlands has been a key research focus over the last decade. Luke is also Deputy Director of the Acid Sulfate Soil Centre at the University of Adelaide and President of Soil Science Australia.

Predicting the carbon and nitrogen contents in soil from blue carbon environments using infrared spectroscopy

CSIRO Jeff Baldock1, Dr Peter Macreadie2, Dr Jeff Kelleway3, Dr Oscar Serrano4, Dr Paul Lavery4, Ms Christina Asanopoulos5, Dr Joey Crosswell6, Dr Catherine Lovelock7, Dr Matt Hayes7, Dr Andy Steven6

1CSIRO Agriculture and Food, Glen Osmond, Australia, 2Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Australia, 3School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, Australia, 4School of Science & Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, Australia, 5School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, Australia, 6CSIRO Oceans and Atmosphere, Brisbane, Australia, 7University of Queensland, St Lucia, Australia

Coastal blue carbon environments (mangroves, tidal marshes and seagrass meadows) can contain significant stocks of soil organic carbon and can accumulate additional organic carbon through the capture and retention of organic materials derived from autochthonous and allochthonous sources.  Assessing soil organic carbon stocks present in these environments requires quantification of soil organic carbon concentration.  Developments in the combined use of infrared spectroscopy and partial least squares regression analyses (IR/PLSR) have demonstrated an ability to provide cost effective measurement of organic carbon concentration in agricultural soils and additionally provide values for the concentrations of inorganic carbon and total nitrogen from one analysis.  The objective of this study was to assess the capability of IR/PLSR analyses to provide accurate values for total (TC), organic (OC) and inorganic (IC) carbon and total nitrogen (TN) concentrations in soil samples derived from blue carbon environments.  A total 1201 samples were used.  All TC, OC, IC and TN analytical data were acquired using automated dry combustion analysers (LECO TruMac, C-144 or CNS-2000) with the application of acid pretreatment to soils containing carbonate.  Independent sets of 300 and 901 samples were used respectively to develop and then validate IR/PLSR predictive algorithms.  Robust IR/PLSR models were obtained for TC, OC, IC and TN concentrations given the values derived for the coefficient of determination (R2=0.91-0.96), ratio of performance to deviation (RPD = 4.8-5.6) and ratio of performance to interquartile range (RPIQ = 2.5-3.8).  After calibration, the concentrations of TC, OC, IC and TN of the blue carbon soils could be robustly predicted using a single IR scan.  The IR/PLSR approach therefore provides a cost-effective alternative approach to quantifying the concentration of carbon and nitrogen in blue carbon soils.

Biography: Jeff Baldock is a research scientist working with CSIRO studying the cycling of organic carbon in a range of natural environments.

Nutrient enrichment induces a shift in dissolved organic carbon (DOC) metabolism in oligotrophic freshwater sediments

Miss Francesca  Brailsford1, Dr Helen Glanville2, Professor Peter Golyshin1, Dr Miles Marshall1, Dr Charlotte Lloyd3, Professor Penny Johnes3, Professors Davey Jones1

1Bangor University, Bangor, United Kingdom, 2Keele University, Keele, United Kingdom, 3Bristol University, Bristol, United Kingdom

Dissolved organic matter (DOC) turnover in aquatic environments is modulated by the presence of other key macronutrients, including nitrogen (N) and phosphorus (P). The ratio of these nutrients directly affects the rates of microbial growth and nutrient processing in the natural environment. The aim of this study was to investigate how labile DOC metabolism responds to changes in nutrient stoichiometry using 14C tracers in conjunction with untargeted analysis of the primary metabolome in upland peat river sediments. N addition led to an increase in 14C-glucose uptake, indicating that the sediments were likely to be primarily N limited. The mineralization of glucose to 14CO2 reduced following N addition, indicating that nutrient addition induced shifts in internal C partitioning and microbial C use efficiency. This is directly supported by the metabolomic profile data which identified significant differences in 22 known metabolites (34% of the total) and 30 unknown metabolites (16 % of the total) upon the addition of either N or P. 14C-glucose addition increased the production of organic acids known to be involved in mineral P dissolution (e.g. gluconic acid, malic acid). Conversely, when N was not added, the addition of glucose led to the production of the sugar alcohols, mannitol and sorbitol, which are well known microbial C storage compounds. P addition resulted in increased levels of several amino acids (e.g. alanine, glycine) which may reflect greater rates of microbial growth or the P requirement for coenzymes required for amino acid synthesis. We conclude that inorganic nutrient enrichment in addition to labile C inputs has the potential to dramatically alter in-stream biogeochemical cycling in oligotrophic freshwaters.

Biography: After obtaining a BSc in Biochemistry at King’s College London, I returned to North Wales to study for an MSc in Marine Biology at Bangor University. I am completing my PhD part-time alongside my role as a Junior Research Technician on the NERC DOMAINE Project, which aims to characterise the nature, origins and ecological significance of dissolved organic matter in freshwater ecosystems. The project partners include the University of Bristol, Bangor University, The University of East Anglia and the Centre for Ecology & Hydrology (CEH). My research is part of Work Package 3 of the DOMAINE Project, which aims to identify the dominant metabolic pathways controlling stream and nutrient processing and uptake. Currently I am involved in the seasonal analysis of low-molecular weight (LMW) nutrient processing using both 14C and 33P labelling methods. Once this is complete a combination of microbial characterisation and metabolomic approaches will be used to identify the major microbial groups and nutrient pathways involved in in-stream processing. Information on the NERC DOMAINE Project can be found below: Future publications will be added to ResearchGate:

Microbial uptake kinetics of dissolved organic carbon (DOC) compound groups from river water and sediments

Dr Helen Glanville1, Miss Francesca  Brailsford2, Professor Peter Golyshin2, Professor Penny  Johnes3, Dr Chris Yates3, Professor Davey Jones1

1Keele University, Crewe, United Kingdom, 2Bangor University , Bangor, United Kingdom, 3Bristol University, Bristol, United Kingdom, 4University of Western Australia, Perth, Australia

Since completing my PhD (2013), I have worked as a biogeochemist on 2 large NERC-funded consortium projects (2013-2017), both at Bangor university. My research explored critical thresholds controlling microbial pathways in terrestrial and aquatic environments (North Wales and SW England) to understand their role in larger scale, global nutrient (C, N and P) cycling processes (for further project information follow the links and

Dissolved organic matter (DOM) represents a key component of carbon cycling in freshwater ecosystems. While the behaviour of bulk DOC in aquatic ecosystems is well studied, comparatively little is known about the turnover of specific dissolved organic carbon (DOC) compounds. The aim of this study was to investigate the persistence of 14C-labelled low molecular weight (LMW) DOC at a wide range of concentrations (0.1 µM to 10 mM), in sediments and waters from oligotrophic and mesotrophic rivers within the same catchment. Overall, rates of DOC loss varied between compound groups (amino acids > sugars = organic acids > phenolics). Sediment-based microbial communities contributed to higher DOC loss from river waters, which was attributed, in part, to its greater microbial biomass. At higher DOC compound concentrations, DOC loss was greater in mesotrophic rivers in comparison to oligotrophic headwaters. A lag-phase in substrate use within sediments provided evidence of microbial growth and adaptation, ascribed here to the lack of inorganic nutrient limitation on microbial C processing in mesotrophic communities. We conclude that the higher microbial biomass and available inorganic nutrients in sediments enables the rapid processing of LMW DOC, particularly during high C enrichment events and in N and P-rich mesotrophic environments.

Biography: After graduating with an MSci. in Geology from Birmingham University, I worked in the oil and gas industry as a formation damage geologist for 6 months. I then had a complete career change and moved to South Korea to work as an English teacher. After 2 years as a senior teacher, I returned to the UK (2008) to pursue a career in academia by studying for a Ph.D in soil biogeochemistry at Bangor University, looking at drivers controlling soil respiration in temperate grasslands and high Arctic tundra in Svalbard. I was awarded the Drapers’ Company Bronze medal (2013) in recognition of outstanding academic achievements and for providing pastoral support to my peers.

Since completing my PhD (2013), I have worked as a biogeochemist on 2 large NERC-funded consortium projects (2013-2017), both at Bangor university. My research explored critical thresholds controlling microbial pathways in terrestrial and aquatic environments (North Wales and SW England) to understand their role in larger scale, global nutrient (C, N and P) cycling processes (for further project information follow the links and

I then joined the Geography, Geology and the Environment group at Keele university as a Lecturer in Physical Geography in 2017 where I am keen to develop new and exciting research ideas and continue to widen my research collaborations

Investigating the relationship between soil organic carbon and age in temperate blue carbon ecosystems.

Miss Christina Asanopoulos1,2, Dr Lynne Macdonald2,1, Dr Jeff Baldock2,1, A/Prof Timothy Cavagnaro1

1University Of Adelaide, Glen Osmond, Australia, 2CSIRO, Glen Osmond, Australia

Blue carbon ecosystems such as mangrove forests, tidal marshes and seagrass meadows account for almost 50% of total soil carbon stores, globally. Their exceptionally high carbon burial rates are attributed to the retention of organic matter by extensive root systems that encourage deposition and prevent erosion of rich organic material. High carbon burial rates coupled with slow decomposition of the soil organic matter (SOM) results in long term carbon storage. However, the chemical nature of blue carbon through the soil profile and its potential vulnerability to decomposition, particularly with changes in environmental conditions, is largely unknown. The objective of this study was to investigate the relationship between chemical structure of the SOM in the blue carbon environment and its age. Specifically, we characterised the chemical structure of the soil organic carbon (SOC) in mangrove soils through the depth profile with solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Samples were collected from an undisturbed temperate mangrove forest in South Australia to a depth of 1 m. All samples were analysed for elemental carbon content and aged by 210Pb and 14C (radiocarbon) dating methods prior to being selected for 13C NMR. Samples were selected to reflect a continuum in age based on short term (210Pb) and long-term (14C) dating data. The relationship between age and chemistry was then assessed using a partial least squares regression (PLSR) analysis. Radiocarbon age tends to increase with depth and is assumed to reflect the mean residence time of the SOM and in turn its stability. Characterising the chemical structure of SOM through the depth profile will contribute to a better understanding of carbon cycling and long-term stability of SOC in the blue carbon environment. An in-depth analysis of the chemical structure of the blue carbon SOM and the PLSR analysis will be discussed.


Christina Asanopoulos is an early career research scientist based at the University of Adelaide. In 2011, she successfully completed a bachelor’s degree in marine biology (hons) and commenced working at the CSIRO as a research assistant in the soil carbon and nitrogen cycling group. Christina’s research interests are in investigating the impacts of anthropogenic activity and climate induced change on natural ecosystems to improve their conservation. Since 2016 she has been undertaking a PhD affiliated with the University of Adelaide and CSIRO. The research focus of Christina’s PhD is in biogeochemical cycling of carbon in South Australia’s temperate coastal wetlands.

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