ORCID Profile
0000-0002-1021-1923
Current Organisation
University of Tasmania
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Oceanography | Biological oceanography | Chemical oceanography |
Publisher: Elsevier BV
Date: 08-2017
Publisher: American Geophysical Union (AGU)
Date: 05-2022
DOI: 10.1029/2021GB007194
Abstract: Marine free‐living (FL) bacteria play a key role in the cycling of essential biogeochemical elements, including iron (Fe), during their uptake, transformation and release of organic matter throughout the water column. Similar to phytoplankton, the growth of FL bacteria is regulated by nutritive resources such as Fe, and the low availability of these resources may influence bacterial interactions with phytoplankton, causing knock‐on effects for biogeochemical cycling. Yet, knowledge of the factors limiting the growth of FL bacteria and their role within the Fe cycle is poorly constrained. Here, we explicitly represent FL, carbon‐oxidizing bacteria in a three‐dimensional global ocean biogeochemistry model to address these questions. We find that although Fe can emerge as proximally limiting in the tropical Pacific and in high‐latitude regions during summer, the growth of FL bacteria is ultimately controlled by the availability of labile dissolved organic carbon over most of the world's oceans. In Fe‐limited regions, FL bacterial biomass is sensitive to their Fe uptake capability in seasonally Fe‐limitation regions and to their minimum Fe requirements in regions perennially low in Fe. Fe consumption by FL bacteria is significant in the upper ocean in our model, and their competition with phytoplankton for Fe affects phytoplankton growth dynamics and can make bacteria become more carbon limited. The impact of FL bacteria on the Fe distribution in the ocean interior is small due to a tight coupling between Fe uptake and release. Moving forward, future work that considers other bacteria groups and different bacterial metabolisms is needed to explore the broader role of bacteria in ocean Fe cycling. In this context, the global growing’ omics data from ocean observing programs can play a crucial role.
Publisher: Elsevier BV
Date: 12-2015
Publisher: Springer Science and Business Media LLC
Date: 09-10-2009
Publisher: Wiley
Date: 08-02-2011
DOI: 10.1111/J.1461-0248.2010.01578.X
Abstract: The decomposition of plant litter is one of the most important ecosystem processes in the biosphere and is particularly sensitive to climate warming. Aquatic ecosystems are well suited to studying warming effects on decomposition because the otherwise confounding influence of moisture is constant. By using a latitudinal temperature gradient in an unprecedented global experiment in streams, we found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates. As a result, overall decomposition rates should remain unchanged. Nevertheless, the process would be profoundly altered, because the shift in importance from detritivores to microbes in warm climates would likely increase CO(2) production and decrease the generation and sequestration of recalcitrant organic particles. In view of recent estimates showing that inland waters are a significant component of the global carbon cycle, this implies consequences for global biogeochemistry and a possible positive climate feedback.
Publisher: Springer Science and Business Media LLC
Date: 02-02-2023
DOI: 10.1038/S41467-023-36241-5
Abstract: Zooplankton are major consumers of phytoplankton primary production in marine ecosystems. As such, they represent a critical link for energy and matter transfer between phytoplankton and bacterioplankton to higher trophic levels and play an important role in global biogeochemical cycles. In this Review, we discuss key responses of zooplankton to ocean warming, including shifts in phenology, range, and body size, and assess the implications to the biological carbon pump and interactions with higher trophic levels. Our synthesis highlights key knowledge gaps and geographic gaps in monitoring coverage that need to be urgently addressed. We also discuss an integrated s ling approach that combines traditional and novel techniques to improve zooplankton observation for the benefit of monitoring zooplankton populations and modelling future scenarios under global changes.
Publisher: The Royal Society
Date: 27-04-2016
Abstract: Plant litter breakdown is a key ecological process in terrestrial and freshwater ecosystems. Streams and rivers, in particular, contribute substantially to global carbon fluxes. However, there is little information available on the relative roles of different drivers of plant litter breakdown in fresh waters, particularly at large scales. We present a global-scale study of litter breakdown in streams to compare the roles of biotic, climatic and other environmental factors on breakdown rates. We conducted an experiment in 24 streams encompassing latitudes from 47.8° N to 42.8° S, using litter mixtures of local species differing in quality and phylogenetic ersity (PD), and alder ( Alnus glutinosa ) to control for variation in litter traits. Our models revealed that breakdown of alder was driven by climate, with some influence of pH, whereas variation in breakdown of litter mixtures was explained mainly by litter quality and PD. Effects of litter quality and PD and stream pH were more positive at higher temperatures, indicating that different mechanisms may operate at different latitudes. These results reflect global variability caused by multiple factors, but unexplained variance points to the need for expanded global-scale comparisons.
Publisher: Wiley
Date: 19-05-2016
DOI: 10.1002/LNO.10322
Publisher: American Geophysical Union (AGU)
Date: 12-01-2021
DOI: 10.1029/2020GL088369
Publisher: American Geophysical Union (AGU)
Date: 11-2021
DOI: 10.1029/2020GB006921
Abstract: Despite widespread iron (Fe) limitation in the Southern Ocean, intense phytoplankton blooms are observed around productive coastal regions such as the Mertz Polynya (off George V Land and Adelie Land, East Antarctica 140–155°E). Sources of Fe across coastal East Antarctica vary, with limited data available for late summer months. We investigated the sources of dissolved Fe (dFe .2 μm) at 19 oceanographic stations in the Mertz Glacier Region (64–67°S 138–154°E), between January and March of 2019. Concentrations of dFe ranged from below detection limit (0.03 nM) at the surface, to 0.34 nM above the base of the mixed layer (35 m), reaching 0.59 nM at depth (520 m). Using oceanographic features and trace element ratios (manganese and titanium), we identified Circumpolar Deep Water (CDW) and shelf sediment resuspension in modified CDW as contributors of dFe to the region over this period. Microbial Fe remineralization was evident where nutrient‐rich water met highly oxygenated waters over the continental shelf. Reduced Fe concentrations in the mixed layer and euphotic zones suggested rapid biological uptake prior to s ling. Despite proposals for pelagic Fe recycling by marine animals, preliminary investigations reveal no significant spatial relationship between animal presence and surface ocean Fe concentrations over the study area. Further research is required to identify seasonal changes to Fe supply in coastal areas which will strengthen our understanding of the Fe cycle and its influence on microbial and primary productivity in this globally significant region.
Publisher: Springer International Publishing
Date: 2014
Publisher: University of Chicago Press
Date: 06-2009
DOI: 10.1899/07-161.1
Publisher: Elsevier BV
Date: 02-2015
DOI: 10.1016/J.JPLPH.2014.10.008
Abstract: The impact of elevated atmospheric [CO2] (e[CO2]) on plants often includes a decrease in their nutrient status, including Ca and Mg, but the reasons for this decline have not been clearly identified. One of the proposed hypotheses is a decrease in transpiration-driven mass flow of nutrients due to decreased stomatal conductance. We used glasshouse and Free Air CO2 Enrichment (FACE) experiments with wheat to show that, in addition to decrease in transpiration rate, e[CO2] decreased the concentrations of Ca and Mg in the xylem sap. This result suggests that uptake of nutrients is not only decreased by reduced transpiration-driven mass flow, but also by as yet unidentified mechanisms that lead to reduced concentrations in the xylem sap.
Publisher: Elsevier BV
Date: 03-2015
Publisher: Public Library of Science (PLoS)
Date: 03-12-2014
Publisher: Wiley
Date: 22-09-2021
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.CUB.2016.08.044
Abstract: Iron limits phytoplankton growth in large areas of the Southern Ocean. A new study shows that Antarctic krill play a crucial role in the recycling of iron in the iron-limited waters.
Publisher: University of Chicago Press
Date: 06-2012
DOI: 10.1899/11-103.1
Publisher: Wiley
Date: 05-11-2021
Publisher: Elsevier BV
Date: 07-2015
DOI: 10.1016/J.PLANTSCI.2015.04.006
Abstract: Projected climatic impacts on crop yield and quality, and increased demands for production, require targeted research to optimise nutrition of crop plants. For wheat, post-anthesis carbon and nitrogen remobilisation from vegetative plant parts and translocation to grains directly affects grain carbon (C), nitrogen (N) and protein levels. We analysed the influence of increased atmospheric CO2 on the expression of genes involved in senescence, leaf carbohydrate and nitrogen metabolism and assimilate transport in wheat under field conditions (Australian Grains Free Air CO2 Enrichment AGFACE) over a time course from anthesis to maturity, the key period for grain filling. Wheat grown under CO2 enrichment had lower N concentrations and a tendency towards greater C/N ratios. A general acceleration of the senescence process by elevated CO2 was not confirmed. The expression patterns of genes involved in carbohydrate metabolism, nitrate reduction and metabolite transport differed between CO2 treatments, and this CO2 effect was different between pre-senescence and during senescence. The results suggest up-regulation of N remobilisation and down-regulation of C remobilisation during senescence under elevated CO2, which is consistent with greater grain N-sink strength of developing grains.
Publisher: Springer Science and Business Media LLC
Date: 19-11-2014
Publisher: Frontiers Media SA
Date: 25-10-2021
DOI: 10.3389/FMARS.2021.737416
Abstract: Maintaining healthy, productive ecosystems in the face of pervasive and accelerating human impacts including climate change requires globally coordinated and sustained observations of marine bio ersity. Global coordination is predicated on an understanding of the scope and capacity of existing monitoring programs, and the extent to which they use standardized, interoperable practices for data management. Global coordination also requires identification of gaps in spatial and ecosystem coverage, and how these gaps correspond to management priorities and information needs. We undertook such an assessment by conducting an audit and gap analysis from global databases and structured surveys of experts. Of 371 survey respondents, 203 active, long-term (& years) observing programs systematically s led marine life. These programs spanned about 7% of the ocean surface area, mostly concentrated in coastal regions of the United States, Canada, Europe, and Australia. Seagrasses, mangroves, hard corals, and macroalgae were s led in 6% of the entire global coastal zone. Two-thirds of all observing programs offered accessible data, but methods and conditions for access were highly variable. Our assessment indicates that the global observing system is largely uncoordinated which results in a failure to deliver critical information required for informed decision-making such as, status and trends, for the conservation and sustainability of marine ecosystems and provision of ecosystem services. Based on our study, we suggest four key steps that can increase the sustainability, connectivity and spatial coverage of biological Essential Ocean Variables in the global ocean: (1) sustaining existing observing programs and encouraging coordination among these (2) continuing to strive for data strategies that follow FAIR principles (findable, accessible, interoperable, and reusable) (3) utilizing existing ocean observing platforms and enhancing support to expand observing along coasts of developing countries, in deep ocean basins, and near the poles and (4) targeting capacity building efforts. Following these suggestions could help create a coordinated marine bio ersity observing system enabling ecological forecasting and better planning for a sustainable use of ocean resources.
Publisher: Elsevier BV
Date: 07-2021
DOI: 10.1016/J.CUB.2021.05.016
Abstract: The scarcity of iron limits phytoplankton growth in large areas of the global ocean. Zooplankton may contribute to the cycling of iron via excretion and egestion. Despite evidence of high iron content in zooplankton excretion and faecal products, many questions arise as to the availability of regenerated iron for phytoplankton growth.
Publisher: Springer Science and Business Media LLC
Date: 18-10-2019
DOI: 10.1038/S41467-019-12668-7
Abstract: Antarctic krill ( Euphausia superba ) are swarming, oceanic crustaceans, up to two inches long, and best known as prey for whales and penguins – but they have another important role. With their large size, high biomass and daily vertical migrations they transport and transform essential nutrients, stimulate primary productivity and influence the carbon sink. Antarctic krill are also fished by the Southern Ocean’s largest fishery. Yet how krill fishing impacts nutrient fertilisation and the carbon sink in the Southern Ocean is poorly understood. Our synthesis shows fishery management should consider the influential biogeochemical role of both adult and larval Antarctic krill.
Publisher: Elsevier BV
Date: 2016
Publisher: American Geophysical Union (AGU)
Date: 05-2019
DOI: 10.1029/2019JC015071
Publisher: Springer Science and Business Media LLC
Date: 21-08-2015
Publisher: Frontiers Media SA
Date: 29-03-2018
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/FP14125
Abstract: Underlying physiological mechanisms of intraspecific variation in growth response to elevated CO2 concentration [CO2] were investigated using two spring wheat (Triticum aestivum L.) cultivars: Yitpi and H45. Leaf blade elongation rate (LER), leaf carbon (C), nitrogen (N) in the expanding leaf blade (ELB, sink) and photosynthesis (A) and C and N status in the last fully expanded leaf blade (LFELB, source) were measured. Plants were grown at ambient [CO2] (~384µmolmol–1) and elevated [CO2] (~550µmolmol–1) in the Australian Grains Free Air CO2 Enrichment facility. Elevated [CO2] increased leaf area and total dry mass production, respectively, by 42 and 53% for Yitpi compared with 2 and 13% for H45. Elevated [CO2] also stimulated the LER by 36% for Yitpi compared with 5% for H45. Yitpi showed a 99% increase in A at elevated [CO2] but no A stimulation was found for H45. There was a strong correlation (r2=0.807) between LER of the ELB and soluble carbohydrate concentration in LFELB. In ELB, the highest spatial N concentration was observed in the cell ision zone, where N concentrations were 67.3 and 60.6mg g–1 for Yitpi compared with 51.1 and 39.2mg g–1 for H45 at ambient and elevated [CO2]. In contrast, C concentration increased only in the cell ision and cell expansion zone of the ELB of Yitpi. These findings suggest that C supply from the source (LFELB) is cultivar dependent and well correlated with LER, leaf area expansion and whole-plant growth response to elevated [CO2].
Publisher: Elsevier BV
Date: 03-2015
DOI: 10.1016/J.FOODCHEM.2014.07.044
Abstract: Wheat cv. H45 was grown under ambient CO2 concentration and Free Air CO2 Enrichment (FACE e[CO2], ∼550 μmol CO2 mol(-1)). The effect of FACE on wheat grain proteome and associated changes in the flour rheological properties was investigated. A comparative proteomic analysis was performed using 2-D-DIGE followed by MALDI/TOF-MS. Total grain protein concentration was decreased by 9% at e[CO2]. Relative abundance of three high molecular weight glutenin sub units (HMW-GS) were decreased at e[CO2]. In contrast, relative abundance of serpins Z1C and 1-Cys peroxiredoxin was increased at e[CO2]. Elevated [CO2] also decreased the bread volume (by 11%) and dough strength (by 7%) while increased mixing time. However, dough extensibility and dough stability were unchanged at elevated [CO2]. These findings suggest that e[CO2] has a major impact on gluten protein concentration which is associated lower bread quality at e[CO2].
Location: United Kingdom of Great Britain and Northern Ireland
Location: Australia
Location: Australia
Start Date: 05-2023
End Date: 05-2026
Amount: $411,554.00
Funder: Australian Research Council
View Funded Activity