ORCID Profile
0000-0003-2816-9521
Current Organisations
University of Tasmania Institute for Marine and Antarctic Studies
,
University of Tasmania
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Publisher: Wiley
Date: 02-04-2020
DOI: 10.1111/GCB.15052
Publisher: Informa UK Limited
Date: 11-08-2020
Publisher: Wiley
Date: 24-04-2022
DOI: 10.1111/JPY.13249
Abstract: Carbon sequestration is defined as the secure storage of carbon‐containing molecules for years, and in the context of carbon dioxide removal for climate mitigation, the origin of this CO 2 is from the atmosphere. On land, trees globally sequester substantial amounts of carbon in woody biomass, and an analogous role for seaweeds in ocean carbon sequestration has been suggested. The purposeful expansion of natural seaweed beds and aquaculture systems, including into the open ocean (ocean afforestation), has been proposed as a method of increasing carbon sequestration and use in carbon trading and offset schemes. However, to verify whether CO 2 fixed by seaweeds through photosynthesis leads to carbon sequestration is extremely complex in the marine environment compared to terrestrial systems, because of the need to jointly consider: the comparatively rapid turnover of seaweed biomass, tracing the fate of carbon via particulate and dissolved organic carbon pathways in dynamic coastal waters, and the key role of atmosphere–ocean CO 2 exchange. We propose a Forensic Carbon Accounting approach, in which a thorough analysis of carbon flows between the atmosphere and ocean, and into and out of seaweeds would be undertaken, for assessing the magnitude of CO 2 removal and robust attribution of carbon sequestration to seaweeds.
Publisher: Springer Science and Business Media LLC
Date: 21-04-2022
DOI: 10.1038/S41559-022-01722-1
Abstract: Our scientific understanding of climate change makes clear the necessity for both emission reduction and carbon dioxide removal (CDR). The ocean with its large surface area, great depths and long coastlines is central to developing CDR approaches commensurate with the scale needed to limit warming to below 2 °C. Many proposed marine CDR approaches rely on spatial upscaling along with enhancement and/or acceleration of the rates of naturally occurring processes. One such approach is 'ocean afforestation', which involves offshore transport and concurrent growth of nearshore macroalgae (seaweed), followed by their export into the deep ocean. The purposeful occupation for months of open ocean waters by macroalgae, which do not naturally occur there, will probably affect offshore ecosystems through a range of biological threats, including altered ocean chemistry and changed microbial physiology and ecology. Here, we present model simulations of ocean afforestation and link these to lessons from other ex les of offshore dispersal, including rafting plastic debris, and discuss the ramifications for offshore ecosystems. We explore what additional metrics are required to assess the ecological implications of this proposed CDR. In our opinion, these ecological metrics must have equal weight to CDR capacity in the development of initial trials, pilot studies and potential licensing.
Publisher: Springer Science and Business Media LLC
Date: 06-06-2023
DOI: 10.1038/S42003-023-04962-4
Abstract: Carbon dioxide removal (CDR) and emissions reduction are essential to alleviate climate change. Ocean macroalgal afforestation (OMA) is a CDR method already undergoing field trials where nearshore kelps, on rafts, are purposefully grown offshore at scale. Dissolved iron (dFe) supply often limits oceanic phytoplankton growth, however this potentially rate-limiting factor is being overlooked in OMA discussions. Here, we determine the limiting dFe concentrations for growth and key physiological functions of a representative kelp species, Macrocystis pyrifera , considered as a promising candidate for OMA. dFe additions to oceanic seawater ranging 0.01-20.2 nM Fe′ ‒ Fe′ being the sum of dissolved inorganic Fe(III) species ‒ result in impaired physiological functions and kelp mortality. Kelp growth cannot be sustained at oceanic dFe concentrations, which are 1000-fold lower than required by M. pyrifera . OMA may require additional perturbation of offshore waters via dFe fertilisation.
Publisher: Springer Science and Business Media LLC
Date: 06-02-2021
Publisher: Oxford University Press (OUP)
Date: 10-01-2023
Abstract: In a future ocean, dissolved organic carbon (DOC) release by seaweed has been considered a pathway for organic carbon that is not incorporated into growth under carbon dioxide (CO2) enrichment/ocean acidification (OA). To understand the influence of OA on seaweed DOC release, a 21-day experiment compared the physiological responses of three seaweed species, two which operate CO2 concentrating mechanisms (CCMs), Ecklonia radiata (C. Agardh) J. Agardh and Lenormandia marginata (Hooker F. and Harvey) and one that only uses CO2 (non-CCM), Plocamium cirrhosum (Turner) M.J. Wynne. These two groups (CCM and non-CCM) are predicted to respond differently to OA dependent on their affinities for Ci (defined as CO2 + bicarbonate, HCO3−). Future ocean CO2 treatment did not drive changes to seaweed physiology—growth, Ci uptake, DOC production, photosynthesis, respiration, pigments, % tissue carbon, nitrogen, and C:N ratios—for any species, regardless of Ci uptake method. Our results further showed that Ci uptake method did not influence DOC release rates under OA. Our results show no benefit of elevated CO2 concentrations on the physiologies of the three species under OA and suggest that in a future ocean, photosynthetic CO2 fixation rates of these seaweeds will not increase with Ci concentration.
Publisher: Springer Science and Business Media LLC
Date: 03-05-2022
DOI: 10.1007/S10811-022-02743-W
Abstract: The combined culture of fed species (bivalves, fish) and macroalgae, known as integrated multi-trophic aquaculture (IMTA), has been suggested as a method of mitigating localised nitrogen (N) increase from aquaculture, whilst simultaneously culturing macroalgae for commercial applications. The development of IMTA requires an understanding of the N ecophysiology of candidate macroalga species. We examined seasonal variations in ammonium (NH 4 + ) uptake kinetics, carbon to nitrogen (C:N) ratio, pigment content and soluble tissue N of four macroalgae of the phylum Ochrophyta, Ecklonia radiata, Macrocystis pyrifera, Lessonia corrugata, and Phyllospora comosa, from Tasmania, Australia. This study aimed to determine, (1) if the N physiology of the four macroalgal species was suitable for IMTA applications and (2) whether the species had seasonal variations in N ecophysiology which would influence their suitability for IMTA. Macrocystis pyrifera , L. corrugata, and E. radiata exhibited saturable NH 4 + uptake kinetics, with a maximum uptake rate (V max ) during spring, summer and autumn of 200, 45.8 and 45 μmol gDW -1 h -1 and half-saturation constants (K s ) of 361.3, 104.2 and 121 μM, respectively. Phyllospora comosa exhibited biphasic uptake patterns for three out of four months s led. There were no noticeable seasonal patterns in pigment content or soluble tissue N for any species. C:N ratios increased from spring (October) to autumn (March) in both E. radiata (28.34 – 47.83) and P. comosa (24.99 – 51.62) , indicating progressive N limitation though summer and into autumn. Results suggest that M. pyrifera and P. comosa are most suitable for IMTA due to their high NH 4 + uptake potential.
Publisher: Wiley
Date: 23-08-2021
DOI: 10.1111/JPY.13198
Abstract: Dissolved organic carbon (DOC) release by seaweeds (marine macroalgae) is a critical component of the coastal ocean biogeochemical carbon cycle but is an aspect of seaweed carbon physiology that we know relatively little about. Seaweed‐derived DOC is found throughout coastal ecosystems and supports multiple food web linkages. Here, we discuss the mechanisms of DOC release by seaweeds and group them into passive (leakage, requires no energy) and active release (exudation, requires energy) with particular focus on the photosynthetic “overflow” hypothesis. The release of DOC from seaweeds was first studied in the 1960s, but subsequent studies use a range of units hindering evaluation: we convert published values to a common unit (μmol C · g DW −1 · h −1 ) allowing comparisons between seaweed phyla, functional groups, biogeographic region, and an assessment of the environmental regulation of DOC production. The range of DOC release rates by seaweeds from each phylum under ambient environmental conditions was 0–266.44 μmol C · g DW −1 · h −1 (Chlorophyta), 0–89.92 μmol C · g DW −1 · h −1 (Ochrophyta), and 0–41.28 μmol C · g DW −1 · h −1 (Rhodophyta). DOC release rates increased under environmental factors such as desiccation, high irradiance, non‐optimal temperatures, altered salinity, and elevated dissolved carbon dioxide (CO 2 ) concentrations. Importantly, DOC release was highest by seaweeds that were desiccated ( times greater DOC release compared to ambient). We discuss the impact of future ocean scenarios (ocean acidification, seawater warming, altered irradiance) on DOC release rates by seaweeds, the role of seaweed‐derived DOC in carbon sequestration models, and how they inform future research directions.
Publisher: Wiley
Date: 03-07-2023
DOI: 10.1111/JPY.13352
Abstract: Release of dissolved organic carbon (DOC) by seaweed underpins the microbial food web and is crucial for the coastal ocean carbon cycle. However, we know relatively little of seasonal DOC release patterns in temperate regions of the southern hemisphere. Strong seasonal changes in inorganic nitrogen availability, irradiance, and temperature regulate the growth of seaweeds on temperate reefs and influence DOC release. We seasonally surveyed and s led seaweed at Coal Point, Tasmania, over 1 year. Dominant species with or without carbon dioxide (CO 2 ) concentrating mechanisms (CCMs) were collected for laboratory experiments to determine seasonal rates of DOC release. During spring and summer, substantial DOC release (10.06–33.54 μmol C · g DW −1 · h −1 ) was observed for all species, between 3 and 27 times greater than during autumn and winter. Our results suggest that inorganic carbon (C i ) uptake strategy does not regulate DOC release. Seasonal patterns of DOC release were likely a result of photosynthetic overflow during periods of high gross photosynthesis indicated by variations in tissue C:N ratios. For each season, we calculated a reef‐scale net DOC release for seaweed at Coal Point of 7.84–12.9 g C · m −2 · d −1 in spring and summer, which was ~16 times greater than in autumn and winter (0.2–1.0 g C · m −2 · d −1 ). Phyllospora comosa , which dominated the biomass, contributed the most DOC to the coastal ocean, up to ~14 times more than Ecklonia radiata and the understory assemblage combined. Reef‐scale DOC release was driven by seasonal changes in seaweed physiology rather than seaweed biomass.
Location: Australia
No related grants have been discovered for Ellie Paine.