المؤلفون: Duncan, RJ, Nielsen, D, Søreide, JE, Varpe, Ø, Tobin, MJ, Pitusi, V, Heraud, P, Petrou, K

مصطلحات موضوعية: 3103 Ecology, 3107 Microbiology

الوصف: Arctic sea-ice diatoms fuel polar marine food webs as they emerge from winter darkness into spring. Through their photosynthetic activity they manufacture the nutrients and energy that underpin secondary production. Sea-ice diatom abundance and biomolecular composition vary in space and time. With climate change causing short-term extremes and long-term shifts in environmental conditions, understanding how and in what way diatoms adjust biomolecular stores with environmental perturbation is important to gain insight into future ecosystem energy production and nutrient transfer. Using synchrotron-based Fourier transform infrared microspectroscopy, we examined the biomolecular composition of five dominant sea-ice diatom taxa from landfast ice communities covering a range of under-ice light conditions during spring, in Svalbard, Norway. In all five taxa, we saw a doubling of lipid and fatty acid content when light transmitted to the ice-water interface was >5% but <15% (85%-95% attenuation through snow and ice). We determined a threshold around 15% light transmittance after which biomolecular synthesis plateaued, likely because of photoinhibitory effects, except for Navicula spp., which continued to accumulate lipids. Increasing under-ice light availability led to increased energy allocation towards carbohydrates, but this was secondary to lipid synthesis, whereas protein content remained stable. It is predicted that under-ice light availability will change in the Arctic, increasing because of sea-ice thinning and potentially decreasing with higher snowfall. Our findings show that the nutritional content of sea-ice diatoms is taxon-specific and linked to these changes, highlighting potential implications for future energy and nutrient supply for the polar marine food web.

وصف الملف: application/pdf

العلاقة: ISME Commun; ISME Commun, 2024, 4, (1), pp. ycad010; http://hdl.handle.net/10453/175588Test

الإتاحة: http://hdl.handle.net/10453/175588Test

المؤلفون: Bey, E, Hughes, C, Hogg, K, Chance, R, Petrou, K

مصطلحات موضوعية: 0399 Other Chemical Sciences, 0402 Geochemistry, 0405 Oceanography, Oceanography, 3703 Geochemistry, 3708 Oceanography

الوصف: Phytoplankton in marine surface waters play a key role in the global iodine cycle. The biologically-mediated iodide production under future scenarios is limited. Here we compare growth, iodate to iodide conversion rate and membrane permeability in the diatom Chaetoceros sp. (CCMP 1690) grown under seawater carbonate chemistry conditions projected for 2100 (1000 ppm) and pre-industrial (280 ppm) conditions. We found no effect of CO2 on growth rates, but a significantly higher cell yield under high CO2, suggesting sustained growth from relief from carbon limitation. Cell normalised iodate uptake (16.73 ± 0.92 amol IO3− cell−1) and iodide production (8.61 ± 0.15 amol I− cell−1) was lower in cultures grown at high pCO2 than those exposed to pre-industrial conditions (21.29 ± 2.37 amol IO3− cell−1, 11.91 ± 1.49 amol I− cell−1, respectively). Correlating these measurements with membrane permeability, we were able to ascertain that iodide conversion rates were not linked to cell permeability and that the processes of mediated iodate loss and diatom-iodide formation are decoupled. These findings are the first to implicate OA in driving a potential shift in diatom-mediated iodate reduction. If our results are indicative of diatom-mediated iodine cycling in 2100, future surface ocean conditions could experience reduced rates of iodide production by Chaetoceros spp., potentially lowering iodide concentrations in ocean regions dominated by this group. These changes have the potential to impact ozone cycling and new particle formation in the atmosphere.

وصف الملف: application/pdf

العلاقة: Marine Chemistry; Marine Chemistry, 2023, 257; http://hdl.handle.net/10453/175594Test

الإتاحة: http://hdl.handle.net/10453/175594Test

المؤلفون: Duncan, RJ, Petrou, K

مصطلحات موضوعية: 0403 Geology, 0907 Environmental Engineering, 0909 Geomatic Engineering

الوصف: Microalgae growing on the underside of sea ice are key primary producers in polar marine environments. Their nutritional status, determined by their macromolecular composition, contributes to the region’s biochemistry and the unique temporal and spatial characteristics of their growth makes them essential for sustaining polar marine food webs. Here, we review the plasticity and taxonomic diversity of sea ice microalgae macromolecular composition, with a focus on how different environmental conditions influence macromolecular production and partitioning within cells and communities. The advantages and disadvantages of methodologies for assessing macromolecular composition are presented, including techniques that provide high throughput, whole macromolecu-lar profile and/or species-specific resolution, which are particularly recommended for future studies. The directions of environmentally driven macromolecular changes are discussed, alongside antici-pated consequences on nutrients supplied to the polar marine ecosystem. Given that polar regions are facing accelerated rates of environmental change, it is argued that a climate change signature will become evident in the biochemical composition of sea ice microalgal communities, highlighting the need for further research to understand the synergistic effects of multiple environmental stressors. The importance of sea ice microalgae as primary producers in polar marine ecosystems means that ongoing research into climate-change driven macromolecular phenotyping is critical to understanding the implications for the regions biochemical cycling and carbon transfer.

وصف الملف: application/pdf

العلاقة: Geosciences (Switzerland); Geosciences (Switzerland), 2022, 12, (1), pp. 38; http://hdl.handle.net/10453/155343Test

الإتاحة: http://hdl.handle.net/10453/155343Test

المؤلفون: Petrou, K., Nielsen, D. A.

المصدر: Biogeochemistry, 2018 Nov 01. 141(2), 265-271.

الوصول الحر: https://www.jstor.org/stable/48721035Test

المؤلفون: Doblin, MA, Petrou, K, Sinutok, S, Seymour, JR, Messer, LF, Brown, MV, Norman, L, Everett, JD, McInnes, AS, Ralph, PJ, Thompson, PA, Hassler, CS

وصف الملف: application/pdf

العلاقة: http://purl.org/au-research/grants/arc/DP1092892Test; http://purl.org/au-research/grants/arc/DP120102764Test; http://purl.org/au-research/grants/arc/DP140101340Test; http://purl.org/au-research/grants/arc/FT130100218Test; PeerJ Preprints; PeerJ Preprints, 2016; http://hdl.handle.net/10453/155352Test

الإتاحة: http://hdl.handle.net/10453/155352Test

المؤلفون: Fernandez, E, Ostrowski, M, Siboni, N, Seymour, JR, Petrou, K

الوصف: Dimethylsulfoniopropionate (DMSP) is a key organic sulfur compound that is produced by many phytoplankton and macrophytes and is ubiquitous in marine environments. Following its release into the water column, DMSP is primarily metabolised by heterotrophic bacterioplankton, but recent evidence indicates that non-DMSP producing phytoplankton can also assimilate DMSP from the surrounding environment. In this study, we examined the uptake of DMSP by communities of bacteria and phytoplankton within the waters of the Great Barrier Reef (GBR), Australia. We incubated natural GBR seawater with DMSP and quantified the uptake of DMSP by different fractions of the microbial community (>8 µm, 3-8 µm, <3 µm). We also evaluated how microbial community composition and the abundances of DMSP degrading genes are influenced by elevated dissolved DMSP levels. Our results showed uptake and accumulation of DMSP in all size fractions of the microbial community, with the largest fraction (>8 µm) forming the dominant sink, increasing in particulate DMSP by 44-115% upon DMSP enrichment. Longer-term incubations showed however, that DMSP retention was short lived (<24 h) and microbial responses to DMSP enrichment differed depending on the community carbon and sulfur demand. The response of the microbial communities from inside the reef indicated a preference towards cleaving DMSP into the climatically active aerosol dimethyl sulfide (DMS), whereas communities from the outer reef were sulfur and carbon limited, resulting in more DMSP being utilised by the cells. Our results show that DMSP uptake is shared across members of the microbial community, highlighting larger phytoplankton taxa as potentially relevant DMSP reservoirs and provide new information on sulfur cycling as a function of community metabolism in deeper, oligotrophic GBR waters.

وصف الملف: Electronic; application/pdf

العلاقة: http://purl.org/au-research/grants/arc/DP140101045Test; Microorganisms; Microorganisms, 2021, 9, (9), pp. 1891-1891; http://hdl.handle.net/10453/151727Test

الإتاحة: http://hdl.handle.net/10453/151727Test

المؤلفون: Petrou, K, Ralph, PJ, Nielsen, DA

مصطلحات موضوعية: 05 Environmental Sciences, 06 Biological Sciences, 10 Technology, Microbiology, Animals, Anthozoa, Ecosystem, Symbiosis, Photosynthesis, Foraminifera, Coral Reefs

الوصف: Light underpins the health and function of coral reef ecosystems, where symbiotic partnerships with photosynthetic algae constitute the life support system of the reef. Decades of research have given us detailed knowledge of the photoprotective capacity of phototrophic organisms, yet little is known about the role of the host in providing photoprotection in symbiotic systems. Here we show that the intracellular symbionts within the large photosymbiotic foraminifera Marginopora vertebralis exhibit phototactic behaviour, and that the phototactic movement of the symbionts is accomplished by the host, through rapid actin-mediated relocation of the symbionts deeper into the cavities within the calcium carbonate test. Using a photosynthetic inhibitor, we identified that the infochemical signalling for host regulation is photosynthetically derived, highlighting the presence of an intimate communication between the symbiont and the host. Our results emphasise the central importance of the host in photosymbiotic photoprotection via a new mechanism in foraminifera that can serve as a platform for exploring host-symbiont communication in other photosymbiotic organisms.

وصف الملف: Print-Electronic; application/pdf

العلاقة: ISME Journal; ISME Journal, 2017, 11, (2), pp. 453-462; http://hdl.handle.net/10453/147727Test

الإتاحة: http://hdl.handle.net/10453/147727Test

المؤلفون: Sheehan, CE, Nielsen, DA, Petrou, K

مصطلحات موضوعية: 0405 Oceanography, 0602 Ecology, 0608 Zoology, Marine Biology & Hydrobiology

الوصف: © Inter-Research 2020. Microalgae form the base of the Antarctic marine food web and through their conversion of nutrients into biomass, are the principal source of energy for higher trophic levels. Environmental conditions strongly influence microalgal photophysiology, biochemistry and macromol ecular composition, which has implications for the quality and quantity of energy available for transfer through the food web. Here we assessed the photosynthetic performance, biochemical (dimethylsulfoniopropionate; DMSP) and macromolecular composition (lipids, carbohydrates and proteins) of selected diatoms sampled from 2 distinct Antarctic marine environments, namely the late spring bottom sea ice (sympagic) and near-shore ice-free coastal waters (pelagic). The photosynthetic efficiency and photoprotective capacity of the communities differed significantly, and chlorophyll a-specific gross primary productivity was 4-fold greater in the pelagic community. At the community level, pelagic microalgae had the highest DMSP content (1.4 nmol [μg chl a]-1) and the highest potential rates of DMSP lyase activity (0.87 nmol [μg chl a]-1 h-1). Comparisons within each community showed taxon-specific differences in macromolecular composition, which were strongest amongst the sympagic diatoms. Comparing across communities, pelagic diatoms had lower lipid to protein ratios, whereas sympagic diatoms were lipid rich and had significantly higher content of unsaturated fatty acids. These findings show variability in the physiology and nutritional quality of the base of the food web depending on habitat and taxonomic group and emphasise the importance of the sympagic community for providing a concentrated source of high-energy compounds during the pulsed productivity events for key grazers such as krill to survive through long dark winters.

وصف الملف: application/pdf

العلاقة: Marine Ecology Progress Series; Marine Ecology Progress Series, 2020, 640, pp. 45-61; http://hdl.handle.net/10453/145920Test

الإتاحة: http://hdl.handle.net/10453/145920Test

المؤلفون: Sheehan, CE, Baker, KG, Nielsen, DA, Petrou, K

مصطلحات موضوعية: 04 Earth Sciences, 05 Environmental Sciences, 06 Biological Sciences, Marine Biology & Hydrobiology

الوصف: © 2020, Springer Nature Switzerland AG. Temperature plays a fundamental role in determining phytoplankton community structure, distribution, and abundance. With climate models predicting increases in ocean surface temperatures of up to 3.2°C by 2100, there is a genuine need to acquire data on the phenotypic plasticity, and thus performance, of phytoplankton in relation to temperature. We investigated the effects of temperature (14–28°C) on the growth, morphology, productivity, silicification and macromolecular composition of the marine diatom Thalassiosira pseudonana. Optimum growth rate and maximum P:R ratio were obtained around 21°C. Cell volume and chlorophyll a increased with temperature, as did lipids and proteins. One of the strongest temperature-induced shifts was the higher silicification rates at low temperature. Our results reveal temperature-driven responses in physiological, morphological and biochemical traits in T. pseudonana; whereby at supra-optimal temperatures cells grew slower, were larger, had higher chlorophyll and protein content but reduced silicification, while those exposed to sub-optimal temperatures were smaller, heavily silicified with lower lipid and chlorophyll content. If these conserved across species, our findings indicate that as oceans warm, we may see shifts in diatom phenotypes and community structure, with potential biogeochemical consequences of higher remineralisation and declines in carbon and silicon export to the ocean interior.

وصف الملف: application/pdf

العلاقة: Hydrobiologia; Hydrobiologia, 2020, 847, (20), pp. 4233-4248; http://hdl.handle.net/10453/145942Test

الإتاحة: http://hdl.handle.net/10453/145942Test

المؤلفون: Hurtado-McCormick, V, Kahlke, T, Petrou, K, Jeffries, T, Ralph, PJ, Seymour, JR

مصطلحات موضوعية: 0502 Environmental Science and Management, 0503 Soil Sciences, 0605 Microbiology

الوصف: [This corrects the article DOI:10.3389/fmicb.2019.01011.].

وصف الملف: Electronic-eCollection; application/pdf

العلاقة: Frontiers in Microbiology; Frontiers in Microbiology, 2021, 12, pp. 642964; http://hdl.handle.net/10453/150533Test

الإتاحة: http://hdl.handle.net/10453/150533Test