ORCID Profile
0000-0002-8340-3133
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Publisher: Inter-Research Science Center
Date: 03-12-2014
DOI: 10.3354/MEPS11009
Publisher: Frontiers Media SA
Date: 05-04-2016
Publisher: American Society for Microbiology
Date: 11-2014
DOI: 10.1128/AEM.01962-14
Abstract: Understanding the interconnectivity of oceanic carbon and nitrogen cycles, specifically carbon and nitrogen fixation, is essential in elucidating the fate and distribution of carbon in the ocean. Traditional techniques measure either organism abundance or biochemical rates. As such, measurements are performed on separate s les and on different time scales. Here, we developed a method to simultaneously quantify organisms while estimating rates of fixation across time and space for both carbon and nitrogen. Tyramide signal lification fluorescence in situ hybridization (TSA-FISH) of mRNA for functionally specific oligonucleotide probes for rbcL (ribulose-1,5-bisphosphate carboxylase/oxygenase carbon fixation) and nifH (nitrogenase nitrogen fixation) was combined with flow cytometry to measure abundance and estimate activity. Cultured s les representing a ersity of phytoplankton (cyanobacteria, coccolithophores, chlorophytes, diatoms, and dinoflagellates), as well as environmental s les from the open ocean (Gulf of Mexico, USA, and southeastern Indian Ocean, Australia) and an estuary (Galveston Bay, Texas, USA), were successfully hybridized. Strong correlations between positively tagged community abundance and 14 C/ 15 N measurements are presented. We propose that these methods can be used to estimate carbon and nitrogen fixation in environmental communities. The utilization of mRNA TSA-FISH to detect multiple active microbial functions within the same s le will offer increased understanding of important biogeochemical cycles in the ocean.
Publisher: Public Library of Science (PLoS)
Date: 22-01-2016
Publisher: American Geophysical Union (AGU)
Date: 08-2015
DOI: 10.1002/2015GB005194
Publisher: Wiley
Date: 20-07-2022
DOI: 10.1111/GCB.16330
Abstract: Despite their relatively high thermal optima ( T opt ), tropical taxa may be particularly vulnerable to a rising baseline and increased temperature variation because they live in relatively stable temperatures closer to their T opt . We examined how microbial eukaryotes with differing thermal histories responded to temperature fluctuations of different litudes (0 control, ±2, ±4°C) around mean temperatures below or above their T opt . Cosmopolitan dinoflagellates were selected based on their distinct thermal traits and included two species of the same genus (tropical and temperate Coolia spp.), and two strains of the same species maintained at different temperatures for generations (tropical Amphidinium massartii control temperature and high temperature, CT and HT, respectively). There was a universal decline in population growth rate under temperature fluctuations, but strains with narrower thermal niche breadth (temperate Coolia and HT) showed ~10% greater reduction in growth. At suboptimal mean temperatures, cells in the cool phase of the fluctuation stopped iding, fixed less carbon (C) and had enlarged cell volumes that scaled positively with elemental C, N, and P and C:Chlorophyll‐ a . However, at a supra‐optimal mean temperature, fixed C was directed away from cell ision and novel trait combinations developed, leading to greater phenotypic ersity. At the molecular level, heat‐shock proteins, and chaperones, in addition to transcripts involving genome rearrangements, were upregulated in CT and HT during the warm phase of the supra‐optimal fluctuation (30 ± 4°C), a stress response indicating protection. In contrast, the tropical Coolia species upregulated major energy pathways in the warm phase of its supra‐optimal fluctuation (25 ± 4°C), indicating a broadscale shift in metabolism. Our results demonstrate ergent effects between taxa and that temporal variability in environmental conditions interacts with changes in the thermal mean to mediate microbial responses to global change, with implications for biogeochemical cycling.
Publisher: PeerJ
Date: 25-04-2016
DOI: 10.7717/PEERJ.1973
Abstract: The intensification of western boundary currents in the global ocean will potentially influence meso-scale eddy generation, and redistribute microbes and their associated ecological and biogeochemical functions. To understand eddy-induced changes in microbial community composition as well as how they control growth, we targeted the East Australian Current (EAC) region to s le microbes in a cyclonic (cold-core) eddy (CCE) and the adjacent EAC. Phototrophic and diazotrophic microbes were more erse (2–10 times greater Shannon index) in the CCE relative to the EAC, and the cell size distribution in the CCE was dominated (67%) by larger micro-plankton $(\\geq 20\\lrm{\\mu }\\mathrm{m})$, as opposed to pico- and nano-sized cells in the EAC. Nutrient addition experiments determined that nitrogen was the principal nutrient limiting growth in the EAC, while iron was a secondary limiting nutrient in the CCE. Among the diazotrophic community, heterotrophic NifH gene sequences dominated in the EAC and were attributable to members of the gamma-, beta-, and delta-proteobacteria, while the CCE contained both phototrophic and heterotrophic diazotrophs, including Trichodesmium , UCYN-A and gamma-proteobacteria. Daily s ling of incubation bottles following nutrient amendment captured a cascade of effects at the cellular, population and community level, indicating taxon-specific differences in the speed of response of microbes to nutrient supply. Nitrogen addition to the CCE community increased picoeukaryote chlorophyll a quotas within 24 h, suggesting that nutrient uplift by eddies causes a ‘greening’ effect as well as an increase in phytoplankton biomass. After three days in both the EAC and CCE, diatoms increased in abundance with macronutrient (N, P, Si) and iron amendment, whereas haptophytes and phototrophic dinoflagellates declined. Our results indicate that cyclonic eddies increase delivery of nitrogen to the upper ocean to potentially mitigate the negative consequences of increased stratification due to ocean warming, but also increase the biological demand for iron that is necessary to sustain the growth of large-celled phototrophs and potentially support the ersity of diazotrophs over longer time-scales.
Publisher: Springer Science and Business Media LLC
Date: 31-01-2019
Publisher: Wiley
Date: 25-04-2018
DOI: 10.1002/LNO.10814
Publisher: Frontiers Media SA
Date: 30-08-2016
No related grants have been discovered for Allison McInnes.