@article {chauhan_size-dependent_2024,
	title = {Size-dependent dynamics of the internal carbon pool drive isotopic vital effects in calcifying phytoplankton},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {373},
	year = {2024},
	pages = {35{\textendash}51},
	abstract = {Isotopic offsets in biogenic calcite from equilibrium values can provide unique insights into the physiology and mechanisms of carbon regulation in calcifying phytoplankton. This study examines the impact of varying CO2 (controlled via pH) on five coccolithophore species chosen for varied cell sizes, physiology, and calcification. The study investigates isotopic offsets in coccolith calcite and organic matter, in relation to carbon demand and supply ({\textmu}/CO2). Species-specific CO2 and/or pH optima for growth ({\textmu}opt) were derived from variations in growth rates with varying CO2 concentrations. Growth rates for all species declined with rising CO2 (decreasing pH) due to H+-driven inhibition. C. braarudii and C. leptoporus exhibited {\textmu}opt at high CO2 concentrations (suggesting high carbon-demand) and limited growth under low CO2 (high pH) suggesting carbon limitation. Under low CO2 supply, when growth rates were CO2-limited, both species exhibited coincident isotopic depletion in calcite and organic matter as a consequence of CO2 diffusion into the cell that experienced no equilibration as a result of a highly depleted internal carbon pool. In these two species, isotopic values in calcite remained unaffected by growth rates and CO2 concentration ({\textmu}/CO2) when CO2 was sufficient for optimal growth. G. huxleyi and G. oceanica displayed optima for growth ({\textmu}opt) at low CO2 concentrations and showed no growth limitation under low CO2 (indicating low carbon-demand). Both species experienced depleted (negative) vital effects caused by an excess of CO2 diffusioninto the small internal carbon pool of the cell when diffusive carbon supply outpaced low demand (low {\textmu}/CO2). Enriched (positive) vital effects were observed under low carbon supply and high demand, likely due to increased HCO3{\textendash} uptake and diffusive CO2 loss from the intracellular carbon pooldue to a lower intracellular pH than the seawater pH. C. carterae exhibited a {\textmu}opt at intermediate CO2 concentrations and isotopically equilibrated intracellular carbon pool such that δ13C values in calcite and organic matter suggested a shared carbon pool. This study illustrates that pH and CO2 driven vital effects and fractionation into organic matter indicate the residence time for carbon in the intracellular carbon pool, where the size of the pool is proportional to cell size. Due to the increased buffering afforded by a larger pool, C. leptoporus and C. carterae may have elevated intracellular pH which minimises CO2 leakage, whereas vital effects in G. huxleyi and G. oceanica are caused by CO2 diffusion in or out of their small internal carbon pool with limited buffering capacity owing to its small size.},
	keywords = {Carbon demand and supply, Carbon residence time, coccolithophores, Internal carbon pool, RCC1130, RCC1198, RCC1314, Vital effects},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2024.03.033},
	url = {https://www.sciencedirect.com/science/article/pii/S0016703724001571},
	author = {Chauhan, Nishant and Rickaby, Rosalind E. M.}
}
@article {dedman_shotgun_2023,
	title = {Shotgun proteomics reveals temperature-dependent regulation of major nutrient metabolism in coastal Synechococcus sp. WH5701},
	journal = {Algal Research},
	year = {2023},
	month = {oct},
	pages = {103279},
	abstract = {Marine cyanobacteria are major contributors to the oceanic carbon sink and are predicted to increase in numbers in the future warmed ocean. As a result, the influence of marine cyanobacteria on marine biogeochemical cycling will likely be enhanced. Associated with elevations in temperature the ocean will undergo increased stratification, reducing supply of essential nutrients to upper phototrophic layers. It is therefore critical that we resolve the manners by which cyanobacteria respond to variations in temperature, and consequences for major nutrient metabolism which may ultimately direct global biogeochemistry and trophic transfer. In this study we use the coastal Synechococcus sp. WH5701 to examine proteomic alterations in major nutrient (C, N and P) metabolic pathways following exposure to varying temperature. In response to temperature treatments, Synechococcus displayed higher rates of growth and photosynthetic efficiency when temperatures were raised from 17 {\textdegree}C to 23 {\textdegree}C and 28 {\textdegree}C, associated with a significant \textasciitilde30{\textendash}40 \% alteration in the cellular proteome. As temperatures increased, proteomic investment towards photosynthetic machinery appeared up-regulated, whilst abundance of RuBisCO was reduced, associated with an apparent alteration in CCM composition and carbon metabolism. N demand appeared to increase in-line with temperature, associated with alterations in the GS-GOGAT pathway, likely due to increased demand for and efficiency of protein synthesis. In contrast, P demand at the highest temperature appeared reduced as investment in the ribosome declines due to improved translation efficiency, whilst luxury P-storage appeared a feature of growth at low temperature. It appears likely that as seawater temperatures rise under ocean warming, the biochemical composition of cyanobacteria will be altered, increasing cellular C- and N- to P ratios, ultimately impacting upon their contribution to oceanic biogeochemical cycling.},
	keywords = {climate change, Ocean warming, phytoplankton, Proteomics: Marine biogeochemistry, rcc1084},
	issn = {2211-9264},
	doi = {10.1016/j.algal.2023.103279},
	url = {https://www.sciencedirect.com/science/article/pii/S2211926423003120},
	author = {Dedman, Craig J. and Barton, Samuel and Fournier, Marjorie and Rickaby, Rosalind E. M.}
}
@article {zhang_stimulating_2023,
	title = {Stimulating and toxic effect of chromium on growth and photosynthesis of a marine chlorophyte},
	journal = {New Phytologist},
	volume = {n/a},
	number = {n/a},
	year = {2023},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/nph.19376},
	abstract = {Marine phytoplankton can interchange trace metals in various biochemical functions, particularly under metal-limiting conditions. Here, we investigate the stimulating and toxicity effect of chromium (Cr) on a marine Chlorophyceae Osetreococcus tauri under Fe-replete and Fe-deficient conditions. We determined the growth, photosynthesis, and proteome expressions of Osetreococcus tauri cultured under different Cr and Fe concentrations. In Fe-replete conditions, the presence of Cr(VI) stimulated significantly the growth rate and the maximum yield of photochemistry of photosystem II (Fv/Fm) of the phytoplankton, while the functional absorption cross-section of photosystem II (σPSII) did not change. Minor additions of Cr(VI) partially rescued phytoplankton growth under Fe-limited conditions. Proteomic analysis of this alga grown in Fe-replete normal and Fe-replete with Cr addition media (10 μM Cr) showed that the presence of Cr significantly decreased the expression of phosphate-transporting proteins and photosynthetic proteins, while increasing the expression of proteins related to carbon assimilation. Cr can stimulate the growth and photosynthesis of O. tauri, but the effects are dependent on both the Cr(VI) concentration and the availability of Fe. The proteomic results further suggest that Cr(VI) addition might significantly increase starch production and carbon fixation.},
	keywords = {chromium, Photosynthesis, phytoplankton, proteomics, RCC1, RCC1242, trace metal},
	issn = {1469-8137},
	doi = {10.1111/nph.19376},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.19376},
	author = {Zhang, Qiong and Charles, Philip D. and Bendif, El Mahdi and Hester, Svenja S. and Mohammad, Shabaz and Rickaby, Rosalind E. M.}
}
@article {Wilson2019,
	title = {Susceptibility of algae to Cr toxicity reveals contrasting metal management strategies},
	journal = {Limnology and Oceanography},
	volume = {64},
	number = {5},
	year = {2019},
	note = {Publisher: John Wiley \& Sons, Ltd tex.mendeley-tags: RCC1,RCC1242,RCC4221,RCC950},
	month = {sep},
	pages = {2271{\textendash}2282},
	abstract = {At the Paleozoic{\textendash}Mesozoic boundary, the dominance of marine eukaryotic algae shifted from the green (chlorophyll b) to the red (chlorophyll c) superfamily. Selection pressures caused by the bioavailability of trace metals associated with increasing oxygenation of the ocean may have played a key role in this algal revolution. From a scan of elemental compositions, a significant difference in the cellular Cr/P quota was found between the two superfamilies. Here, the different responses to high levels of Cr exposure reveal contrasting strategies for metal uptake and homeostasis in these algal lineages. At high Cr(VI) concentrations, red lineages experience growth inhibition through reduced photosynthetic capability, while green lineages are completely unaffected. Moreover, Cr(VI) has a more significant impact on the metallomes of red lineage algae, in which metal/P ratios increased with increasing Cr(VI) concentration for many trace elements. Green algae have higher specificity transporters to prevent Cr(VI) from entering the cell, and more specific intracellular stores of Cr within the membrane fraction than the red algae, which accumulate more Cr mistakenly in the cytosol fraction via lower affinity transport mechanisms. Green algal approaches require greater nutrient investments in the more numerous transport proteins required and management of specific metals, a strategy better adapted to the resource-rich coastal waters. By contrast, the red algae are nutrient-efficient with fewer and less discriminate metal transporters, which can be fast and better adapted in the oligotrophic, oxygenated open ocean, which has prevailed since the deepening of the oxygen minimum zones at the start of the Mesozoic era.},
	keywords = {RCC1, RCC1242, RCC4221, RCC950},
	issn = {0024-3590},
	doi = {10.1002/lno.11183},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lno.11183},
	author = {Wilson, Will and Zhang, Qiong and Rickaby, Rosalind E. M.}
}
