Phytoplankton in a changing world: cell size and elemental stoichiometry
TL;DR: It is suggested that cell size and elemental stoichiometry are promising ecophysiological traits for modelling and tracking changes in phytoplankton community structure in response to climate change.
Abstract: Global increases in atmospheric CO2 and temperature are associated with changes in ocean chemistry and circulation, altering light and nutrient regimes. Resulting changes in phytoplankton community structure are expected to have a cascading effect on primary and export production, food web dynamics and the structure of the marine food web as well the biogeochemical cycling of carbon and bio-limiting elements in the sea. A review of current literature indicates cell size and elemental stoichiometry often respond predictably to abiotic conditions and follow biophysical rules that link environmental conditions to growth rates, and growth rates to food web interactions, and consequently to the biogeochemical cycling of elements. This suggests that cell size and elemental stoichiometry are promising ecophysiological traits for modelling and tracking changes in phytoplankton community structure in response to climate change. In turn, these changes are expected to have further impacts on phytoplankton community structure through as yet poorly understood secondary processes associated with trophic dynamics.
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TL;DR: This Review examines how several cyanobacterial eco-physiological traits, specifically, the ability to grow in warmer temperatures; buoyancy; high affinity for, and ability to store, phosphorus; nitrogen-fixation; akinete production; and efficient light harvesting, vary amongst cyanobacteria genera and may enable them to dominate in future climate scenarios.
609 citations
TL;DR: It is shown that specific plankton communities, from the surface and deep chlorophyll maximum, correlate with carbon export at 150 m and that the relative abundance of a few bacterial and viral genes can predict a significant fraction of the variability in carbon export in these regions.
Abstract: The biological carbon pump is the process by which CO2 is transformed to organic carbon via photosynthesis, exported through sinking particles, and finally sequestered in the deep ocean. While the intensity of the pump correlates with plankton community composition, the underlying ecosystem structure driving the process remains largely uncharacterized. Here we use environmental and metagenomic data gathered during the Tara Oceans expedition to improve our understanding of carbon export in the oligotrophic ocean. We show that specific plankton communities, from the surface and deep chlorophyll maximum, correlate with carbon export at 150 m and highlight unexpected taxa such as Radiolaria and alveolate parasites, as well as Synechococcus and their phages, as lineages most strongly associated with carbon export in the subtropical, nutrient-depleted, oligotrophic ocean. Additionally, we show that the relative abundance of a few bacterial and viral genes can predict a significant fraction of the variability in carbon export in these regions.
556 citations
TL;DR: The results suggest that warming and drought can increase C:N and C:P ratios in warm-dry and temperate-dry terrestrial ecosystems, especially, when high temperatures and drought coincide.
Abstract: This study examined the literature in ISI Web of Science to identify the effects that the main drivers of global change have on the nutrient concentrations and C:N:P stoichiometry of organisms and ecosystems, and examined their relationship to changes in ecosystem structure and function. We have conducted a meta-analysis by comparing C:N:P ratios of plants and soils subjected to elevated [CO2] with those subjected to ambient [CO2]. A second meta-analysis compared the C:N:P ratios of plants and soils that received supplemental N to simulate N deposition and those that did not receive supplemental N. On average, an experimental increase in atmospheric [CO2] increased the foliar C:N ratios of C3 grasses, forbs, and woody plants by 22%, but the foliar ratios of C4 grasses were unaffected. This trend may be enhanced in semi-arid areas by the increase in droughts that have been projected for the coming decades which can increase leaf C:N ratios. The available studies show an average 38% increase in foliar C:P ratios in C3 plants in response to elevated atmospheric [CO2], but no significant effects were observed in C4 grasses. Furthermore, studies that examine the effects of elevated atmospheric [CO2] on N:P ratio (on a mass basis) are warranted since its response remains elusive. N deposition increases the N:P ratio in the plants of terrestrial and freshwater ecosystems, and decreases plants and organic soil C:N ratio (25% on average for C3 plants), reducing soil and water N2 fixation capacity and ecosystem species diversity. In contrast, in croplands subjected to intense fertilization, mostly, animal slurries, a reduction in soil N:P ratio can occur because of the greater solubility and loss of N. In the open ocean, there are experimental observations showing an ongoing increase in P-limited areas in response to several of the factors that promote global change, including the increase in atmospheric [CO2] which increases the demand for P, the warming effect that leads to an increase in water column stratification, and increases in the N:P ratio of atmospheric inputs. Depending on the type of plant and the climate where it grows, warming can increase, reduce, or have no effect on foliar C:N ratios. The results suggest that warming and drought can increase C:N and C:P ratios in warm-dry and temperate-dry terrestrial ecosystems, especially, when high temperatures and drought coincide. Advances in this topic are a challenge because changes in stoichiometric ratios can favour different types of species and change ecosystem composition and structure.
488 citations
Cites background from "Phytoplankton in a changing world: ..."
...:P biomass ratios of phytoplankton (Finkel et al., 2010) (Fig....
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...In marine ecosystems, elevated [CO2] levels can increase the C:N and C:P biomass ratios of phytoplankton (Finkel et al., 2010) (Fig....
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...Increases in ambient temperature can increase respiration rates, which increases organic-C mineralization and, thus, counterbalance the direct effect of an increase in the C-storage capacity of an ecosystem caused by an increase in atmospheric [CO2] (Finkel et al., 2010; Ferreira et al., 2010)....
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...:P ratios caused by increases in atmospheric [CO2] (Finkel et al., 2010) might be exacerbated by the stratification of water caused by warming....
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...The predicted widespread increases in C:N and C:P ratios caused by increases in atmospheric [CO2] (Finkel et al., 2010) might be exacerbated by the stratification of water caused by warming....
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TL;DR: Relationships between NH4+ and NO3− metabolism have important implications for harmful algal blooms, development of nutrient criteria for management, and modeling of nutrient uptake by phytoplankton, particularly in conditions where eutrophication is increasing and the redox state of N loads is changing.
Abstract: Anthropogenic activities are altering total nutrient loads to many estuaries and freshwaters, resulting in high loads not only of total nitrogen (N), but in some cases, of chemically reduced forms, notably NH4+. Long thought to be the preferred form of N for phytoplankton uptake, NH4+ may actually suppress overall growth when concentrations are sufficiently high. NH4+ has been well known to be inhibitory or repressive for NO3‐ uptake and assimilation, but the concentrations of NH4+ that promote vs. repress NO3‐ uptake, assimilation, and growth in different phytoplankton groups and under different growth conditions are not well understood. Here, we review N metabolism first in a “generic” eukaryotic cell, and the contrasting metabolic pathways and regulation of NH4+ and NO3− when these substrates are provided individually under equivalent growth conditions. Then the metabolic interactions of these substrates are described when both are provided together, emphasizing the cellular challenge of balancing nutrient acquisition with photosynthetic energy balance in dynamic environments. Conditions under which dissipatory pathways such as dissimilatory NO3−/ NO2− reduction to NH4+ and photorespiration that may lead to growth suppression are highlighted. While more is known about diatoms, taxon-specific differences in NH4+ and NO3− metabolism that may contribute to changes in phytoplankton community composition when the composition of the N pool changes are presented. These relationships have important implications for harmful algal blooms, development of nutrient criteria for management, and modeling of nutrient uptake by phytoplankton, particularly in conditions where eutrophication is increasing and the redox state of N loads is changing.
453 citations
Cites background from "Phytoplankton in a changing world: ..."
...Cell size sets biophysical constraints on many aspects of physiology, including nutrient transport (e.g., Finkel et al. 2010 and references therein)....
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References
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01 Jan 2007
TL;DR: The first volume of the IPCC's Fourth Assessment Report as mentioned in this paper was published in 2007 and covers several topics including the extensive range of observations now available for the atmosphere and surface, changes in sea level, assesses the paleoclimatic perspective, climate change causes both natural and anthropogenic, and climate models for projections of global climate.
Abstract: This report is the first volume of the IPCC's Fourth Assessment Report. It covers several topics including the extensive range of observations now available for the atmosphere and surface, changes in sea level, assesses the paleoclimatic perspective, climate change causes both natural and anthropogenic, and climate models for projections of global climate.
32,826 citations
TL;DR: This work has developed a quantitative theory for how metabolic rate varies with body size and temperature, and predicts how metabolic theory predicts how this rate controls ecological processes at all levels of organization from individuals to the biosphere.
Abstract: Metabolism provides a basis for using first principles of physics, chemistry, and biology to link the biology of individual organisms to the ecology of populations, communities, and ecosystems. Metabolic rate, the rate at which organisms take up, transform, and expend energy and materials, is the most fundamental biological rate. We have developed a quantitative theory for how metabolic rate varies with body size and temperature. Metabolic theory predicts how metabolic rate, by setting the rates of resource uptake from the environment and resource allocation to survival, growth, and reproduction, controls ecological processes at all levels of organization from individuals to the biosphere. Examples include: (1) life history attributes, including devel- opment rate, mortality rate, age at maturity, life span, and population growth rate; (2) population interactions, including carrying capacity, rates of competition and predation, and patterns of species diversity; and (3) ecosystem processes, including rates of biomass production and respiration and patterns of trophic dynamics. Data compiled from the ecological literature strongly support the theoretical predictions. Even- tually, metabolic theory may provide a conceptual foundation for much of ecology, just as genetic theory provides a foundation for much of evolutionary biology.
6,017 citations
"Phytoplankton in a changing world: ..." refers background in this paper
...…fundamental constraints on the rate of acquiring (Munk and Riley, 1952; Duysens, 1956) and processing energy and materials from the environment (Brown et al., 2004), to influence evolution (Quigg et al., 2003; Bragg and Hyder, 2004; Finkel et al., 2005; Finkel et al., 2007b), food web…...
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...…phytoplankton size is an easily determined and promising trait for predicting physiological responses to environmental change that can be used to scale-up to ecological and biogeochemical processes; often referred to as the metabolic theory of ecology (Brown et al., 2004; López-Urrutia, 2008)....
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TL;DR: Evidence is presented to suggest that numbers of free bacteria are controlled by nanoplankton~c heterotrophic flagellates which are ubiquitous in the marine water column, thus providing the means for returning some energy from the 'microbial loop' to the conventional planktonic food chain.
Abstract: Recently developed techniques for estimating bacterial biomass and productivity indicate that bacterial biomass in the sea is related to phytoplankton concentration and that bacteria utilise 10 to 50 % of carbon fixed by photosynthesis. Evidence is presented to suggest that numbers of free bacteria are controlled by nanoplankton~c heterotrophic flagellates which are ubiquitous in the marine water column. The flagellates in turn are preyed upon by microzooplankton. Heterotrophic flagellates and microzooplankton cover the same size range as the phytoplankton, thus providing the means for returning some energy from the 'microbial loop' to the conventional planktonic food chain.
5,069 citations
"Phytoplankton in a changing world: ..." refers background in this paper
...…dominated by smaller zooplankton, ciliates and flagellates, and bacteria in the ocean surface, to dominance by larger copepods in the zooplankton and an increase in the biological pump due to the more rapid sedimentation of particulate matter (Pomeroy, 1974; Azam et al., 1983; Laws et al., 2000)....
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TL;DR: 13 models of the ocean–carbon cycle are used to assess calcium carbonate saturation under the IS92a ‘business-as-usual’ scenario for future emissions of anthropogenic carbon dioxide and indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.
Abstract: Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms—such as corals and some plankton—will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean–carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.
4,244 citations
Book Chapter•
01 Jan 2007
3,995 citations
"Phytoplankton in a changing world: ..." refers background in this paper
...Climate change over the next century is expected to modify ocean ice cover, temperature, precipitation, and circulation (Meehl et al., 2007), altering the environmental conditions that influence phytoplankton standing stock and primary production (Sarmiento et al., 2004; Irwin and Finkel, 2008)....
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...…the decadal scale, there is already clear evidence of increases in ocean temperature, decreases in ocean pH, strengthening in the westerly winds (Meehl et al., 2007), a decrease in summer sea ice in the high latitudes (Curran et al., 2003; Serreze et al., 2007), an increase in salinity in…...
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