Corrigendum: A mechanistic model of macromolecular allocation, elemental stoichiometry, and growth rate in phytoplankton.

[This corrects the article DOI: 10.3389/fmicb.2020.

Image-derived indicators of phytoplankton community responses to Pseudo-nitzschia blooms.

Phytoplankton populations in the natural environment interact with each other. Despite rising global concern with Pseudo-nitzschia blooms, which can produce the potent neurotoxin domoic acid, we still do not fully understand how other phytoplankton genera respond to the presence of Pseudo-nitzschia. Here, we used a 4-year high-resolution imaging dataset for 9 commonly found phytoplankton genera in Narragansett Bay, alongside environmental data, to identify potential interactions between phytoplankton genera and their response to elevated Pseudo-nitzschia abundance.

Rapid mode switching facilitates the growth of : A model analysis.

is one of the dominant dinitrogen (N) fixers in the ocean, influencing global carbon and nitrogen cycles through biochemical reactions. Although its photosynthetic activity fluctuates rapidly, the physiological or ecological advantage of this fluctuation is unclear. We develop a metabolic model of that can perform daytime N fixation.

Crocosphaera watsonii - A widespread nitrogen-fixing unicellular marine cyanobacterium.

Crocosphaera watsonii is a unicellular N-fixing (diazotrophic) cyanobacterium observed in tropical and subtropical oligotrophic oceans. As a diazotroph, it can be a source of bioavailable nitrogen (N) to the microbial community in N-limited environments, and this may fuel primary production in the regions where it occurs. Crocosphaera watsonii has been the subject of intense study, both in culture and in field populations.

Metabolic trade-offs constrain the cell size ratio in a nitrogen-fixing symbiosis.

Biological dinitrogen (N) fixation is a key metabolic process exclusively performed by prokaryotes, some of which are symbiotic with eukaryotes. Species of the marine haptophyte algae Braarudosphaera bigelowii harbor the N-fixing endosymbiotic cyanobacteria UCYN-A, which might be evolving organelle-like characteristics. We found that the size ratio between UCYN-A and their hosts is strikingly conserved across sublineages/species, which is consistent with the size relationships of organelles in this symbiosis and other species.

Patterns in the temporal complexity of global chlorophyll concentration.

Decades of research have relied on satellite-based estimates of chlorophyll-a concentration to identify oceanographic processes and plan in situ observational campaigns; however, the patterns of intrinsic temporal variation in chlorophyll-a concentration have not been investigated on a global scale. Here we develop a metric to quantify time series complexity (i.e.

Projecting global biological N fixation under climate warming across land and ocean.

Biological N fixation sustains the global inventory of nitrogenous nutrients essential for the productivity of terrestrial and marine ecosystems. Like most metabolic processes, rates of biological N fixation vary strongly with temperature, making it sensitive to climate change, but a global projection across land and ocean is lacking. Here we use compilations of field and laboratory measurements to reveal a relationship between N fixation rates and temperature that is similar in both domains despite large taxonomic and environmental differences.

Saturating growth rate against phosphorus concentration explained by macromolecular allocation.

The Monod equation has been used to represent the relationship between growth rate and the environmental nutrient concentration under the limitation of this respective nutrient. This model often serves as a means to connect microorganisms to their environment, specifically in ecosystem and global models. Here, we use a simple model of a marine microorganism cell to illustrate the model's ability to capture the same relationship as Monod, while highlighting the additional physiological details our model provides.

Coexistence of Dominant Marine Phytoplankton Sustained by Nutrient Specialization.

and are the two dominant picocyanobacteria in the low-nutrient surface waters of the subtropical ocean, but the basis for their coexistence has not been quantitatively demonstrated. Here, we combine microcosm experiments and an ecological model to show that this coexistence can be sustained by specialization in the uptake of distinct nitrogen (N) substrates at low-level concentrations that prevail in subtropical environments. In field incubations, the response of both and to nanomolar N amendments demonstrates N limitation of growth in both populations.

Light-driven Proton Pumps as a Potential Regulator for Carbon Fixation in Marine Diatoms.

Diatoms are a major phytoplankton group responsible for approximately 20% of carbon fixation on Earth. They perform photosynthesis using light-harvesting chlo-rophylls located in plastids, an organelle obtained through eukaryote-eukaryote endosymbiosis. Microbial rhodopsin, a photoreceptor distinct from chlo-rophyll-based photosystems, was recently identified in some diatoms.

A diazotrophy-ammoniotrophy dual growth model for the sulfate reducing bacterium var. Hildenborough.

Sulfate reducing bacteria (SRB) comprise one of the few prokaryotic groups in which biological nitrogen fixation (BNF) is common. Recent studies have highlighted SRB roles in N cycling, particularly in oligotrophic coastal and benthic environments where they could contribute significantly to N input. Most studies of SRB have focused on sulfur cycling and SRB growth models have primarily aimed at understanding the effects of electron sources, with N usually provided as fixed-N (nitrate, ammonium).

Better together? Lessons on sociality from Trichodesmium.

The N-fixing cyanobacterium Trichodesmium is an important player in the oceanic nitrogen and carbon cycles. Trichodesmium occurs both as single trichomes and as colonies containing hundreds of trichomes. In this review, we explore the benefits and disadvantages of colony formation, considering physical, chemical, and biological effects from nanometer to kilometer scale.

High Growth Rate of Diatoms Explained by Reduced Carbon Requirement and Low Energy Cost of Silica Deposition.

The rapid growth of diatoms makes them one of the most pervasive and productive types of plankton in the world's ocean, but the physiological basis for their high growth rates remains poorly understood. Here, we evaluate the factors that elevate diatom growth rates, relative to other plankton, using a steady-state metabolic flux model that computes the photosynthetic C source from intracellular light attenuation and the carbon cost of growth from empirical cell C quotas, across a wide range of cell sizes. For both diatoms and other phytoplankton, growth rates decline with increased cell volume, consistent with observations, because the C cost of division increases with size faster than photosynthesis.

Saturating relationship between phytoplankton growth rate and nutrient concentration explained by macromolecular allocation.

Phytoplankton account for about a half of photosynthesis in the world, making them a key player in the ecological and biogeochemical systems. One of the key traits of phytoplankton is their growth rate because it indicates their productivity and affects their competitive capability. The saturating relationship between phytoplankton growth rate and environmental nutrient concentration has been widely observed yet the mechanisms behind the relationship remain elusive.

Modeling the elemental stoichiometry and silicon accumulation in diatoms.

Diatoms are important microorganisms involved in global primary production, nutrient cycling, and carbon sequestration. A unique feature of diatoms is their silica frustules, which impact sinking speed, defense against predators and viruses, and growth cycling. Thus, frustules are inherently linked to their role in ecosystems and biogeochemical cycles.

The balance between photosynthesis and respiration explains the niche differentiation between and .

and are both unicellular, nitrogen-fixing cyanobacteria that prefer different environments. Whereas mainly lives in nutrient-deplete, open oceans, is more common in coastal, nutrient-rich regions. Despite their physiological similarities, the factors separating their niches remain elusive.

Quantitative Analysis of the Trade-Offs of Colony Formation for .

There is considerable debate about the benefits and trade-offs for colony formation in a major marine nitrogen fixer, . To quantitatively analyze the trade-offs, we developed a metabolic model based on carbon fluxes to compare the performance of colonies and free trichomes under different scenarios. Despite reported reductions in carbon fixation and nitrogen fixation rates for colonies relative to free trichomes, we found that model colonies can outperform individual cells in several cases.

N Fixation in Does Not Require Spatial Segregation from Photosynthesis.

The dominant marine filamentous N fixer, , conducts photosynthesis and N fixation during the daytime. Because N fixation is sensitive to O, some previous studies suggested that spatial segregation of N fixation and photosynthesis is essential in . However, this hypothesis conflicts with some observations where all the cells contain both photosystems and the N-fixing enzyme nitrogenase.

Sinking Trichodesmium fixes nitrogen in the dark ocean.

The photosynthetic cyanobacterium Trichodesmium is widely distributed in the surface low latitude ocean where it contributes significantly to N fixation and primary productivity. Previous studies found nifH genes and intact Trichodesmium colonies in the sunlight-deprived meso- and bathypelagic layers of the ocean (200-4000 m depth). Yet, the ability of Trichodesmium to fix N in the dark ocean has not been explored.

Impact of warming on aquatic body sizes explained by metabolic scaling from microbes to macrofauna.

Rising temperatures are associated with reduced body size in many marine species, but the biological cause and generality of the phenomenon is debated. We derive a predictive model for body size responses to temperature and oxygen (O) changes based on thermal and geometric constraints on organismal O supply and demand across the size spectrum. The model reproduces three key aspects of the observed patterns of intergenerational size reductions measured in laboratory warming experiments of diverse aquatic ectotherms (i.

as a Major Consumer of Fixed Nitrogen.

Crocosphaera watsonii (hereafter referred to as ) is a key nitrogen (N) fixer in the ocean, but its ability to consume combined-N sources is still unclear. Using microcosm incubations with an ecological model, we show that has high competitive capability both under low and moderately high combined-N concentrations. In field incubations, accounted for the highest consumption of ammonium and nitrate, followed by picoeukaryotes.