The export of organic carbon from the surface ocean by sinking particles is an important, yet highly uncertain, component of the global carbon cycle. Here we introduce a mechanistic assessment of the ...global ocean carbon export using satellite observations, including determinations of net primary production and the slope of the particle size spectrum, to drive a food‐web model that estimates the production of sinking zooplankton feces and algal aggregates comprising the sinking particle flux at the base of the euphotic zone. The synthesis of observations and models reveals fundamentally different and ecologically consistent regional‐scale patterns in export and export efficiency not found in previous global carbon export assessments. The model reproduces regional‐scale particle export field observations and predicts a climatological mean global carbon export from the euphotic zone of ~6 Pg C yr−1. Global export estimates show small variation (typically < 10%) to factor of 2 changes in model parameter values. The model is also robust to the choices of the satellite data products used and enables interannual changes to be quantified. The present synthesis of observations and models provides a path for quantifying the ocean's biological pump.
Key Points
Global ocean carbon export is assessed using satellite observations
Reproduces field observations and predicts sensible patterns in export efficiency
Decadal‐scale trends are found in global export efficiency
Background
There is increasing recognition of the unique physical and psychosocial concerns of the growing population of cancer survivors. An emerging literature demonstrates that fear of cancer ...recurrence (FCR) is a problematic long‐term and late effect for cancer survivors. In fact, FCR is a top concern, and this article provides a necessary synthesis of the extant research evidence and theory.
Methods
Literature searches were conducted using databases including MEDLINE and PsychINFO using specified search terms including ‘fear of recurrence’ and ‘worry about recurrence’. A comprehensive narrative review summarizes early empirical findings on FCR including current definitions, assessment tools, clinical presentations, quality of life impact, prevalence, trajectory and risk factors. This paper also critically reviews the relevant theoretical frameworks to best understand these findings and considers multiple psychosocial treatment models that may have relevance for addressing FCR in the clinical setting.
Results
There is evidence of substantial prevalence and quality of life impact of FCR. Several theories (e.g. self‐regulation model of illness, a family‐based model, uncertainty in illness theory, social‐cognitive processing theory, terror management theory) directly or indirectly help conceptualize FCR and inform potential treatment options for those with clinically significant distress or impairment resulting from FCR.
Conclusions
Further investigation into FCR is warranted to promote evidence‐based care for this significant cancer survivorship concern.
Some antimicrobial peptides (AMPs) and membrane fusion-catalyzing peptides (FPs) stabilize bicontinuous inverted cubic (QII) phases. Previous authors proposed a topological rationale: since ...AMP-induced pores, fusion intermediates, and QII phases all have negative Gaussian curvature (NGC), peptides which produce NGC in one structure also do it in another. This assumes that peptides change the curvature energy of the lipid membranes. Here I test this with a Helfrich curvature energy model. First, experimentally, I show that lipid systems often used to study peptide NGC have NGC without peptides at higher temperatures. To determine the net effect of an AMP on NGC, the equilibrium phase behavior of the host lipids must be determined. Second, the model shows that AMPs must make large changes in the curvature energy to stabilize AMP-induced pores. Peptide-induced changes in elastic constants affect pores and QII phase differently. Changes in spontaneous curvature affect them in opposite ways. The observed correlation between QII phase stabilization and AMP activity doesn't show that AMPs act by lowering pore curvature energy. A different rationale is proposed. In theory, AMPs could simultaneously stabilize QII phase and pores by drastically changing two particular elastic constants. This could be tested by measuring AMP effects on the individual constants. I propose experiments to do that. Unlike AMPs, FPs must make only small changes in the curvature energy to catalyze fusion. It they act in this way, their fusion activity should correlate with their ability to stabilize QII phases.
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•Previous researchers observed a correlation of AMP & FP activity with QII phase stabilization.•Implication: peptides could act by reducing the curvature energy of pores & fusion intermediates.•Here that rationale is tested using simple curvature energy models.•FPs could act in this way. If so, their activity should correlate with QII phase stabilization.•AMPs are less likely to act in this way. Activity would not always correlate with effects on QII.
We investigate the bio‐optical footprints made by mesoscale eddies in the Sargasso Sea and the processes that create them through an eddy‐centric approach. Many (>10,000) eddies are identified and ...followed in time using satellite altimetry observations and the spatial ocean color patterns surrounding each eddy are assessed. We find through a sequence of statistical hypothesis tests that not one but several mechanisms (i.e., eddy pumping, eddy advection and eddy‐Ekman pumping) are responsible for the spatial‐temporal ocean color patterns following individual eddies. Both eddy pumping and the eddy‐Ekman pumping mechanisms alter subsurface nutrient distributions thereby driving biogeochemical cycles, while the eddy advection mechanism to first order stirs existing horizontal gradients in bio‐optical properties. This work illustrates both the promise and some of the limitations of satellite observations for assessing the biogeochemical impacts of mesoscale eddies.
Key Points
Eddies create bio‐optical footprints
Signals are small but can be discerned when 1000's of eddies are analyzed
Many mechanisms are important ‐ not just one
Abstract
Ocean-based carbon dioxide (CO
2
) removal (CDR) strategies are an important part of the portfolio of approaches needed to achieve negative greenhouse gas emissions. Many ocean-based CDR ...strategies rely on injecting CO
2
or organic carbon (that will eventually become CO
2
) into the ocean interior, or enhancing the ocean’s biological pump. These approaches will not result in permanent sequestration, because ocean currents will eventually return the injected CO
2
back to the surface, where it will be brought into equilibrium with the atmosphere. Here, a model of steady state global ocean circulation and mixing is used to assess the time scales over which CO
2
injected in the ocean interior remains sequestered from the atmosphere. There will be a distribution of sequestration times for any single discharge location due to the infinite number of pathways connecting a location at depth with the sea surface. The resulting probability distribution is highly skewed with a long tail of very long transit times, making mean sequestration times much longer than typical time scales. Deeper discharge locations will sequester purposefully injected CO
2
much longer than shallower ones and median sequestration times are typically decades to centuries, and approach 1000 years in the deep North Pacific. Large differences in sequestration times occur both within and between the major ocean basins, with the Pacific and Indian basins generally having longer sequestration times than the Atlantic and Southern Oceans. Assessments made over a 50 year time horizon illustrates that most of the injected carbon will be retained for injection depths greater than 1000 m, with several geographic exceptions such as the Western North Atlantic. Ocean CDR strategies that increase upper ocean ecosystem productivity with the goal of exporting more carbon to depth will have mainly a short-term influence on atmospheric CO
2
levels because ∼70% will be transported back to the surface ocean within 50 years. The results presented here will help plan appropriate ocean CDR strategies that can help limit climate damage caused by fossil fuel CO
2
emissions.
The particle size distribution (PSD) provides important information about pelagic ocean ecosystem structure and function. Knowledge of the PSD and its changes in time can be used to assess the ...contributions made by phytoplankton functional groups to primary production, particle sinking, and carbon sequestration by the ocean. However, few field measurements of the PSD have been made in the pelagic ocean, and little is known about its space‐time variation. Here, a novel bio‐optical algorithm is introduced to retrieve the parameters of a power law particle size spectrum from satellite ocean color observations. First, the particle backscattering coefficient spectrum, bbp(λ), is retrieved from monthly Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) normalized water‐leaving radiance observations following Loisel et al. (2006). Mie modeling is then used to estimate the parameters of a power law PSD (the PSD slope and the particle differential number concentration for a given reference diameter) as a function of the particulate backscattering spectrum. Algorithm uncertainties are greater when bbp(λ) slopes are low, which occurs in high‐productivity areas. Satellite‐based retrievals of PSD parameters are reasonably consistent with available field observations. As an example, the algorithm was applied to monthly SeaWiFS global imagery from August 2007. Global spatial distributions show subtropical oligotrophic gyres characterized by higher PSD slopes and smaller particle number concentrations, as compared with coastal and other high‐productivity areas. Partitioning particle number and volume concentrations into picophytoplankton‐, nanophytoplankton‐, and microphytoplankton‐sized classes indicates that the abundance of picoplankton‐sized particles is roughly constant spatially and that they dominate the particle volume concentrations in oligotrophic regions. On the other hand, abundances of microplankton‐sized particles vary over many orders of magnitude, and they contribute to volume concentration only in the highest‐productivity areas. These results are consistent with current understanding of particle dynamics of pelagic ecosystems and provide new tools for biogeochemical modeling and assessment of the global ocean ecosystem.
Many nearshore fish and invertebrate populations are overexploited even when apparently coherent management structures are in place. One potential cause of mismanagement may be a poor understanding ...and accounting of stochasticity, particularly for stock recruitment. Many of the fishes and invertebrates that comprise nearshore fisheries are relatively sedentary as adults but have an obligate larval pelagic stage that is dispersed by ocean currents. Here, we demonstrate that larval connectivity is inherently an intermittent and heterogeneous process on annual time scales. This stochasticity arises from the advection of pelagic larvae by chaotic coastal circulations. This result departs from typical assumptions where larvae simply diffuse from one site to another or where complex connectivity patterns are created by transport within spatially complicated environments. We derive a statistical model for the expected variability in larval settlement patterns and demonstrate how larval connectivity varies as a function of different biological and physical processes. The stochastic nature of larval connectivity creates an unavoidable uncertainty in the assessment of fish recruitment and the resulting forecasts of sustainable yields.
Metformin, one of most widely prescribed oral hypoglycemic agents, has recently received increased attention because of its potential antitumorigenic effects that are thought to be independent of its ...hypoglycemic effects. Several potential mechanisms have been suggested for the ability of metformin to suppress cancer growth in vitro and vivo: (1) activation of LKB1/AMPK pathway, (2) induction of cell cycle arrest and/or apoptosis, (3) inhibition of protein synthesis, (4) reduction in circulating insulin levels, (5) inhibition of the unfolded protein response (UPR), (6) activation of the immune system, and (7) eradication of cancer stem cells. There is also a growing number of evidence, mostly in the form of retrospective clinical studies that suggest that metformin may be associated with a decreased risk of developing cancer and with a better response to chemotherapy. There are currently several ongoing randomized clinical trials that incorporate metformin as an adjuvant to classic chemotherapy and aim to evaluate its potential benefits in this setting. This review highlights basic aspects of the molecular biology of metformin and summarizes new advances in basic science as well as intriguing results from recent clinical studies.
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