Armor: Why, When, and How

Hamm, Christian; Smetacek, Victor

doi:10.1016/b978-012370518-1/50015-1

Cited by 60 publications

(35 citation statements)

References 37 publications

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“…On the contrary, dinoflagellates (except for calcifying species; (Van de Waal et al, 2013)) with generally inefficient CO 2 -fixing RuBisCO enzymes (Tortell, 2000) may even profit from chemical changes since photosynthetic carbon fixation as their source of structural elements in the form of cellulose should be facilitated by the ocean acidification-associated CO 2 fertilization Reinfelder, 2011). Under the assumption that any form of shell/exoskeleton protects phytoplankton against predation (as argued by Hamm and Smetacek, 2007), non-calcareous armors may be the preferable solution to realize protection in a future ocean (Fig. 7).…”

Section: Embedding the Physiological Concept In Ecological Theorymentioning

confidence: 99%

A unifying concept of coccolithophore sensitivity to changing carbonate chemistry embedded in an ecological framework

Bach

Riebesell

Gutowska

et al. 2015

Progress in Oceanography

116

133

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a b s t r a c tCoccolithophores are a group of unicellular phytoplankton species whose ability to calcify has a profound influence on biogeochemical element cycling. Calcification rates are controlled by a large variety of biotic and abiotic factors. Among these factors, carbonate chemistry has gained considerable attention during the last years as coccolithophores have been identified to be particularly sensitive to ocean acidification. Despite intense research in this area, a general concept harmonizing the numerous and sometimes (seemingly) contradictory responses of coccolithophores to changing carbonate chemistry is still lacking to date. Here, we present the ''substrate-inhibitor concept'' which describes the dependence of calcification rates on carbonate chemistry speciation. It is based on observations that calcification rate scales positively with bicarbonate (HCO 3 À ), the primary substrate for calcification, and carbon dioxide (CO 2 ), which can limit cell growth, whereas it is inhibited by protons (H + ). This concept was implemented in a model equation, tested against experimental data, and then applied to understand and reconcile the diverging responses of coccolithophorid calcification rates to ocean acidification obtained in culture experiments. Furthermore, we (i) discuss how other important calcification-influencing factors (e.g. temperature and light) could be implemented in our concept and (ii) embed it in Hutchinson's niche theory, thereby providing a framework for how carbonate chemistry-induced changes in calcification rates could be linked with changing coccolithophore abundance in the oceans. Our results suggest that the projected increase of H + in the near future (next couple of thousand years), paralleled by only a minor increase of inorganic carbon substrate, could impede calcification rates if coccolithophores are unable to fully adapt. However, if calcium carbonate (CaCO 3 ) sediment dissolution and terrestrial weathering begin to increase the oceans' HCO 3 À and decrease its H + concentrations in the far future (10-100 kyears), coccolithophores could find themselves in carbonate chemistry conditions which may be more favorable for calcification than they were before the Anthropocene.

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Section: Embedding the Physiological Concept In Ecological Theorymentioning

confidence: 99%

A unifying concept of coccolithophore sensitivity to changing carbonate chemistry embedded in an ecological framework

Bach

Riebesell

Gutowska

et al. 2015

Progress in Oceanography

116

133

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“…Beyond the key biological functions of the cell wall lie important mechanical functions, such as preventing virus penetration, protecting diatoms from the mandibles of predators, or even digestion in some cases. [7][8][9] Applications of materials and technologies inspired from diatoms are widespread and encompass multiple disciplines. Some examples of applications are filters, molecular sieves, resins, insulators, sensors, electronics, optical coatings, environmental indicators of fresh and salt water, and the reduction of red tide's toxicity.…”

Section: Introductionmentioning

confidence: 99%

Hierarchical Silica Nanostructures Inspired by Diatom Algae Yield Superior Deformability, Toughness, and Strength

Garcia

Sen

Buehler

2011

Metall Mater Trans A

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A universal design paradigm in biology is the use of hierarchies, which is evident in the structure of proteins, cells, tissues, and organisms, as well as outside the material realm in the design of signaling networks in complex organs such as the brain. A fascinating example of a biological structure is that of diatoms, a microscopic mineralized algae that is mainly composed of amorphous silica, which features a hierarchical structure that ranges from the nano-to the macroscale. Here, we use the porous structure found at submicron length scales in diatom algae as a basis to study a bioinspired nanoporous material implemented in crystalline silica. We consider the mechanical performance of two nanoscale levels of hierarchy, studying an array of thin-walled foil silica structures and a hierarchical arrangement of foil elements into a porous silica mesh structure. By comparing their elastic, plastic, and failure mechanisms under tensile deformation, we elucidate the impact of hierarchies and the wall width of constituting silica foils on the mechanical properties, by carrying out a series of large-scale molecular dynamics (MD) simulations with the first principles based reactive force field ReaxFF. We find that by controlling the wall width and by increasing the level of hierarchy of the nanostructure from a foil to a mesh, it is possible to significantly enhance the mechanical response of the material, creating a highly deformable, strong, and extremely tough material that can be stretched in excess of 100 pct strain, in stark contrast to the characteristic brittle performance of bulk silica. We find that concurrent mechanisms of shearing and crack arrest lead to an enhanced toughness and are enabled through the hierarchical assembly of foil elements into a mesh structure, which could not be achieved in foil structures alone. Our results demonstrate that including higher levels of hierarchy are beneficial in improving the mechanical properties and deformability of intrinsically brittle materials. The findings reported here provide insight into general material design approaches that may enable us to transform a brittle material such as silicon or silica into a ductile, yet strong and tough material, solely through alterations of its structural arrangement at the nanoscale.

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“…() demonstrated, for instance, that crushing diatom silica shells requires a substantial energy investment on the part of grazers (e.g., through the formation of specialized tools) and suggested that diatom frustules have evolved as mechanical defenses from grazers (Hamm et al. , Hamm and Smetacek ), provided that the predators could reject, after a first “bite,” cells with an especially tough frustule. This argument may be extended to a coevolution of grazers and prey: some grazers, after experiencing (over a time compatible with evolutionary responses) the difficulty of eating diatoms with a strong frustule, may have developed ways of sensing silica; this would prevent the energetic costs associated with capture and subsequent rejection of hard‐to‐break cells.…”

Section: Hypothesesmentioning

confidence: 99%

Different Nutritional Histories Affect the Susceptibility of Algae to Grazing

Venuleo

Giordano

2019

Journal of Phycology

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We hypothesize that algae with different cell compositions are differently perceived by their predators and consequently subjected to selective grazing. Five populations of the diatom Phaeodactylum tricornutum that differed in organic and elemental composition, but were otherwise identical, were generated by acclimation to distinct growth regimes. The different populations were then mixed in pairs and subjected to predation by either the rotifer Brachionus plicatilis or the copepod Acartia tonsa. The presence of rotifers had no impact on the ratio between any two algal populations. The presence of copepods, however, affected the ratio between algae previously acclimated to a medium containing 1 mM NH4+ and algae acclimated to 0.5 mM NO3−, and to either a lower irradiance or a higher CO2 concentration. We discuss the possible reason for the influence of different nutritional histories on the vulnerability of algae to predators. The differential impact of grazers on the growth of algae with different nutritional histories may result from direct selective grazing (i.e., grazers can detect algae with the most palatable cell composition), alone or combined to an asymmetric utilization of the nutrients regenerated after predation by co‐existing algal populations. Our results strongly suggest that the nutritional history of algae can influence the relationships between phytoplankton and grazers and hint at the possibility that algal cell composition is potentially subject to natural selection, because it influences the probability that algae survive predation.

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Armor: Why, When, and How

Cited by 60 publications

References 37 publications

A unifying concept of coccolithophore sensitivity to changing carbonate chemistry embedded in an ecological framework

A unifying concept of coccolithophore sensitivity to changing carbonate chemistry embedded in an ecological framework

Hierarchical Silica Nanostructures Inspired by Diatom Algae Yield Superior Deformability, Toughness, and Strength

Different Nutritional Histories Affect the Susceptibility of Algae to Grazing

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