Abstract:Chain formation in diatoms is relevant because of several aspects of their adaptation to the ecosystem. However, the tools to quantify the regulation of their assemblage and infer specific mechanisms in a laboratory setting are scarce. To address this problem, we define an approach based on a statistical physics model of chain growth and separation in combination with experimental evaluation of chain-length distributions. Applying this combined analysis to data from Chaetoceros decipiens and Phaeodactylum tric… Show more
“…Thalassiosira rotula
39 ) and in starvation and responded to it.Figure 5Chain spectra in POST-still cluster (see Fig. 4) and in all the other clusters taken as a single group compared to the null model in which chain separation is stochastically regulated 42 .
…”
Section: Discussionmentioning
confidence: 98%
“…4) and in all the other clusters taken as a single group compared to the null model in which chain separation is stochastically regulated 42 .…”
Section: Discussionmentioning
confidence: 99%
“…By contrast, in turbulence cells produced significantly longer chains, which we interpret as a good physiological state 41 . It has been mathematically demonstrated that C. decipiens exerts an active control on chain length dynamics during growth 42 . Chain length spectrum from exponentially growing C .…”
Current information on the response of phytoplankton to turbulence is linked to cell size and nutrient availability. Diatoms are considered to be favored by mixing as dissolved nutrients are more easily accessible for non-motile cells. We investigated how diatoms exploit microscale turbulence under nutrient repletion and depletion conditions. Here, we show that the chain-forming diatom Chaetoceros decipiens, continues to take up phosphorus and carbon even when silicon is depleted during turbulence. Our findings indicate that upon silica depletion, during turbulence, chain spectra of C. decipiens remained unchanged. We show here that longer chains are maintained during turbulence upon silica depletion whereas under still conditions, shorter chains are enriched. We interpret this as a sign of good physiological state leading to a delay of culture senescence. Our results show that C. decipiens senses and responds to turbulence both in nutrient repletion and depletion. This response is noteworthy due to the small size of the species. The coupling between turbulence and biological response that we depict here may have significant ecological implications. Considering the predicted increase of storms in Northern latitudes this response might modify community structure and succession. Our results partly corroborate Margalef’s mandala and provide additional explanations for that conceptualization.
“…Thalassiosira rotula
39 ) and in starvation and responded to it.Figure 5Chain spectra in POST-still cluster (see Fig. 4) and in all the other clusters taken as a single group compared to the null model in which chain separation is stochastically regulated 42 .
…”
Section: Discussionmentioning
confidence: 98%
“…4) and in all the other clusters taken as a single group compared to the null model in which chain separation is stochastically regulated 42 .…”
Section: Discussionmentioning
confidence: 99%
“…By contrast, in turbulence cells produced significantly longer chains, which we interpret as a good physiological state 41 . It has been mathematically demonstrated that C. decipiens exerts an active control on chain length dynamics during growth 42 . Chain length spectrum from exponentially growing C .…”
Current information on the response of phytoplankton to turbulence is linked to cell size and nutrient availability. Diatoms are considered to be favored by mixing as dissolved nutrients are more easily accessible for non-motile cells. We investigated how diatoms exploit microscale turbulence under nutrient repletion and depletion conditions. Here, we show that the chain-forming diatom Chaetoceros decipiens, continues to take up phosphorus and carbon even when silicon is depleted during turbulence. Our findings indicate that upon silica depletion, during turbulence, chain spectra of C. decipiens remained unchanged. We show here that longer chains are maintained during turbulence upon silica depletion whereas under still conditions, shorter chains are enriched. We interpret this as a sign of good physiological state leading to a delay of culture senescence. Our results show that C. decipiens senses and responds to turbulence both in nutrient repletion and depletion. This response is noteworthy due to the small size of the species. The coupling between turbulence and biological response that we depict here may have significant ecological implications. Considering the predicted increase of storms in Northern latitudes this response might modify community structure and succession. Our results partly corroborate Margalef’s mandala and provide additional explanations for that conceptualization.
“…Cell-to-cell communication is likely occurring in a chain to regulate its length. The transcriptional changes related to this communication would be hard to capture with transcriptomics as i) the portion of the population that responds to turbulence by tuning chain spectrum is small and the transcriptional signal would be diluted in the background noise; ii) cells may communicate also in still condition 29 .…”
Section: Discussionmentioning
confidence: 99%
“…To this aim we applied measured levels of turbulence, in the order of those found in the field 27 , to the diatom Chaetoceros decipiens using a prototypic turbulence generator (TURBOGEN 28 ) and performed both microscopic inspection of chain lengths and transcriptomic analyses. Chain formation is often put in relation to turbulence 13 and C. decipiens displays the peculiar trait of being able to control chain length 29 . Moreover this species belongs to the most abundant diatom genus in ocean waters 30 .…”
Diatoms are a fundamental microalgal phylum that thrives in turbulent environments. Despite several experimental and numerical studies, if and how diatoms may profit from turbulence is still an open question. One of the leading arguments is that turbulence favours nutrient uptake. Morphological features, such as the absence of flagella, the presence of a rigid exoskeleton and the micrometre size would support the possible passive but beneficial role of turbulence on diatoms. We demonstrate that in fact diatoms actively respond to turbulence in non-limiting nutrient conditions. TURBOGEN, a prototypic instrument to generate natural levels of microscale turbulence, was used to expose diatoms to the mechanical stimulus. Differential expression analyses, coupled with microscopy inspections, enabled us to study the morphological and transcriptional response of Chaetoceros decipiens to turbulence. Our target species responds to turbulence by activating energy storage pathways like fatty acid biosynthesis and by modifying its cell chain spectrum. Two other ecologically important species were examined and the occurrence of a morphological response was confirmed. These results challenge the view of phytoplankton as unsophisticated passive organisms.Oceanic plankton are characterised by a huge biodiversity spanning over many phyla. The different life strategies and behaviours displayed by such diverse organisms were selected also to cope with a patchy and variable 3D world driven by water motion 1 . Key factors for their survival, e.g., light availability, nutrient concentrations, prey abundance and water temperature, are all strongly tuned by the fluid motion at different scales. Fluid motion introduces kinetic energy in the system and turbulence is the way kinetic energy is transferred, through a dissipation cascade, over several eddy-like structures down to the smallest scale. Below this scale, energy is dissipated to heat via the friction of viscosity and water motion cannot prevail over molecular diffusion but can control it by changing local gradients 2, 3 . This is particularly important for unicellular phytoplankton which are surrounded by a fluid boundary layer where molecular diffusion is the dominant process and only solute (nutrient) chemical gradients assure cell provisioning. A distortion of the boundary layer would change these gradients, hence nutrients would diffuse more rapidly, enhancing the uptake rate 4 . For non-motile cells, like diatoms, the distortion of the boundary layer can be produced only by sinking or by the shear generated by the decay of turbulent kinetic energy. Therefore there is no more turbulence, as a random motion of water parcels, but the effects of turbulence which dissipates though sheared flow. Shear stress is what cells below Kolmogorov scale would ultimately perceive
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