Low-Reynolds-number swimming at pycnoclines
Microorganisms play pivotal functions in the trophic dynamics and biogeochemistry of aquatic ecosystems. Their concentrations and activities often peak at localized hotspots, an important example of which are pycnoclines, where water density increases sharply with depth due to gradients in temperatu...
| Main Authors: | , , |
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| Format: | Article |
| Language: | en_US |
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National Academy of Sciences
2012
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| Online Access: | http://hdl.handle.net/1721.1/74588 https://orcid.org/0000-0002-3199-0508 |
| _version_ | 1826213579082170368 |
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| author | Doostmohammadi, Amin Stocker, Roman Ardekani, Arezoo M. |
| author2 | Massachusetts Institute of Technology. Department of Civil and Environmental Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Civil and Environmental Engineering Doostmohammadi, Amin Stocker, Roman Ardekani, Arezoo M. |
| author_sort | Doostmohammadi, Amin |
| collection | MIT |
| description | Microorganisms play pivotal functions in the trophic dynamics and biogeochemistry of aquatic ecosystems. Their concentrations and activities often peak at localized hotspots, an important example of which are pycnoclines, where water density increases sharply with depth due to gradients in temperature or salinity. At pycnoclines organisms are exposed to different environmental conditions compared to the bulk water column, including reduced turbulence, slow mass transfer, and high particle and predator concentrations. Here we show that, at an even more fundamental level, the density stratification itself can affect microbial ecology at pycnoclines, by quenching the flow signature, increasing the energetic expenditure, and stifling the nutrient uptake of motile organisms. We demonstrate this through numerical simulations of an archetypal low-Reynolds-number swimmer, the “squirmer.” We identify the Richardson number—the ratio of buoyancy forces to viscous forces—as the fundamental parameter that quantifies the effects of stratification. These results demonstrate an unexpected effect of buoyancy on low-Reynolds-number swimming, potentially affecting a broad range of abundant organisms living at pycnoclines in oceans and lakes. |
| first_indexed | 2024-09-23T15:51:29Z |
| format | Article |
| id | mit-1721.1/74588 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T15:51:29Z |
| publishDate | 2012 |
| publisher | National Academy of Sciences |
| record_format | dspace |
| spelling | mit-1721.1/745882022-10-02T04:37:15Z Low-Reynolds-number swimming at pycnoclines Doostmohammadi, Amin Stocker, Roman Ardekani, Arezoo M. Massachusetts Institute of Technology. Department of Civil and Environmental Engineering Stocker, Roman Microorganisms play pivotal functions in the trophic dynamics and biogeochemistry of aquatic ecosystems. Their concentrations and activities often peak at localized hotspots, an important example of which are pycnoclines, where water density increases sharply with depth due to gradients in temperature or salinity. At pycnoclines organisms are exposed to different environmental conditions compared to the bulk water column, including reduced turbulence, slow mass transfer, and high particle and predator concentrations. Here we show that, at an even more fundamental level, the density stratification itself can affect microbial ecology at pycnoclines, by quenching the flow signature, increasing the energetic expenditure, and stifling the nutrient uptake of motile organisms. We demonstrate this through numerical simulations of an archetypal low-Reynolds-number swimmer, the “squirmer.” We identify the Richardson number—the ratio of buoyancy forces to viscous forces—as the fundamental parameter that quantifies the effects of stratification. These results demonstrate an unexpected effect of buoyancy on low-Reynolds-number swimming, potentially affecting a broad range of abundant organisms living at pycnoclines in oceans and lakes. National Science Foundation (U.S.) (Grant CBET-1066545) 2012-11-07T18:56:29Z 2012-11-07T18:56:29Z 2012-02 2011-10 Article http://purl.org/eprint/type/JournalArticle 0027-8424 1091-6490 http://hdl.handle.net/1721.1/74588 Doostmohammadi, A., R. Stocker, and A. M. Ardekani. “Low-Reynolds-number Swimming at Pycnoclines.” Proceedings of the National Academy of Sciences 109.10 (2012): 3856–3861. ©2012 by the National Academy of Sciences https://orcid.org/0000-0002-3199-0508 en_US http://dx.doi.org/10.1073/pnas.1116210109 Proceedings of the National Academy of Sciences Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf National Academy of Sciences PNAS |
| spellingShingle | Doostmohammadi, Amin Stocker, Roman Ardekani, Arezoo M. Low-Reynolds-number swimming at pycnoclines |
| title | Low-Reynolds-number swimming at pycnoclines |
| title_full | Low-Reynolds-number swimming at pycnoclines |
| title_fullStr | Low-Reynolds-number swimming at pycnoclines |
| title_full_unstemmed | Low-Reynolds-number swimming at pycnoclines |
| title_short | Low-Reynolds-number swimming at pycnoclines |
| title_sort | low reynolds number swimming at pycnoclines |
| url | http://hdl.handle.net/1721.1/74588 https://orcid.org/0000-0002-3199-0508 |
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