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Sequential resuspension of protists by accelerating tidal flow: implications for community structure in the benthic boundary layer

Sequential resuspension of protists by accelerating tidal flow: implications for community structure in the benthic boundary layer
Sequential resuspension of protists by accelerating tidal flow: implications for community structure in the benthic boundary layer
We measured resuspension thresholds of protists and bacteria at a subtidal coastal site with in situ flumes and by sampling the benthic boundary layer during tidal accelerations. Heterotrophic nanoflagellates, oligotrich ciliates, the diatom Navicula distans, and bacteria resuspended in weak flow (friction velocity u*crit = 0.25–0.80 cm s-1), likely associated with a surficial fluff layer of sediment. Hypotrich ciliates, scuticociliates, and the diatoms N. transitans and Pleurosigma sp. resuspended in moderate flow (u*crit = 0.82–1.3 cm s-1), followed by pigmented nanoflagellates and diatoms of two Nitzschia spp. in strong flow (u*crit >= 1.5 cm s-1). Hypotrichs and scuticociliates resuspended independent of sediment erosion thresholds, whereas most diatoms resuspended with bulk sediment.
Differing thresholds may be due to cell size, specific gravity, behavior, or association with particles. As tidal currents accelerated to u* = 1.3 cm s-1, resuspension caused cell concentrations at 5 cm above bottom to increase by 2–16 times, varying among taxa. Community structure shifted accordingly, with total oligotrichs, hypotrichs, and scuticociliates changing from 75% to 96% of the ciliate community and the total diatom taxa listed above changing from 37% to 63% of the pennate cells. Sequential resuspension suggests that the species assemblage entering the water column during a resuspension event depends on the maximal bed shear stress, thus varying with the springneap cycle as well as atmospheric forcing and local hydrography. Flow-induced fluctuations of community structure may influence microbial food-web dynamics in the benthic boundary layer and sediment.
bacteria, buzzards bay, nanoflagellates, ciliates, diatoms, community composition, food webs, biology
0024-3590
1152-1164
Shimeta, Jeff
0f7153c7-87cb-4a93-936f-819199ccaf2b
Amos, Carl L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c
Beaulieu, Stace E.
cf86aab3-7eae-43c3-aca0-cfe9ef2ce7c5
Ashiru, Oladipo M.
ade482a0-2993-44d2-a54f-387c9a5bbaa1
Shimeta, Jeff
0f7153c7-87cb-4a93-936f-819199ccaf2b
Amos, Carl L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c
Beaulieu, Stace E.
cf86aab3-7eae-43c3-aca0-cfe9ef2ce7c5
Ashiru, Oladipo M.
ade482a0-2993-44d2-a54f-387c9a5bbaa1

Shimeta, Jeff, Amos, Carl L., Beaulieu, Stace E. and Ashiru, Oladipo M. (2002) Sequential resuspension of protists by accelerating tidal flow: implications for community structure in the benthic boundary layer. Limnology and Oceanography, 47 (4), 1152-1164.

Record type: Article

Abstract

We measured resuspension thresholds of protists and bacteria at a subtidal coastal site with in situ flumes and by sampling the benthic boundary layer during tidal accelerations. Heterotrophic nanoflagellates, oligotrich ciliates, the diatom Navicula distans, and bacteria resuspended in weak flow (friction velocity u*crit = 0.25–0.80 cm s-1), likely associated with a surficial fluff layer of sediment. Hypotrich ciliates, scuticociliates, and the diatoms N. transitans and Pleurosigma sp. resuspended in moderate flow (u*crit = 0.82–1.3 cm s-1), followed by pigmented nanoflagellates and diatoms of two Nitzschia spp. in strong flow (u*crit >= 1.5 cm s-1). Hypotrichs and scuticociliates resuspended independent of sediment erosion thresholds, whereas most diatoms resuspended with bulk sediment.
Differing thresholds may be due to cell size, specific gravity, behavior, or association with particles. As tidal currents accelerated to u* = 1.3 cm s-1, resuspension caused cell concentrations at 5 cm above bottom to increase by 2–16 times, varying among taxa. Community structure shifted accordingly, with total oligotrichs, hypotrichs, and scuticociliates changing from 75% to 96% of the ciliate community and the total diatom taxa listed above changing from 37% to 63% of the pennate cells. Sequential resuspension suggests that the species assemblage entering the water column during a resuspension event depends on the maximal bed shear stress, thus varying with the springneap cycle as well as atmospheric forcing and local hydrography. Flow-induced fluctuations of community structure may influence microbial food-web dynamics in the benthic boundary layer and sediment.

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More information

Published date: 2002
Keywords: bacteria, buzzards bay, nanoflagellates, ciliates, diatoms, community composition, food webs, biology

Identifiers

Local EPrints ID: 6113
URI: http://eprints.soton.ac.uk/id/eprint/6113
ISSN: 0024-3590
PURE UUID: 95ef6c08-0d06-4d0d-a0e4-f3636dd5caaa

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Date deposited: 24 Jun 2004
Last modified: 09 Nov 2021 06:07

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Contributors

Author: Jeff Shimeta
Author: Carl L. Amos
Author: Stace E. Beaulieu
Author: Oladipo M. Ashiru

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