Influence of plankton community structure on the sinking velocity of marine aggregates.

Bach, Lennart T. , Boxhammer, Tim , Larsen, A., Hildebrandt, N., Schulz, Kai G. and Riebesell, Ulf (2016) Influence of plankton community structure on the sinking velocity of marine aggregates. Open Access Global Biogeochemical Cycles, 30 (8). pp. 1145-1165. DOI 10.1002/2016GB005372.

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Abstract

About 50 Gt of carbon is fixed photosynthetically by surface ocean phytoplankton communities every year. Part of this organic matter is reprocessed within the plankton community to form aggregates which eventually sink and export carbon into the deep ocean. The fraction of organic matter leaving the surface ocean is partly dependent on aggregate sinking velocity which accelerates with increasing aggregate size and density, where the latter is controlled by ballast load and aggregate porosity. In May 2011, we moored nine 25 m deep mesocosms in a Norwegian fjord to assess on a daily basis how plankton community structure affects material properties and sinking velocities of aggregates (Ø 80–400 µm) collected in the mesocosms' sediment traps. We noted that sinking velocity was not necessarily accelerated by opal ballast during diatom blooms, which could be due to relatively high porosity of these rather fresh aggregates. Furthermore, estimated aggregate porosity (Pestimated) decreased as the picoautotroph (0.2–2 µm) fraction of the phytoplankton biomass increased. Thus, picoautotroph-dominated communities may be indicative for food webs promoting a high degree of aggregate repackaging with potential for accelerated sinking. Blooms of the coccolithophore Emiliania huxleyi revealed that cell concentrations of ~1500 cells/mL accelerate sinking by about 35–40%, which we estimate (by one-dimensional modeling) to elevate organic matter transfer efficiency through the mesopelagic from 14 to 24%. Our results indicate that sinking velocities are influenced by the complex interplay between the availability of ballast minerals and aggregate packaging; both of which are controlled by plankton community structure.

Document Type: Article
Keywords: sinking velocity; plankton community structure; aggregates; ballast; porosity; biological pump
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
AWI
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/2016GB005372
ISSN: 0886-6236
Projects: SOPRAN, BIOACID, MicroPolar, MINOS
Expeditions/Models/Experiments:
Date Deposited: 30 Aug 2016 09:22
Last Modified: 23 Sep 2019 18:16
URI: http://oceanrep.geomar.de/id/eprint/33663

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