The University of Southampton
University of Southampton Institutional Repository

The 'Fall dump' - a new perspective on the role of a 'shade flora' in the annual cycle of diatom production and export flux

The 'Fall dump' - a new perspective on the role of a 'shade flora' in the annual cycle of diatom production and export flux
The 'Fall dump' - a new perspective on the role of a 'shade flora' in the annual cycle of diatom production and export flux
Investigations of diatom fluxes recorded in laminated sediments using scanning electron microscope techniques together with evidence from sediment trap studies have contributed to a reappraisal of the annual cycle of diatom production and export flux. We propose that where there is a strong seasonal thermocline and nutricline, a number of diatoms, hitherto regarded as typical sparse summer flora, characteristic of oligotrophic waters, are able to generate substantial production at depth. These species, including Rhizosolenia spp., Stephanopyxis palmeriana, Thalassiothrix spp. and some Coscinodiscus spp., may represent a "shade flora" that have adapted to grow in low-light conditions and/or to regulate their buoyancy to move between a deep nutrient source and the euphotic zone. Although rates of growth and primary production are substantially lower than species characteristic of "spring bloom" or "upwelling" conditions, the total primary production integrated over the (several-month) period of summer stratification may be as significant as the "spring bloom" or greater. The term fall or autumn bloom (as a counterpart of the "spring bloom") is therefore a misnomer. Whereas the "spring bloom" involves a rapid burst of reproduction and sedimentation, the "fall dump" is the sedimentation of a long-lived episode of production (lasting the duration of the seasonal thermocline) and triggered by the fall/winter mixing that breaks down stratification. The "fall dump" may produce as much, or in some cases more, export production than the "spring bloom". The results of this study suggest that a reorientation of thinking on diatom ecology and palaeoecology may be required.
DIATOMS, PARTICULATE FLUX, SEDIMENTS, CALIFORNIA GULF, MEDITERRANEAN
0967-0645
2129-2154
Kemp, A.E.S.
131b479e-c2c4-47ae-abe1-ad968490960e
Pike, J.
a752c052-98ae-4c4c-967d-051bc9586219
Pearce, R.B.
7d772b25-3ad0-4909-9a96-3a1a8111bc2f
Lange, C.B.
6d5507ae-1d21-416a-a191-cc175003585e
Kemp, A.E.S.
131b479e-c2c4-47ae-abe1-ad968490960e
Pike, J.
a752c052-98ae-4c4c-967d-051bc9586219
Pearce, R.B.
7d772b25-3ad0-4909-9a96-3a1a8111bc2f
Lange, C.B.
6d5507ae-1d21-416a-a191-cc175003585e

Kemp, A.E.S., Pike, J., Pearce, R.B. and Lange, C.B. (2000) The 'Fall dump' - a new perspective on the role of a 'shade flora' in the annual cycle of diatom production and export flux. Deep Sea Research Part II: Topical Studies in Oceanography, 47 (9-11), 2129-2154. (doi:10.1016/S0967-0645(00)00019-9).

Record type: Article

Abstract

Investigations of diatom fluxes recorded in laminated sediments using scanning electron microscope techniques together with evidence from sediment trap studies have contributed to a reappraisal of the annual cycle of diatom production and export flux. We propose that where there is a strong seasonal thermocline and nutricline, a number of diatoms, hitherto regarded as typical sparse summer flora, characteristic of oligotrophic waters, are able to generate substantial production at depth. These species, including Rhizosolenia spp., Stephanopyxis palmeriana, Thalassiothrix spp. and some Coscinodiscus spp., may represent a "shade flora" that have adapted to grow in low-light conditions and/or to regulate their buoyancy to move between a deep nutrient source and the euphotic zone. Although rates of growth and primary production are substantially lower than species characteristic of "spring bloom" or "upwelling" conditions, the total primary production integrated over the (several-month) period of summer stratification may be as significant as the "spring bloom" or greater. The term fall or autumn bloom (as a counterpart of the "spring bloom") is therefore a misnomer. Whereas the "spring bloom" involves a rapid burst of reproduction and sedimentation, the "fall dump" is the sedimentation of a long-lived episode of production (lasting the duration of the seasonal thermocline) and triggered by the fall/winter mixing that breaks down stratification. The "fall dump" may produce as much, or in some cases more, export production than the "spring bloom". The results of this study suggest that a reorientation of thinking on diatom ecology and palaeoecology may be required.

Full text not available from this repository.

More information

Published date: 2000
Keywords: DIATOMS, PARTICULATE FLUX, SEDIMENTS, CALIFORNIA GULF, MEDITERRANEAN

Identifiers

Local EPrints ID: 8718
URI: https://eprints.soton.ac.uk/id/eprint/8718
ISSN: 0967-0645
PURE UUID: f33d7dfe-d7fd-4720-bd1e-18fec569d0b6

Catalogue record

Date deposited: 25 Aug 2004
Last modified: 17 Jul 2017 17:12

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×