The University of Southampton
University of Southampton Institutional Repository

Phytoplankton Stimulation in Frontal Regions of Benguela Upwelling Filaments by Internal Factors

Phytoplankton Stimulation in Frontal Regions of Benguela Upwelling Filaments by Internal Factors
Phytoplankton Stimulation in Frontal Regions of Benguela Upwelling Filaments by Internal Factors
Filaments are intrusions of upwelling water into the sea, separated from the surrounding water by fronts. Current knowledge explains the enhanced primary production and phytoplankton growth found in frontal areas by external factors like nutrient input. The question is whether this enhancement is also caused by intrinsic factors, i.e., simple mixing without external forcing. In order to study the direct effect of frontal mixing on organisms, disturbing external influx has to be excluded. Therefore, mixing was simulated by joining waters originating from “inside” and “outside” the filament in mesocosms (“tanks”). These experiments were conducted during two cruises in the northern Benguela upwelling system in September 2013 and January 2014. The mixed waters reached a much higher net primary production and chlorophyll a (chla) concentration than the original waters already 2–3 days after their merging. The peak in phytoplankton biomass stays longer than the chla peak. After their maxima, primary production rates decreased quickly due to depletion of the nutrients. The increase in colored dissolved organic matter (CDOM) may indicate excretion and degradation. Zooplankton is not quickly reacting on the changed conditions. We conclude that already simple mixing of two water bodies, which occurs generally at fronts between upwelled and ambient water, leads to a short-term stimulation of the phytoplankton growth. However, after the exhaustion of the nutrient stock, external nutrient supply is necessary to maintain the enhanced phytoplankton growth in the frontal area. Based on these data, some generally important ecological factors are discussed as for example nutrient ratios and limitations, silicate requirements and growth rates.
210
Wasmund, Norbert
2fa63b2c-dabf-4af9-88f8-67833afecc5d
Siegel, Herbert
aebab9bc-6b24-4771-aea2-6bd6fedc35bb
Bohata, Karolina
39885c8e-d3b8-4b45-b63f-45b17bab1b66
Flohr, Anita
1e293a22-bdba-408e-9608-fed8b65e4e79
Hansen, Anja
d8c02750-37ad-49e2-8ccc-b3b3b6cc786d
Mohrholz, Volker
25a7de89-0f75-499b-b1d1-a9834ba2b7a7
Wasmund, Norbert
2fa63b2c-dabf-4af9-88f8-67833afecc5d
Siegel, Herbert
aebab9bc-6b24-4771-aea2-6bd6fedc35bb
Bohata, Karolina
39885c8e-d3b8-4b45-b63f-45b17bab1b66
Flohr, Anita
1e293a22-bdba-408e-9608-fed8b65e4e79
Hansen, Anja
d8c02750-37ad-49e2-8ccc-b3b3b6cc786d
Mohrholz, Volker
25a7de89-0f75-499b-b1d1-a9834ba2b7a7

Wasmund, Norbert, Siegel, Herbert, Bohata, Karolina, Flohr, Anita, Hansen, Anja and Mohrholz, Volker (2016) Phytoplankton Stimulation in Frontal Regions of Benguela Upwelling Filaments by Internal Factors. Frontiers in Marine Science, 3, 210. (doi:10.3389/fmars.2016.00210).

Record type: Article

Abstract

Filaments are intrusions of upwelling water into the sea, separated from the surrounding water by fronts. Current knowledge explains the enhanced primary production and phytoplankton growth found in frontal areas by external factors like nutrient input. The question is whether this enhancement is also caused by intrinsic factors, i.e., simple mixing without external forcing. In order to study the direct effect of frontal mixing on organisms, disturbing external influx has to be excluded. Therefore, mixing was simulated by joining waters originating from “inside” and “outside” the filament in mesocosms (“tanks”). These experiments were conducted during two cruises in the northern Benguela upwelling system in September 2013 and January 2014. The mixed waters reached a much higher net primary production and chlorophyll a (chla) concentration than the original waters already 2–3 days after their merging. The peak in phytoplankton biomass stays longer than the chla peak. After their maxima, primary production rates decreased quickly due to depletion of the nutrients. The increase in colored dissolved organic matter (CDOM) may indicate excretion and degradation. Zooplankton is not quickly reacting on the changed conditions. We conclude that already simple mixing of two water bodies, which occurs generally at fronts between upwelled and ambient water, leads to a short-term stimulation of the phytoplankton growth. However, after the exhaustion of the nutrient stock, external nutrient supply is necessary to maintain the enhanced phytoplankton growth in the frontal area. Based on these data, some generally important ecological factors are discussed as for example nutrient ratios and limitations, silicate requirements and growth rates.

Text
Wasmund_2016_final.pdf - Other
Available under License Creative Commons Attribution.
Download (3MB)

More information

e-pub ahead of print date: 3 November 2016
Published date: 3 November 2016
Organisations: Geochemistry

Identifiers

Local EPrints ID: 402391
URI: https://eprints.soton.ac.uk/id/eprint/402391
PURE UUID: 4d1d0b1e-5ed8-4ee7-9e49-d075a74720f2
ORCID for Anita Flohr: ORCID iD orcid.org/0000-0002-5018-5379

Catalogue record

Date deposited: 07 Nov 2016 09:40
Last modified: 31 Jul 2019 00:33

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.

×