The University of Southampton
University of Southampton Institutional Repository

Shifts in the phytoplankton community in response to zinc and iron enrichments in the north-eastern subarctic Pacific

Shifts in the phytoplankton community in response to zinc and iron enrichments in the north-eastern subarctic Pacific
Shifts in the phytoplankton community in response to zinc and iron enrichments in the north-eastern subarctic Pacific
The offshore Gulf of Alaska—in the north-eastern subarctic Pacific—is a high nitrate, low chlorophyll (HNLC) oceanic region where concentrations of dissolved iron (DFe) and zinc (DZn) are of the order ~0.1 nmol kg-1 in surface waters. At the average winter mixed layer depth of ~120 m, concentrations of DFe and DZn are of the orders ~0.1–0.2 nmol kg-1 and ~1–2 nmol kg-1 respectively. Vertical supply of Fe to surface waters is therefore limited, with phytoplankton blooms driven by episodic inputs of Fe. In contrast, DZn is presumably replenished through seasonal vertical mixing, though maintained at low levels in surface waters, even in winter, implying that removal processes are in operation.

Previous supplementation experiments have demonstrated that phytoplankton biomass (chl-a) and growth, and drawdown of nitrate (NO3-), are stimulated strongly by Fe but only minimally, if at all, by Zn alone. Using on-deck bioassay incubations of surface waters, we confirm that addition of Fe stimulates significant increases in chl-a and large diatoms, and drawdown of NO3-

and silicic acid (Si(OH)4). Associated drawdown of DZn and dissolved cadmium (DCd) indicated Zn stress in control and +Fe treatments. Supplementation with Zn alone had no significant impact on dissolved NO3- and commonly monitored pigments such as chl-a and fucoxanthin. However, in +Zn treatments, DFe and coccolithophore abundance were significantly lower, and the concentration of particulate organic carbon (POC) and the pigments alloxanthin and chlorophyll c1+2 were significantly higher than in control incubations. Our experiment corroborates previously observed relationships between DZn and alloxanthin and chlorophyll c across the subarctic north Pacific and Bering Sea and could help to explain the low or undetectable concentrations of alloxanthin frequently observed in this region. Alloxanthin is a pigment specific to the cryptophytes, either within free-living cells, or within functional plastids retained by mixotrophic protists. Both cryptophytes and mixotrophic ciliates, such as Laboea sp. and Stombidium spp., make a variable but significant contribution to phytoplankton biomass in this area. In the absence of Fe supply to surface waters, Zn could play a hitherto unsuspected role in shaping plankton communities in the HNLC Gulf of Alaska.
2296-7745
Crawford, D.W.
1625e56b-d0c8-4c45-b519-094d0e928a63
Purdie, Duncan
18820b32-185a-467a-8019-01f245191cd8
Lohan, Maeve Carroll
24498297-4906-4238-b69c-f8955961a602
Statham, Peter John
7a626e6f-5c6c-49ad-964d-40df72a1ce63
Peterson, Tawnya D.
b326aaf7-b27a-406e-8e3d-995b5f598b6e
Kennedy, Hilary A.
12104fa7-3c4d-4e1c-9014-2cce8fc3f234
Lipsen, Michael S.
db3d706b-f31f-4c72-8c98-1d6d2b304b86
Putland, Jennifer N.
25c2855d-740f-4d75-abe3-6e9c070f9a5b
Whitney, Frank A.
8e72f36c-0c48-416f-9274-8e965d29b2ba
Crawford, D.W.
1625e56b-d0c8-4c45-b519-094d0e928a63
Purdie, Duncan
18820b32-185a-467a-8019-01f245191cd8
Lohan, Maeve Carroll
24498297-4906-4238-b69c-f8955961a602
Statham, Peter John
7a626e6f-5c6c-49ad-964d-40df72a1ce63
Peterson, Tawnya D.
b326aaf7-b27a-406e-8e3d-995b5f598b6e
Kennedy, Hilary A.
12104fa7-3c4d-4e1c-9014-2cce8fc3f234
Lipsen, Michael S.
db3d706b-f31f-4c72-8c98-1d6d2b304b86
Putland, Jennifer N.
25c2855d-740f-4d75-abe3-6e9c070f9a5b
Whitney, Frank A.
8e72f36c-0c48-416f-9274-8e965d29b2ba

Crawford, D.W., Purdie, Duncan, Lohan, Maeve Carroll, Statham, Peter John, Peterson, Tawnya D., Kennedy, Hilary A., Lipsen, Michael S., Putland, Jennifer N. and Whitney, Frank A. (2022) Shifts in the phytoplankton community in response to zinc and iron enrichments in the north-eastern subarctic Pacific. Frontiers in Marine Science. (doi:10.3389/fmars.2022.93382).

Record type: Article

Abstract

The offshore Gulf of Alaska—in the north-eastern subarctic Pacific—is a high nitrate, low chlorophyll (HNLC) oceanic region where concentrations of dissolved iron (DFe) and zinc (DZn) are of the order ~0.1 nmol kg-1 in surface waters. At the average winter mixed layer depth of ~120 m, concentrations of DFe and DZn are of the orders ~0.1–0.2 nmol kg-1 and ~1–2 nmol kg-1 respectively. Vertical supply of Fe to surface waters is therefore limited, with phytoplankton blooms driven by episodic inputs of Fe. In contrast, DZn is presumably replenished through seasonal vertical mixing, though maintained at low levels in surface waters, even in winter, implying that removal processes are in operation.

Previous supplementation experiments have demonstrated that phytoplankton biomass (chl-a) and growth, and drawdown of nitrate (NO3-), are stimulated strongly by Fe but only minimally, if at all, by Zn alone. Using on-deck bioassay incubations of surface waters, we confirm that addition of Fe stimulates significant increases in chl-a and large diatoms, and drawdown of NO3-

and silicic acid (Si(OH)4). Associated drawdown of DZn and dissolved cadmium (DCd) indicated Zn stress in control and +Fe treatments. Supplementation with Zn alone had no significant impact on dissolved NO3- and commonly monitored pigments such as chl-a and fucoxanthin. However, in +Zn treatments, DFe and coccolithophore abundance were significantly lower, and the concentration of particulate organic carbon (POC) and the pigments alloxanthin and chlorophyll c1+2 were significantly higher than in control incubations. Our experiment corroborates previously observed relationships between DZn and alloxanthin and chlorophyll c across the subarctic north Pacific and Bering Sea and could help to explain the low or undetectable concentrations of alloxanthin frequently observed in this region. Alloxanthin is a pigment specific to the cryptophytes, either within free-living cells, or within functional plastids retained by mixotrophic protists. Both cryptophytes and mixotrophic ciliates, such as Laboea sp. and Stombidium spp., make a variable but significant contribution to phytoplankton biomass in this area. In the absence of Fe supply to surface waters, Zn could play a hitherto unsuspected role in shaping plankton communities in the HNLC Gulf of Alaska.

Other
933823_Manuscript (5) - Accepted Manuscript
Download (19MB)
Text
fmars-09-933823 - Version of Record
Available under License Creative Commons Attribution.
Download (8MB)

More information

In preparation date: 14 April 2022
Submitted date: 1 May 2022
Accepted/In Press date: 12 August 2022
Published date: 21 September 2022

Identifiers

Local EPrints ID: 469827
URI: http://eprints.soton.ac.uk/id/eprint/469827
ISSN: 2296-7745
PURE UUID: b0bbcb89-7c72-47e8-bff4-4b48470cd456
ORCID for Duncan Purdie: ORCID iD orcid.org/0000-0001-6672-1722

Catalogue record

Date deposited: 27 Sep 2022 16:30
Last modified: 28 Sep 2022 01:32

Export record

Altmetrics

Contributors

Author: D.W. Crawford
Author: Duncan Purdie ORCID iD
Author: Maeve Carroll Lohan
Author: Peter John Statham
Author: Tawnya D. Peterson
Author: Hilary A. Kennedy
Author: Michael S. Lipsen
Author: Jennifer N. Putland
Author: Frank A. Whitney

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 http://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.

×