Characterization of a Southern Ocean deep chlorophyll maximum: response of phytoplankton to light, iron, and manganese enrichment

Southern Ocean phytoplankton growth is limited by low iron (Fe) supply and irradiance, impacting the strength of the biological carbon pump. Unfavourable upper ocean conditions such as low nutrient concentrations can lead to the formation of deep chlorophyll or biomass maxima (DCM/DBM). While common in the Southern Ocean, these features remain under-studied due to their subsurface location. To increase our understanding of their occurrence, we studied the responses of phytoplankton communities from a Southern Ocean DCM to increasing light, Fe, and manganese (Mn) levels. The DCM communities were light- and Fe-limited, but light limitation did not increase phytoplankton Fe requirements. The greatest physiological responses were observed under combined Fe/light additions, which stimulated macronutrient drawdown, biomass production and the growth of large diatoms. Combined Mn/light additions induced subtle changes in Fe uptake rates and community composition, suggesting species-specific Mn requirements. These results provide valuable information on Southern Ocean DCM phytoplankton physiology.

Simple

Identification info

Date (Publication)
2023-10-11T00:00:00
Citation identifier
doi:10.25959/6S84-RM14

Title
Information and documentation - Digital object identifier system
Date (Publication)
2023-10-11
Citation identifier
ISO 26324:2012

Citation identifier
https://doi.org/10.25959/6S84-RM14

Principal investigator

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Latour, Pauline
Private Bag 129
Hobart
TAS
7001
Australia
ORCID ID >

Author

Research School of Earth Sciences (RSES), The Australian National University (ANU) - Eggins, Sam
Building 142, Mills Road, Acton
Canberra
Australian Capital Territory
2601
Australia
ORCID ID >

Author

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - van der Merwe, Pier
Private Bag 129
Hobart
TAS
7001
Australia
ORCID ID >

Author

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Bach, Lennart T.
Private Bag 129
Hobart
TAS
7001
Australia
ORCID ID >

Author

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Boyd, Philip W.
Private Bag 129
Hobart
TAS
7001
Australia
ORCID ID >

Author

Research School of Earth Sciences (RSES), The Australian National University (ANU) - Ellwood, Michael J.
Building 142, Mills Road, Acton
Canberra
Australian Capital Territory
2601
Australia
ORCID ID >

Author

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Bowie, Andrew R.
Private Bag 129
Hobart
TAS
7001
Australia
ORCID ID >

Author

Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC) - Wuttig, Kathrin
20 Castray Esplanade
Hobart
Tasmania
7001
Australia
ORCID ID >

Author

Australian Antarctic Program Partnership (AAPP), Institute for Marine and Antarctic Studies, University of Tasmania, Hobart - Strzepek, Robert F.
Private Bag 129
Hobart
Tasmania
7001
ORCID ID >

Credit
We would like to acknowledge the officers and crew of the RV Investigator (CSIRO Australian Marine National Facility) for the deployment of all the instruments during the SOLACE voyage (IN2020_V08), and the hydro-chemistry team who performed the macronutrient analyses onboard. We acknowledge Terry L. Pinfold for his help with the flow cytometry. This work was funded by the Australian Antarctic Program Partnership (AAPP; ASCI000002) and through the Antarctic Climate & Ecosystems Cooperative Research Centre (ACE CRC).
Credit
We acknowledge the use of the CSIRO Marine National Facility (https://ror.org/01mae9353 ) in undertaking this research.
Status
Completed

Point of contact

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Latour, Pauline
Hobart
TAS
7001
Australia
ORCID ID >

Topic category
  • Biota

Extent

Temporal extent

Time period
2020-12-29 2021-06-15
Maintenance and update frequency
Not planned
Keywords (Theme)
  • deep chlorophyll maximum
  • iron
  • light
  • manganese
  • photophysiology
Global Change Master Directory Earth Science Keywords, Version 8.5
AODN Discovery Parameter Vocabulary
AODN Geographic Extents Vocabulary

Resource constraints

Use limitation
Data, products and services from IMAS are provided "as is" without any warranty as to fitness for a particular purpose.

Resource constraints

Other constraints
This dataset is the intellectual property of the University of Tasmania (UTAS) through the Institute for Marine and Antarctic Studies (IMAS).

Resource constraints

Linkage
https://licensebuttons.net/l/by/4.0/88x31.png

License Graphic

Title
Creative Commons Attribution 4.0 International License
Alternate title
CC-BY
Edition
4.0


>

Website
https://creativecommons.org/licenses/by/4.0/

License Text

Other constraints
Cite data as: Latour, P., Eggins, S., van der Merwe, P., Bach, L., Boyd, P., Ellwood, M., Bowie, A., Wuttig, K., & Strzepek, R. (2023). Characterization of a Southern Ocean deep chlorophyll maximum: response of phytoplankton to light, iron, and manganese enrichment [Data set]. Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS). https://doi.org/10.25959/6S84-RM14
Language
English
Character encoding
UTF8
Supplemental Information
Characterization of a Southern Ocean deep chlorophyll maximum: response of phytoplankton to light, iron, and manganese enrichment

Content Information

Content type
Physical measurement

Identifier

Code
Concentration of nitrate and nitrite {NO3 and NO2} per unit volume of the water body
Identifier
http://vocab.nerc.ac.uk/collection/P06/current/UPOX
Name
Micromoles per litre

Identifier

Code
Concentration of phosphate {PO4} per unit volume of the water body
Identifier
http://vocab.nerc.ac.uk/collection/P06/current/UPOX
Name
Micromoles per litre

Identifier

Code
Concentration of silicate {SiO4} per unit volume of the water body
Identifier
http://vocab.nerc.ac.uk/collection/P06/current/UPOX
Name
Micromoles per litre

Identifier

Code
Photochemical efficiency of Photosystem II
Name
no unit

Identifier

Code
Functional absorption cross-section of Photosystem II
Name
nm2 quanta-1

Identifier

Code
Flow cytometry
Name
no unit

Identifier

Code
Iron uptake rates
Name
Picomoles per liter per day

Identifier

Code
Carbon uptake rates
Name
Micromoles per litre per day

Identifier

Code
Concentration of chlorophyll-a per unit volume of the water body
Identifier
http://vocab.nerc.ac.uk/collection/P06/current/UMMC
Name
Milligrams per cubic metre

Identifier

Code
Particulate organic carbon
Identifier
http://vocab.nerc.ac.uk/collection/P06/current/UPOX
Name
Micromoles per litre

Identifier

Code
Biogenic silica
Identifier
http://vocab.nerc.ac.uk/collection/P06/current/UPOX
Name
Micromoles per litre

Distribution Information

Distribution format
  • Microsoft excel, fcs files

OnLine resource
DATA ACCESS - browse and download available files

OnLine resource
SUPPLEMENTARY - Rmarkdown code and results [PDF]

Resource lineage

Statement
We performed a field bioassay experiment onboard RV Investigator in polar waters of the Southern Ocean (55.47°S, 138.34°E) to study the response of phytoplankton communities from a deep chlorophyll maximum (DCM) to changes in iron (Fe), manganese (Mn) and light conditions. Unfiltered trace metal clean seawater was collected using a trace metal rosette and incubated with Fe and/or Mn additions in deck-board incubators. Neutral-density mesh bags were used to alter the light conditions. Two light treatments were used: a low light treatment (1% incident irradiance) to reproduce the light conditions at the DCM (located at 87m) and a high light treatment (12.4% of incident irradiance) to stimulate shoaling up to 40m. Incubations bottles were sampled at the end of the experiment (day = 10) for multiple parameters: chlorophyll-a/particulate organic carbon/biogenic silica concentrations. Macronutrient concentrations were measured onboard through segmented flow analysis. Photophysiology was studied using a Light-induced Fluorescence Transients Fast Repetition Rate (LIFT-FRR) fluorometer. Flow cytometry samples (for community composition) were fixed at sea and analysed back onshore using an Aurora Cytek flow cytometer (Cytek Biosciences). In addition, carbon and iron uptake rates were measured through radioisotopes additions: after 10 days of incubation, 300 ml of the incubated water was dispensed into smaller bottles and spiked with 14-carbon (NaH14CO3; specific activity 1.85 GBq mmol-1; PerkinElmer, USA) and 55-iron (55FeCl3 in 0.1 M Ultrapure HCl; specific activity 30 MBq mmol-1; PerkinElmer) solutions. The spiked bottles were incubated for 24h under initial conditions before sequential filtration though 20, 2 and 0.2 µm polycarbonate filters. Iron and carbon uptake rates were determined by measuring disintegrations per minute (DPM) on a liquid scintillation counter (PerkinElmer Tri-Carb 2910 TR) after incubation of the filters in Ultima Gold liquid scintillation cocktail at least 24h prior to analysis (PerkinElmer). To study the effect of metal additions and light on the tested response variables, linear mixed effect models were performed using R. Models were fit with the ‘lme’ function of the ‘lme4’ package, using maximum likelihood. The variability between replicates (or bottle effect) was included as a random effect in all analyses. Using the ‘drop1’ function with a Chi-squared test (null hypothesis of independence), the best model fit was selected by sequentially eliminating variables among the fixed effects: Mn, Fe, light and in some cases size class (Fe/carbon uptake) or gated population (flow cytometry). To normalize model residuals, data were log10 transformed before analyses. Iron and Mn addition treatments were treated as two separate factors, each possessing two levels (‘True’ for addition or ‘False’ for no addition). When treatment effects were suggested by the model fit (with more than two factor levels), we performed pairwise comparisons using the ‘emmeans’ package with the Tukey method.
Hierarchy level
Dataset
Hierarchy level
Dataset

Metadata

Metadata identifier
urn:uuid/93561671-c14f-4207-92e1-3b24d419855b

Language
English
Character encoding
UTF8

Distributor

IMAS Data Manager - Data Officer
Institute for Marine and Antarctic Studies
Private Bag 129
Hobart
Tasmania
7001
Australia

Type of resource

Resource scope
Dataset
Name
IMAS Dataset level record
Metadata linkage
https://metadata.imas.utas.edu.au/geonetwork/srv/eng/catalog.search#/metadata/93561671-c14f-4207-92e1-3b24d419855b

Point of truth URL of this metadata record

Date info (Creation)
2023-10-09T00:00:00
Date info (Revision)
2023-11-13T10:47:46

Metadata standard

Title
ISO 19115-3:2018
 
 

Overviews

Spatial extent

Keywords

deep chlorophyll maximum iron light manganese photophysiology
AODN Discovery Parameter Vocabulary
Biogenic silica Carbon uptake rates Concentration of chlorophyll-a per unit volume of the water body Concentration of nitrate and nitrite {NO3 and NO2} per unit volume of the water body Concentration of phosphate {PO4} per unit volume of the water body Concentration of silicate {SiO4} per unit volume of the water body Flow cytometry Functional absorption cross-section of Photosystem II Iron uptake rates Particulate organic carbon Photochemical efficiency of Photosystem II
Global Change Master Directory Earth Science Keywords, Version 8.5
EARTH SCIENCE | BIOSPHERE | ECOLOGICAL DYNAMICS | ECOSYSTEM FUNCTIONS | BIOGEOCHEMICAL CYCLES EARTH SCIENCE | BIOSPHERE | ECOSYSTEMS | AQUATIC ECOSYSTEMS | PLANKTON | PHYTOPLANKTON

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