# Pan-Atlantic connectivity of marine biogeochemical and ecological processes and the impact of anthropogenic pressures

Birgit Quack, D. Arevalo, H. W. Bange, K. Becker, W. Böhme, D. Booge, A.

Engel, H. Hepach, R. Ingeniero, J. Karnatz, et al.

► To cite this version:

Birgit Quack, D. Arevalo, H. W. Bange, K. Becker, W. Böhme, et al., Pan-Atlantic connectivity of marine biogeochemical and ecological processes and the impact of anthropogenic pressures. Status Conference Research Vessels 2024, Mar 2024, Bremen (DE), Germany. pp.473-482. hal-04490989

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Submitted on 12 Mar 2024

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STATUS CONFERENCE
RESEARCH VESSELS 2024

Conference transcript

SCHRIFTENREIHE PROJEKTTRÄGER JÜLICH
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Schriftenreihe Projektträger Jülich Volume 18

ISBN 973-3-95806-747-9

The contributions are abstracts of the results of past research cruises. These results were presented at the Status Conference Research Vessels 2024 at MARUM, the Center for Marine Environmental Sciences at the University of Bremen.

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# STATUS CONFERENCE RESEARCH VESSELS 2024

## Conference transcript

SCHRIFTENREIHE PROJEKTTRÄGER JÜLICH
AUTHORS

GEOMAR Helmholtz Centre for Ocean Research Kiel | Kiel, Germany

B. Quack, D. Arevalo, H. Bange, K. Becker, W. Böhme, D. Booge, A. Engel, H. He-
pach, R. Ingeniero, J. Karnatz, C. Marandino, T. Müller, B. Pontiller, L. Scheidemann

Hereon | Geesthacht, Germany

M. Hieronymi, R. Röttgers, G. Schulz

IUP – Institut für Umweltphysik | Bremen, Germany

T. Bösch, M. Latsch, F. Wittrock

ARDITI – Agência Regional para o Desenvolvimento da Investigação, Tecnologia e
Inovação | Funchal, Portugal

R. Caldeira, C. Cardoso, J. Reis, A. Rosa

CRODT – Centre de Recherche Océanographique de Dakar Thiaroye | Dakar, Senegal

N. Diogoul

IRD - Institut de Recherche pour le Développement | Dakar, Senegal

P. Brehmer

RSMAS – Rosenstiel School of Marine and Atmospheric Science | Miami, Florida, USA

E. Atlas

SDU – University of Southern Denmark | Odense, Denmark

C. Löscher, P. Xu

CNRS – Centre national de la recherche scientifique, Station Biologique de Roscoff |
Roscoff, France

P. Potin

UiO – University of Oslo | Oslo, Norway

S. Auganaes, K. Krüger
University of Leicester | Leicester, United Kingdom

S. Ball, A. Offin, J. Pickering

University of York | York, United Kingdom

Y. Assiri, L. Brown, L. J. Carpenter, R. Chance, M. Jones, D. Loades, K. Weddell

## SO287-CONNECT FROM LAS PALMAS TO GUAYAQUIL IN WINTER 2021/2022

The transit of R/V SONNE from Las Palmas (11.12.2021) to Guayaquil, Ecuador (11.01.2022) was directly related to the international collaborative project SO287-CONNECT of GEOMAR in cooperation with Hereon and the University of Bremen, supported by the German Federal Ministry of Education and Research (BMBF) between October 2021 and January 2024. The research expedition was conducted to decipher the coupling of biogeochemical and ecological processes and their influence on atmospheric chemistry. A comprehensive work program combined continuous underway water and atmospheric sampling and measurements, incubations, as well as 36 stations from the upwelling zones off Africa into the Sargasso Sea and further to the Caribbean and the equatorial Pacific.

<figure><img src="image_4.png" /><figcaption>Figure 1: Track chart of R/V SONNE cruise SO287-CONNECT with stations (upper left). Salinity (upper right) and oxygen (lower right), with encountered water masses along the route in the top 1100 m of the Atlantic as North Atlantic Subtropical Mode water (NASTMW), subtropical Underwater (SUW), western and eastern North and South Atlantic Central Waters (W/ENACW/ESACW), Antarctic intermediate water (AAIW), dichloromethane (pM) in the upper water column (lower left).</figcaption></figure>

## WATER MASS ANALYSIS ALONG THE NORTH EQUATORIAL CURRENT

With the Extended Multi-parameter analysis (OMP) from Karstensen & Tomczak (1998) with source water types (SWT) based on Liu & Tanhua (2021), eight upper and lower
central water masses, Antarctic Intermediate and Mediterranean Water, as well as North Atlantic Deep Waters, Antarctic Bottom and Northeast Atlantic Bottom Water were analysed in the Atlantic transect. Based on a literature search, it was possible to additionally identify North Atlantic Subtropical Mode water and subtropical Underwater (Goes et al., 2005) in the upper depth ranges. An interesting feature in the OMP analysis is related to the higher proportions of SACW at station 6, which is related to a cyclonic low-oxygen eddy (Figure 1). The water masses sampled at this station were significantly different from the other stations, which underlines the efficiency of eddies formed in the Mauritian upwelling region in transporting tracers from the coast to the open ocean.

The biogeochemical and ecological processes along the cruise track need to be interpreted on the background of this water mass analysis, e. g. for marine and atmospheric halocarbons during the cruise.

## HALOCARBON DYNAMICS

The spatial variations of natural and anthropogenic short-lived bromo-, chloro- and iodocarbons, e. g. bromoform (CHBr<sub>3</sub>), methyl iodide (CH<sub>3</sub>I), di- and trichloromethane (CH<sub>2</sub>Cl<sub>2</sub> CHCl<sub>3</sub>) were highly dynamic in both the ocean and atmosphere. Production of brominated and, surprisingly, chlorinated methanes occurred in the deep chlorophyll maximum (Figure 1), while the chemistry of iodinated compounds was closely related to light. The cycling of anthropogenic chlorinated compounds was coupled to water mass formation and transport. First time incubation experiments of halocarbon release from the floating seaweed species *Sargassum* spp. suggest, that during its extensive blooms in the Atlantic, this brown seaweed plays an important role in the emissions of natural halogens and organic matter.

## MARINE CARBON AND NITROGEN CYCLING

Marine carbon cycling was tightly coupled to differences in microbial diversity, activity, and abundance from the Canary current upwelling system into the subtropical gyre. Phosphorus availability was an important driver of shifts in the bacterial community composition along the transect affecting the semi-labile DOM pool, supported by pronounced changes in the relative proportion of transcribed genes associated with the utilization of phosphorus and transcription of carbohydrate-active enzymes.

The vertical distribution of gel particles was investigated along the cruise track from the surface to the deep sea. Significant distinctions were found in terms of particle abundances and sizes between the productive upwelling system at the northwest coast of Africa compared to the open ocean regime in the western north Atlantic.

Ambient atmospheric concentrations of nitrogen dioxide (NO<sub>2</sub>, manmade pollutant) were highly variable, but were typically below 0.1 parts per billion (ppbv) in air from "clean sector" wind directions unperturbed by the ship's own emissions. Even at night, no molecular iodine (I<sub>2</sub>, natural emissions) above the instrument's detection limit (~1 pptv)
was observed, except for a small iodine signal (~2 pptv) in the equatorial Pacific. Time series measurements of the solar flux, photosynthetically active radiation (PAR), and the photolysis rate coefficients for 16 photolabile atmospheric gases will be used for the interpretation of halocarbon cycling above the subtropical North Atlantic.

As the cruise went through the Equatorial Tropical Pacific (ETP), we took the opportunity to revisit a section at 85.5°W, which covers the ETP oxygen minimum zone (OMZ) that has been sampled and investigated on prior cruises. All ocean surface waters were above or close to equilibrium with respect to the corresponding atmospheric values of nitrous oxide (N₂O) and methane (CH₄). Enhanced N₂O saturations were observed in the vicinity of the Canary current upwelling system and above the OMZ in the ETP. Enhanced CH₄ saturations were also observed in coastal waters of the ETP. N₂O concentrations within the hypoxic zone were twice as high as those in the rest of the water column during SO287. Comparison of depth-integrated concentrations of dissolved N₂O with previous cruises reveals comparatively high values during La Niña years, maximizing during SO287.

SO287 connect was the first study to measure surface dissolved nitric oxide (NO) concentration across the Atlantic Ocean. Dissolved NO concentrations ranged from 9.38 to 48.24 pM (average: 13.89 ± 5.82 pM). Notably higher concentrations were observed in the eastern Tropical North Atlantic Ocean, southeast of the Azores Archipelago, and northwest of the Canary Islands. The sea-to-air-flux ranged from 1.12x10⁻¹⁸ to 4.78x10⁻¹⁷ mol m⁻² s⁻¹ (average: 1.50 ± 0.99x10⁻¹⁷ mol m⁻² s⁻¹), indicating that the open ocean was a notable source of NO to the atmosphere during this campaign.

A metagenomic approach was utilized across a dissolved oxygen (DO) gradient from oxic to suboxic conditions in the ETP. The findings were compared to the Tara Ocean datasets obtained from the same region under a comparable La Niña event in 2011. SO287 observed a decrease in microbial diversity and abundance, coupled with an increase in most nitrogen metabolisms as DO decreased. Dominant microbial groups and key functions displayed varying sensitivities to different DO ranges (5 to >120 µmol/kg). The shift in functional groups occurred when DO dropped below 120, 90, 80, 60, or 12 µmol/kg. A significant reduction in the relative abundance of SAR11, along with an increase in nitrogen metabolisms, e. g., denitrification (N₂O production) and nitrogen fixation, were observed in our datasets comparing to Tara Ocean datasets. The study improves our understanding of the response of microbial diversity, groups, and functions to a future OMZ expansion and how ENSO events impact in-situ microbial community and their roles.

## INFLUENCE OF SHIP EMISSIONS ON DMS

Dimethyl sulfide (DMS) biogenically produced in the ocean is an important precursor of cloud condensation nuclei in the remote marine boundary layer and therefore influences the radiation budget of the Earth. The goal during SO287 was to investigate, how ship
emissions (i. e. use of scrubbers) impact the trace gas biogeochemistry in the surface
ocean. Incubation experiments revealed a significant difference of DMS concentrations
between the scrubber treatment and the controls. DMS concentrations in the scrubber
treated water are drastically reduced at the start of the experiment indicating an
immediate effect (possibly pH related) of scrubber water addition on the actual DMS
concentration. Initial DMSO concentrations in the scrubber treated water were
significantly higher than in the control during the experiment with a 2% scrubber addition
indicating a pH induced oxidation to DMSO. The overall decrease of the climate relevant
trace gas DMS through addition of scrubber effluent could facilitate climate change.

TRANS-ATLANTIC MICRO-PLASTIC

95% of plastic particles along the transect were either polyethylene (PE) or polypropylene, with PE clearly dominating. Furthermore, the distribution of the plastic particles along the transect was defined by a few stations with high concentrations, such as the one in the North Atlantic garbage patch located in the North Atlantic gyre.

UPTAKE OF OZONE TO THE OCEAN

Atmospheric ozone levels and uptake of ozone to the ocean alongside biogeochemical
properties of the seawater (including iodine speciation, fatty acid composition, DOC
concentrations and surface tension) were measured in order to investigate the mechanisms
of ozone uptake. Measured ambient ozone mixing ratios 10 m above sea level were
between ~ 5 - 40 ppb. The highest concentrations were observed in the Atlantic (35.0
± 2.6 ppb), followed by the Caribbean (17.7±2.1 ppb) and ETP (6.5 ± 1.4 ppb).
Ozone uptake to seawater was measured for samples from the CTD, underway system
and from the sea-surface microlayer (SML). The SML was the most reactive towards
ozone, with chemical reactivity to ozone on average 17% higher than in the underlying
water. Iodine speciation (iodide, iodate, dissolved organic iodine, total inorganic iodine
and total dissolved iodine) was measured for all samples, with the reduced form, iodide,
representing the most ozone-reactive fraction. Mean (±sd) iodide concentrations in the
CTD, SML and underway samples were 140±24, 59±11 and 139±29 nM, respectively,
revealing a significant depletion of iodide in the SML compared to the near-surface CTD
sample. Mean total dissolved iodine concentrations were 438±20, 401±15 and
397±15 nM for CTD, SML and underway samples. The SML samples were enriched in
DOC relative to the CTD samples (EF=1.4) and their concentration range was far greater
(0.68–8.9 mgL⁻¹ vs 1.4–2.6 mgL⁻¹). SML surface tensions were depressed relative to the
CTD seawater (72.1±1.6 vs 73.5±0.2) indicating enhanced surfactant concentrations in
the SML. The DOC and surface tension measurements show that there is increased
organic material concentration within the SML. This dataset will help improve our
understanding of the mechanism and rates of ozone uptake to the ocean.

PLANKTON DIEL MIGRATION

Sea temperature and dissolved oxygen were identified as primary drivers of SSLs
distribution, highlighting their significance in oceanic ecosystems and global climate
regulation. The planktonic sound scattering layer (SSLs) revealed strong regional variations in the Atlantic and Pacific and responses to environmental factors in the North Atlantic Gyre. Sea temperature and DO were identified as primary drivers of SSL distribution, highlighting their significance in oceanic ecosystems and global climate regulation. The Pacific's shallow SSLs were linked to the OMZ.

## REFERENCES

Karstensen J, Tomczak M, Age determination of mixed water masses using CFC and oxygen data. Journal of Geophysical Research: Oceans 1998, 103(C9), 18599-18609.
https://doi.org/10.1029/98JC00889.

Liu M, Tanhua T, Water masses in the Atlantic Ocean: Characteristics and distributions. Ocean Science 2021, 17(2), 463-486. https://doi.org/10.5194/os-17-463-2021.

Goes M, Molinari R, da Silveira I, Wainer I, Retroflections of the north brazil current during February 2002, Deep-Sea Res. Pt. I 2005, 52, 647-667,
https://doi.org/10.1016/j.dsr.2004.10.010.

## SCIENTIFIC OUTPUT

### LIST OF PUBLICATIONS

Auganæs, S, Ozone above the tropical Atlantic ocean, 19. June 2023 at the University of Oslo.

Bi S, Hieronymi M, Röttgers R, Bio-geo-optical modelling of natural waters, Front. Mar. Sci. 2023, 10, 1196352. doi: 10.3389/fmars.2023.1196352.

Böhme W, On the relationships between dissolved organic matter, inorganic nutrients, and the bacterial community composition in the tropical North Atlantic Ocean",
Masterthesis, 06. April 2023 at the Christian-Albrechts-Universität zu Kiel (CAU Kiel).

Karnatz J, Sargassum seaweed in the North Atlantic and its potential contributions to the emissions of halocarbons and DOC", Masterthesis 02. December 2022 at the Christian-Albrechts-Universität zu Kiel (CAU Kiel).

Keß K, Interaction of dimethyl sulphide (DMS) and hypobromous acid (HOBr) in global ocean surface waters, Masterthesis 20. August 2023 at the Christian-Albrechts-Universität zu Kiel (CAU Kiel).
Müller T, Abundance and size distribution of Transparent Exopolymer Particles (TEP) and Coomassie Stainable Particles (CSP) in the North Atlantic Ocean, Masterthesis 29. März 2023 at the Christian-Albrechts-Universität zu Kiel (CAU Kiel).

Offin A J M B, Iodine volatilisation from the ocean, PhD thesis (submitted) 2023, School of Chemistry, University of Leicester (United Kingdom).

Pohlmann M, Nitrous oxide measurements in the western tropical South Pacific, Bachelor thesis, Christian-Albrechts-Universität zu Kiel, 2023, Kiel, Germany, 41 pp.

Xu, P, Microbial Ecology under Ocean Deoxygenation: Diversity, Metabolisms, Environmental Controls, Ph.D. thesis, SDU, 2023, Syddansk Universitet. Det Naturvidenskabelige Fakultet. https://doi.org/10.21996/nag8-j503.

Baker et al., Iodine speciation in aerosols over the tropical Atlantic and Pacific Oceans, (working title, ongoing analysis).

Baker et al., Trace metal fractional solubility in aerosols collected over the tropical southeast Pacific Ocean, (working title, ongoing analysis).

Becker K W, Engel A.; Variations of the surface ocean microbial lipidome across a biogeochemical continuum from the productive Canary upwelling system to the oligotrophic Sargasso Sea, (working title, ongoing analysis).

Becker K W, Pontiller B, Engel A; Effects of nutrient availability on lipid biosynthesis in marine prokaryotes based on combined metatranscriptomic and lipidomic analysis, (working title, ongoing analysis).

Brown L, Chemical Controls on the Uptake of Ozone to the Ocean, PhD thesis, University of York, to be submitted 2024.

Devresse et al., Size-fractioned plankton respiration and bacterial growth efficiency in the subtropical north Atlantic ocean, (working title, ongoing analysis).

Diogoul et al., Pelagic Sound Scattering Layer distribution and diel vertical migration behavior across the North Est Atlantic & Eastern Tropical Pacific Ocean.

Hepach et al., Tracing organic matter degradation along an East-to-West gradient in the subtropical Atlantic, (working title, ongoing analysis).

Ingeniero et al., Underway Measurement of Dissolved Nitric Oxide in the Tropical North Atlantic Ocean and in the Eastern Pacific Ocean.
Müller T et al., Gel-like particles distribution along a trophic gradient in the North Atlantic Ocean.

Pontiller B, Böhme F W, Hepach H, Engel A, Dissolved organic matter and nutrient availability across the tropical North Atlantic shape microbial community structure (working title, ongoing analysis, writing in progress).

Pontiller B, Böhme F W, Lundin D, Engel A, Expression patterns of carbohydrate, nitrogen, and phosphorus utilization by marine prokaryotes across the tropical North Atlantic, (working title, ongoing analysis, writing in progress).

Pontiller B, Lundin D, Knoop T, Biastoch, A., Engel. A, Tropical North Atlantic resistome: Exploring antibiotic resistance gene abundance, distribution, and connectivity from the eastern to the western tropical North Atlantic, (working title, ongoing analysis).

Quack B, Atlas E, Booge D, Cardoso C, Hepach H., Karnatz J, Potin P, Reis J, Rosa, A, Schmidt L, The biogeochemistry of halocarbons in the subtropical North Atlantic, (working title, ongoing analysis).

Scheidemann L, Schlundt C, Pontiller B, Galgani L, Beck A, Engel A, Abundance of small plastic marine Debris (PMD) in the surface equatorial Atlantic Ocean along an East to west transect and its colonisation by bacteria, (working title, ongoing analysis).

Weddell, Katherine, Links between Oceanic Ozone Uptake and Ocean Biology, PhD thesis, University of York, to be submitted 2024.

Xu, P et al., Metagenomic insights into variability of microbial diversity and functions in the Eastern Tropical Pacific Ocean, (writing in progress).

Xu, P et al., Do sinking particles promote vertical and horizontal connectivity in the ocean, (working title, ongoing analysis).

## LIST OF CONFERENCE PRESENTATIONS

2022 | **Vom Startschuss ins Ziel – Die sportliche Expedition SO287-CONNECT**
https://www geomar de/news/
article/16032022-vortragsreihe-wissenschaffen-online-vortragPublic

2022 | **The Chemical Controls on the Uptake of Ozone to the Ocean** iCACGP-IGAC
Joint Conference, Manchester, United Kingdom

2023 | **Halocarbon dynamics from Las Palmas to Guayaquil in winter 2021/2022 –**
**Results of SO287-CONNECT** EGU, Vienna, Austria
2023 | Measurements of trace gases with a MAX-DOAS system during a ship cruise from the Canaries to Ecuador (SO287) on board of RV Sonne EGU, Vienna, Austria

2023 | Variations in microbial community and organic matter composition along a coastal upwelling to open ocean continuum in the subtropical North Atlantic ASLO, Palma de Mallorca, Spain

2023 | Atmospheric Chemistry On and Over the Ocean Atmospheric Chemistry GRC Conference, Maine, USA

DATA

Continuous thermosalinograph oceanography along RV SONNE cruise track SO287: https://doi.org/10.1594/PANGAEA.953082

Multibeam bathymetry raw data (Kongsberg EM 122 entire dataset) of RV SONNE during cruise SO287: https://doi.org/10.1594/PANGAEA.943705

Master tracks in different resolutions of SONNE cruise SO287, Las Palmas - Guayaquil, 2021-12-11 – 2022-01-11. GEOMAR – Helmholtz Centre for Ocean Research Kiel: https://doi.org/10.1594/PANGAEA.944256

ADCP current measurements (75 kHz) during RV SONNE cruise SO287: https://doi.org/10.1594/PANGAEA.945808

Continuous bio-optical measurements of chlorophyll a and turbidity along RV SONNE cruise SO287 (CONNECT): https://doi.org/10.1594/PANGAEA.959910

Physical oceanography (CTD): https://portal geomar de /group /so287-connect/data

e. g. son_287_1_ctd_rel4.zip, SO287_ADCP_data_38and75KHz/raw, SO287_eddies.zip, SO287_OMPA_water masses

Biogeochemical variables:
https://portal geomar.de/group/so287-connect/data.

e. g. SO287_primaryproduction, SO287_bacphytvir_cellcounts, SO287_bacterialproduction, SO287_POCN_POP_BSi, SO287_pigmenteici HEREON.xlsx, SO287_CDOM_abs HEREON.xlsx, SO287_DOC_DON_DOP_CTD, SO287_Dissolved_carbohydrates_CTD, size-fractionned respiration rates using the in-vivo electron transport system method
Chemical variables:

https://portal geomar de /group /so287-connect/data.

e. g. SO287_UW_4ODV_1min_import.xlsx, SO287_UW_Masterfile.xlsx, SO287_CTD_Masterfile.xlsx, SO287_oxygen_and_nutrient_data, DMS_UW.txt, SO287incubation_NO, Underway_measurements_of_N2O__CH4_and_CO2__, DMS_CTD.txt

Atmospheric variables:

https://portal geomar de /group /so287-connect/data.

e. g. Trace_gas_canister_data, SO287-aerosol, SO287_Ozone.zip, SO287_photolysisRates_Leicester.xlsx, Surface ozone_minutely_clean.csv, IUP-Bremen_MAX-DOAS_and_InSitu_data.zip, SO287_Radiosondes.zip, SO287_AOD.zip

SDU Metagenomic sequence data has been archived in the NCBI Sequence Read Archive (SRA) database under the Bioproject PRJNA983277 from SRR24907232 to SRR24907253, which will be released after the work is published or after 2025.

CRUISE REPORT

SO287: doi:10.48433/cr_so287