Articles | Volume 17, issue 16
Research article 18 Aug 2020
Research article | 18 Aug 2020
Ocean acidification reduces growth and grazing impact of Antarctic heterotrophic nanoflagellates
Stacy Deppeler et al.
Stacy Deppeler, Katherina Petrou, Kai G. Schulz, Karen Westwood, Imojen Pearce, John McKinlay, and Andrew Davidson
Biogeosciences, 15, 209–231,Short summary
We combined productivity and photophysiology measurements to investigate the effects of ocean acidification on a natural Antarctic marine microbial community. Our study identifies a threshold for CO2 tolerance in the phytoplankton community between 953 and 1140 μatm of CO2, above which productivity declines. Bacteria were tolerant to CO2 up to 1641 μatm. We identify physiological changes in the phytoplankton at high CO2 that allowed them to acclimate to the high CO2 treatment.
Shao-Min Chen, Ulf Riebesell, Kai G. Schulz, Elisabeth von der Esch, Eric P. Achterberg, and Lennart T. Bach
Preprint under review for BGShort summary
Oxygen minimum zones in the ocean are characterized by enhanced carbon dioxide (CO2) levels and are being further acidified by increasing anthropogenic atmospheric CO2. Here we report CO2 system measurements in a mesocosm study offshore Peru during a rare coastal El Niño event, to investigate how CO2 dynamics may respond to on-going ocean deoxygenation. Our observations show that nitrogen limitation, productivity and plankton community shift play an important role in driving the CO2 dynamics.
Michelle N. Simone, Kai G. Schulz, Joanne M. Oakes, and Bradley D. Eyre
Biogeosciences, 18, 1823–1838,Short summary
Estuaries are responsible for a large contribution of dissolved organic carbon (DOC) to the global C cycle, but it is unknown how this will change in the future. DOC fluxes from unvegetated sediments were investigated ex situ subject to conditions of warming and ocean acidification. The future climate shifted sediment fluxes from a slight DOC source to a significant sink, with global coastal DOC export decreasing by 80 %. This has global implications for C cycling and long-term C storage.
Kai G. Schulz, Eric P. Achterberg, Javier Arístegui, Lennart T. Bach, Isabel Baños, Tim Boxhammer, Dirk Erler, Maricarmen Igarza, Verena Kalter, Andrea Ludwig, Carolin Löscher, Jana Meyer, Judith Meyer, Fabrizio Minutolo, Elisabeth von der Esch, Bess B. Ward, and Ulf Riebesell
Revised manuscript under review for BGShort summary
Upwelling of nutrient-rich deep waters to the surface make Eastern Boundary upwelling systems hotspots of marine productivity. This leads to sub-surface oxygen-depletion and transformation of bio-available nitrogen into inert N2. Here we quantify nitrogen loss processes following a simulated deep-water upwelling. Denitrification was the dominant process and budget calculations suggest that a significant portion of nitrogen that could be exported to depth is already lost in the surface ocean.
Lennart Thomas Bach, Allanah Joy Paul, Tim Boxhammer, Elisabeth von der Esch, Michelle Graco, Kai Georg Schulz, Eric Achterberg, Paulina Aguayo, Javier Arístegui, Patrizia Ayón, Isabel Baños, Avy Bernales, Anne Sophie Boegeholz, Francisco Chavez, Gabriela Chavez, Shao-Min Chen, Kristin Doering, Alba Filella, Martin Fischer, Patricia Grasse, Mathias Haunost, Jan Hennke, Nauzet Hernández-Hernández, Mark Hopwood, Maricarmen Igarza, Verena Kalter, Leila Kittu, Peter Kohnert, Jesus Ledesma, Christian Lieberum, Silke Lischka, Carolin Löscher, Andrea Ludwig, Ursula Mendoza, Jana Meyer, Judith Meyer, Fabrizio Minutolo, Joaquin Ortiz Cortes, Jonna Piiparinen, Claudia Sforna, Kristian Spilling, Sonia Sanchez, Carsten Spisla, Michael Sswat, Mabel Zavala Moreira, and Ulf Riebesell
Biogeosciences, 17, 4831–4852,Short summary
The eastern boundary upwelling system off Peru is among Earth's most productive ocean ecosystems, but the factors that control its functioning are poorly constrained. Here we used mesocosms, moored ~ 6 km offshore Peru, to investigate how processes in plankton communities drive key biogeochemical processes. We show that nutrient and light co-limitation keep productivity and export at a remarkably constant level while stoichiometry changes strongly with shifts in plankton community structure.
Bruce L. Greaves, Andrew T. Davidson, Alexander D. Fraser, John P. McKinlay, Andrew Martin, Andrew McMinn, and Simon W. Wright
Biogeosciences, 17, 3815–3835,Short summary
We observed that variation in the Southern Annular Mode (SAM) over 11 years showed a relationship with the species composition of hard-shelled phytoplankton in the seasonal ice zone (SIZ) of the Southern Ocean. Phytoplankton in the SIZ are productive during the southern spring and summer when the area is ice-free, with production feeding most Antarctic life. The SAM is known to be increasing with climate change, and changes in phytoplankton in the SIZ may have implications for higher life forms.
Richard Porter-Smith, John McKinlay, Alex Fraser, and Robert Massom
Earth Syst. Sci. Data Discuss.,
Revised manuscript accepted for ESSDShort summary
This study quantifies the characteristic complexity ‘signatures’ around the Antarctic outer coastal margin giving a multiscale estimate of the magnitude and direction of undulation or complexity at each point location along the entire coastline. It has numerous applications for both geophysical and biological studies and will contribute to Antarctic research requiring quantitative information about this important interface.
Yong Zhang, Lennart T. Bach, Kai T. Lohbeck, Kai G. Schulz, Luisa Listmann, Regina Klapper, and Ulf Riebesell
Biogeosciences, 15, 3691–3701,Short summary
To compare variations in physiological responses to pCO2 between populations, we measured growth, POC and PIC production rates at a pCO2 range from 120 to 2630 µatm for 17 strains of the coccolithophore Emiliania huxleyi from the Azores, Canary Islands, and Norwegian coast near Bergen. Optimal pCO2 for growth and POC production rates and tolerance to low pH was significantly higher for the Bergen population than the Azores and Canary Islands populations.
Natasha A. Gafar and Kai G. Schulz
Biogeosciences, 15, 3541–3560,Short summary
Emiliania huxleyi and Gephyrocapsa oceanica are the most prolific calcifying phytoplankton in today's oceans. We compare their sensitivity to combined anthropogenic stressors of temperature, light and CO2. For the future, we project a niche contraction for G. oceanica. Furthermore, there was good correlation of our new metric, the CaCO3 production potential, with satellite-derived concentrations in the modern ocean, indicating means of assessing overall coccolithophorid success in the future.
Alyce M. Hancock, Andrew T. Davidson, John McKinlay, Andrew McMinn, Kai G. Schulz, and Rick L. van den Enden
Biogeosciences, 15, 2393–2410,Short summary
Absorption of carbon dioxide (CO2) realized by humans is decreasing the ocean pH (ocean acidification). Single-celled organisms (microbes) support the Antarctic ecosystem, yet little is known about their sensitivity to ocean acidification. This study shows a shift in a natural Antarctic microbial community, with CO2 levels exceeding 634 μatm changing the community composition and favouring small cells. This would have significant flow effects for Antarctic food webs and elemental cycles.
Stacy Deppeler, Katherina Petrou, Kai G. Schulz, Karen Westwood, Imojen Pearce, John McKinlay, and Andrew Davidson
Biogeosciences, 15, 209–231,Short summary
We combined productivity and photophysiology measurements to investigate the effects of ocean acidification on a natural Antarctic marine microbial community. Our study identifies a threshold for CO2 tolerance in the phytoplankton community between 953 and 1140 μatm of CO2, above which productivity declines. Bacteria were tolerant to CO2 up to 1641 μatm. We identify physiological changes in the phytoplankton at high CO2 that allowed them to acclimate to the high CO2 treatment.
Coulson A. Lantz, Kai G. Schulz, Laura Stoltenberg, and Bradley D. Eyre
Biogeosciences, 14, 5377–5391,Short summary
This study examined the combined effect of seawater warming and organic matter enrichment on coral reef sediment metabolism. Sediments under control conditions were net autotrophic and net calcifying. Warming shifted the sediment to net heterotrophy and net dissolution, while organic matter enrichment increased net production and net calcification. When combined, the effects of each treatment were counterbalanced and sediment metabolism did not significantly differ from control treatments.
Hanieh T. Farid, Kai G. Schulz, and Andrew L. Rose
Manuscript not accepted for further reviewShort summary
This study provides new insights into: (a) how organic exudates from a marine cyanobacterium may influence iron speciation and bioavailability in the extracellular milieu; and (b) approaches for evaluating rate constants for Fe(II) oxidation in the presence of unknown organic ligands. Given that microorganisms play critical roles in biochemical cycling of trace metals in water systems, the findings are expected to improve nutrient uptake models and be of interest to broad range of readers.
Mitchell Call, Kai G. Schulz, Matheus C. Carvalho, Isaac R. Santos, and Damien T. Maher
Biogeosciences, 14, 1305–1313,Short summary
The conventional method for determining dissolved inorganic carbon (DIC) and it carbon stable isotope ratio (δ13C–DIC) can be a laborious process which can limit sampling frequency. This paper presents a new approach to autonomously determine DIC & δ13C–DIC at high temporal resolution. The simple method requires no customised design. Instead it uses two commercially available instruments and achieved a sampling resolution of 16 mins with precision and accuracy comparable to conventional methods.
Silke Lischka, Lennart T. Bach, Kai-Georg Schulz, and Ulf Riebesell
Biogeosciences, 14, 447–466,Short summary
We conducted a large-scale field experiment using 55 m3 floating containers (mesocosms) to investigate consequences of near-future projected CO2 elevations (ocean acidification) on a Baltic Sea plankton community in Storfjärden (Finland). The focus of our study was on single- and multicelled small-sized organisms dwelling in the water column. Our results suggest that increasing CO2 concentrations may change the species composition and promote specific food web interactions.
Thomas Hornick, Lennart T. Bach, Katharine J. Crawfurd, Kristian Spilling, Eric P. Achterberg, Jason N. Woodhouse, Kai G. Schulz, Corina P. D. Brussaard, Ulf Riebesell, and Hans-Peter Grossart
Biogeosciences, 14, 1–15,
Kristian Spilling, Kai G. Schulz, Allanah J. Paul, Tim Boxhammer, Eric P. Achterberg, Thomas Hornick, Silke Lischka, Annegret Stuhr, Rafael Bermúdez, Jan Czerny, Kate Crawfurd, Corina P. D. Brussaard, Hans-Peter Grossart, and Ulf Riebesell
Biogeosciences, 13, 6081–6093,Short summary
We performed an experiment in the Baltic Sea in order to investigate the consequences of the increasing CO2 levels on biological processes in the free water mass. There was more accumulation of organic carbon at high CO2 levels. Surprisingly, this was caused by reduced loss processes (respiration and bacterial production) in a high-CO2 environment, and not by increased photosynthetic fixation of CO2. Our carbon budget can be used to better disentangle the effects of ocean acidification.
Francesca Gallo, Kai G. Schulz, Eduardo B. Azevedo, João Madruga, and Joana Barcelos e Ramos
Revised manuscript not acceptedShort summary
Global change driven by humans activities may affect phytoplankton, which are important primary producers. Assessing the combined effect of turbulence and ocean acidification on the species Asterionellopsis glacialis, we found that turbulence magnifies the acidification stress, with negative effects on their growth. In the natural environment, this might have consequences to phytoplankton community composition and production with feedbacks to climate.
Kristian Spilling, Allanah J. Paul, Niklas Virkkala, Tom Hastings, Silke Lischka, Annegret Stuhr, Rafael Bermúdez, Jan Czerny, Tim Boxhammer, Kai G. Schulz, Andrea Ludwig, and Ulf Riebesell
Biogeosciences, 13, 4707–4719,Short summary
Anthropogenic carbon dioxide (CO2) emissions are reducing the pH in the world's oceans. We determined the plankton community composition and measured primary production, respiration rates and carbon export during an ocean acidification experiment. Our results suggest that increased CO2 reduced respiration and increased net carbon fixation at high CO2. This did not, however, translate into higher carbon export, and consequently did not work as a negative feedback mechanism for decreasing pH.
Juntian Xu, Lennart T. Bach, Kai G. Schulz, Wenyan Zhao, Kunshan Gao, and Ulf Riebesell
Biogeosciences, 13, 4637–4643,
Alison L. Webb, Emma Leedham-Elvidge, Claire Hughes, Frances E. Hopkins, Gill Malin, Lennart T. Bach, Kai Schulz, Kate Crawfurd, Corina P. D. Brussaard, Annegret Stuhr, Ulf Riebesell, and Peter S. Liss
Biogeosciences, 13, 4595–4613,Short summary
This paper presents concentrations of several trace gases produced by the Baltic Sea phytoplankton community during a mesocosm experiment with five different CO2 levels. Average concentrations of dimethylsulphide were lower in the highest CO2 mesocosms over a 6-week period, corresponding to previous mesocosm experiment results. No dimethylsulfoniopropionate was detected due to a methodological issue. Concentrations of iodine- and bromine-containing halocarbons were unaffected by increasing CO2.
Allanah J. Paul, Eric P. Achterberg, Lennart T. Bach, Tim Boxhammer, Jan Czerny, Mathias Haunost, Kai-Georg Schulz, Annegret Stuhr, and Ulf Riebesell
Biogeosciences, 13, 3901–3913,
Anna Jansson, Silke Lischka, Tim Boxhammer, Kai G. Schulz, and Joanna Norkko
Biogeosciences, 13, 3377–3385,Short summary
We studied the responses of larvae of Macoma balthica to a range of future CO2 scenarios using large mesocosms encompassing the entire pelagic community. We focused on the growth and settlement process of M. balthica when exposed to future CO2 levels, and found the size and time to settlement to increase along the CO2 gradient, suggesting a developmental delay. The strong impact of increasing CO2 on early-stage bivalves is alarming as these stages are crucial for sustaining viable populations.
Monika Nausch, Lennart Thomas Bach, Jan Czerny, Josephine Goldstein, Hans-Peter Grossart, Dana Hellemann, Thomas Hornick, Eric Pieter Achterberg, Kai-Georg Schulz, and Ulf Riebesell
Biogeosciences, 13, 3035–3050,Short summary
Studies investigating the effect of increasing CO2 levels on the phosphorus cycle in natural waters are lacking although phosphorus often controls phytoplankton development in aquatic systems. The aim of our study was to analyse effects of elevated CO2 levels on phosphorus pool sizes and uptake. Therefore, we conducted a CO2-manipulation mesocosm experiment in the Storfjärden (western Gulf of Finland, Baltic Sea) in summer 2012. We compared the phosphorus dynamics in different mesocosm treatment
M. N. Müller, J. Barcelos e Ramos, K. G. Schulz, U. Riebesell, J. Kaźmierczak, F. Gallo, L. Mackinder, Y. Li, P. N. Nesterenko, T. W. Trull, and G. M. Hallegraeff
Biogeosciences, 12, 6493–6501,Short summary
The White Cliffs of Dover date back to the Cretaceous and are made up of microscopic chalky shells which were produced mainly by marine phytoplankton (coccolithophores). This is iconic proof for their success at times of relatively high seawater calcium concentrations and, as shown here, to be linked to their ability to precipitate calcium as chalk. The invention of calcification can thus be considered an evolutionary milestone allowing coccolithophores to thrive at times when others struggled.
A. J. Paul, L. T. Bach, K.-G. Schulz, T. Boxhammer, J. Czerny, E. P. Achterberg, D. Hellemann, Y. Trense, M. Nausch, M. Sswat, and U. Riebesell
Biogeosciences, 12, 6181–6203,
M. N. Müller, M. Lebrato, U. Riebesell, J. Barcelos e Ramos, K. G. Schulz, S. Blanco-Ameijeiras, S. Sett, A. Eisenhauer, and H. M. Stoll
Biogeosciences, 11, 1065–1075,
U. Riebesell, J. Czerny, K. von Bröckel, T. Boxhammer, J. Büdenbender, M. Deckelnick, M. Fischer, D. Hoffmann, S. A. Krug, U. Lentz, A. Ludwig, R. Muche, and K. G. Schulz
Biogeosciences, 10, 1835–1847,
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Biogeosciences, 18, 2301–2323,Short summary
Michaelis–Menten kinetics were determined for alkaline phosphatase, aminopeptidase and β-glucosidase in the Mediterranean Sea. Although the ectoenzymatic-hydrolysis contribution to heterotrophic prokaryotic needs was high in terms of N, it was low in terms of C. This study points out the biases in interpretation of the relative differences in activities among the three tested enzymes in regard to the choice of added concentrations of fluorogenic substrates.
Oscar E. Romero, Simon Ramondenc, and Gerhard Fischer
Biogeosciences, 18, 1873–1891,Short summary
Upwelling intensity along NW Africa varies on the interannual to decadal timescale. Understanding its changes is key for the prediction of future changes of CO2 sequestration in the northeastern Atlantic. Based on a multiyear (1988–2009) sediment trap experiment at the site CBmeso, fluxes and the species composition of the diatom assemblage are presented. Our data help in establishing the scientific basis for forecasting and modeling future states of this ecosystem and its decadal changes.
Katharine T. Bigham, Ashley A. Rowden, Daniel Leduc, and David A. Bowden
Biogeosciences, 18, 1893–1908,Short summary
Turbidity flows – underwater avalanches – are large-scale physical disturbances believed to have profound impacts on productivity and diversity of benthic communities in the deep sea. We reviewed published studies and found that current evidence for changes in productivity is ambiguous at best, but the influence on regional and local diversity is clearer. We suggest study design criteria that may lead to a better understanding of large-scale disturbance effects on deep-sea benthos.
Phillip Williamson, Hans-Otto Pörtner, Steve Widdicombe, and Jean-Pierre Gattuso
Biogeosciences, 18, 1787–1792,Short summary
The reliability of ocean acidification research was challenged in early 2020 when a high-profile paper failed to corroborate previously observed impacts of high CO2 on the behaviour of coral reef fish. We now know the reason why: the
replicatedstudies differed in many ways. Open-minded and collaborative assessment of all research results, both negative and positive, remains the best way to develop process-based understanding of the impacts of ocean acidification on marine organisms.
Michael Lintner, Bianca Lintner, Wolfgang Wanek, Nina Keul, and Petra Heinz
Biogeosciences, 18, 1395–1406,Short summary
Foraminifera are unicellular marine organisms that play an important role in the marine element cycle. Changes of environmental parameters such as salinity or temperature have a significant impact on the faunal assemblages. Our experiments show that changes in salinity immediately influence the foraminiferal activity. Also the light regime has a significant impact on carbon or nitrogen processing in foraminifera which contain no kleptoplasts.
Michele Casini, Martin Hansson, Alessandro Orio, and Karin Limburg
Biogeosciences, 18, 1321–1331,Short summary
In the past 20 years the condition of the eastern Baltic cod has dropped, with large implications for the fishery. Our results show that simultaneously the cod population has moved deeper while low-oxygenated waters detrimental for cod growth have become shallower. Cod have thus dwelled more in detrimental waters, explaining the drop in its condition. This study, using long-term fish and hydrological monitoring data, evidences the impact of deoxygenation on fish biology and fishing.
Elizabeth D. LaBone, Kenneth A. Rose, Dubravko Justic, Haosheng Huang, and Lixia Wang
Biogeosciences, 18, 487–507,Short summary
The hypoxic zone is an area of low dissolved oxygen (DO) in the Gulf of Mexico. Fish can be killed by exposure to hypoxia and can be negatively impacted by exposure to low, nonlethal DO concentrations (sublethal DO). We found that high sublethal area resulted in higher exposure and DO variability had a small effect on exposure. There was a large variation in exposure among individuals, which when combined with spatial variability of DO, can result in an underestimation of exposure when averaged.
Svenja Reents, Peter Mueller, Hao Tang, Kai Jensen, and Stefanie Nolte
Biogeosciences, 18, 403–411,Short summary
By conducting a flooding experiment with two genotypes of the salt-marsh grass Elymus athericus, we show considerable differences in biomass response to flooding within the same species. As biomass production plays a major role in sedimentation processes and thereby salt-marsh accretion, we emphasise the importance of taking intraspecific differences into account when evaluating ecosystem resilience to accelerated sea level rise.
Cara Nissen and Meike Vogt
Biogeosciences, 18, 251–283,Short summary
Using a regional Southern Ocean ecosystem model, we find that the relative importance of Phaeocystis and diatoms at high latitudes is controlled by iron and temperature variability, with light levels controlling the seasonal succession in coastal areas. Yet, biomass losses via aggregation and grazing matter as well. We show that the seasonal succession of Phaeocystis and diatoms impacts the seasonality of carbon export fluxes with ramifications for nutrient cycling and food web dynamics.
Jiangtao Li, Lingyuan Gu, Shijie Bai, Jie Wang, Lei Su, Bingbing Wei, Li Zhang, and Jiasong Fang
Biogeosciences, 18, 113–133,Short summary
Few studies have focused on the particle-attached (PA) and free-living (FL) microbes of the deep ocean. Here we determined PA and FL microbial communities along depth profiles of the SCS. PA and FL fractions accommodated divergent microbial compositions, and most of them are potentially generalists with PA and FL dual lifestyles. A potential vertical connectivity between surface-specific microbes and those in the deep ocean was indicated, likely through microbial attachment to sinking particles.
Saskia Brix, Karen J. Osborn, Stefanie Kaiser, Sarit B. Truskey, Sarah M. Schnurr, Nils Brenke, Marina Malyutina, and Pedro Martinez Arbizu
Biogeosciences, 17, 6163–6184,Short summary
The Clarion–Clipperton Fracture Zone (CCZ) located in the Pacific is commercially the most important area of proposed manganese nodule mining. Extraction of this will influence the life and distribution of small deep-sea invertebrates like peracarid crustaceans, of which >90 % are undescribed species new to science. We are doing a species delimitation approach as baseline for an ecological interpretation of species distribution and discuss the results in light of future deep-sea conservation.
Amal Jayakumar and Bess B. Ward
Biogeosciences, 17, 5953–5966,Short summary
Diversity and community composition of nitrogen-fixing microbes in the three main oxygen minimum zones of the world ocean were investigated using nifH clone libraries. Representatives of three main clusters of nifH genes were detected. Sequences were most diverse in the surface waters. The most abundant OTUs were affiliated with Alpha- and Gammaproteobacteria. The sequences were biogeographically distinct and the dominance of a few OTUs was commonly observed in OMZs in this (and other) studies.
Guillermo Feliú, Marc Pagano, Pamela Hidalgo, and François Carlotti
Biogeosciences, 17, 5417–5441,Short summary
The impact of Saharan dust deposition events on the Mediterranean Sea ecosystem was studied during a basin-scale survey (PEACETIME cruise, May–June 2017). Short-term responses of the zooplankton community were observed after episodic dust deposition events, highlighting the impact of these events on productivity up to the zooplankton level in the poorly fertilized pelagic ecosystems of the southern Mediterranean Sea.
Douglas Lessa, Raphaël Morard, Lukas Jonkers, Igor M. Venancio, Runa Reuter, Adrian Baumeister, Ana Luiza Albuquerque, and Michal Kucera
Biogeosciences, 17, 4313–4342,Short summary
We observed that living planktonic foraminifera had distinct vertically distributed communities across the Subtropical South Atlantic. In addition, a hierarchic alternation of environmental parameters was measured to control the distribution of planktonic foraminifer's species depending on the water depth. This implies that not only temperature but also productivity and subsurface processes are signed in fossil assemblages, which could be used to perform paleoceanographic reconstructions.
Karl M. Attard and Ronnie N. Glud
Biogeosciences, 17, 4343–4353,Short summary
Light-use efficiency defines the ability of primary producers to convert sunlight energy to primary production. This report provides a framework to compute hourly and daily light-use efficiency using underwater eddy covariance, a recent technological development that produces habitat-scale rates of primary production for many different habitat types. The approach, tested on measured flux data, provides a useful means to compare habitat productivity across time and space.
Mirjana Najdek, Marino Korlević, Paolo Paliaga, Marsej Markovski, Ingrid Ivančić, Ljiljana Iveša, Igor Felja, and Gerhard J. Herndl
Biogeosciences, 17, 3299–3315,Short summary
The response of Cymodocea nodosa to environmental changes was reported during a 15-month period. The meadow decline was triggered in spring by the simultaneous reduction of available light in the water column and the creation of anoxic conditions in the rooted area. This disturbance was critical for the plant since it took place during its recruitment phase when metabolic needs are maximal and stored reserves minimal. The loss of such habitat-forming seagrass is a major environmental concern.
Timm Schoening, Autun Purser, Daniel Langenkämper, Inken Suck, James Taylor, Daphne Cuvelier, Lidia Lins, Erik Simon-Lledó, Yann Marcon, Daniel O. B. Jones, Tim Nattkemper, Kevin Köser, Martin Zurowietz, Jens Greinert, and Jose Gomes-Pereira
Biogeosciences, 17, 3115–3133,Short summary
Seafloor imaging is widely used in marine science and industry to explore and monitor areas of interest. The selection of the most appropriate imaging gear and deployment strategy depends on the target application. This paper compares imaging platforms like autonomous vehicles or towed camera frames and different deployment strategies of those in assessing the megafauna abundance of polymetallic-nodule fields. The deep-sea mining industry needs that information for robust impact monitoring.
Tatsuro Tanioka and Katsumi Matsumoto
Biogeosciences, 17, 2939–2954,Short summary
We conducted an extensive literature survey (meta-analysis) on how the C : N : P ratio varies with change in key environmental drivers. We found that the expected reduction in nutrients and warming under the future climate change scenario is likely to result in increased C : P and C : N of marine phytoplankton. Further, our findings highlight the greater stoichiometric plasticity of eukaryotes over prokaryotes, which provide us insights on how to understand and model plankton.
Vanessa Joglar, Antero Prieto, Esther Barber-Lluch, Marta Hernández-Ruiz, Emilio Fernández, and Eva Teira
Biogeosciences, 17, 2807–2823,Short summary
Coastal marine ecosystems are among the most ecologically and economically productive areas providing a large fraction of ecosystem goods and services to human populations, and B vitamins have long been considered important growth factors for phytoplankton. Our findings indicate that the responses of microbial plankton to B-vitamin supply are mainly driven by the bacterial community composition and that microbial plankton in this area seems to be well adapted to cope with B-vitamin shortage.
Tasnim Patel, Henri Robert, Cedric D'Udekem D'Acoz, Koen Martens, Ilse De Mesel, Steven Degraer, and Isa Schön
Biogeosciences, 17, 2731–2744,Short summary
Exploitation of deep-sea resources in one of the largest ecosystems on the planet has rendered research of its biodiversity more urgent than ever before. We investigated the known habitats and connectivity of deep-sea scavenging amphipods and obtained important knowledge about several species. We also demonstrated that a long-term disturbance experiment has possibly reduced amphipod biodiversity. These data and further sampling expeditions are instrumental for formulating sustainable policies.
Daphne Cuvelier, Pedro A. Ribeiro, Sofia P. Ramalho, Daniel Kersken, Pedro Martinez Arbizu, and Ana Colaço
Biogeosciences, 17, 2657–2680,Short summary
Polymetallic nodule mining will remove hard substrata from the abyssal deep-sea floor. The only neighbouring ecosystems featuring hard substratum are seamounts, and their inhabiting fauna could aid in recovery post-mining. Nevertheless, first observations of seamount megafauna were very different from nodule-associated megafauna and showed little overlap. The possible uniqueness of these ecosystems implies that they should be included in management plans for the conservation of biodiversity.
Karen F. Wishner, Brad Seibel, and Dawn Outram
Biogeosciences, 17, 2315–2339,Short summary
Increasing deoxygenation and oxygen minimum zone expansion are consequences of global warming. Copepod species had different vertical distribution strategies and physiologies associated with oxygen profile variability (0–1000 m). Species (1) changed vertical distributions and maximum abundance depth, (2) shifted diapause depth, (3) changed diel vertical migration depths, or (4) changed epipelagic depth range in the aerobic mixed layer. Present-day variability helps predict future scenarios.
Magdalini Christodoulou, Timothy O'Hara, Andrew F. Hugall, Sahar Khodami, Clara F. Rodrigues, Ana Hilario, Annemiek Vink, and Pedro Martinez Arbizu
Biogeosciences, 17, 1845–1876,Short summary
Unexpectedly high diversity was revealed in areas licenced for polymetallic nodule mining exploration in the Pacific Ocean. For the first time, a comprehensive reference library including 287 novel ophiuroid sequences allocated to 43 species was produced. Differences in food availability along the nodule province of CCZ were reflected in the biodiversity patterns observed. The APEI3's dissimilarity with the exploration contract areas questions its ability to serve as a biodiversity reservoir.
Julie Meilland, Hélène Howa, Vivien Hulot, Isaline Demangel, Joëlle Salaün, and Thierry Garlan
Biogeosciences, 17, 1437–1450,Short summary
This study reports on planktonic foraminifera (PF) diversity and distribution in the Barents Sea. The species Globigerinita uvula and Turborotalita quinqueloba dominate the water column while surface sediments are dominated by Neogloboquadrina pachyderma. We hypothesize the unusual dominance of G. uvula in the water to be a seasonal signal or a result of climate forcing. Size-normalized-protein concentrations of PF show a northward decrease, suggesting biomass to vary with the environment.
Julien Richirt, Bettina Riedel, Aurélia Mouret, Magali Schweizer, Dewi Langlet, Dorina Seitaj, Filip J. R. Meysman, Caroline P. Slomp, and Frans J. Jorissen
Biogeosciences, 17, 1415–1435,Short summary
The paper presents the response of benthic foraminiferal communities to seasonal absence of oxygen coupled with the presence of hydrogen sulfide, considered very harmful for several living organisms. Our results suggest that the foraminiferal community mainly responds as a function of the duration of the adverse conditions. This knowledge is especially useful to better understand the ecology of benthic foraminifera but also in the context of palaeoceanographic interpretations.
Xiangqi Yi, Fei-Xue Fu, David A. Hutchins, and Kunshan Gao
Biogeosciences, 17, 1169–1180,Short summary
Combined effects of warming and light intensity were estimated in N2-fixing cyanobacterium Trichodesmium. Its physiological responses to warming were significantly modulated by light, with growth peaking at 27 °C under the light-saturating condition but being non-responsive across the range of 23–31 °C under the light-limiting condition. Light shortage also weakened the acclimation ability of Trichodesmium to warming, making light-limited Trichodesmium more sensitive to acute temperature change.
Jan Goleń, Jarosław Tyszka, Ulf Bickmeyer, and Jelle Bijma
Biogeosciences, 17, 995–1011,Short summary
We studied the organisation and dynamics of actin in foraminifera. Actin is one of the key structural proteins in most lifeforms. Our investigations show that in foraminifera it forms small granules, around 1 µm in diameter, that display rapid movement. This granularity is unusual in comparison to other organisms. We suppose that these granules are most likely involved in the formation of all types of pseudopods responsible for movement, food capturing, biomineralisation, and other functions.
Paulo Bonifácio, Pedro Martínez Arbizu, and Lénaïck Menot
Biogeosciences, 17, 865–886,Short summary
The patterns observed in the composition of polychaete assemblages were attributed to variations in food supply at the regional scale and nodule density at the local scale. The high levels of species replacement were mainly driven by rare species, leading to regional species pool estimates between 498 and 240 000 species. The high proportion of singletons seems reflect an under-sampling bias that is currently preventing the assessment of potential biodiversity loss due to nodule mining.
Finn Mielck, Rune Michaelis, H. Christian Hass, Sarah Hertel, Caroline Ganal, and Werner Armonies
Revised manuscript accepted for BGShort summary
Marine sand mining becomes more and more important to nourish fragile coastlines that face the global change. We investigated the largest sand extraction site in the German Bight. The study reveals that after more than 35 years of mining, the excavation pits are still detectable on the seafloor while the sediment composion largly changed. The organic communities living in and on the seafloor were strongly decimated and no recovery is observable towards previous conditions.
Stephanie Dutkiewicz, Pedro Cermeno, Oliver Jahn, Michael J. Follows, Anna E. Hickman, Darcy A. A. Taniguchi, and Ben A. Ward
Biogeosciences, 17, 609–634,Short summary
Phytoplankton are an essential component of the marine food web and earth's carbon cycle. We use observations, ecological theory and a unique trait-based ecosystem model to explain controls on patterns of marine phytoplankton biodiversity. We find that different dimensions of diversity (size classes, biogeochemical functional groups, thermal norms) are controlled by a disparate combination of mechanisms. This may explain why previous studies of phytoplankton diversity had conflicting results.
Emily White, Clara J. M. Hoppe, and Björn Rost
Biogeosciences, 17, 635–647,Short summary
The Arctic picoeukaryote Micromonas pusilla was acclimated to two pCO2 levels under a constant and a dynamic light, simulating more realistic light fields. M. pusilla was able to benefit from ocean acidification with an increase in growth rate, irrespective of the light regime. In dynamic light M. pusilla optimised its photophysiology for effective light usage during both low- and high-light periods. This highlights M. pusilla is likely to cope well with future conditions in the Arctic Ocean.
Oscar E. Romero, Karl-Heinz Baumann, Karin A. F. Zonneveld, Barbara Donner, Jens Hefter, Bambaye Hamady, Vera Pospelova, and Gerhard Fischer
Biogeosciences, 17, 187–214,Short summary
Monitoring of the multiannual evolution of populations representing different trophic levels allows for obtaining insights into the impact of climate variability in marine coastal upwelling ecosystems. By using a multiyear, continuous (1,900 d) sediment trap record, we assess the dynamics and fluxes of calcareous, organic and siliceous microorganisms off Mauritania (NW Africa). The experiment allowed for the recognition of a general sequence of seasonal variations of the main populations.
Ulrike Hanz, Claudia Wienberg, Dierk Hebbeln, Gerard Duineveld, Marc Lavaleye, Katriina Juva, Wolf-Christian Dullo, André Freiwald, Leonardo Tamborrino, Gert-Jan Reichart, Sascha Flögel, and Furu Mienis
Biogeosciences, 16, 4337–4356,Short summary
Along the Namibian and Angolan margins, low oxygen conditions do not meet environmental ranges for cold–water corals and hence are expected to be unsuitable habitats. Environmental conditions show that tidal movements deliver water with more oxygen and high–quality organic matter, suggesting that corals compensate unfavorable conditions with availability of food. With the expected expansion of oxygen minimum zones in the future, this study provides an example how ecosystems cope with extremes.
Alexia Dubuc, Ronald Baker, Cyril Marchand, Nathan J. Waltham, and Marcus Sheaves
Biogeosciences, 16, 3959–3976,Short summary
Little is known about how hypoxia influences mangrove fish assemblages. In situ video observations reveal species-specific avoidance strategies in response to developing hypoxia in a mangrove forest. Taxa commonly using mangroves could withstand hypoxia, while others usually associated with reef habitats were not recorded below 70 % saturation. These results suggest that hypoxia is an important factor shaping mangrove fish assemblages and could explain the low species richness usually observed.
Mariem Saavedra-Pellitero, Karl-Heinz Baumann, Miguel Ángel Fuertes, Hartmut Schulz, Yann Marcon, Nele Manon Vollmar, José-Abel Flores, and Frank Lamy
Biogeosciences, 16, 3679–3702,Short summary
Open ocean phytoplankton include coccolithophore algae, a key element in carbon cycle regulation with important feedbacks to the climate system. We document latitudinal variability in both coccolithophore assemblage and the mass variation in one particular species, Emiliania huxleyi, for a transect across the Drake Passage (in the Southern Ocean). Coccolithophore abundance, diversity and maximum depth habitat decrease southwards, coinciding with changes in the predominant E. huxleyi morphotypes.
Freija Hauquier, Lara Macheriotou, Tania N. Bezerra, Great Egho, Pedro Martínez Arbizu, and Ann Vanreusel
Biogeosciences, 16, 3475–3489,Short summary
Future mining operations in the deep sea provide a source of scientific uncertainty and call for detailed study of the ecosystem. We investigated one of the most diverse and abundant taxa present in deep-sea sediments, nematodes, and demonstrate the importance of sediment attributes for their communities. Especially species that are less common and have a limited spatial distribution will be vulnerable to mining-induced changes. Our findings can serve as a reference for future impact studies.
Haruka Takagi, Katsunori Kimoto, Tetsuichi Fujiki, Hiroaki Saito, Christiane Schmidt, Michal Kucera, and Kazuyoshi Moriya
Biogeosciences, 16, 3377–3396,Short summary
Photosymbiosis (endosymbiosis with algae) is an evolutionary important ecology for many marine organisms but has poorly been identified among planktonic foraminifera. In this study, we identified and characterized photosymbiosis of various species of planktonic foraminifera by focusing on their photosynthesis–related features. We finally proposed a new framework showing a potential strength of photosymbiosis, which will serve as a basis for future ecological studies of planktonic foraminifera.
Elina A. Virtanen, Alf Norkko, Antonia Nyström Sandman, and Markku Viitasalo
Biogeosciences, 16, 3183–3195,Short summary
Our understanding of the drivers of hypoxia fundamentally hinges on patterns of water circulation and vertical mixing that can be difficult to resolve in coastal regions. We identified areas prone to oxygen loss in a complex marine area without knowledge of biogeochemical properties, using only parameters which describe the enclosed seafloors with restricted water exchange. Our approach could help nutrient abatement measures and pinpoint areas where management actions are most urgently needed.
Jeffrey C. Drazen, Astrid B. Leitner, Sage Morningstar, Yann Marcon, Jens Greinert, and Autun Purser
Biogeosciences, 16, 3133–3146,Short summary
We investigated the fish and scavenger community after a deep seafloor disturbance experiment intended to simulate the effects of deep-sea mining. Fish density returned to background levels after several years; however the dominant fish was rarely found in ploughed habitat after 26 years. Given the significantly larger scale of industrial mining, these results could translate to population-level effects. The abyssal fish community at the site was similar to that in the Clarion–Clipperton Zone.
Scarlett Trimborn, Silke Thoms, Pascal Karitter, and Kai Bischof
Biogeosciences, 16, 2997–3008,Short summary
Ecophysiological studies on Antarctic cryptophytes to assess whether climatic changes such as ocean acidification and enhanced stratification affect their growth in Antarctic coastal waters in the future are lacking so far. Our results reveal beneficial effects of ocean acidification in conjunction with enhanced irradiance on growth and photosynthesis of the Antarctic cyrptophyte Geminigera cryophila. Hence, cryptophytes such as G. cryophila may be potential winners of these climatic changes.
Daffne C. López-Sandoval, Katherine Rowe, Paloma Carillo-de-Albonoz, Carlos M. Duarte, and Susana Agustí
Biogeosciences, 16, 2983–2995,Short summary
We addressed how the intertwined effect of temperature and nutrients modulates the metabolic response of planktonic communities in the Red Sea, one of the warmest seas on earth. Our study unveiled that photosynthesis increases at a faster pace than respiration rates for this group of organisms formed by microalgae, bacteria, and drifting animals. This anomaly is likely due to the nature of the basin where the warmest waters are frequently enriched with nutrients, which favours microalgae growth.
Camilla Parzanini, Christopher C. Parrish, Jean-François Hamel, and Annie Mercier
Biogeosciences, 16, 2837–2856,Short summary
This review synthesized current knowledge of deep-sea food webs and provided a preliminary analysis of global geographic patterns in the biochemical composition of deep-water organisms. Our results revealed both latitudinal and depth wise trends in the biochemical composition of deep-sea animals. In addition, the link across latitudes between surface primary production and deep-water communities was highlighted, which has important implications in the face of global climate change.
Susann Rossbach, Vincent Saderne, Andrea Anton, and Carlos M. Duarte
Biogeosciences, 16, 2635–2650,Short summary
Giant clams including the species Tridacna maxima are unique among bivalves as they live in symbiosis with unicellular algae and generally function as net photoautotrophs. Light is therefore crucial for these species to thrive. We show that net calcification and photosynthetic rates of T. maxima are light dependent, with maximum rates at conditions comparable to 4 m water depth, reflected also in the depth-related distribution in the Red Sea with maximum abundances in shallow sunlit coral reefs.
Lisa Mevenkamp, Katja Guilini, Antje Boetius, Johan De Grave, Brecht Laforce, Dimitri Vandenberghe, Laszlo Vincze, and Ann Vanreusel
Biogeosciences, 16, 2329–2341,Short summary
To elucidate the potential effects of crushed nodule particle deposition on abyssal meiobenthos, we covered abyssal soft sediment in the Peru Basin (4200 m depth) with approximately 2 cm of this nodule material for 11 d. About half of the meiobenthos migrated from the sediment into the added material, and nematode feeding type proportions in that added layer were altered. These results considerably contribute to our understanding of the short-term responses of deep-sea meiobenthos to burial.
Maria Grigoratou, Fanny M. Monteiro, Daniela N. Schmidt, Jamie D. Wilson, Ben A. Ward, and Andy Ridgwell
Biogeosciences, 16, 1469–1492,Short summary
The paper presents a novel study based on the traits of shell size, calcification and feeding behaviour of two planktonic foraminifera life stages using modelling simulations. With the model, we tested the cost and benefit of calcification and explored how the interactions of planktonic foraminifera among other plankton groups influence their biomass under different environmental conditions. Our results provide new insights into environmental controls in planktonic foraminifera ecology.
Shanying Tong, David A. Hutchins, and Kunshan Gao
Biogeosciences, 16, 561–572,Short summary
Most previous studies concerning the effects of environmental changes on marine organisms have been carried out under
photosynthetically active radiation onlyconditions, with solar ultraviolet radiation (UVR) not being considered. In this study, we found that UVR can counteract the negative effects of the
greenhousetreatment on the calcification rate to photosynthesis rate ratio, and may be a key stressor when considering the impacts of future greenhouse conditions on E. huxleyi.
Catherine A. Pfister and Mark A. Altabet
Biogeosciences, 16, 193–206,Short summary
Microbial assemblages on host plants and animals are an increasingly recognized biological phenomenon. We present evidence that microbes in association with mussels and seaweeds are contributing greatly to nitrogen cycling in coastal marine areas, often many times that of the microbes that are simply free-living in seawater. The addition of dissolved organic carbon increased nutrient uptake by microbes, suggesting that coastal species enhance microbial metabolism through resource provisioning.
François Carlotti, Marc Pagano, Loïc Guilloux, Katty Donoso, Valentina Valdés, Olivier Grosso, and Brian P. V. Hunt
Biogeosciences, 15, 7273–7297,Short summary
The paper characterizes the zooplankton community and plankton food web processes between New Caledonia and Tahiti (tropical South Pacific) during the austral summer 2015. In this region, the pelagic production depends on N2 fixation by diazotroph microorganisms on which the zooplankton community feeds, supporting a pelagic food chain ending with valuable tuna fisheries. We estimated a contribution of up to 75 % of diazotroph‐derived nitrogen to zooplankton biomass in the Melanesian archipelago.
Ana Martinez, Laura Hernández-Terrones, Mario Rebolledo-Vieyra, and Adina Paytan
Biogeosciences, 15, 6819–6832,Short summary
Our study at low-pH submarine springs suggests that ocean acidification may reduce the number of Caribbean benthic foraminifera, particularly those species that form carbonate shells. This may have subsequent repercussions on the global carbon cycle and marine food webs that depend on benthic foraminifera.
Janet E. Burke, Willem Renema, Michael J. Henehan, Leanne E. Elder, Catherine V. Davis, Amy E. Maas, Gavin L. Foster, Ralf Schiebel, and Pincelli M. Hull
Biogeosciences, 15, 6607–6619,Short summary
Metabolic rates are sensitive to environmental conditions and can skew geochemical measurements. However, there is no way to track these rates through time. Here we investigate the controls of test porosity in planktonic foraminifera (organisms commonly used in paleoclimate studies) as a potential proxy for metabolic rate. We found that the porosity varies with body size and temperature, two key controls on metabolic rate, and that it can respond to rapid changes in ambient temperature.
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Our study showed how ocean acidification can exert both direct and indirect influences on the interactions among trophic levels within the microbial loop. Microbial grazer abundance was reduced at CO2 concentrations at and above 634 µatm, while microbial communities increased in abundance, likely due to a reduction in being grazed. Such changes in predator–prey interactions with ocean acidification could have significant effects on the food web and biogeochemistry in the Southern Ocean.
Our study showed how ocean acidification can exert both direct and indirect influences on the...