Spring–summer net community production, new production, particle export and related water column biogeochemical processes in the marginal sea ice zone of the Western Antarctic Peninsula 2012–2014

New production (New P, the rate of net primary production (NPP) supported by exogenously supplied limiting nutrients) and net community production (NCP, gross primary production not consumed by community respiration) are closely related but mechanistically distinct processes. They set the carbon balance in the upper ocean and define an upper limit for export from the system. The relationships, relative magnitudes and variability of New P (from 15 NO 3 – uptake), O 2 : argon-based NCP and sinking particle export (based on the 238 U : 234 Th disequilibrium) are increasingly well documented but still not clearly understood. This is especially true in remote regions such as polar marginal ice zones. Here we present a 3-year dataset of simultaneous measurements made at approximately 50 stations along the Western Antarctic Peninsula (WAP) continental shelf in midsummer (January) 2012–2014. Net seasonal-scale changes in water column inventories (0–150 m) of nitrate and iodide were also estimated at the same stations. The average daily rates based on inventory changes exceeded the shorter-term rate measurements. A major uncertainty in the relative magnitude of the inventory estimates is specifying the start of the growing season following sea-ice retreat. New P and NCP(O 2 ) did not differ significantly. New P and NCP(O 2 ) were significantly greater than sinking particle export from thorium-234. We suggest this is a persistent and systematic imbalance and that other processes such as vertical mixing and advection of suspended particles are important export pathways. This article is part of the theme issue ‘The marine system of the west Antarctic Peninsula: status and strategy for progress in a region of rapid change’.

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Decline in plankton diversity and carbon flux with reduced sea ice extent along the Western Antarctic Peninsula

Nature Communications ◽

10.1038/s41467-021-25235-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yajuan Lin ◽

Carly Moreno ◽

Adrian Marchetti ◽

Hugh Ducklow ◽

Oscar Schofield ◽

...

Keyword(s):

Sea Ice ◽

Carbon Cycling ◽

Antarctic Peninsula ◽

Dominant Factor ◽

Western Antarctic Peninsula ◽

Net Community Production ◽

Sea Ice Extent ◽

Plankton Diversity ◽

Mixed Layers ◽

Community Production

AbstractSince the middle of the past century, the Western Antarctic Peninsula has warmed rapidly with a significant loss of sea ice but the impacts on plankton biodiversity and carbon cycling remain an open question. Here, using a 5-year dataset of eukaryotic plankton DNA metabarcoding, we assess changes in biodiversity and net community production in this region. Our results show that sea-ice extent is a dominant factor influencing eukaryotic plankton community composition, biodiversity, and net community production. Species richness and evenness decline with an increase in sea surface temperature (SST). In regions with low SST and shallow mixed layers, the community was dominated by a diverse assemblage of diatoms and dinoflagellates. Conversely, less diverse plankton assemblages were observed in waters with higher SST and/or deep mixed layers when sea ice extent was lower. A genetic programming machine-learning model explained up to 80% of the net community production variability at the Western Antarctic Peninsula. Among the biological explanatory variables, the sea-ice environment associated plankton assemblage is the best predictor of net community production. We conclude that eukaryotic plankton diversity and carbon cycling at the Western Antarctic Peninsula are strongly linked to sea-ice conditions.

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Specific eukaryotic plankton are good predictors of net community production in the Western Antarctic Peninsula

Scientific Reports ◽

10.1038/s41598-017-14109-1 ◽

2017 ◽

Vol 7 (1) ◽

Cited By ~ 7

Author(s):

Yajuan Lin ◽

Nicolas Cassar ◽

Adrian Marchetti ◽

Carly Moreno ◽

Hugh Ducklow ◽

...

Keyword(s):

Antarctic Peninsula ◽

Western Antarctic Peninsula ◽

Net Community Production ◽

Community Production

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Interannual variability in net community production at the Western Antarctic Peninsula region (1997–2014)

Journal of Geophysical Research Oceans ◽

10.1002/2015jc011378 ◽

2016 ◽

Vol 121 (7) ◽

pp. 4748-4762 ◽

Cited By ~ 9

Author(s):

Zuchuan Li ◽

Nicolas Cassar ◽

Kuan Huang ◽

Hugh Ducklow ◽

Oscar Schofield

Keyword(s):

Interannual Variability ◽

Antarctic Peninsula ◽

Western Antarctic Peninsula ◽

Net Community Production ◽

Community Production

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Holocene climate variations in the western Antarctic Peninsula: evidence for sea ice extent predominantly controlled by changes in insolation and ENSO variability

Climate of the Past ◽

10.5194/cp-9-1431-2013 ◽

2013 ◽

Vol 9 (4) ◽

pp. 1431-1446 ◽

Cited By ~ 47

Author(s):

J. Etourneau ◽

L. G. Collins ◽

V. Willmott ◽

J.-H. Kim ◽

L. Barbara ◽

...

Keyword(s):

Sea Ice ◽

Water Column ◽

Antarctic Peninsula ◽

Primary Productivity ◽

Climatic Factors ◽

Southern Oscillation ◽

Western Antarctic Peninsula ◽

Deep Basin ◽

Sea Ice Extent ◽

Ice Conditions

Abstract. The West Antarctic ice sheet is particularly sensitive to global warming and its evolution and impact on global climate over the next few decades remains difficult to predict. In this context, investigating past sea ice conditions around Antarctica is of primary importance. Here, we document changes in sea ice presence, upper water column temperatures (0–200 m) and primary productivity over the last 9000 yr BP (before present) in the western Antarctic Peninsula (WAP) margin from a sedimentary core collected in the Palmer Deep Basin. Employing a multi-proxy approach, based on the combination of two biomarkers proxies (highly branched isoprenoid (HBI) alkenes for sea ice and TEX86L for temperature) and micropaleontological data (diatom assemblages), we derived new Holocene records of sea ice conditions and upper water column temperatures. The early Holocene (9000–7000 yr BP) was characterized by a cooling phase with a short sea ice season. During the mid-Holocene (~7000–3800 yr BP), local climate evolved towards slightly colder conditions and a prominent extension of the sea ice season occurred, promoting a favorable environment for intensive diatom growth. The late Holocene (the last ~2100 yr) was characterized by warmer temperatures and increased sea ice presence, accompanied by reduced local primary productivity, likely in response to a shorter growing season compared to the early or mid-Holocene. The gradual increase in annual sea ice duration over the last 7000 yr might have been influenced by decreasing mean annual and spring insolation, despite increasing summer insolation. We postulate that, in addition to precessional changes in insolation, seasonal variability, via changes in the strength of the circumpolar Westerlies and upwelling activity, was further amplified by the increasing frequency/amplitude of the El Niño–Southern Oscillation (ENSO). However, between 3800 and 2100 yr BP, the lack of correlation between ENSO and climate variability in the WAP suggests that other climatic factors might have been more important in controlling WAP climate at this time.

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Holocene climate variations in the western Antarctic Peninsula: evidence for sea ice extent predominantly controlled by insolation and ENSO variability changes

Climate of the Past Discussions ◽

10.5194/cpd-9-1-2013 ◽

2013 ◽

Vol 9 (1) ◽

pp. 1-41 ◽

Cited By ~ 3

Author(s):

J. Etourneau ◽

L. G. Collins ◽

V. Willmott ◽

J. H. Kim ◽

L. Barbara ◽

...

Keyword(s):

Sea Ice ◽

Water Column ◽

Antarctic Peninsula ◽

Primary Productivity ◽

Climatic Factors ◽

Southern Oscillation ◽

Western Antarctic Peninsula ◽

Deep Basin ◽

Sea Ice Extent ◽

Ice Conditions

Abstract. The West Antarctic ice sheet is particularly sensitive to global warming and its evolution and impact on global climate over the next few decades remains difficult to predict. In this context, investigating past sea ice conditions around Antarctica is of primary importance. Here, we document changes in sea ice presence, upper water column temperatures (0–200 m) and primary productivity over the last 9000 yr BP (before present) in the western Antarctic Peninsula (WAP) margin from a sedimentary core collected in the Palmer Deep basin. Employing a multi-proxy approach, we derived new Holocene records of sea ice conditions and upper water column temperatures, based on the combination of two biomarkers proxies (highly branched isoprenoid (HBI) alkenes for sea ice and TEXL86 for temperature) and micropaleontological data (diatom assemblages). The early Holocene (9000–7000 yr BP) was characterized by a cooling phase with a short sea ice season. During the mid-Holocene (~ 7000–3000 yr BP), local climate evolved towards slightly colder conditions and a prominent extension of the sea ice season occurred, promoting a favorable environment for intensive diatom growth. The late Holocene (the last ~ 3000 yr) was characterized by more variable temperatures and increased sea ice presence, accompanied by reduced local primary productivity likely in response to a shorter growing season compared to the early or mid-Holocene. The stepwise increase in annual sea ice duration over the last 7000 yr might have been influenced by decreasing mean annual and spring insolation despite an increasing summer insolation. We postulate that in addition to precessional changes in insolation, seasonal variability, via changes in the strength of the circumpolar Westerlies and upwelling activity, was further amplified by the increasing frequency/amplitude of El Niño-Southern Oscillation (ENSO). However, between 4000 and 2100 yr BP, the lack of correlation between ENSO and climate variability in the WAP suggests that other climatic factors might have been more important in controlling WAP climate at this time.

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Ice melt influence on summertime net community production along the Western Antarctic Peninsula

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/j.dsr2.2016.07.016 ◽

2017 ◽

Vol 139 ◽

pp. 89-102 ◽

Cited By ~ 20

Author(s):

R. Eveleth ◽

N. Cassar ◽

R.M. Sherrell ◽

H. Ducklow ◽

M.P. Meredith ◽

...

Keyword(s):

Antarctic Peninsula ◽

Western Antarctic Peninsula ◽

Net Community Production ◽

Ice Melt ◽

Community Production

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Bacteria-algae relationships in Antarctic sea ice

Antarctic Science ◽

10.1017/s0954102004001889 ◽

2004 ◽

Vol 16 (2) ◽

pp. 143-156 ◽

Cited By ~ 31

Author(s):

F.J. STEWART ◽

C.H. FRITSEN

Keyword(s):

Sea Ice ◽

Water Column ◽

Antarctic Peninsula ◽

Algal Biomass ◽

Ross Sea ◽

Radiant Energy ◽

Bacterial Biomass ◽

Weddell Sea ◽

Western Antarctic Peninsula ◽

Antarctic Sea Ice

Energy transfer in microbial food webs is partly quantified by the relationship between bacterial and algal biomass. Tight spatial relationships suggest active bacterial assimilation of dissolved photosynthate in temperate marine and fresh waters. However, studies in the Antarctic suggest that bacterial biomass generation from algal-derived dissolved organic matter is highly variable across seasons and habitats. Regression analysis was used to measure how bacteria covaried with algae in sea ice and water column habitats at three sites around Antarctica. Bacteria and algae were positively related in sea ice of the Weddell Sea during early winter 1992 (r2 = 0.16, slope = 0.24) and across sea ice and upper water column habitats of the Ross Sea during summer 1999 (r2 = 0.52, slope = 0.50). Conversely, bacteria and algae exhibited no discernible relationship in the water column and first year ice habitats of the Western Antarctic Peninsula region in winter 2001 (r2 = 0.003, slope = −0.04). Low algal production and residual biomass probably limited bacterial production and facilitated bacteria-algae uncoupling in winter sea ice of the Western Antarctic Peninsula. Winter sea ice algal biomass was probably limited by a relatively late date of initial ice formation, reduced multi-year ice coverage, and a lack of radiant energy in the winter ice pack.

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