Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity

Alderkamp, Anne‐Carlijn; Mills, Matthew M.; Dijken, Gert L. van; Laan, Patrick; Thuróczy, Charles-Edouard; Gerringa, Loes J. A.; Baar, H. J. W. de; Payne, Christopher D.; Visser, Ronald J. W.; Buma, Anita G. J.; Arrigo, Kevin R.

doi:10.1016/j.dsr2.2012.03.005

Cited by 129 publications

(128 citation statements)

References 83 publications

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“…In a similar way, the pattern of enhanced Chl-a in the northern sector of the BS demonstrated the coupling between water column structure and phytoplankton biomass: a shallow (deep) UMLD and high (low) Chl-a in the TBW (TWW). This type of association has been pointed out in other studies conducted within the BS and also at other sites across the Southern Ocean (Alderkamp et al, 2012;Castro et al, 2002;Hewes et al, 2009;Mura et al, 1995). Sangrà et al (2011) also demonstrated that sites within TWW influence presented deep UMLD or even a homogeneous water column with the lowest stability values.…”

Section: Phytoplankton and Environmental Factors: Spatial Variabilitymentioning

confidence: 60%

Influence of oceanographic features on spatial and interannual variability of phytoplankton in the Bransfield Strait, Antarctica

Gonçalves-Araujo

Souza

Tavano

et al. 2015

Journal of Marine Systems

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Section: Phytoplankton and Environmental Factors: Spatial Variabilitymentioning

confidence: 60%

Influence of oceanographic features on spatial and interannual variability of phytoplankton in the Bransfield Strait, Antarctica

Gonçalves-Araujo

Souza

Tavano

et al. 2015

Journal of Marine Systems

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“…Similarly, the meltwater-laden mCDW from the Pine Island Glacier was found to be a major source of DFe for the phytoplankton bloom in the PIP . These Fe sources support phytoplankton blooms with high biomass and productivity in both the PIP and ASP (Alderkamp et al, 2012a;Yager et al, 2012). Moreover, Fe addition bioassay experiments at the peak and during the decline of the phytoplankton bloom revealed that Fe was not limiting phytoplankton growth in either polynya at these times (Mills et al, 2012), suggesting relatively high Fe availability to the phytoplankton.…”

Section: Domain Editor-in-chiefmentioning

confidence: 93%

“…Conversely, basal ice shelf melt introduces meltwater-laden mCDW into the water column at the base of the ice shelf, at 150-400 m depth, depending both on the draft of the ice shelf Mankoff et al, 2012) and the degree of buoyancy driven upwelling. Introducing buoyant water at depth destabilizes the water column and may increase MLD and decrease light availability to the phytoplankton, as was observed at the face of the Pine Island ice shelf (Alderkamp et al, 2012a Phytoplankton photoacclimate to low light by increasing their cellular pigment concentration to maximize the capture of photons (Falkowski and LaRoche, 1991;MacIntyre et al, 2002). However, Fe availability affects photoacclimation because biosynthesis of pigments requires Fe and the photosynthetic apparatus has a high Fe content (Raven, 1990;Greene et al, 1992).…”

Section: Domain Editor-in-chiefmentioning

confidence: 99%

“…Phytoplankton productivity throughout the water column was estimated at each station from the Chl a concentrations, light availability in the water column, and P-E parameters, as described in Alderkamp et al (2012a). Briefly, at depth intervals of 1 m, Chl a concentrations were estimated from continuous vertical fluorescence profiles that were calibrated to the measured Chl a concentrations at similar depths (Chl a = 0.71 fluorescence; R 2 = 0.69).…”

Section: Water Column Productivitymentioning

confidence: 99%

“…The MLD was determined from each CTD profile as the shallowest depth at which the density (σ T ) was 0.02 kg m −3 greater than at the surface (Cisewski et al, 2008;Alderkamp et al, 2012a …”

Section: Mixed Layer Depth (Mld)mentioning

confidence: 99%

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Fe availability drives phytoplankton photosynthesis rates during spring bloom in the Amundsen Sea Polynya, Antarctica

Alderkamp

Dijken

Lowry

et al. 2015

Elementa: Science of the Anthropocene

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To evaluate what drives phytoplankton photosynthesis rates in the Amundsen Sea Polynya (ASP), Antarctica, during the spring bloom, we studied phytoplankton biomass, photosynthesis rates, and water column productivity during a bloom of Phaeocystis antarctica (Haptophyceae) and tested effects of iron (Fe) and light availability on these parameters in bioassay experiments in deck incubators. Phytoplankton biomass and productivity were highest (20 µg chlorophyll a L −1 and 6.5 g C m −2 d −1 ) in the central ASP where sea ice melt water and surface warming enhanced stratification, reducing mixed layer depth and increasing light availability. In contrast, maximum photosynthesis rate (P * max ), initial light-limited slope of the photosynthesis-irradiance curve (a *), and maximum photochemical efficiency of photosystem II (F v / F m ) were highest in the southern ASP near the potential Fe sources of the Dotson and Getz ice shelves. In the central ASP, P * max , a *, and F v / F m were all lower. Fe addition increased phytoplankton growth rates in three of twelve incubations, and at a significant level when all experiments were analyzed together, indicating Fe availability may be rate-limiting for phytoplankton growth in several regions of the ASP early in the season during build-up of the spring bloom. Moreover, Fe addition increased P * max , a*, and F v / F m in almost all experiments when compared to unamended controls. Incubation under high light also increased P * max , but decreased F v / F m and a * when compared to low light incubation. These results indicate that the lower values for P * max , a*, and F v / F m in the central ASP, compared to regions close to the ice shelves, are constrained by lower Fe availability rather than light availability. Our study suggests that higher Fe availability (e.g., from higher melt rates of ice shelves) would increase photosynthesis rates in the central ASP and potentially increase water column productivity 1.7-fold, making the ASP even more productive than it is today.

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Polynya dynamics drive primary production in the Larsen A and B embayments following ice shelf collapse

et al. 2014

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[1] The climate-driven collapses of the Larsen A and B ice shelves have opened up new regions of the coastal Antarctic to the influence of sea ice resulting in increases in seasonal primary production. In this study, passive microwave remote sensing of sea ice concentration and satellite imagery of ocean color are employed to quantify the magnitude of and variability in open water area and net primary productivity (NPP) in the Larsen embayments between 1997 and 2011. Numerical model output provides context to analyze atmospheric forcing on the coastal ocean. Following ice shelf disintegration the embayments function as coastal, sensible heat polynyas. The Larsen A and B are as productive as other Antarctic shelf regions, with seasonally averaged daily NPP rates reaching 1232 and 1127 mg C m 22 d 21 and annual rates reaching 200 and 184 g C m 22 yr 21 , respectively. A persistent cross-shelf gradient in NPP is present with higher productivity rates offshore, contrasting with patterns observed along the West Antarctic Peninsula. Embayment productivity is intimately tied to sea ice dynamics, with large interannual variability in NPP rates driven by open water area and the timing of embayment opening. Opening of the embayment is linked to periods of positive Southern Annular Mode and stronger westerlies, which lead to the vertical deflection of warm, maritime air over the peninsula and down the leeward side causing increases in surface air temperature and wind velocity. High productivity in these new polynyas is likely to have ramifications for organic matter export and marine ecosystem evolution.Citation: Cape, M. R., M. Vernet, M. Kahru, and G. Spreen (2014), Polynya dynamics drive primary production in the Larsen A and B embayments following ice-shelf collapse,

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Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity

Cited by 129 publications

References 83 publications

Influence of oceanographic features on spatial and interannual variability of phytoplankton in the Bransfield Strait, Antarctica

Influence of oceanographic features on spatial and interannual variability of phytoplankton in the Bransfield Strait, Antarctica

Fe availability drives phytoplankton photosynthesis rates during spring bloom in the Amundsen Sea Polynya, Antarctica

Polynya dynamics drive primary production in the Larsen A and B embayments following ice shelf collapse

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