The Marine System of the Western Antarctic Peninsula

Ducklow, Hugh W.; Clarke, Andrew; Dickhut, Rebecca M.; Doney, Scott C.; Geisz, Heidi N.; Huang, Kuan; Martinson, Douglas G.; Meredith, Michael P.; Moeller, Holly V.; Montes-Hugo, Martin; Schofield, Oscar; Stammerjohn, Sharon; Steinberg, Debbie; Fraser, William R.

doi:10.1002/9781444347241.ch5

Cited by 89 publications

(56 citation statements)

References 240 publications

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“…During period 1, the sea ice gradually melted and freshened the surface layer thereby reducing MLD and promoting diatom growth, as is typical for the traditional WAP ecosystem (Ducklow et al, 2012a(Ducklow et al, , 2013. Moreover, a strong increase of turbidity indicated the marked presence of non-photosynthetic material, presumably microalgal aggregates released from the bottom of the sea ice ( Figure 2B; Legge et al, 2017).…”

Section: Influence Of Presence/absence Of Sea Ice On Phytoplankton Dymentioning

confidence: 88%

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Assessing Drivers of Coastal Primary Production in Northern Marguerite Bay, Antarctica

Rozema

Kulk

Veldhuis³

et al. 2017

Front. Mar. Sci.

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The coastal ocean of the climatically-sensitive west Antarctic Peninsula is experiencing changes in the physical and (photo)chemical properties that strongly affect the phytoplankton. Consequently, a shift from diatoms, pivotal in the Antarctic food web, to more mobile and smaller flagellates has been observed. We seek to identify the main drivers behind primary production (PP) without any assumptions beforehand to obtain the best possible model of PP. We employed a combination of field measurements and modeling to discern and quantify the influences of variability in physical, (photo)chemical, and biological parameters on PP in northern Marguerite Bay. Field data of high-temporal resolution (November 2013-March 2014) collected at a long-term monitoring site here were combined with estimates of PP derived from photosynthesis-irradiance incubations and modeled using mechanistic and statistical models. Daily PP varied greatly and averaged 1,764 mg C m −2 d −1 with a maximum of 6,908 mg C m −2 d −1 after the melting of sea ice and the likely release of diatoms concentrated therein. A non-assumptive random forest model (RF) with all possibly relevant parameters (M RFmax ) showed that variability in PP was best explained by light availability and chlorophyll a followed by physical (temperature, mixed layer depth, and salinity) and chemical (phosphate, total nitrogen, and silicate) water column properties. The predictive power from the relative abundances of diatoms, cryptophytes, and haptophytes (as determined by pigment fingerprinting) to PP was minimal. However, the variability in PP due to changes in species composition was most likely underestimated due to the contrasting strategies of these phytoplankton groups as we observed significant negative relations between PP and the relative abundance of flagellates groups. Our reduced model (M RFmin ) showed how light availability, chlorophyll a, and total nitrogen concentrations can be used to obtain the best estimate of PP (R 2 = 0.93). The resulting estimates from our models suggest summer PP to have been between 214.4 and 176.1 g C m −2 . Through the employment of a modeling technique without any assumptions apart from a representative sampling strategy, we showed and estimated how PP in this climatically sensitive and changing region can best be predicted and described.

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Section: Influence Of Presence/absence Of Sea Ice On Phytoplankton Dymentioning

confidence: 88%

“…The classical Antarctic food web revolves around highly productive sea ice edge blooms consisting of diatoms, where krill can feed and transfer energy up the food chain (reviewed in Ducklow et al, 2012a). These blooms are instigated by the melting of sea ice and increase in light availability after the polar winter.…”

Section: Introductionmentioning

confidence: 99%

Assessing Drivers of Coastal Primary Production in Northern Marguerite Bay, Antarctica

Rozema

Kulk

Veldhuis³

et al. 2017

Front. Mar. Sci.

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“…However, their contribution to the vertical flux of biogenic carbon is higher than that of krill (Pakhomov et al, 2002;Pakhomov, 2004;Tanimura et al, 2008), with higher ingestion rates and the egestion of larger, faster sinking fecal pellets (Pakhomov et al, 2006;Ducklow et al, 2012). Regarding the smaller size fractions of mesozooplankton (Copepods and furcilia) their role in Antarctic food webs is complex.…”

Section: Wwwfrontiersinorgmentioning

confidence: 99%

Changes in the C, N, and P cycles by the predicted salps-krill shift in the southern ocean

et al. 2014

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The metabolic carbon requirements and excretion rates of three major zooplankton groups in the Southern Ocean were studied in February 2009. The research was conducted in the framework of the ATOS research project as part of the Spanish contribution to the International Polar Year. The objective was to ascertain the possible consequences of the predicted zooplankton shift from krill to salps in the Southern Ocean for the cycling of biogenic carbon and the concentration and stoichiometry of dissolved inorganic nutrients. The carbon respiratory demands and NH4-N and PO4-P excretion rates of <5 mm size copepods, krill and salps were estimated by incubation experiments. The carbon-specific metabolic rates and N:P metabolic quotients of salps were higher than those of krill (furcilia spp. and adults) and copepods, and as expected there was a significant negative relation between average individual zooplankton biomass and their metabolic rates, each metabolic process showing a particular response that lead to different metabolic N:P ratios. The predicted change from krill to salps in the Southern Ocean would encompass not only the substitution of a pivotal group for Antarctic food webs (krill) by one with an indifferent trophic role (salps). In a zooplankton community dominated by salps the respiratory carbon demand by zooplankton will significantly increase, and therefore the proportion of primary production that should be allocated to compensate for the global respiratory C-losses of zooplankton. At the same time, the higher production by salps of larger, faster sinking fecal pellets will increase the sequestration rate of biogenic carbon. Similarly, the higher N and P excretion rates of zooplankton and the changes in the N:P stoichiometry of the metabolic products will modify the concentration and proportion of N and P in the nutrient pool, inducing quantitative and qualitative changes on primary producers that will translate to the whole Southern Ocean ecosystem.

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“…Compared to krill or copepods (Pakhomov et al, 2006;Ducklow et al, 2012), it has been suggested that salps strongly contribute to the vertical flux of biogenic carbon due to their production of large, fast sinking fecal pellets (FPs; Pakhomov et al, 2002). Sinking velocity is an important parameter since it will determine the residence time during which the FPs will be subjected in the mixed layer to physicochemical recycling processes such as photo-degradation, before being exported and undergoing further microbial decomposition and coprophagy (Turner, 2002;Rontani, 2008;Pisani et al, 2011;Giering et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

First Evaluation of the Role of Salp Fecal Pellets on Iron Biogeochemistry

et al. 2017

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Planktonic grazers such as salps may have a dominant role in iron (Fe) cycling in surface waters of the Southern Ocean (SO). Salps have high ingestion rates and egest large, fast sinking fecal pellets (FPs) that potentially contribute to the vertical flux of carbon. In this study, we determined the impact of FPs from Salpa thompsoni, the most abundant salp in the SO, on Fe biogeochemistry. During the Polarstern expedition ANT-XXVII/3, salps were sampled from a large diatom bloom area in the Atlantic sector of the SO. Extensive work on carbon export and salp FPs export at the sampling location had shown that salps were a minor component of zooplankton and were responsible for only a 0.2% consumption of the daily primary production. Furthermore, at 100 m, export efficiency of salp FPs was ∼2-3 fold higher than that of the bulk of sinking particulate organic carbon (POC). After collection, salps were maintained in 200 µm screened seawater and their FPs were collected for further experiments. To investigate whether the FPs release Fe and/or Fe-binding ligands into the filtered seawater (FSW) under different experimental conditions, they were either incubated in the dark or under full sunlight at in situ temperatures for 24 h, or placed into the dark after a freeze/thaw treatment. We observed that none of the treatments caused release of dissolved Fe (dFe) or strong Fe ligands from the salp FPs. However, humic-substance like (HS-like) compounds, weak Fe ligands, were released at a rate of 8.2 ± 4.7 µg HS-like FP −1 d −1 . Although the Fe content per salp FP was high at 0.33 −1 ± 0.02 nmol dFe FP , the small contribution of salps to the zooplankton pool resulted in an estimated dFe export flux of 11.3 nmol Fe m −2 d −1 at 300 m. Since salp FPs showed an export efficiency at 100 m well above that shown by the bulk of sinking POC, our results suggest that in those areas of the SO where salps play a major role in the grazing of primary production, they could be actively contributing to the depletion of the dFe pool in surface water.

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The Marine System of the Western Antarctic Peninsula

Cited by 89 publications

References 240 publications

Assessing Drivers of Coastal Primary Production in Northern Marguerite Bay, Antarctica

Assessing Drivers of Coastal Primary Production in Northern Marguerite Bay, Antarctica

Changes in the C, N, and P cycles by the predicted salps-krill shift in the southern ocean

First Evaluation of the Role of Salp Fecal Pellets on Iron Biogeochemistry

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