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Phytoplankton composition derived from CHEMTAX along 10°E during POLARSTERN cruise ANT-XXVIII/3, Jan-March 2012 (2016)

Cheah, Wee ; Soppa, Mariana A ; Wiegmann, Sonja ; [et al.]

PANGAEA

In: Supplement to: Cheah, Wee; Soppa, Mariana A; Wiegmann, Sonja; Ossebaar, Sharyn; Laglera, Luis Miguel; Strass, Volker H; Santos-Echeandía, Juan; Hoppema, Mario; Wolf-Gladrow, Dieter A; Bracher, Astrid (2016): Importance of deep mixing and silicic acid in regulating phytoplankton biomass and community in the iron-limited Antarctic Polar Front region in summer. Deep Sea Research Part II: Topical Studies in Oceanography, 12 pp, https://doi.org/10.1016/j.dsr2.2016.05.019

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Publication Date: 2024-06-26

Description: Phytoplankton community structure and their physiological response in the vicinity of the Antarctic Polar Front (APF; 44°S to 53°S, centred at 10°E) were investigated as part of the ANT-XXVIII/3 Eddy-Pump cruise conducted in austral summer 2012. Our results show that under iron-limited (〈 0.3 µmol/m**3) conditions, high total chlorophyll-a (TChl-a) concentrations (〉 0.6 mg/m**3) can be observed at stations with deep mixed layer (〉 60 m) across the APF. In contrast, light was excessive at stations with shallower mixed layer and phytoplankton were producing higher amounts of photoprotective pigments, diadinoxanthin (DD) and diatoxanthin (DT), at the expense of TChl-a, resulting in higher ratios of (DD+DT)/ TChl-a. North of the APF, significantly lower silicic acid (Si(OH)4) concentrations (〈 2 mmol/m**3) lead to the domination of nanophytoplankton consisting mostly of haptophytes, which produced higher ratios of (DD+DT)/TChl-a under relatively low irradiance conditions. The Si(OH)4 replete (〉 5 mmol/m**3) region south of the APF, on the contrary, was dominated by microphytoplankton (diatoms and dinoflagellates) with lower ratios of (DD+DT)/TChl-a, despite having been exposed to higher levels of irradiance. The significant correlation between nanophytoplankton and (DD+DT)/TChl-a indicates that differences in taxon-specific response to light are also influencing TChl-a concentration in the APF during summer. Our results reveal that provided mixing is deep and Si(OH)4 is replete, TChl-a concentrations higher than 0.6 mg/m**3 are achievable in the iron-limited APF waters during summer.

Keywords: ANT-XXVIII/3; CHEMTAX (Lewitus et al., 2005); Chlorophytes; Cryptophytes; CTD/Rosette; CTD-RO; Cyanobacteria; Date/Time of event; DEPTH, water; Diatoms; Dinoflagellates; Elevation of event; Event label; Haptophytes; In situ pump; ISP; Latitude of event; Longitude of event; Polarstern; Prasinophytes; PS79; PS79/057-4; PS79/060-5; PS79/061-1; PS79/062-1; PS79/063-2; PS79/064-1; PS79/065-1; PS79/066-1; PS79/068-1; PS79/069-4; PS79/070-3; PS79/073-2; PS79/074-1; PS79/075-9; PS79/076-2; PS79/077-1; PS79/078-1; PS79/079-1; PS79/080-1; PS79/081-11; PS79/081-5; PS79/082-1; PS79/083-1; PS79/084-9; South Atlantic Ocean

Type: Dataset

Format: text/tab-separated-values, 1090 data points

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Investigation of spectral band requirements for improving retrievals of phytoplankton functional types. (2016)

Wolanin, Aleksandra ; Soppa, Mariana A. ; Bracher, Astrid

MDPI

In: EPIC3Remote Sensing, MDPI, 8(871), pp. 1-21, ISSN: ISSN 2072-4292

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Publication Date: 2016-11-08

Description: Studying phytoplankton functional types (PFTs) from space is possible due to recent advances in remote sensing. Though a variety of products are available, the limited number of wavelengths available compared to the number of model parameters needed to be retrieved is still a major problem in using ocean-color data for PFT retrievals. Here, we investigated which band placement could improve retrievals of three particular PFTs (diatoms, coccolithophores and cyanobacteria). In addition to analyzing dominant spectral features in the absorption spectra of the target PFTs, two previously-developed methods using measured spectra were applied to simulated data. Such a synthetic dataset allowed for significantly increasing the number of scenarios and enabled a full control over parameters causing spectral changes. We evaluated the chosen band placement by applying an adapted ocean reflectance inversion, as utilized in the generalized inherent optical properties (GIOP) retrieval. Results show that the optimal band settings depend on the method applied to determine the bands placement, as well as on the internal variability of the dataset investigated. Therefore, continuous hyperspectral instruments would be most beneficial for discriminating multiple PFTs, though a small improvement in spectral sampling and resolution does not significantly modify the results. Bands, which could be added to future instruments (e.g., Ocean and Land Colour Instrument (OLCI) instrument on the upcoming Sentinel-3B,-3C,-3D, etc., and further satellites) in order to enhance PFT retrieval capabilities, were also determined.

Repository Name: EPIC Alfred Wegener Institut

Type: Article , isiRev

Format: application/pdf

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