Preprints
https://doi.org/10.5194/bg-2022-233
https://doi.org/10.5194/bg-2022-233
12 Dec 2022
 | 12 Dec 2022
Status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Variability of light absorption coefficients by different size fractions of suspensions in the southern Baltic Sea

Justyna Meler, Dagmara Litwicka, and Monika Zabłocka

Abstract. Measurements of light absorption coefficients by particles suspended in seawater (ap (λ)), by phytoplankton (aph(λ)) and detritus (ad (λ)) were carried out in the Baltic Sea waters. Measurements were performed for the original (unfiltered) seawater samples and the four selected size fractions: pico-particles with diameters (0.2–2 μm), ultra-particles with diameters (2–5 μm), nano-particles with diameters (5–20 μm) and micro-particles (20–200 μm). Chlorophyll a  (Chla) concentrations and total suspended particulate matter (SPM) concentrations were determined. The proportions of particles from the size classes (micro, nano, ultra and pico) in the total light absorption by particles, phytoplankton and detritus were determined. Particles with sizes < 5 μm (i.e. pico and ultra-particles) had the largest contribution to the total particles absorption – an average of 38 % and 31 %. Particles of 5–20 μm accounted for approximately 20 % of all particles and phytoplankton and 29 % of the detritus. The contribution of large particles > 20 µm averaged 5–10 %.

The average chlorophyll-specific and mass-specific light absorption coefficients, i.e. light absorption coefficients normalized to Chla and to SPM concentration, were determined for all size fractions. The determined average chlorophyll-specific light absorption coefficients ap(Chla)(λ), ad(Chla)(λ) and aph(Chla)(λ), along with standard deviations, do not allow clear separation of the individual fractions. For mass-specific light absorption coefficients, ap(SPM)(λ), ad(SPM)(λ) and aph(SPM)(λ), it is possible to distinguish between large particle fractions (microplankton – 20–200 μm) and small and medium particle fractions (0.2–20 μm).

Justyna Meler et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-233', Anonymous Referee #1, 02 Feb 2023
    • AC1: 'Reply on RC1', Justyna Meler, 07 Mar 2023
  • RC2: 'Comment on bg-2022-233', Anonymous Referee #2, 08 Feb 2023
    • AC2: 'Reply on RC2', Justyna Meler, 07 Mar 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-233', Anonymous Referee #1, 02 Feb 2023
    • AC1: 'Reply on RC1', Justyna Meler, 07 Mar 2023
  • RC2: 'Comment on bg-2022-233', Anonymous Referee #2, 08 Feb 2023
    • AC2: 'Reply on RC2', Justyna Meler, 07 Mar 2023

Justyna Meler et al.

Justyna Meler et al.

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Short summary
We present a variability of absorption properties by different size fractions of particles suspended in the Baltic Sea waters. The light absorption coefficient by all suspended particles (ap) and, by detritus (ad) and phytoplankton (aph) was determined for 4 size fractions: pico-particles, ultra-particles, nano-particles, and micro-particles. We have showed the proportions of particles from the size classes (micro, nano, ultra and pico) in the total ap, ad, and aph.
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