Light Absorption by Suspended Particles in the Red Sea: Effect of Phytoplankton Community Size Structure and Pigment Composition

Kheireddine, Malika; Ouhssain, Mustapha; Organelli, Emanuele; Bricaud, Annick; Jones, Burton H.

doi:10.1002/2017jc013279

Cited by 23 publications

(27 citation statements)

References 128 publications

(273 reference statements)

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“…significantly higher than those predicted by the model of Morel and Maritorena (2001) at any given [Chl_a] concentration. This may be due to a higher contribution of non-algal particles or small particles in the Red Sea, relative to other open-ocean environments (Kheireddine et al, 2018). We also found, as reported in previous studies (Twardowski et al, 2001;Whitmire et al, 2007) (up to 20%, Whitmire et al, 2007).…”

Section: Resultssupporting

confidence: 89%

Particulate Scattering and Backscattering in Relation to the Nature of Particles in the Red Sea

et al. 2021

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The ocean contains a large variety of suspended particles that cover a broad size range, from 0.1 nm to 1 mm, and vary in origin (i.e., biogenic or terrestrial), shape and internal composition (i.e., refractive index; Stramski et al., 2004). The pool of suspended particles is often divided into non-algal particles and phytoplankton. Non-algal particles include: (1) heterotrophs (i.e., bacteria, viruses and zooplankton), (2) non-living organic detritus produced by zoo-and phyto-plankton (i.e., fecal pellets, dead cells), and (3) mineral particles (e.g., silicate shells, dusts, clay, etc.). The phytoplankton pool is often divided according to cell size (Sieburth et al., 1978), into pico-phytoplankton (0.2-2 µm), nano-phytoplankton (2-20 µm) and micro-phytoplankton

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Section: Resultssupporting

confidence: 89%

Particulate Scattering and Backscattering in Relation to the Nature of Particles in the Red Sea

et al. 2021

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“…exceeding 5-10 mg m -3 ) than those in our data set (our maximum Chl a_tot was 2.4 mg m -3 ); as discussed above, for a given amount of scatter of the dependent variable, the value of the correlation increases with increasing variability among the observations of the independent variable (Goodwin and Leech 2006). On the other hand, our outcomes are in line with those of other studies where, in addition to the major contribution of size structure, either changes in intracellular pigment concentration or variations in pigment composition were also found to be important factors shaping a ph *(443) (Brunelle et al 2012, Ferreira et al 2017, Kheireddine et al 2018; it can be noted also that these works used a Chl a concentration range rarely exceeding 5 mg m -3 .…”

Section: Variability Of Cdom and Phytoplankton Absorptionsupporting

confidence: 91%

Size fractionation, chemotaxonomic groups and bio-optical properties of phytoplankton along a transect from the Mediterranean Sea to the SW Atlantic Ocean

Nunes¹,

Pérez²,

Latasa³

et al. 2019

Sci. Mar.

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The relationships between the structure of the phytoplankton community and the bio-optical properties of surface waters were studied during the TransPEGASO cruise along a transect across the Atlantic Ocean that covered seven biogeographical provinces, from the Alborán Sea (SW Mediterranean) to the Patagonian Shelf. We characterized the composition of the phytoplankton community by means of high-performance liquid chromatography and CHEMTAX pigment analyses applied to whole water and two filtration size classes (< 3 and ≥ 3 μm), flow cytometric determinations and microscopic observations. Additionally, the study was complemented by measurements of the absorption of particulate matter and coloured dissolved organic matter (CDOM). The size class distribution of the chlorophyll a (Chl a) obtained from the size-fractionated filtration (SFF) was compared with that resulting from the diagnostic pigment algorithms (VU) developed by Vidussi et al. (2001) and Uitz et al. (2006), and the total Chl a–based expressions (HI) of Hirata et al. (2011). The seven provinces crossed by the transect could be divided into an oligotrophic group with Chl a < 0.25 mg m-3 comprising the tropical and subtropical Atlantic (including the Canary Current Coastal Province), and a eutrophic group (Chl a > 0.5 mg m-3) with a single Mediterranean (MEDI) sample and those from the southwestern Atlantic Shelf (SWAS). According to CHEMTAX, the most important taxa in the tropical and subtropical Atlantic were Prochlorococcus, haptophytes and Synechoccoccus, while the MEDI and SWAS were dominated by diatoms and haptophytes. Both the VU and HI algorithms, which are based on pigment composition or Chl a concentration, predicted for SWAS a high proportion of nano- and microphytoplankton, while the SFF indicated dominance of the < 3 μm size class. In addition, the CHEMTAX results indicated a high average diatom contribution in this province. However, at several SWAS stations with relatively high values of diatom Chl a estimated by CHEMTAX, the microscopic observations found only small concentrations of nano- or microplankton-sized cells. This discrepancy appeared to be due to the presence, confirmed by scanning electron microscopy, of picoplankton-sized cells of the diatom Minidiscus sp. and of Parmales (a group sharing the pigment composition with the diatoms). These findings caution against a routine assignment of diatom pigments to the microplankton size class. The total non-water absorption in the water column was dominated by CDOM. The average contribution of phytoplankton absorption for the different provinces ranged from 19.3% in the MEDI to 45.7% in the SWAS and 47% in the western tropical Atlantic (WTRA). The Chl a–specific phytoplankton absorption [aph*(443), m2 mg-1] was lower in the MEDI and SWAS than in the oligotrophic provinces. aph*(443) was negatively correlated with the first principal component derived from a principal component analysis based on the concentration of the main pigments and was not correlated with indicators of phytoplankton community size structure such as the proportion of Chl a in the < 3 μm class or a size index derived from the VU size class distribution. These findings indicate that the variability observed in aph*(443) was mainly related to differences in pigment composition and possibly to photoacclimation processes, and that any package effects due to cell size were probably masked by other factors, an outcome that may be related to the relatively small influence of size within the narrow range of Chl a concentrations (all ≤ 2.4 mg m-3) considered in our study.

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“…Besides and as aforementioned, the SI index was originally developed for the surface layer and can be used here only as a rough indicator of the phytoplankton dominant size in the three evaluated layers. Even though, it has been previously used in different studies either in the SML or below this layer (Kheireddine et al, 2018;Organelli et al, 2011;Wang et al, 2014). Is encouraging, however, the agreement between our observations (DPA, light microscopy counts and cytometry determinations), as well as with the previously mentioned works and other studies conducted in the NWMS (see Bricaud et al, 2004;Organelli et al, 2013).…”

Section: Phytoplankton Pigments Community Composition and Size Structuresupporting

confidence: 91%

Variability of phytoplankton light absorption in stratified waters of the NW Mediterranean Sea: The interplay between pigment composition and the packaging effect

Pérez¹,

Galí²,

Royer³

et al. 2021

Deep Sea Research Part I: Oceanographic Research Papers

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The Variability of chlorophyll-specific phytoplankton light absorption [a*ph (l)] was examined over depth and time in stratified offshore waters of the North-Western Mediterranean Sea. Coherent water patches were tracked with Lagrangian drifters during two oceanographic cruises in September (late summer) and May (post-spring bloom phase). By simultaneously analysing the phytoplankton absorption and pigment measurements, we explicitly separated the impact of pigment composition from that of pigment packaging on a*ph (l). We further partitioned the packaging effect by comparing the variation of the packaging index [Qa*(440)], the phytoplankton community size structure (derived from diagnostic pigment analysis), and the chlorophyll-specific beam attenuation by particles [cp* (660)] as an optical index of phytoplankton photophysiology. In the ensemble of cruises, around 50% of the a*ph (440) vertical variation was explained by changes in the pigment composition (ruled by the decrease of photoprotective pigments with depth). The remaining vertical and inter-cruise variation of a*ph (440) was attributed to the packaging effect. We found that differences in the cp*(660) index (most likely indicating changes in the intracellular pigment concentration due to photoacclimation) mainly explained the observed variation in the packaging effect. Differences in cp* (660) were coincident with either the vertical gradient of light availability or the lower mean daily PAR irradiance in the euphotic layer of the September cruise. These explained the stronger packaging and lower a*ph (440) values observed with increasing depth in both cruises, and in September relative to May. On the other hand, differences in the phytoplankton community size structure did not explain the observed patterns in the packing effect. Our results highlight the importance of phytoplankton short-term acclimation to the prevailing light conditions, determining the vertical and temporal variability of a*ph (l). A better understanding of the a*ph (l) variability and its main drivers are key to improve different bio-optical applications. Manuscript FileClick here to view linked References

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Light Absorption by Suspended Particles in the Red Sea: Effect of Phytoplankton Community Size Structure and Pigment Composition

Cited by 23 publications

References 128 publications

Particulate Scattering and Backscattering in Relation to the Nature of Particles in the Red Sea

Particulate Scattering and Backscattering in Relation to the Nature of Particles in the Red Sea

Size fractionation, chemotaxonomic groups and bio-optical properties of phytoplankton along a transect from the Mediterranean Sea to the SW Atlantic Ocean

Variability of phytoplankton light absorption in stratified waters of the NW Mediterranean Sea: The interplay between pigment composition and the packaging effect

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