Carbon and nitrogen content to biovolume relationships for marine protist of the Rhizaria lineage (Radiolaria and Phaeodaria)

Abstract

Rhizaria are large protistan cells that have been shown to be a major component of the planktic community in the oceans and contribute significantly to major biogeochemical cycles such as carbon or silicon. However, unlike for many other protists, limited data is available on rhizarian cellular carbon (C) and nitrogen (N) content and cell volume. Here we present novel C and N mass to volume equations and ratios for nine Rhizaria taxa belonging to Radiolaria (i.e., Collozoum, Sphaerozoum, Collosphaeridae, Acantharia, Nassellaria, and Spumellaria) and Phaeodaria (i.e., Aulacantha, Protocystis, and Challengeria). The C and N content of collodarian cells was significantly correlated to cell volume as expressed by the mass : vol equations ng C cell −1 = −13.51 + 0.1524 × biovolume (μm 3) or ng N cell −1 = −4.33 + 0.0249 × biovolume (μm 3). Significant C and N content to volume correlations were also identified, and corresponding equations are proposed, for C : vol and N : vol of collodarian colonies (Radiolaria), and C : vol of the genus Protocystis (Phaeodaria). Furthermore, average C and N densities (mass per volume) are given for all studied Rhizaria. The densities and mass : vol equations established here could show that, with the exception of Aulacantha, biomass of most Rhizaria would have been underestimated using previously published generic protist C : vol ratios. We measured up to 35 times more C content for Acantharia than otherwise estimated, and between 1.4 and 21.5 times more for other taxa. Our mass : vol data will prove critical for model input and quantitative ecological studies of oceanic ecosystems. Rhizaria are single-celled eukaryotes (i.e., protists) that are a key component of planktic communities in the ocean (Not et al. 2007;

Global Distribution of Zooplankton Biomass Estimated by In Situ Imaging and Machine Learning

“…This choice was done based on the fact that solitary Collodaria are smaller than colonial ones and have a different vertical distribution (Faillettaz et al, 2016). For solitary collodarians with a dark central capsule (subgroup of solitary Collodaria) described in Biard et al (2016), the estimation of carbon (0.189 mgC mm -3 ) by Mansour et al, (2021) was done on the capsule of the organisms. As Zooprocess measures the area of the whole organism, we determined the ratio area whole organism area central capsule = 0:713 and applied this factor to avoid overestimation of carbon biomass for this group.…”

“…As Zooprocess measures the area of the whole organism, we determined the ratio area whole organism area central capsule = 0:713 and applied this factor to avoid overestimation of carbon biomass for this group. For the rest of the collodarians, the estimation of Mansour et al, (2021) was directly applied.…”

Planktonic protist diversity across contrasting Subtropical and Subantarctic waters of the southwest Pacific

“…The high copy number of 18S rDNA in Radiolaria may contribute to their high relative abundance metabarcode datasets ((Gutierrez-Rodriguez et al 2019;Vargas et al 2015)); however, it is unlikely to be responsible for their dominance, particularly in relation to dinoflagellates and ciliates, which are also known to have high copy numbers (Gong et al 2013;Piredda et al 2017). Moreover, the positive relationship between cell length and 18S rDNA copy number (Biard et al 2017;Zhu et al 2005) and the higher C and N density (mass: volume) of Radiolaria compared to other protist (Mansour et al 2021) suggest that gene-based relative abundance of these groups was likely reflected in their relative contribution to the community biomass.…”

Elemental content allometries and silicon uptake rates of planktonic Rhizaria: Insights into their ecology and role in biogeochemical cycles

“…From the pictures, we measured the length of major and minor axes using ImageJ software (Abràmoff et al 2004). Volumes (V) were estimated by approximating the shape and size of each taxon using simple geometric shapes that allowed calculation of the associated volume (Mansour et al 2021; Supporting Information Fig. S1; Table S2).…”

“…Along with 103 samples available from the literature (Mansour et al 2021; Table 1), we tested for the relationship between elemental composition and cell size using ordinary least-square regressions of log 10 -transformed C or N content on log 10 -transformed cell volume for a total of 256 samples for C and 235 for N. For both elements, we found a significant relationship (R 2 = 0.76, p-value < 0.0001, RMSE = 0.40 for C; R 2 = 0.78, p-value < 0.0001, RMSE = 0.41 for N), described by the equations:…”