Phosphorus limitation affects the molecular composition of Thalassiosira weissflogii leading to increased biogenic silica dissolution and high degradation rates of cellular carbohydrates
|Author(s)||Panagiotopoulos Christos1, Goutx Madeleine1, Suroy Maxime1, Moriceau Brivaela2|
|Affiliation(s)||1 : Aix Marseille Univ., Université de Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France
2 : Université de Brest, Institut Universitaire Européen de la Mer (IUEM), CNRS, Laboratoire des Sciences de l’Environnement Marin, UMR 6539 CNRS/UBO/IFREMER/IRD, 29280 Plouzané, France
|Source||Organic Geochemistry (0146-6380) (Elsevier BV), 2020-10 , Vol. 148 , P. 104068 (11p.)|
|Keyword(s)||Bacterial biodegradation, Thalassiosira weissflogii, P-stress, POC, PON, Carbohydrates, Biogenic silica|
Diatoms in general, and Thalassiosira weissflogii (T. weissflogii) in particular, are among the most ubiquitous phytoplanktonic species while, phosphorus (P) is an essential nutrient that limits productivity in many oceanic regimes. To investigate how T. weissflogii cultures grown under different P regimes are chemically altered before and during their prokaryotic degradation, T. weissflogii cells were cultivated under two
contrasting P conditions, “P-stress” and “P-replete”. Biodegradation experiments were conducted in natural sea water comprising a natural prokaryotic community. The particulate fraction was monitored for 3 weeks for organic carbon (POC), nitrogen (PON), biogenic silica (bSiO2), total carbohydrates (PCHO) and individual monosaccharides, including prokaryotic counting. Our results indicated that P-stress induced changes in the chemical composition of the T. weissflogii cells, causing a decrease to the Si/N (1.1 to 0.46) and Si/C (0.17 to 0.08) ratios. The “P-stress T. weissflogii” cells were characterized by high amounts of galactose (23% of PCHO), xylose (21%), and glucose (19%) compared to the “P-replete T. weissflogii” cells, which were dominated by ribose (20% of PCHO), further indicating the exhaustion of ribose-rich molecules (e.g., ATP) in T. weissflogii under “P-stress” conditions. The degradation experiments showed that bSiO2 produced under “P-stress” conditions dissolved more rapidly than bSiO2 formed under “P-replete” conditions, whereas POC and PON exhibited higher degradation rate constants in the “P-replete T. weissflogii” than in the “P-stress T. weissflogii” experiment. Overall, these observations show that T. weissflogii submitted to P-limitation, results in changes in its initial biochemical composition, increases frustule dissolution rate, and decreases the degradation of T. weissflogii-organic matter by marine prokaryotes.