Contributions of Transparent Exopolymer Particles by Specific Phytoplankton Groups in the Cosmonaut Sea, East Antarctic

Abstract. Transparent exopolymer particles (TEP) play a crucial role in marine carbon cycling. While phytoplankton are known to be the primary contributors to TEP, the impact of changes in phytoplankton community structure on TEP production in natural aquatic environments remains incompletely understood. This study employed multiple linear regression (MLR) modeling to quantify the contributions of two dominant phytoplankton groups, diatoms and haptophytes (primarily Phaeocystis antarctica), to TEP production in the surface waters of the Cosmonaut Sea, antarctica during the austral summer. Results demonstrate that in situ TEP production by each group can be estimated by scaling laboratory-derived theoretical values with an environmentally adjusted correction factor. These factors, primarily governed by phytoplankton community structure, reveal taxon-specific discrepancies between field and laboratory TEP production capacities. Notably, temperature, ammonium, and polysaccharide composition act as secondary modifiers of through indirect physiological effects. This study revealed that when the chlorophyll a concentration (Chl a) of P. antarctica exceeds 0.5 μg/L in the Cosmonaut Sea, its TEP production capacity surpasses that of diatoms at equivalent biomass levels – challenging the paradigm of diatom-dominated TEP contributions. In the research area, P. antarctica contributed 14.6–82.5 % (mean: 48.6 ± 15.4 %) to total TEP production, while diatoms contributed 31.0–112.0 % (mean: 55.1 ± 21.2 %; values >100 % reflect co-occurring group contributions). This highlights the pivotal role of P. antarctica in Southern Ocean carbon cycling and provides mechanistic insights for refining polar carbon budget models.