Mesoscale oceanographic meanders influence protist community function and structure in the southern Indian Ocean

• Published in: Environmental microbiology Vol. 25; no. 12; pp. 3161 - 3179
• Main Authors: Sturm, Daniela, Vries, Joost, Balch, William M., Wheeler, Glen, Brownlee, Colin
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.12.2023; Wiley Subscription Services, Inc
• Subjects: Biodiversity; Biological activity; Carbon dioxide; Community structure; Dinoflagellates; Dinoflagellida - genetics; DNA, Ribosomal - genetics; Drawdown; Environmental conditions; Fluorimetry; Indian Ocean; Mesoscale phenomena; Microscopy; Phytoplankton; Phytoplankton - genetics; Pulse amplitude; Structure-function relationships; Indian Ocean; Southern Ocean
• ISSN: 1462-2912; 1462-2920; 1462-2920
• DOI: 10.1111/1462-2920.16500

The interface between the nutrient‐rich Southern Ocean and oligotrophic Indian Ocean creates unique environmental conditions that can strongly influence biological processes. We investigated protist communities across a mesoscale meander of the Subtropical Front within the Southern Indian Ocean. 18S V9 rDNA metabarcoding suggests a diverse protist community in which the dinoflagellates and parasitic Syndiniales were abundant. Diversity was highest in frontal waters of the mesoscale meander, with differences in community structure inside and outside the meander. While the overall community was dominated by mixotrophic taxa, the frontal boundary of the meander had increased abundances of heterotrophic taxa, with potential implications for net atmospheric CO2 drawdown. Pulse amplitude modulated (PAM) fluorimetry revealed significant differences in the photophysiology of phytoplankton communities inside and outside the meander. By using single‐cell PAM microscopy, we identified physiological differences between dinoflagellate and coccolithophore taxa, which may have contributed to changes in photophysiology observed at community level. Overall, our results demonstrate that frontal areas have a strong impact on the composition of protist communities in the Southern Ocean with important implications for understanding biological processes in this region. We studied species composition and photo physiological properties of protist communities across a meander region in the Southern Indian Ocean. Metabarcoding revealed varying community composition in different meander regions corresponding to environmental gradients. Taxon‐specific photo physiological properties indicate that overall community physiology is determined by both community composition and species‐specific physiology.