Biology subjects

Rose, J. M.

Publications and source records attributed to Rose, J. M..

2 recordsLinked to original sources

bioRxiv2026

The Role of Photoperiod, Light Intensity, and Iron Concentration on Cellular Physiology Photophysiology, and Proteomics in Southern Ocean Phytoplankton.

Primary production in the Southern Ocean (SO) plays a critical role in regulating the global carbon cycle, yet the physiological mechanisms governing phytoplankton responses to iron (Fe) limitation and variable light remain poorly constrained. Using a custom made incubation system that simulated natural diel solar variability, we examined the interactive effects of Fe availability, light intensity, and photoperiod (continuous vs. variable) on three ecologically important SO phytoplankton: Fragilariopsis cylindrus, Phaeocystis antarctica, and Thalassiosira antarctica. Physiological, photophysiological, and proteomic measurements revealed that Fe availability was the dominant factor regulating growth, carbon production, photosynthetic performance and protein expression across all species. Distinct acclimation strategies emerged: F. cylindrus exhibited marked trade-offs between productivity and photoprotection under Fe stress, consistent with adaptation to stable, low-light, Fe-poor environments; P. antarctica maintained growth by flexibly modulating photoprotective and photosynthetic capacity, reflecting high plasticity suited to dynamic, open-ocean conditions; and T. antarctica expressed a balanced strategy, sustaining productivity and photoprotection simultaneously, characteristic of coastal bloom formers with higher Fe demand. Dynamic light regimes produced smaller, species-specific effects, influencing chlorophyll content and carbon storage primarily in T. antarctica. Correlation and z-score analyses demonstrated that Fe-rich photosynthetic proteins co-varied with biomass production, whereas photoprotective traits clustered independently, underscoring divergent energy-allocation strategies. Together, these results reveal how SO phytoplankton partition resources between productivity and photoprotection under shifting Fe-light regimes, providing mechanistic insight into their ecological niches.

ecology↗

bioRxiv2025

Primary productivity and N2-fixation in the eastern Indian Ocean: bottom-up support for an ecologically and economically important ecosystem

Oligotrophic regions of the global ocean are characterized by strong nutrient limitation, low standing phytoplankton biomass, and highly efficient nutrient recycling. We quantified nutrient inventories, primary productivity and N2 fixation during the BLOOFINZ-IO expedition (February 2022) in the Argo Basin located in the eastern Indian Ocean, the sole known spawning ground for Southern Bluefin Tuna. Surface nitrate concentrations were near depletion (<0.02 {micro}mol L-1), with low but persistent residual phosphate (P) concentrations suggesting nitrogen as the major limiting nutrient. Depth-integrated net primary production (NPP), from 14C-based in-situ incubations during 4 Lagrangian cycles, averaged [~]460 mg C m-2d-1, in good agreement with satellite-based NPP estimates. Nitrogen fixation provided a consistent new nitrogen source, contributing [~]16% to local NPP in the upper euphotic zone. Gross primary production (GPP), derived from fast-repetition-rate-fluorometry-based electron transport estimates, revealed significant autotrophic respiration losses, with GPP:NPP ratios averaging [~]1.8, consistent with metabolic costs under nutrient limitation. Net community production (NCP), estimated from O2/Ar ratios, remained positive across all cycles, averaging [~]20% of NPP in the upper 30 m. This result, in combination with N2 fixation measurement indicates that N2 fixation supports most of the export production in this region. Together, the multi-method approach revealed a recycling-dominated ecosystem affected by episodic mixing events, where primary productivity is maintained primarily through efficient nitrogen recycling and physiological photoacclimation. These results provide a comprehensive baseline of bottom-up support on ecosystem productivity for the Argo Basin for assessing future climate-driven changes in stratification, nutrient cycling, and food-web dynamics.

ecology↗