Journal Article

Physiological Responses of Three Species of Antarctic Mixotrophic Phytoflagellates to Changes in Light and Dissolved Nutrients

Gast, Rebecca J., Sanders, Robert W., McKie-Krisberg, Zaid M.

2015

Overview

Antarctic phototrophs are challenged by extreme temperatures, ice cover, nutrient limitation, and prolonged periods of darkness. Yet this environment may also provide niche opportunities for phytoplankton utilizing alternative nutritional modes. Mixotrophy, the combination of photosynthesis and particle ingestion, has been proposed as a mechanism for some phytoplankton to contend with the adverse conditions of the Antarctic. We conducted feeding experiments using fluorescent bacteria-sized tracers to compare the effects of light and nutrients on bacterivory rates in three Antarctic marine photosynthetic nanoflagellates representing two evolutionary lineages: Cryptophyceae (Geminigera cryophila) and Prasinophyceae (Pyramimonas tychotreta and Mantoniella antarctica). Only G. cryophila had previously been identified as mixotrophic. We also measured photoautotrophic abilities over a range of light intensities (P vs. I) and used dark survival experiments to assess cell population dynamics in the absence of light. Feeding behavior in these three nanoflagellates was affected by either light, nutrient levels, or a combination of both factors in a species-specific manner that was not conserved by evolutionary lineage. The different responses to environmental factors by these mixotrophs supported the idea of tradeoffs in the use of phagotrophy and phototrophy for growth.

• Publisher: Springer,Springer US,Springer Nature B.V
• Subject: Adaptation, Biological - physiology / Analysis of Variance / Antarctic region / Antarctic Regions / autotrophs / Biomedical and Life Sciences / Cell survival / Chlorophyta - physiology / Cryptophyceae / Cryptophyta - physiology / Darkness / Ecology / Environmental factors / Feeding behavior / Feeding experiments / Feeding habits / Fluorescence / Fluorescent indicators / Food - statistics & numerical data / Geminigera / Geoecology/Natural Processes / ice / Ice cover / Ingestion / Life Sciences / Light / Light effects / light intensity / Luminous intensity / Mantoniella / Microbial Ecology / Microbiology / MICROBIOLOGY OF AQUATIC SYSTEMS / Mixotrophy / Nature Conservation / nutrient content / Nutrients / Photosynthesis / Phototrophic Processes - physiology / Phototrophy / physiological response / Physiological responses / Phytoplankton / Phytoplankton - physiology / Plankton / Population Dynamics / Prasinophyceae / Pyramimonas tychotreta / temperature / tracer techniques / Tracers / Water Quality/Water Pollution