Seminar Details

Microenvironments in Trichodesmium colonies

Date

26/04/2018

Lecturers

Dr. Meri Eichner - Max Planck Institute for Marine Microbiology, Bremen, Germany

Abstract

N2-fixation by the colony-forming cyanobacterium Trichodesmium is an important source of new nitrogen in oligotrophic oceans. For understanding the ecology and physiology of this keystone species in a changing climate, we need to consider the potential implications of colony formation for chemical microenvironments and biotic interactions. The first part of my presentation will focus on a field study in the North Pacific Subtropical Gyre targeting gradients of O2 and pH as well as single-cell fluxes of carbon and nitrogen in Trichodesmium colonies under different pCO2 levels. Microsensor measurements and single-cell analysis by nanoSIMS indicated that cells within colonies experienced large fluctuations in O2, pH and CO2 concentrations, and showed high variability in carbon and nitrogen assimilation on a single-cell level. Secondly, I will present a laboratory study on O2 dynamics and feedbacks on N2 fixation within Trichodesmium colonies, questioning the paradigm of colony formation as a benefit to N2 fixation. Collectively, these studies highlight that a detailed characterization of microenvironments is crucial for our understanding of the ecophysiology of colony-forming phytoplankton such as Trichodesmium.

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