PARENT SESSION
Posters P5D Emerging techniques and systems. Abstracts (731-741)

Fluorescence induction and relaxation (FIRE) technique and instrumentation for monitoring photosynthetic processes and primary production in aquatic ecosystems. Maxim Gorbunov^{*,1, 2}, Paul Falkowski¹, ¹ Environmental Biophysics and Molecular Ecology Program, New Brunswick, NJ, USA² Satlantic Inc., Halifax, NS, Canada

ABSTRACT- Over the last decade, the Fast Repetition Rate Fluorometry (FRRF) provided tremendous insight into the factors controlling primary production in the ocean. The use of FRRF became an integral part of many biological oceanographic programs, but its broader use is limited by the complexity and high cost of the available instrumentation. We have designed and built a new instrument to measure photosynthetic characteristics in algae and benthic organisms, such as macrophytes and corals. The Fluorescence Induction and Relaxation (FIRe) technique and realized instrumentation are based on similar biophysical principles as the FRRF, but the technical implementation and measurement protocols have been simplified, greatly reducing the production cost. The FIRe technique relies on active stimulation and highly resolved detection of the induction and subsequent relaxation of chlorophyll fluorescence yields. A multicolor excitation source has been implemented to accommodate efficient excitation of diverse functional groups within phytoplankton communities. Analysis of fluorescence induction on microsecond time scales results in the minimum and maximum fluorescence yields, the quantum efficiency of photochemistry in PSII, the functional absorption cross-section of PSII, and the energy transfer between PSII units. The recorded relaxation kinetics of fluorescence yields reflects the rates of electron transport on the acceptor side of PSII and between PSII and PSI. The photosynthetic electron transport rates as a function of irradiance, together with coefficients of photochemical and non-photochemical quenching are measured using an incorporated source of background light. A benchtop version of the FIRe Meter is used for measurements on phytoplankton samples or macrophyte leaves. The compact design, low power consumption, and network capability of the submersible version of the FIRe Meter make it an efficient sensor for long-term monitoring programs in coastal zones and the open ocean. Examples of applications for monitoring of phytoplankton communities and coral reefs are presented and discussed.

KEY WORDS: primary productivity, variable fluorescence, chlorophyll