Variable Fluorescence Performance Data: Mapping the yield during a red tide, yield in relation to copper sulfate, new red active fluorometer data (specific to cyanobacteria)

Introduction

Turner Designs, Inc has developed an in situ variable fluorescence system that can be used to determine the quantum efficiency of phytoplankton in both oligotrophic and mesotrophic environments. The PhytoFlash can be integrated into a CTD or multi-parameter system, used in self-contained mode in conjunction with the internal data logger and attachable battery or in flow-through mode for laboratory work and in underway monitoring mode. The variable fluorescence measurement is being used in an ever-growing list of applications, such as;

• In situ measurement of phytoplankton photosynthetic parameters
• Indicator of nutrient status of planktonic algae
• Detection of the onset of algae blooms
• Accurate measurement of algal biomass and monitoring algal community changes
• Ballast water monitoring

The PhytoFlash technique utilizes 3 low intensity LEDs to measure Fo and Fm and 6 high intensity LEDs to saturate cells in the sample chamber. The response curve from the saturating flash can be viewed in the laboratory mode. Unlike other ‘active’ fluorescence systems, the PhytoFlash does not provide induction curve data and is not designed as a physiological instrument for laboratory use. Rather, it is designed as a simplified and robust variable fluorescence system for submersible and/or laboratory use.

UNDERWAY MAPPING OF YIELD (Fv/Fm) DURING A REDTIDE OFF THE COAST OF CALIFORNIA

Data was collected during a cruise in Monterey Bay in September 2006 as a large red tide (>250 µg Chl) event was occurring. The yield data was collected by a PhytoFlash active fluorometer during tows. The PhytoFlash was collecting data as it was in line with the underway sampling system.

Sampling Protocol

The underway data show that higher yields were concentrated in the center of the Bay. Higher biomass concentrations mostly occurred along the coast. The bloom was dominated by the dinoflagellate Akashiwo sanguinea.

Preliminary conclusions suggest that the highest biomass (fluorescence) was not necessarily the highest Yield, and that the low biomass waters were “healthy” (Fv/Fm >0.6).

HOW YIELD (Fv/Fm) CHANGES WHEN A SYSTEM IS IMPACTED

Design
Copper sulfate (CuSO4) was used in an experiment designed to demonstrate the change in yield in relation to an “impacted” system. CuSO4 impacts algal cells by inhibiting specific mechanisms of photosynthesis. Two sub-samples of a green algal monoculture (Dunaliella) at a 50 µg/l concentration were prepared. One sample acted as a control and 100 µM of CuSO4 was added to the second sample. Samples were evaluated using the PhytoFlash active fluorometer. The instrument was blanked using artificial seawater (35 psu) for each sample. Samples were measured at 1-minute intervals over a 50-minute period to assess the natural variability of the control culture as well as the effect of CuSO4. At the 4-minute time interval 100 µM of CuSO4 was added to the second culture.

Results

Yields ranged from 0.588-0.648 for the control sample over 50-minutes displaying natural variability. At approximately 16-minutes after the addition of CuSO4 yields begin to deviate from the natural range of variability. At the end of the experiment (50-minutes) yields dropped significantly to 0.216 for the CuSO4 sample and the control remained above 0.6. The PhytoFlash active fluorometer was able to detect an impact in the system which was negatively affecting photosynthesis.

RED PHYTOFLASH - SENSITIVE TO CYANOBACTERIA

The Red PhytoFlash was developed in an effort to provide variable fluorescence measurements sensitive to cyanobacteria and prochlorophytes.

Optical Specifications:
Excitation Filter 635nm
Emission Filter 710-835nm
LED wavelength 630nm

*Photosynthetic Parameters, Electrical and Physical Specifications are the Same as the BLUE PhytoFlash

RED PhytoFlash Induction Curve

Preliminary RED and BLUE PhytoFlash variable fluorescence data from a cruise off the Fiji Islands. A comparison of Fv/Fm for the RED and BLUE PhytoFlash was generated over a one hour period at station 24. Higher Fv/Fm values for the RED PhytoFlash correlates toCrocosphaera dominated water found at station 24.