An Unusual Chlorophyll a Derivative in Tropical Phytoplankton: Artifact or Real?

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A derivative of chlorophyll has been detected in tropical North Atlantic and North Pacific in recent years. This is significant because the derivative was found in concentrations equal or higher to chlorophyll a. The derivative also has similar optical characteristics and thus this finding may alter our interpretation of chlorophyll as a biomass marker. This support will enable Dr. Vernet to isolate, identify and begin a preliminary characterization of this chlorophyll a derivative by using a combination of techniques. These include; high performance liquid chromatography, absorption and fluorescence spectra, and high resolution mass spectrometry. Accessory pigments associated with the chlorophyll derivative will be estimated by chromatography and in vivo fluorescence spectra. Also, the photosynthetic activity of the plankton fraction rich in this chlorophyll derivative will be determined using in vivo fluorescence excitation spectra and 14C labeled chlorophyll. The combination of these methods should establish the authenticity of this altered chlorophyll in marine phytoplankton and its activity with respect to chlorophyll a. Microscopic plants suspended in the surface layer of the ocean are responsible for most of the ocean's biological production, and these plants contain pigments for absorbing sunlight just as their terrestrial counterparts do. Pigments such as chlorophyll a have long been used to quantify marine phytoplankton through direct chemical analysis of the chlorophyll present in a given body of water. Dr. Vernet will investigate an unusual pigment that has been discovered in tropical water that is chemically similar to chlorophyll a. Because chlorophyll a is used extensively to estimate plant biomass in biological oceanography, the potential impact of this recently discovered pigment on our interpretation of surface ocean biology is substantial. Through chemical and biological studies in association with a recognized expert in the field, (Dr. W. Gieskes), Dr. Vernet will determine if this unusual pigment can also be used as an indicator of plant biomass. Dr. Vernet is very qualified to carry out this study and significant benefit to our understanding of plant pigments in ocean water will result.