Photosynthesis in the intertidal macroalga Fucus vesiculosus L. (Phaeophyta): an investigation into the composition of a stored carbon pool
Date
2005
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Publisher
University of Delaware
Abstract
A source of carbon dioxide is one of the main requirements for photosynthesis in all plant species. For marine macroalgae, inorganic carbon is readily available in seawater. Intertidal species spend time exposed to air, which has a much lower concentration of inorganic carbon. Several studies recognize the ability of marine macroalgae to accumulate carbon from seawater and from air. The nature of the stored carbon is not well understood. The main objective of this study was to determine the composition of the stored carbon pool in Fucus vesiculosus L. (Phaeophyta). Photosynthesis measurements using an oxygen electrode provided a means to follow the status of the carbon pool. Algal tissue was exposed to air with 1% CO2 and to CO2-free air to build and deplete the carbon store, respectively. After treatment, organic compounds were extracted from the tissue. Because of previous work in terrestrial and marine species, malate, aspartate, and free amino acids were targeted as the most likely candidates for the stored carbon pool. These target compounds were analyzed using enzyme assays. Analysis of the extracts determined there was no measurable malate in the tissue. The concentration of aspartate in the tissue samples averaged 0.35 mmol m-2, whereas the total stored carbon pool was estimated at 7.58 mmol m-2. Additionally, the total free amino acid (FAA) pool size was approximately 5.72 mmol m-2. Pool sizes for aspartate and FAA did not follow a pattern to suggest either of these as the stored carbon source. Further analysis should re-investigate if the stored pool is in fact organic in nature. I also investigated the physiological response of F. vesiculosus in various carbon environments. In contrast to previous research, photosynthesis data indicate the alga may store carbon while in the dark. Additional physiological measurements are necessary before further conclusions can be drawn concerning the carbon storage capabilities of F. vesiculosus.