PHOTOSYNTHESIS AND RESPIRATION OF THE CONCHOCELIS STAGE OF ALASKAN PORPHYRA (BANGIALES,RHODOPHYTA) SPECIES IN RESPONSE TO ENVIRONMENTAL VARIABLES1 |
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| Authors: | Rulong Lin Sandra C. Lindstrom Michael S. Stekoll |
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| Affiliation: | 1. Key Laboratory of Global Change and Marine‐Atmospheric Chemistry and Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China;2. Author for correspondence: e‐mail .;3. Department of Botany, #3529 – 6270 University Blvd., University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada;4. Department of Natural Sciences, University of Alaska Southeast and Juneau Center, School of Fisheries and Ocean Science, University of Alaska Fairbanks, 11120 Glacier Highway, Juneau, Alaska 99801, USA |
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| Abstract: | Photosynthesis and respiration of three Alaskan Porphyra species, P. abbottiae V. Krishnam., P. pseudolinearis Ueda species complex (identified as P. “pseudolinearis” below), and P. torta V. Krishnam., were investigated under a range of environmental parameters. Photosynthesis versus irradiance (P–I) curves revealed that maximal photosynthesis (Pmax), irradiance at maximal photosynthesis (Imax), and compensation irradiance (Ic) varied with salinity, temperature, and species. The Pmax of Porphyra abbottiae conchocelis varied between 83 and 240 μmol O2 · g dwt?1 · h?1 (where dwt indicates dry weight) at 30–140 μmol photons · m?2 · s?1 (Imax) depending on temperature. Higher irradiances resulted in photoinhibition. Maximal photosynthesis of the conchocelis of P. abbottiae occurred at 11°C, 60 μmol photons · m?2·s?1, and 30 psu (practical salinity units). The conchocelis of P. “pseudolinearis” and P. torta had similar Pmax values but higher Imax values than those of P. abbottiae. The Pmax of P. “pseudolinearis” conchocelis was 200–240 μmol O2 · g dwt?1 · h?1 and for P. torta was 90–240 μmol O2 · g dwt?1 · h?1. Maximal photosynthesis for P. “pseudolinearis” occurred at 7°C and 250 μmol photons · m?2 · s?1 at 30 psu, but Pmax did not change much with temperature. Maximal photosynthesis for P. torta occurred at 15°C, 200 μmol photons · m?2 · s?1, and 30 psu. Photosynthesis rates for all species declined at salinities <25 or >35 psu. Estimated compensation irradiances (Ic) were relatively low (3–5 μmol · photons · m?2 · s?1) for intertidal macrophytes. Porphyra conchocelis had lower respiration rates at 7°C than at 11°C or 15°C. All three species exhibited minimal respiration rates at salinities between 25 and 35 psu. |
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| Keywords: | Alaska conchocelis culture irradiance marine algae photosynthesis Porphyra respiration salinity temperature |
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