Poster SCAR Uribe et al. 2012
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Normalized by Chl-a, the pigment content of Chl 2, was lower in Navicula directa and S kerguelensis, and was intermediate in Nitzschia sp. 1 and 2 Navicula showed an important increase of the de-epoxidation rate with light intensity compared to other species groups, Nitzschia species had intermediate and similar values at all light intensities. Fucoxanthin/Chl a content is similar among all species at all light intensities The proportion of photoprotective pigments of Navicula species decreases with light intensity, S. kerguelensis, P. kamshiaticum 2 showed the highest values and increase at 100 µMol Photons m-2 s-1. PHOTOSYNTHETIC RESPONSE AND PIGMENT RATIOS OF ANTARTIC MARINE BENTHIC DIATOMS EXPOSED TO DIFFERENT LIGHT INTENSITIES INTRODUCTION Benthic diatoms represent the 40-50 of primary pro- duction of coastal marine environments (Falkowski and Raven, 1997; Underwood and Kromkamp, 1999). In Antarctica, they are exposed to high variations of light intensity and photoperiod during the year. Due to their low light acclimation capacity (Robinson et al, 1995), they are the supporting food or “winter fo- rage” for a diversity of invertebrates, small crusta- ceans (Krill), that feed penguins, seals and whales during the dark and cold season. Fluctuations of marine ice coverage have been re- ported over the recent decades in Antarctica (Gor- don, 1981). However, their effects on benthic pri- mary producers are not well understood. The study photosynthetic response of Antarctic benthic diatom species is necessary to assess their light intensity tolerance range and stress symptoms related to the eventual marine ice coverage reduction. These pro- perties are also reflected in the quantity and propor- tion of pigments (Petrou et al, 2010), photoprotecti- ve / photosynthetic pigments ratios, and the ratio of accessory pigments to chlorophyll a. The purpose of this study is to determine the photosynthetic para- meters and pigments contents and ratio of individual species of benthic diatoms from Bahía Covadonga, Bernardo O’Higgins Antarctic Station (63°19’15’’S, 57°53’55’’W), Antarctic Peninsula, in response to dif- ferent light intensities. ABSTRACT Antarctic benthic diatom communities account for 40% of the primary production in shallow coastal areas. They are exposed to wide variations in light intensity and duration over an annual cycle. In particular, they persist in these coastal areas during the austral winter under the sea-ice cover in very low light conditions. They play a vital role in the winter food web, providing “winter forage” crucial for a diversity of marine organisms such as small crustaceans and krill. Despite their ecological importance, community composition, physiology and their acclimation to low light remain poorly understood. This study investigated photo-physiolo- gical responses in eight benthic diatom species collected from different depths of Covadonga Bay O’Higgins Station (63°19´15´´S, 57°53´55´´W) in January 2009. Diatoms were grown in low light and exposed to six different irradiances for five hours. Physiological responses were assessed by measuring the photosynthetic parameters: Quantum Yield (φPSII); relative Electron Transport Rate (rETR); and light utilization efficiency (α), following the 5-hour exposure to light and again after 30 min of darkness. Pigment composition of each species was analyzed by HPLC before and after light treatment. Our results show low-light acclimation in all eight species with photoinhibition occurring at 100-200 µmol photons m-2 s-1. Species from the genus Nitzschia showed higher tolerance to greater light intensities than those from the genus Navicula. Important questions arise regarding the mechanisms involved in photoprotection among benthic diatoms, as well as the role light plays in determining their spatial and temporal distribution. Navicula species showed the lowest Quantum yield, and Nitzschia the highest at higher light intensities. S. kerguelensis and Pseudogomphonema had intermediate responses. All species showed photo-inhibition at 200 µMol Photons m-2 s-1 Recovery capacity was the lowest in Navicula compared to all other species that showed values over 85% on the range of light intensity studied CONCLUSIONS • Species groups or genus of Antarctic Benthic Diatoms studied showed differences in their photosynthetic efficiency and photoprotective response to light intensity vari ation. • This results suggest that the differences of response and plasticity to light intensity variation are due to differences of their mechanisms of regulation of the photoprotec tive pigments proportion and their de-epoxidation rate among this species groups. • Navicula species are acclimated to lower light environments and have low plasticity, with high de-epoxidation rates, Nitzschia and Pseudogomphonema species can accomodate to higher light enviroments displaying a photoprotective response and maintainig low de-epoxidation ratios. Synedra kerguelensis had the highest tolerance range of light intensity, not related with these pigment responses. REFERENCES Falkowski, PG. and J. Raven. 1997. Aquatic Photosynthesis, Blackwell, Oxford UK. Underwood, GJC and Kromkamp J.1999. Adv Ecol Res 29:93-153. Robinson DH et al. 1995. J of Phycol 31:508-520. Gordon, AL 1981. J Geophys Res 86: 4193-4197. ACKNOWLEDGEMENTS INACH T11-08 Project A. Palma, A. Díaz and L. Henríquez (Catholic University of Chile) G. Barahona (HFBK, Hamburg, Deutschland) Technical assistance. B.O’Higgins and Escudero Antarctic Stations personnel. Background picture: Pedro Niada Uribe Paulina 1 , Petrou Katherina 2 , Zbinden Marlene 2 , Molina Ernesto 2 . 1: Fundacion Ciencia para la Vida, Santiago, Chile; 2: Plant Functional Biology & Climate Change Cluster (C3) University of Technology of Sydney, Australia MATERIALS AND METHODS RESULTS
description
PHOTOSYNTHETIC RESPONSE AND PIGMENT RATIOS OF ANTARTIC MARINE BENTHIC DIATOMS EXPOSED TO DIFFERENT LIGHT INTENSITIESUribe Paulina 1 , Petrou Katherina 2 , Zbinden Marlene 2 , Molina Ernesto 2 . 1: Fundacion Ciencia para la Vida, Santiago, Chile; 2: Plant Functional Biology & Climate Change Cluster (C3) University of Technology of Sydney, AustraliaABSTRACTAntarctic benthic diatom communities account for 40% of the primary production in shallow coastal areas. They are exposed to wide variation
Transcript of Poster SCAR Uribe et al. 2012
Normalized by Chl-a, the pigment content of Chl 2, was lower in Navicula directa and S kerguelensis, and was intermediate in Nitzschia sp. 1 and 2
Navicula showed an important increase of the de-epoxidation rate with light intensity compared to other species groups, Nitzschia species had intermediate and similar values at all light intensities.
Fucoxanthin/Chl a content is similar among all species at all light intensities The proportion of photoprotective pigments of Navicula species decreases with light intensity, S. kerguelensis, P. kamshiaticum 2 showed the highest values and increase at 100 µMol Photons m-2 s-1.
PHOTOSYNTHETIC RESPONSE AND PIGMENT RATIOS OF ANTARTIC MARINE BENTHIC DIATOMS EXPOSED TO DIFFERENT LIGHT INTENSITIES
INTRODUCTION
Benthic diatoms represent the 40-50 of primary pro-duction of coastal marine environments (Falkowski and Raven, 1997; Underwood and Kromkamp, 1999). In Antarctica, they are exposed to high variations of light intensity and photoperiod during the year. Due to their low light acclimation capacity (Robinson et al, 1995), they are the supporting food or “winter fo-rage” for a diversity of invertebrates, small crusta-ceans (Krill), that feed penguins, seals and whales during the dark and cold season. Fluctuations of marine ice coverage have been re-ported over the recent decades in Antarctica (Gor-don, 1981). However, their effects on benthic pri-mary producers are not well understood. The study photosynthetic response of Antarctic benthic diatom species is necessary to assess their light intensity tolerance range and stress symptoms related to the eventual marine ice coverage reduction. These pro-perties are also reflected in the quantity and propor-tion of pigments (Petrou et al, 2010), photoprotecti-ve / photosynthetic pigments ratios, and the ratio of accessory pigments to chlorophyll a. The purpose of this study is to determine the photosynthetic para-meters and pigments contents and ratio of individual species of benthic diatoms from Bahía Covadonga, Bernardo O’Higgins Antarctic Station (63°19’15’’S, 57°53’55’’W), Antarctic Peninsula, in response to dif-ferent light intensities.
ABSTRACTAntarctic benthic diatom communities account for 40% of the primary production in shallow coastal areas. They are exposed to wide variations in light intensity and duration over an annual cycle. In particular, they persist in these coastal areas during the austral winter under the sea-ice cover in very low light conditions. They play a vital role in the winter food web, providing “winter forage” crucial for a diversity of marine organisms such as small crustaceans and krill. Despite their ecological importance, community composition, physiology and their acclimation to low light remain poorly understood. This study investigated photo-physiolo-gical responses in eight benthic diatom species collected from different depths of Covadonga Bay O’Higgins Station (63°19´15´´S, 57°53´55´´W) in January 2009. Diatoms were grown in low light and exposed to six different irradiances for five hours. Physiological responses were assessed by measuring the photosynthetic parameters: Quantum Yield (φPSII); relative Electron Transport Rate (rETR); and light utilization efficiency (α), following the 5-hour exposure to light and again after 30 min of darkness. Pigment composition of each species was analyzed by HPLC before and after light treatment. Our results show low-light acclimation in all eight species with photoinhibition occurring at 100-200 µmol photons m-2 s-1. Species from the genus Nitzschia showed higher tolerance to greater light intensities than those from the genus Navicula. Important questions arise regarding the mechanisms involved in photoprotection among benthic diatoms, as well as the role light plays in determining their spatial and temporal distribution.
Navicula species showed the lowest Quantum yield, and Nitzschia the highest at higher light intensities. S. kerguelensis and Pseudogomphonema had intermediate responses. All species showed photo-inhibition at 200 µMol Photons m-2 s-1
Recovery capacity was the lowest in Navicula compared to all other species that showed values over 85% on the range of light intensity studied
CONCLUSIONS
• Species groups or genus of Antarctic Benthic Diatoms studied showed differences in their photosynthetic efficiency and photoprotective response to light intensity vari ation. • This results suggest that the differences of response and plasticity to light intensity variation are due to differences of their mechanisms of regulation of the photoprotec tive pigments proportion and their de-epoxidation rate among this species groups. • Navicula species are acclimated to lower light environments and have low plasticity, with high de-epoxidation rates, Nitzschia and Pseudogomphonema species can accomodate to higher light enviroments displaying a photoprotective response and maintainig low de-epoxidation ratios. Synedra kerguelensis had the highest tolerance range of light intensity, not related with these pigment responses.
REFERENCES
Falkowski, PG. and J. Raven. 1997. Aquatic Photosynthesis, Blackwell, Oxford UK.Underwood, GJC and Kromkamp J.1999. Adv Ecol Res 29:93-153.Robinson DH et al. 1995. J of Phycol 31:508-520.Gordon, AL 1981. J Geophys Res 86: 4193-4197.
ACKNOWLEDGEMENTS
INACH T11-08 Project A. Palma, A. Díaz and L. Henríquez (Catholic University of Chile)G. Barahona (HFBK, Hamburg, Deutschland) Technical assistance.B.O’Higgins and Escudero Antarctic Stations personnel.Background picture: Pedro Niada
Uribe Paulina1, Petrou Katherina2, Zbinden Marlene2, Molina Ernesto2. 1: Fundacion Ciencia para la Vida, Santiago, Chile; 2: Plant Functional Biology & Climate Change Cluster (C3) University of Technology of Sydney, Australia
MATERIALS AND METHODS RESULTS
