Küter, Marie (2015) Oxygen consumption and polyp extension rates of the scleractinian cold-water coral Lophelia pertusa under different CO2 end-of-the-century scenarios. (Master thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 66 pp.

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Abstract

The scleractinian coral Lophelia pertusa forms large reefs and provides habitat for a huge number of associated species. These ecosystems are often described as biomass and biodiversity hotspots. Thus, the ecological relevance of this species is very high. Due to destruction by bottom trawling and hydrocarbon mining, these reefs are in danger. Additionally, they are endangered by climate change. The rise of temperature and the decrease in seawater pH are known to especially affect calcifying organisms. Since the industrial time, the ocean pH decreased from values around 8.2 to circa 8.1 and for the end of the century another 0.3 to 0.4 pH units of decrease is expected. The performed study dealed with mid-term physiological responses of the cold-water coral Lophelia pertusa in terms of shifts in oxygen consumption and behavior towards elevated carbon dioxide concentrations. The behavior of the corals was documented via 24 hours video observation and the polyp extension rates of single polyps were analyzed. Five replicates were kept under control conditions (8°C; 390 μatm pC02 ), while another five replicates ran through three successive elevated C02 scenarios (800 μatm/1000 μatm/1200 μatm). Each phase lasted 5 weeks, including one week of acclimatization and four following weeks of measurements. Each replicate was equipped with one coral fragment of a white color morph of L. pertusa and one coral fragment of a red color morph of L. pertusa, in order to estimate if the two color morphs occurring in Norwegian waters differ in physiological responses towards elevated pC02 conditions. Slight elevations of respiration rates in the red color morph were recognized, but were not approved to be significant. Respiration rates recorded for the control treatment ranged from 0.112 to 0.191 μmol 02 g -1 dry weight h-1 for the white color morph and from 0.114 to 0.238 μmol 02 g-1 dry weight h-1 for the red color morph. Respiration rates of the elevated treatment did not differ significantly from control values ( on average 0.185 μmol 02 g-1 dry weight h-1 for the white color morph and 0.204 μmol 02 g-1 dry weight h-1 for the red color morph). Corals might have acclimatized to changing conditions. Polyp extension rates of white corals in turn changed with increasing pC02 conditions. Mean polyp extension rates of the control were 24 ± 3 % throughout the entire experiment, while extension rates of the elevated treatment increased by 75 % during the first elevated pC02 phase and decreased down to 50 % of control values during the following phases of the experiment. This study shows that elevated pC02 conditions influence the behavior in terms of polyp extension rates of L. pertusa, but that respiration rates can be maintained during a mid-term period exposure to elevated pC02 conditions.

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