Effects of ocean acidification on key physiological parameters in the green sea urchin Strongylocentrotus droebachiensis

• Main Author: Trübenbach, Katja
• Format: Thesis
• Language: English
• Published: 2009
• Subjects: Ocean acidification
• Online Access: https://oceanrep.geomar.de/id/eprint/5058/; https://oceanrep.geomar.de/id/eprint/5058/1/Dipl.%202009%20Tr%C3%BCbenbach,%20K.pdf

Since the last two centuries anthropogenic C02 emissions arising from the combustion of fossil fuels have altered seawater chemistry far more rapidly than previously experienced in earth history. The rate and extent of this change are expected to affect marine organisms and entire ecosystems. Excess C0 2 diffuses from the atmosphere into ocean surface waters, resulting in elevated seawater C02 partial pressure, as weil as reduced [CO3 2-] and pH. These changes in carbonate system speciation have been demonstrated to especially impact calcifying organisms. The present study focuses on the effects of ocean acidification on adult specimens of the green sea urchin Strongylocentrotus droebachiensis, a keystone predator and grazer in ecosystems of the northern hemisphere. Laboratory experiments revealed that the potential of S. droebachiensis to cope with COrdriven ocean acidification is surprisingly high. The green sea urchin was able to fully compensate its extracellular pH by active accumulation of HC03- ions (3-4 mM) under exposure to 140 Pa. Thereby, accumulation of HC03- was facilitated by active ion regulation processes and not due to passive shell dissolution. Between the pC02 treatments 140 and 400 Pa, an ion exchange capacity limit was detected, beyond this the extracellular pH could no langer be achieved and declined by about 0.2 units. Simultaneously, in high pC02 treatments (400 Pa), extracellular bicarbonate concentration was maintained, resulting in a partial compensation of S. droebachiensis extracellular body fluid. Under long-term exposure ( 400 Pa), an upregulation of respiratory chain cytochrome oxidase in the podia of the green sea urchin could point at mitochondrial proliferation and a general elevation in aerobic metabolism, as active compensation of extracellular pH increases total energy demand. The suggested metabolic upregulation could potentially ameliorate some of the effects of increased acidity, but at similar feeding intake rates it might come at a substantial cost (e.g. decreased ...