Acidified seawater impacts sea urchin larvae pH regulatory systems relevant for calcification

Stumpp, Meike, Hu, Marian Yong-An, Melzner, Frank, Gutowska, Magdalena, Dorey, N., Himmerkus, Nina, Holtmann, Wiebke C., Dupont, S. T., Thorndyke, M. C. and Bleich, Markus (2012) Acidified seawater impacts sea urchin larvae pH regulatory systems relevant for calcification Proceedings of the National Academy of Sciences of the United States of America, 109 (44). pp. 18192-18197. DOI 10.1073/pnas.1209174109.

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Abstract

Calcifying echinoid larvae respond to changes in seawater carbonate chemistry with reduced growth and developmental delay. To date, no information exists on how ocean acidification acts on pH homeostasis in echinoderm larvae. Understanding acid–base regulatory capacities is important because intracellular formation and maintenance of the calcium carbonate skeleton is dependent on pH homeostasis. Using H+-selective microelectrodes and the pH-sensitive fluorescent dye BCECF, we conducted in vivo measurements of extracellular and intracellular pH (pHe and pHi) in echinoderm larvae. We exposed pluteus larvae to a range of seawater CO2 conditions and demonstrated that the extracellular compartment surrounding the calcifying primary mesenchyme cells (PMCs) conforms to the surrounding seawater with respect to pH during exposure to elevated seawater pCO2. Using FITC dextran conjugates, we demonstrate that sea urchin larvae have a leaky integument. PMCs and spicules are therefore directly exposed to strong changes in pHe whenever seawater pH changes. However, measurements of pHi demonstrated that PMCs are able to fully compensate an induced intracellular acidosis. This was highly dependent on Na+ and HCO3−, suggesting a bicarbonate buffer mechanism involving secondary active Na+-dependent membrane transport proteins. We suggest that, under ocean acidification, maintained pHi enables calcification to proceed despite decreased pHe. However, this probably causes enhanced costs. Increased costs for calcification or cellular homeostasis can be one of the main factors leading to modifications in energy partitioning, which then impacts growth and, ultimately, results in increased mortality of echinoid larvae during the pelagic life stage.

Document Type: Article
Additional Information: WOS:000311149900099
Keywords: AMORPHOUS CALCIUM-CARBONATE; PRIMARY MESENCHYME CELLS; ACID-BASE REGULATION; GIANT FIBER LOBE; INTRACELLULAR PH; BUFFERING CAPACITY; INORGANIC CARBON; PLUTEUS LARVAE; MYTILUS-EDULIS; CO2; pH microelectrode; Strongylocentrotus droebachiensis; acid-base regulation; Na+-HCO3- transport; epithelial transport
Research affiliation: Kiel University > Faculty of Medicine > Institute of Physiology
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-B Experimental Ecology - Benthic Ecology
Refereed: Yes
DOI etc.: 10.1073/pnas.1209174109
ISSN: 0027-8424
Projects: BIOACID
Date Deposited: 13 Nov 2012 10:07
Last Modified: 25 Oct 2016 12:33
URI: http://oceanrep.geomar.de/id/eprint/19188

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