TY - JOUR
T1 - The role of seawater endocytosis in the biomineralization process in calcareous foraminifera
AU - Bentov, Shmuel
AU - Brownlee, Colin
AU - Erez, Jonathan
PY - 2009/12/22
Y1 - 2009/12/22
N2 - Foraminifera are unicellular organisms that inhabit the oceans in various ecosystems. The majority of the foraminifera precipitate calcitic shells and are among the major CaCO3 producers in the oceans. They comprise an important component of the global carbon cycle and also provide valuable paleoceanographic information based on the relative abundance of stable isotopes and trace elements (proxies) in their shells. Understanding the biomineralization processes in foraminifera is important for predicting their calcification response to ocean acidification and for reliable interpretation of the paleoceanographic proxies. Most models of biomineralization invoke the involvement of membrane ion transporters (channels and pumps) in the delivery of Ca2+ and other ions to the calcification site. Here we show, in contrast, that in the benthic foraminiferan Amphistegina lobifera, (a shallow water species), transport of seawater via fluid phase endocytosis may account for most of the ions supplied to the calcification site. During their intracellular passage the seawater vacuoles undergo alkalization that elevates the CO32- concentration and further enhances their calcifying potential. This mechanism of biomineralization may explain why many calcareous foraminifera can be good recorders of paleoceanographic conditions. It may also explain the sensitivity to ocean acidification that was observed in several planktonic and benthic species.
AB - Foraminifera are unicellular organisms that inhabit the oceans in various ecosystems. The majority of the foraminifera precipitate calcitic shells and are among the major CaCO3 producers in the oceans. They comprise an important component of the global carbon cycle and also provide valuable paleoceanographic information based on the relative abundance of stable isotopes and trace elements (proxies) in their shells. Understanding the biomineralization processes in foraminifera is important for predicting their calcification response to ocean acidification and for reliable interpretation of the paleoceanographic proxies. Most models of biomineralization invoke the involvement of membrane ion transporters (channels and pumps) in the delivery of Ca2+ and other ions to the calcification site. Here we show, in contrast, that in the benthic foraminiferan Amphistegina lobifera, (a shallow water species), transport of seawater via fluid phase endocytosis may account for most of the ions supplied to the calcification site. During their intracellular passage the seawater vacuoles undergo alkalization that elevates the CO32- concentration and further enhances their calcifying potential. This mechanism of biomineralization may explain why many calcareous foraminifera can be good recorders of paleoceanographic conditions. It may also explain the sensitivity to ocean acidification that was observed in several planktonic and benthic species.
KW - Biomineralization
KW - Seawater vacuoles
UR - http://www.scopus.com/inward/record.url?scp=76049103635&partnerID=8YFLogxK
U2 - 10.1073/pnas.0906636106
DO - 10.1073/pnas.0906636106
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
C2 - 20007770
AN - SCOPUS:76049103635
SN - 0027-8424
VL - 106
SP - 21500
EP - 21504
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 51
ER -