Fish as major carbonate mud producers and missing components of the tropical carbonate factory

Proceedings of the National Academy of Sciences of the United States of America
By: , and 

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Abstract

Carbonate mud is a major constituent of recent marine carbonate sediments and of ancient limestones, which contain unique records of changes in ocean chemistry and climate shifts in the geological past. However, the origin of carbonate mud is controversial and often problematic to resolve. Here we show that tropical marine fish produce and excrete various forms of precipitated (nonskeletal) calcium carbonate from their guts ("low" and "high" Mg-calcite and aragonite), but that very fine-grained (mostly <2 ??m) high Mg-calcite crystallites (i.e., >4 mole % MgCO3) are their dominant excretory product. Crystallites from fish are morphologically diverse and species-specific, but all are unique relative to previously known biogenic and abiotic sources of carbonate within open marine systems. Using site specific fish biomass and carbonate excretion rate data we estimate that fish produce ???6.1 ?? 106 kg CaCO3/year across the Bahamian archipelago, all as mud-grade (the <63 ??m fraction) carbonate and thus as a potential sediment constituent. Estimated contributions from fish to total carbonate mud production average ???14% overall, and exceed 70% in specific habitats. Critically, we also document the widespread presence of these distinctive fish-derived carbonates in the finest sediment fractions from all habitat types in the Bahamas, demonstrating that these carbonates have direct relevance to contemporary carbonate sediment budgets. Fish thus represent a hitherto unrecognized but significant source of fine-grained carbonate sediment, the discovery of which has direct application to the conceptual ideas of how marine carbonate factories function both today and in the past.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Fish as major carbonate mud producers and missing components of the tropical carbonate factory
Series title Proceedings of the National Academy of Sciences of the United States of America
DOI 10.1073/pnas.1015895108
Volume 108
Issue 10
Year Published 2011
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Proceedings of the National Academy of Sciences of the United States of America
First page 3865
Last page 3869