EGS Seminar Tuesday 07 December 2010

Tuesday 07th December, E0.05 from 1.00-2.00 pm.
Lunch, and an opportunity to chat with the speaker, will be in room E402 from 12:30. All are invited!

Professor Chris Perry, MMU

‘Fish as a Newly Discovered Source of Carbonate Sediment: Their Role in the Tropical Carbonate Factory’



This talk will focus on the recent discovery that marine bony fish (like barracuda, flatfish and grouper, collectively known as 'teleosts') excrete high volumes of calcium carbonate from their guts and that this represents a major, but previously unknown, source of fine-grained carbonate sediment. Teleosts precipitate this carbonate within their guts as a by-product of continuously drinking Ca- and Mg-rich seawater, excreting the ingested marine Ca and Mg as insoluble carbonate within mucus envelopes. Our recent research, funded through a NERC small grant in 2008, lead to a series of novel findings regarding the significance of fish-derived carbonates within tropical marine environments, and which have potentially major implications for the field of carbonate sedimentology.

Firstly, we generated the first data on the compositional and morphological characteristics of the carbonates produced by any marine fish, showing that tropical fish produce a diverse array of fine-grained, mainly high Mg-calcite crystals, and that crystal morphologies fundamentally differ from those associated with all known biogenic and abiotic sources of marine carbonate. These carbonates are thus highly relevant to the controversial issue of where tropical carbonate muds are sourced from. Secondly, using our own newly measured fish carbonate production rate data from the Bahamas, combined with fish biomass data based on existing ecological surveys, we made the first regional-scale estimates of fish carbonate production in the tropics. Our data indicate that fish produce ~6 million kilograms of carbonate sediment each year across the Bahamas (equivalent to ~14 % of estimated total carbonate mud production, and up to 70 % in particular habitats). Thirdly, we have made the crucial observation that the crystals produced by fish occur commonly in the finest sediment fractions of surface sediments from all sedimentary environments examined in the Bahamas, thus demonstrating that such material does indeed represent both a novel and quantitatively important source of marine carbonate sediment. This presentation will discuss our current understanding of this recently discovered process and consider major areas of future research interest arising from this work.