Early diagenesis and vertical distribution of organic carbon and total nitrogen in recent sediments from southern Chilean fjords (Boca del Guafo to Pulluche Channel) Diag谷nesis temprana y distribuci車n vertical de carbono org芍nico y nitr車geno total en sedimentos recientes de los fiordos del sur de Chile (Boca del Guafo hasta canal Pulluche)

作者：Nora Rojas; Nelson Silva

来源：Investigaciones Marinas, 2005.

• sedimentos
• textura
• carbono
• nitrogeno
• C:N
• diagenesis
• fiordos
• Chile
• sediments
• grain size
• carbon
• nitrogen
• C:N
• diagenesis
• estuaries
• fjords
• Chile

Eleven surface sediment cores were taken with a Rumohr corer during the oceanographic cruise Cimar 8 Fiordos (July 2002; between the Corcovado Gulf and Pulluche Channel). These cores were used to determine the vertical distribution of organic carbon, total nitrogen, and their atomic ratio (C/N) for use as a diagenesis indicator. The grains observed were mostly clay-silt in four of the sediment cores and more heterogeneous in the other seven cores. Organic carbon and total nitrogen concentrations were higher in the four clay-silt cores than in the sandy cores, although in terms of their vertical distribution, both concentrations were relatively homogenous at most stations. Nevertheless, exponential decreases characteristic of first-order diagenetic degradation were observed in cores from three stations. The C:N ratio fluctuated between 7 and 10, indicating that the organic material in the sediments was mostly marine in origin. Values were lower at more oceanic stations and greater at more coastal stations; the contribution of terrigenous materials was greater at the latter. We inferred a slower break down of organic carbon as compared to total nitrogen from a steady-state first-order degradation kinetics model, that was applied to stations where both fractions had exponential vertical distributions. Remineralization percentages were between 23 and 34% (organic carbon) and 33 and 43% (total nitrogen) and accumulation percentages were between 77 and 66% (organic carbon) and 67 and 57% (total nitrogen) Durante el crucero oceanogr芍fico Cimar 8 Fiordos (julio 2002), entre golfo Corcovado y canal Pulluche, con un Rumohr corer se obtuvo 11 testigos de sedimentos superficiales. Con 谷stos se determin車 la distribuci車n vertical de carbono org芍nico, nitr車geno total y sus relaciones at車micas (C:N) para ser usados como indicadores de la presencia de procesos diagen谷ticos. En cuatro testigos o %26quot;cores%26quot;, la textura se caracteriz車 por estar compuesta principalmente por sedimento limo-arcilloso y en los otros siete la composici車n de textura fue m芍s heterog谷nea. Las muestras limo-arcillosas presentaron mayores concentraciones de C-org y N-tot, que aquellas m芍s arenosas. En cuanto a la distribuci車n vertical de C-org y N-tot, sus concentraciones fueron relativamente homog谷neas en la mayor赤a de las estaciones. Sin embargo, tres estaciones presentaron disminuciones de tipo exponencial caracter赤sticas de procesos de degradaci車n diagen谷tica de primer orden. Valores de la raz車n C:N, entre 7 a 10, indican, en una primera aproximaci車n, que la procedencia de la materia org芍nica del s