Organic carbon isotope ratios (δ 13 C) of Arctic Amerasian Continental shelf sediments

Abstract

Organic matter origins are inferred from carbon isotope ratios (d 13 C) in recent continental shelf sediments and major rivers from 465 locations from the north Bering-Chukchi-East Siberian-Beaufort Sea, Arctic Amerasia. Generally, there is a cross-shelf increase in d 13 C, which is due to progressive increased contribution seaward of marine-derived organic carbon to surface sediments. This conclusion is supported by the correlations between sediment d 13 C, OC/N, and d 15 N. The sources of total organic carbon (TOC) to the Amerasian margin sediments are primarily from marine water-column phytoplankton and terrigenous C 3 plants constituted of tundra taiga and angiosperms. In contrast to more temperate regions, the source of TOC from terrigenous C 4 and CAM plants to the study area is probably insignificant because these plants do not exist in the northern high latitudes. The input of carbon to the northern Alaskan shelf sediments from nearshore kelp community (Laminaria solidungula) is generally insignificant as indicated by the absence of high sediment d 13 C values (±16.5 to ±13.6½) which are typical of the macrophytes. Our study suggests that the isotopic composition of sediment TOC has potential application in reconstructing temporal changes in delivery and accumulation of organic matter resulting from glacial±interglacial changes in sea level and environments. Furthermore, recycling and advection of the extensive deposits of terrestrially derived organic matter from land, or the wide Amerasian margin, could be a mechanism for elevating total CO 2 and pCO 2 in the Arctic Basin halocline.

Distribution and sources of organic matter in surficial sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C / N ratios

“…Identifying the source materials in the sediment is essential to understand the mechanisms of C cycling in the marine environment. Based on the difference of the values among the sources, stable C and nitrogen (N) isotope ratios and C/N have been widely used to elucidate the source and fate of organic matter in the 4 marine environment (Hedges and Parker, 1976;Peters et al, 1978;Fry and Sherr, 1984;Wada et al, 1987;Thornton and McManus, 1994;Ogawa and Ogura, 1997;Middelburg and Nieuwenhuize, 1998;Tyson, 1995;Naidu et al, 2000;Cloern et al, 2002;Gordon and Goñi, 2003;Goñi et al, 2003). However, it should be noted that C and N isotopic compositions and C/N ratios in marine and riverine particulate organic matter (POM) often vary seasonally (Altabet et al, 1991;Mook and Tan, 1991;Nakatsuka et al, 1992;Tyson, 1995;Kendall et al, 2001;Nakanishi and Minagawa, 2003).…”

Transformation of terrestrial organic matter along thermokarst-affected permafrost coasts in the Arctic

“…C signatures (Lamb et al, 2006;Naidu et al, 2000). Stable carbon isotopes are indicative of the initial contribution of different plant species and plant components and therefore its terrestrial origin (Gundelwein et al, 2007).…”

“…However, all marine sediments and OC in the water column at water depths less than 30 m can be affected by wave erosion, resuspension or ice-scouring, and thus long-term accumulation of OM may be limited Macdonald et al, 2015;Reimnitz et al, 1987;Vonk et al, 2012). Further offshore, the contribution of autochtonous sources increases gradually along the narrow shelf and towards the Alaskan Beaufort Sea and Chukchi Sea, where autochtonous production dominates (Naidu et al, 2000). However, terrestrial OM can even be transported to the shelf edge and beyond into deep water basins, where it can be stored for millennia (Belicka et al, 2002;Forest et al, 2007;Letscher et al, 2013;O'Brien et al, 2006).…”

Stable carbon and nitrogen isotopes and elemental composition and origin of organic matter from the Euphrates, Injana and Dibdibba formations in Iraq: discrimination between marine and terrestrial environments

“…Car bon iso topic val ues are sim i lar in the Injana and Dibdibba for ma tions, and dif fer from that of the Euphrates Formation C/N ra tios, and d 13 C and d 15 N val ues have been widely used as ef fec tive mark ers to es ti mate the rel a tive pro por tions of terrigenous and ma rine or ganic mat ter in coastal and mar ginal sed i ments (Meyers, 1997;Naidu et al, 2000;Stein and Macdon ald, 2004). River net works of tightly linked with the landscape played an es sen tial role in trans port ing and de pos it ing sed i ment of the Injana and Dibdibba for ma tions, with land plants sup ply ing the or ganic mat ter.…”