Miguel A. Goñi

Biogeochemical characterization of carbon sources in the Strickland and Fly rivers, Papua New Guinea

the organic and inorganic composition of particulate and dissolved carbon at several lowland sites in the Fly and Strickland rivers and on the Strickland River floodplain. Isotopic, elemental, and biomarker results suggest that organic carbon in the Strickland River was more degraded than in the Fly River, with a greater input of ancient organics from upland sources, and that aquatic production constituted a larger source in the Fly River. Radiocarbon results indicate that all carbon fractions were older in the Strickland than in the Fly and that Strickland floodplain sediments were also depleted in radiocarbon. Collectively, these results suggest that rivers of New Guinea export a comparable amount of particulate organic carbon to the Amazon, with a significant contribution from radiocarbon-depleted sources.

Terrigenous organic matter in sediments from the Fly River delta‐clinoform system (Papua New Guinea)

loadings (0.5–1.0 mg C m 2 ), although several samples from the outer topset region, an area of sediment bypass, were characterized by lower carbon loadings indicative of enhanced carbon losses. Overall, the organic matter in both surface and subsurface sediments appeared to have predominantly a terrigenous origin, with no evidence for dilution and/or replacement by marine carbon. The measured compositions were consistent with contributions from modern vascular plant detritus, aged soil organic matter, and very old or fossil organic matter devoid of recognizable biochemicals.

Soft-Rot Fungal Degradation of Lignin in 2700 Year Old Archaeological Woods

Soft-rot fungal degradation of archaeological wood was investigated by comparing the micromorphological characteristics, elemental compositions and monomeric and dimeric phenols derived from CuO oxidation of lignins in degraded boxwood, maple, juniper and pine woods from Tumulus MM, Turkey, thought to be the ancient tomb to King Midas dated 2700 years before present (BP). Chemical compositions of these soft-rotted archaeological woods were compared to those of modern undegraded counterparts and to those of contemporary white- and brown-rotted woods. The degraded angiosperm woods showed Type 1 (cavity) and Type 2 (erosive) forms of soft-rot, whereas the degraded gymnosperm samples exhibited only Type 1 decay. All soft-rotted woods contained higher weight percentages of ash and nitrogen than their fresh counterparts. Polysaccharides were preferentially attacked by soft-rot fungi as indicated by decreased atomic ratios of hydrogen/carbon in all degraded woods and lower atomic ratios of oxygen/carbon in remnant boxwood, maple, and pine woods. In addition, soft-rot fungi extensively attacked lignin as evidenced by the lower carbon-normalized yields of lignin monomers from most degraded samples. All soft-rotted woods had elevated acid/aldehyde ratios indicative of oxidative microbial degradation of remnant lignin sidechains. Soft-rot degradation resulted in greater carbon cross-linking of the remnant lignin and enrichment of ring-ring dimers in the degraded angiosperm samples, indicating preferential attack of sidechain-linked structures within the lignin polymer. While soft-rot fungi share some degradative characteristics with both white- and brown-rot fungi, the physical and chemical effects of soft-rot degradation are unique

Mississippi Delta mudflow activity and 2005 Gulf hurricanes

Gravity-driven sediment flows can be important mechanisms for transporting sediments and solutes rapidly across continental margins, and therefore may have important impacts on benthic ecosystems and geochemical cycling. Also, infrastructure damage can result from these events, as was the case when mudflow activity during Hurricane Ivan in fall 2004 caused pipeline damage (U.S. Minerals Management Service (MMS) press release on 8 October 2004; http://www.mms.gov/ooc/press/2004/press I 008a.htm).

The effects of wildfire on the sediment yield of a coastal California watershed

The occurrence of two wildfi res separated by 31 yr in the chaparral-dominated Arroyo Seco watershed (293 km 2 ) of California provides a unique opportunity to evaluate the effects of wildfi re on suspended-sediment yield. Here, we compile discharge and suspended-sediment sampling data from before and after the fi res and show that the effects of the postfi re responses differed markedly. The 1977 Marble Cone wildfi re was followed by an exceptionally wet winter, which resulted in concentrations and fl uxes of both fi ne and coarse suspended sediment that were ~35 times greater than average (sediment yield during the 1978 water year was 11,000 t/km 2 /yr). We suggest that the combined 1977–1978 fi re and fl ood had a recurrence interval of greater than 1000 yr. In contrast, the 2008 Basin Complex wildfi re was followed by a drier than normal year, and although suspended-sediment fl uxes and concentrations were signifi cantly elevated compared to those expected for unburned conditions, the sediment yield during the 2009 water year was less than 1% of the post–Marble Cone wildfi re yield. After the fi rst postfi re winters, sediment concentrations and yield decreased with time toward prefi re relationships and continued to have signifi cant rainfall dependence. We hypothesize that the differences in sediment yield were related to precipitationenhanced hillslope erosion processes, such as rilling and mass movements. The millennialscale effects of wildfi re on sediment yield were explored further using Monte Carlo simulations, and these analyses suggest that infrequent wildfi res followed by flincrease long-term suspended-sediment fl markedly. Thus, we suggest that the current approach of estimating sediment yield from sediment rating curves and discharge data— without including periodic perturbations from wildfi res—may grossly underestimate actual sediment yields.

Changes in wind‐driven upwelling during the last three centuries: Interocean teleconnections

based U37 0 paleothermometer yielded high-resolution records of sea surface temperatures (SST) from 1700 to 2000 AD. The trends in the U37 0 index reveal steady SST increases of 1 to 2C at both sites since the end of the Little Ice Age. Higher-frequency changes in SST indicate a decoupling in the relative intensity of wind-driven upwelling at the two sites. Periods of enhanced upwelling in Guaymas correspond to periods of decreased upwelling in Cariaco (and vice versa). We propose that these contrasts reflect regional differences in the upwelling response of upwelling to changes in the positioning of the Inter-Tropical Convergence Zone (ITCZ) and the Subtropical High (SH) under current climate conditions. Citation: Goni, M. A., R. C.

Reexposure and advection of 14C‐depleted organic carbon from old deposits at the upper continental slope

represents an additional source of 14 C‐depleted organic carbon supplied to the ocean, in parallel with the weathering of fossil organic carbon delivered by rivers from land. To understand the dynamics and implications of this reexposure at the shelf edge, a biogeochemical study was carried out in the Gulf of Lions (Mediterranean Sea) where erosive processes, driven by shelf dense water cascading, are currently shaping the seafloor at the canyon heads. Mooring lines equipped with sediment traps and current meters were deployed during the cascading season in the southwestern canyon heads, whereas sediment cores were collected along the sediment dispersal system from the prodelta regions down to the canyon heads. Evidence from grain‐size, X‐radiographs and 210 Pb activity indicate the presence in the upper slope of a shelly‐coarse surface stratum overlying a consolidated deposit. This erosive discontinuity was interpreted as being a result of dense water cascading that is able to generate sufficient shear stress at the canyon heads to mobilize the coarse surface layer, eroding the basal strata. As a result, a pool of aged organic carbon (D 14 C= −944.5 ± 24.7‰; mean age 23,650 ± 3,321 ybp) outcrops at the modern seafloor and is reexposed to the contemporary carbon cycle. This basal deposit was found to have relatively high terrigenous organic carbon (lignin = 1.48 ± 0.14 mg/100 mg OC), suggesting that this material was deposited during the last low sea‐level stand. A few sediment trap samples showed anomalously depleted radiocarbon concentrations (D 14 C= −704.4 ± 62.5‰) relative to inner shelf (D 14 C= −293.4 ± 134.0‰), mid‐shelf (D 14 C= −366.6 ± 51.1‰), and outer shelf (D 14 C= −384 ± 47.8‰) surface sediments. Therefore, although the major source of particulate material during the cascading season is resuspended shelf deposits, there is evidence that this aged pool of organic carbon can be eroded and laterally advected downslope.

Impact of Hurricanes Katrina and Lili on the Inner Shelf of the Mississippi-Atchafalaya Delta

Box cores collected on the Louisiana continental shelf immediately following Hurricanes Lili and Katrina allow comparison of sediment event layer formation on the actively accreting Mississippi delta adjacent to Southwest Pass (Katrina) and the Atchafalaya delta (Lili). Post-Katrina box core sites in water depths of 25 m, post-Katrina cores display event layer deposition 1–25 cm thick above the incision surface: post-Lili cores from the Atchafalaya show similar thicknesses dependent on proximity to the storm path, but also extending into shallower water (shallowest station sampled was 4 m).

Occurrence and sources of polar lipid tracers in sediments from the Shatt al-Arab River of Iraq and the northwestern Arabian Gulf.

Shallow surface sediment samples from the southern part of the Shatt al-Arab River estuary of Iraq and the northwestern Arabian Gulf were analyzed for polar lipid compounds including n-alkanoic acids, n-alkanols, steroids and triterpenoids. The results showed that the n-alkanoic acids, methyl n-alkanoates and n-alkanols typically ranged from C12 to C32 with total concentrations of 3.2 to 108.2 μg g(-1)dwt sample, from C12 to C30 with totals of 1.1 to 18.9 μg g(-1)dwt sample, and from C14 to C32 at 1.8 to 112.6 μg g(-1)dwt sample, respectively. Steroids and triterpenoids were detected and included stenols, stanols, stenones, stanones, tetrahymanol, tetrahymanone and extended ββ-hopanes. The total steroid concentrations ranged from 2.8 to 78.4 μg g(-1)dwt sample, whereas the triterpenoids varied from 0.05 to 7.6 μg g(-1)dwt sample. The simple regression analysis of the results and the spatial distribution patterns of the identified organic tracers indicated that the inter-compound relationships were related mainly to their major sources. Cluster analysis and principal component analysis (PCA) of data set showed that the sampling sites are similar. These sources were allochthonous (terrestrial vegetation), autochthonous (plankton residues and bacteria in the sediments) and anthropogenic (sewage and petroleum).

Organic matter compositions of rivers draining into Hudson Bay: Present‐day trends and potential as recorders of future climate change

Concentrations and compositions of particulate and dissolved organic carbon (POC and DOC, respectively) and aromatic compounds including lignin were analyzed in water samples from 17 rivers flowing into Hudson Bay, northern Canada. These rivers incorporate basins to the south with no permafrost to basins in the north with continuous permafrost, and dominant vegetation systems that include Boreal Forest, the Hudson Plains, Taiga Shield, and Tundra. Major latitudinal trends in organic carbon and lignin concentrations and compositions were evident, with both DOC and dissolved lignin concentrations dominating over their particulate counterparts and exhibiting significant correlations with total dissolved and suspended solids, respectively. The composition of lignin reaction products in terms of the syringyl, cinnamyl, and vanillyl compositions indicate mixed sources of vascular land plant-derived organic carbon, with woody gymnosperms contributions dominating in the southern river basins whereas nonwoody angiosperm sources were more important in the most northerly rivers. The composition of nonlignin aromatic compounds, which provides a tracer for nonvascular plant contributions, suggests stronger contributions from Sphagnum mosses to dissolved organic matter in rivers below the tree line, including those with large peat bogs in their basins. Acid/aldehyde ratios of the lignin products together with Δ14C data for DOC in selected rivers indicate that DOC has generally undergone greater alteration than POC. Interestingly, several northern rivers exhibited relatively old DOC according to the Δ14C data suggesting that either old DOC is being released from permafrost or old DOC survives river transport in these rivers.