TY - JOUR
T1 - Compositional and biogeochemical variations of sediments across the terrestrial-marine continuum of the Baker-Martínez fjord system (Chile, 48°S)
AU - Rebolledo, Lorena
AU - Bertrand, Sebastien
AU - Lange, Carina B.
AU - Tapia, Fabian J.
AU - Quiroga, Eduardo
AU - Troch, Matthias
AU - Silva, Nelson
AU - Cárdenas, Paola
AU - Pantoja, Silvio
N1 - Funding Information:
We thank Dr. Marcelo Gutiérrez (UdeC) for kindly providing the Jorge Montt sediment samples, and Dr. Juan Placencia (UCSC) for sharing some of the CF20 samples used in this study. Paola Reinoso and Francisco Gallardo (PUCV) are acknowledged for their help in collecting the CF14 sediment samples for bulk organic geochemical analysis. We also thank Dr. Roberto Rodríguez (UdeC) for his help with the identification of vascular plants from the Tortel area, and Víctor Acuña (COPAS Sur-Austral) and Alejandro Ávila (IDEAL Center) for n-alkanes and biogenic opal analyses, respectively. We are grateful to the captain and crew of the L/C Sur-Austral for their help during sample collection, and to the CIMAR program (Cruceros de Investigación Marina en Áreas Remotas; Marine Research Cruises in Remote Areas). The research presented here was funded by the Center for Oceanographic Research COPAS Sur-Austral ( CONICYT PIA PFB31 and CONICYT PIA APOYO CCTE AFB170006 ) and by UGent BOF project HYDROPROX ( 01N02216 ). Partial support from the IDEAL Center (grant FONDAP 15150003 to CBL and LR ), and CONA projects C14F 08-13 and C20F 14-06 (to NS) is also acknowledged. The authors wish to thank Rolf Kilian and an anonymous reviewer for their valuable comments.
Funding Information:
We thank Dr. Marcelo Guti?rrez (UdeC) for kindly providing the Jorge Montt sediment samples, and Dr. Juan Placencia (UCSC) for sharing some of the CF20 samples used in this study. Paola Reinoso and Francisco Gallardo (PUCV) are acknowledged for their help in collecting the CF14 sediment samples for bulk organic geochemical analysis. We also thank Dr. Roberto Rodr?guez (UdeC) for his help with the identification of vascular plants from the Tortel area, and V?ctor Acu?a (COPAS Sur-Austral) and Alejandro ?vila (IDEAL Center) for n-alkanes and biogenic opal analyses, respectively. We are grateful to the captain and crew of the L/C Sur-Austral for their help during sample collection, and to the CIMAR program (Cruceros de Investigaci?n Marina en ?reas Remotas; Marine Research Cruises in Remote Areas). The research presented here was funded by the Center for Oceanographic Research COPAS Sur-Austral (CONICYT PIA PFB31 and CONICYT PIA APOYO CCTE AFB170006) and by UGent BOF project HYDROPROX (01N02216). Partial support from the IDEAL Center (grant FONDAP 15150003 to CBL and LR), and CONA projects C14F 08-13 and C20F 14-06 (to NS) is also acknowledged. The authors wish to thank Rolf Kilian and an anonymous reviewer for their valuable comments.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2019/5/1
Y1 - 2019/5/1
N2 - The Baker-Martínez fjord system (Chile, 48°S) is a transitional environment between the terrestrial ecosystems of Patagonia and the SE Pacific Ocean. This unique setting makes it an ideal system to evaluate land-ocean gradients in sediment composition and in a range of biogeochemical variables. Here, we studied the composition and organic geochemistry of surface sediments deposited in the Baker-Martínez fjord system to assess spatial changes in sediment properties and identify the best tracers of terrestrial input. We determined concentrations in biogenic opal, organic carbon, calcium carbonate, and lithogenic particles, and we measured diatom abundance, bulk elemental and isotopic organic geochemistry, and n-alkanes distribution, on a series of surface sediment samples distributed along two proximal-to-distal transects (one in the Martínez Channel and a second one in the Baker Channel). Results reveal clear proximal-to-distal trends in the proportion of freshwater diatoms and in the fraction of organic carbon of terrestrial origin calculated from the bulk organic δ13C measurements. Diatoms are particularly sensitive to freshwater input in proximal environments, whereas bulk organic geochemistry better reflects terrestrial input over long distances across the fjord system. Other terrestrial proxies frequently used in the literature, such as the N/C ratio and the n-alkane-based terrestrial/aquatic ratio, did not show clear variations with distance from the fjord head. Our results suggest that the isotopic composition of bulk organic matter (δ13Corg) and the relative proportion of diatoms of freshwater origin are the best-suited proxies to estimate past changes in terrestrial input from fjord sediment archives, irrespective of the glacial status of the fjord and its watershed.
AB - The Baker-Martínez fjord system (Chile, 48°S) is a transitional environment between the terrestrial ecosystems of Patagonia and the SE Pacific Ocean. This unique setting makes it an ideal system to evaluate land-ocean gradients in sediment composition and in a range of biogeochemical variables. Here, we studied the composition and organic geochemistry of surface sediments deposited in the Baker-Martínez fjord system to assess spatial changes in sediment properties and identify the best tracers of terrestrial input. We determined concentrations in biogenic opal, organic carbon, calcium carbonate, and lithogenic particles, and we measured diatom abundance, bulk elemental and isotopic organic geochemistry, and n-alkanes distribution, on a series of surface sediment samples distributed along two proximal-to-distal transects (one in the Martínez Channel and a second one in the Baker Channel). Results reveal clear proximal-to-distal trends in the proportion of freshwater diatoms and in the fraction of organic carbon of terrestrial origin calculated from the bulk organic δ13C measurements. Diatoms are particularly sensitive to freshwater input in proximal environments, whereas bulk organic geochemistry better reflects terrestrial input over long distances across the fjord system. Other terrestrial proxies frequently used in the literature, such as the N/C ratio and the n-alkane-based terrestrial/aquatic ratio, did not show clear variations with distance from the fjord head. Our results suggest that the isotopic composition of bulk organic matter (δ13Corg) and the relative proportion of diatoms of freshwater origin are the best-suited proxies to estimate past changes in terrestrial input from fjord sediment archives, irrespective of the glacial status of the fjord and its watershed.
KW - Carbon stable isotopes
KW - Chilean fjords
KW - Diatoms
KW - Organic geochemistry
KW - Sediment composition
KW - n-alkanes
UR - http://www.scopus.com/inward/record.url?scp=85059349461&partnerID=8YFLogxK
U2 - 10.1016/j.pocean.2018.12.004
DO - 10.1016/j.pocean.2018.12.004
M3 - Article
AN - SCOPUS:85059349461
VL - 174
SP - 89
EP - 104
JO - Progress in Oceanography
JF - Progress in Oceanography
SN - 0079-6611
ER -