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2013
Harada, N, Ninnemann U, Lange CB, Marchant ME, Sato M, Ahagon N, Pantoja S.  2013.  Deglacial–Holocene environmental changes at the Pacific entrance of the Strait of Magellan. Palaeogeography, Palaeoclimatology, Palaeoecology. 375:125-135.   10.1016/j.palaeo.2013.02.022   Abstract

We show environmental and nitrogen cycle changes between 13 and 2.5 kyr BP (from the latest deglaciation to the Holocene) based on biogeochemical records in a sediment core from the Pacific entrance of the Strait of Magellan. Organic carbon, total nitrogen, and C37 alkenone contents were low during 13–9 kyr BP but increased rapidly at 8 kyr BP. The relative contribution of tetra-unsaturated C37 alkenone, used as a salinity proxy, suggests low salinity during 13–9 kyr BP changing to high salinity at 8 kyr BP. Planktic foraminifer data showed that Globigerina bulloides was more abundant during the deglacial–early Holocene than in the mid–late Holocene, whereas abundances of Neogloboquadrina pachyderma showed the opposite pattern. This evidence plus biogenic opal data suggest that sea level rose, surface waters were relatively stratified, and in situ productivity was low except for organisms with opal tests from 13 to 9 kyr BP. Bulk δ15N values were high (9–11‰) relative to present-day values during the deglacial–early Holocene, with consistently lower values (~ 7‰) after ~ 8 kyr BP. These relatively high δ15N values most likely reflect increased nutrient utilization in the Southern Ocean, which resulted in high-δ15N water being advected to the Patagonian fjords, although local denitrification caused by the delivery of copious terrestrial materials and organic matter to the ocean cannot be ruled out. By ~ 8 kyr BP continental influences and surface stratification were reduced and characteristic Holocene conditions were established, with increased influence of Southern Ocean water in the western Strait of Magellan. Sea surface temperatures showed millennial-scale changes during the deglaciation and early Holocene, with relatively warm temperatures (11–12 °C) corresponding to the Antarctic counterpart of the Younger Dryas cooling event of the Northern Hemisphere. The longer term pattern (~ 10 kyr time scale) in alkenone-derived sea surface temperatures generally follows orbital changes in insolation during austral spring, suggesting a controlling influence of austral spring insolation on southern Patagonian climate.

2012
Sanchez, GE, Lange CB, Gonzalez HE, Vargas G, Munoz P, Cisternas C, Pantoja S.  2012.  Siliceous microorganisms in the upwelling center off Concepcion, Chile (36 degrees S): Preservation in surface sediments and downcore fluctuations during the past similar to 150 years. Progress in Oceanography. 92-95:50-65.   10.1016/j.pocean.2011.07.014   AbstractWebsite

We analyzed the temporal patterns of siliceous microorganisms in the water column and their representation in the underlying surface sediments between September 2002 and November 2005, at a fixed station on the shelf off Concepcion, Chile (Station 18, 36 degrees 30.80'S and 73 degrees 07.75'W), connecting our results to instrumental records of temperature, salinity, coastal upwelling and freshwater input. The goals of the study were to understand the seasonal representation of siliceous microorganisms in surface sediments and to evaluate the use of this information in the interpretation of past climatic/oceanographic conditions in the area. The implications of seasonal and preservational biases are discussed. Additionally, a 30-cm core collected at the same site and spanning the last similar to 150 years of sedimentation was also studied in order to provide a record of historical siliceous productivity changes. Firstly, the analyses focused on diatoms since they were numerically the most prominent microorganisms in the water column and the surface sediments, independent of season and year. In both settings, maxima of the key diatom genera Chaetoceros and Skeletonema coincided with the spring-summer upwelling period. For the autumn-winter non-upwelling period, significant plankton-sediment discrepancies were observed, with enrichment of moderately robust taxa in the sediments, as well as freshwater diatoms and phytoliths tracing the increased river discharges in winter. Secondly, the downcore analysis revealed a marked decrease in total diatom accumulation rates since the late 19th and throughout the 20th century, which was accompanied by increasing concentrations of lithogenic particles and freshwater diatoms. An alkenone-based sea surface temperature reconstruction in the same core (past similar to 150 years) and instrumental data show that these changes occurred simultaneously with a general trend of increasing temperatures in the upwelling area off Concepcion. Taken together, these signals suggest an intensified influence of ENSO-like variability in the ocean-climate system off central-southern Chile. (C) 2011 Elsevier Ltd. All rights reserved.

Munoz, P, Dezileau L, Cardenas L, Sellanes J, Lange CB, Inostroza J, Muratli J, Salamanca MA.  2012.  Geochemistry of trace metals in shelf sediments affected by seasonal and permanent low oxygen conditions off central Chile, SE Pacific (similar to 36 degrees S). Continental Shelf Research. 33:51-68.   10.1016/j.csr.2011.11.006   AbstractWebsite

Trace metals (Cd, U, Co, Ni, Cu, Ba, Fe, Mn), total organic carbon (TOC) and C and N stable isotope signatures (delta C-313 and delta N-15) were determined in short sediments cores from the inner and outer shelf off Concepcion, Chile (similar to 36 degrees S). The objectives were to establish the effect of environmental conditions on trace metal distributions at two shelf sites, one affected by seasonal oxygenation and the other by permanent low oxygen conditions due to the presence of the oxygen minimum zone (OMZ). We evaluate trace metals as proxies of past changes in primary productivity and the bottom water oxygen regime. Concentrations of pore water sulfides and NH4+ were also measured as indicators of the main diagenetic pathways at each site. Our results for the inner shelf (seasonal suboxia) suggest that the oxidative state of the sediments responds to seasonal pulses of organic matter and that seasonal oxygenation develops during high and low primary productivity in the water column. Here, positive fluxes (to the water column) estimated from pore water concentrations of several elements were observed (Ba, Co, Ni, Fe and Mn). The less reduced environment at this site produces authigenic enrichment of Cu associated with the formation of oxides in the oxic surface sediment layer, and the reduction of U within deeper sediment sections occur consistently with negative estimated pore water fluxes. In the outer shelf sediments (permanent suboxia, OMZ site), negative fluxes (to the sediment) were estimated for all elements, but these sediments showed authigenic enrichments only for Cd, Cu and U. The short oxygenation period during the winter season did not affect the accumulation of these metals on the shelf. The distribution of Cu, Cd and U have been preserved within the sediments and the authigenic accumulation rates estimated showed a decrease from the deep sections of the core to the surface sediments. This could be explained by a gradual decrease in the strength of the OMZ in the last 100 years, in combination with periods of strong oxygenations during El Nino events. (C) 2011 Elsevier Ltd. All rights reserved.

Bertrand, S, Hughen KA, Lamy F, Stuut JBW, Torrejon F, Lange CB.  2012.  Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield. Climate of the Past. 8:519-534.   10.5194/cp-8-519-2012   AbstractWebsite

Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided into three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we suggest that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the North Patagonian Andes.

2011
Caniupan, M, Lamy F, Lange CB, Kaiser J, Arz H, Kilian R, Urrea OB, Aracena C, Hebbeln D, Kissel C, Laj C, Mollenhauer G, Tiedemann R.  2011.  Millennial-scale sea surface temperature and Patagonian Ice Sheet changes off southernmost Chile (53 degrees S) over the past similar to 60 kyr. Paleoceanography. 26   10.1029/2010pa002049   AbstractWebsite

Glacial millennial-scale paleoceanographic changes in the Southeast Pacific and the adjacent Southern Ocean are poorly known due to the scarcity of well-dated and high resolution sediment records. Here we present new surface water records from sediment core MD07-3128 recovered at 53 degrees S off the Pacific entrance of the Strait of Magellan. The alkenone-derived sea surface temperature (SST) record reveals a very strong warming of ca. 8 C over the last Termination and substantial millennial-scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope (delta(18)O) record of Neogloboquadrina pachyderma (sin.). The timing and structure of the Termination and some of the millennial-scale SST fluctuations are very similar to those observed in the well-dated SST record from ODP Site 1233 (41 degrees S) and the temperature record from Drowning Maud Land Antarctic ice core supporting the hemispheric-wide Antarctic timing of SST changes. However, differences in our new SST record are also found including a long-term warming trend over Marine Isotope Stage (MIS) 3 followed by a cooling toward the Last Glacial Maximum (LGM). We suggest that these differences reflect regional cooling related to the proximal location of the southern Patagonian Ice Sheet and related meltwater supply at least during the LGM consistent with the fact that no longer SST cooling trend is observed in ODP Site 1233 or any SST Chilean record. This proximal ice sheet location is documented by generally higher contents of ice rafted debris (IRD) and tetra-unsaturated alkenones, and a slight trend toward lighter planktonic delta(18)O during late MIS 3 and MIS 2.

Aracena, C, Lange CB, Iriarte JL, Rebolledo L, Pantoja S.  2011.  Latitudinal patterns of export production recorded in surface sediments of the Chilean Patagonian fjords (41-55 degrees S) as a response to water column productivity. Continental Shelf Research. 31:340-355.   10.1016/j.csr.2010.08.008   AbstractWebsite

The Chilean Patagonian fjords region (41-56 degrees S) is characterized by highly complex geomorphology and hydrographic conditions, and strong seasonal and latitudinal patterns in precipitation, freshwater discharge, glacier coverage, and light regime; all of these directly affect biological production in the water column. In this study, we compiled published and new information on water column properties (primary production, nutrients) and surface sediment characteristics (biogenic opal, organic carbon, molar C/N, bulk sedimentary delta(13)C(org)) from the Chilean Patagonian fjords between 41 degrees S and 55 degrees S, describing herein the latitudinal pattern of water column productivity and its imprint in the underlying sediments. Based on information collected at 188 water column and 118 sediment sampling sites, we grouped the Chilean fjords into four main zones: Inner Sea of Chiloe (41 degrees to similar to 44 degrees S), Northern Patagonia (44 degrees to similar to 47 degrees S), Central Patagonia (48-51 degrees S), and Southern Patagonia (Magellan Strait region between 52 degrees and 55 degrees S). Primary production in the Chilean Patagonian fjords was the highest in spring-summer, reflecting the seasonal pattern of water column productivity. A clear north-south latitudinal pattern in primary production was observed, with the highest average spring and summer estimates in the Inner Sea of Chiloe (2427 and 5860 mg C m(-2) d(-1)) and Northern Patagonia (1667 and 2616 mg C m(-2) d(-1)). This pattern was closely related to the higher availability of nutrients, greater solar radiation, and extended photoperiod during the productive season in these two zones. The lowest spring value was found in Caleta Tortel, Central Patagonia (91 mg C m(-2) d(-1)), a site heavily influenced by glacier meltwater and river discharge loaded with glacial sediments. Biogenic opal, an important constituent of the Chilean fjord surface sediments (Si(OPAL) similar to 1-13%), reproduced the general north-south pattern of primary production and was directly related to water column silicic acid concentrations. Surface sediments were also rich in organic carbon content and the highest values corresponded to locations far away from glacier influence, sites within fjords, and/or semi-enclosed and protected basins, reflecting both autochthonous (water column productivity) and allochthonous sources (contribution of terrestrial organic matter from fluvial input to the fjords). A gradient was observed from the more oceanic sites to the fjord heads (west-east) in terms of bulk sedimentary delta(13)C(org) and C/N ratios; the more depleted (delta(13)C(org) -26 parts per thousand) and higher C/N (23) values corresponded to areas close to rivers and glaciers. A comparison of the Chilean Patagonian fjords with other fjord systems in the world revealed high variability in primary production for all fjord systems as well as similar surface sediment geochemistry due to the mixing of marine and terrestrial organic carbon. (C) 2010 Elsevier Ltd. All rights reserved.

Rebolledo, L, Gonzalez HE, Munoz P, Iriarte JL, Lange CB, Pantoja S, Salamanca M.  2011.  Siliceous productivity changes in Gulf of Ancud sediments (42 degrees S, 72 degrees W), southern Chile, over the last similar to 150 years. Continental Shelf Research. 31:356-365.   10.1016/j.csr.2010.06.015   AbstractWebsite

We evaluated changes in siliceous export production and the source of organic matter preserved in sediment core MD07-3109H recovered from the Gulf of Ancud, Chiloe Inner Sea (42 degrees S, 72 degrees W, water column depth: 328 m), southern Chile. We analyzed the abundance of siliceous microfossils (diatoms, silicoflagellates, sponge spicules, Chrysophyte cysts, phytoliths), geochemical proxies (weight percent silicon %Si(OPAL), organic carbon, total nitrogen. C/N molar), and sediment stable isotopes (delta(13)C(org), delta(15)N). Chronology based on (210)Pb and (14)C provided an accumulated age of 144 years at the base of the core. Sediments of core MD07-3109H are predominantly marine in origin, averaging delta(13)C(org)=-20.75 parts per thousand+0.82, delta(15)N=8.7 +/- 0.35 parts per thousand, and C/N =8.76 +/- 0.36. Marine diatoms compose 94% of the total assemblage of siliceous microfossils. Our record of productivity based on the mass accumulation rates of organic carbon, total nitrogen, Si(OPAL), and total diatoms showed high values between 1863 and 1869 AD followed by a declining trend until 1921 AD, a transition period from 1921 to 1959 AD with fluctuating values, and a clear decreasing pattern from 1960 AD to the present. This marked reduction in productivity was associated with decreased precipitation and Puelo River streamflow (41 degrees S), as well as a warmer and more stratified water column, especially since the 1980s. (C) 2010 Elsevier Ltd. All rights reserved.

Diaz-Ochoa, JA, Pantoja S, De Lange GJ, Lange CB, Sanchez GE, Acuna VR, Munoz P, Vargas G.  2011.  Oxygenation variability in Mejillones Bay, off northern Chile, during the last two centuries. Biogeosciences. 8:137-146.   10.5194/bg-8-137-2011   AbstractWebsite

The Peru Chile Current ecosystem is characterized by high biological productivity and important fisheries. Although this system is likely to be severely affected by climate change, its response to current global warming is still uncertain. In this paper, we analyze 10-166 year-old sediments in two cores collected from Mejillones Bay, an anoxic sedimentary setting favorable for the preservation of proxies. Based on a 166-year chronology, we used proxies of bottom-water oxygenation (Mo, V, S, and the (lycopane+n-C(35))/n-C(31) ratio) and surface water productivity (biogenic opal, counts of diatom valves, biogenic Ba, organic carbon, and chlorins) to reconstruct environmental variations in Mejillones Bay. During the last two centuries, a shift took place in the coastal marine ecosystem of Bahia Mejillones at decadal scales. This shift was characterized by intense ENSO-like activity, large-scale fluctuations in biological export productivity and bottom water oxygenation, and increased eolian activity (inferred from Ti/Al and Zr/Al). This short-term variability was accompanied by a gradual increase of sulfidic conditions that has intensified since the early 1960s.

2010
Contreras, S, Lange CB, Pantoja S, Lavik G, Rincon-Martinez D, Kuypers MMM.  2010.  A rainy northern Atacama Desert during the last interglacial. Geophysical Research Letters. 37   10.1029/2010gl045728   AbstractWebsite

The response of the northern extension of the Atacama Desert and the Peruvian upwelling system to climate conditions during the Last Interglacial ([LIG]; similar to 125kyr ago) was tracked using molecular fossils of marine and terrestrial organisms preserved in Peruvian shelf sediments. High resolution records of ODP Site 1229 (past 145 kyr) indicated that warmer and wetter conditions (rainfall and river runoff) along the coast occurred during the LIG, when global temperatures were comparable or even higher than today. A similar to 3 degrees C warming of surface waters, enhanced water column stratification, rainfall and river runoff were associated with low primary productivity and a similar to 1.5 degrees C decrease in the temperature gradient across the Equatorial Pacific (i.e., weak Walker circulation), suggesting a prolonged El Nino-like response of the tropical Pacific during the LIG. In contrast, the late Holocene ([LH] last 3 kyr) was characterized by colder surface waters, higher export and primary productivity, and a drier climate. Citation: Contreras, S., C. B. Lange, S. Pantoja, G. Lavik, D. Rincon-Martinez, and M. M. M. Kuypers (2010), A rainy northern Atacama Desert during the last interglacial, Geophys. Res. Lett., 37, L23612, doi: 10.1029/2010GL045728.

2009
Montecino, V, Lange CB.  2009.  The Humboldt Current System: Ecosystem components and processes, fisheries, and sediment studies. Progress in Oceanography. 83:65-79.   10.1016/j.pocean.2009.07.041   AbstractWebsite

In the Humboldt Current System (HCS), biological and non-biological components, ecosystem processes, and fisheries are known to be affected by multi-decadal, inter-annual, annual, and intra-seasonal scales. The interplay between atmospheric variability, the poleward undercurrent, the shallow oxygen minimum zone (OMZ), and the fertilizing effect of coastal upwelling and overall high primary production rates drive bio-physical interactions, the carbon biomass, and fluxes of gases and particulate and dissolved matter through the water column. Coastal upwelling (permanent and seasonally modulated off Peru and northern Chile, and markedly seasonal between 30 degrees S and 40 degrees S) is the key process responsible for the high biological productivity in the HCS. At present, the western coast of South America produces more fish per unit area than any other region in the world ocean (i.e. similar to 7.5 x 10(6) t of anchoveta were landed in 2007). Climate changes on different temporal scales lead to alterations in the distribution ranges of anchoveta and sardine populations and shifts in their dominance throughout the HCS. The factors affecting the coastal marine ecosystem that reverberate in the fisheries are crucial from a social perspective. since the economic consequences of mismanagement can be severe. Fish remains are often well-preserved in sediment settings under the hypoxic conditions of the OMZ off Peru and Chile, and reveal multi-decadal variability and centennial-scale changes in fish populations. Sediment studies from the Chilean continental margin encompassing the last 20,000 years of deposition reveal changes in sub-surface conditions in the HCS during deglaciation, interpreted to include: a major reorganization of the OMZ; a deglacial increase in denitrification decoupled from local marine productivity; and higher deglacial and Holocene paleoproductivities compared to the Last Glacial Maximum in central-south Chile (35-37 degrees S) while this scheme is reversed for north-central Chile. Multi-scale, interdisciplinary approaches and focused research groups are needed to understand air-sea interactions, plankton dynamics, biomass removal by fisheries, and the transformation and fluxes of matter across the different HCS components. In this paper, we present a multidisciplinary synthesis of the HCS that covers its physics, atmosphere, primary and secondary production, medium and high trophic levels, fisheries including management aspects, and relevant sedimentary studies. (C) 2009 Elsevier Ltd. All rights reserved.

Caniupan, M, Villasenor T, Pantoja S, Lange CB, Vargas G, Munoz P, Salamanca M.  2009.  Temporal changes in phytoplankton productivity over the last similar to 200 years recorded from Mejillones Bay laminated sediments. Revista Chilena De Historia Natural. 82:83-96. AbstractWebsite

We analyzed the contents of total organic carbon, biogenic opal, chlorins, and alkenones (as productivity proxies) from a laminated sediment core recovered within Bahia Mejillones, northern Chile, in order to reconstruct recent temporal changes in phytoplankton productivity. Physical parameters (water content, dry bulk density, magnetic Susceptibility, X-radiography, and grey scale intensity) were also used to characterize the sediments. A sedimentation rate of 0.18 cm year(-1) (based on (210)Pb measurements) was determined for the core (Core 3; 23 degrees 03' S, 70 degrees 27' W), which was recovered with a box-corer (water column depth: 80 in). By extrapolating this sedimentation rate to the base of the core, it yielded a total age of similar to 223 years. The sediments were characterized by a succession of light and dark millimetre-thick laminae, which differed ill both physical properties and composition; the denser dark laminae had less water content and represented periods of increased phytoplankton productivity, whereas the less dense, light laminae had higher water content and reflected less productive periods. The good preservation of the laminae, the absence of structures associated with processes of bioturbation, and the high sedimentary delta(15)N values ((X) over bar = 11.37 parts per thousand) suggest low dissolved oxygen levels in the bay's bottom water during the two centuries of sedimentary deposition reported herein. Our record is divided into two large productivity intervals: one prior to AD 1820, with lower phytoplankton productivity and relatively warmer conditions, and another from similar to AD 1877 to the present, characterized by higher productivity, high variability, and relatively colder conditions, and accompanied by intensified winds favouring coastal upwelling. We suggest that the productivity of Mejillones Bay since AD 1820 has been strongly dependent on siliceous production and that calcareous primary production has increased since AD 1877.

Diaz-Ochoa, JA, Lange CB, Pantoja S, De Lange GJ, Gutierrez D, Munoz P, Salamanca M.  2009.  Fish scales in sediments from off Callao, central Peru. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 56:1113-1124.   10.1016/j.dsr2.2008.09.015   AbstractWebsite

We study fish scales as a proxy of fish abundance and preservation biases together with phosphorus from fish remains (P(fish)) in a sediment core retrieved off Callao, Peru (12 degrees 1'S, 77 degrees 42'W; water depth = 179 m; core length = 52 cm). We interpret our results as a function of changing redox conditions based on ratios of redox-sensitive trace elements (Cu/Al, Mo/Al, Ni/Al, Zn/Al, V/Al), terrigenous indicators (Fe in clays, Ti, Al), and biogenic proxies (CaCO(3), biogenic opal, total nitrogen, organic carbon, barite Ba). The core covers roughly 700 years of deposition, based on (210)Pb activities extrapolated downcore and (14)C dating at selected intervals. Our fish-scale record is dominated by anchovy (Engraulis ringens) scales followed by hake (Merluccius gayii) scales. The core presented an abrupt lithological change at 17 cm (corresponding to the early 19th century). Above that depth, it was laminated and was more organic-rich (10-15% organic carbon) than below, where the core was partly laminated and less organic-rich (< 10%). The lithological shift coincides with abrupt changes in dry bulk density and in the contents of terrigenous and redox-sensitive trace elements, biogenic proxies, and fish scales. The remarkable increase in redox-sensitive trace elements in the upper 17 cm of the core suggests more reducing conditions when compared with deeper and older horizons, and is interpreted as an intensification of the oxygen minimum zone off Peru beginning in the early 19th century. Higher fish-scale contents and higher P(fish)/P(total) ratios were also observed within the upper 17 cm of the core. The behavior of biogenic proxies and redox-sensitive trace elements was similar; more reduced conditions corresponded to higher contents of CaCO(3), C(org), total nitrogen and fish scales, suggesting that these proxies might convey an important preservation signal. (C) 2008 Elsevier Ltd. All rights reserved.

Sanchez, GE, Sarno D, Montresor M, Siano R, Lange CB.  2009.  Germination of Resting Stages of Diatoms and Dinoflagellates in Marine Sediments From Two Upwelling Areas of Chile. Gayana Botanica. 66:239-255. AbstractWebsite

With the aim to assess germination of diatom and dinoflagellates resting spores we Cultured under laboratory conditions surface sediments collected in the Mejillones Bay (23 degrees S) and off Concepcion (36 degrees S), Chile. These sediments were cultured in the laboratory with a 12:12 h L/D cycle, light intensity of 140 mu mol m(2) s(-1), at room temperature, and with a salinity of 35.4 units. The main diatom species in the sediments were Skeletonema japonicum and Chaetoceros spores. Dinoflagellate cysts were represented by the genera Diplopsalis, Scrippsiella, and Woloszynskia and the species Protoperidinium avellanum and P. leonis. After 20 days of culturing, germination and growth was recorded for S. japonicum and several of the Chaetoceros species, although their abundance was low. The diatoms with abundant growth were Stauroneis legleri, Pseudostaurosira trainorii, Pseudostaurosira sp. 1, Pseudostaurosira sp. 2, and Navicula pseudoreinhardtii. The dinoflagellate Woloszynskia sp. also germinated and grew abundantly in the culture. This study includes a brief description of the cultured species and some aspects of their ecology. In addition, we discuss the possible causes for low levels of germination in planktonic diatoms, finding low dissolved oxygen concentrations in the bottom waters to be one of the main factors that presumably affected the survival of resting spores in the sediment.

2008
Tapia, R, Lange CB, Marchant M.  2008.  Living (stained) calcareous benthic foraminifera from recent sediments off Concepcion, central-southern Chile (similar to 36 degrees S). Revista Chilena De Historia Natural. 81:403-416. AbstractWebsite

This Study examines onshore-offshore and vertical distribution of living (Rose Bengal stained) benthic foraminifera (> 180 mu m fraction) from three sediment stations along a bathymetric transect off Concepcion. Chile (station 18 = 88 in water depth, station 26 = 120 m, station 40 = 1 030 in), within and below the oxygen minimum zone. All cores were collected in austral winter. Calcareous foraminifera dominated the three stations. The species composition, living foraminifera density, and vertical distribution patterns within the sediment changed in accordance with bottom water dissolved oxygen concentration and food availability. Onshore-offshore pattern revealed overall highest living foraminiferal densities at shelf stations 18 and 26 where bottom water dissolved oxygen was lowest (similar to 0.2 mL(-1)) and content in labile organic matter highest. Within the sediment. maximum relative abundances (50-60 %) of living organisms were found in the 0-1 cm interval at the organic-rich and oxygen-poor shelf stations 18 and 26. In the well-oxygenated (2.7 mL(-1)) slope station 40, 70 % of living foraminifera were observed deeper than the first centimeter. The number of species and the contribution of the > 250 mu m fraction to the total fauna larger than 180 mu m increased offshore. Nonionella auris (d'Orbigny) dominated at stations 18 and 26 while a more diverse foraminifera fauna was found at station 40. This Study provides the first quantitative data on living benthic foraminifera in the area; seasonal and interannual changes are not addressed.

Sanchez, GE, Pantoja S, Lange CB, Gonzalez HE, Daneri G.  2008.  Seasonal changes in particulate biogenic and lithogenic silica in the upwelling system off Concepcion (similar to 36 degrees S), Chile, and their relationship to fluctuations in marine productivity and continental input. Continental Shelf Research. 28:2594-2600.   10.1016/j.csr.2008.07.010   AbstractWebsite

We analyzed the temporal and vertical distribution of biogenic (BSi) and lithogenic (LSi) silica, and diatom abundance in the upwelling center off Concepcion, Chile, from April 2004 to May 2005. Measurements were performed at the FONDAP COPAS Time Series Station 18 (36 degrees 30.8'S, 73 degrees 07.7'W; 88 m water depth), and were combined with primary production estimates and river runoff data to assess the relationships between water column BSi and primary production, and between LSi and river runoff. Throughout the sampling period, water-column-integrated (0-80m) BSi averaged 252 +/- 287 mmol m(-2), and was about six times higher than average LSi (44 +/- 30 mmol m(-2)). The highest water column BSi observed during the upwelling season (786 +/- 281 mmol m(-2)) coincided with increments in total diatom abundance, and high integrated chlorophyll a concentration and primary production. In contrast, LSi was nearly two times higher in winter (85 +/- 43 mmol m(-2)) than the annual average, in agreement with the period of substantial discharges from the Itata and Bio-Bio rivers. The observed temporal patterns in BSi and LSi are coincident with primary production-related factors and riverine outflow, respectively, suggesting that the BSi and LSi pools are separate. With respect to the vertical distribution in the water column, most of the BSi and diatoms were found in surface waters (0-30 m depth), whereas LSi was most abundant at depth. Our study attempts to make an inventory of both BSi and LSi in the water column off Concepcion, and gives the present-day background information necessary to assess potential future changes in the hydrological cycle that, in turn, may induce modifications in the Si path from the watersheds to the ocean. (C) 2008 Elsevier Ltd. All rights reserved.

Venrick, EL, Lange CB, Reid FMH, Dever EP.  2008.  Temporal patterns of species composition of siliceous phytoplankton flux in the Santa Barbara Basin. Journal of Plankton Research. 30:283-297.   10.1093/plankt/fbm107   AbstractWebsite

We have examined the species composition of 127 sediment trap samples collected sequentially from the Santa Barbara Basin, USA, during a 7-year period. The sampling period included two warm-water periods (El Ninos) and two cold-water periods (one La Nina and one more local). We examined changes in total species composition and changes in subsets of species accompanying extreme environmental conditions, as well as changes in flux composition associated with periods of anomalous flux. Our goal was to improve the scale and precision of hindcasting past conditions from the sedimentary record and, hence, prediction of the biological consequences of environmental change. Although large-scale climate events were accompanied by changes in the flux composition, there was little similarity in composition during environmentally similar periods, precluding generalization. Eighty-four percent of the flux (number of cells m(-2) d(-1)) and 89% of its variability were due to changes in the flux of four dominant species. Anomalous flux events were due to changes in flux of these species rather than introduction of new flora. Rare species showed the same patterns as the flora as a whole: there were changes in composition associated with extreme environmental temperatures but little redundancy of species between similar periods. Our data indicate that, at present, we can predict only that the specific composition of flux will change in response to extreme environmental conditions. It is premature to generalize about the specific composition of that response. Knowledge about mechanisms linking flux with ocean environment is currently insufficient to permit the precision of hindcast and prediction that we were seeking from our data. Nevertheless, species composition remains a potentially important tool for interpreting past environmental conditions on both the regional and the local scales.

Mohtadi, M, Rossel P, Lange CB, Pantoja S, Boning P, Repeta DJ, Grunwald M, Lamy F, Hebbeln D, Brumsack HJ.  2008.  Deglacial pattern of circulation and marine productivity in the upwelling region off central-south Chile. Earth and Planetary Science Letters. 272:221-230.   10.1016/j.epsl.2008.04.043   AbstractWebsite

A high-resolution sea surface temperature and paleoproductivity reconstruction on a sedimentary record collected at 36 degrees S off central-south Chile (GeoB 7165-1, 36 degrees 33'S, 73 degrees 401W, 797 in water depth, core length 750 cm) indicates that paleoceanographic conditions changed abruptly between 18 and 17 ka. Comparative analysis of several cores along the Chilean continental margin (30 degrees-41 degrees S) suggests that the onset and the pattern of deglacial warming was not uniform off central-south Chile due to the progressive Southward migration of the Southern Westerlies and local variations in upwelling. Marine productivity augmented rather abruptly at 13-14 ka, well after the oceanographic changes. We suggest that the late deglacial increase in paleoproductivity off central-south Chile reflects the onset of an active upwelling system bringing nutrient-rich, oxygen-poor Equatorial Subsurface Water to the euphotic zone, and a relatively higher nutrient load of the Antarctic Circumpolar Current. During the Last Glacial Maximum, when the Southern Westerlies were located further north, productivity off central-south Chile, in contrast to off northern Chile, was reduced due to direct onshore-blowing winds that prevented Coastal upwelling and export production. (C) 2008 Elsevier B.V. All rights reserved.

Diaz-Ochoa, JA, Lange CB, De Lange GJ.  2008.  Fish scale preservation and abundance in sediments from the continental margin off Chile (21-36 degrees S). Revista Chilena De Historia Natural. 81:561-574. AbstractWebsite

The relationship between fish scale preservation and variations in the sediment redox conditions on Chile's continental shelf are evaluated herein through fish scale counts and normalized concentrations of redox sensitive elements (Mo/Al, S/Al, Fc/Al) using eight sediment cores taken from Sites under the influence of the oxygen minimum zone off Chile (Iquique: 20 degrees 15' S, Mejillones Bay: 23 degrees S, Concepcion: 36 degrees S). Off northern Chile (Iquique and Mejillones), fish scales from anchovy (Engraulis ringens) and the Myctophidae family are dominant (mean = 90 and 120 scales 1 000 cm(-3), respectively). whereas off central-southern Chile (Concepcion), jack mackerel (Trachurtus murphy) scales are the most abundant (mean = 140 scales 1,000 cm-3). The abundance of hake (Merlurccis gayi gayi) and sardine (Sardinops sagax) scales is approximately one order of magnitude lower than that of anchovy or jack mackerel. In general, the highest values and widest ranges of variation in the Mo/Al, S/Al, and Fc/Al ratios are found in Mejillones (Mo/Al similar to 0.8-12 mg g(-1), S/Al 0.2-4.6 g g(-1), Fe/Al 03-0.7 g g(-1)), followed by Iquique (Mo/Al similar to 0.2-1.8, S/Al 0.2-0.7, Fe/Al 0.5-0.8): Concepcion has lower, less variable values (Mo/Al similar to 0.07, S/Al similar to 0.15, Fe/Al similar to 0.5). According to the Mo/Al ratio, used as an indicator of paleo-oxygenation, reducing conditions in the Mejillones Bay and Iquique sediments are relatively more intense than in those off Concepcion. At all three sampling sites, the relationship between the abundance of anchovy scales and the logarithm of the Mo/Al ratio is statistically significant (r(2) = 0.46, P < 0.0001), indicating a dependence between these two variables. In particular, for Mo/Al < 1 mg g(-1), small changes in the redox conditions can affect considerably scale preservation in the sediment, whereas this dependence decreases with Mo/Al >= 1 mg g(-1).

2007
Vargas, G, Pantoja S, Rutllant JA, Lange CB, Ortlieb L.  2007.  Enhancement of coastal upwelling and interdecadal ENSO-like variability in the Peru-Chile Current since late 19th century. Geophysical Research Letters. 34   10.1029/2006gl028812   AbstractWebsite

Secular trends in coastal upwelling proxies from a sediment record at 23 degrees S encompassing 250 years reveal two distinct stages separated by a transition period between AD 1820 and 1878. Persistent interdecadal variability that roughly follows the Pacific Decadal Oscillation is accompanied by intensification of upwelling-favourable coastal winds and decreased coastal sea surface temperature since AD 1878. We propose that an increased land-sea thermal contrast along the arid coast of northern Chile and Peru intensifies the equatorward wind stress due to reduced mean low-cloud cover, resulting in enhanced primary and export production during interdecadal El Nino-like conditions. This mechanism overcompensates for the overall effect of a regional surface warming secular trend in the Peru-Chile Current System, providing a novel insight on physical and biogeochemical feedbacks of coastal upwelling ecosystems to global warming.

Contreras, S, Pantoja S, Neira C, Lange CB.  2007.  Biogeochemistry of surface sediments off Concepcion (similar to 36 degrees S), Chile: El Nino vs. non-El Nino conditions. Progress in Oceanography. 75:576-585.   10.1016/j.pocean.2007.08.030   AbstractWebsite

We compared the signals of several water column properties (upwelling intensity, sea level anomaly, temperature, nutrients, dissolved oxygen, chlorophyll-a, and surface sediments) of the continental shelf off Concepcion (36 degrees S) during the 1997-1998 El Nino with those of a normal year (2002-2003). We found that the primary hydrographic effect of El Nino 1997-1998 was a reduction in the input of nutrient-rich, oxygen-poor Equatorial Subsurface Water over the shelf. This affected the biology of the water column, as evidenced by the reduced phytoplankton biomass. Surface sediment properties (biogenic opal, organic carbon, bulk delta N-15) observed during El Nino 1997-1998 reflected a reduced export production and the sediments failed to show the water column seasonality that occurs under normal conditions. In addition, weakened denitrification and/or upper water column fertilization could be inferred from the sedimentary delta N-15. Although diminished, export production was preserved in the surface sediments, revealing less degraded organic matter in the upwelling period of the El Nino year than in the normal year. We suggest that the fresher organic material on the seafloor was probably associated with a severe reduction in the polychaete Parapronospio pinnata, which is considered to be the most important metazoan remineralizer of organic carbon at the sediment-water interface in the study area. (c) 2007 Elsevier Ltd. All rights reserved.

Harada, N, Uchida M, Shibata Y, Ahagon N, Miyashita W, Lange CB, Pantoja S.  2007.  Fluctuations in alkenone-derived sea surface temperature, productivity, and ventilation in the Magellan Strait, Chilean continental margin, over the past 12 kyr. Geophysical Research Abstracts. ( Harada N, Ed.). AbstractWebsite

In 2003, Leg 3 of the R/V MIRAI MRO3-KO4 cruise, which was part of the BEAGLE (Blue Earth Global Ocean Experiment) program, took place along the Chilean marginal area (36-54 degree S) and the Magellan Strait. The main goal of this leg was to study changes in the biological pump, sea surface water temperature and ventilation speed of the intermediate water during the recent past (last 12,000 years) geological era, and to clarify the bio-optical dynamics in the surface water at present times. The eastern South Pacific Ocean is one of the least explored and most productive regions of the global ocean. Circulation along the Chilean coastline is controlled by the West Wind Drift (WWD) which approaches the coast at 45 degree S, where it splits into the Peru-Chile Current (PCC) and the Cape Horn Current (CHC). The PCC flows equatorward to ca. 4 degree S where it turns westward. The CHC flows poleward along the southernmost coast of Chile. The area north of ca. 40 degree S is characterized by very high productivity due to coastal upwelling of nutrient-rich equatorial subsurface waters (ESSW) and a sub-surface oxygen minimum zone. South of this latitude, productivity is also high due to the interplay of nutrients from the south and runoff from the Chilean fjord system. Antarctic Intermediate Water, which has high oxygen, low nutrients and salinity, is present at the depths 400-900m. Thus, the Chilean marginal area has been recognized as a key area for biogeochemical cycle of carbon in the global oceans not only during modern times but also over the past geological period. Studies over the past decade have focused on the area north of ca. 43 degree S but little is known of the paleoceanographic history in the southern region. Based on the above-mentioned purpose, Leg 3 of cruise of R/V MIRAI MR03-K04 retrieved four piston, two gravity and four multiple cores in the Chilean marginal sea and the Magellan Strait. Piston core PC-03 collected at the mouth of Magellan Strait (52 degree 52'S, 74 degree 05'W, water depth 560m) was used in this study. In this presentation, alkenone-derived sea surface temperature (SST) with decadal to centennial time resolution over the past 12ka are shown. Alkenone-SST range between 10 and 12 degree C in the early Holocene, and show a marked decline from 12 degree C to 9 degree C since 6 kyr BP. Changes in SST are accompanied by changes in primary productivity proxies such as biogenic opal, total organic carbon, total nitrogen, and isotopes of organic matter d super(13)C and d super(15)N, as well as changes in ventilation based on carbon isotope data of planktic and benthic foraminifers.

2006
Kemp, AES, Pearce RB, Grigorov I, Rance J, Lange CB, Quilty P, Salter I.  2006.  Production of giant marine diatoms and their export at oceanic frontal zones: Implications for Si and C flux from stratified oceans. Global Biogeochemical Cycles. 20: American Geophysical Union, 2000 Florida Ave., N.W. Washington DC 20009 USA, [mailto:service@agu.org], [URL:http://www.agu.org]   10.1029/2006gb002698   AbstractWebsite

From a synthesis of recent oceanic observations and paleo-data it is evident that certain species of giant diatoms including Rhizosolenia spp. Thalassiothrix spp. and Ethmodiscus rex may become concentrated at oceanic frontal zones and subsequently form episodes of mass flux to the sediment. Within the nutrient bearing waters advecting towards frontal boundaries, these species are generally not dominant, but they appear selectively segregated at fronts, and thus may dominate the export flux. Ancient Thalassiothrix diatom mat deposits in the eastern equatorial Pacific and beneath the Polar Front in the Southern Ocean record the highest open ocean sedimentation rates ever documented and represent vast sinks of silica and carbon. Several of the species involved are adapted to a stratified water column and may thrive in Deep Chlorophyll Maxima. Thus in oceanic regions and/or at times prone to enhanced surface water stratification (e.g., during meltwater pulses) they provide a mechanism for generating substantial biomass at depth and its subsequent export with concomitant implications for Si export and C drawdown. This ecology has important implications for ocean biogeochemical models suggesting that more than one diatom "functional type" should be used. In spite of the importance of these giant diatoms for biogeochemical cycling, their large size coupled with the constraints of conventional oceanographic survey schemes and techniques means that they are undersampled. An improved insight into these key species will be an important prerequisite for enhancing our understanding of marine biogeochemical cycling and for assessing the impacts of climate change on ocean export production.

Mohtadi, M, Hebbeln D, Ricardo SN, Lange CB.  2006.  El Nino-like pattern in the Pacific during marine isotope stages (MIS) 13 and 11? Paleoceanography. 21   10.1029/2005pa001190   AbstractWebsite

[1] Paleoceanographic evidence from midlatitudes bearing on the long-term development of Pacific Ocean surface circulation through the middle and late Pleistocene is scant because of a lack of marine paleorecords exceeding the last four or five glacial cycles. Here we compare benthic and planktonic foraminiferal stable carbon isotope data from a 1-Myr marine record in the southeastern subtropical Pacific with records from the equatorial Pacific and Southern Ocean in order to reconstruct sea surface circulation in this part of the world ocean and its possible link to the El Nino/Southern Oscillation (ENSO). We especially address marine isotope stages (MIS) 13 and 11, when internal climate dynamics are suggested to produce somewhat unusual interglacial periods. Our results show that the Southern Ocean controlled the circulation in the subtropical Pacific throughout the middle and late Pleistocene and that the hitherto existing hypotheses cannot explain the peak delta(13)C values in both MIS 13 and 11. We argue that the surface circulation pattern in the southeast Pacific during MIS 13 and 11 should have differed from any other interglacial, and we suggest that the subsequent changes in the latitudinal and meridional heat and moisture transfer contributed to the unusual paleoceanographic settings during these stages. We further hypothesize unusually strong El Nino-like conditions during MIS 13 and 11. This hypothesis, if true, challenges a direct forcing of ENSO by orbital parameters.