Foraminifera as paleoenvironmental tracers
(Collaboration with Prof. Silvia Spezzaferri, University of Fribourg, Switzerland; Prof. Judith McKenzie, ERDW-ETHZ, Switzerland)
Research will concentrate on the transition to Late Pleistocene Marine Isotope Stage 5 (with particular attention to Sub-stage 5e, from about 130 to 120 ka). The selected areas for this study are the southern and northeastern Australian margins where the Ocean Drilling Program Legs 133, 182 and 194 drilled sedimentary sections particularly suitable for high-resolution studies.
This Swiss NSF project proposes to investigate the response of foraminifera to paleoceanographic changes in terms of nutrient availability, climate and its influence on ice volume and sea level, and variations in ocean chemistry. In particular, the aim of this study is to calibrate changes in benthic and planktonic foraminiferal assemblages during selected time intervals of known paleoceanographic changes by comparing biological and chemical proxies (e.g., benthic and planktonic assemblages composition and abundance, oxygen and carbon isotopes, Mg/Ca, Cd/Ca, and Zn/Ca records of foraminiferal shells and phosphorus and organic matter in sediments).
The novelty of this research sits on the fact that micropaleontological studies (qualitative and quantitative approach) will be coupled with geochemical studies on foraminifera (benthic and planktonic) and on sediments (phosphorus and organic matter) to obtain a more complete and multiproxy paleoceanographic scenario.
We plan to use phosphorus from sediments as a proxy to trace changes in paleoproductivity, nutrient input from the continent, and burial, using the SEDEX method to differentiate and quantify phosphorus sedimentary reservoirs.
High resolution study of North Atlantic sediments
(Collaboration with Dr. Sylvain Huon, UMPC, Paris, France)
In the last 20 years, many studies have proved that climate can change rapidly (i.e., timescale of individual human lifetimes), both on a regional or even global scale (Heinrich, 1988). These flips of the climate system (e.g., Heinrich events), rapidly leading to colder climate conditions, happened mainly during glacial and interstadial periods, when climate was in a more unstable mode than in our present interglacial state. However, there are evidences of rapid coolings also during periods of relatively stable and warm climate, such as the early Holocene (Alley et al., 1997).
A high resolution study of marine sediments from the North Atlantic (core SU90-09) will be carried out in collaboration with Dr. Sylvain Huon from Université Pierre et Marie Curie (UPMC-CNRS-INRA), Paris, France. First results from core SU90-09 (Tamburini et al., 2002), studied for Heinrich events 4 and 5 (between 55 and 32 ka), indicate that variation in phosphorus sinks in this core did record the rapid oceanographic and climatic changes related to Heinrich events. The goal of this research is to identify, if present, the record of these rapid climate shifts during the last interglacial stage (Stage 5), a period comparable to our present climate state.
We are going to analyze at a high-resolution samples from core SU90-09, spanning the time period between Marine Isotopic Stages 4 and 6. The samples, already collected and stored at the Université Pierre et Marie Curie, are going to be analyzed for P speciation, and the results will be compared with the other organic proxies. Dr. Huon will analyze the samples for organic carbon content, carbon and nitrogen isotopes.
The importance of using P speciation for this kind of studies lies in the fact that 1) phosphate concentrations in bottom waters are frequently used to assess changes in oceanic circulation between glacial and interglacial, 2) change in P sinks are sensible to changes in oxygenation of the sediments and in bottom waters, and 3) changes in nutrients concentration in the ocean, even on short periods, may have important feedbacks on primary productivity, CO2, and climate.
If the occurrence of rapid climate flips is confirmed by this study, our results will corroborate previous theories of climate instability even during warm stages.
› Alley, R.B. et al., 1997. Holocene climatic instability: a prominent, widespread event 8200 years ago. Geology, 25(6): 483-486.
› Heinrich, H., 1988. Origin and consequences of cyclic ice rafting in the Northeast Atlantic Ocean during the past 130,000 years. Quaternary Res., 29: 142-152.
› Tamburini, F. et al., 2002. Dysaerobic conditions during Heinrich events 4 and 5: Evidence from phosphorus distribution in a North Atlantic deep-sea core. Geochimica et Cosmochimica Acta, 66(23): 4069-4083.
Geochemistry of marine sediments from the Adriatic region, Emilian-Marchean coast:
an environmental study
(Collaboration with Prof. Rodolfo Coccioni, University of Urbino, Italy)
Coastal regions are of fundamental importance for human kind, and historically, it has been proved that these regions have seen the onset of many cultures. Nowadays is of great interest to study and understand the sustainability of urban development, and the impact of human activities (agriculture, tourism, etc.) on the natural coastal environment. The area between the San Bartolo hill and the river Metauro (Emilian Marchean regions, along the Adriatic coast, eastern Italy) has recently become a protected area, because of its high environmental importance.
In the framework of an environmental project aiming at studying the geological, geochemical, and biological situation of this region, we are planning to analyze phosphorus distribution in sediments.
In the last few decades, agricultural, domestic, and industrial use of P has increased, enhancing the transport of dissolved and particulate P from terrestrial to aquatic ecosystems. Despite its important role as a nutrient in all ecosystems, excess P may lead to changes in other nutrient cycles (e.g., nitrogen, carbon, and oxygen), alter the environment (e.g., eutrophication), and reduce water quality (Melack, 1995). Surface sediment and seawater samples have been recovered along several transects, which have been sampled on a seasonal basis starting, from winter 2002. To understand the biological setting of the area, seawater samples have been analyzed for nitrate, nitrite, and phosphate concentration, and a detailed micropaleontological study of benthic foraminifer associations and their degree of malformation, linked to environmental stress, have been performed.
P distribution in the sediment will be correlated to the existent data, and will provide more information about environmental parameters along this highly urbanized area. Moreover, the possibility of a parallel biological and chemical study in these sediments, and the acquisition of data along a spatial and temporal grid, will give the opportunity to understand how enhanced P input to a coastal area is influencing benthic distribution and biological activity in bottom waters.
› Melack, J.M., 1995. Transport and transformations of P, fluvial and lacustrine ecosystems. In: H. Tiessen (Editor), Phosphorus in the global environment. John Wiley and Sons Ltd., pp. 245-252.
High Through-Put Solid-Phase Extraction Manifold (SPEM) for Separating and Quantifying Different forms of Phosphorus and Iron in Particulate Matter and Sediments
(Dr. Kathleen C. Ruttenberg, University of Honolulu at Manoa, USA).
The SEDEX method, a sequential extraction technique, was developed to separate different solid forms of P (Ruttenberg, 1992). The principal flaws of this method are 1) the partial loss of material during procedure, and 2) being time consuming, because of the extensive manipulation.
The SPEM consists of a vacuum manifold which can accommodate 24 reaction vessels. To address the first concern, each reaction vessel has an integrated filter holder at its base which allow to remove supernatant at the termination of each step via vacuum filtration. Because the same filter remains in the reaction vessel during the entire SEDEX procedure, and supernatant is removed only by passing through this filter, there is no possibility of sediment loss during the entire procedure. Moreover, the proposed SPEM decreases the extraction time required and the number of steps (from 12 to 9). Performance of the SPEM has been evaluated by comparing P-speciation and concentration data of known reference material obtained via SPEM-SEDEX to that which has been obtained by the conventional SEDEX.
› Ruttenberg, K.C., Development of a sequential extraction method for different forms of phosphorus in marine sediments, Limnology Oceanography, 37 (7), 1460-1482, 1992.
Evaluation of the effect of different levels of oxygen in porewaters and bottom water on the early diagenesis of phosphorus
(Collaboration with Dr. Kathleen C. Ruttenberg, University of Honolulu at Manoa, USA).
The distribution of the different sedimentary phases of phosphorus in Pleistocene and Holocene sediments, and its link to other geochemical proxies (e.g. nitrogen stable isotopes and organic carbon) suggest that early diagenetic processes affecting phosphorus are also controlled by oxygen levels. To better evaluate the effect of oxygen and interpret marine records, recent sediments from three cores collected in the Californian borderland basins are analyzed for solid-phase phosphorus, using the SPEM-SEDEX extraction technique. The three sites are characterized by different oxygen levels, and porewater samples have been already analyzed for dissolved phosphate, nitrate, iron, and silica. In a second phase, the obtained data will also enable to model the behavior of phosphorus in the sediments.
Effect of photoreduction on liberation of phosphorus from dust on seawater
(Dr. Kathleen C. Ruttenberg, University of Honolulu at Manoa, USA).
The photolytic reduction of iron (Fe) present in dust is known to provide dissolved and bioavailable Fe in the oligotrophic waters of the open ocean. One possibility is that also phosphate, carried along with Fe-rich dust, that is generally enriched in P, could be solubilized during photoreduction of Fe and could supply bioavailable P to surface waters. This could have important biological effects, because both elements are important nutrients. Moreover, the extent of their bioavailability in ocean waters could impact also other nutrients' cycle, i.e. nitrogen, especially in oligotrophic areas.
The aim of this project is to evaluate the importance of P release associated with photolytic reduction of Fe-compounds, through a series of laboratory photoreduction experiments. Synthetic Fe-minerals and natural dust samples (Saharan dust and Chinese Loess), characterized for their P content, are used in these experiments.
Phosphorus in marine sediments during the last 150,000 years: exploring relationships between continental weathering, productivity, and climate
(PhD Thesis, University of Neuchâtel, Prof. K.B.Föllmi)
The aim of this PhD project was to investigate the links between continental weathering and the marine nutrient household during the last 150'000 years in taking a close look at the phosphorus cycle (using a sequential extraction method). Our starting point was a selection of well-dated Ocean Drilling Program (ODP) material from Legs 108, 112, 117, 128, 130, 151, and 184. Besides detailed phosphate measurements, mineralogical composition, major and minor elemental composition, organic matter composition and nitrogen stable isotope measurements have been examined. Sediments from a North Atlantic core (SU 9009), sampled at high resolution, have been analyzed to study phosphorus phases variations in correlation with Heinrich events 4 and 5 (in collaboration with Dr. S. Huon).
The research was focused on the late Pleistocene-early Holocene glacial-interglacial period. This time interval is an ideal subject for palaeoclimatological research, because of the excellent accessibility to proxy data, a good time resolution, and the occurrence of prominent shifts in the climate system.