Case Studies Of Eco-geology On Typical Islands In Ny-(?)lesund, Arctic And Zhoushan Archipelage, Zhejiang

To compare between Antarctica and Arctic, to better understand the evolution of the polar environment and its respond to global change, and to promote the theoretical system of ecological geology in polar ice-free areas, we carried out studies in Spitsbergen, Svalbard. Meanwhile, to expand the study scope of ecological geology, we performed related researches in Zhoushan Archipelago, Zhejiang.In the present dissertation, a paleo-notch sediment profile with a 118 cm length was sampled in Ny-Alesund, Spitsbergen, Arctic, and samples in a special intertidal zone influenced by buried ancient wood were collected in Zhoushan Archipelago, Zhejiang. Then, analysis, including chronology, sedimentology, geochemistry, isotopic geochemistry, palaeoecology, Geological microbiology, microbial mineralization, were performed on those samples. Main conclusions are listed as follows:(1) The identification of sediment sources and the deposited age indicate that seabirds have inhabited Ny-Alesund since 9,400 yr B.P. after Kongsfjorden was completely deglaciated. This is the first report on Holocene seabird occupation on Ny-Alesund and it provides the foundation for understanding the ecological history of seabirds in Svalbard in Holocene;(2) The calibrated aragonite isotopic temperature equation was established for Ny-Alesund based on comparing theδ18O profiles of shell fragments in paleo-notch sediments and modern mollusks. The paleotemperature range was reconstructed as-0.52～+4.78℃, warmer than today by about 1℃. Moreover, the mortality of the fossil mollusks was very likely caused by an abrupt cooling event at about 9,400 yr B.P., which was inferred from reduced insolation, weakened thermohaline circulation (THC), and abrupt decreased SST. This abrupt cooling event might extensively occur.(3) AMS14C chronology was established for the 70-118 cm unit in paleo-notch sediments, and the bio-element cluster was extracted to reconstruct the historic seabird populations. The historic seabird populations experienced obvious fluctuations during 9400-1860 yr BP:(Ⅰ) at the beginning of landing, the seabird populations gradually increased, and reached the maximum at about 7650 yr BP; (Ⅱ) in the subsequent 5800 years (7650-1860 yr BP), the seabird populations intensively fluctuated during 7650-6280 yr BP,6280-4580 yr BP, and 4580-2540 yr BP. Moreover, the fluctuations of historic seabird populations were dominated by North Atlantic climate change, not SST; (4) The gravel accumulation in 10-70 cm unit in paleo-notch sediments was caused by LIA; The sediments in 0-10 cm unit was related with anthropogenic activities in Ny-Alesund, Arctic;(5) The modern microbial mineralization study in the intertidal zone influenced by ancient wood revealed that neutrophilic iron-oxidizing bacteria (Leptothrix ochracea, Gallionella ferruginea) and sulfate reduction bacteria (SRB) extensively existed in the intertidal zone. The biomineralization product of neutrophilic iron-oxidizing bacteria is ferrihydrite, a poorly ordered iron oxide. The mineralization process of the iron oxidizing bacteria undergoes different stages, from extracellular mineralization, intracellular mineralization to the whole cell mineralization, and these bacteriogenic iron oxides (BIOS) obviously affected the fate of metal ions there. The SRB were involved in Fe-S cycle to induce extracellular biomineralization.(6) Microscale analysis methods were employed to study the nanoscale characterization and trace element distributions in the stratified sediments and the concretions in the special intertidal zone, Zhoushan Archipelago, Zhejiang. Light microscopy, scanning electron microscopy (SEM) and backscattered electron imaging (BSE) revealed that these samples were composed of different coatings on sand grains. The main mineral compositions of coatings are ferrihydrite and goethite for the yellowish-red parts, and birnessite and vernadite for the black parts using X-ray powder diffraction (XRD). SEM observations show bacteriogenic products and bacterial remnants extensively occurred in the coatings, indicating that bacteria likely played an important role in the formation of Fe-Mn oxyhydroxide coatings here. PAAS-normalized middle rare-earth-element (MREE) enrichment patterns were characterized by the coatings, which were caused by two subsequential processes:(1) preferentially release of Fe-Mn from the beach rocks by fermentation of ancient woods and colloidal flocculation in the mixing water zone; (2) preferentially adsorption of MREE by Fe-Mn oxyhydroxides from the seawater. The chemical results indicate that trace metals of the coatings are enriched with Sc, V, Cr, Co, Ni, Cu, Zn, Ba, particularly for Co, Ni, implying significant implications for environmental bioremediation. Furthermore, the formation model for these Fe-Mn oxyhydroxide coatings was proposed. These findings in the present study provide a sight in the nannoscale features of Fe-Mn oxyhydroxide coatings and the Fe-Mn biogeochemical cycles involved buried organic matters in the intertidal zone or shallow coast.