GIS technologies and spatial organization patterns among hunter-gatherers: an archaeological case study from Southern Patagonia (southern South America)

This paper discusses some aspects of hunter-gatherer spatial organization in southern South Patagonia, in later times to 10,000 cal yr BP. Various methods of spatial analysis, elaborated with a Geographic Information System (GIS) were applied to the distributional pattern of archaeological sites with radiocarbon dates. The shift in the distributional pattern of chronological information was assessed in conjunction with other lines of evidence within a biogeographic framework. Accordingly, the varying degrees of occupation and integration of coastal and interior spaces in human spatial organization are explained in association with the adaptive strategies hunter-gatherers have used over time. Both are part of the same human response to changes in risk and uncertainty variability in the region in terms of resource availability and environmental dynamics.

Survey of sediment quality in Sabine Lake, Texas and vicinity

The toxicity of sediments in Sabine Lake, Texas, and adjoining Intracoastal Waterway canals was determined as part of bioeffects assessment studies managed by NOAA’s National Status and Trends Program. The objectives of the survey were to determine: (1) the incidence and degree of toxicity of sediments throughout the study area; (2) the spatial patterns (or gradients) in chemical contamination and toxicity, if any, throughout the study area; (3) the spatial extent of chemical contamination and toxicity; and (4) the statistical relationships between measures of toxicity and concentrations of chemicals in the sediments. Surficial sediment samples were collected during August, 1995 from 66 randomly-chosen locations. Laboratory toxicity tests were performed as indicators of potential ecotoxicological effects in sediments. A battery of tests was performed to generate information from different phases (components) of the sediments. Tests were selected to represent a range in toxicological endpoints from acute to chronic sublethal responses. Toxicological tests were conducted to measure: reduced survival of adult amphipods exposed to solid-phase sediments; impaired fertilization success and abnormal morphological development in gametes and embryos, respectively, of sea urchins exposed to pore waters; reduced metabolic activity of a marine bioluminescent bacteria exposed to organic solvent extracts; and induction of a cytochrome P-450 reporter gene system in exposures to solvent extracts of the sediments. Chemical analyses were performed on portions of each sample to quantify the concentrations of trace metals, polynuclear aromatic hydrocarbons, and chlorinated organic compounds. Correlation analyses were conducted to determine the relationships between measures of toxicity and concentrations of potentially toxic substances in the samples. Based upon the compilation of results from chemical analyses and toxicity tests, the quality of sediments in Sabine Lake and vicinity did not appear to be severely degraded. Chemical concentrations rarely exceeded effects-based numerical guidelines, suggesting that toxicant-induced effects would not be expected in most areas. None of the samples was highly toxic in acute amphipod survival tests and a minority (23%) of samples were highly toxic in sublethal urchin fertilization tests. Although toxic responses occurred frequently (94% of samples) in urchin embryo development tests performed with 100% pore waters, toxicity diminished markedly in tests done with diluted pore waters. Microbial bioluminescent activity was not reduced to a great degree (no EC50 <0.06 mg/ml) and cytochrome P-450 activity was not highly induced (6 samples exceeded 37.1 ug/g benzo[a]pyrene equivalents) in tests done with organic solvent extracts. Urchin embryological development was highly correlated with concentrations of ammonia and many trace metals. Cytochrome P450 induction was highly correlated with concentrations of a number of classes of organic compounds (including the polynuclear aromatic hydrocarbons and chlorinated compounds). (PDF contains 51 pages)

A GEOPASS-NERC project on diatom deposition and sediment accumulation in Lake Baikal, Siberia

This new project is multidisciplinary, with physical and chemical palaeolimnological aspects mainly the responsibility of Swiss and Russian scientists, and the biological limnology and palaeolimnology components mainly undertaken by the British and Russian groups. The overall project aim is to improve palaeoclimate reconstructions using sedimentary diatoms by promoting better understanding of diatom ecology and sediment-forming processes. The initial work plan is divided into four main parts: To understand diatom phytoplankton ecology more fully, to assess taphonomic changes associated with the transformation of phytoplankton diatom communities into sediment assemblages, to demonstrate sediment core integrity and representativity and to calibrate modern diatom assemblages against contemporary climate records. The preliminary results from the interrelated studies of phytoplankton, sediment traps and sediment cores used in GEOPASS-NERC, demonstrate the complexity of links between the living and fossil systems. Furthermore, the nature of recent sedimentation in Lake Baikal is spatially variable and incompletely known. This poses a major challenge to palaeolimnological interpretation. Turbidite deposits and differential preservation of microfossils, combined with inadequate knowledge of the modern ecology of endemic diatoms, all conspire to obfuscate the sedimentary record of environmental change.

Distribution of Cu, Zn, Pb and Cd in some recent molluscan shells from Lake Mariut sediment

Shells and shell fragments were the principal constituents of the core sediment taken from LakeMariut. Their trace metals were studied to assess their contribution to environmental adjustment. The results indicated that the shells of Biomphalaria alexandrina, Mercierella enigmatica and Melanoida tuberculate contain higher amounts of Cu and Zn than the widely distributed shells of Lucina sp. and Cerastoderma edule. The Pb contents found in different types of shells were higher than the other metals. The Cd contents found in different shell types were the most important fraction in comparison to the total Cd in the sediments of the lake. The relationship between the concentrations of trace metals and mineralogical analysis revealed that lead tended to be more concentrated in aragonite than in calcite.

Seasonal Variations in Chlorophyll a Concentrations in Relation to Potentials of Sediment Phosphate Release by Different Mechanisms in a Large Chinese Shallow Eutrophic Lake (Lake Taihu)

The relationship between chlorophyll a and fractionation of sediment phosphorus, inorganic phosphate-solubilizing bacteria (IPB), and organic phosphate-mineralizing bacteria (OPB) was evaluated in a large Chinese shallow eutrophic lake (Lake Taihu) and its embayment (Wuli Bay). At the three study sites, the increase of chlorophyll a concentrations in April paralleled those of the iron bound phosphate accounting for major portion of sediment inorganic phosphate, and in June significantly higher OPB and IPB numbers (especially OPB) in sediment were main contributors to the peaks of chlorophyll a concentration. Even though IPB peaked from February to June, it should serve as an unimportant P source due to the irrelevancy with chlorophyll a and soluble reactive phosphorus (SRP). By contrast, at the other site in the embayment, the calcium-bound phosphate was predominant and solid, which was difficult to be released, and neither IPB nor OPB were detectable in the sediment, indicating weak potential for phosphorus release from the sediment, which was reflected in the small seasonal variation in SRP concentration in water column. Hence, the extents to which the three general mechanisms behind phosphate release from sediment (desorption of iron bound phosphate, solubilization by IPB and enzymatic hydrolysis by OPB) operated were different depending on seasons and sites in Lake Taihu, they may jointly drive phosphate release and accelerate the eutrophication processes.

Influence of Potamogeton crispus growth on nutrients in the sediment and water of Lake Tangxunhu

An incubation experiment was performed on Potamogeton crispus (P. crispus) using sediment collected from Lake Tangxunhu in the center of China, in order to determine the effects of plant growth on Fe, Si, Cu, Zn, Mn, Mg, P, and Ca concentrations in the sediments and overlying waters. After 3 months of incubation, Ca, Mg, and Si concentrations in the water column were significantly lower, and P and Cu concentrations were significantly higher than in unplanted controls. The effect of P. crispus growth on sediment pore waters and water-extractable elements varied. Concentrations of Ca, Mg, Si, Fe, Cu, and Zn were significantly higher, and P was significantly lower, than in pore waters of the control. Water-extracted concentrations of Fe, Mg, and Si in the sediments were lower, and P was higher, than in the control. Presence of P. crispus generally enhanced concentration gradients of elements between pore waters and overlying waters but not for P. The growth of P. crispus was associated with an increase in water pH and formation of root plaques, resulting in complex effects on the sediment nutritional status.

Phosphorus in interstitial water induced by redox potential in sediment of Dianchi Lake, China

The sediment redox potential was raised in the laboratory to estimate reduction of internal available phosphorus loads, such as soluble reactive phosphorus (SRP) and total phosphorus (TP), as well as the main elements of sediment extracts in Dianchi Lake. Several strongly reducing substances in sediments, which mainly originated from anaerobic decomposition of primary producer residues, were responsible for the lower redox potential. In a range of -400 to 200 mV raising the redox potential of sediments decreased TP and SRP in interstitial water. Redox potentials exceeding 320 mV caused increases in TP, whereas SRP maintained a relatively constant minimum level. The concentrations of Al, Fe, Ca2+, Mg2+, K+, Na+ and S in interstitial water were also related to the redox potential of sediments, suggesting that the mechanism for redox potential to regulate the concentration of phosphorus in interstitial water was complex.

Distribution of nitrogen and phosphorus in sediment cores and overlying water of Donghu Lake

In this study, the seasonal, vertical distribution of various phosphorus and nitrogen forms in the sediment and overlying water of Donghu Lake were investigated. The concentration of total nitrogen (TN) in overlying water was high in spring and autumn, but that of NO3--N reached its peak in autumn. From summer to autumn and from winter to spring, the concentration of phosphorus in overlying water decreased, while it increased from autumn to winter. Vertical characteristic forms of phosphorus in sediment cores are total phosphorus (TP), labile phosphorus (LP), Fe-P and Al-P, obviously enriched in the surface layer (0-10 cm), but their concentrations are observably reduced along with the depth of sediment. The research is of important theoretical and practical value to understand the status and to control the developmental trend of eutrophication in Donghu Lake.

Enhancement of dissolved phosphorus release from sediment to lake water by Microcystis blooms - an enclosure experiment in a hyper-eutrophic, subtropical Chinese lake

To clarify the possible influence of Microcystis blooms on the exchange of phosphorus (P) between sediment and lake water, an enclosure experiment was conducted in the hypereutrophic subtropical Lake Donghu during July-September 2000. Eight enclosures were used: six received sediment while two were sediment-free. In mid-August, Microcystis blooms developed in all the enclosures. There was a persistent coincidence between the occurrence of Microcystis blooms and the increase of both total P (TP) and soluble reactive P (SRP) concentrations in the water of the enclosures with sediments. In sediment-free enclosures, TP and SRP concentrations remained rather stable throughout the experiment, in spite of the appearance of Microcystis blooms. The results indicate that Microcystis blooms induced massive release of P from the sediment, perhaps mediated by high pH caused by intense algal photosynthesis, and/or depressed concentrations of nitrate nitrogen (NO3-N). (C) 2002 Elsevier Science Ltd. All rights reserved.

Characterization of stable isotope fractionation during methane production in the sediment of a eutrophic lake,lake dagow,germany

We measured delta C-13 of CO2, CH4, and acetate-methyl in profundal sediment of eutrophic Lake Dagow by incubation experiments in the presence and absence of methanogenic inhibitors chloroform, bromoethane sulfonate (BES), and methyl fluoride, which have different specificities. Methyl fluoride predominantly inhibits acetoclastic methanogenesis and affects hydrogenotrophic methanogenesis relatively little. Optimization of methyl fluoride concentrations resulted in complete inhibition of acetoclastic methanogenesis. Methane was then exclusively produced by hydrogenotrophic methanogenesis and thus allowed determination of the fractionation factors specific for this methanogenic pathway. Acetate, which was then no longer consumed, accumulated and allowed determination of the isotopic signatures of the fermentatively produced acetate. BES and chloroform also inhibited CH4 production and resulted in accumulation of acetate. The fractionation factor for hydrogenotrophic methanogenesis exhibited variability, e. g., it changed with sediment depth. The delta C-13 of the methyl group of the accumulated acetate was similar to the delta C-13 of sedimentary organic carbon, while that of the carboxyl group was by about 12 parts per thousand higher. However, the delta C-13 of the acetate was by about 5 parts per thousand lower in samples with uninhibited compared with inhibited acetoclastic methanogenesis, indicating unusual isotopic fractionation. The isotope data were used for calculation of the relative contribution of hydrogenotrophic vs. acetoclastic methanogenesis to total CH4 production. Contribution of hydrogenotrophic methanogenesis increased with sediment depth from about 35% to 60%, indicating that organic matter was only partially oxidized in deeper sediment layers.

Spatial variability in water quality and surface sediment diatom assemblages in a complex lake basin,lake of the woods,ontario,canada

Lake of the Woods (LOW) is an international waterbody spanning the Canadian provinces of Ontario and Manitoba, and the U.S. state of Minnesota. In recent years, there has been a perception that water quality has deteriorated in northern regions of the lake, with all increase in the frequency and intensity of toxin-producing cyanobacterial blooms. However, given the lack of long-term data these trends are difficult to verify. As a first step, we examine spatial and seasonal patterns in water quality in this highly complex lake on the Canadian Shield. Further, we examine surface sediment diatom assemblages across multiple sites to determine if they track within-take differences in environmental conditions. Our results show that there are significant spatial patterns in water quality in LOW. Principal Component Analysis divides the lake into three geographic zones based primarily on algal nutrients (i.e., total phosphorus, TP), with the highest concentrations at sites proximal to Rainy River. This variation is closely tracked by sedimentary diatom assemblages, with [TP] explaining 43% of the variation in diatom assemblages across sites. The close correlation between water quality and the surface sediment diatom record indicate that paleoecological models could be used to provide data on the relative importance of natural and anthropogenic sources of nutrients to the lake.

Intra-habitat heterogeneity of microbial food web structure under the regime of eutrophication and sediment resuspension in the large subtropical shallow Lake Taihu, China

Planktonic microbial community structure and classical food web were investigated in the large shallow eutrophic Lake Taihu (2338 km(2), mean depth 1.9 m) located in subtropical Southeast China. The water column of the lake was sampled biweekly at two sites located 22 km apart over a period of twelve month. Site 1 is under the regime of heavy eutrophication while Site 2 is governed by wind-driven sediment resuspension. Within-lake comparison indicates that phosphorus enrichment resulted in increased abundance of microbial components. However, the coupling between total phosphorus and abundance of microbial components was different between the two sites. Much stronger coupling was observed at Site 1 than at Site 2. The weak coupling at Site 2 was mainly caused by strong sediment resuspension, which limited growth of phytoplankton and, consequently, growth of bacterioplankton and other microbial components. High percentages of attached bacteria, which were strongly correlated with the biomass of phytoplankton, especially Microcystis spp., were found at Site 1 during summer and early autumn, but no such correlation was observed at Site 2. This potentially leads to differences in carbon flow through microbial food web at different locations. Overall, significant heterogeneity of microbial food web structure between the two sites was observed. Site-specific differences in nutrient enrichment (i.e. nitrogen and phosphorus) and sediment resuspension were identified as driving forces of the observed intra-habitat differences in food web structure.