In this volume John Murray investigates the ecological processes that control the distribution, abundance, and species diversity of benthic foraminifera in environments ranging from marsh to the deepest ocean. To interpret the fossil record it is necessary to have an understanding of the ecology of modern foraminifera and the processes operating after death leading to burial and fossilisation. This book presents the ecological background required to explain how fossil forms are used in dating rocks and reconstructing past environmental features including changes of sea level. It demonstrates how living foraminifera can be used to monitor modern-day environmental change. Ecology and Applications of Benthic Foraminifera presents a comprehensive and global coverage of the subject using all the available literature. It is supported by a website hosting a large database of additional ecological information (www.cambridge.org/0521828392) and will form an important reference for academic researchers and graduate students in Earth and Environmental Sciences.

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Ecology and Applications of Benthic Foraminifera

https://doc.rero.ch/record/29510/files/spe_fit.pdf

The FOBIMO (FOraminiferal BIo-MOnitoring) initiative—Towards a standardised protocol for soft-bottom benthic foraminiferal monitoring studies

Effect-directed analysis supporting monitoring of aquatic environments - An in-depth overview

Arsenic is the 20th most abundant element in the Earth's crust (56) and is widely distributed throughout nature as a result of weathering, dissolution, fire, volcanic activity, and anthropogenic input (13). The last includes the use of arsenic in pesticides, herbicides, wood preservatives, and dye stuffs as well as production of arsenic-containing wastes during smelting and mining operations (56). In arsenic-enriched environments, a major concern is the potential for mobilization and transport of this toxic element to groundwater and drinking water supplies. In Bangladesh, an estimated 57 million people have been exposed to arsenic through contaminated wells (9). This incident serves as an unfortunate reminder of the toxic consequences of arsenic mobilization and underscores the need to understand the factors controlling the mobility and solubility of arsenic in aquatic systems (60).

Coeur d'Alene Lake (CDAL) is the second largest lake in Idaho. As a result of a century of mining along the Coeur d'Alene River, one of two rivers feeding CDAL, lake sediments are highly enriched in trace elements including Ag, As, Cd, Pb, Sb, and Zn (31). Sediment pore waters are also trace element enriched with mean total arsenic and lead concentrations exceeding 160 and 250 μg/liter (28), respectively. Nevertheless, CDAL surface waters comply with current federal drinking water standards (28) (50 and 15 μg/liter for As and Pb [75, 76], respectively). Because residents of Northern Idaho use these waters for recreation and fishing and as a source of drinking water (82), concern remains over the possibility that contaminants could be mobilized from the sediment to the water column.

Iron is the dominant metal in the Coeur d'Alene system, constituting approximately 10% of the sediments by dry weight (14, 27). Because iron is exceptionally abundant in CDAL sediments, its transformations are likely to influence the bioavailability and mobility of trace elements such as arsenic (16). Sorption of As onto the surface of insoluble iron oxyhydroxides is well documented, as is the observation that the oxidation state of arsenic influences its propensity to sorb onto iron mineral surfaces (5, 18, 22, 50–52, 62, 63, 65). In arsenic-enriched soils and sediments, an increase in soluble As(III) is commonly observed upon establishment of reducing conditions (1, 8, 52, 53, 69). This observation has been attributed to poor sorption of As(III) onto iron oxyhydroxides (18, 62) and is consistent with the idea that As(III) is more mobile than As(V) in aquatic environments (39). Recent studies, however, suggest that under certain conditions at circumneutral pH, As(III) can sorb to iron oxyhydroxides at least as strongly as As(V) (50, 63, 74). In view of this, alternative mechanisms should be considered to explain why soluble As(III) commonly increases when soils and sediments become anoxic.

The occurrence of soluble As in reduced aquatic environments has been attributed to the reductive dissolution of solid-phase iron oxyhydroxides followed by the release of sorbed arsenic (1, 4, 8, 18, 53, 60). In such environments, the reductive dissolution of iron oxyhydroxides is largely mediated by the activity of dissimilatory iron-reducing bacteria (DIRB) (43). Our laboratory has demonstrated that the DIRB Shewanella alga BrY, an organism that cannot respire As(V), mobilizes As(V) from the solid-phase ferric arsenate mineral scorodite by reducing Fe(III) to Fe(II) (14). As(V) reduction is therefore not a prerequisite to arsenic solubilization from FeO(OH)x, even though an increase in soluble As(III) is commonly observed upon the onset of anoxia (1, 8, 52, 53). In anaerobic environments, DIRB-mediated reductive dissolution of iron minerals would likely result in an increase in As(V) concentrations, provided DIRB were not also capable of reducing As(V) (14). However, if dissimilatory arsenate-reducing organisms were also present and active, solubilized As(V) could be readily converted into As(III).

Our laboratory has demonstrated that CDAL sediments are highly reduced (16) and support biotic reduction of As(V) (28). We have hypothesized that this results from dissimilatory arsenate reduction. Dissimilatory arsenic-reducing bacteria (DAsRB) couple the reduction of As(V) to the oxidation of an organic compound or H2 and thereby conserve energy for growth (33, 46, 72). Most probable number estimates suggest that the number of cultivable DAsRB in this environment ranges from 103 to 105 cells/g (wet weight) of sediment (28). Several studies of dissimilatory arsenate reduction suggest that this transformation is likely to play a role in mobilizing arsenic from ferric oxyhydroxide minerals (3, 19, 28, 83). Incubation of either sterile As-contaminated sediments or scorodite with a pure culture of the DAsRB Sulfurospirillum arsenophilum MIT-13T resulted in elevated aqueous-phase As(III) concentration (3). When the DAsRB Sulfurospirillum barnesii strain SES-3T was incubated with As(V) that was either coprecipitated with or adsorbed to poorly crystalline iron oxyhydroxide minerals, approximately half of the resulting arsenite was retained in the solid phase and the other half was released into solution (83). The few known DAsRB are remarkable for their phylogenetic diversity and metabolic versatility (see Fig. ​Fig.5A)5A) (Table ​(Table1).1). This suggests that the capacity to couple growth to As(V) reduction may be widespread. If further investigation confirms that this trait is broadly distributed among the Bacteria and Archaea and that such organisms are abundant and active, DAsRB may play essential roles in mediating the reductive portion of the arsenic cycle. 



TABLE 1

Summary of relevant physiological characteristics of previously published DAsRBa 





FIG. 5

(A) Unrooted phylogenetic tree showing the positions of currently recognized As(V)-reducing microorganisms (in bold) among the major lines of prokaryotes. The tree is based on an optimized global tree reconstructed from almost full-length SSU rRNA gene ...



We hypothesized that the biotic generation of As(III) observed in CDAL sediment microcosms (28) arose from the activity of dissimilatory arsenate-reducing bacteria, and we sought to enrich such organisms from CDAL sediments. From thermodynamic considerations, we hypothesized that formate could serve as both the electron donor and carbon source for As(V) reduction and that energy from this reduction could be conserved for growth. Insofar as no characterized DAsRB have been enriched from CDAL and no characterized DAsRB are capable of growth on formate alone, we proposed that a formate-oxidizing DAsRB recovered from CDAL sediments would be phylogenetically distinct from previously characterized arsenate-reducers. Lastly, we hypothesized that As(V)-reducing organisms enriched from these Fe-rich sediments would also be capable of obtaining energy for growth by dissimilatory Fe(III) reduction. Such an organism could be expected to mediate diagenesis of both arsenic and iron.

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Isolation and Characterization of a Novel As(V)-Reducing Bacterium: Implications for Arsenic Mobilization and the Genus Desulfitobacterium

Development of an approach to the assessment of sediment quality in Florida coastal waters.

Introduction, A. Mudroch and S.D. MacKnight Project and Data Review, A. Mudroch and S.D. MacKnight Selection of Bottom Sediment Sampling Stations, S.D. MacKnight Bottom Sediment Sampling, A. Mudroch and S.D. MacKnight Sampling the Settling and Suspended Particulate Matter, F. Rosa, J. Bloesch, and D.E. Rathke Sediment Preservation, Processing, and Storage, A. Mudroch and R.A. Bourbonniere Sediment Pore Water Sampling, D.D. Adams Case Studies, J.M. Azcue, J.R.D. Guimaraes, A. Mudroch, P. Mudroch, and O. Malm

Alena Mudroch

Papers

Handbook of Techniques for Aquatic Sediments Sampling

Bottom Sediment Sampling