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Über dieses Buch

This volume synthesizes the relevant data that is fundamental to our understanding of trace metal biogeochemistry and the ecology of biological communities of deep-sea vent systems. It presents the combined results of biological and geochemical research and analyzes the microdistribution of animals and the spatial structure of vent communities. Careful consideration is given to the export of iron and other trace metals from hydrothermal vents. The environmental conditions to be found in deep-sea hydrothermal community habitats, along with the trace metal behavior in biotope water are characterized and the sources and forms of trace metals taken up by dominant hydrothermal vent animals are discussed. Special attention is paid to the poorly investigated deep biosphere of the sub-seafloor igneous crust. The book is illustrated with a wealth of exceptional deep-sea photos taken by the manned submersible “Mir”, and a dedicated chapter focuses on the role of deep manned submersibles in ocean research. The book will be of interest to researchers and students in the fields of oceanography, geochemistry, biology, the environmental sciences and marine ecology.

Inhaltsverzeichnis

Frontmatter

Introduction

Over a period of time after discovery in 1977 of the extraordinary abundant faunal assemblages functioning at the deep-sea hydrothermal vent systems, a new knowledge has been gained of highly dynamic and extreme conditions in their habitats. Hydrothermal vent communities have to survive in habitats which are exposed to high heavy metal load, emitting from vents and dispersing into ambient water and changing physicochemical parameters. All these processes are reflected in the distribution pattern of bottom communities along the gradients of reduced substances that serve a basement for chemosynthetic primary productivity. In the book we aimed to summarize available data, which are of fundamental interest for understanding the trace metal biogeochemistry and ecology of biological communities of deep-sea vent systems. Along with, some interesting aspects of the subseafloor biosphere are considered.
This book is addressed to the specialists working in various fields of environmental problems, especially in marine biogeochemistry and ecology.
Sergey V. Galkin, Liudmila L. Demina

The Export of Iron and Other Trace Metals from Hydrothermal Vents and the Impact on Their Marine Biogeochemical Cycle

Recently the role of hydrothermalism as a significant source for several bioactive trace metals in their dissolved form has become evident through numerous GEOTRACES ocean basin transects and other studies. Especially iron (Fe) has found much attention due to its important role as a limiting micronutrient in about 40% of the global surface ocean. Organic complexation has been confirmed as one of the processes stabilizing the dissolved phase of Fe and other trace metals from forming insoluble (oxy)hydroxides or being scavenged on these surface active particulate phases. Small colloidal metal phases can also enhance transport of dissolved metals from vents into the ocean. However, hydrothermalism is not only a source for dissolved trace metals into the ocean basins but for some it is also a sink. Particulates forming in hydrothermal plumes, especially Fe and Mn ox(yhydrox)ides, are very efficient scavengers of other trace metals and were found to bind PO4 3−, V, As, REE (rare earth elements), Th, plus other elements from seawater. The linkage between the hydrothermal dissolved, soluble and colloidal phases, as well as the particulate phase in the non-buoyant plume is not a simple thermodynamic equilibrium and our knowledge about biological processes involved is still in its infancy. The oceanic iron and carbon cycles are inseparable from each other and observations as well as modeling approaches have shown that in some areas hydrothermal iron input is needed to balance the iron required to explain global marine primary productivity. On the other hand it has also been demonstrated that the precipitation of iron (oxy)hydroxides will coprecipitate organic carbon causing a removal flux of dissolved organic carbon not only from the hydrothermal vent but also from the deep-ocean water. This particulate organic carbon flux is a significant source of organic carbon in the basin sediments. After a long period of underestimating the importance of deep-sea hydrothermal vents for the biogeochemical cycling of iron and other trace metals in the global ocean today much effort is put into this emerging field of research. Especially the role of shallow island arcs for direct hydrothermal trace metal input into the productive zone promises to become an exciting field of studies.
S. G. Sander, A. Koschinsky

Geologic-Geochemical and Ecological Characteristics of Selected Hydrothermal Areas

In this paper we consider geologic-geochemical and ecological characteristics of the areas where the material for biogeochemical study (Demina, Trace metals in water in the hydrothermal biotope. Hdb Env Chem. doi:10.​1007/​698_​2016_​1; Demina, Galkin, Factors controlling the trace metal distribution in hydrothermal vent. Hdb Env Chem. doi:10.​1007/​698_​2016_​5) has been collected. In the Atlantic Ocean five hydrothermal areas (Menez Gwen, Rainbow, Lost City, Broken Spur, and Snake Pit) have been investigated. In the Pacific Ocean the 9°50′N vent area at the East Pacific Rise and hydrothermal manifestations in Guaymas Basin (Gulf of California) were studied. Observations and sampling were provided in 1996–2005 during numerous cruises of RV “Akademik Mstislav Keldysh” using deep-sea manned submersibles “Mir.” Explored vent areas exhibit a wide range of environmental conditions, including great variation in depth (particularly on the MAR), associated physical parameters, and different geologic setting and underlying rocks. Faunal communities also vary greatly in taxonomic composition and spatial structure. Short characteristic of abiotic environment and structure of benthic communities is given for each explored area. With all the variety of hydrothermal manifestations, in the spatial structure of communities a number of general patterns can be revealed. At the analysis of bioaccumulation function of vent organisms in the case of each area particular habitat conditions and characteristics of spatial structure of communities (microdistribution of animal’s populations, their association with a specific temperature zone and a particular type of substrate) must be taken into account.
Sergey V. Galkin, Liudmila L. Demina

Trace Metals in the Water of the Hydrothermal Biotopes

Hydrothermal vents on the ocean floor are surrounded by geochemical barriers that have been caused by extreme gradients of water temperature and concentrations of reduced compounds as well as trace metals. Now it is known that water of the faunal hydrothermal biotopes consists mostly of the diluted hydrothermal fluids while the biological communities concentrate many trace metals due to bioaccumulation processes. Thus the deep-sea hydrothermal vent fields represent geochemically interesting areas where processes of trace metal dispersion and concentration coexist. In spite of the numerous publications on hydrothermal fluid biogeochemistry, some unsolved problems caused by the complexity of hydrothermal systems still remain. In this chapter, an attempt is made to summarize the available data on the trace metal distribution in the water of hydrothermal vent community habitats. These data allow us to understand that there is a difference in trace metal concentration in the water of biotopes of the different vent sites. Here a trace metal chemical speciation in the water of biotope is considered briefly as soon as it influences the ability of hydrothermal organisms to accumulate trace metals.
Liudmila L. Demina

Structure of Hydrothermal Vent Communities

Deep-sea hydrothermal vent communities are characterized by complicated taxonomic, trophic, and spatial structure. Different animals consume chemosynthetic bacterial production to a variable extent and by different ways. Different animal groups demonstrate variable degree of adaptations to the extreme environment of hydrothermal vent systems. According to their ecological requirements, vent animal populations occupy different zones within the vent field. The boundaries of different vent fauna assemblages could be rather sharp or feebly marked appearing to be defined by gradients of water chemistry as well as the hydrodynamic regime within the vent field. To ensure the correct analyses of bioconcentration function (BCF) of vent organisms, such factors as taxonomic position, trophic specialization, patterns of physiology, ontogenetic stages, and spatial disposition of animal population within the vent field should be taken into consideration.
S. V. Galkin

Sources and Forms of Trace Metals Taken Up by Hydrothermal Vent Mussels, and Possible Adaption and Mitigation Strategies

Vent mussels are ubiquitous in most hydrothermal fields, despite the metal-rich environment they live in, with dissolved metal ions, colloidal and particulate metal forms in concentrations orders of magnitude higher than in ambient seawater. Different studies at various hydrothermally active sites on the Mid-Atlantic Ridge and East Pacific Rise have shown that metal concentrations in the tissues of the mussel generally reflect metal loads of their environments, displaying spatial gradients, with bioconcentration factors up to 105. Gills and digestive glands accumulate the highest amounts of metals, which is related to their direct role in food uptake, while mantle and foot show moderate metal enrichments. Metal uptake in the form of mineral particles has been identified as an important source of metals in the mussel tissues. While closer to the active vent sites metal sulfides forming during mixing of hot hydrothermal fluid and seawater are more dominant, with increasing distance iron oxides with metals adsorbed from seawater play a more important role for metal accumulation by the vent mussels. Although the shells of hydrothermal mussels have low metal concentrations compared to the soft tissues, they are a record of the chemical composition of the seawater – hydrothermal fluid mixture. Different species of Bathymodiolus mussels from the Pacific and Atlantic display similar metal accumulations and adaptation strategies, while vent clams show some similarities, but also some differences compared to Bathymodiolus.
Some of the metals (e.g., alkali and earth alkaline elements, Zn and Mn) taken up by the mussels appear to be bioregulated. They are essential elements and their concentration ranges in the mussel tissues are usually less variable than other heavy metals, although their variability in the fluids is comparably high. Strategies of the vent mussels to cope with high concentrations of potentially toxic metals such as Cu, Cd, and Hg include binding to metallothioneins, which are strongly metal-binding proteins, and possibly immobilization of the metals in the form of granules stored in the tissue. These ways of mitigating heavy metal toxicity have also been found for other organisms including non-vent bivalves. Another yet to be proven possibility is the excretion of organic ligands into the water which binds to the metals and makes them less bioavailable.
Due to the challenges of sampling hydrothermal vent mussels and their environmental compartments, many questions remain open or hypotheses still need to be tested; studies often differ in their approach and a comparison of results is not straightforward. Hence, more systematic studies focusing on specific metal groups, experiments under defined conditions and a comparison of different species of vent mussels are desirable. Apart from the many open questions that refer directly to the understanding of metal accumulation and adaptation of hydrothermal vent mussels to their challenging environment, a better knowledge in this field may also help to support other fields of research. These include estimation of hydrothermal metal fluxes into the ocean and elucidation of survival strategies of organisms in other metal-rich environments.
Andrea Koschinsky

Factors Controlling the Trace Metal Distribution in Hydrothermal Vent Organisms

Despite the numerous published data, the evaluation of the various conditions, influencing the trace metal distribution and accumulation in the different hydrothermal organisms, is not completed up till now. In this chapter we aimed to clear out the influence of the main factors, affecting the trace metal bioaccumulation in the deep-sea hydrothermal vent biota: environmental factors, acting outside the organisms, and biological ones, acting inside the organisms and within the biological communities. Among the environmental conditions there are such site-specific differences as depth, temperature, and fluid chemical composition that control trace metal concentrations in water of the biotope, as well as mineralogical features of substratum. Meanwhile the biogenic factors include stage of ontogenesis, species differences, trophic level and feeding type, and etc. For this purpose we consider data on the Fe, Mn, Zn, Cu, Cd, Pb, Ag, Ni, Co, Cr, As, Se, Sb, and Hg concentrations in the benthic organisms inhabiting the following hydrothermal vent fields at the Mid-Atlantic Ridge (MAR): Menez Gwen, Rainbow, Lost City, Broken Spur, as well at the 9°50′N at the East Pacific Rise (EPR), and the Guaymas Basin (Gulf of California). To clarify some of the influencing factors, we have aimed to summarize the available data on factors that control the trace metal distribution in hydrothermal vent organisms, including not only Bathymodiolus mussels, but also other dominant organisms, such as Rimicaris shrimps, vestimentiferan tube worms Riftia pachyptila, whose feeding strategy relies on microbial symbiotrophy. Distribution patterns of some trace metals studied in different taxa gave an evidence of the influence of environmental and biological parameters on their bioaccumulation in the hydrothermal vent organisms.
Liudmila L. Demina, Sergey V. Galkin

The Deep Biosphere of the Subseafloor Igneous Crust

The igneous portion of the subseafloor crust is considered to be the largest potential microbial habitat on Earth; thus, it is somewhat of a paradox that our knowledge regarding its abundance, diversity and ecology is sparse, close to non-existent. This is mainly due to issues involved in sampling live species, and therefore much of our present knowledge of the deep biosphere is based on a fossil record. However, drilling and sampling techniques are constantly being developed to facilitate sampling of live microorganisms, and recent molecular studies show a positive progress towards better recovery and less contamination. Here we discuss the subseafloor igneous crust as a microbial habitat, its physical and geochemical prerequisites to support life and what type of life that could sustain in such an extreme environment. We also discuss what the fossil record, and the few successful molecular studies, tells us regarding what type of microorganisms exist in the deep subseafloor settings. It appears as if the igneous crust is more diverse than previously expected consisting of both prokaryotes and eukaryotes in close interplay with each other and their physical environment. As our knowledge increases so does the questions, and hopefully future technique development can provide us with an increased understanding of this deep, hidden world.
Magnus Ivarsson, N. G. Holm, A. Neubeck

Manned Submersibles Mir and the Worldwide Research of Hydrothermal Vents

The role of deep manned submersibles (DMSs) in scientific research of the ocean is considered. The history of development of DMS is introduced, drawing attention on the steps, generated by submarine accident (“Thresher”) and scientific research jumps (hydrothermal vent discovery). Development of the building of DMS in Russia and particularly in P. P. Shirshov Institute of Oceanology, RAS, is considered, concentrating on worldwide research with “Pisces VII” and “Pisces XI” submersibles in 1970–1980s of the twentieth century.
Short description of Mir-1 and Mir-2 design is introduced, as the best 6,000 m DMS in the world.
The introduction of scientific research of hydrothermal fields on ocean bottom, using the Mir submersibles, is done. The methodology of hydrothermal field study, using the Mir submersibles, is described.
Anatoly M. Sagalevich

Conclusions

The recent 10 years are characterized by a marked success in our knowledge of the marine trace metal biogeochemistry, resulted from the International GEOTRACES Program (http://​www.​geotraces.​org) ocean basin transects, including the areas of the mid-ocean ridges. Meanwhile, it is the authors’ opinion that now it’s time to summarize available data on trace metal biogeochemistry in the deep ocean hydrothermal vent ecosystems. In this book we aimed to outline some features that control processes of metal input from the deep-sea hydrothermal vents followed by their transport, dispersion in the ambient seawater, and biological accumulation. An important contribution in the biogeochemical research is associated with knowledge of the biological structure of bottom fauna inhabiting vent areas, as well as with deep biosphere of the subseafloor igneous crust. Some outlooks for the future research are proposed.
Liudmila L. Demina, Sergey V. Galkin

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