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Ronald Osinga Arjen J. Kop Gerard C. A. Duineveld Rudolf A. Prins Fleur C. Van Duyl 《Journal of Sea Research》1996,36(3-4)
Benthic oxygen uptake, sulphate reduction and benthic bacterial production were measured at two contrasting locations in the southern North Sea: the shallow and turbulent Broad Fourteens area in the Southern Bight, and the deeper Oyster Grounds, a deposition area, where thermohaline stratification occurs during summer. Oxygen uptake and sulphate reduction showed a clear seasonal pattern in the Broad Fourteens area, indicating a supply of carbon to the benthic system that is closely related to the standing stock of carbon in the water column. This close benthic-pelagic coupling is probably due to the influence of the tide in this part of the North Sea, which keeps the water column permanently mixed. At the Oyster Grounds, no seasonal pattern was observed. Peaks in oxygen uptake and sulphate reduction were found in winter. Irregularly occurring events, such as storms and fishery-related activities, are likely to affect the benthic mineralization patterns in this area. Annual benthic carbon mineralization rates estimated from oxygen uptake rates were 44 gC·m−2 at the Broad Fourteens, and 131 gC·m−2 at the Oyster Grounds, of which 26 and 28%, respectively, could be attributed to sulphate reduction (assuming an annual sulphide reoxidation rate of 100%). Although sulphate reduction rates in the southern North Sea are higher than previously suggested, aerobic respiration is the most important pathway for benthic carbon mineralization at the stations visited. Production rates of benthic bacterial carbon measured with labelled leucine were much higher than carbon mineralization rates based on oxygen uptake or sulphate reduction. This may either imply a very high bacterial carbon conversion efficiency, or point to shortcomings in the accuracy of the techniques. A critical evaluation of the techniques is recommended. 相似文献
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Seasonal ecosystem variability in remote mountain lakes: implications for detecting climatic signals in sediment records 总被引：5，自引：0，他引：5
J. Catalan M. Ventura A. Brancelj I. Granados H. Thies U. Nickus A. Korhola A.F. Lotter A. Barbieri E. Stuchlík L. Lien P. Bitušík T. Buchaca L. Camarero G.H. Goudsmit J. Kopáćek G. Lemcke D.M. Livingstone B. Müller M. Rautio M. Šiško S. Sorvari F. Šporka O. Strunecký M. Toro 《Journal of Paleolimnology》2002,28(1):25-46
Weather variation and climate fluctuations are the main sources of ecosystem variability in remote mountain lakes. Here we describe the main patterns of seasonal variability in the ecosystems of nine lakes in Europe, and discuss the implications for recording climatic features in their sediments. Despite the diversity in latitude and size, the lakes showed a number of common features. They were ice-covered between 5–9 months, and all but one were dimictic. This particular lake was long and shallow, and wind action episodically mixed the water column throughout the ice-free period. All lakes showed characteristic oxygen depletion during the ice-covered-period, which was greater in the most productive lakes. Two types of lakes were distinguished according to the number of production peaks during the ice-free season. Lakes with longer summer stratification tended to have two productive periods: one at the onset of stratification, and the other during the autumn overturn. Lakes with shorter stratification had a single peak during the ice-free period. All lakes presented deep chlorophyll maxima during summer stratification, and subsurface chlorophyll maxima beneath the ice. Phosphorus limitation was common to all lakes, since nitrogen compounds were significantly more abundant than the requirements for the primary production observed. The major chemical components present in the lakes showed a short but extreme dilution during thawing. Certain lake features may favour the recording of particular climatic fluctuations, for instance: lakes with two distinct productive periods, climatic fluctuations in spring or autumn (e.g., through chrysophycean cysts); lakes with higher oxygen consumption, climatic factors affecting the duration of the ice-cover (e.g., through low-oxygen tolerant chironomids); lakes with higher water retention time; changes in atmospheric deposition (e.g., through carbon or pigment burial); lakes with longer stratification, air temperature changes during summer and autumn (e.g., through all epilimnetic species). 相似文献
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Jordi Catalan Sergi Pla-Rabés Alexander P. Wolfe John P. Smol Kathleen M. Rühland N. John Anderson Jiři Kopáček Evžen Stuchlík Roland Schmidt Karin A. Koinig Lluís Camarero Roger J. Flower Oliver Heiri Christian Kamenik Atte Korhola Peter R. Leavitt Roland Psenner Ingemar Renberg 《Journal of Paleolimnology》2013,49(3):513-535
Over recent decades, palaeolimnological records from remote sites have provided convincing evidence for the onset and development of several facets of global environmental change. Remote lakes, defined here as those occurring in high latitude or high altitude regions, have the advantage of not being overprinted by local anthropogenic processes. As such, many of these sites record broad-scale environmental changes, frequently driven by regime shifts in the Earth system. Here, we review a selection of studies from North America and Europe and discuss their broader implications. The history of investigation has evolved synchronously with the scope and awareness of environmental problems. An initial focus on acid deposition switched to metal and other types of pollutants, then climate change and eventually to atmospheric deposition-fertilising effects. However, none of these topics is independent of the other, and all of them affect ecosystem function and biodiversity in profound ways. Currently, remote lake palaeolimnology is developing unique datasets for each region investigated that benchmark current trends with respect to past, purely natural variability in lake systems. Fostering conceptual and methodological bridges with other environmental disciplines will upturn contribution of remote lake palaeolimnology in solving existing and emerging questions in global change science and planetary stewardship. 相似文献
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Fleur C. van Duyl Winfried W. C. Gieskes Arjen J. Kop Wilma E. Lewis 《Journal of Sea Research》1998,40(3-4)
In the spring of 1995, short-term variations in the concentration of particulate and dissolved dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) were monitored in the western Wadden Sea, a shallow coastal region in open connection with the North Sea. Significant correlations were found between abundance of Phaeocystis globosa and particulate DMSP; concentrations increased rapidly from 100 to 1650 nM in the middle of April. Highest DMS concentrations were found during the initial phase of the exponential growth of the bloom. DMS production and loss rates of DMSP and DMS were estimated experimentally during various phases of the bloom. DMS production and consumption were roughly in balance, with production only slightly exceeding consumption at the start of the bloom. Rates of production and consumption were highest during the exponential growth phase of Phaeocystis and declined in the course of the bloom (from 300–375 to less than 5 nmol dm−3 d−1). Demethylation of DMSP increased during the bloom (from 11 to 1300 nmol dm−3 d−1); it accounted for up to 100% of the DMSP loss at the end of the bloom. The shift from DMSP cleavage to demethylation in the course of a Phaeocystis bloom implies that DMS concentrations are not necessarily highest at the peak or towards the end of blooms. 相似文献
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The spatial and temporal dynamics of monsoon in the Holocene has been reconstructed for the Lower Amur area. Four stages of cooling are determined (10300–10800, 8000–8300, 4200–4600 and 2500 yrs. ago). During these periods the intensity of the summer monsoon was weakest. The conventional northern boundary of monsoon influence moved from 54 to 48o N. Two retrospective scenarios of the interaction versions of interaction of seasonal atmospheric centers are suggested, which had influence on the dynamics of the cyclone process over the southern part of the Far East in the Holocene. The cyclones attenuated as a result of frequently recurring long-lasting periods of an increase in pressure in the region of the summer Far-Eastern and Asian depressions, and a decrease in pressure over the Sea of Okhotsk as well as the displacement of the center of the Okhotsk anticyclone toward southern latitudes, which was often in a quasi-stationary state blocking the passage of cyclones to the southern coast of the Sea of Okhotsk. In either case, the cyclones were forced away to lower latitudes and intensified over northern and eastern regions of China. The two scenarios could work both synchronously and metachronously. 相似文献
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Stephen A. Norton Randall H. Perry Jasmine E. Saros George L. JacobsonJr. Ivan J. Fernandez Jiří Kopáček Tiffany A. Wilson Michael D. SanClements 《Journal of Paleolimnology》2011,46(1):107-122
The sediment record from a 5.3-m core from Sargent Mountain Pond, Maine USA indicates strong co-evolutionary relationships
among climate, vegetation, soil development, runoff chemistry, lake processes, diatom community, and water and sediment chemistry.
Early post-glacial time (16,600–12,500 Cal Yr BP) was dominated by deposition of mineral-rich sediment, low in organic matter
and secondary hydroxides of Al and Fe; pollen indicate tundra conditions; diatom taxa indicate pH between 7.5 and 8, and total
P concentrations of about 25 μg L−1, favoring higher productivity. Chemical weathering was rapid, with high alkalinity, pH, Ca, and P in runoff. As climate ameliorated,
about 12,500 Cal Yr BP, forest vegetation became established; soils would have developed vertical zonation, including organic
matter accumulation, and incipient podzolic horizons, with accumulating secondary hydroxides of Al and Fe that sequestered
P in the soils. Labile minerals (primarily apatite, Ca5(PO4)3(OH,F,Cl)) became depleted in the soil, further reducing the supply of P to the lake. Dissolved organic carbon (DOC) from
soil organic matter mobilized Al and Fe to the lake where Al(OH)3 (primarily) and Fe(OH)3 (minor) were precipitated. The sedimenting hydroxides adsorbed P from the water column, further reducing bioavailable P.
These long-term trends of moderating climate, and changing terrestrial biology, soils, and aquatic chemistry and phytoplankton
were interrupted by the 1,000-year long Younger Dryas cooling, which led to a temporary reversal of these processes, a period
that ended with the major onset of Holocene warming. The sequestration of P by soils would have strengthened because of long-term
soil acidification and pedogenesis. The lake was transformed from a more productive, high P, high pH, low DOC system into
an oligotrophic, relatively low P, acidic, humic lake over a period of 16,600 years, a natural trend that continues. In contrast
to many human-affected lakes that become increasingly eutrophic, many lakes become more oligotrophic during their history.
The precursors for that are: (1) absence of human land-use in watersheds, (2) bedrock lithology and soil with a paucity of
soluble Ca-rich minerals, and (3) vegetation that promotes the accumulation of soil organic matter, podzolization, and increased
export of metal-DOC complexes, particularly Al. 相似文献
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Acidification in European mountain lake districts: A regional assessment of critical load exceedance 总被引：1，自引：0，他引：1