ISSN:0020-9309    

DOI:10.1002/iroh.3510610527

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY

摘要:

AbstractOxygen deficits, rates of oxygen depletion, and Secchi disk measurements were the major indices examined in this study to determine trends in trophic conditions in Lakes Mendota, Monona, and Waubesa near Madison, Wisconsin. On the basis of available data, there is little that can be said reliably with respect to documenting eutrophication, particularly in Lake Mendota in the past several decades, that could not be attributed to normal variability. Better evidence for eutrophication comes from cores of some of the lakes.A comparison of oxygen deficits without simultaneous information on mean hypolimnetic temperatures and the lateness of ice out may provide a misleading interpretation of trophic variations over time.

ISSN:0020-9309    

DOI:10.1002/iroh.3510610502

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY

摘要:

AbstractMany sampling stations are preferable in sediment investigations. With a basis of only single samples an unequivocal determination of the lake's sediment character is hard to obtain. Knowledge of the morphometrical conditions is an advantage, as in steeply sloping parts great changes in concentrations can occur. However, even unexpected distribution patterns can emerge and a map of horizontal distributions in sediments can never be looked upon as completely reliable. The traditional sediment picture (based on dry weight) with increasing concentrations of several elements with depth can often give a false impression of the distribution of amounts per volume wet sediment with maximum values in somewhat shallower parts which, from an ecological point of view, should be the important one.

ISSN:0020-9309    

DOI:10.1002/iroh.3510610503

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY

摘要:

AbstractThis paper is devoted to the varying concentrations of 49 elements found in the water from three littoral sites and one pelagic site, sampled over a five hour period, in Lake Lacawac. These elements were detected in concentrated water samples by use of X‐ray emission and optical emission spectroscopy. The elemental concentrations of the four sampling sites differed. Statistical analyses were used to estimate how chemical mixing proceeded in the surface waters of the lake. Results from a previous study of the chydorid Cladocera living in the sediments beneath the water sampling sites indicated that the more organic sediments contained more individuals than the sandy sediments. The chemical concentration of the water followed the same distribution as did the organism

ISSN:0020-9309    

DOI:10.1002/iroh.3510610504

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY

摘要:

AbstractIn the past many authors have described mathematical models of limnic ecosystems by means of differential equations and time‐stationary statistical methods. But an accurate description of the ecosystem processes is only possible by time‐varying methods. Approaching deterministic techniques often leads to hardly computable nonlinear differential equations with distributed parameters.In this paper recursive estimation methods of ecosystems modeling in real‐time are presented and first results of the application to Saidenbach reservoir are given. In practice the oxygen balance of the surface and of two lower layers (depth 10 m and 35 m) of the reservoir was modeled. The structure of all models was p‐canonic with oxygen as output and temperature, oxygen deficiency (BOD2), seston, chlorophyll, nitrate‐nitrogen, COD(Mn), phosphate (PO4) as inputs on each level. For surface model the Secchi disk‐transparency was used as an addit

ISSN:0020-9309    

DOI:10.1002/iroh.3510610505

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY

摘要:

AbstractThe turbulence correction terms for the photosynthetic oxygen production of phytoplankton given by BAUMERT(1974) are used for the case that the variations in velocity are exponentially autocorrelated. In case of theP(I)‐relation by STEEMANNNIELSENone can show that the value of the relative correction term is — in the worst case — less than, or equal to 1% if the depth of epilimnion (mixing depth) and the light intensity at the water surface are high.The demand for weak turbulence and light extinction — necessary for validity of the equations — is met for some real objects, especially for oligotrophic seas

ISSN:0020-9309    

DOI:10.1002/iroh.3510610506

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY

摘要:

AbstractThe authors give here a qualitative and quantitative description of the phytoplancton in the brackish waters of the St. Lawrence Upper Estuary (Québec). The very high observed concentrations are the responsibility of fresh‐water forms:Skeletonema subsalsum, Melosira binderana, Diatoma elongatum, Asterionella formosa, Fragilaria crotonensis, F. capucina, Cyclotella striata, Melosira islandica, Ankistrodesmus falcatusandScenedesmus quadricauda;193 species are listed in an append

ISSN:0020-9309    

DOI:10.1002/iroh.3510610507

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY

摘要:

AbstractConditions governing the utilization of glucose by the pelagic communities of the Northwest Mediterranean have been studied and it is concluded that (1) the vertical distribution of heterotrophic activity first reaches a maximum at about 50 m, close to the maximum of the phytoplankton while a second maximum occurs at 150 m; furthermore, within the first 200 m, the mineralization of carbon is almost complete and (2) the response of the microorganisms to increasing amounts of substrate follows the kinetic law of MICHAELIS‐MENTE

ISSN:0020-9309    

DOI:10.1002/iroh.3510610508

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY

摘要:

AbstractBy using autoradiographic examination of14C labeled viable cells, natural phytoplankton communities were separated into living and non‐living components. Comparisons of carbon to adenosine triphosphate (ATP) content of living cells yielded consistent ratios with depth, during periods of high and low nutrient supply at Lake Tahoe. Over time the ratio fluctuated by no more than ± 17% of the mean between the time of maximum nutrient supplies and nutrient depletion. The viability of specific phytoplankton groups was surprisingly low at times, indicating that conventional counting methods tend to overestimate live biomass. A survey of lakes differing in trophic states and having diverse phytoplankton and bacterial assemblages has shown that ATP measurements can be used as an accurate measure of total living microbial bioma

ISSN:0020-9309    

DOI:10.1002/iroh.3510610509

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY

摘要:

AbstractThe photosynthetic rates ofEnteromorpha intestinalis, Fucus vesiculosusandLaminaria saccharinafrom the Baltic Sea were measured in different salinity range of Medium A (with NaHCO3) and Medium B (without NaHCO3). Photosynthetic activity in Medium A showed higher values than those in Medium B. The materials pretreated for one day showed a higher O2output than those untreated at almost every salinity range. In a chloride loss experiment the pretreated thalli ofPorphyra umbilicalis, Fucus vesiculosusandLaminaria digitatawere placed for a three minute period in distilled water. The excreted chloride ion content showed a higher value in sublittoral species after hypotonic and hypertonic treatment than in intertidal species.

ISSN:0020-9309    

DOI:10.1002/iroh.3510610510

出版商:Akademie Verlag, Berlin    

年代:1976

数据来源: WILEY