摘要:

AbstractFour commonly used formulae for measuring percentage similarity (PS) of biological communities were tested for their usefulness in relating to two plankton community properties, species proportional differences and total density differences. The formula best combining species proportionality and total density in the expression ofPSis new:\documentclass{article}\pagestyle{empty}\begin{document}$$ PS = 1/2[\sum\limits_i {\min \,(x_i ,\,y_i )] + 1/2\left[ {100 - \frac{{100}}{{\sum\limits_i {z_i } }}\,|\,\sum\limits_i {x_i } - \sum\limits_i {y_i \,|} } \right]} $$\end{document}where min (xi,yi) is the lesser percentage (doubly standardized) of a species in two samples X and Y and where 2 q, 2xi and 2yi are the total quantities of all species in samples 8,X and Y, where\documentclass{article}\pagestyle{empty}\begin{document}$ \sum\limits_i {z_i } ,\,\sum\limits_i {x_i } \,and\sum\limits_i {y_i } $\end{document}are the total quantities of all species in samples Z, X and Y, respectively. Sample 2 contains the highest density of all species in the set;\documentclass{article}\pagestyle{empty}\begin{document}$ \sum\limits_i {z_i \,>\,(\sum\limits_i {x_i ,\,} \sum\limits_i {y_i } )} $\end{document}.The new expression of PS is simple to use and has the additional advantage of offering the analyst an unlimited choice of weighting factors or importance values for proportionality of species content and total density. The method has been applied to data from Gravenhurst Bay (Ontario) and effectively demonstrates the consequences of phosphorus loading reductions for phytoplankton communities.

ISSN:0020-9309    

DOI:10.1002/iroh.19850700502

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractMethods of formalizing trophic interactions within plankton communities are discussed on the basis of correlations observed between prey size and specific and age‐dependent features of the consumer. The nature of the functional reaction of copepods to changes in food quality is specific to the different age groups. Allometric types of relation between food ration and body size cannot describe these phenomena. An alternative method based on the notions of minimum, maximum and optimum prey size changing in the course of ontogeny is suggested. The values of the parameters are identified for the species of Temoridae and Acartiidae (Copepoda, Calanoida), and a range of examples proves satisfactory reproducibility of the experimental data concerning mono‐ and polyphagy. This paper presents a biological interpretation of the parameters that suggest their functional connection with mesh size, mouth size and the ability of copepods to dismember large objects into portions. Optimum food size is expressed as a function of age and size of modal class particles that enabled “switching” of food as a result of changes in the component ratio in the environment and different capturing capabilities to be modelled. Some conclusions resulting from the model are di

ISSN:0020-9309    

DOI:10.1002/iroh.19850700503

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19850700505

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractIt is generally believed that excessive P release from lake sediments, i. e. internal P load, is only a problem in deep lakes with stagnant anaerobic bottom waters. However, substantial amounts of P can also be released from sediments in shallow, well‐mixed lakes. The dynamics and magnitude of P release from sediments in these types of lakes are affected primarily by physical factors, such as seasonal variations in water temperature and year‐to‐year differences in water renewal. These factors, in turn, induce chemical and microbiological processes which regulate the exchange of substances between sediments and water. The fractional distribution of sedimentary P and the chelating capacity of the water are also important factors that can provide insights to the processes involved and their quantitative impact on the P status in shallow, eutrophic

ISSN:0020-9309    

DOI:10.1002/iroh.19850700506

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractThe graph of maximum filtering and grazing ratesversusparticle size shows thatDaphnia hyalinais a microfiltrator andEudiaptomus gracilisis a macrofiltrator. In contrast toEudiaptomus gracilis, Daphnia hyalinais also able to utilize larger bacteria (c. 1 μm3) as a food source

ISSN:0020-9309    

DOI:10.1002/iroh.19850700507

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19850700508

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractIn 1981, experiments to study the toxicity of copper in its ionic, complexed (to humic acid) and adsorbed (on cellulose fibers from a local paper mill) forms on species composition, standing crop, and photosynthesis of phytoplankton were conducted in chemostats with natural aggregations composed mainly of either green algae or of diatoms from the Saguenay River. In the aggregations of green algae, the rates of primary production were more strongly inhibited by copper than were the chlorophyllaconcentrations, whereas the cell numbers, standing crop and rates of primary production of the diatoms were all strongly inhibited by copper.

ISSN:0020-9309    

DOI:10.1002/iroh.19850700509

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19850700510

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractAnadromous Atlantic salmon parr (Salmo salar) were captured from three Newfoundland lakes. Yearling and 2 year parr were captured most often in shallow water<2 m deep around lake perimeters and were not abundant at greater depths. The 3+ and 4+ parr age groups were rarely found inshore (<2 m) but were captured in deeper offshore areas. Though the parr population in one deep lake was too small to be estimated by mark‐recapture, estimates of the yearlings plus 2+ age groups in two shallower lakes were 55 and 63 parr ha−1. respectively. No under yearlings were found in lake habitats. Parr density in the three study lakes varied inversely with mean lake depth. Lacustrine parr growth rate was greater than or equal to that of stream dwelling parr. It is concluded that some shallow lakes of Newfoundland provide major rearing areas for juvenile anadromous Atlantic sal

ISSN:0020-9309    

DOI:10.1002/iroh.19850700512

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19850700513

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY