ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1932.tb00695.x

出版商:Blackwell Publishing Ltd    

年代:1932

数据来源: WILEY

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1932.tb00696.x

出版商:Blackwell Publishing Ltd    

年代:1932

数据来源: WILEY

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1932.tb00697.x

出版商:Blackwell Publishing Ltd    

年代:1932

数据来源: WILEY

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1932.tb00698.x

出版商:Blackwell Publishing Ltd    

年代:1932

数据来源: WILEY

摘要:

Summary.1The lakes visited by the expedition are situated on the floor of the Great Rift Valley.2Owing to the prevalence of soda springs and to the high soda content of the volcanic lava, of which the country is largely composed, these lakes are all relatively alkaline. Their alkalinity is due mainly to sodium carbonate.3The high alkalinity of the water is due in some case8 (c.g. Lake Rudolf) mainly to evaporation from a previously much greater volume. In others (e.g. Lake Edward) the inflow of watcr of high soda content is chiefly responsible.4Some fifteen lakes were visited, of which the least alkaline WM Lake George in Uganda (alkalinity 0.002 N., midday pH 9.9) and the most alkaline Lake Maseche in Uganda (alka,linity 0.71 N., midday pH over 10.5).5The relatively low alkalinity 01 the waters of Lakes Naivasha and Baringo is probably due to the existence of underground outlets.6The reduction in concentration of calcium and magnosiuin due to the lligh alkalinity is not sufficiently great to conrtitutt, a biologically limiting factor.7Neither the silicate nor the phosphate content of theso waters wcts suficicntly low to limit the life of phytoplankton. A possible exception was thc water of Laku Naivasha in which the phosphate content was at one period very low.8Phytoplankton.(a) Arthrospira (Cyanophyceae) was found only in wators of an alkalinity greater than 0.06 N. In the most alkitline lakes they were present in sufficient numbers to make the wakr bright green in colour.(b) Other algae were found only in waters of an alkalinity of 0.06 N. and less.(c) There was some evidence that waters of it high organic content were a favourable environment for Microcystis and Aphanocapsu (Cyanophyceae).9Zooplankton.NO zooplankton other than rotifers was found in waters of a higher ctlkalinity than 0.1 K. Certain rotifem can withstand water of very high alkalinity and salinity.10Certain fish. particularly Tilapia, are able to live in water of an alkalinity and salinity apparently toxic to the majority of fish living in these lakes (alk. 0.1 N).11It is not certain whether the high pH or the high salinity is the more important. factor liniiting the fauna and flora in very alkaline lakes.12The absence of layering of the waters in the majority of lakes investigated was attributed to the prevalence of 1ic.ttvy winds in tho Rift Valley. It is suggested that the layering of the deep waters of Lake Edward, which was accompanied by a thermocline at 40 to 70 metres, was due to the presence of a layer of water of high salinity underlying a layer of less dense

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1932.tb00699.x

出版商:Blackwell Publishing Ltd    

年代:1932

数据来源: WILEY

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1932.tb00700.x

出版商:Blackwell Publishing Ltd    

年代:1932

数据来源: WILEY

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1932.tb00701.x

出版商:Blackwell Publishing Ltd    

年代:1932

数据来源: WILEY