J. Rzóska – författare

Origin and Aims of this essay It was not by choice but by the misfortunes or fortunes of the last war, that I became involved with rivers. In December 1946 I obtained a lecturing post at the then Gordon Memorial College at Khartoum and the Principal of the college brought me to confluence of the two Niles and urged me to 'do something' on the biology of the river. I was very reluctant, my experience was limited to lakes in Poland up to 1939, and I did not know anything about work on rivers. The 'equipment' was a rowing boat, hired, and a 'home made' plankton net. This limited our first exploratory steps to the immediate vicinity of Khartoum. In both the White and Blue Nile we discovered the presence of a pure plankton. This was contrary to opinions expressed in the limited scientific literature available at Khartoum which stimulated our doubts and the search for the origin of this phenomenon. And so, early in our work, we became aware of the longitudinal sequence of events in running water, a fundamental feature of river ecology. of work were daunting; In the Nile, as in other long rivers, the difficulties the water courses stretch for thousands of kilometers south and north of our base, our work had to be done in time free from lecturing duties, no research grants were available.

Proceedings of a Regional Seminar, on Noxious Aquatic Vegetation, New Delhi, 12-17 December 1973

Origin and Aims of this essay It was not by choice but by the misfortunes or fortunes of the last war, that I became involved with rivers. In December 1946 I obtained a lecturing post at the then Gordon Memorial College at Khartoum and the Principal of the college brought me to confluence of the two Niles and urged me to 'do something' on the biology of the river. I was very reluctant, my experience was limited to lakes in Poland up to 1939, and I did not know anything about work on rivers. The 'equipment' was a rowing boat, hired, and a 'home made' plankton net. This limited our first exploratory steps to the immediate vicinity of Khartoum. In both the White and Blue Nile we discovered the presence of a pure plankton. This was contrary to opinions expressed in the limited scientific literature available at Khartoum which stimulated our doubts and the search for the origin of this phenomenon. And so, early in our work, we became aware of the longitudinal sequence of events in running water, a fundamental feature of river ecology. of work were daunting; In the Nile, as in other long rivers, the difficulties the water courses stretch for thousands of kilometers south and north of our base, our work had to be done in time free from lecturing duties, no research grants were available.

Scope and limitations of this book I am trying here to present the natural history of a land largely created and dominated by two great rivers, the Euphrates and Tigris. All rivers have two main functions, quite different from lakes; they transport water and eroded material sometimes over large distances. The astute Greeks, who penetrated here in the 4th century B.C., called the land Mesopotamia, an apt name; it is the only region in the Near East, except Egypt, having the benefit of large rivers. Another name coined in antiquity was ''Fertile Crescent'', stretching from Egypt to present day Iraq; Herodotus marvelled at the fertility of the soils, the abundance of water and the magnificent cities of Mesopotamia. Thus a further role of some great rivers is recognized as foci of human development. The desire to collate this book arose from a similar motif as in the Nile book (1976), the intricate connection between man and rivers.

Scope and limitations of this book I am trying here to present the natural history of a land largely created and dominated by two great rivers, the Euphrates and Tigris. All rivers have two main functions, quite different from lakes; they transport water and eroded material sometimes over large distances. The astute Greeks, who penetrated here in the 4th century B.C., called the land Mesopotamia, an apt name; it is the only region in the Near East, except Egypt, having the benefit of large rivers. Another name coined in antiquity was 'Fertile Crescent', stretching from Egypt to present day Iraq; Herodotus marvelled at the fertility of the soils, the abundance of water and the magnificent cities of Mesopotamia. Thus a further role of some great rivers is recognized as foci of human development. The desire to collate this book arose from a similar motif as in the Nile book (1976), the intricate connection between man and rivers.

357 Temperature . . . . . . . . . 358 Transparency and light penetration. 360 Salinity and conductivity 363 Major ions . . . . . 365 Dissolved gases and pH 371 Plant nutrients. 375 References 381 27. Phytoplankton: cOlDposition, developlDent and p- ductivity by]. F. TaIling. 385 Introduction. . . . . 385 Regional Development 385 The headwater lakes 385 a. Lake Victoria . 385 b. Lake Kioga . 387 c. Lake Albert. . 388 d. Lake Tana . . 390 The Sudan plain . 390 The Main Nile in Nubia and Egypt. 395 Limiting factors . . . . . . . . 396 Rates of photosynthetic production 397 References . . . . . 400 VI. Epilogue by ]. Rzoska 403 Authors Index . 407 Subject Index . . . . 413 The Nile in the Desert. The view encompasses more than 2000 kilometers from the river junction in the lower part of the picture to just below the Qena-Luxor bend, at the left upper end. The photograph was taken before the Aswan High Dam basin began to rise. The Red Sea and Saudi Arabia and the Ethiopian Highlands form the background. For the present state of the Dam basin see fig. 72. Courtesy of NASA. INTRODUCTION This book is an attempt to bring together information on the biology of the Nile. A big library could be filled by books on this river devoted to exploration and discovery, human history and hydrology. None has so far been written on the biology of the whole river system.

357 Temperature . . . . . . . . . 358 Transparency and light penetration. 360 Salinity and conductivity 363 Major ions . . . . . 365 Dissolved gases and pH 371 Plant nutrients. 375 References 381 27. Phytoplankton: cOlDposition, developlDent and p- ductivity by]. F. TaIling. 385 Introduction. . . . . 385 Regional Development 385 The headwater lakes 385 a. Lake Victoria . 385 b. Lake Kioga . 387 c. Lake Albert. . 388 d. Lake Tana . . 390 The Sudan plain . 390 The Main Nile in Nubia and Egypt. 395 Limiting factors . . . . . . . . 396 Rates of photosynthetic production 397 References . . . . . 400 VI. Epilogue by ]. Rzoska 403 Authors Index . 407 Subject Index . . . . 413 The Nile in the Desert. The view encompasses more than 2000 kilometers from the river junction in the lower part of the picture to just below the Qena-Luxor bend, at the left upper end. The photograph was taken before the Aswan High Dam basin began to rise. The Red Sea and Saudi Arabia and the Ethiopian Highlands form the background. For the present state of the Dam basin see fig. 72. Courtesy of NASA. INTRODUCTION This book is an attempt to bring together information on the biology of the Nile. A big library could be filled by books on this river devoted to exploration and discovery, human history and hydrology. None has so far been written on the biology of the whole river system.